Subject: [Sip] Connection Reuse and different transports

From: "Paul D.Smith" <[email-masked]>
Date: Tue, 9 Dec 2003 16:11:34 -0000

Rohan,

I have a question regarding Connection Reuse and the selection of a
transport shown in draft-ietf-sip-connect-reuse-00.txt.

The examples of pages 6 and 7 show the registering of an alias address, in
this case through a Via which indicates TLS.  However the examples then go
on to show what happens only when the preferred transport in the reverse
direction is also TLS (alias is used as expected).  But what happens if the
preferred transport in the reverse direction is _not_ TLS, for example if it
is TCP?  Should the alias now be ignored?

Aside: I am studiously ignoring possible issues about "Contact: should be
SIPS etc".  Consider SCTP and TCP as another example.

I suspect that the alias _should_ be ignored and that the registered alias
is actually transport specific so the check for "should I use an alias"
becomes...

if (target server name/address AND target port name AND target transport ALL
match an alias then)
  use the alias
endif

Assuming that I am correct, could you perhaps add a more explicit example to
the next version of the draft?

Thanks,
Paul DS.

Paul D.Smith
Network Protocols Group 
Data Connection Ltd (DCL)
Tel: +44 20 8366 1177  Email: [email-masked] 
Fax: +44 20 8363 1039  Web:   http://www.dataconnection.com

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