I sent the attached message to the routing area discussion list. I thought that people on the IPv6 list might be interested in this discussion, so I will forward a message containing the responses after this one. I suppose I just should have cc:ed the IPv6 group in the first place...
Margaret >Date: Fri, 24 May 2002 12:17:04 -0400 >To: [EMAIL PROTECTED] >From: Margaret Wasserman <[EMAIL PROTECTED]> >Subject: IPv6 Scoped Addresses and Routing Protocols > > > >Hi All, > >I raised some questions with Bill Fenner in Minneapolis regarding IPv6 scoped >addressing and our current IPv6 routing protocol specifications, and Bill suggested >that I should send my questions to this list for discussion. So, here they are. > >First, some background... > >As many of you probably know, IPv6 includes the concept of scoped unicast >addressing -- a unicast address can have link-local scope, site-local scope >or global scope. The address scopes are defined in the IPv6 Addressing >Architecture: > >http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-addr-arch-v3-07.txt > >Additional information can be found in the IPv6 Scoped Address >Architecture: > >http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-scoping-arch-03.txt > >I would suggest that all of you read the IPv6 Scoped Address Architecture >document, if you haven't already, as it contains information regarding >the expected configuration and forwarding behaviour of IPv6 routers. >It also defines the concept of an IPv6 site, which is important to understanding >the questions that I am about to raise. > >In IPv6, there is a concept of site-local addressing that is quite different >from the concept of "net 10" addresses in IPv4. Sites are administratively >defined entities that must be "convex" (i.e. the best route between two nodes >in the site must, at all scopes, fall completely within the site). Sites boundaries >run through routers, so a single router (called a site border router (SBR)) can >have interfaces in more than one site. And, IPv6 site-local addresses can be >used for site-constrained communication, even when a site is globally >connected and global addresses are available. > >Because all site-local addresses use the same well-known site-local prefix, the >only way to tell that a particular site-local address belongs to a particular >site is to know which site originated the address. SBRs will need >to enforce site boundaries, not mixing site-local routing information, and not >forwarding packets outside of a given site. To do this, it is expected that >SBRs will need to maintain multiple "conceptual routing tables", including one >site-local routing table for each attached site, and one global routing table. > >Unfortunately, I can't find any indication that these concepts have been reflected >in the current IPv6 routing protocols. None of our IPv6 routing protocol documents >deal with site-local boundaries or SBR behaviour explicitly. > >There are currently four standards for how IPv6 routes will be handled in BGP, OSPF, >IS-IS and RIP. I will refer to these documents as BGP-IPv6, OSPF-IPv6 and IS-IS-IPv6, >and RIP-IPv6 respectively: > >Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing: >http://www.ietf.org/rfc/rfc2545.txt > >OSPF for IPv6 >http://www.ietf.org/rfc/rfc2740.txt > >Routing IPv6 with IS-IS: >http://www.ietf.org/internet-drafts/draft-ietf-isis-ipv6-02.txt > >RIPng for IPv6 >http://www.ietf.org/rfc/rfc2080.txt > >So here are my actual questions: > >(1) Are the statements regarding the routing system in the IPv6 Scoped Addressing >Architecture >draft valid? Will they work in real life? Please read it, and comment to the IPv6 >WG if you think that >there are any issues with what it says. > >(2) BGP-IPv6: > >BGP-IPv6 states: "As this document makes no assumption on the characteristics of a >particular >routing realm where BGP-4 is used, it makes no distinction between global and >site-local addresses >and refers to both as "global" or "non-link-local"." > >Would it ever be reasonable for BGP to propagate site-local routing information? >Why, under >what circumstances? Would it be reasonable to assume that an Inter-Domain Routing >protocol >shouldn't propagate site-local information at all? > >If BGP should be capable of propagating site-local information, will it be possible, >using existing >BGP standards for a BGP SBR router with four interfaces (A, B, C & D), in two sites >(A & B in S1, >and C & D in S2) to maintain two separate sets of information for prefix FEC0::/10, >one that applies >to S1 (interfaces A & B) and one that applies to S2 (interfaces C & D), and to >propagate that information >accordingly? Is this really just an issue of configuring the router properly, as >BGP-IPv6 implies? > >(3) OSPF-IPV6: > >In this specification, no distinction is made between site-local and global >addresses. Unlike the >previous specification (BGP-IPv6), this assumption is not stated up-front. Instead, >everywhere in >the draft where either site-local or global addresses are mentioned they are both >mentioned (i.e. >"site-local or global IPv6 addresses"). > >Again this specification makes no provision for separate sets of site local >information. There is >also no mention of a boundary for site-local route propagation, and no mention of >multiple conceptual >sets of site-local routing information. Would it make sense to tie the concept of an >IPv6 site to >one of the existing propagation boundaries in OSPF, such as an OSPF area? Or to >assume that >an OSPF AS will always be completely contained within one site -- which is what the >current draft >seems to assume? > >(4) IS-IS-IPv6: > >IS-IS-IPv6 makes no mention of site-local or scoped addressing at all. Is this >appropriate? How will IS-IS >SBRs know not to propagate site-local routing information between two attached sites? > I don't yet >know enough about IS-IS to understand how site-local routing information would best >be handled >in IS-IS. Any thoughts? > >(5) RIP-IPv6: > >The RIP-IPv6 document explicitly states that there is a single IPv6 routing table, >and it makes no >mention of sites. I think it would be fine to constrain RIP to operating within a >single IPv6 >site, but that should be explicitly stated somewhere. > >(6) Will the MIBs for any of these routing tables be capable of representing multiple >independent, >possibly overlapping sets of site-local routing information? I looked them over >quickly, and it >wasn't immediately obvious to me how they could do this. > >(7) Do you think that there would be some utility to defining the actual routing >architecture (as >opposed to just the addressing architecture) for IPv6? If so, what would be the best >way to do >that? > >(8) Should we mention link-local addresses anywhere in these specifications? We >certainly would >not want to propagate routing information for link-local addresses. > >If there is some work that needs to be done here, I am very happy to provide some >IPv6 expertise >to that effort. > >Margaret > > > -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
