--- 1/draft-ietf-grow-collection-communities-05.txt 2006-02-04 23:23:59.000000000 +0100 +++ 2/draft-ietf-grow-collection-communities-06.txt 2006-02-04 23:23:59.000000000 +0100 @@ -1,18 +1,18 @@ INTERNET-DRAFT D. Meyer -draft-ietf-grow-collection-communities-05.txt +draft-ietf-grow-collection-communities-06.txt Category Best Current Practice Expires: March 2005 September 2004 BGP Communities for Data Collection - + Status of this Memo Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become @@ -29,37 +29,37 @@ Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This document is a product of the GROW WG. Comments should be - addressed to the authors, or the mailing list at + addressed to the author, or the mailing list at grow@lists.uoregon.edu. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract BGP communities (RFC 1997) are used by service providers for many purposes, including tagging of customer, peer, and geographically originated routes. Such tagging is typically used to control the scope of redistribution of routes within a provider's network, and to its peers and customers. With the advent of large scale BGP data collection (and associated research), it has become clear that the information carried in such communities is essential for a deeper - understanding of the global routing system. This document defines + understanding of the global routing system. This memo defines standard (outbound) communities and their encodings for export to BGP route collectors. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Peers and Peering . . . . . . . . . . . . . . . . . . . . . 5 2.2. Customer Routes . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Peer Routes . . . . . . . . . . . . . . . . . . . . . . . . 5 @@ -94,42 +94,42 @@ such as LOCAL_PREF [RFC1771] by sending appropriate communities to their service provider. Other applications include signaling various types of VPNs (e.g., VPLS [VPLS]), and carrying link bandwidth for traffic engineering applications [EXTCOMM]. With the advent of large scale BGP data collection [RIS,ROUTEVIEWS] (and associated research), it has become clear that the geographical and topological information, as well as the relationship the provider has to the source of a route (e.g., transit, peer, or customer), carried in such communities is essential for a deeper understanding - of the global routing system. This document defines standard - communities for export to BGP route collectors. These communities - represent a significant part of information carried by service - providers as of this writing, and as such could be useful for - internal use by service providers. However, such use is beyond the - scope of this memo. Finally, those involved in BGP data analysis are - encouraged to verify with their data sources as to which peers - implement this scheme (as there is a large amount of existing data as - well as many legacy peerings). + of the global routing system. This memo defines standard communities + for export to BGP route collectors. These communities represent a + significant part of information carried by service providers as of + this writing, and as such could be useful for internal use by service + providers. However, such use is beyond the scope of this memo. + Finally, those involved in BGP data analysis are encouraged to verify + with their data sources as to which peers implement this scheme (as + there is a large amount of existing data as well as many legacy + peerings). - The remainder of this document is organized as follows. Section 2 + The remainder of this memo is organized as follows. Section 2 provides both the definition of terms used as well as the semantics of the communities used for BGP data collection, and section 3 defines the corresponding encodings for RFC 1997 [RFC1997] communities. Finally, section 4 defines the encodings for use with extended communities [EXTCOMM]. 2. Definitions In this section, we define the terms used and the categories of routes that may be tagged with communities. This tagging is often - referred to coloring, and we refer to a route's "color" as its + refered to as coloring, and we refer to a route's "color" as its community value. The categories defined here are loosely modeled on those described in [WANG] and [HUSTON]. 2.1. Peers and Peering Consider two network service providers, A and B. Service providers A and B are defined to be peers when (i). A and B exchange routes via BGP, and (ii). traffic exchange between A and B is settlement-free. This arrangement is also typically known as "peering". Peers typically exchange only their respective customer routes (see @@ -192,72 +192,66 @@ This mandates use of regional routing, including community attributes set by the network in question to allow easy discrimination among regional routes. For example, service providers may treat a route set received from another service provider in Europe differently than the same route set received in North America, as it is common practice to sell transit in one region while peering in the other. 3. RFC 1997 Community Encoding and Values In this section we provide RFC 1997 [RFC1997] community values for - the categories described above. RFC 1997 communities encoded as BGP - Type Code 8, and are treated as 32 bit values ranging from 0x0000000 - through 0xFFFFFFF. The values 0x0000000 through 0x0000FFFF and - 0xFFFF0000 through 0xFFFFFFFF are reserved. + the categories described above. RFC 1997 communities are encoded as + BGP Type Code 8, and are treated as 32 bit values ranging from + 0x0000000 through 0xFFFFFFF. The values 0x0000000 through 0x0000FFFF + and 0xFFFF0000 through 0xFFFFFFFF are reserved. The best current practice among service providers is to use the high - order two octets to represent the providers AS number, and the low + order two octets to represent the provider's AS number, and the low order two octets to represent the classification of the route, as depicted below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - where 16 bit AS number. For example, the encoding 0x2A7C029A - would represent the AS 10876 with value 666. + where is the 16 bit AS number. For example, the encoding + 0x2A7C029A would represent the AS 10876 with value 666. 