Tappit Hen <tappit.hen@xxxxxxxxx> espoused:
> On Thu, 03 Jan 2008 07:59:00 +0000, Mark Kent wrote:
>
>> Roy Schestowitz <newsgroups@xxxxxxxxxxxxxxx> espoused:
>>> ____/ Mark Kent on Tuesday 01 January 2008 15:06 : \____
>>>
>>>> Buffering can't make up for a connection which is too slow, though
>>>> - but as you say, the flash video format works well under even
>>>> heavy congestion.
>>>
>>> You can watch it in lumps though (pause instead of jitter). You
>>> can't do that with a complete download.
>>>
>>
>> True, but with normal connectionless packet networks, you have no
>> idea how long the next "lump" will take to come down, so it's not a
>> particularly satisfactory way of doing things.
>>
>> You can see this behaviour quite often on eg., Youtube, when
>> sometimes videos will play fine, but at other times, they get
>> choppy, and randomly pause and resume. This is an inevitable
>> consequence of connectionless packet networks. It can be solved, of
>> course, by setting up connections, but so long as we have huge
>> swathes of router manufacturers with products to push, this issue is
>> not going to be "accepted".
>
> Ahem, youtube uses tcp. If your player uses buffering then it works
> great unless you have a really shitty connection.
You cannot have connections on IP, IP is a connectionless protocol. It
doesn't matter what you try to do /on top/ of a connectionless protocol.
Think about it - you *will* lose packets.
tcp tries to get around this by operating and ack/nack approach,
however, this is *not effective* in real-time streaming, since it
causes pauses, which means that you are no longer real-time. The only
workable solution is to have a connection-oriented network at the
transport layer, which IP is not.
> I never have a
> problem with youtube and firefox.
Never ever? Either you don't use it much, or you're confusing "never"
with "sometimes".
>
> The only problem I can think of is when you want to watch in
> realtime.
Exactly... you're catching up.
> tcp is bad for that and hence udp tends to be used. The odd
> packet loss is not normally that noticeable.
Except for when it is. It would appear that you do understand that it
doesn't work, but have fallen into the usual traps.
Consider - television companies have been streaming video around telco
networks for 20 years without jitter and losses; telcos have been
transport voice 2-way digital for 30 years without jitter, packet-loss
and so on. Connection-oriented packet transport has been used in the
international voice networks for at least 15 years - look up DCME for
more information.
Simply put, you cannot do real-time streaming on connectionless
networks, unless the "network" is a trivial instance, ie., point to
point with no other traffic, in which case, it's not a network.
--
| Mark Kent -- mark at ellandroad dot demon dot co dot uk |
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