draft-ietf-mboned-mtrace-v2-00.txt   draft-ietf-mboned-mtrace-v2-01.txt 
MBONED Working Group H. Asaeda MBONED Working Group H. Asaeda
Internet-Draft Keio University Internet-Draft Keio University
Expires: May 15, 2008 T. Jinmei Intended status: Standards Track T. Jinmei
Toshiba Corporation Expires: January 5, 2009 ISC
W. Fenner W. Fenner
AT&T Research Arastra, Inc.
S. Casner S. Casner
Packet Design, Inc. Packet Design, Inc.
November 12, 2007 July 4, 2008
Mtrace Version 2: Traceroute Facility for IP Multicast Mtrace Version 2: Traceroute Facility for IP Multicast
draft-ietf-mboned-mtrace-v2-00 draft-ietf-mboned-mtrace-v2-01
Status of this Memo Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract Abstract
This document describes the IP multicast traceroute facility. Unlike This document describes the IP multicast traceroute facility. Unlike
unicast traceroute, multicast traceroute requires special unicast traceroute, multicast traceroute requires special
implementations on the part of routers. This specification describes implementations on the part of routers. This specification describes
the required functionality in multicast routers, as well as how the required functionality in multicast routers, as well as how
management applications can use the new router functionality. management applications can use the router functionality.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. IPv4 Multicast Traceroute Header . . . . . . . . . . . . . . . 8 4. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Type: 8 bits . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Mtrace2 TLV format . . . . . . . . . . . . . . . . . . . . 8
4.2. # hops: 8 bits . . . . . . . . . . . . . . . . . . . . . . 8 4.2. Defined TLVs . . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Checksum: 16 bits . . . . . . . . . . . . . . . . . . . . 9 5. Mtrace2 Header . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4. Multicast Address . . . . . . . . . . . . . . . . . . . . 9 5.1. # hops: 8 bits . . . . . . . . . . . . . . . . . . . . . . 9
4.5. Source Address . . . . . . . . . . . . . . . . . . . . . . 9 5.2. Multicast Address . . . . . . . . . . . . . . . . . . . . 10
4.6. Destination Address . . . . . . . . . . . . . . . . . . . 9 5.3. Source Address . . . . . . . . . . . . . . . . . . . . . . 10
4.7. Response Address . . . . . . . . . . . . . . . . . . . . . 9 5.4. Destination Address . . . . . . . . . . . . . . . . . . . 10
4.8. Resp TTL: 8 bits . . . . . . . . . . . . . . . . . . . . . 9 5.5. Response Address . . . . . . . . . . . . . . . . . . . . . 10
4.9. Query ID: 24 bits . . . . . . . . . . . . . . . . . . . . 9 5.6. Resp TTL/HopLim: 8 bits . . . . . . . . . . . . . . . . . 10
5. IPv4 Multicast Traceroute Response Data . . . . . . . . . . . 10 5.7. Query ID: 24 bits . . . . . . . . . . . . . . . . . . . . 10
5.1. Query Arrival Time: 32 bits . . . . . . . . . . . . . . . 10 6. IPv4 Mtrace2 Response Data . . . . . . . . . . . . . . . . . . 11
5.2. Incoming Interface Address . . . . . . . . . . . . . . . . 11 6.1. Query Arrival Time: 32 bits . . . . . . . . . . . . . . . 11
5.3. Outgoing Interface Address . . . . . . . . . . . . . . . . 11 6.2. Incoming Interface Address: 32 bits . . . . . . . . . . . 12
5.4. Previous-Hop Router Address . . . . . . . . . . . . . . . 11 6.3. Outgoing Interface Address: 32 bits . . . . . . . . . . . 12
5.5. Packet counts . . . . . . . . . . . . . . . . . . . . . . 11 6.4. Previous-Hop Router Address: 32 bits . . . . . . . . . . . 12
5.6. Input packet count on incoming interface . . . . . . . . . 11 6.5. Input packet count on incoming interface: 64 bits . . . . 12
5.7. Output packet count on incoming interface . . . . . . . . 11 6.6. Output packet count on incoming interface: 64 bits . . . . 12
5.8. Total number of packets for this source-group pair . . . . 11 6.7. Total number of packets for this source-group pair: 64
5.9. Rtg Protocol: 8 bits . . . . . . . . . . . . . . . . . . . 12 bits . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.10. Fwd TTL: 8 bits . . . . . . . . . . . . . . . . . . . . . 12 6.8. Rtg Protocol: 8 bits . . . . . . . . . . . . . . . . . . . 13
5.11. MBZ: 1 bit . . . . . . . . . . . . . . . . . . . . . . . . 12 6.9. Fwd TTL: 8 bits . . . . . . . . . . . . . . . . . . . . . 13
5.12. S: 1 bit . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.10. MBZ: 1 bit . . . . . . . . . . . . . . . . . . . . . . . . 13
5.13. Src Mask: 6 bits . . . . . . . . . . . . . . . . . . . . . 12 6.11. S: 1 bit . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.14. Forwarding Code: 8 bits . . . . . . . . . . . . . . . . . 13 6.12. Src Mask: 6 bits . . . . . . . . . . . . . . . . . . . . . 13
6. IPv6 Multicast Traceroute Header . . . . . . . . . . . . . . . 15 6.13. Forwarding Code: 8 bits . . . . . . . . . . . . . . . . . 13
6.1. Type: 8 bits . . . . . . . . . . . . . . . . . . . . . . . 16 7. IPv6 Mtrace2 Response Data . . . . . . . . . . . . . . . . . . 16
6.2. # hops: 8 bits . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Query Arrival Time: 32 bits . . . . . . . . . . . . . . . 16
6.3. Checksum: 16 bits . . . . . . . . . . . . . . . . . . . . 16 7.2. Incoming Interface ID: 32 bits . . . . . . . . . . . . . . 16
6.4. Reserved: 32 bits . . . . . . . . . . . . . . . . . . . . 16 7.3. Outgoing Interface ID: 32 bits . . . . . . . . . . . . . . 17
6.5. Multicast Address . . . . . . . . . . . . . . . . . . . . 16 7.4. Local Address . . . . . . . . . . . . . . . . . . . . . . 17
6.6. Source Address . . . . . . . . . . . . . . . . . . . . . . 16 7.5. Remote Address . . . . . . . . . . . . . . . . . . . . . . 17
6.7. Destination Address . . . . . . . . . . . . . . . . . . . 16 7.6. Input packet count on incoming interface . . . . . . . . . 17
6.8. Response Address . . . . . . . . . . . . . . . . . . . . . 16 7.7. Output packet count on incoming interface . . . . . . . . 17
6.9. Resp Hop Limit: 8 bits . . . . . . . . . . . . . . . . . . 17 7.8. Total number of packets for this source-group pair . . . . 18
6.10. Query ID: 24 bits . . . . . . . . . . . . . . . . . . . . 17 7.9. Rtg Protocol: 8 bits . . . . . . . . . . . . . . . . . . . 18
7. IPv6 Multicast Traceroute Response Data . . . . . . . . . . . 18 7.10. MBZ: 7 bits . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. Query Arrival Time: 32 bits . . . . . . . . . . . . . . . 19 7.11. S: 1 bit . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.2. Incoming Interface ID: 32 bits . . . . . . . . . . . . . . 19 7.12. Src Prefix Len: 8 bits . . . . . . . . . . . . . . . . . . 18
7.3. Outgoing Interface ID: 32 bits . . . . . . . . . . . . . . 19 7.13. Forwarding Code: 8 bits . . . . . . . . . . . . . . . . . 18
7.4. Local Address . . . . . . . . . . . . . . . . . . . . . . 19 8. Router Behavior . . . . . . . . . . . . . . . . . . . . . . . 19
7.5. Remote Address . . . . . . . . . . . . . . . . . . . . . . 19 8.1. Traceroute Query . . . . . . . . . . . . . . . . . . . . . 19
7.6. Input packet count on incoming interface . . . . . . . . . 20 8.1.1. Packet Verification . . . . . . . . . . . . . . . . . 19
7.7. Output packet count on incoming interface . . . . . . . . 20 8.1.2. Normal Processing . . . . . . . . . . . . . . . . . . 19
7.8. Total number of packets for this source-group pair . . . . 20 8.2. Mtrace2 Request . . . . . . . . . . . . . . . . . . . . . 19
7.9. Rtg Protocol: 8 bits . . . . . . . . . . . . . . . . . . . 20 8.2.1. Packet Verification . . . . . . . . . . . . . . . . . 20
7.10. Fwd Hop Limit: 8 bits . . . . . . . . . . . . . . . . . . 20 8.2.2. Normal Processing . . . . . . . . . . . . . . . . . . 20
7.11. MBZ: 7 bits . . . . . . . . . . . . . . . . . . . . . . . 20 8.3. Mtrace2 Response . . . . . . . . . . . . . . . . . . . . . 21
7.12. S: 1 bit . . . . . . . . . . . . . . . . . . . . . . . . . 20 8.4. Forwarding Mtrace2 Requests . . . . . . . . . . . . . . . 21
7.13. Src Prefix Len: 8 bits . . . . . . . . . . . . . . . . . . 20 8.5. Sending Mtrace2 Responses . . . . . . . . . . . . . . . . 22
7.14. Forwarding Code: 8 bits . . . . . . . . . . . . . . . . . 21 8.5.1. Destination Address . . . . . . . . . . . . . . . . . 22
7.15. Reserved: 24 bit . . . . . . . . . . . . . . . . . . . . . 21 8.5.2. TTL and Hop Limit . . . . . . . . . . . . . . . . . . 22
8. Router Behavior . . . . . . . . . . . . . . . . . . . . . . . 22 8.5.3. Source Address . . . . . . . . . . . . . . . . . . . . 22
8.1. Traceroute Query . . . . . . . . . . . . . . . . . . . . . 22 8.5.4. Sourcing Multicast Responses . . . . . . . . . . . . . 22
8.1.1. Packet Verification . . . . . . . . . . . . . . . . . 22 8.6. Hiding Information . . . . . . . . . . . . . . . . . . . . 22
8.1.2. Normal Processing . . . . . . . . . . . . . . . . . . 22 9. Client Behavior . . . . . . . . . . . . . . . . . . . . . . . 23
8.2. Traceroute Request . . . . . . . . . . . . . . . . . . . . 22 9.1. Sending Mtrace2 Query . . . . . . . . . . . . . . . . . . 23
8.2.1. Packet Verification . . . . . . . . . . . . . . . . . 23 9.2. Determining the Path . . . . . . . . . . . . . . . . . . . 23
8.2.2. Normal Processing . . . . . . . . . . . . . . . . . . 23 9.3. Collecting Statistics . . . . . . . . . . . . . . . . . . 23
8.3. Traceroute Response . . . . . . . . . . . . . . . . . . . 24 9.4. Last Hop Router . . . . . . . . . . . . . . . . . . . . . 23
8.4. Forwarding Traceroute Requests . . . . . . . . . . . . . . 24 9.5. First Hop Router . . . . . . . . . . . . . . . . . . . . . 24
8.5. Sending Traceroute Responses . . . . . . . . . . . . . . . 25 9.6. Broken Intermediate Router . . . . . . . . . . . . . . . . 24
8.5.1. Destination Address . . . . . . . . . . . . . . . . . 25 9.7. Mtrace2 Termination . . . . . . . . . . . . . . . . . . . 24
8.5.2. TTL and Hop Limit . . . . . . . . . . . . . . . . . . 25 9.7.1. Arriving at source . . . . . . . . . . . . . . . . . . 24
8.5.3. Source Address . . . . . . . . . . . . . . . . . . . . 25 9.7.2. Fatal error . . . . . . . . . . . . . . . . . . . . . 25
8.5.4. Sourcing multicast responses . . . . . . . . . . . . . 25 9.7.3. No previous hop . . . . . . . . . . . . . . . . . . . 25
8.6. Hiding information . . . . . . . . . . . . . . . . . . . . 26 9.7.4. Traceroute shorter than requested . . . . . . . . . . 25
9. Using multicast traceroute . . . . . . . . . . . . . . . . . . 27 9.8. Continuing after an error . . . . . . . . . . . . . . . . 25
9.1. Sample client . . . . . . . . . . . . . . . . . . . . . . 27 10. Protocol-Specific Considerations . . . . . . . . . . . . . . . 26
9.1.1. Sending initial query . . . . . . . . . . . . . . . . 27 10.1. PIM-SM . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9.1.2. Determining the Path . . . . . . . . . . . . . . . . . 27 10.2. Bi-Directional PIM . . . . . . . . . . . . . . . . . . . . 26
9.1.3. Collecting statistics . . . . . . . . . . . . . . . . 27 10.3. PIM-DM . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9.2. Last hop router . . . . . . . . . . . . . . . . . . . . . 28 10.4. IGMP/MLD Proxy . . . . . . . . . . . . . . . . . . . . . . 26
