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INTERNET-DRAFT D. Meyer
draft-ietf-grow-collection-communities-00.txt
Category Best Current Practice
Expires: June 2004 December 2003
BGP Communities for Data Collection
<draft-ietf-grow-collection-communities-00.txt>
Status of this Document
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use 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
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The key words "MUST"", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC 2119].
This document is a product of the GROW WG. Comments should be
addressed to the authors, or the mailing list at
grow@lists.uoregon.edu.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
D. Meyer [Page 1]
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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
standard (outbound) communities and their encodings for export to BGP
route collectors.
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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
2.4. Internal Routes . . . . . . . . . . . . . . . . . . . . . . 5
2.5. Internal More Specific Routes . . . . . . . . . . . . . . . 5
2.6. Special Purpose Routes. . . . . . . . . . . . . . . . . . . 6
2.7. Upstream Routes . . . . . . . . . . . . . . . . . . . . . . 6
2.8. National Routes . . . . . . . . . . . . . . . . . . . . . . 6
2.9. Regional Routes . . . . . . . . . . . . . . . . . . . . . . 6
3. RFC 1997 Community Encoding and Values . . . . . . . . . . . . 7
3.1. Community Values for BGP Data Collection. . . . . . . . . . 7
4. Extended Communities . . . . . . . . . . . . . . . . . . . . . 8
5. Intellectual Property. . . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations. . . . . . . . . . . . . . . . . . . . 11
7.1. Total Path Attribute Length . . . . . . . . . . . . . . . . 11
8. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References. . . . . . . . . . . . . . . . . . . . 12
9.2. Informative References. . . . . . . . . . . . . . . . . . . 12
10. Author's Addresses. . . . . . . . . . . . . . . . . . . . . . 13
11. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 13
D. Meyer [Page 3]
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1. Introduction
BGP communities [RFC1997] 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 providers network, and to
it's customers and peers. Communities are also used for a wide
variety of other applications, such as allowing customers to set
attributes 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 are
not (necessarily) intended for internal use by service providers.
Rather, they are meant to mirror the information that many service
providers carry today, and to be a standardized representation of
that information.
The remainder of this document 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
community value. The categories defined here are loosely modeled on
those described in [WANG] and [HUSTON].
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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 known as "peering". Peers typically exchange
only their respective customer routes (see "Customer Routes" below),
and hence exchange only their respective customer traffic. See
[HUSTON] for a more in-depth discussion of the business models
surrounding peers and peering.
2.2. Customer Routes
Customer routes are those routes which are heard from a customer via
BGP and are propagated to peers and other customers. Note that a
customer can be an enterprise or another network service provider.
These routes are sometimes called client routes [HUSTON].
2.3. Peer Routes
Peer routes are those routes heard from peers via BGP, and not
propagated to other peers. In particular, these routes are only
propagated to the service provider's customers.
2.4. Internal Routes
Internal routes are those routes that a service provider originates
and passes to its peers and customers. These routes are frequently
taken out of the address space allocated to a provider.
2.5. Internal More Specific Routes
Internal more specific routes are those routes which are frequently
used for circuit balancing purposes, IGP route reduction, and also
may correspond to customer services which are not visible outside the
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service provider's network. Internal more specific routes are not
exported to any external peer.
2.6. Special Purpose Routes
Special purpose routes are those routes which do not fall into any of
the other classes described here. In those cases in which such routes
need to be distinguished, a service provider may color such routes
with a unique value. Examples of special purpose routes include
anycast routes, and routes for overlay networks.
2.7. Upstream Routes
Upstream routes are typically learned from upstream service provider
as part of a transit service contract executed with the upstream
provider.
2.8. National Routes
These are route sets that are sourced from and/or received within a
particular country.
2.9. Regional Routes
Several global backbones implement regional policy based on their
deployed footprint, and on strategic and business imperatives.
Service providers often have settlement free interconnections with an
AS in one region, and that same AS is a customer in another region.
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.
