Most firewalls have a hard time with relating UDP flows, so I don't know if it's a case of Cisco being more or less braindead than other vendors.<div><br></div><div>The other possibility is that the 9971 came from an acquisition or was built as part of a partnership, in which case someone else might have made the "hey, why don't we use TCP!?" decision.</div>
<div><br></div><div>Sean<br><br><div class="gmail_quote">On Wed, Dec 29, 2010 at 12:55 PM, John Lange <span dir="ltr"><<a href="mailto:john@johnlange.ca">john@johnlange.ca</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Sorry to revive a stale thread but I've been doing some work recently<br>
with the Cisco 9971 phone and interestingly this phone is TCP only for<br>
both SIP and RTP.<br>
<br>
Since Microsoft and Cisco are both doing VOIP TCP I'm curious if there<br>
is actually a good reason for this or if it's just a case of the blind<br>
leading the blind?<br>
<br>
As I said previously in this thread, SIP TCP _might_ make some sense<br>
as long as you stripped the state tracking out of the SIP protocol<br>
(which means it wouldn't actually be SIP anymore) but RTP over TCP?<br>
Madness!<br>
<br>
I can think of only two reasons for this:<br>
<br>
a) Microsoft doesn't know jack about SIP/RTP so they wrote it using<br>
TCP because they didn't know any better & Cisco wanted to be<br>
compatible with Microsoft.<br>
<br>
b) Cisco firewalls aren't good at reliably tracking UDP state so they<br>
decided to get around the problem by using TCP.<br>
<br>
If there is actually a good technical reason for voip over TCP I'd<br>
love to hear it.<br>
<font color="#888888"><br>
--<br>
John Lange<br>
<a href="http://www.johnlange.ca" target="_blank">www.johnlange.ca</a><br>
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</font></blockquote></div><br><br clear="all"><br>-- <br>Sean Walberg <<a href="mailto:sean@ertw.com">sean@ertw.com</a>> <a href="http://ertw.com/">http://ertw.com/</a><br>
</div>