9.3. First hop router . . . . . . . . . . . . . . . . . . . . . 28 10.5. AMT . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.4. Broken intermediate router . . . . . . . . . . . . . . . . 28 11. Problem Diagnosis . . . . . . . . . . . . . . . . . . . . . . 28
9.5. Mtrace2 termination . . . . . . . . . . . . . . . . . . . 29 11.1. Forwarding Inconsistencies . . . . . . . . . . . . . . . . 28
9.5.1. Arriving at source . . . . . . . . . . . . . . . . . . 29 11.2. TTL or Hop Limit Problems . . . . . . . . . . . . . . . . 28
9.5.2. Fatal error . . . . . . . . . . . . . . . . . . . . . 29 11.3. Packet loss . . . . . . . . . . . . . . . . . . . . . . . 28
9.5.3. No previous hop . . . . . . . . . . . . . . . . . . . 29 11.4. Link Utilization . . . . . . . . . . . . . . . . . . . . . 29
9.5.4. Traceroute shorter than requested . . . . . . . . . . 29 11.5. Time Delay . . . . . . . . . . . . . . . . . . . . . . . . 29
9.6. Continuing after an error . . . . . . . . . . . . . . . . 29 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
9.7. Multicast Traceroute and shared tree routing protocols . . 30 12.1. Forwarding Codes . . . . . . . . . . . . . . . . . . . . . 30
9.7.1. PIM-SM . . . . . . . . . . . . . . . . . . . . . . . . 30 12.2. UDP Destination Port and IPv6 Address . . . . . . . . . . 30
9.7.2. Bi-directional PIM . . . . . . . . . . . . . . . . . . 30 13. Security Considerations . . . . . . . . . . . . . . . . . . . 31
9.7.3. CBT . . . . . . . . . . . . . . . . . . . . . . . . . 30 13.1. Topology Discovery . . . . . . . . . . . . . . . . . . . . 31
9.8. Protocol-specific considerations . . . . . . . . . . . . . 31 13.2. Traffic Rates . . . . . . . . . . . . . . . . . . . . . . 31
9.8.1. DVMRP . . . . . . . . . . . . . . . . . . . . . . . . 31 13.3. Unicast Replies . . . . . . . . . . . . . . . . . . . . . 31
9.8.2. PIM-DM . . . . . . . . . . . . . . . . . . . . . . . . 31 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32
10. Problem Diagnosis . . . . . . . . . . . . . . . . . . . . . . 32 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.1. Forwarding Inconsistencies . . . . . . . . . . . . . . . . 32 15.1. Normative References . . . . . . . . . . . . . . . . . . . 33
10.2. TTL or hop limit problems . . . . . . . . . . . . . . . . 32 15.2. Informative References . . . . . . . . . . . . . . . . . . 33
10.3. Packet loss . . . . . . . . . . . . . . . . . . . . . . . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35
10.4. Link Utilization . . . . . . . . . . . . . . . . . . . . . 33 Intellectual Property and Copyright Statements . . . . . . . . . . 36
10.5. Time delay . . . . . . . . . . . . . . . . . . . . . . . . 33
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
11.1. Routing protocols . . . . . . . . . . . . . . . . . . . . 34
11.2. Forwarding codes . . . . . . . . . . . . . . . . . . . . . 34
11.3. UDP destination port and IPv6 address . . . . . . . . . . 34
12. Security Considerations . . . . . . . . . . . . . . . . . . . 35
12.1. Topology Discovery . . . . . . . . . . . . . . . . . . . . 35
12.2. Traffic Rates . . . . . . . . . . . . . . . . . . . . . . 35
12.3. Unicast Replies . . . . . . . . . . . . . . . . . . . . . 35
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 36
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37
14.1. Normative References . . . . . . . . . . . . . . . . . . . 37
14.2. Informative References . . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 38
Intellectual Property and Copyright Statements . . . . . . . . . . 39
1. Introduction 1. Introduction
The unicast "traceroute" program allows the tracing of a path from The unicast "traceroute" program allows the tracing of a path from
one machine to another. The key mechanism for unicast traceroute is one machine to another. The key mechanism for unicast traceroute is
the ICMP TTL exceeded message, which is specifically precluded as a the ICMP TTL exceeded message, which is specifically precluded as a
response to multicast packets. On the other hand, the multicast response to multicast packets. On the other hand, the multicast
traceroute facility allows the tracing of an IP multicast routing traceroute facility allows the tracing of an IP multicast routing
paths. In this document, we specify the new multicast "traceroute" paths. In this document, we specify the multicast "traceroute"
facility to be implemented in multicast routers and accessed by facility to be implemented in multicast routers and accessed by
diagnostic programs. The new multicast traceroute, mtrace version 2 diagnostic programs. The multicast traceroute described in this
or mtrace2, can provide additional information about packet rates and document named as mtrace version 2 or mtrace2 provides additional
losses that the unicast traceroute cannot, and generally requires information about packet rates and losses that the unicast traceroute
fewer packets to be sent. cannot, and generally requires fewer packets to be sent.
o. To be able to trace the path that a packet would take from some o. To be able to trace the path that a packet would take from some
source to some destination. source to some destination.
o. To be able to isolate packet loss problems (e.g., congestion). o. To be able to isolate packet loss problems (e.g., congestion).
o. To be able to isolate configuration problems (e.g., TTL o. To be able to isolate configuration problems (e.g., TTL
threshold). threshold).
o. To minimize packets sent (e.g. no flooding, no implosion). o. To minimize packets sent (e.g. no flooding, no implosion).
This document supports both IPv4 and IPv6 multicast traceroute This document supports both IPv4 and IPv6 multicast traceroute
facility. The protocol design, concept, and program behavior are facility. The protocol design, concept, and program behavior are
same between IPv4 and IPv6 mtrace2. Regarding the previous IPv4 same between IPv4 and IPv6 mtrace2. While the original IPv4
multicast traceroute, mtrace, the query and response messages for multicast traceroute, mtrace, the query and response messages are
IPv4 mtrace are implemented as IGMP messages [4]. On the other hand, implemented as IGMP messages [4], all mtrace2 messages are carried on
mtrace2 messages are carried on UDP, whereas the packet formats of UDP. The packet formats of IPv4 and IPv6 mtrace2 are different
IPv4 and IPv6 mtrace2 are different (but similar) because of the because of the different address families, but the syntax is similar.
different address family.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT","SHOULD", "SHOULD NOT", "RECOMMENDED","MAY", and "OPTIONAL" in NOT","SHOULD", "SHOULD NOT", "RECOMMENDED","MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119 [1]. this document are to be interpreted as described in RFC 2119 [1].
Since multicast traceroutes flow in the opposite direction to the Since multicast traceroutes flow in the opposite direction to the
data flow, we refer to "upstream" and "downstream" with respect to data flow, we refer to "upstream" and "downstream" with respect to
data, unless explicitly specified. data, unless explicitly specified.
skipping to change at page 6, line 30 skipping to change at page 6, line 30
The interface on which traffic is forwarded from the specified source The interface on which traffic is forwarded from the specified source
and group toward the destination. It is the interface on which the and group toward the destination. It is the interface on which the
multicast traceroute Request was received. multicast traceroute Request was received.
Previous-hop router: Previous-hop router:
The router that is on the link attached to the Incoming Interface and The router that is on the link attached to the Incoming Interface and
is responsible for forwarding traffic for the specified source and is responsible for forwarding traffic for the specified source and
group. group.
Group state: Group state:
It is the state in which a shared-tree protocol (e.g., PIM-SM [11]) It is the state in which a shared-tree protocol (e.g., PIM-SM [12])
running on a router chooses the previous-hop router toward the core running on a router chooses the previous-hop router toward the core
router (or RP) as its parent router. In this state, source-specific router or Rendezvous Point (RP) as its parent router. In this state,
state is not available for the corresponding multicast address on the source-specific state is not available for the corresponding
router. multicast address on the router.
Source-specific state: Source-specific state:
It is the state in which a routing protocol running on a router It is the state in which a routing protocol running on a router
chooses the path that would be followed for a source-specific join. chooses the path that would be followed for a source-specific join.
ALL-[protocol]-ROUTERS.MCAST.NET:
It is a dedicated multicast address for a multicast router to
communicate with other routers that are working with the same routing
protocol. For instance,the address of ALL-PIM-ROUTERS.MCAST.NET is
'224.0.0.13' for IPv4 and 'ff02::d' for IPv6.
3. Overview 3. Overview
Given a multicast distribution tree, tracing from a source to a Given a multicast distribution tree, tracing from a source to a
multicast destination is hard, since you don't know down which branch multicast destination is hard, since you don't know down which branch
of the multicast tree the destination lies. This means that you have of the multicast tree the destination lies. This means that you have
to flood the whole tree to find the path from one source to one to flood the whole tree to find the path from one source to one
destination. However, walking up the tree from destination to source destination. However, walking up the tree from destination to source
is easy, as most existing multicast routing protocols know the is easy, as most existing multicast routing protocols know the
previous hop for each source. Tracing from destination to source can previous hop for each source. Tracing from destination to source can
involve only routers on the direct path. involve only routers on the direct path.
skipping to change at page 7, line 36 skipping to change at page 7, line 36
one of its directly connected networks) changes the packet type to one of its directly connected networks) changes the packet type to
indicate a Response packet and sends the completed response to the indicate a Response packet and sends the completed response to the
response destination address. The response may be returned before response destination address. The response may be returned before
reaching the first hop router if a fatal error condition such as "no reaching the first hop router if a fatal error condition such as "no
route" is encountered along the path. route" is encountered along the path.
