At 05:38 PM 12/16/97 -0800, Fred Baker wrote:
>... on the order of half a second of fixed propagation delay. TCP will
transfer
>data at one window per round trip, a round trip is on the order of half a
>second, and slow start makes GEOS look bad. All of this is true.
>
>There are some fixes. TCP "spoof" engines that terminate the TCP session on
>either side of the satellite link can be used to make the "round trip" in
>question only account for terrestrial time. This means that end to end
>security (IPSEC) and some end to end assumptions are violated - but heck,
>in a world full of NATs, that's not news. TCP Large Windows (implemented in
>Microsoft Window s '98, I am told) also helps for long-lived sessions, and
>with HTTP 1.1 and 2.0, sessions are growing in length. So TCP does in fact
>work over GEOS, and the latency issues can be mitigated somewhat. Fifteen
>years of experience in the Internet says it works just fine, there's just
>some considerations you need to make.
... good writing, Fred. Can I add my $0.02?
In the "real-world" of satellites I've lived in for the past decade or
more, I've seen a lot of marginal links, due to any number of
considerations and variables which can degenerate C/N and Eb/No
performance, and which therefore raise BER to levels which can easily allow
for the corruption of data. With Eudora's latest offering on the 'net up
to some 9mb in size, a BER of 10E-6 would be pretty useless. "Spoofing"
would pass the file to a user without noticing the lost data, and my end
user would quickly conclude that "my" Internet sucks. and, the user would
be correct. :-)
>Now, let's talk about LEOS.
>If you want my honest opinion, in so many words, this whole debate in the
>press about GEOS vs LEOS, and delay, is not a technical debate. It has
>technical aspects, but those who understand them look at them and say "OK,
>so do this thing defined in <mumble>, and you'll be fine." It's really a
>marketing debate, and insofar as the press goes beyond its educational role
>to leading folks to make simplistic "me tarzan, you jane, this good, that
>bad" analysis, it has misled its readership and become the tool of one side
>or the other.
I agree.
I also think a most important distinction between the two services will be
billing methods. LEOS plan to bill by increment of time, or by the number
of bits passed, or some other incremental-use system. GEOS have
traditionally offered fixed costs based on power and bandwidth, though this
may change based on some of the conversations I've heard at recent
conferences. (I don't really think it will, due to competitive pressures.)
A fixed cost plan works for the 'net - for ISP businesses, providers,
etc., who can't really function well if they don't know their own costs.
Incremental billing will work for "direct-to-end-user" services far better
than to intermediate ISPs. Different customers, different applications
therefore seem better served by the two platforms.
Frankly, as the owner of a couple of ISP businesses with thousands of
end-users (translation: morons), I'd rather not deal with the end-users in
160 countries - the support issues will bankrupt you if you're not careful.
B
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