Wading into water way over my head here, but still...
On 2001-12-17 17:53:28 -0800, Randy Bush wrote:
> i can't get my head around this qos stuff, at least as it applies to
> backbone or isp networks. our customers pay us not to drop packets.
> so adding complexity in order to choose which packets to drop seems a
> bit strange.
My understanding is that the "Quality" in QoS covers a range of
variables, depending on what you care about.
If you include ordering packets and not simply dropping them or not,
then the problem becomes more interesting. For instance, voice
communication has extremely tight jitter requirements, a bit looser
latency requirements, and is pretty minimal bandwidth requirements.
Carry voice traffic on the same network as, say, web traffic and you
may wish to defer a port 80 packets that could cause unacceptable jitter
in a voice stream.
Now, I'm not a router guy, so this may not matter in the Real World(tm),
but QoS isn't necessarily something you can ignore just by making sure
your network is reliable. Even if no packets ever get dropped, you may
still exceed the jitter requirements of a phone call, making it
impossible to hear the person at the other end of the phone. In such a
case, using "drop" as a synonym for "defer" may be the right thing to
do: the better of several unhappy alternatives.
But if your customer pays you not to drop packets, then that's what you
should do. ;)
-- Shane
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