Multicast traceroute uses any information available to it in the Multicast traceroute uses any information available to it in the
router to attempt to determine a previous hop to forward the trace router to attempt to determine a previous hop to forward the trace
towards. Multicast routing protocols vary in the type and amount of towards. Multicast routing protocols vary in the type and amount of
state they keep; multicast traceroute endeavors to work with all of state they keep; multicast traceroute endeavors to work with all of
them by using whatever is available. For example, if a DVMRP router them by using whatever is available. For example, if a PIM-SM router
has no active state for a particular source but does have a DVMRP is on the (*,G) tree, it chooses the parent towards the RP as the
route, it chooses the parent of the DVMRP route as the previous hop. previous hop. In these cases, no source/group-specific state is
If a PIM-SM router is on the (*,G) tree, it chooses the parent available, but the path may still be traced.
towards the RP as the previous hop. In these cases, no source/
group-specific state is available, but the path may still be traced.
4. IPv4 Multicast Traceroute Header 4. Packet Formats
Mtrace2 message is encoded in TLV format. If an implementation
receives a TLV whose length exceeds the TLV length specified in the
Length field, the TLV SHOULD be accepted but any additional data
SHOULD be ignored.
4.1. Mtrace2 TLV format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Value .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (8 bits)
Length (16 bits)
Value (variable length)
4.2. Defined TLVs
The following TLV Types are defined:
Code Type
====== ============================
1 Mtrace2 Query
2 Mtrace2 Response
The type field is defined to be "0x1" for traceroute queries and
requests. The type field is changed to "0x2" when the packet is
completed and sent as a response from the first hop router to the
querier. Two codes are required so that multicast routers won't
attempt to process a completed response in those cases where the
initial query was issued from a router or the response is sent via
multicast.
5. Mtrace2 Header
The mtrace2 message is carried as a UDP packet. The UDP source port The mtrace2 message is carried as a UDP packet. The UDP source port
is uniquely selected by the local host operating system. The UDP is uniquely selected by the local host operating system. The UDP
destination port is the IANA reserved mtrace2 port number (see destination port is the IANA reserved mtrace2 port number (see
Section 11). The UDP checksum MUST be valid in mtrace2 control Section 12). The UDP checksum MUST be valid in mtrace2 control
messages. messages.
The IPv4 mtrace2 includes the common packet header as follows. The The mtrace2 includes the common packet header as follows. The header
header is only filled in by the originator of the traceroute Query; is only filled in by the originator of the traceroute Query;
intermediate routers MUST NOT modify any of the fields. intermediate routers MUST NOT modify any of the fields.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| # hops |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Reserved | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Multicast Address | | Multicast Address |
| |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| |
| Source Address | | Source Address |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination Address | | Destination Address |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Response Address | | Response Address |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Resp TTL/HopLim| Query ID | |Resp TTL/HopLim| Query ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1. Type: 8 bits Figure 1
The UDP type field is defined to be "0x1" for traceroute queries and
requests. The UDP type field is changed to "0x2" when the packet is
completed and sent as a response from the first hop router to the
querier. Two codes are required so that multicast routers won't
attempt to process a completed response in those cases where the
initial query was issued from a router or the response is sent via
multicast.
4.2. # hops: 8 bits 5.1. # hops: 8 bits
This field specifies the maximum number of hops that the requester This field specifies the maximum number of hops that the requester
wants to trace. If there is some error condition in the middle of wants to trace. If there is some error condition in the middle of
the path that keeps the traceroute request from reaching the first- the path that keeps the traceroute request from reaching the first-
hop router, this field can be used to perform an expanding-ring hop router, this field can be used to perform an expanding-ring
search to trace the path to just before the problem. search to trace the path to just before the problem.
4.3. Checksum: 16 bits 5.2. Multicast Address
The checksum is the 16-bit one's complement of the one's complement
sum of the whole UDP message (the entire IP payload) [7]. When
computing the checksum, the checksum field is set to zero. When
transmitting packets, the checksum MUST be computed and inserted into
this field. When receiving packets, the checksum MUST be verified
before processing a packet.
4.4. Multicast Address
This field specifies the multicast address to be traced, or zero if This field specifies the 32 bits length IPv4 or 128 bits length IPv6
no group-specific information is desired. Note that non-group- multicast address to be traced, or is filled with "all 1" in case of
specific traceroutes may not be possible with certain multicast IPv4 or with the unspecified address (::) in case of IPv6 if no
routing protocols. source-specific information is desired. Note that non-group-specific
traceroutes may not be possible with certain multicast routing
protocols.
4.5. Source Address 5.3. Source Address
This field specifies the IP address of the multicast source for the This field specifies the 32 bits length IPv4 or 128 bits length IPv6
path being traced, or 0xffffffff if no source-specific information is address of the multicast source for the path being traced, or is
desired. Note that non-source-specific traceroutes may not be filled with "all 1" in case of IPv4 or with the unspecified address
possible with certain multicast routing protocols. (::) in case of IPv6 if no source-specific information is desired.
Note that non-source-specific traceroutes may not be possible with
certain multicast routing protocols.
4.6. Destination Address 5.4. Destination Address
This field specifies the IP address of the multicast receiver for the This field specifies the 32 bits length IPv4 or 128 bits length IPv6
path being traced. The trace starts at this destination and proceeds address of the multicast receiver for the path being traced. The
toward the traffic source. trace starts at this destination and proceeds toward the traffic
source.
4.7. Response Address 5.5. Response Address
This field specifies IP address to which the completed traceroute This field specifies 32 bits length IPv4 or 128 bits length IPv6
response packet gets sent. It can be a unicast address or a address to which the completed traceroute response packet gets sent.
multicast address, as explained in Section 8.2 It can be a unicast address or a multicast address, as explained in
Section 8.2
4.8. Resp TTL: 8 bits 5.6. Resp TTL/HopLim: 8 bits
This field specifies the TTL at which to multicast the response, if This field specifies the TTL or Hop Limit at which to multicast the
the response address is a multicast address. response, if the response address is a multicast address.
4.9. Query ID: 24 bits 5.7. Query ID: 24 bits
This field is used as a unique identifier for this traceroute request This field is used as a unique identifier for this traceroute request
so that duplicate or delayed responses may be detected and to so that duplicate or delayed responses may be detected and to
minimize collisions when a multicast response address is used. minimize collisions when a multicast response address is used.
5. IPv4 Multicast Traceroute Response Data 6. IPv4 Mtrace2 Response Data
Each intermediate router in a trace path appends "response data" to Each intermediate IPv4 router in a trace path appends "response data"
the forwarded trace packet. The response data looks as follows. to the forwarded trace packet. The response data looks as follows.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Query Arrival Time | | Query Arrival Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Incoming Interface Address | | Incoming Interface Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outgoing Interface Address | | Outgoing Interface Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Previous-Hop Router Address | | Previous-Hop Router Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Input packet count on incoming interface | . Input packet count on incoming interface .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Output packet count on outgoing interface | . Output packet count on outgoing interface .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Total number of packets for this source-group pair | . Total number of packets for this source-group pair .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |M| | | | | | |M| | | |
| Rtg Protocol | Fwd TTL |B|S| Src Mask |Forwarding Code| | Rtg Protocol | Fwd TTL |B|S| Src Mask |Forwarding Code|
| | |Z| | | | | | |Z| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.1. Query Arrival Time: 32 bits 6.1. Query Arrival Time: 32 bits
The Query Arrival Time is a 32-bit NTP timestamp specifying the The Query Arrival Time is a 32-bit NTP timestamp specifying the
arrival time of the traceroute request packet at this router. The arrival time of the traceroute request packet at this router. The
32-bit form of an NTP timestamp consists of the middle 32 bits of the 32-bit form of an NTP timestamp consists of the middle 32 bits of the
full 64-bit form; that is, the low 16 bits of the integer part and full 64-bit form; that is, the low 16 bits of the integer part and
the high 16 bits of the fractional part. the high 16 bits of the fractional part.
The following formula converts from a UNIX timeval to a 32-bit NTP The following formula converts from a UNIX timeval to a 32-bit NTP
timestamp: timestamp:
query_arrival_time query_arrival_time
= (tv.tv_sec + 32384) << 16 + ((tv.tv_usec << 10) / 15625) = (tv.tv_sec + 32384) << 16 + ((tv.tv_usec << 10) / 15625)
The constant 32384 is the number of seconds from Jan 1, 1900 to Jan The constant 32384 is the number of seconds from Jan 1, 1900 to Jan
1, 1970 truncated to 16 bits. ((tv.tv_usec << 10) / 15625) is a 1, 1970 truncated to 16 bits. ((tv.tv_usec << 10) / 15625) is a
reduction of ((tv.tv_usec / 100000000) << 16). reduction of ((tv.tv_usec / 100000000) << 16).
5.2. Incoming Interface Address 6.2. Incoming Interface Address: 32 bits
This field specifies the address of the interface on which packets This field specifies the address of the interface on which packets
from this source and group are expected to arrive, or 0 if unknown. from this source and group are expected to arrive, or 0 if unknown.
5.3. Outgoing Interface Address 6.3. Outgoing Interface Address: 32 bits
This field specifies the address of the interface on which packets This field specifies the address of the interface on which packets
from this source and group flow to the specified destination, or 0 if from this source and group flow to the specified destination, or 0 if
unknown. unknown.
5.4. Previous-Hop Router Address 6.4. Previous-Hop Router Address: 32 bits
This field specifies the router from which this router expects This field specifies the router from which this router expects
packets from this source. This may be a multicast group (e.g. ALL- packets from this source. This may be a multicast group (e.g. ALL-
[protocol]-ROUTERS.MCAST.NET) if the previous hop is not known [protocol]-ROUTERS.MCAST.NET) if the previous hop is not known
because of the workings of the multicast routing protocol. However, because of the workings of the multicast routing protocol. However,
it should be 0 if the incoming interface address is unknown. it should be 0 if the incoming interface address is unknown.
5.5. Packet counts 6.5. Input packet count on incoming interface: 64 bits
Note that these packet counts SHOULD be as up to date as possible.
If packet counts are not being maintained on the processor that
handles the traceroute request in a multi-processor router
architecture, the packet SHOULD be delayed while the counters are
gathered from the remote processor(s). If this occurs, the Query
Arrival Time should be updated to reflect the time at which the
packet counts were learned.
5.6. Input packet count on incoming interface
This field contains the number of multicast packets received for all This field contains the number of multicast packets received for all
groups and sources on the incoming interface, or 0xffffffffffffffff groups and sources on the incoming interface, or "all 1" if no count
if no count can be reported. This counter should have the same value can be reported. This counter may have the same value as
as ifInMulticastPkts from the IF-MIB [9] for this interface. ifHCInMulticastPkts from the IF-MIB [10] for this interface.
5.7. Output packet count on incoming interface 6.6. Output packet count on incoming interface: 64 bits
This field contains the number of multicast packets that have been This field contains the number of multicast packets that have been
transmitted or queued for transmission for all groups and sources on transmitted or queued for transmission for all groups and sources on
the outgoing interface, or 0xffffffffffffffff if no count can be the outgoing interface, or "all 1" if no count can be reported. This
reported. This counter should have the same value as counter may have the same value as ifHCOutMulticastPkts from the IF-
ifOutMulticastPkts from the IF-MIB for this interface. MIB for this interface.
