ISP Community Usage

RFC 1998 was written several years ago, and since then, ISPs have refined and enhanced what they use communities for. Many examples exist on the Internet, and a few of them that were publicly visible at the time of this writing are documented here.

The first example is from AS 2764, an Australian-based ISP. The community policies are documented in the AS object stored in the Internet Routing Registry:

aut-num:

AS2764

as-name:

ASN-CONNECT-NET

descr:

connect.com.au pty ltd

admin-c:

CC8 9

tech-c:

MP151

remarks:

Community Definition

remarks:

remarks:

2764:

1

Announce to "domestic"

rate ASes only

remarks:

2764:

2

Don't announce outside

local PoP

remarks:

2764:

3

Lower local preference

by 25

remarks:

2764:

4

Lower local preference

by 15

remarks:

2764:

5

Lower local preference

by 5

remarks:

2764:

6

Announce to non customers with "no-export

remarks:

2764:

7

Only announce route to

customers

remarks:

2764:

8

Announce route over satellite link

notify:

[email protected]

changed: [email protected] 19990506

source: CCAIR

The remarks section describes the communities supported. For example, if a customer of AS 2764 sends a prefix with community of 2764:2 set, AS 2764 will announce the prefix only within the local PoP. If a customer sends a prefix with community 2764:8 set, the prefix will be announced only over AS 2764's satellite connection to the United States, and so on.

The second example is from AS 702, a European-based ISP. Its community policies also are documented in its AS object, stored in the Internet Routing Registry:

aut-num:

as-name:

descr:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

remarks:

mnt-by:

changed:

source:

AS7 02 AS702

UUNET - Commercial IP service provider in Europe

UUNET uses the following communities with its customers: 702:80 Set Local Pref 80 within AS702 702:120 Set Local Pref 120 within AS702

702:20 Announce only to UUNET ASes and UUNET customers 702:30 Keep within Europe, don't announce to other UUNET ASs 702:1 Prepend AS702 once at edges of UUNET to Peers 702:2 Prepend AS702 twice at edges of UUNET to Peers 702:3 Prepend AS702 thrice at edges of UUNET to Peers Details of UUNET's peering policy and how to get in touch with UUNET regarding peering policy matters can be found at: http://www.uu.net/peering/

UUNET-MNT

[email protected] 20010928 RIPE

Notice that AS 702 supports one of the RFC 1998 values: 702:80. If that community is attached to a prefix sent to AS 702 by a customer, AS 702 will set the local preference to 80. 702:20 and 702:30 are interesting because they determine boundaries about how far a prefix will be announced within the AS 702 network. Finally, the 702:1, 702:2, and 702:3 communities determine the number of autonomous systems prepended in any announcements that AS 702 makes of customer prefixes to AS 702's peers. This gives customers the option of a primary path to and from AS 702, but they possibly have a backup path through another ISP when they multihome. Or they can use this community to help fine-tune their multihoming load sharing between AS 702 and their other upstream ISPs.

The third example is one of the most comprehensive seen in use in the Internet at this time. An excerpt is given in the following:

aut-num: AS5400

as-name: CIPCORE

descr: Concert European Core Network remarks: Communities scheme:

remarks: The following BGP communities can be set by Concert BGP

remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks: remarks:

customers to affect announcements to major peerings.

Community to Not announce

To peer:

Community to AS prepend 5400

5400:1000 5400:1001 5400:1002 5400:1003 5400:1005 5400:1006 5400:1007 5400:1008 5400:1009 5400:1010

Unisource (AS3300) UUnet (AS7 02) Carrier1 (AS8918) SupportNet (8582) AT&T (AS2 68 6) Level 3 (AS9057) RIPE (AS3333)

European peers

Ebone (AS1755) Eunet (AS286)

5400:2000 5400:2001 5400:2002 5400:2003 5400:2005 5400:2006 5400:2007 5400:2008 5400:2009 5400:2010

remarks: notify: mnt-by: source:

[email protected]

CIP-MNT

RIPE

5400:1100

US peers

5400:2100

Customers of AS 5400 have a large variety of communities available to them, allowing prefix announcements to be made to all of AS 5400's peers and to multihoming load balancing to be determined between AS 5400 and their other upstream ISPs. This model is based on that used by AS 3257, whose detailed community policy is listed at http://www.as3257.net/html/communities.htrr. Although implementing this might seem unduly complicated (it is not that hard, just a very large route map), the benefits for the networks that use this sort of scheme is that their customers have a great deal of liberty when it comes to configuring their multihoming needs.

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