Re: [lisp] [ipdir] LISP WG: Loc/ID separation - not separate namespaces
Robin Whittle <rw@firstpr.com.au> Wed, 18 March 2009 00:55 UTC
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From: Robin Whittle <rw@firstpr.com.au>
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Cc: ipdir@ietf.org, Noel Chiappa <jnc@mercury.lcs.mit.edu>, iesg@ietf.org
Subject: Re: [lisp] [ipdir] LISP WG: Loc/ID separation - not separate namespaces
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(I am replying to Noel's "Re: [lisp] [ipdir] LISP WG" message.) Short version: Neither LISP nor any of the other core-edge separation approaches to the routing and addressing scaling problem involve separate namespaces for "locators" and "identifiers". The nature of the "split" is operational. While the proposed LISP charter does not mention namespaces, there is a danger that without clarification, the erroneous notion of separate namespaces in LISP etc. will be propagated. This is especially the case since several LISP-ALT documents explicitly claim that there are separate namespaces. I raised this critique in March 2008 and still people are mentioning separate namespaces for EIDs and RLOCs as if this is an accepted truth. Noel wrote, in part: >> From: Margaret Wasserman <mrw@lilacglade.org> > >> I am concerned about the accuracy of calling this mechanism an >> ID/Locator split mechanism > > Well, if it is not intended to separate location and identity, what's the > point of creating a mapping database, to maintain maps from one namespace to > another? In LISP, RLOC addresses and EID addresses are not in separate namespaces. Assuming IPv4 for the discussion, both RLOC and EID addresses are within the 32 bit IPv4 namespace. I am unable to find an authoritative definition of the term "namespace" but these strike me as pretty good: http://en.wiktionary.org/wiki/namespace (computing) A conceptual space that groups classes, identifiers, etc. to avoid conflicts with items in unrelated code that have the same names. http://en.wikipedia.org/wiki/Namespace ... an abstract container providing context for the items (names, or technical terms, or words) it holds and allowing disambiguation of items having the same name (residing in different namespaces). ... The "split" referred to in LISP's name involves classifying some IPv4 addresses into "EID" addresses and others (the remainder?) into "RLOC" addresses. I think this is fine, but I agree with the critique that other approaches, such as HIP, have a stronger claim to being a system which truly splits Locator and Identifier addresses. LISP's "split" is an operational matter. An ITR will recognise some addresses as being RLOCs and others as EIDs. (Ordinary routers or hosts need make no such distinctions.) EIDs and RLOCs are still within the single IPv4 namespace. Arguably, a true split would be a conceptual one - which HIP certainly does - into two separate namespaces for RLOC and EID addresses. In principle, it would be possible for both RLOC and EID addresses to be in separate namespaces while both being 32 bit integers. However, then each such address would need to come with sufficient context for the device to know which namespace to interpret these bits within. If IPv4 LISP really had separate namespaces for EID and RLOC, then the number 1.2.3.4 would mean one thing in the EID namespace and another in the RLOC namespace. It is probably too late to change LISP's name. However, I think there should be a truth in labelling notice in all LISP documents that the "split" referred to is an operational matter within the IPvN namespace, and not the creation of two separate namespaces. Furthermore, I think it would be good to note that HIP and I guess other proposals really do split addressing into two separate namespaces for identifier and locator. Below my signature are some links to prominent items which appear when searching for: LISP split EID RLOC namespace These include some I-Ds and other material from the LISP-ALT team which erroneously state that LISP involves two separate namespaces. - Robin http://www.firstpr.com.au/ip/ivip/ http://www.google.com/search?hl=en&as_q=LISP+split+EID+RLOC+namespace LISP documents referring to 2 namespaces ---------------------------------------- http://tools.ietf.org/html/draft-farinacci-lisp-12 Another approach is to have the ITR not encapsulate a multicast packet and allow the the host built packet to flow into the core even if the source address is allocated out of the EID namespace. http://tools.ietf.org/html/draft-lewis-lisp-interworking-02 EID Sub Namespace: A power-of-two block of aggregatable locators set aside for LISP interworking. PTRs (Proxy Tunnel Routers) attract traffic by announcing the LISP EID namespace into parts of the non-LISP-speaking global routing system. http://www.isoc.org/tools/blogs/ietfjournal/?p=158 http://www.isoc.org/tools/blogs/ietfjournal/wp-content/uploads/2007/10/IETFJournal0302.pdf IETF Journal Vol 3 Issue 2 2007-10 David Meyer Most of the existing routing and addressing proposals leverage the one or more levels of indirection inherent in the ID/Locator separation idea to create one or more new namespaces. In most cases, two namespaces are utilised. One namespace-the End-point Identifiers (or EIDs)-is used to address hosts. The other space, known as Routing Locators (or RLOCs), is used for packet routing across a transit domain. http://www.nanog.org/mtg-0710/presentations/LISP-cons.pdf What is LISP? * Locator/ID Separation Protocol (LISP) – draft-farinacci-lisp-03.txt * Creates two namespaces: IDs and Locators ... Mailing list message from LISP-ALT team referring to 2 namespaces ------------------------------------------------------------------- http://www.ietf.org/mail-archive/web/rrg/current/msg01293.html Dino: Well an EID/RLOC split adds one new namespace to address systems out of. That gives you more addresses on the order of the total addressable address space of the namespace's address family (IPv4 or IPv6). You could iterate to build multiple levels of hierarchy. Just like people have done with multi-level NAT. Critiques of the notion that LISP provides separate namespaces -------------------------------------------------------------- None of the three core-edge separation techniques which are documented in I-Ds provide separate namespaces for "locators" and "identifiers": http://www.lisp4.net http://tools.ietf.org/html/draft-jen-apt-01 http://www.firstpr.com.au/ip/ivip/ This question of namespaces has been discussed before, including: http://www.ops.ietf.org/lists/rrg/2008/msg00797.html RW 2008-03-16 Hi Tony (Li), You wrote, in part: > We've also accepted as axiomatic that we would like to separate > this functionality into two independent namespaces. I want to > stress here that for the architectural result to be in any way > clean, independence is mandatory. Any linkage whatsoever would > be a clearly suboptimal result. ... I don't think any of the map-encap approaches - LISP, APT, Ivip or TRRP - involves the creation of a completely independent namespace. I can't imagine any incrementally deployable solution which would. (Tony's response strikes me as quite abstract and doesn't really tackle the critique that for LISP etc. these are not separate namespaces: http://www.ops.ietf.org/lists/rrg/2008/msg00817.html) http://www.ops.ietf.org/lists/rrg/2008/msg00829.html RW 2008-03-18 [On "jack-down" models - independent namespaces] http://www.ops.ietf.org/lists/rrg/2008/msg01637.html RW 2008-06-27 [Not separate namespaces: Loc-ID-separation, map-encap etc.]
- Re: [lisp] [ipdir] LISP WG Margaret Wasserman
- Re: [lisp] [ipdir] LISP WG Templin, Fred L
- Re: [lisp] [ipdir] LISP WG Sam Hartman
- Re: [lisp] [ipdir] LISP WG Noel Chiappa
- Re: [lisp] [ipdir] LISP WG Templin, Fred L
- Re: [lisp] [ipdir] LISP WG Scott Brim
- Re: [lisp] [ipdir] LISP WG Noel Chiappa
- Re: [lisp] [ipdir] LISP WG: Loc/ID separation - n… Robin Whittle