5.8. Total number of packets for this source-group pair 6.7. Total number of packets for this source-group pair: 64 bits
This field counts the number of packets from the specified source This field counts the number of packets from the specified source
forwarded by this router to the specified group, or forwarded by this router to the specified group, or "all 1" if no
0xffffffffffffffff if no count can be reported. If the S bit is set, count can be reported. If the S bit is set, the count is for the
the count is for the source network, as specified by the Src Mask source network, as specified by the Src Mask field. If the S bit is
field. If the S bit is set and the Src Mask field is 63, indicating set and the Src Mask field is 63, indicating no source-specific
no source-specific state, the count is for all sources sending to state, the count is for all sources sending to this group. This
this group. This counter should have the same value as counter should have the same value as ipMcastRoutePkts from the
ipMcastRoutePkts from the IPMROUTE-STD-MIB [10] for this forwarding IPMROUTE-STD-MIB [11] for this forwarding entry.
entry.
5.9. Rtg Protocol: 8 bits 6.8. Rtg Protocol: 8 bits
This field describes the routing protocol in use between this router This field describes the routing protocol in use between this router
and the previous-hop router. Specified values include: and the previous-hop router. Specified values include:
1 DVMRP 0 Unknown
2 MOSPF 1 PIM
3 PIM 2 PIM using special routing table
4 CBT 3 PIM using a static route
5 PIM using special routing table 4 PIM using MBGP route
6 PIM using a static route 5 PIM using state created by Assert processing
7 DVMRP using a static route 6 Bi-directional PIM
8 PIM using MBGP route 7 IGMP/MLD proxy
9 CBT using special routing table 8 AMT Relay
10 CBT using a static route 9 AMT Gateway
11 PIM using state created by Assert processing
12 Bi-directional PIM
Note that some of the routing protocols or functions are not
supported or not used in either of IPv4 multicast nor IPv6 multicast.
5.10. Fwd TTL: 8 bits 6.9. Fwd TTL: 8 bits
This field contains the TTL that a packet is required to have before This field contains the TTL that a packet is required to have before
it will be forwarded over the outgoing interface. it will be forwarded over the outgoing interface.
5.11. MBZ: 1 bit 6.10. MBZ: 1 bit
Must be zeroed on transmission and ignored on reception. Must be zeroed on transmission and ignored on reception.
5.12. S: 1 bit 6.11. S: 1 bit
This S bit indicates that the packet count for the source-group pair This S bit indicates that the packet count for the source-group pair
is for the source network, as determined by masking the source is for the source network, as determined by masking the source
address with the Src Mask field. address with the Src Mask field.
5.13. Src Mask: 6 bits 6.12. Src Mask: 6 bits
This field contains the number of 1's in the netmask this router has This field contains the number of 1's in the netmask this router has
for the source (i.e. a value of 24 means the netmask is 0xffffff00). for the source (i.e. a value of 24 means the netmask is 0xffffff00).
If the router is forwarding solely on group state, this field is set If the router is forwarding solely on group state, this field is set
to 63 (0x3f). to 63 (0x3f).
5.14. Forwarding Code: 8 bits 6.13. Forwarding Code: 8 bits
This field contains a forwarding information/error code. Defined This field contains a forwarding information/error code. Section 8.2
values are as follows; explains how and when the forwarding code is filled. Defined values
are as follows;
Value Name Description Value Name Description
----- -------------- ------------------------------------------- ----- -------------- -------------------------------------------
0x00 NO_ERROR No error 0x00 NO_ERROR No error
0x01 WRONG_IF Traceroute request arrived on an interface 0x01 WRONG_IF Mtrace2 request arrived on an interface
to which this router would not forward for to which this router would not forward for
this source,group,destination. this source,group,destination.
0x02 PRUNE_SENT This router has sent a prune upstream which 0x02 PRUNE_SENT This router has sent a prune upstream which
applies to the source and group in the applies to the source and group in the
traceroute request. traceroute request.
0x03 PRUNE_RCVD This router has stopped forwarding for this 0x03 PRUNE_RCVD This router has stopped forwarding for this
source and group in response to a request source and group in response to a request
from the next hop router. from the next hop router.
skipping to change at page 13, line 45 skipping to change at page 14, line 32
group and no way to determine a potential group and no way to determine a potential
route. route.
0x06 WRONG_LAST_HOP This router is not the proper last-hop 0x06 WRONG_LAST_HOP This router is not the proper last-hop
router. router.
0x07 NOT_FORWARDING This router is not forwarding this source, 0x07 NOT_FORWARDING This router is not forwarding this source,
group out the outgoing interface for an group out the outgoing interface for an
unspecified reason. unspecified reason.
0x08 REACHED_RP Reached Rendez-vous Point or Core 0x08 REACHED_RP Reached Rendezvous Point or Core
0x09 RPF_IF Traceroute request arrived on the expected 0x09 RPF_IF Mtrace2 request arrived on the expected
RPF interface for this source, group. RPF interface for this source and group.
0x0A NO_MULTICAST Traceroute request arrived on an interface 0x0A NO_MULTICAST Mtrace2 request arrived on an interface
which is not enabled for multicast. which is not enabled for multicast.
0x0B INFO_HIDDEN One or more hops have been hidden from this 0x0B INFO_HIDDEN One or more hops have been hidden from this
trace. trace.
0x81 NO_SPACE There was not enough room to insert another 0x81 NO_SPACE There was not enough room to insert another
response data block in the packet. response data block in the packet.
0x82 OLD_ROUTER The previous-hop router does not understand 0x82 OLD_ROUTER The previous-hop router does not understand
traceroute requests. traceroute requests.
0x83 ADMIN_PROHIB Traceroute is administratively prohibited. 0x83 ADMIN_PROHIB Mtrace2 is administratively prohibited.
Note that if a router discovers there is not enough room in a packet Note that if a router discovers there is not enough room in a packet
to insert its response, it puts the 0x81 error code in the previous to insert its response, it puts the 0x81 error code in the previous
router's Forwarding Code field, overwriting any error the previous router's Forwarding Code field, overwriting any error the previous
router placed there. A multicast traceroute client, upon receiving router placed there. A multicast traceroute client, upon receiving
this error, MAY restart the trace at the last hop listed in the this error, MAY restart the trace at the last hop listed in the
packet. packet.
The 0x80 bit of the Forwarding Code is used to indicate a fatal The 0x80 bit of the Forwarding Code is used to indicate a fatal
error. A fatal error is one where the router may know the previous error. A fatal error is one where the router may know the previous
hop but cannot forward the message to it. hop but cannot forward the message to it.
6. IPv6 Multicast Traceroute Header 7. IPv6 Mtrace2 Response Data
IPv6 mtrace2 includes the common packet header as follows. Because
of the specification of the IPv6 address, all IPv6 addresses used in
each field consume 128 bits length.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | # hops | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
* *
| |
* Multicast Address *
| |
* *
| |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| |
* *
| |
* Source Address *
| |
* *
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
* *
| |
* Destination Address *
| |
* *
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
* *
| |
* Response Address *
| |
* *
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Resp Hop Limit | Query ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.1. Type: 8 bits
The UDP type field is defined to be "0x1" for traceroute queries and
requests. The UDP type field is changed to "0x2" when the packet is
completed and sent as a response from the first hop router to the
querier. Two codes are required so that multicast routers won't
attempt to process a completed response in those cases where the
initial query was issued from a router or the response is sent via
multicast.
6.2. # hops: 8 bits
Same definition described in Section 4.2
6.3. Checksum: 16 bits
As defined in [2], the checksum is the 16-bit one's complement of the
one's complement sum of the entire UDP message, starting with the UDP
message type field, and prepended with a "pseudo-header" of IPv6
header fields.
6.4. Reserved: 32 bits
Initialized to zero by the sender; ignored by receivers.
6.5. Multicast Address
Same definition described in Section 4.4
6.6. Source Address
This field specifies the IPv6 address of the multicast source for the
path being traced, or is filled with the unspecified address (::) if
no source-specific information is desired. Note that non-source-
specific traceroutes may not be possible with certain multicast
routing protocols.
6.7. Destination Address
Same definition described in Section 4.6
6.8. Response Address
Same definition described in Section 4.7
6.9. Resp Hop Limit: 8 bits
This field specifies the hop limit at which to multicast the
response, if the response address is a multicast address.
6.10. Query ID: 24 bits
Same definition described in Section 4.9
7. IPv6 Multicast Traceroute Response Data
Each intermediate router in a trace path appends "response data" to Each intermediate IPv6 router in a trace path appends "response data"
the forwarded trace packet. The response data looks as follows. to the forwarded trace packet. The response data looks as follows.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Query Arrival Time | | Query Arrival Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Incoming Interface ID | | Incoming Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outgoing Interface ID | | Outgoing Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
* *
| |
* Local Address * * Local Address *
| | | |
* *
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
* *
| |
* Remote Address * * Remote Address *
| | | |
* *
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Input packet count on incoming interface | . Input packet count on incoming interface .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Output packet count on outgoing interface |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| Total number of packets for this source-group pair | . Output packet count on outgoing interface .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Rtg Protocol | Fwd Hop Limit | MBZ |S|Src Prefix Len | | |
. Total number of packets for this source-group pair .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Forwarding Code| Reserved | | Rtg Protocol | MBZ |S|Src Prefix Len |Forwarding Code|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7.1. Query Arrival Time: 32 bits 7.1. Query Arrival Time: 32 bits
Same definition described in Section 5.1 Same definition described in Section 6.1
7.2. Incoming Interface ID: 32 bits 7.2. Incoming Interface ID: 32 bits
This field specifies the interface ID on which packets from this This field specifies the interface ID on which packets from this
source and group are expected to arrive, or 0 if unknown. This ID source and group are expected to arrive, or 0 if unknown. This ID
should be the value taken from InterfaceIndex of the IF-MIB for this should be the value taken from InterfaceIndex of the IF-MIB [10] for
interface. This field is carried in network byte order. this interface. This field is carried in network byte order.
7.3. Outgoing Interface ID: 32 bits 7.3. Outgoing Interface ID: 32 bits
This field specifies the interface ID on which packets from this This field specifies the interface ID on which packets from this
source and group flow to the specified destination, or 0 if unknown. source and group flow to the specified destination, or 0 if unknown.
This ID should be the value taken from InterfaceIndex of the IF-MIB This ID should be the value taken from InterfaceIndex of the IF-MIB
for this interface. This field is carried in network byte order. for this interface. This field is carried in network byte order.
7.4. Local Address 7.4. Local Address
skipping to change at page 20, line 7 skipping to change at page 17, line 44
address (i.e., Local Address). address (i.e., Local Address).
This may be a multicast group (e.g., ALL-[protocol]- This may be a multicast group (e.g., ALL-[protocol]-
ROUTERS.MCAST.NET) if the previous hop is not known because of the ROUTERS.MCAST.NET) if the previous hop is not known because of the
workings of the multicast routing protocol. However, it should be workings of the multicast routing protocol. However, it should be
the unspecified address (::) if the incoming interface address is the unspecified address (::) if the incoming interface address is
unknown. unknown.
