Subject: [NSIS] closing GIST issue 61 (interface-address selection in NLI)

From: "Hancock, Robert" <[email-masked]>
Date: Thu, 1 Sep 2005 16:13:40 +0100

Dear all,

During the interop, the message format torture testing uncovered
some potential freedom in address selection. Some of this freedom
is possibly dangerous (the particular case was a v6 signalling
address with a v4 flow, but there are also other possibilities.
See also:

http://nsis.srmr.co.uk/cgi-bin/roundup.cgi/nsis-ntlp-issues/issue61

The text in section 5.2.2 has been revised, hopefully to make it
clearer what implementors ought to do but also what is possible
for them to do. The particular paragraph is now:

      The interface-address must be routable, i.e. it MUST be usable as
      a destination IP address for packets to be sent back to the node
      generating the signalling message (whether in datagram or
      connection mode).  Where this object is carried in a GIST-Query or
      GIST-Confirm, the interface-address MUST specifically be set to an
      address bound to the interface associated with the MRI (e.g. the
      one carrying the outbound flow), to allow its use in route change
      handling, see Section 7.1.  A node may have several choices for
      which of its addresses to use as the interface-address.  For
      example, there may be a choice of IP versions, or addresses of
      limited scope (e.g. link-local), or addresses bound to different
      interfaces in the case of a router or multi-homed host.  However,
      some of these choices of interface address may not be usable by
      the peer.  A node SHOULD follow a default policy of using a global
      address of the same IP version as in the MRI, unless it can
      establish in advance that an alternative address would also be
usable.

Comments?

robert h.

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