Subject: [MMUSIC] draft-ietf-mmusic-ice-12: questions on ICE's local preference and rfc 3484's source address selection algorithm

From: "Jean-Francois Mule" <[email-masked]>
Date: Mon, 30 Oct 2006 09:35:03 -0700

Jonathan,

   In section 5.2 of ice-12, the second paragraph on page 19 has some
considerations on the selection of (local) preferences based on the IP
address family (Ipv6, IPv4).
   While ice defines an application level mechanisms for choosing
between candidates for valid connectivity, RFC 3484 defines a default
source/destination address selection algorithm for IPv6 nodes (in cases
where there is no guidance provided by the application layer). 

--- Questions:
1. Would it be appropriate to somehow link the precedence of the policy
table in 3484 with the local preference of ICE when both IPv4 and IPv6
candidates are present, and a policy table does exist?
What got me to go back to 3484 is the second sentence of that second
paragraph on page 19 of ice-12 on how connectivity checks over IPv6
might be preferred over IPv4 ones; see section 10.3 of 3484 - there
seems to be some parallels at a first sight.

2. Would it be useful to mention RFC 3484 in ICE and discuss how it
may/should be used in dual-stack hosts to derive the local preference of
particular candidate?

Jean-Francois.

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 30 Oct 2006 13:51:20 -0500

These are some good questions.

To be frank I was not familiar with RFC3484 until you pointed it out. It 
is very much solving the same kind of problem, but it makes a much 
different assumption. It assumes that the source selection algorithm has 
the destination address as an input. In ICE, we don't know the 
destination until after we've signaled the priority for the source 
addresses.

Consequently, it was non-obvious to me how to just reference RFC 3484 or 
use any of its algorithms without some major tweaking. Indeed I would go 
so far as to say that RFC 3484 is almost inapplicable because of this 
difference.

Perhaps you can suggest some words that do make sense?

Thanks,
Jonathan R.

-- 
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