Extreme congestion (was Re: inter-domain link recovery)

Fred Baker fred at cisco.com
Thu Aug 16 04:40:21 UTC 2007


On Aug 15, 2007, at 8:39 PM, Sean Donelan wrote:

> Or would it be better to let the datagram protocols fight it out  
> with the session oriented protocols, just like normal Internet  
> operations
>
>   Session protocol start packets (TCP SYN/SYN-ACK, SCTP INIT, etc)  
> 1% queue
>   Everything else (UDP, ICMP, GRE, TCP ACK/FIN, etc) normal queue
>
> And finally why only do this during extreme congestion?  Why not  
> always
> do it?

I think I would always do it, and expect it to take effect only under  
extreme congestion.


On Aug 15, 2007, at 8:39 PM, Sean Donelan wrote:
> On Wed, 15 Aug 2007, Fred Baker wrote:
>> So I would suggest that a third thing that can be done, after the  
>> other two avenues have been exhausted, is to decide to not start  
>> new sessions unless there is some reasonable chance that they will  
>> be able to accomplish their work.
>
> I view this as part of the flash crowd family of congestion  
> problems, a combination of a rapid increase in demand and a rapid  
> decrease in capacity.

In many cases, yes. I know of a certain network that ran with 30%  
loss for a matter of years because the option didn't exist to  
increase the bandwidth. When it became reality, guess what they did.

That's when I got to thinking about this.




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