Subject: Re: making satellite channel loss transparent

From: Osnat Mokryn <[email-masked]>
Date: Thu, 22 Jul 1999 11:51:53 +0300

ketan bajaj wrote:

>
>
> The issue i'm trying to raise here is why bother TCP to distinguish between
> packet loss due to corrution or due to congestion, why not make the
> corruption loss transparent to sender tcp ? Some of the work ive seen in
> doing the above, are split-connection and berkeley snoop designs. But they
> are limited to a particular satellite network topologies, where the
> satellite hop is the last hop of the end-to-end path. What about more
> generic topologies ?
>
> ketan
>

There are several companies who tackle this problem. Obviously, solving a
problem
by a hop-by-hop special optimizations is a very good way to utilize each hop.
So they do what is called today "spoofing" - cutting the TCP session to 3
different segments,
(more accurately - 3 different sessions) where the middle segment is the
satellite link.
Usually, on the satellite segment they use a dedicated protocol.
One of the companies I personally know is flash networks
(http://www.flash-networks.com),
their homepage is quite good.

Osi.

>
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--

Osnat Mokryn

---

From: "ketan bajaj" <[email-masked]>
Date: Wed, 21 Jul 1999 23:50:24 PDT

Hi,
Pls refer to section 3.3.4 of 
http://www.ietf.org/internetdrafts/draft-ietf-tcpsat-res-issues-09.txt

"
Differentiating between congestion (loss of segments due to router buffer 
overflow or imminent buffer overflow) and corruption (loss of segments due 
to damaged bits) is a difficult problem for TCP.  This differentiation is 
particularly important because the action that TCP should take in the two 
cases is entirely different .... "
"....
Perhaps the greatest research challenge in detecting corruption is getting 
TCP (a transport-layer protocol) to receive appropriate information from 
either the network layer (IP) or the link layer. Much of the work done to 
date has involved link-layer mechanisms that retransmit damaged segments.  
The challenge seems to be to get these mechanisms to make repairs in such a 
way that TCP understands what happened and can respond appropriately."

ketan

---

From: PAN Jianping <[email-masked]>
Date: Thu, 22 Jul 1999 09:52:56 -0400

At 11:51 AM 7/22/99 +0300, Osnat Mokryn wrote:
> session to 3 different segments, 
>their homepage is quite good. Osi. 

Another example is the SkyX from Mentat Inc., related information can be
found at http://www.mentat.com/skyx/whitepaper.html

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  PAN Jianping                                      [email-masked]
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