3.1. Community Values for BGP Data Collection In this section we define the RFC 1997 community encoding for the route types described above for use in BGP data collection. It is anticipated that a service provider's internal community values will be converted to these standard values for output to a route collector. - This document follows the best current practice of using the basic - format :. The values for the route categories are - described in the following table: + This memo follows the best current practice of using the basic format + :. The values for the route categories are described in + the following table: Category Value =============================================================== Reserved :0000000000000000 Customer Routes :0000000000000001 Peer Routes :0000000000000010 Internal Routes :0000000000000011 Internal More Specific Routes :0000000000000100 Special Purpose Routes :0000000000000101 Upstream Routes :0000000000000110 Reserved :0000000000000111- :0000011111111111 National and Regional Routes :0000100000000000- :1111111111111111 - Africa (AF) : - Oceania (OC) : - Asia (AS) : - Antarctica (AQ) : - Europe (EU) : - Latin America/Caribbean islands (LAC) : - North America (NA) : - Reserved :0100000000000000- + Encoded as : + Reserved National and Regional values :0100000000000000- :1111111111111111 Where is the 16-bit AS is the 5-bit Region Identifier is the 1-bit satellite link indication X = 1 for satellite links, 0 otherwise is the 10-bit ISO-3166-2 country code @@ -328,24 +322,24 @@ 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x00 | Sub-Type | Global Administrator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Administrator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The two-octet AS specific extended community attribute encodes the service provider's two octet Autonomous System number (as assigned by - an Regional Internet Registry, or RIR) in the Global Administrator + a Regional Internet Registry, or RIR) in the Global Administrator field, and the Local Administrator field may encode any information. - This document assigns Sub-Type 0x05 for BGP data collection, and + This memo assigns Sub-Type 0x05 for BGP data collection, and specifies that the field, as defined in section 3.1, is carried in the low order octets of the Local Administrator field. The two high order octets of the Local Administrator field are reserved, and are set to 0x00 when sending and ignored upon receipt. For example, the extended community encoding for 10876:4338 (representing a terrestrial national route in AS 10876 from the Fiji Islands) would be: 0 1 2 3 @@ -376,68 +370,67 @@ Note that data collection communities have the potential of making the attribute set of a specific route more unique than it would be otherwise (since each route collects data that is specific to it's path inside one or more ASes). This, in turn, can affect whether multiple routes can be grouped in the same BGP update message, and may lead to increased use of bandwidth, router CPU cycles, and memory. 6. Acknowledgments - The community encoding described in this document germinated from an + The community encoding described in this memo germinated from an interesting suggestion from Akira Kato at WIDE. In particular, the idea would be to use the collection community values to select paths that would result in (hopefully) more efficient access to various services. For example, in the case of RFC 3258 [RFC3258] based DNS anycast service, BGP routers may see multiple paths to the same prefix, and others might be coming from the same origin with different paths, but others might be from different region/country (with the same origin AS). Joe Abley, Randy Bush, Sean Donelan, Xenofontas Dimitropoulos, Vijay Gill, John Heasley, Geoff Huston, Steve Huter, Michael Patton, Olivier Marce, Ryan McDowell, Rob Rockell, Rob Thomas, Pekka Savola, Patrick Verkaik and Alex Zinin all made many insightful comments on early versions of this draft. Henk Uijterwaal suggested the use of the ISO-3166-2 country codes. 7. Security Considerations - While this document introduces no additional security considerations - into the BGP protocol, the information contained in the communities - defined in this document may in some cases reveal network structure - that was not previously visible outside the provider's network. As a + While this memo introduces no additional security considerations into + the BGP protocol, the information contained in the communities + defined in this memo may in some cases reveal network structure that + was not previously visible outside the provider's network. As a result, care should be taken when exporting such communities to route collectors. Finally, routes exported to a route collector should also be tagged with the NO_EXPORT community (0xFFFFFF01). 7.1. Total Path Attribute Length - The communities described in this document are intended for use on - egress to a route collector. Hence an operator may choose to - overwrite its internal communities with the values specified in this - document when exporting routes to a route collector. However, - operators should in general ensure that the behavior of their BGP - implementation is well-defined when the addition of an attribute - causes a PDU to exceed 4096 octets. For example, since it is common - practice to use community attributes to implement policy (among other - functionality such as allowing customers to set attributes such as - LOCAL_PREF), the behavior of an implementation when the attribute - space overflows is crucial. Among other behaviors, an implementation - might usurp the intended attribute data or otherwise cause - indeterminate failures. These behaviors can result in unanticipated - community attribute sets, and hence result in unintended policy - implications. + The communities described in this memo are intended for use on egress + to a route collector. Hence an operator may choose to overwrite its + internal communities with the values specified in this memo when + exporting routes to a route collector. However, operators should in + general ensure that the behavior of their BGP implementation is well- + defined when the addition of an attribute causes a PDU to exceed 4096 + octets. For example, since it is common practice to use community + attributes to implement policy (among other functionality such as + allowing customers to set attributes such as LOCAL_PREF), the + behavior of an implementation when the attribute space overflows is + crucial. Among other behaviors, an implementation might usurp the + intended attribute data or otherwise cause indeterminate failures. + These behaviors can result in unanticipated community attribute sets, + and hence result in unintended policy implications. 8. IANA Considerations - This document assigns a new Sub-Type for the AS specific extended + This memo assigns a new Sub-Type for the AS specific extended community type. In particular, the IANA should assign Sub-type 0x05, using the "First Come First Served" policy defined in RFC 2434 [RFC2434], for the Sub-Type defined in Section 4. This corresponds to a Type Field value of 0x0005. 9. References 9.1. Normative References [EXTCOMM] Sangali, S., D. Tappan and Y. Rekhter, "BGP Extended