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

From: Juha Heinanen <[email-masked]>
Date: Fri, 28 Dec 2001 10:18:15 +0200

i have nothing against introducing an error response for truncated UDP
messages, but whatever the new spec will say should not make existing
implementations that support large udp packets non-compliant.

i have in active use half a dozen different sip phone, proxies and media
gateway controllers and all of them today send and receive sip messages
in udp packets that are larger than 1500 bytes.  their network driver
simply ip fragments and reassembles a packet if it doesn't fit into a
1500 byte ethernet frame.  almost a year ago i found one ip phone that
didn't support reception of framented udp packets, but that was promptly
fixed, when i reported the issue.

if the new version of the spec will say (as jonathan suggested) "if the
request is larger than 1500 bytes, you MUST use TCP to send it", then
such a statement would make all off-the-shelf sip entities that are
currently in use in my network non-compliant, which would be a VERY bad
idea.

-- juha

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From: "Jari Arkko" <[email-masked]>
Date: Fri, 28 Dec 2001 10:39:25 +0200

> currently in use in my network non-compliant, which would be a VERY bad

Yeah. How about "SHOULD use TCP if the sent request is larger than A
bytes, MAY return an error code if the received request is larger than B
bytes."  Here B >= A, e.g. A=B=1500 or A=1500, B=5000.

Jari