7.6. Input packet count on incoming interface 7.6. Input packet count on incoming interface
Same definition described in Section 5.6 Same definition described in Section 6.5
7.7. Output packet count on incoming interface 7.7. Output packet count on incoming interface
Same definition described in Section 5.7 Same definition described in Section 6.6
7.8. Total number of packets for this source-group pair 7.8. Total number of packets for this source-group pair
This field counts the number of packets from the specified source This field counts the number of packets from the specified source
forwarded by this router to the specified group, or forwarded by this router to the specified group, or "all 1" if no
0xffffffffffffffff if no count can be reported. If the S bit is set, count can be reported. If the S bit is set, the count is for the
the count is for the source network, as specified by the Src Prefix source network, as specified by the Src Prefix Len field. If the S
Len field. If the S bit is set and the Src Prefix Len field is 255, bit is set and the Src Prefix Len field is 255, indicating no source-
indicating no source-specific state, the count is for all sources specific state, the count is for all sources sending to this group.
sending to this group. This counter should have the same value as This counter should have the same value as ipMcastRoutePkts from the
ipMcastRoutePkts from the IPMROUTE-STD-MIB for this forwarding entry. IPMROUTE-STD-MIB for this forwarding entry.
7.9. Rtg Protocol: 8 bits 7.9. Rtg Protocol: 8 bits
Same definition described in Section 5.9 Same definition described in Section 6.8
Note that some of the routing protocols or functions are not
supported or not used in IPv6 multicast.
7.10. Fwd Hop Limit: 8 bits
This field contains the hop limit that a packet is required to have
before it will be forwarded over the outgoing interface.
7.11. MBZ: 7 bits 7.10. MBZ: 7 bits
Must be zeroed on transmission and ignored on reception. Must be zeroed on transmission and ignored on reception.
7.12. S: 1 bit 7.11. S: 1 bit
This S bit indicates that the packet count for the source-group pair This S bit indicates that the packet count for the source-group pair
is for the source network, as determined by masking the source is for the source network, as determined by masking the source
address with the Src Prefix Len field. address with the Src Prefix Len field.
7.13. Src Prefix Len: 8 bits 7.12. Src Prefix Len: 8 bits
This field contains the decimal number of the prefix length this
router has for the source. If the router is forwarding solely on
group state, this field is set to 255 (0xff)
7.14. Forwarding Code: 8 bits
Same definition described in Section 5.14 This field contains the prefix length this router has for the source.
If the router is forwarding solely on group state, this field is set
to 255 (0xff)
7.15. Reserved: 24 bit 7.13. Forwarding Code: 8 bits
Initialized to zero by the sender; ignored by receivers. Same definition described in Section 6.13
8. Router Behavior 8. Router Behavior
All of these actions are performed in addition to (NOT instead of) All of these actions are performed in addition to (NOT instead of)
forwarding the packet, if applicable. E.g. a multicast packet that forwarding the packet, if applicable. E.g. a multicast packet that
has TTL or the hop limit remaining MUST be forwarded normally, as has TTL or the hop limit remaining MUST be forwarded normally, as
MUST a unicast packet that has TTL or the hop limit remaining and is MUST a unicast packet that has TTL or the hop limit remaining and is
not addressed to this router. not addressed to this router.
8.1. Traceroute Query 8.1. Traceroute Query
A traceroute Query message is a traceroute message with no response An mtrace2 Query message is a traceroute message with no response
blocks filled in, and uses UDP type 0x1 for IPv4 and IPv6 mtrace2. blocks filled in, and uses TLV type 0x1 for IPv4 and IPv6 mtrace2.
8.1.1. Packet Verification 8.1.1. Packet Verification
Upon receiving a traceroute Query message, a router must examine the Upon receiving an mtrace2 Query message, a router must examine the
Query to see if it is the proper last-hop router for the destination Query to see if it is the proper last-hop router for the destination
address in the packet. It is the proper last-hop router if it has a address in the packet. It is the proper last-hop router if it has a
multicast-capable interface on the same subnet as the Destination multicast-capable interface on the same subnet as the Destination
Address and is the router that would forward traffic from the given Address and is the router that would forward traffic from the given
source onto that subnet. (S,G) onto that subnet.
If the router determines that it is not the proper last-hop router, If the router determines that it is not the proper last-hop router,
or it cannot make that determination, it does one of two things or it cannot make that determination, it does one of two things
depending if the Query was received via multicast or unicast. If the depending if the Query was received via multicast or unicast. If the
Query was received via multicast, then it MUST be silently dropped. Query was received via multicast, then it MUST be silently dropped.
If it was received via unicast, a forwarding code of WRONG_LAST_HOP If it was received via unicast, a forwarding code of WRONG_LAST_HOP
is noted and processing continues as in Section 8.2 is noted and processing continues as in Section 8.2
Duplicate Query messages as identified by the tuple (IP Source, Query Duplicate Query messages as identified by the tuple (IP Source, Query
ID) SHOULD be ignored. This MAY be implemented using a simple 1-back ID) SHOULD be ignored. This MAY be implemented using a simple 1-back
cache (i.e. remembering the IP source and Query ID of the previous cache (i.e. remembering the IP source and Query ID of the previous
Query message that was processed, and ignoring future messages with Query message that was processed, and ignoring future messages with
the same IP Source and Query ID). Duplicate Request messages MUST the same IP Source and Query ID). Duplicate Request messages MUST
NOT be ignored in this manner. NOT be ignored in this manner.
8.1.2. Normal Processing 8.1.2. Normal Processing
When a router receives a traceroute Query and it determines that it When a router receives an mtrace2 Query and it determines that it is
is the proper last-hop router, it treats it like a traceroute Request the proper last-hop router, it treats it like an mtrace2 Request and
and performs the steps listed in Section 8.2 performs the steps listed in Section 8.2
8.2. Traceroute Request 8.2. Mtrace2 Request
A traceroute Request is a traceroute message with some number of An mtrace2 Request is a traceroute message with some number of
response blocks filled in, and uses UDP type 0x1 for IPv4 and IPv6 response blocks filled in, and uses TLV type 0x1 for IPv4 and IPv6
mtrace2. Routers can tell the difference between Queries and mtrace2. Routers can tell the difference between Queries and
Requests by checking the length of the packet. Requests by checking the length of the packet.
8.2.1. Packet Verification 8.2.1. Packet Verification
If the traceroute Request is not addressed to this router, or if the If the mtrace2 Request is not addressed to this router, or if the
Request is addressed to a multicast group which is not a link-scoped Request is addressed to a multicast group which is not a link-scoped
group (i.e. 224/24 for IPv4, FFx2::/16 [3] for IPv6), it MUST be group (i.e. 224/24 for IPv4, FFx2::/16 [3] for IPv6), it MUST be
silently ignored. silently ignored.
8.2.2. Normal Processing 8.2.2. Normal Processing
When a router receives a traceroute Request, it performs the When a router receives an mtrace2 Request, it performs the following
following steps. Note that it is possible to have multiple steps. Note that it is possible to have multiple situations covered
situations covered by the Forwarding Codes. The first one by the Forwarding Codes. The first one encountered is the one that
encountered is the one that is reported, i.e. all "note forwarding is reported, i.e. all "note forwarding code N" should be interpreted
code N" should be interpreted as "if forwarding code is not already as "if forwarding code is not already set, set forwarding code to N".
set, set forwarding code to N".
1. If there is room in the current buffer (or the router can 1. If there is room in the current buffer (or the router can
efficiently allocate more space to use), insert a new response efficiently allocate more space to use), insert a new response
block into the packet and fill in the Query Arrival Time, block into the packet and fill in the Query Arrival Time,
Outgoing Interface Address (for IPv4 mtrace2) or Outgoing Outgoing Interface Address (for IPv4 mtrace2) or Outgoing
Interface ID (for IPv6 mtrace2), Output Packet Count, and Fwd Interface ID (for IPv6 mtrace2), Output Packet Count, and Fwd
TTL or Fwd Hop Limit. If there was no room, fill in the TTL (for IPv4 mtrace2). If there was no room, fill in the
response code "NO_SPACE" in the *previous* hop's response block, response code "NO_SPACE" in the *previous* hop's response block,
and forward the packet to the requester as described in and forward the packet to the requester as described in
"Forwarding Traceroute Requests". Section 8.4.
2. Attempt to determine the forwarding information for the source 2. Attempt to determine the forwarding information for the source
and group specified, using the same mechanisms as would be used and group specified, using the same mechanisms as would be used
when a packet is received from the source destined for the when a packet is received from the source destined for the
group. State need not be instantiated, it can be "phantom" group. State need not be instantiated, it can be "phantom"
state created only for the purpose of the trace. state created only for the purpose of the trace.
If using a shared-tree protocol and there is no source-specific If using a shared-tree protocol and there is no source-specific
state, or if the source is specified as 0xFFFFFFFF, group state state, or if the source is specified as "all 1", group state
should be used. If there is no group state or the group is should be used. If there is no group state or the group is
specified as 0, potential source state (i.e. the path that would specified as 0, potential source state (i.e. the path that would
be followed for a source-specific Join) should be used. If this be followed for a source-specific Join) should be used. If this
router is the Core or RP and no source-specific information is router is the Core or RP and no source-specific information is
available, note an error code of REACHED_RP. available, note an error code of REACHED_RP.
3. If no forwarding information can be determined, the router notes 3. If no forwarding information can be determined, the router notes
an error code of NO_ROUTE, sets the remaining fields that have an error code of NO_ROUTE, sets the remaining fields that have
not yet been filled in to zero, and then forwards the packet to not yet been filled in to zero, and then forwards the packet to
the requester as described in "Forwarding Traceroute Requests". the requester as described in Section 8.4.
4. Fill in the Incoming Interface Address, Previous-Hop Router 4. Fill in the Incoming Interface Address, Previous-Hop Router
Address, Input Packet Count, Total Number of Packets, Routing Address, Input Packet Count, Total Number of Packets, Routing
Protocol, S, and Src Mask from the forwarding information that Protocol, S, and Src Mask from the forwarding information that
was determined. was determined.
5. If traceroute is administratively prohibited or the previous hop 5. If traceroute is administratively prohibited or the previous hop
router does not understand traceroute requests, note the router does not understand traceroute requests, note the
appropriate forwarding code (ADMIN_PROHIB or OLD_ROUTER). If appropriate forwarding code (ADMIN_PROHIB or OLD_ROUTER). If
traceroute is administratively prohibited and any of the fields traceroute is administratively prohibited and any of the fields
as filled in step 4 are considered private information, zero out as filled in step 4 are considered private information, zero out
the applicable fields. Then the packet is forwarded to the the applicable fields. Then the packet is forwarded to the
requester as described in "Forwarding Traceroute Requests". requester as described in Section 8.4.
6. If the reception interface is not enabled for multicast, note 6. If the reception interface is not enabled for multicast, note
forwarding code NO_MULTICAST. If the reception interface is the forwarding code NO_MULTICAST. If the reception interface is the
interface from which the router would expect data to arrive from interface from which the router would expect data to arrive from
the source, note forwarding code RPF_IF. Otherwise, if the the source, note forwarding code RPF_IF. Otherwise, if the
reception interface is not one to which the router would forward reception interface is not one to which the router would forward
data from the source to the group, a forwarding code of WRONG_IF data from the source to the group, a forwarding code of WRONG_IF
is noted. is noted.
7. If the group is subject to administrative scoping on either the 7. If the group is subject to administrative scoping on either the
Outgoing or Incoming interfaces, a forwarding code of SCOPED is Outgoing or Incoming interfaces, a forwarding code of SCOPED is
noted. noted.
