Subject: Re: [Sip] MAJOR Open Issue #184: Message size limitations

From: Scott Bradner <[email-masked]>
Date: Fri, 28 Dec 2001 12:11:31 -0500 (EST)

> I would still prefer "MUST" use TCP for packets larger than 1500; your 

anyone who is concerned with reliability or with Internet congestion
should also prefer "MUST use TCP for packets larger than 1500" - it
will be hard to convince the IESG that it is OK for the Internet
to not have this a MUST

Scott

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From: Juha Heinanen <[email-masked]>
Date: Fri, 28 Dec 2001 19:18:51 +0200

> will be hard to convince the IESG that it is OK for the Internet

scott,

i'm wasting too much bandwidth on this, but my point att the time has
been that someone already has convinced IESG not to have MUST there,
because it is SHOULD in rfc2543.  in some other occasions people on this
list have said that iesg requires the bis to be backwards compatible
with rfc2543, but looks like we are now relaxed from that obligation.

-- juha

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From: Juha Heinanen <[email-masked]>
Date: Fri, 28 Dec 2001 22:30:53 +0200

lawrence,

i'm not worried about large message messages, but regular invites, oks,
etc.  all it takes for an invite or ok (that includes an sdp) to exceed
1500 bytes is that the message goes through four proxies that each add
their via and record-route or route headers.

-- juha

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From: Lawrence Conroy <[email-masked]>
Date: Fri, 28 Dec 2001 20:19:17 +0000

>with rfc2543, but looks like we are now relaxed from that obligation.

Don't think so - the difference is that SIP has gained weight since then,
(look at the 3GPP flows in TS 24.228 :) and with SIMPLE, it also gains as
a source of congestion.

IMHO: In summary, SHOULD -> MUST (or use some sunny company's zero loss net :).

And that reminds me...[Flashes of "I told you so" on forehead]
1) There was some concern during PINT finalization that we would be forced to
implement UDP on PINT systems when our messages could be large (and we were
going to use TLS anyway). However, "mainstream" SIP messages would fit into
a single datagram, so we re-implemented to fit. Hey ho...

2) I -knew- there was a reason for SigComp - suggest that anyone who thinks
that they NEED a "standard" SIP message to exceed 1500 octets looks at the
ROHC work; you will end up implementing this sooner or later.

3) Seems to me that including attachments on IM traffic is a major cause of
BIG messages (i.e ones that even SigComp can't fix). We had similar problems
with PINT (see point 1), hence we allowed both "inline" and URL references to
content. If someone wants to include a MP3, why does this need to be inline
in the IM ? -- but that's another list. Reason for mentioning it here is that,
with New Year at hand and everyone promising to diet, we CAN solve the minor
bloat problems and still use UDP. For those cases (i.e. IM) where this won't
suffice, other solutions can be found (see point 2), or we can use TCP or SCTP.
No big deal, as long as we don't add even more poundage to the messages.

all the best,
   Lawrence

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