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List:       ms-ospf
Subject:    Re: Congestion Avoidance & Control for OSPF Networks
From:       "Ash, Gerald R (Jerry), ALASO" <gash () ATT ! COM>
Date:       2002-08-23 19:40:18
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Hi Chaoping,
 
> If we take a deep look at the congestion state in the draft, we can find
> that it is consisted of two parts actually:
> 1. Entering (or detection of) congestion state
> 2. severity of the congestion
> 
> The draft does state several possible ways to detect congestion, which is
> related to part 1. But it is just a little short in standardizing the
> detection methods. The draft also states low/high congestion states, which
> is related to part 2. But the draft does not provide any specification on
> what conditions make a low or high congestion. Interoperability would be a
> concern here.

Agreed.

> I'd like to propose the following suggestions to improve the above two
> parts for better interoperability and I believe they are not difficult to
> implement.
> 1. Congestion Detection
> Assign standard values to congestion detection methods and signaling the
> value in the choke LSA/LLS signaling mentioned in the draft.
> For Example, the detection value could be
> 1= method based percentage of consumed, internal work queues exceeding a
> thresh-hold percentage
> 2= Missing some percentage of hellos;
> 3= Frequent retransmissions are required.
> 15= other method
> 
> This is analogous to some other protocols that signals some algorithms
> selected for current use and provides a cause code when certain events
> occur.
> 
> 2. Severity of Congestion
> Measure severity of congestion with time, since all equipment has timers
> implemented inside. Something similar to chronic or acute congestion.
> Prolonged congestion requires serious measures to overcome.
> For example,
> Prolonged congestion = high state
> Short congestion = low state
> The time-based congestion severity measurement can be used along with the
> internal congestion interval timer that is stated in the draft. With some
> modification, they should complement each other pretty well.

Your ideas are very good here.  Both the degree and duration of congestion should be \
considered in defining congestion state.  We'll plan to incorporate along these lines \
in the next rev. of the draft.

Thanks,
Regards,
Jerry


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