[asterisk-users] QOS for outgoing SIP ... Who needs QoS anyway!

[Brian J. Murrell]

On Thu, 2008-04-17 at 08:36 -0400, J. Oquendo wrote:
> 
> Brian J. Murrell wrote:
> 
> | But certainly at my choke point which is of course my Internet uplink,
                                                          ^^^^^^^^^^^^^^^
>  I
> | can apply QOS (i.e. traffic shaping, which is what the OP's router was
> | offering) to make sure that what little capacity is there is giving
> | priority to my voice traffic.


> Let's take a bare bones look at this. Let's say your connection is 300k

Downstream or upstream?  Notice I said "Internet uplink" in my previous
message.  Anyone at all familiar with traffic shaping understands that
they can only shape the uplink, not the downlink.

The best you can do with the downlink is to "police" it to try to keep
the congestion below 100%.  But that's mostly alright given how the ISPs
have perverted the Internet with "asymmetric" last mile connections to
consumers.

> and you have five packets coming in at 60k each to saturate your network:

First of all,your whole example is pointless as you are clearly talking
about downstream and I have already said that anyone knowledgeable with
traffic shaping knows you cannot shape the downlink only the uplink.
However, let's see where else your example fails.

My MTU is only about 1500 bytes or so, so 60k packets to me are
impossible.  I'd tend to guess that for most of the Internet, packets
max out at about 1500 given the prevalence of ethernet connected
devices.  So in order to saturate my 300k you'd have to send me 200
packets all in that one second.

> Provider to you
> 
> Packet 1 ----> You
> Packet 2 ----> You
> Packet 3 ----> You
> Packet 4 ----> You
> Packet 5 ----> You
> 
> You believe that this is happening:
> 
> Packet 1 ----> You ---> This is voice send it first --> Device
> Packet 2 ----> You ---> This is voice send it first --> Device
> Packet 3 ----> You ---> This is P2P leave it 4 last --> Device
> Packet 4 ----> You ---> This is P2P leave it 4 last --> Device
> Packet 5 ----> You ---> This is AIM make it second! --> Device

As I've said, you cannot shape this traffic.  I've already conceded
that.  But again, OP was talking about uplink shaping, not downlink.

> Its fine and dandy, but the problem is you're still getting 5 packets.
> You're still saturated period.

Right.  You cannot shape the downlink.  You can only police it to
prevent packet loss.

> No QoS in the world outside of your
> provider and more bandwidth can alleviate that.

If more bandwidth is an option, but I already stated that for many
people, it's not an option.  They have exactly one or two choices and
they are subscribed to their maximum available.

> QoS on a home router... Useless COMING IN. Going out...
> Means little but helps MINIMALLY.

Not at all "little".  If you have a lot of low priority outgoing traffic
(i.e. p2p) saturating your link, uplink traffic shaping will mean the
difference between a completely unintelligible call and something very
acceptable.

b.

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