8. If this router is the Rendez-vous Point or Core for the group, a 8. If this router is the Rendezvous Point or Core for the group, a
forwarding code of REACHED_RP is noted. forwarding code of REACHED_RP is noted.
9. If this router has sent a prune upstream which applies to the 9. If this router has sent a prune upstream which applies to the
source and group in the traceroute Request, it notes forwarding source and group in the traceroute Request, it notes forwarding
code PRUNE_SENT. If the router has stopped forwarding code PRUNE_SENT. If the router has stopped forwarding
downstream in response to a prune sent by the next hop router, downstream in response to a prune sent by the next hop router,
it notes forwarding code PRUNE_RCVD. If the router should it notes forwarding code PRUNE_RCVD. If the router should
normally forward traffic for this source and group downstream normally forward traffic for this source and group downstream
but is not, it notes forwarding code NOT_FORWARDING. but is not, it notes forwarding code NOT_FORWARDING.
10. The packet is then sent on to the previous hop or the requester 10. The packet is then sent on to the previous hop or the requester
as described in Section 8.4. as described in Section 8.4.
8.3. Traceroute Response 8.3. Mtrace2 Response
A router must forward all traceroute response packets normally, with A router must forward all mtrace2 response packets normally, with no
no special processing. If a router has initiated a traceroute with a special processing. If a router has initiated an mtrace2 with a
Query or Request message, it may listen for Responses to that Query or Request message, it may listen for Responses to that
traceroute but MUST still forward them as well. traceroute but MUST still forward them as well.
8.4. Forwarding Traceroute Requests 8.4. Forwarding Mtrace2 Requests
If the Previous-hop router is known for this request and the number If the Previous-hop router is known for this request, the packet is
of response blocks is less than the number requested, the packet is
sent to that router. If the Incoming Interface is known but the sent to that router. If the Incoming Interface is known but the
Previous-hop router is not known, the packet is sent to an Previous-hop router is not known, the packet is sent to an
appropriate multicast address on the Incoming Interface. The appropriate multicast address on the Incoming Interface. The
appropriate multicast address may depend on the routing protocol in appropriate multicast address may depend on the routing protocol in
use, MUST be a link-scoped group (i.e. 224/24 for IPv4, FF02::/16 for use, MUST be a link-scoped group (i.e. 224/24 for IPv4, FF02::/16 for
IPv6), MUST NOT be ALL-SYSTEMS.MCAST.NET (224.0.0.1) for IPv4 and All IPv6), MUST NOT be ALL-SYSTEMS.MCAST.NET (224.0.0.1) for IPv4 and All
Nodes Address (FF02::1) for IPv6, and MAY be ALL-ROUTERS.MCAST.NET Nodes Address (FF02::1) for IPv6, and MAY be ALL-ROUTERS.MCAST.NET
(224.0.0.2) for IPv4 or All Routers Address (FF02::2) for IPv6 if the (224.0.0.2) for IPv4 or All Routers Address (FF02::2) for IPv6 if the
routing protocol in use does not define a more appropriate group. routing protocol in use does not define a more appropriate group.
Otherwise, it is sent to the Response Address in the header, as Otherwise, it is sent to the Response Address in the header, as
described in Section 8.5. described in Section 8.5.
Note that it is not an error for the number of response blocks to be 8.5. Sending Mtrace2 Responses
greater than the number requested; such a packet should simply be
forwarded to the requester as described in Section 8.5.
8.5. Sending Traceroute Responses
8.5.1. Destination Address 8.5.1. Destination Address
A traceroute response must be sent to the Response Address in the An mtrace2 response must be sent to the Response Address in the
traceroute header. traceroute header.
8.5.2. TTL and Hop Limit 8.5.2. TTL and Hop Limit
If the Response Address is unicast, the router inserts its normal If the Response Address is unicast, the router inserts its normal
unicast TTL or hop limit in the IP header, and may use any of its unicast TTL or hop limit in the IP header. If the Response Address
interface addresses as the source address. If the Response Address
is multicast, the router copies the Response TTL or hop limit from is multicast, the router copies the Response TTL or hop limit from
the traceroute header into the IP header. the traceroute header into the IP header.
8.5.3. Source Address 8.5.3. Source Address
If the Response Address is unicast, the router may use any of its If the Response Address is unicast, the router may use any of its
interface addresses as the source address. Since some multicast interface addresses as the source address. Since some multicast
routing protocols forward based on source address, if the Response routing protocols forward based on source address, if the Response
Address is multicast, the router MUST use an address that is known in Address is multicast, the router MUST use an address that is known in
the multicast routing topology if it can make that determination. the multicast routing topology if it can make that determination.
8.5.4. Sourcing multicast responses 8.5.4. Sourcing Multicast Responses
When a router sources a multicast response, the response packet MUST When a router sources a multicast response, the response packet MUST
be sent on a single interface, then forwarded as if it were received be sent on a single interface, then forwarded as if it were received
on that interface. It MUST NOT source the response packet on that interface. It MUST NOT source the response packet
individually on each interface, in order to avoid duplicate packets. individually on each interface, in order to avoid duplicate packets.
8.6. Hiding information 8.6. Hiding Information
Information about a domain's topology and connectivity may be hidden Information about a domain's topology and connectivity may be hidden
from multicast traceroute requests. The exact mechanism is not from multicast traceroute requests. The exact mechanism is not
specified here; however, the INFO_HIDDEN forwarding code may be used specified here; however, the INFO_HIDDEN forwarding code may be used
to note that, for example, the incoming interface address and packet to note that, for example, the incoming interface address and packet
count are for the entrance to the domain and the outgoing interface count are for the entrance to the domain and the outgoing interface
address and packet count are the exit from the domain. The source- address and packet count are the exit from the domain. The source-
group packet count may be from either router or not specified group packet count may be from either router or not specified (all
(0xffffffff). 1).
9. Using multicast traceroute
9.1. Sample client
This section describes the behavior of an example multicast 9. Client Behavior
traceroute client.
9.1.1. Sending initial query 9.1. Sending Mtrace2 Query
When the destination of the mtrace2 is the machine running the When the destination of the mtrace2 is the machine running the
client, the mtrace2 Query packet can be sent to the ALL- client, the mtrace2 Query packet can be sent to the ALL-
ROUTERS.MCAST.NET (224.0.0.2) for IPv4 or All Routers Address ROUTERS.MCAST.NET (224.0.0.2) for IPv4 or All Routers Address
(FF02::2) for IPv6. This will ensure that the packet is received by (FF02::2) for IPv6. This will ensure that the packet is received by
the last-hop router on the subnet. Otherwise, if the proper last-hop the last-hop router on the subnet. Otherwise, if the proper last-hop
router is known for the mtrace2 destination, the Query could be router is known for the mtrace2 destination, the Query could be
unicasted to that router. Otherwise, the Query packet should be unicasted to that router. Otherwise, the Query packet should be
multicasted to the group being queried; if the destination of the multicasted to the group being queried; if the destination of the
mtrace2 is a member of the group, this will get the Query to the mtrace2 is a member of the group, this will get the Query to the
proper last-hop router. In this final case, the packet should proper last-hop router. In this final case, the packet should
contain the Router Alert option [8], to make sure that routers that contain the Router Alert option [8][9], to make sure that routers
are not members of the multicast group notice the packet. that are not members of the multicast group notice the packet.
See also Section 9.2 on determining the last-hop router. See also Section 9.4 on determining the last-hop router.
9.1.2. Determining the Path 9.2. Determining the Path
The client could send a small number of initial query messages with a The client could send a small number of initial query messages with a
large "# hops" field, in order to try to trace the full path. If large "# hops" field, in order to try to trace the full path. If
this attempt fails, one strategy is to perform a linear search (as this attempt fails, one strategy is to perform a linear search (as
the traditional unicast traceroute program does); set the "# hops" the traditional unicast traceroute program does); set the "# hops"
field to 1 and try to get a response, then 2, and so on. If no field to 1 and try to get a response, then 2, and so on. If no
response is received at a certain hop, the hop count can continue response is received at a certain hop, the hop count can continue
past the non-responding hop, in the hopes that further hops may past the non-responding hop, in the hopes that further hops may
respond. These attempts should continue until a user-defined timeout respond. These attempts should continue until a user-defined timeout
has occurred. has occurred.
See also Section 9.3 and Section 9.4 on receiving the results of a See also Section 9.5 and Section 9.6 on receiving the results of a
trace. trace.
9.1.3. Collecting statistics 9.3. Collecting Statistics
After a client has determined that it has traced the whole path or as After a client has determined that it has traced the whole path or as
much as it can expect to (see Section 9.5), it might collect much as it can expect to (see Section 9.7), it might collect
statistics by waiting a short time and performing a second trace. If statistics by waiting a short time and performing a second trace. If
the path is the same in the two traces, statistics can be displayed the path is the same in the two traces, statistics can be displayed
as described in Section 10.3 and Section 10.4. as described in Section 11.3 and Section 11.4.
9.2. Last hop router 9.4. Last Hop Router
The mtrace2 querier may not know which is the last hop router, or The mtrace2 querier may not know which is the last hop router, or
that router may be behind a firewall that blocks unicast packets but that router may be behind a firewall that blocks unicast packets but
passes multicast packets. In these cases, the mtrace2 request should passes multicast packets. In these cases, the mtrace2 request should
be multicasted to the group being traced (since the last hop router be multicasted to ALL-ROUTERS.MCAST.NET (224.0.0.2) for IPv4 or All
listens to that group). All routers except the correct last hop Routers Address (FF02::2) for IPv6. All routers except the correct
router should ignore any mtrace2 request received via multicast. last hop router should ignore any mtrace2 request received via
Mtrace2 requests which are multicasted to the group being traced must multicast. Mtrace2 requests which are multicasted to the group being
include the Router Alert option [8]. traced must include the Router Alert option[8][9].
Another alternative is to unicast to the trace destination.
Traceroute requests which are unicasted to the trace destination must
include the Router Alert option, in order that the last-hop router is
aware of the packet.
If the traceroute querier is attached to the same router as the Another alternative is to unicast to the trace destination. Mtrace2
destination of the request, the traceroute request may be multicasted requests which are unicasted to the trace destination must include
to ALL-ROUTERS.MCAST.NET (224.0.0.2) for IPv4 or All Routers Address the Router Alert option, in order that the last-hop router is aware
(FF02::2) for IPv6 if the last-hop router is not known. of the packet.
9.3. First hop router 9.5. First Hop Router
The mtrace2 querier may not be unicast reachable from the first hop The mtrace2 querier may not be unicast reachable from the first hop
router. In this case, the querier should set the traceroute response router. In this case, the querier should set the traceroute response
address to a multicast address, and should set the response TTL (or address to a multicast address, and should set the response TTL (or
hop limit) to a value sufficient for the response from the first hop hop limit) to a value sufficient for the response from the first hop
router to reach the querier. It may be appropriate to start with a router to reach the querier. It may be appropriate to start with a
small TTL and increase in subsequent attempts until a sufficient TTL small TTL and increase in subsequent attempts until a sufficient TTL
is reached, up to an appropriate maximum (such as 192). is reached, up to an appropriate maximum (such as 192).
