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Re: IPv6 news

  • From: John Reilly
  • Date: Sun Oct 16 13:27:14 2005

On Sun, 2005-10-16 at 11:08 -0400, Joe Abley wrote:
> > Am I mistaken in thinking that if shim6 (or something like it) did
> > exist, that portable address space could be allocated to everyone  
> > (maybe
> > with a different allocation policy?) to be used as (shim6)  
> > identifiers.
> Yes, you're mistaken. The locator identifier is chosen from the  
> host's pool of upper-layer identifiers.

Sorry, maybe I wasn't clear when I said identifier - I meant endpoint
identity (ULID) not locator.

I had read a portion (most of the first 3 sections) of draft-ietf-shim6-
arch-00.txt to try and get the main concepts.  Just so I get it
straight, as I've read it, there are ULIDs (which I mistakenly called
identifiers in my previous posts), and there are locators (which are
real routable IP addresses).  

>From section 3:
   "There are a number of options in the choice of an endpoint identity
   realm, including the use of existing addresses as an identity tokens,
   the use of distinguished (possibly non-routeable) addresses as
   tokens, or the use of tokens drawn from a different realm (such as
   use of a fully qualified domain name).

   Shim6 uses the first of these options, and the endpoint identity for
   a host is one of the locator addresses that are normally associated
   with the host.  The particular locator address selected to be the
   endpoint identity (or ULID) is specified in [RFC3484].  Shim6 does
   not mandate the use of distinguished addresses as identities,
   although the use non-routeable distinguished addresses in this
   context is described as an option in this approach."

So currently, shim6 will always use a routable IP address (one of the
locators) as the ULID, but it seemed to leave the option open for non-
routable addresses to be used.  Therefore, my conclusion that a portable
(but non-routed) address might be used.  


And now, after reading the rest of the draft, I see that use of non-
routable addresses has only been explored at an abstract level.
Obviously the null tranform for ULID->locator wouldn't work when
establishing a session if the ULID was non-routable. 

One comment/question and I know this is probably the wrong forum, but in
section 4.1 there is a question "What form of token is passed to the IP
layer from the upper level protocol element as an identification of the
remote session target?". As part of the answer, it says "If the initial
identification of the remote host is via a domain name, then this
approach assumes that there are a one or more locators held in the

Should that not read that "there are one or more ULIDs held in DNS"?
Although in practice, it seems that the set of ULIDs and locators will
probably be the same (although not always?) so it probably won't matter