draft-ietf-grow-simple-va-12.txt   rfc6769.txt 
GROW Working Group R. Raszuk Internet Engineering Task Force (IETF) R. Raszuk
Internet-Draft NTT MCL Request for Comments: 6769 NTT MCL
Intended status: Informational J. Heitz Category: Informational J. Heitz
Expires: February 17, 2013 Ericsson ISSN: 2070-1721 Ericsson
A. Lo A. Lo
Arista Arista
L. Zhang L. Zhang
UCLA UCLA
X. Xu X. Xu
Huawei Huawei
August 16, 2012 October 2012
Simple Virtual Aggregation (S-VA) Simple Virtual Aggregation (S-VA)
draft-ietf-grow-simple-va-12.txt
Abstract Abstract
All BGP routers in the Default Free Zone (DFZ) are required to carry All BGP routers in the Default-Free Zone (DFZ) are required to carry
all the routes in the Default Free Routing Table (DFRT). A technique all routes in the Default-Free Routing Table (DFRT). This document
is described that allows some BGP routers not to install all of those describes a technique, Simple Virtual Aggregation (S-VA), that allows
routes into the Forwarding Information Base (FIB). some BGP routers not to install all of those routes into the
Forwarding Information Base (FIB).
Some routers in an Autonomous System (AS) announce an aggregate (the Some routers in an Autonomous System (AS) announce an aggregate (the
VA prefix) in addition to the routes they already announce. This VA prefix) in addition to the routes they already announce. This
enables other routers not to install the routes covered by the VA enables other routers not to install the routes covered by the VA
prefix into the FIB as long as those routes have the same next-hop as prefix into the FIB as long as those routes have the same next-hop as
the VA prefix. the VA prefix.
The VA prefixes that are announced within an AS are not announced to The VA prefixes that are announced within an AS are not announced to
any other AS. Described functionality is of very low operational any other AS. The described functionality is of very low operational
complexity by proposing a confined BGP speaker solution without any complexity, as it proposes a confined BGP speaker solution without
dependency on network wide configuration or requirement for any form any dependency on network-wide configuration or requirement for any
of intra-domain tunneling. form of intra-domain tunneling.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This document is not an Internet Standards Track specification; it is
Task Force (IETF). Note that other groups may also distribute published for informational purposes.
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
This Internet-Draft will expire on February 17, 2013. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6769.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
1.1. Scope of this Document . . . . . . . . . . . . . . . . . . 4 1.1. Scope of This Document .....................................3
1.2. Requirements notation . . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Notation ......................................3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Terminology ................................................3
2. Operation of S-VA . . . . . . . . . . . . . . . . . . . . . . . 5 2. Operation of S-VA ...............................................4
3. Deployment considerations . . . . . . . . . . . . . . . . . . . 7 3. Deployment Considerations .......................................6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 4. Security Considerations .........................................7
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 5. Acknowledgements ................................................7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 6. Normative References ............................................7
7. Normative References . . . . . . . . . . . . . . . . . . . . . 8 7. Informative References ..........................................7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
A technique called Simple Virtual Aggregation (S-VA) is described. This document describes a technique called Simple Virtual Aggregation
It allows some routers not to have to store some routes in the (S-VA). It allows some routers not to store some routes in the
Forwarding Information Base (FIB) while still advertising and Forwarding Information Base (FIB) while still advertising and
receiving the full Default Free Routing Table (DFRT) in BGP. receiving the full Default-Free Routing Table (DFRT) in BGP.
A typical scenario is as follows. Core routers in the ISP maintain A typical scenario is as follows. Core routers in the ISP maintain
the full DFRT in the FIB and RIB. Edge routers maintain the full the full DFRT in the FIB and Routing Information Base (RIB). Edge
DFRT in the BGP Loc-RIB, but do not install certain routes in the RIB routers maintain the full DFRT in the BGP Local RIB (Loc-RIB), but do
and FIB. Edge routers may install a default route to core routers, not install certain routes in the RIB and FIB. Edge routers may
to Area Border Routers (ABR) which are installed on the Point of install a default route to core routers, to Area Border Routers (ABR)
Presence (POP), to core boundary routers or to Autonomous System that are installed on the Point of Presence (POP), to core boundary
Border Routers (ASBR). routers, or to Autonomous System Border Routers (ASBRs).
