[Asterisk-Users] ISPs with QoS for VoIP?

[Steve Underwood]

Roderick Montgomery wrote:

>According to alex at pilosoft.com:
>  
>
>>The only case where QoS is useful is on tail-end circuits. Everywhere 
>>else, having bigger pipes is much more preferable to QoS.
>>    
>>
>
>Um, not to state the obvious, but aren't bigger pipes ALWAYS preferable?
>
>QoS does not make packets move faster.
>
>Please reread the previous sentence.
>
>QoS implementations essentially tell network elements (routers, switches,
>etc.) which packets may be slowed or dropped entirely relative to other
>packets. I think everyone here can agree that slow or failed delivery of
>packets is a Bad Thing. However, since the "bigger pipes" solution usually
>carries a monetary cost, it's not always available. 
>
>QoS is a "damage control" technology. If your network needs outstrip your
>network capacity, QoS is one way to deal with the problem: attempt to
>de-prioritize some traffic to allow more capacity for your voice traffic.
>
>If a network segment or element becomes congested, there are many other
>options available -- remove the competing traffic altogether. Complain to or
>change your ISP (if it's their problem). Segment your voice traffic with
>VLANs.
>
>If your network is already congested, QoS is a way to direct the effects of
>congestion at the traffic that is less important to you. It is not a way to
>make "good" traffic go faster.
>

What you say is basically true, but I would put things differently.

Streaming media traffic never has to go faster, but it *must* never go 
slower. There is a fixed amount of bits to get to the other end, at a 
well controlled pace. A fat pipe will not give you that. The bursty 
nature of internet traffic means you will get at least some 
interruptions in voice with even the fatest non-QoS pipe. Think of it as 
voice being slashdotted :-) Or think of VoIP the day a huge bugfix comes 
out of Redmond.

IP + QoS, like ATM and other streaming aware techniques will guarantee 
your voice data is never screwed up. It has to work end-to-end to be 
fully effective, though, and you generally can't get that kind of 
service - specifically you may, but not generally.

If most Internet traffic is really porn, then the key issue is how much 
is still pictures and how much is streaming movies. The streaming movies 
aren't bursty, so an internet full of those and VoIP might see few 
hiccups in the VoIP. If its mostly stills, those are bursty, and VoIP 
really needs QoS. :-)

Regards,
Steve