[opendtv] Re: IPTV on AP: Interactive TV Poised for a Rollout (Feb 13)
- From: Kon Wilms <kon@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 17 Feb 2005 09:31:12 -0800
On Thu, 2005-02-17 at 08:04 -0500, Craig Birkmaier wrote:
> In the example I cited, several homes are viewing a VOD program that
> is being delivered via a multicast, as opposed to individual unicasts
> to each home. If one home hits pause, does the program pause for
> every other home on that multicast? I think not.
You missed my point. You're equating single one-on-one sessions with
unicast delivery. One-on-one sessions can also be delivered via
multicast. As can the one to many sessions. My point is that it is more
advantageous from a robustness and server load point of view to simply
deliver everything as multicast.
In terms of what a server can dish out, it is easier to multicast than
unicast. The server doesn't have constant ACK/NACKs being received, it
doesn't have to keep the endpoint socket connection up, and needs no
mechanism to re-establish connections if the client drops out. In effect
your servers become simple playout pumps.
Ofcourse one needs an OOB server interface to communicate with the
clients, which initiates and cuts transmission of multicast data (one to
one or one to many) and can also handle session initiation -- but one
needs that anyway. You don't even need to handle pausing as with a
unicast connection, the network can do it for you. Or you can do it OOB.
Another advantage is if a segment of your network goes down, no socket
connections are broken. So recovery is made simpler too.
Cheers
Kon
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