IETF Corner, March, 2001 - Page 2

 By Pete Loshin
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BGP Confederations and Autonomous Systems

As originally specified, the Border Gateway Protocol (BGP) used for Internet backbone routing requires that all BGP routing entities within a routing domain must be fully-meshed. This poses a serious scalability obstacle as more entities become a part of the domain. Since the mid 1990s, BGP confederations have been used to subdivide the domains, allowing groups of entities to represent themselves as a single BGP entity for routing purposes. An extension to BGP supporting confederations was proposed in experimental RFC 1965, "Autonomous System Confederations for BGP," published in 1996. This month, a new version of this specification was published under the same title as RFC 3065, as a Proposed Standard. The new status reflects the widespread acceptance of BGP confederations by the industry.

Licking Loops

RFC 3063, "MPLS Loop Prevention Mechanism," is an experimental RFC, which can often be interpreted as "trained professionals only: don't try this protocol at home." However, given that this month we saw the advancement of another experimental to the standards track (BGP confederations), it's always wise to stay on top of the research today to see what tomorrow holds. Toshiba and/or Cisco, notes the RFC under the Intellectual Property Considerations section, may at some point seek patent or other intellectual property protection for this mechanism, don't be too surprised if you start seeing it supported in products from those companies. Of course, two of the four authors work for Toshiba and one for Cisco.

MPLS loops can happen when there are transients in routing paths, such that some intermediate switch uses more current switching tables than some oth/er, downstream, switch. The whole point of using MPLS, of course, is to improve performance, so anything that prevents looping within the MPLS domain is a good thing. The authors propose a threading mechanism for MPLS that would differentiate routing threads and associate specific hop counts for each route.

BCP 47: Language Tags

The Internet is a global network, even if many users assume that it's all in English. RFC 3066, "Tags for the Identification of Languages," defines a mechanism by which a client can determine the language, associated character set and any other related information, necessary to identify and decode language content in an information object. Also published as BCP 47, this document obsoletes RFC 1766 of the same title, which was published six years ago as a Proposed Standard.

This type of specification may not necessarily reflect clever engineering so much as agreement on the standards for representing different languages and character sets. Interoperability in this case depends on everyone agreeing to use the same authorities for denoting languages, with the same syntax. BCP 47 can be applied to any kind of content with an RFC 822-style header (such as email or news postings), web pages, or MIME objects.

What's Next

This will be my last IETF Corner column for CrossNodes, although my IETF-oriented columns in other publications will continue. I've been grateful for the opportunity to write this column, and especially for all the readers who've supported it. Thank you.

Pete Loshin is author of 24 books and frequently consults on Internet standards issues; he can be reached at pete@Internet-Standard.com.

This article was originally published on Mar 13, 2001
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