Subject: Asymmetry draft ?

From: Mahesh Sooriyabandara <[email-masked]>
Date: Tue, 31 Oct 2000 13:35:52 +0000

Dear Hari,

I was following the PILC mailing list for quite a sometime and wonder
what is going to happen to asymmetry draft. Last thread on this topic
showed that there are lot of disagreements to the draft. For the same
reason I believe that it needs to be revised rather than let it
disappear.

It will be nice to have a document describing the Asymmetry problem and
solutions/(best practices) since there are some disadvantage networks
which can be benefited from it. The draft should address all (  as much
as possible) different asymmetric networks and different techniques. The
former draft may lack this generality. To achieve this contributions
from everybody dealing with different asymmetric networks will be
needed. There are some commercial products out there which uses some
mitigation techniques to improve TCP performance.

We have done series of experiments on this topic and I have seen quite a
lot of techniques ( mainly ACK modification) proposed by various
researchers. Generally each technique is addressing a certain type of
networking technology. FYI following is a list of techniques I have seen
so far:

1) TCP Header Compression    [a]
2) ACK filtering/ Sender Adaptation    [b]
3) ACK Congestion Control    [b]
4) ACK compaction    [c]
5) ACK Companding/ Expanding    [d]
6) Window Prediction Mechanism    [e]
7) Acknowledgement based on Cwnd Estimation    [f]
8) ACK decimation    [h]

[a] Jacobson, V. ,Compressing TCP/IP Headers for Low Speed Serial Lines,
RFC 1144,1990, IETF.

[b] Balakrishnan H, Padmanathan V.N. Katz R. "The effects of asymmetry
on TCP performance" Mobicom Budapest Hungary 1997, ACM/IEEE.

[c] Nihal Samaraweera "Return Link optimization for Internet service
provision using DVB-S networks ACM CCR June 1999.

[d] Johansson G.L , Shakargi, H. Kanljung, C. Kullander, J.
‘ACKNOWLEDGEMENT Compression Rev B’, Technical Report December 1999.

[e] A Calveras, Linare, J. Paradells, J. “Window Prediction Mechanism
For Improving TCP in Wireless Asymmetric Links”, Globecom 98.

[f] Ming-Chit, I.T, Jinsong, D. Wang, W. “Improving TCP Performance Over
Asymmetric Networks” ACM Communication Computer Review, July 2000.

[g] R. Segura “ Asymmetric Networking Techniques For Hybrid Satellite
Communications” NC3A, Technical Note 810. August 2000.

Above techniques have been analysed ( or can be used) in different
asymmetric networking technologies. (like Cable networks , packet radio,
ADSL, DVB-S with return dial-up, Wireless cable modem with dial up
return, DVB satellite forward with narrowband Inmarsat return)

It is obvious that lot of work has been done in this area during past
few years. This may be a correct time to start discussing this to make
use of them and get things correct with the Asymmetry draft. I believe
there are lot of researchers who are willing to put their input in to
this.

Regards,

Mahesh.