The IANA has assigned 224.0.1.32, MTRACE.MCAST.NET as the default The IANA has assigned 224.0.1.32, MTRACE.MCAST.NET as the default
multicast group for IPv4 mtrace2 responses, and will assign multicast group for IPv4 mtrace2 responses, and will assign
MTRACE2_IPV6RESPADDR (TBD (see Section 11)) for IPv6 mtrace2 MTRACE2_IPV6RESPADDR (TBD (see Section 12)) for IPv6 mtrace2
responses. Other groups may be used if needed, e.g. when using responses. Other groups may be used if needed, e.g. when using
mtrace2 to diagnose problems with the IANA-assigned group. mtrace2 to diagnose problems with the IANA-assigned group.
9.4. Broken intermediate router 9.6. Broken Intermediate Router
A broken intermediate router might simply not understand traceroute A broken intermediate router might simply not understand traceroute
packets, and drop them. The querier would then get no response at packets, and drop them. The querier would then get no response at
all from its traceroute requests. It should then perform a hop-by- all from its traceroute requests. It should then perform a hop-by-
hop search by setting the number of responses field until it gets a hop search by setting the number of responses field until it gets a
response (both linear and binary search are options, but binary is response (both linear and binary search are options, but binary is
likely to be slower because a failure requires waiting for a likely to be slower because a failure requires waiting for a
timeout). timeout).
9.5. Mtrace2 termination 9.7. Mtrace2 Termination
When performing an expanding hop-by-hop trace, it is necessary to When performing an expanding hop-by-hop trace, it is necessary to
determine when to stop expanding. determine when to stop expanding.
9.5.1. Arriving at source 9.7.1. Arriving at source
A trace can be determined to have arrived at the source if the A trace can be determined to have arrived at the source if the
Incoming Interface of the last router in the trace is non-zero, but Incoming Interface of the last router in the trace is non-zero, but
the Previous Hop router is zero. the Previous Hop router is zero.
9.5.2. Fatal error 9.7.2. Fatal error
A trace has encountered a fatal error if the last Forwarding Error in A trace has encountered a fatal error if the last Forwarding Error in
the trace has the 0x80 bit set. the trace has the 0x80 bit set.
9.5.3. No previous hop 9.7.3. No previous hop
A trace can not continue if the last Previous Hop in the trace is set A trace can not continue if the last Previous Hop in the trace is set
to 0. to 0.
9.5.4. Traceroute shorter than requested 9.7.4. Traceroute shorter than requested
If the trace that is returned is shorter than requested (i.e. the If the trace that is returned is shorter than requested (i.e. the
number of Response blocks is smaller than the "# hops" field), the number of Response blocks is smaller than the "# hops" field), the
trace encountered an error and could not continue. trace encountered an error and could not continue.
9.6. Continuing after an error 9.8. Continuing after an error
When the NO_SPACE error occurs, the client might try to continue the When the NO_SPACE error occurs, the client might try to continue the
trace by starting it at the last hop in the trace. It can do this by trace by starting it at the last hop in the trace. It can do this by
unicasting to this router's outgoing interface address, keeping all unicasting to this router's outgoing interface address, keeping all
fields the same. If this results in a single hop and a "WRONG_IF" fields the same. If this results in a single hop and a "WRONG_IF"
error, the client may try setting the trace destination to the same error, the client may try setting the trace destination to the same
outgoing interface address. outgoing interface address.
If a trace times out, it is likely to be because a router in the If a trace times out, it is likely to be because a router in the
middle of the path does not support multicast traceroute. That middle of the path does not support multicast traceroute. That
router's address will be in the Previous Hop field of the last entry router's address will be in the Previous Hop field of the last entry
in the last reply packet received. A client may be able to determine in the last response packet received. A client may be able to
(via mrinfo or SNMP [6][10]) a list of neighbors of the non- determine (via mrinfo or SNMP [6][11]) a list of neighbors of the
responding router. If desired, each of those neighbors could be non-responding router. If desired, each of those neighbors could be
probed to determine the remainder of the path. Unfortunately, this probed to determine the remainder of the path. Unfortunately, this
heuristic may end up with multiple paths, since there is no way of heuristic may end up with multiple paths, since there is no way of
knowing what the non-responding router's algorithm for choosing a knowing what the non-responding router's algorithm for choosing a
previous-hop router is. However, if all paths but one flow back previous-hop router is. However, if all paths but one flow back
towards the non-responding router, it is possible to be sure that towards the non-responding router, it is possible to be sure that
this is the correct path. this is the correct path.
9.7. Multicast Traceroute and shared tree routing protocols 10. Protocol-Specific Considerations
When using shared-tree routing protocols like PIM-SM and CBT, a more
advanced client may use multicast traceroute to determine paths or
potential paths.
9.7.1. PIM-SM 10.1. PIM-SM
When a multicast traceroute reaches a PIM-SM RP and the RP does not When a multicast traceroute reaches a PIM-SM RP and the RP does not
forward the trace on, it means that the RP has not performed a forward the trace on, it means that the RP has not performed a
source-specific join so there is no more state to trace. However, source-specific join so there is no more state to trace. However,
the path that traffic would use if the RP did perform a source- the path that traffic would use if the RP did perform a source-
specific join can be traced by setting the trace destination to the specific join can be traced by setting the trace destination to the
RP, the trace source to the traffic source, and the trace group to 0. RP, the trace source to the traffic source, and the trace group to 0.
This trace Query may be unicasted to the RP. This trace Query may be unicasted to the RP.
9.7.2. Bi-directional PIM 10.2. Bi-Directional PIM
Bi-directional PIM [13] is a variant of PIM-SM that builds bi- Bi-directional PIM [13] is a variant of PIM-SM that builds bi-
directional shared trees connecting multicast sources and receivers. directional shared trees connecting multicast sources and receivers.
Along the bi-directional shared trees, multicast data is natively Along the bi-directional shared trees, multicast data is natively
forwarded from sources to the RPA (Rendezvous Point Address) and from forwarded from sources to the RPA (Rendezvous Point Address) and from
the RPA to receivers without requiring source-specific state. In the RPA to receivers without requiring source-specific state. In
contrast to PIM-SM, RP always has the state to trace. contrast to PIM-SM, RP always has the state to trace.
A Designated Forwarder (DF) for a given RPA is in charge of A Designated Forwarder (DF) for a given RPA is in charge of
forwarding downstream traffic onto its link, and forwarding upstream forwarding downstream traffic onto its link, and forwarding upstream
traffic from its link towards the RPL (Rendezvous Point Link) that traffic from its link towards the RPL (Rendezvous Point Link) that
the RPA belongs to. Hence mtrace2 reports DF addresses or RPA along the RPA belongs to. Hence mtrace2 reports DF addresses or RPA along
the path. the path.
9.7.3. CBT 10.3. PIM-DM
When a multicast traceroute reaches a CBT [12] Core, it must simply
stop since CBT does not have source-specific state. However, a
second trace can be performed, setting the trace destination to the
traffic source, the trace group to the group being traced, and the
trace source to the Core (or to 0, since CBT does not have source-
specific state). This trace Query may be unicasted to the Core.
There are two possibilities when combining the two traces:
9.7.3.1. No overlap
If there is no overlap between the two traces, the second trace can
be reversed and appended to the first trace. This composite trace
shows the full path from the source to the destination.
9.7.3.2. Overlapping paths
If there is a portion of the path that is common to the ends of the
two traces, that portion is removed from both traces. Then, as in
the no overlap case, the second trace is reversed and appended to the
first trace, and the composite trace again contains the full path.
This algorithm works whether the source has joined the CBT tree or
not.
9.8. Protocol-specific considerations
9.8.1. DVMRP
DVMRP's dominant router election and route exchange guarantees that
DVMRP routers know whether or not they are the last-hop forwarder for
the link and who the previous hop is.
9.8.2. PIM-DM
Routers running PIM Dense Mode do not know the path packets would Routers running PIM Dense Mode do not know the path packets would
take unless traffic is flowing. Without some extra protocol take unless traffic is flowing. Without some extra protocol
mechanism, this means that in an environment with multiple possible mechanism, this means that in an environment with multiple possible
paths with branch points on shared media, multicast traceroute can paths with branch points on shared media, multicast traceroute can
only trace existing paths, not potential paths. When there are only trace existing paths, not potential paths. When there are
multiple possible paths but the branch points are not on shared multiple possible paths but the branch points are not on shared
media, the previous hop router is known, but the last hop router may media, the previous hop router is known, but the last hop router may
not know that it is the appropriate last hop. not know that it is the appropriate last hop.
When traffic is flowing, PIM Dense Mode routers know whether or not When traffic is flowing, PIM Dense Mode routers know whether or not
they are the last-hop forwarder for the link (because they won or they are the last-hop forwarder for the link (because they won or
lost an Assert battle) and know who the previous hop is (because it lost an Assert battle) and know who the previous hop is (because it
won an Assert battle). Therefore, multicast traceroute is always won an Assert battle). Therefore, multicast traceroute is always
able to follow the proper path when traffic is flowing. able to follow the proper path when traffic is flowing.
10. Problem Diagnosis 10.4. IGMP/MLD Proxy
10.1. Forwarding Inconsistencies When a mtrace2 Query packet reaches an incoming interface of IGMP/MLD
Proxy [14], it must be simply discarded. When a mtrace2 Query packet
reaches an outgoing interface of IGMP/MLD Proxy, it is forwarded
through its incoming interface towards the upstream router.
10.5. AMT
AMT [15] provides the multicast connectivity to the unicast-only
inter-network. To do this, multicast packets being sent to or from a
site are encapsulated in unicast packets. When a mtrace2 Query
packet reaches an AMT Pseudo-Interface of an AMT Gateway, the AMT
Gateway encapsulats it to a particular AMT Relay reachable across the
unicast-only infrastructure.
11. Problem Diagnosis
11.1. Forwarding Inconsistencies
The forwarding error code can tell if a group is unexpectedly pruned The forwarding error code can tell if a group is unexpectedly pruned
or administratively scoped. or administratively scoped.
10.2. TTL or hop limit problems 11.2. TTL or Hop Limit Problems
By taking the maximum of (hops from source + forwarding TTL (or hop By taking the maximum of hops (from source + forwarding TTL (or hop
limit) threshold) over all hops, you can discover the TTL required limit) threshold) over all hops, you can discover the TTL or hop
for the source to reach the destination. limit required for the source to reach the destination.
10.3. Packet loss 11.3. Packet loss
By taking two traces, you can find packet loss information by By taking two traces, you can find packet loss information by
comparing the difference in input packet counts to the difference in comparing the difference in input packet counts to the difference in
output packet counts at the previous hop. On a point-to-point link, output packet counts for the specified source-group address pair at
any difference in these numbers implies packet loss. Since the the previous hop. On a point-to-point link, any difference in these
packet counts may be changing as the trace query is propagating, numbers implies packet loss. Since the packet counts may be changing
there may be small errors (off by 1 or 2) in these statistics. as the mtrace2 query is propagating, there may be small errors (off
However, these errors will not accumulate if multiple traces are by 1 or 2 or more) in these statistics. However, these errors will
taken to expand the measurement period. On a shared link, the count not accumulate if multiple traces are taken to expand the measurement
of input packets can be larger than the number of output packets at period. On a shared link, the count of input packets can be larger
the previous hop, due to other routers or hosts on the link injecting than the number of output packets at the previous hop, due to other
packets. This appears as "negative loss" which may mask real packet routers or hosts on the link injecting packets. This appears as
loss. "negative loss" which may mask real packet loss.
