Subject: RE: draft-ietf-pilc-asym-00.txt

From: "Falk, Aaron" <[email-masked]>
Date: Thu, 14 Oct 1999 11:06:15 -0400

Hi, Goran. I have some questions...

> We are working on an idea to remedy the effects of bandwidth asymmetry
> using a version of TCP/IP header compression. Our algorithm should be
> able to achieve effective ACK-sizes considerably smaller than 
> one octet
> and thus remove the effective bandwidth asymmetry in most realistic
> systems.

Smaller ACKs would exacerbate traffic symmetry. Perhaps you are referring to
the limitations that asymmetric links would pose on performance?

> 
> We implement a compressor at the queue where ACKs get congested
> and a decompressor somewhere on the other side of the bottleneck link.

Hmmm...how do you know where the ACKs are getting congested? Congestion
moves around. Are you assuming that you have a *very* asymmetric tail
circuit? If so, this sounds like a single link optimization. Do these links
occur frequently? What kind of asymmetry do you see?

> The compressor concatenates and compresses ACKs belonging to the
> same TCP-connection. We add information about queue-arrival-time
> of the concatenated ACKs. The decompressor then recreates the original
> ACKs and sends them uplink with the same intervals as they arrived at
> the bottleneck queue.

What about path diversity? It sounds like you are assuming that the same
compressor always talks to the same decompressor. You are running into the
same architectural risks that PEPs do (I haven't even mentioned IPSEC).

> 
> We believe that our method could be mentioned in the asymmetry-draft
> and are open for discussions.
> 

I'd like to hear more details on the mail list first.

--aaron