Subject: Article on IP over Satellite

From: Aaron Falk <[email-masked]>
Date: Sat, 24 Oct 1998 17:39:04 -0700

Check out:

http://www.satellitetoday.com/viaonline/issue/1098ip.htm

FYI,

--aaron

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From: Luigi Rizzo <[email-masked]>
Date: Sun, 25 Oct 1998 07:59:11 +0100 (MET)

> http://www.satellitetoday.com/viaonline/issue/1098ip.htm

I find the following quote especially significant:

    <about Mentat's Skyxpress (Skyx) Gateway System>

    Skyx does not change how TCP works over the terrestrial portion
    of the connection, nor does it break TCP's end-to-end semantics
    unlike spoofing solutions, which artificially inject acknowledgements
    into the TCP stream in order to attempt to speed up data
    delivery," says DC Palter, Mentat's vice president for sales
    and marketing.

    ...
    average throughput, on a simulated forward link speed of 10
    Mbps with a reverse link speed of 128 kbps ...  In the case of
    500 KB file, the Skyx delivery time is 2.2 seconds as opposed
    to 36.1 seconds for TCP/IP.

2.2s amount to about 4RTTs, so either they use a proxy approach
(which is not different from "breaking e2e semantics and artificially
injecting acks"), or they start with an unreasonably large initial
window.

Once again, can you say "congestion control".

	cheers
	luigi

-----------------------------+--------------------------------------
Luigi Rizzo                  |  Dip. di Ingegneria dell'Informazione
email: [email-masked]    |  Universita' di Pisa
tel: +39-50-568533           |  via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522           |  http://www.iet.unipi.it/~luigi/
_____________________________|______________________________________

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From: Tom Henderson <[email-masked]>
Date: Mon, 26 Oct 1998 09:15:17 -0800 (PST)

>     delivery," says DC Palter, Mentat's vice president for sales

According to a presentation at NASA Lewis last June, Mentat does use a
transport gateway to split the connection, and uses a proprietary
congestion control (no slow start, rate control) over the satellite
portion.

Tom