In addition to the counts of input and output packets for all In addition to the counts of input and output packets for all
multicast traffic on the interfaces, the response data includes a multicast traffic on the interfaces, the response data includes a
count of the packets forwarded by a node for the specified source- count of the packets forwarded by a node for the specified source-
group pair. Taking the difference in this count between two traces group pair. Taking the difference in this count between two traces
and then comparing those differences between two hops gives a measure and then comparing those differences between two hops gives a measure
of packet loss just for traffic from the specified source to the of packet loss just for traffic from the specified source to the
specified receiver via the specified group. This measure is not specified receiver via the specified group. This measure is not
affected by shared links. affected by shared links.
On a point-to-point link that is a multicast tunnel, packet loss is On a point-to-point link that is a multicast tunnel, packet loss is
usually due to congestion in unicast routers along the path of that usually due to congestion in unicast routers along the path of that
tunnel. On native multicast links, loss is more likely in the output tunnel. On native multicast links, loss is more likely in the output
queue of one hop, perhaps due to priority dropping, or in the input queue of one hop, perhaps due to priority dropping, or in the input
queue at the next hop. The counters in the response data do not queue at the next hop. The counters in the response data do not
allow these cases to be distinguished. Differences in packet counts allow these cases to be distinguished. Differences in packet counts
between the incoming and outgoing interfaces on one node cannot between the incoming and outgoing interfaces on one node cannot
generally be used to measure queue overflow in the node. generally be used to measure queue overflow in the node.
10.4. Link Utilization 11.4. Link Utilization
Again, with two traces, you can divide the difference in the input or Again, with two traces, you can divide the difference in the input or
output packet counts at some hop by the difference in time stamps output packet counts at some hop by the difference in time stamps
from the same hop to obtain the packet rate over the link. If the from the same hop to obtain the packet rate over the link. If the
average packet size is known, then the link utilization can also be average packet size is known, then the link utilization can also be
estimated to see whether packet loss may be due to the rate limit or estimated to see whether packet loss may be due to the rate limit or
the physical capacity on a particular link being exceeded. the physical capacity on a particular link being exceeded.
10.5. Time delay 11.5. Time Delay
If the routers have synchronized clocks, it is possible to estimate If the routers have synchronized clocks, it is possible to estimate
propagation and queuing delay from the differences between the propagation and queuing delay from the differences between the
timestamps at successive hops. However, this delay includes control timestamps at successive hops. However, this delay includes control
processing overhead, so is not necessarily indicative of the delay processing overhead, so is not necessarily indicative of the delay
that data traffic would experience. that data traffic would experience.
11. IANA Considerations 12. IANA Considerations
The following new assignments can only be made via a Standards Action The following new assignments can only be made via a Standards Action
as specified in [5]. as specified in [5].
11.1. Routing protocols 12.1. Forwarding Codes
The IANA is responsible for allocating new Routing Protocol codes.
The Routing Protocol code is somewhat problematic, since in the case
of protocols like CBT and PIM it must encode both a unicast routing
algorithm and a multicast tree-building protocol. The space was not
divided into two fields because it was already small and some
combinations (e.g. DVMRP) would be wasted.
11.2. Forwarding codes
New Forwarding codes must only be created by an RFC that modifies New Forwarding codes must only be created by an RFC that modifies
this document's Section 9, fully describing the conditions under this document's Section 9, fully describing the conditions under
which the new forwarding code is used. The IANA may act as a central which the new forwarding code is used. The IANA may act as a central
repository so that there is a single place to look up forwarding repository so that there is a single place to look up forwarding
codes and the document in which they are defined. codes and the document in which they are defined.
11.3. UDP destination port and IPv6 address 12.2. UDP Destination Port and IPv6 Address
The IANA should allocate UDP destination port for multicast The IANA should allocate UDP destination port for multicast
traceroute version 2 upon publication of the first RFC. traceroute version 2 upon publication of the first RFC.
Additionally, the well-known multicast address (MTRACE2_IPV6RESPADDR) Additionally, the well-known multicast address (MTRACE2_IPV6RESPADDR)
intended for default use by IPv6 multicast traceroute should be intended for default use by IPv6 multicast traceroute should be
registered and defined by the first RFC published. registered and defined by the first RFC published.
12. Security Considerations 13. Security Considerations
12.1. Topology Discovery 13.1. Topology Discovery
Mtrace2 can be used to discover any actively-used topology. If your Mtrace2 can be used to discover any actively-used topology. If your
network topology is a secret, mtrace2 may be restricted at the border network topology is a secret, mtrace2 may be restricted at the border
of your domain, using the ADMIN_PROHIB forwarding code. of your domain, using the ADMIN_PROHIB forwarding code.
12.2. Traffic Rates 13.2. Traffic Rates
Mtrace2 can be used to discover what sources are sending to what Mtrace2 can be used to discover what sources are sending to what
groups and at what rates. If this information is a secret, mtrace2 groups and at what rates. If this information is a secret, mtrace2
may be restricted at the border of your domain, using the may be restricted at the border of your domain, using the
ADMIN_PROHIB forwarding code. ADMIN_PROHIB forwarding code.
12.3. Unicast Replies 13.3. Unicast Replies
The "Response address" field may be used to send a single packet (the The "Response address" field may be used to send a single packet (the
traceroute Reply packet) to an arbitrary unicast address. It is traceroute Reply packet) to an arbitrary unicast address. It is
possible to use this facility as a packet amplifier, as a small possible to use this facility as a packet amplifier, as a small
multicast traceroute Query may turn into a large Reply packet. multicast traceroute Query may turn into a large Reply packet.
13. Acknowledgements 14. Acknowledgements
This specification started largely as a transcription of Van This specification started largely as a transcription of Van
Jacobson's slides from the 30th IETF, and the implementation in Jacobson's slides from the 30th IETF, and the implementation in
mrouted 3.3 by Ajit Thyagarajan. Van's original slides credit Steve mrouted 3.3 by Ajit Thyagarajan. Van's original slides credit Steve
Casner, Steve Deering, Dino Farinacci and Deb Agrawal. The original Casner, Steve Deering, Dino Farinacci and Deb Agrawal. The original
multicast traceroute client, mtrace (version 1), has been implemented multicast traceroute client, mtrace (version 1), has been implemented
by Ajit Thyagarajan, Steve Casner and Bill Fenner. by Ajit Thyagarajan, Steve Casner and Bill Fenner.
The idea of unicasting a multicast traceroute Query to the The idea of unicasting a multicast traceroute Query to the
destination of the trace with Router Alert set is due to Tony destination of the trace with Router Alert set is due to Tony
Ballardie. The idea of the "S" bit to allow statistics for a source Ballardie. The idea of the "S" bit to allow statistics for a source
subnet is due to Tom Pusateri. subnet is due to Tom Pusateri.
14. References For the mtrace version 2 specification, extensive comments were
received from Yiqun Cai, Liu Hui, Bharat Joshi, Shinsuke Suzuki, and
Cao Wei.
14.1. Normative References 15. References
15.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to indicate requirement [1] Bradner, S., "Key words for use in RFCs to indicate requirement
levels", RFC 2119, March 1997. levels", RFC 2119, March 1997.
[2] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) [2] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998. Specification", RFC 2460, December 1998.
[3] Hinden, R. and S. Deering, "IP Version 6 Addressing [3] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998. Architecture", RFC 2373, July 1998.
[4] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. [4] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version 3", Thyagarajan, "Internet Group Management Protocol, Version 3",
RFC 3376, October 2002. RFC 3376, October 2002.
[5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, October 1998. Considerations Section in RFCs", RFC 2434, October 1998.
14.2. Informative References 15.2. Informative References
[6] Draves, R. and D. Thaler, "Default Router Preferences and More- [6] Draves, R. and D. Thaler, "Default Router Preferences and More-
Specific Routes", RFC 4191, November 2005. Specific Routes", RFC 4191, November 2005.
[7] Braden, B., Borman, D., and C. Partridge, "Computing the [7] Braden, B., Borman, D., and C. Partridge, "Computing the
Internet Checksum", RFC 1071, September 1988. Internet Checksum", RFC 1071, September 1988.
[8] Katz, D., "IP Router Alert Option", RFC 2113, February 1997. [8] Katz, D., "IP Router Alert Option", RFC 2113, February 1997.
[9] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", [9] Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
RFC 2711, October 1999.
[10] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB",
RFC 2863, June 2000. RFC 2863, June 2000.
[10] McWalter, D., Thaler, D., and A. Kessler, "IP Multicast MIB", [11] McWalter, D., Thaler, D., and A. Kessler, "IP Multicast MIB",
draft-ietf-mboned-ip-mcast-mib-05.txt (work in progress), draft-ietf-mboned-ip-mcast-mib-05.txt (work in progress),
March 2007. March 2007.
[11] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, [12] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM): "Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006. Protocol Specification (Revised)", RFC 4601, August 2006.
[12] Ballardie, T., "Core Based Trees (CBT version 2) Multicast [13] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
Routing -- Protocol Specification --", RFC 2189, "Bidirectional Protocol Independent Multicast (BIDIR-PIM)",
September 1997. RFC 5015, October 2007.
[13] Handley, M., Kouvelas, I., and T. Speakman, "Bi-directional [14] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet
Protocol Independent Multicast (BIDIR-PIM)", Group Management Protocol (IGMP) / Multicast Listener Discovery
draft-ietf-pim-bidir-09.txt (work in progress), February 2007. (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")",
RFC 4605, August 2006.
[15] Thaler, D., Talwar, M., Aggarwal, A., Vicisano, L., and T.
Pusateri, "Automatic IP Multicast Without Explicit Tunnels
(AMT)", draft-ietf-mboned-auto-multicast-08.txt (work in
progress), October 2007.
Authors' Addresses Authors' Addresses
Hitoshi Asaeda Hitoshi Asaeda
Keio University Keio University
Graduate School of Media and Governance Graduate School of Media and Governance
Fujisawa, Kanagawa 252-8520 Fujisawa, Kanagawa 252-8520
Japan Japan
Email: asaeda@wide.ad.jp Email: asaeda@wide.ad.jp
Tatsuya Jinmei Tatuya Jinmei
Toshiba Corporation Internet Systems Consortium
Corporate Research & Development Center Redwood City, CA 94063
Kawasaki, Kanagawa 212-8582 US
Japan
Email: jinmei@isl.rdc.toshiba.co.jp Email: Jinmei_Tatuya@isc.org
William C. Fenner William C. Fenner
AT&T Research Arastra, Inc.
Menlo Park, CA 94025 Menlo Park, CA 94025
US US
Email: fenner@research.att.com Email: fenner@fenron.com
Stephen L. Casner Stephen L. Casner
Packet Design, Inc. Packet Design, Inc.
Palo Alto, CA 94304 Palo Alto, CA 94304
US US
Email: casner@packetdesign.com Email: casner@packetdesign.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
skipping to change at page 39, line 44 skipping to change at line 1351
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
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Acknowledgment
Funding for the RFC Editor function is provided by the IETF
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