S-VA must be enabled on an edge router that needs to save its RIB and S-VA must be enabled on an edge router that needs to save its RIB and
FIB space. The core routers must announce a new prefix called FIB space. The core routers must announce a new prefix called
virtual aggregate (VA prefix). Virtual Aggregate (VA prefix).
1.1. Scope of this Document 1.1. Scope of This Document
The VA prefix is not intended to be announced from one AS into The VA prefix is not intended to be announced from one AS into
another, only between routers of the same AS. another, only between routers of the same AS.
S-VA can be used for IPv4 and IPv6 both unicast and multicast address S-VA can be used for both IPv4 unicast and multicast address families
families. and IPv6 unicast and multicast address families.
S-VA does not need to operate on on every router in an AS. S-VA does not need to operate on every router in an AS.
1.2. Requirements notation 1.2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
1.3. Terminology 1.3. Terminology
RIB/FIB-Installing Router (FIR): A router that does not suppress any RIB/FIB-Installing Router (FIR): A router that does not suppress any
routes and announces the VA prefix. Typically a core router, a routes and announces the VA prefix. Typically, a core router, a
POP to core boundary router or an ASBR would be configured as an POP to core boundary router, or an ASBR would be configured as an
FIR. FIR.
RIB/FIB-Suppressing Router (FSR): An S-VA router that installs the RIB/FIB-Suppressing Router (FSR): An S-VA router that installs the
VA prefix, and does not install into its FIB routes that are VA prefix, but does not install routes that are covered by and
covered by and have the same next-hop as the VA prefix. Typically have the same next-hop as the VA prefix into its FIB. Typically,
an edge router would be configured as an FSR. an edge router would be configured as an FSR.
Suppress: Not to install a route that is covered by the VA prefix Suppress: Not to install a route that is covered by the VA prefix
into the global RIB or FIB. into the global RIB or FIB.
Legacy Router: A router that does not run S-VA, and has no knowledge
Legacy Router: A router that does not run S-VA and has no knowledge
of S-VA. of S-VA.
Global Routing Information Base (RIB): All the routing protocols in
a router install their selected routes into the RIB. The routes Global Routing Information Base (RIB): All routing protocols in a
in the RIB are used to resolve next-hops for other routes, to be router install their selected routes into the RIB. The routes in
redistributed to other routing protocols and to be installed into the RIB are used to resolve next-hops for other routes, to be
redistributed to other routing protocols, and to be installed into
the FIB. the FIB.
Local/Protocol Routing Information Base (Loc-RIB): The Loc-RIB Local/Protocol Routing Information Base (Loc-RIB): The Loc-RIB
contains the routes that have been selected by the local BGP contains the routes that have been selected by the local BGP
speaker's Decision Process as in [RFC4271]. speaker's Decision Process as in [RFC4271].
NLRI: Network Layer Reachability Information [RFC4271] NLRI: Network Layer Reachability Information [RFC4271]
2. Operation of S-VA 2. Operation of S-VA
There are three types of routers in S-VA, FIB-Installing routers There are three types of routers in S-VA: FIB-Installing routers
(FIR), FIB-Suppressing routers (FSR) and optionally, legacy routers. (FIR), FIB-Suppressing routers (FSR), and, optionally, legacy
While any router can be an FIR or an FSR, the simplest form of routers. While any router can be an FIR or an FSR, the simplest form
deployment is for AS border routers to be configured as FIRs and for of deployment is for AS border routers to be configured as FIRs and
customer facing edge routers to be configured as FSRs. for customer facing edge routers to be configured as FSRs.
When a FIR announces a VA prefix, it sets the path attributes as When a FIR announces a VA prefix, it sets the path attributes as
follows: The ORIGIN MUST be set to INCOMPLETE (value 2). The follows. The ORIGIN MUST be set to INCOMPLETE (value 2). The
NEXT_HOP MUST be set to the same as that of the routes which are NEXT_HOP MUST be set to the same value as that of the routes that are
intended to be covered by the VA prefix. The ATOMIC_AGGREGATE and intended to be covered by the VA prefix. The ATOMIC_AGGREGATE and
AGGREGATOR attributes SHOULD NOT be included. The FIR MUST attach a AGGREGATOR attributes SHOULD NOT be included. The FIR MUST attach a
NO_EXPORT Community Attribute [RFC1997]. The NLRI SHOULD be 0/0. NO_EXPORT community attribute [RFC1997]. The NLRI SHOULD be 0/0.
