Re: [LARTC] QoS for VoIP

["Ming-Ching Tiew" <mingching.tiew@redtone.com>]

From: "Santiago" <santiago@elportal.net.ec>

> If you have for example 1024 Kbps, you have to create a class (maybe htb)
> about 920Kpbs to create the queue. Then you have to attach the prio qdisc
to
> this class, mark the voip packets and send to class :1 in the prio qdisc.
>

That's what I am talking about. You said it **VERY** easily that "If you
have for example 1024 Kbps, you have to create a class about 920 Kbps ...".

But what's the reality. The reality is that you might not have
a 1024 Kbps link, even though the ISP you sign up with might
claim that. You don't know for sure. Even perhaps for most of
the days you have 1024 Kbps, certain peak hours you might
be clamped down to a lower figure due to congestion at the
BRAS of the ISP.

And how do you arrive at your magic figure of 920 kbps ?

And bear in mind that most ADSL are asymmetric, your uplink
is usually lower than your downlink. Even if you clamp down
your down link, if you don't police ( or rate limit ) your uplink,
you still can't really control the link. So in practice you will
actually police the rate of download to a figure slightly smaller
than your uplink speed. There you can see, your overall throughput
of the internet (download ) is significantly slowed down.




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