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3. RFC 1997 Community Encoding and Values
In this section we provide standardized 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 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| <AS> | <Value> |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where <AS> 16 bit AS number, and <Value> is the encoding of the
value. 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 <AS>:<Value>. The values for the route categories are
described in the following table:
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Category Value
===============================================================
Customer Routes <AS>:64500
Peer Routes <AS>:64510
Internal Routes <AS>:64520
Internal More Specific Routes <AS>:64530
Special Purpose Routes <AS>:64540
Upstream Routes <AS>:64550
Reserved <AS>:64551-65535
National and Regional Routes
Africa (AF) <AS>:0<CC>
Asia/Australia/Pacific (AP) <AS>:1<CC>
Antarctica (AQ) <AS>:2<CC>
Europe (EU) <AS>:3<CC>
Latin America/Caribbean islands (LAC) <AS>:4<CC>
North America (NA) <AS>:5<CC>
In the above table, the <CC> field contains the ISO-3166-2 encoding
of the country code [ISO-3166-2,RIS-ISO-3166], which is right-
justified (i.e., left zero-padded) in the <CC> field. For example,
the community 10876:10242 would represent a national route in AS
10876 from the Fiji Islands, since the Fiji Islands are in the AP
region (Region Code 1) and have ISO-3166-2 numeric country code 242.
That is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x2A7C | 0x2802 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Finally, note that these categories are not intended to be mutually
exclusive, and multiple communities can be attached where
appropriate.
4. Extended Communities
In some cases, the encoding described in section 3.1 may clash with a
service provider's existing community assignments. Extended
communities [EXTCOMM] provide a convenient mechanism that can be used
to avoid such clashes.
The Extended Communities Attribute is a transitive optional BGP
attribute with the Type Code 16, and consists of a set of extended
communities of the following format:
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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 high | Type low(*) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Value |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For purposes of BGP data collection, we encode the communities
described in section 3.1 using the two-octet AS specific extended
community type, which has the following 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 assigned by
IANA 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
specifies that the <Value> 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 10876:10242
(representing a national route in AS 10876 from the Fiji Islands)
would be:
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 | 0x05 | 0x2A7C |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00 | 0x00 | 0x2802 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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5. Intellectual Property
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11 [RFC2028].
Copies of claims of rights made available for publication and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementors or users of this
specification can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
6. Acknowledgments
Joe Abley, Randy Bush, Sean Donelan, Xenofontas Dimitropoulos, Vijay
Gill, John Heasley, Geoff Huston, Steve Huter, Olivier Marce, Ryan
McDowell, Rob Rockell, Rob Thomas, and Patrick Verkaik all made many
insightful comments on early versions of this draft. Henk Uijterwaal
suggested the use of the ISO-3166-2 country codes.
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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
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.
8. IANA Considerations
This document 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.
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9. References
9.1. Normative References
[EXTCOMM] Sangali, S., D. Tappan and Y. Rekhter, "BGP
Extended Communities Attribute",
draft-ietf-idr-bgp-ext-communities-06.txt,
Work in Progress.
[HOUSTON] Huston, G., "Interconnection, Peering, and
Settlements",
http://www.isoc.org/inet99/proceedings/1e/1e_1.htm
[ISO-3166-2] http://www.iso.org/iso/en/prods-services/iso3166ma/index.html
[RIS] "Routing Information Service", http://www.ripe.net/ris
[RIS-ISO-3166] ftp://ftp.ripe.net/iso3166-countrycodes.txt
[ROUTEVIEWS] "The Routeviews Project", http://www.routeviews.org
[RFC1771] Rekhter, Y., and T. Li (Editors), "A Border
Gateway Protocol (BGP-4)", RFC 1771, March,
1995.
[RFC1997] Chandra, R. and P. Traina, "BGP Communities
Attribute", RFC 1997, August, 1996.
[VLPS] Kompella, K., et. al., "Virtual Private LAN
Service", draft-ietf-l2vpn-vpls-bgp-00.txt,
Work in Progress.
[WANG] Wang, F. and L. Gao, "Inferring and Characterizing
Internet Routing Policies", ACM SIGCOMM Internet
Measurement Conference 2003.
9.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", RFC 2119, March,
1997.
[RFC2026] Bradner, S., "The Internet Standards Process --
Revision 3", RFC 2026/BCP 9, October, 1996.
D. Meyer Section 9.2. [Page 12]
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[RFC2028] Hovey, R. and S. Bradner, "The Organizations
Involved in the IETF Standards Process", RFC
2028/BCP 11, October, 1996.
[RFC2434] Narten, T., and H. Alvestrand, "Guidelines for
Writing an IANA Considerations Section in RFCs",
RFC 2434/BCP 26, October 1998.
10. Author's Addresses
D. Meyer
Email: dmm@1-4-5.net
11. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
D. Meyer Section 11. [Page 13]
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D. Meyer Section 11. [Page 14]
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