A FIR SHOULD NOT FIB-suppress any routes. A FIR SHOULD NOT FIB-suppress any routes.
An FSR must detect the VA prefix or prefixes (including 0/0) and An FSR must detect the VA prefix or prefixes (including 0/0) and
install them in all of Loc-RIB, RIB and FIB. The FSR MAY suppress install them in all of Loc-RIB, RIB, and FIB. The FSR MAY suppress
any more specific routes that carry the same next-hop as the VA any more-specific routes that carry the same next-hop as the VA
prefix. prefix.
Generally, any more specific route which carries the same next-hop as Generally, any more-specific route that carries the same next-hop as
the VA prefix is eligible for suppression. However, provided that the VA prefix is eligible for suppression. However, provided that
there is at least one less specific prefix with different next-hop there is at least one less-specific prefix with a different next-hop
between the VA prefix and the suppressed prefixes then those between the VA prefix and the suppressed prefixes, then those
suppressed prefixes must be reinstalled. suppressed prefixes must be reinstalled.
An example with 3 prefixes can be considered, where the VA-prefix An example with three prefixes can be considered where the VA-prefix
(prefix 1) is the least specific and covers prefix 2 and prefix 3. (prefix 1) is the least specific and covers prefix 2 and prefix 3.
Prefix 2 is less specific than prefix 3 and covers the latter. If Prefix 2 is less specific than prefix 3 and covers the latter. If
all three have the same next-hop, then only the bigger one, i.e. VA- all three have the same next-hop, then only the bigger one, i.e.,
Prefix, is announced. However, if prefix 2 has a different next-hop, VA-Prefix, is announced. However, if prefix 2 has a different
then it will need to be announce separately. In this case, it is next-hop, then it will need to be announced separately. In this
important to also announce prefix 3 separately. case, it is important to also announce prefix 3 separately.
Similarly, when IBGP multipath is enabled and when multiple VA Similarly, when Internal BGP (IBGP) multipath is enabled, and when
prefixes form a multipath, only those more specific prefixes of which multiple VA prefixes form a multipath, only those more-specific
the set of next-hops are identical to the set of next-hops of the VA prefixes of which the set of next-hops are identical to the set of
prefix multipath are subject to suppression. next-hops of the VA prefix multipath are subject to suppression.
The expected behavior is illustrated in Figure 1. This figure shows The expected behavior is illustrated in Figure 1. This figure shows
an autonomous system with a FIR FIR1 and an FSR FSR1. FSR1 is an an AS with a FIR, FIR1, and an FSR, FSR1. FSR1 is an ASBR and is
ASBR and is connected to two external ASBRs, EP1 and EP2. connected to two external ASBRs, EP1 and EP2.
+------------------------------------------+ +------------------------------------------+
| Autonomous System | +----+ | Autonomous System | +----+
| | |EP1 | | | |EP1 |
| /---+---| | | /---+---| |
| To ----\ +----+ +----+ / | +----+ | To ----\ +----+ +----+ / | +----+
| Other \|FIR1|----------|FSR1|/ | | Other \|FIR1|----------|FSR1|/ |
|Routers /| | | |\ | |Routers /| | | |\ |
| ----/ +----+ +----+ \ | +----+ | ----/ +----+ +----+ \ | +----+
| \---+---|EP2 | | \---+---|EP2 |
| | | | | | | |
| | +----+ | | +----+
+------------------------------------------+ +------------------------------------------+
Figure 1
Suppose that FSR1 has been enabled to perform S-VA. Originally it Figure 1
Suppose that FSR1 has been enabled to perform S-VA. Originally, it
receives all routes from FIR1 (doing next-hop-self) as well as from receives all routes from FIR1 (doing next-hop-self) as well as from
EP1 and EP2. FIR1 now will advertise a VA prefix 0/0 with next-hop EP1 and EP2. FIR1 now will advertise a VA prefix 0/0 with the next-
set to itself. That will cause FSR1 to suppress all routes with the hop set to itself. This will cause FSR1 to suppress all routes with
same next-hop as the VA prefix. However, FSR1 will not suppress any the same next-hop as the VA prefix. However, FSR1 will not suppress
routes received from EP1 and EP2, because their next-hops are any routes received from EP1 and EP2, because their next-hops are
different from that of the VA prefix. different from that of the VA prefix.
