Subject: RE: [Diffserv] Here's the complete EF-service definition.

From: Jon Bennett <[email-masked]>
Date: Thu, 27 Jul 2000 09:33:49 -0400

> Jeez, sorry, my earlier definition was absurd, hehe. How can any
> finite-capacity scheduling scheme provide any guarantee without
> constraints on the arrival rate? So here's the completed definition :)
> 
> The following definition will handle the overloading 
> scenarios that you pointed out. Basically, this definition 
> says that the EF packet latency is bounded by the 
> 1/Configured_Rate *if* aggregate arrival rate is less than 
> Configured_Rate. Else, there is no such guarantee.

Given that the scenario that I described was not 'overloading', 
but was a valid pattern of arrivals for the EF aggregate across a 
number of input links what you have just done is to restrict the EF
PHB to only cover a highly restricted subset of possible arrival 
patterns. Since it is not possible to cause the input to a router to
conform to this restriction if there is more than one input link, 
this definition would not appear to work.

Out of curiosity, if you agree that a new definition is needed, 
would you care to explain what is wrong with the one that we proposed?

jon

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From: Mahadevan Iyer <[email-masked]>
Date: Thu, 27 Jul 2000 07:46:09 -0700 (PDT)

> this definition would not appear to work.

Yes, you are absolutely right. I realized just moments after sending my
previous email that my definition is still far from complete. Simultaneous
packet arrivals at different input links should not be regarded as
non-conforming of course.  
My definition *is* valid if the packet arrivals are defined as those at
the input to  the output queue (if the router has an output queue.)
But this definition is still restrictive and doesn't apply to the
entire router as a black box.

> would you care to explain what is wrong with the one that we proposed?

My aim here is basically to come up with a precise, yet simple definition
(if at all it's possible) for EF service.

Can you give me a pointer to where I can read the definition you proposed?
Or do you mean the one in RFC 2598, section 2, page 1?

Thanks :)

Mahadevan.