On 12/06/2013 10:22 AM, Robinson, Dave C (Dave) wrote:
> Jim et al,
>
> I agree with your comments on Diffserv. I'd go further and
> characterise Diffserv as a business tool whereas ECN and general AQMs
> as network optimisation tools. By that I mean that Diffserv should be
> used by an application to specify a business policy be it low latency
> for VoIP / gaming or preferred forwarding for your video service. AQMs
> can guess at the types of traffic. For example an isochronous flow of
> short packets could well be VoIP which would benefit from expedited
> forwarding. But it has to be an operator policy to decide between two
> VoIP services. 
>
> Same argument for bulk traffic from different video services. One can
> be a partner traffic from your internal CDN nodes which you would like
> to accelerate through your network.
>
> ECN is a good tools to use to tell sources the the network is becoming
> overloaded and is kinder than dropping packets. But it cannot know the
> business policy. Just help manage congestion.

1) it's also a non-business policy issue: I may want to provide low
latency to a friend or child playing a game at my house, or provide
poorer time/throughput guarantees to a web or ftp download. Yes, this
indeed a niggle (;-))

2) I'd be happier providing a metric to the network's management than an
implementation. 
Let's assume I'm doing VOIP or something else small and low-latency to a
known endpoint, and want to say for this socket, (I want = <100
milliseconds, I'm inducing  load =  0.03 mbits/sec).  The implementation
can turn that into a DIFFSERV option, if it's supported, or something
else if not.   This, IMHO, deserves consideration, but not as part of
this discussion.  Thus "off topic".

--dave


-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
[email protected]           |                      -- Mark Twain
(416) 223-8968

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