Several FIRs may announce different S-VA prefixes. For example, in a Several FIRs may announce different S-VA prefixes. For example, in a
POP, each edge router can announce into the POP an S-VA prefix that POP, each edge router can announce into the POP an S-VA prefix that
covers the addresses of the customers it services. covers the addresses of the customers it services.
Several FIRs may announce the same S-VA prefix. In this case an FSR Several FIRs may announce the same S-VA prefix. In this case, an FSR
must choose to install only one of them. For example, two redundant must choose to install only one of them. For example, two redundant
ASBRs, both of which announce the complete DFRT may each also ASBRs, both of which announce the complete DFRT, may each also
announce the default route as an S-VA prefix into the AS. announce the default route as an S-VA prefix into the AS.
S-VA may be used to split traffic among redundant exit routers. For S-VA may be used to split traffic among redundant exit routers. For
example, referring to Figure 1, suppose EP1 and EP2 are two redundant example, suppose in Figure 1 that EP1 and EP2 are two redundant ASBRs
ASBRs that announce the complete DFRT. Each may also announce two that announce the complete DFRT. Each may also announce two S-VA
S-VA prefixes into the AS: 0/1 and 128/1. EP1 might announce 0/1 prefixes into the AS: 0/1 and 128/1. EP1 might announce 0/1 with
with higher preference and EP2 might announce 128/1 with higher higher preference and EP2 might announce 128/1 with higher
preference. FIR1 will now install into its FIB 0/1 pointing to EP1 preference. FIR1 will now install into its FIB 0/1 pointing to EP1
and 128/1 pointing to EP2. If either one of EP1 or EP2 were to fail, and 128/1 pointing to EP2. If either EP1 or EP2 were to fail, then
then FSR1 would switch the traffic to the other exit router with a FSR1 would switch the traffic to the other exit router with a single
single FIB installation of one S-VA prefix. FIB installation of one S-VA prefix.
3. Deployment considerations 3. Deployment Considerations
BGP routes may be used to resolve next-hops for static routes or BGP routes may be used to resolve next-hops for static routes or
other BGP routes. Because the default route does not imply other BGP routes. Because the default route does not imply
reachability of any destination, a router can be configured not to reachability of any destination, a router can be configured to not
resolve next-hops using the default route. In this case, S-VA should resolve next-hops using the default route. In this case, S-VA should
not suppress from installation into the RIB a route that may be used not suppress a route that may be used to resolve a next-hop for
to resolve a next-hop for another route. It may still suppress it another route from installation into the RIB. It may still suppress
from installation into the FIB. it from installation into the FIB.
Selected BGP routes in the RIB may be redistributed to other Selected BGP routes in the RIB may be redistributed to other
protocols. If they no longer exist in the RIB, they will not be protocols. If they no longer exist in the RIB, they will not be
redistributed. This is especially important when the conditional redistributed. This is especially important when the conditional
redistribution is taking place based on the length of the prefix, redistribution is taking place based on the length of the prefix,
community value etc. In those cases where redistribution policy is community value, etc. In those cases where a redistribution policy
in place S-VA implementation should refrain from suppressing is in place, S-VA implementation should refrain from suppressing
installation into the RIB routes matching such policy. It may still installation into the RIB routes matching such policy. It may still
suppress them from installation into the FIB. suppress them from installation into the FIB.
A router may originate a network route or an aggregate route into A router may originate a network route or an aggregate route into
BGP. Some addresses covered by such a route may not exist. If this BGP. Some addresses covered by such a route may not exist. If this
router were to receive a packet for an unreachable address within an router were to receive a packet for an unreachable address within an
originated route, it must not send that packet to the VA prefix originated route, it must not send that packet to the VA prefix
route. There are several ways to achieve this. One is to have the route. There are several ways to achieve this. One way is to have
FIR aggregate the routes instead of the FSR. Another is to install a the FIR aggregate the routes instead of the FSR. Another way is to
blackhole route for the nonexistent addresses on the originating install a black hole route for the nonexistent addresses on the
router. This issue is not specific to S-VA, but applicable to the originating router. This issue is not specific to S-VA, but
general use of default routes. applicable to the general use of default routes.
