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2. call-leg ID lookups in gateways are much faster now, since the tags
and
call-ids are just strings. Matching is now case-sensitive string
compares.
Much easier than URL comparison.=20
3. Overlap dialing is easier. The reason we've had to send each digit as
a
new call leg, is that we needed to change the To field and the request
URI.
By definition, this meant a new call leg. Now, we can send all of that
within a single call leg. Much cleaner.
4. The Replaces draft benefits. We've already identified a need for the
Replaces header to identify the entire call leg thats being replaced.
This
gets big when it carries two URLs, two tags, and a call-id. Now, we can
throw away the URLs. This shortens the header and makes matching of the
call-leg IDs easier.
5. It works with existing proxies.
THe main drawback, of course, is that this won't interoperate with
rfc2543
UAs. Thats fixable with Supported; the UAC indicates Supported:
new-call-leg-id in the INVITE if it understands this. In that case, any
responses or re-invites that change the URLs include a Require:
new-call-leg-id.=20
I fully admit that this may not be worth the pain. However, I'd welcome
comments from others on whether its useful to consider further.
-Jonathan R.
---
Jonathan D. Rosenberg, Ph.D. 72 Eagle Rock Ave.
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
jdrosen@dynamicsoft.com FAX: (973) 952-5050
http://www.jdrosen.net PHONE: (973) 952-5000
http://www.dynamicsoft.com
=20
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<TITLE>RE: [Sip] another modest proposal: change call-leg ID</TITLE>
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<P><FONT SIZE=3D2>Jonathan-</FONT>
</P>
<P><FONT SIZE=3D2>Would your proposal in any way enable a rogue endpoint =
to alter or take over a session by replicating a valid set of Call-ID =
and tags? </FONT></P>
<P><FONT SIZE=3D2>--Andy Zmolek</FONT>
<BR><FONT SIZE=3D2> Technology & Standards =
Engineer</FONT>
<BR><FONT SIZE=3D2> CTO Standards</FONT>
<BR><FONT SIZE=3D2> Avaya =
Inc.</FONT>
</P>
<P><FONT =
SIZE=3D2> &nbs=
p; zmolek@avaya.com</FONT>
<BR><FONT =
SIZE=3D2> &nbs=
p; +1 720 444 4001</FONT>
</P>
<BR>
<P><FONT SIZE=3D2>-----Original Message-----</FONT>
<BR><FONT SIZE=3D2>From: Jonathan Rosenberg [<A =
HREF=3D"mailto:jdrosen@dynamicsoft.com">mailto:jdrosen@dynamicsoft.com</A=
>]</FONT>
<BR><FONT SIZE=3D2>Sent: Wednesday, July 11, 2001 12:30 AM</FONT>
<BR><FONT SIZE=3D2>To: 'sip@ietf.org'</FONT>
<BR><FONT SIZE=3D2>Subject: [Sip] another modest proposal: change =
call-leg ID</FONT>
</P>
<BR>
<P><FONT SIZE=3D2>Folks,</FONT>
</P>
<P><FONT SIZE=3D2>While we're on the subject of modest proposals, here =
is another that I've</FONT>
<BR><FONT SIZE=3D2>been toying with:</FONT>
</P>
<P><FONT SIZE=3D2> Change the definition of call-leg ID. Instead =
of To, To-tag, From,</FONT>
<BR><FONT SIZE=3D2> From-tag, and Call-ID, its *only* the tags and =
the Call-ID. That is,</FONT>
<BR><FONT SIZE=3D2> the ID no longer contains the URLs.</FONT>
</P>
<P><FONT SIZE=3D2>There are quite a few benefits from this:</FONT>
</P>
<P><FONT SIZE=3D2>1. A calls B, and its forwarded to C. C accepts, and =
later re-INVITEs. The</FONT>
<BR><FONT SIZE=3D2>From field in this re-INVITE is NOT actually the =
identity of C, but rather,</FONT>
<BR><FONT SIZE=3D2>B. This screws up the idempotency of SIP INVITE. The =