RE: [Sip] Extension to Assure Congestion Safety

["Dean Willis" <dean.willis@softarmor.com>]

> 
> Dean, where are you found datas and information on 3G network delay?
> 

Primarily from presentations to the 3GPP-IETF joint meeting last week in San
Francisco, plus my own experience with a couple of CDMA 2000 1XRTT networks,
as well was with GRPS over GSM TDMA  (which, despite some marketing
programs, isn't really 3G). 

Don't get me wrong -- there are plenty of potential sources of delay here.
But properly used TCP really isn't a major contributor.

There's a large body of work out there. I suggest starting with RFC 2757

ftp://ftp.rfc-editor.org/in-notes/rfc2757.txt


And I'd like to point out ongoing work (just a tiny subset of what's going
on).

http://www.ietf.org/internet-drafts/draft-ietf-pilc-2.5g3g-12.txt

http://www.ietf.org/internet-drafts/draft-sarolahti-tsvwg-tcp-frto-03.txt

http://www.ietf.org/internet-drafts/draft-amit-quick-start-02.txt

http://www.ietf.org/internet-drafts/draft-ludwig-tsvwg-tcp-fast-timeouts-00.
txt

http://www.ietf.org/internet-drafts/draft-gurtov-tsvwg-tcp-delay-spikes-01.t
xt

http://www.ietf.org/internet-drafts/draft-ietf-rohc-tcp-03.txt

The basic point is that there is a tremendous amount of effort going into
understanding and improving TCP's behaviour over wireless networks, and
trying to re-invent all of that here for SIP/UDP is sheer folly. Sure, UDP
is potentially useful, especially for lightweight mobile-to-first-hop-server
links, but probably just dangerous and pointless for server-server links. I
propose that we DO NOT need to "fix" this in SIP -- we just need to limit
the usage so that UDP is only used in the non-dangerous cases. This
shouldn't be all that hard to do.

--
Dean

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