Like any aggregate, an S-VA prefix may include more address space Like any aggregate, an S-VA prefix may include more address space
than the sum of the prefixes it covers. As such, the S-VA prefix may than the sum of the prefixes it covers. As such, the S-VA prefix may
provide a route for a packet for which no real destination exists. provide a route for a packet for which no real destination exists.
An FSR will forward such a packet to the FIR. An FSR will forward such a packet to the FIR.
If an S-VA prefix changes its next-hop or is removed, then many If an S-VA prefix changes its next-hop or is removed, then many
routes may need to be downloaded into the FIB to achieve convergence. routes may need to be downloaded into the FIB to achieve convergence.
4. IANA Considerations 4. Security Considerations
There are no IANA considerations.
5. Security Considerations
The authors are not aware of any new security considerations due to The authors are not aware of any new security considerations due to
S-VA. The local nature of the proposed optimization eliminates any S-VA. The local nature of the proposed optimization eliminates any
external exposure of the functionality. The presence of more external exposure of the functionality. The presence of more
specifics which are used as VA prefixes is also a normal BGP specifics that are used as VA prefixes is also a normal BGP behavior
behaviour in current networks. in current networks.
6. Acknowledgements 5. Acknowledgements
The concept for Virtual Aggregation comes from Paul Francis. In this The concept for Virtual Aggregation comes from Paul Francis. In this
document authors only simplified some aspects of its behavior to document, the authors only simplified some aspects of its behavior to
allow simpler adoption by some operators. allow simpler adoption by some operators.
Authors would like to thank Clarence Filsfils, Nick Hilliard, S. The authors would like to thank Clarence Filsfils, Nick Hilliard, S.
Moonesamy and Tom Petch for their review and valuable input. Moonesamy, and Tom Petch for their review and valuable input.
7. Normative References 6. Normative References
[RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Communities Attribute", RFC 1997, August 1996. Attribute", RFC 1997, August 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C. [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007. (GTSM)", RFC 5082, October 2007.
7. Informative References
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, January
2006.
Authors' Addresses Authors' Addresses
Robert Raszuk Robert Raszuk
NTT MCL NTT MCL
101 S Ellsworth Avenue Suite 350 101 S Ellsworth Avenue Suite 350
San Mateo, CA 94401 San Mateo, CA 94401
US USA
EMail: robert@raszuk.net
Email: robert@raszuk.net
Jakob Heitz Jakob Heitz
Ericsson Ericsson
300 Holger Way 300 Holger Way
San Jose, CA 95135 San Jose, CA 95134
USA USA
Phone: EMail: jakob.heitz@ericsson.com
Email: jakob.heitz@ericsson.com
Alton Lo Alton Lo
Arista Networks Arista Networks
5470 Great America Parkway 5470 Great America Parkway
Santa Clara, CA 95054 Santa Clara, CA 95054
USA USA
Phone: EMail: altonlo@aristanetworks.com
Email: altonlo@aristanetworks.com
Lixia Zhang Lixia Zhang
UCLA UCLA
3713 Boelter Hall 3713 Boelter Hall
Los Angeles, CA 90095 Los Angeles, CA 90095
US USA
Phone: EMail: lixia@cs.ucla.edu
Email: lixia@cs.ucla.edu
Xiaohu Xu Xiaohu Xu
Huawei Technologies Huawei Technologies
No.3 Xinxi Rd., Shang-Di Information Industry Base, Hai-Dian District Huawei Building, No.3 Xinxi Rd.,
Beijing, Beijing 100085 Shang-Di Information Industry Base, Hai-Dian District
P.R.China Beijing 100085
P.R. China
Phone: +86 10 82836073 Phone: +86 10 82836073
Email: xuxh@huawei.com EMail: xuxh@huawei.com
 End of changes. 67 change blocks. 
144 lines changed or deleted 150 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/