[opendtv] Re: 5th gen receivers
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 23 Jan 2005 19:00:05 -0500
Manfredi, Albert E wrote:
> The advantage of IP multicast is that fat streams are
> used by many destinations, instead of just one. The
> disadvantage is that the network becomes a lot
> smarter than it would have to be to support unicast
> flows. There's no free lunch. That super dumb source
> has to be balanced by smarts elsewhere.
Yep. But increasingly the smarts ARE everywhere, especially in P2P. I
am not a multcast expert but it seemed there could be some useful things
done to take advantage of its existance in the P2P world if end users
could multicast.
- Tom
> Tom Barry wrote:
>
>
>>Why must someone have only one peer? What do you
>>call getting a file from BitTorrent where it comes
>>from multiple P2P sources?
>
>
> You're right about bit torrent. A host has multiple
> peers, and downloads segments of the whole file from
> different sources. The server involved is only there
> to do the choreography. This is unicast, though.
> Each session is a unicast session. The advantage is
> that downloads are distributed among many source
> hosts, which prevents server congestion.
>
> With multicast, instead, there is no concept of
> sessions between sources and destinations. Each
> destination host only ever signals back and forth to
> the edge router of the network. Destinations express
> their desires to edge routers, edge routers in turn
> communicate with core routers in the network to build
> and tear down multicast trees. And the sources are
> oblivious to absolutely everything that's going on.
> They just transmit their bit streams.
>
> The advantage of IP multicast is that fat streams are
> used by many destinations, instead of just one. The
> disadvantage is that the network becomes a lot
> smarter than it would have to be to support unicast
> flows. There's no free lunch. That super dumb source
> has to be balanced by smarts elsewhere.
>
> Bert
>
>
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