[OT]Re: RTP Was: [vorbis] icecast2

Gregory Maxwell greg at linuxpower.cx
Tue Mar 6 18:05:38 PST 2001



On Tue, Mar 06, 2001 at 08:47:13PM -0500, Marshall Eubanks wrote:
> Gregory Maxwell wrote:
> > 
> > On Tue, Mar 06, 2001 at 07:56:06PM +0100, Smörk wrote:
> > > >Also there were rumors around a while back that icecast2 would support
> > > >rtsp and possibly real. Is there any strength in these rumors?
> > >
> > > I'm not a icecast developer, but I think it's not unlikely that icecast
> > > will support rtp. I don't see a reason why it should support RealMedia
> > > streams? It's more likely, that there is is a Ogg/Vorbis plugin for the
> > > RealPlayer.
> > 
> > 'rtsp' (what the orignal poster said) is in IETF standard (RFC 2326), not
> > just some propritary RealMedia standard. That said, icecast doesn't support
> > it, but most likely because it's overkill.
> > 
> > 'rtp' what you said, is also a IETF standard (1889).. Icecast doesn't do RTP
> > because icecast is unicast (RTP is overkill for unicast and not widely used
> > for that). Vorbis multicast (done by icecast or otherwise) will use RTP.
> 
> RTP is useful for UDP, whether unicast or multicast. Any tcp based streaming
> will be subject to TCP's slow start and congestion control, which causes the
> annoying "rebuffering" of TCP unicast streaming. FWIW we plan to switch
> our unicast streams to RTP/UDP in the near future.

It should be noted that the people responcible for backbone traffic
engineering are becoming progressivly more annoyed with protocols that are
not TCP-compatible (be it games, multimedia, file getters which use a large
number of TCP connections).  The internet can not sustain a sizeable
population of flows which do not at least use effective exponential backoff
without collapse.

For a glimpse of the future, observe what this ALTQ implimentation can do
with buckets judged to be suffcently not-TCP-like
http://www.eecs.umich.edu/~wuchang/blue/ .

Slowstart is obviously stupid for multimedia. But simply dumping congestion
control and avoidance is not an option.

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