[e2e] TCP Loss Differentiation

L.Wood@surrey.ac.uk L.Wood at surrey.ac.uk
Tue Feb 24 05:31:37 PST 2009


Actually, it should be possible to combine existing per-flow
statistics (e.g. Netflow) with the kind of existing radio-aware
statistics generated by e.g. RFC4938 (also implemented by Cisco),
to give a good idea of when loss on a (noisy radio) channel is
correlated to packet loss, and isn't congestion.

A complete history isn't needed. The last couple of hundred
ms should do it. All that's being done is combining observations
about the channel, and about the packets flowing through the link,
available in existing code.


<http://www.ee.surrey.ac.uk/Personal/L.Wood/><L.Wood at surrey.ac.uk>

-----Original Message-----
From: end2end-interest-bounces at postel.org on behalf of Fred Baker
Sent: Mon 2009-02-23 23:10
To: Jon Crowcroft
Cc: end2end-interest list
Subject: Re: [e2e] TCP Loss Differentiation

On Feb 23, 2009, at 3:01 PM, Jon Crowcroft wrote:

> if each router were to record in every packet in a flow, all the  
> packets it had seen, the order it had seen them, and the routers own  
> address, then when any packet arrives, you'd have a cmplete history  
> of packets predeceessors and successors and gaps, and where gaps are  
> caused, and so a receiver can disambiguate on a _per packet_ base  
> when a loss was not congestive...

Great! I'm really excited to hear that every router has now sprouted a  
reason to add a few more gigahunks of memory, and that service  
providers are willing to pay the operational expense in heat and  
power! My product managers will be truly dumbfounded that they had not  
tumbled on that source of revenue in the past. And I'm sure that the  
ISPs will be all too eager to pass the upgrade cost along to their  

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