[e2e] how far it queues?

Eric A. Hall ehall at ehsco.com
Fri Oct 4 09:30:04 PDT 2002

on 10/4/2002 10:39 AM Alexandre L. Grojsgold wrote:

> Lets assume also that we run a "standard"  backbone network, made out ou
> routers of a popular brand and of hi capacity deterministic links. And
> that looking at traffic statistics we see that instataneous mean traffic
> (the traffic reported by the router itself over a 5 minutes period) never
> exceeds 80% of the maximum bandwidth, event at most busy hours.

> Then come people with some voice and video applications and tell us that
> they have some special needs to run their stuff:

> Ok, given these needs, what can one expect from the above mentioned happy
> and healthy net? Will it fit the needs? Most of the time? Half the time?
> Hardly?

Without any external controls, the UDP streams will eventually cause the
TCP sessions to adapt to the UDP traffic. TCP's rate control services are
sensitive and therefore friendly; UDP has no rate controls. In the face of
continous traffic from steamroller UDP flows, the TCP sessions will back
down until there is no loss, even to the point of dropping.

TCP needs the benefits of QoS more than voice does.

> Again, I am supposing an *uncongested*  and sane network, where only fifo
> queueing is used.

If ther is no congestion there is no problem.

Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/

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