On 11 May 2007, at 19:18, Lars Eggert wrote:
On 2007-5-11, at 1:16, ext Colin Perkins wrote:
On 10 May 2007, at 18:36, Lars Eggert wrote:
Section 4.2., paragraph 1:
> The RTP Control Protocol (RTCP) is used in the standard
manner with
> DCCP. RTCP packets are grouped into compound packets, as
described
> in Section 6.1 of [1], and each compound RTCP packet is
transported
> in a single DCCP datagram.
It may be worth pointing out that DCCP imposes MTU restrictions
(Section 14 of RFC4340), which may not be obvious to folks who are
used to RTP over UDP. (To my understanding - and that may be
off - RTP
says nothing much about staying within the MTU, but it has been
recommended in payload specifications.)
The RTP specification talks about this (RFC 3550, section 6.1, top
of page 23), so I don't think anything needs to be added.
To me - and I'm no RTP expert - that text talks about RTCP, i.e.,
the control channel.
Sure, but so does the text in the rtp-over-dccp draft to which you
referred.
Are MTU issues for the data channel discussed in the individual
payload descriptions?
Yes, and in the RFCs providing guidelines for payload format authors.
(In any event, this is probably a corner case, of where someone
wants to migrate an RTP payload format that uses large packets that
require UDP fragmentation over to DCCP, and will be surprised by
DCCP's stricter MTU rules.)
To the best of my knowledge, all the RTP payload formats where this
could conceivably be an issue include application level
fragmentation. We've been aware of MTU issues for a long time in AVT.
Colin
