[xiph-rtp] Interesting post on AVT list
dbarrett at quinthar.com
Tue Sep 6 15:40:52 PDT 2005
Tor-Einar Jarnbjo wrote:
> Luca Barbato wrote:
>> Which method would deliver the SDP unreliably?
> RTSP and SIP, isn't that what we're talking about? Both methods usually
> use UDP transport.
Well, TCP is only reliable because it layers retransmissions atop IP.
SIP is likewise reliable because it layers retransmissions atop UDP.
So SDP is delivered reliably by SIP, because SIP has reliability built
Regardless, sending any SIP packet using UDP bigger than the MTU will
probably still fail despite SIP's reliability measures because SIP has
no fragmentation ability (that I know of -- can anyone correct me
here?), and fragmented UDP is sometimes blocked by
NATs/routers/firewalls. That's why SIP states anything over the MTU
should be delivered using TCP.
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