[KLUG Members] ISDN vs. Satelite

[Adam Williams]

>>ISDN: 128kbit connection. Never slows down (well, except for
>>high-usage times all over the net). 
>>Sat:  400kbit down, modem (19.2kbit) up.
>>What is the best for this situation?  What are teh standard
>>delays for this?  A buddy of mine, when he had it back in the
>>day, said it was numerous seconds.  
>You will definitely notice the delay with the satellite connection
>and you won't be able to play real-time games over the internet.
>The speed of light will cost you 483 milliseconds at best, probably
>a bit more, plus the modem's 150 milliseconds, and I've been told by
>people who've used it that the real-world delay is easily over a
>second.

I've used very-small-aperture satellite connections.  Latency *IS* bad, 
and unless you can wrap photons in a warp bubble there isn't anything
anyone can do about it.

If you know much about TCP you'll also know that extreme bandwidths
coupled with high latency means constricted throughput unless you run
huge window sizes, which A.) make error correction gruelingly slow B.)
you need BIG buffers of all/both ends C.) you'll only see your maximum
bandwidth when performing a long and continuous data transfer.

With a dish you'll also get to learn the queer physics of "rain fade". 
Satellites just "disappear" for sometimes milliseconds, sometimes
seconds, sometimes minutes.  This can play havoc with your poor little
applications.  Was pretty common for us during times of rapid weather
change,  but then we we're using the link for both up and down.

>>A guy in my church has my father all geeked, despite the fact
>>that ISDN is being installed in, oh, 11 days now because of the
>>speed.  He says, "Oh, you don't send up much info, it's all just
>>downstream".

Every satellite ISP plan I've seen looks pretty half baked.  

Since the guy is a church goer remind him that the best way to
communicate with the heavens is prayer.  No latency issues. :)
 
>That's true, basically;  most typical net use requires low-bandwidth
>upstream.

True, sort of.  So they have all these requests dribbling in over banks
of modems.  Then (theoretically) tons of responses flooding back to them
from the Internet.  How do they schedule/queue this traffic out over
their satellite network?  What about fragments, lost packets, out of
orders?  I see so many ways this could not work very well.

>>My beef is:  yeah- but how much does it take to flood a 19.2kbit
>>pipe upstream?  How does this affect SSH? Anything else?  is
>>satellite easily used with an OpenBSD/linux router?

This split modem up / dish down makes routing a pain.  You need to trust
them to correctly put the streams together at the "head" end.  

You ***won't*** be using things like telnet/ssh over this connections. 
I think you'll find the delays ***so horrible*** you will not want to do
much of anything.

>SSH will be like telnet, every few characters you type will not be
>visible for an extra second.  I used to administer a machine on the
>west coast with dialup modems on both ends and I can tell you now,
>unless your fingers never slip, you want as little lag between you
>and your shell as possible.

Oh yes!  It hurts.  I've done it over a dish,  that was a neat
experience.  If I never have to use a dish network again I'll die a
happier man.

Wait for all the text to appear,  count the letters to your typo,  press
backspace X number of times,  wait for cursor to move back, try entering
the command again.  I just started typing the command into a text editor
and cut-n-pasting them into the terminal session.  Ackkk!

>>Anyway, I'm trying to convince him that the benefits of
>>High-speed Satellite access are negligible compared to the
>>instantanous nature of ISDN (low latency).  Please:  anyone with
>>experience please let me know.
>Personally -- I've used ISDN for almost a year so I know what that's
>about, and I can imagine what satellite is about.  If the prices and
>everything else were comparable I'd have to pick the ISDN setup you
>describe, above.

I'd pick ISDN,  without any hesitation.

>But then, I do most of my work on the net typing into ssh shells,
>and all of my relaxation on the net is playing twitchy real-time
>games.  So latency is vital to me.  If your family does 99% email
>and casual web browsing, and the games you play are Hearts and
>Pinochle, you'll be just as happy with the satellite.  If your
>family downloads gigabyte-sized files every day, definitely go with
>the satellite :)
>Honestly the difference between 128kbit and 400kbit isn't that big.

True.  Once you pass about 90k things (at least to me) start to offer
diminishing returns.  I have 604k DSL,  and only a few FTP sites max out
my connections.  For most things there is a tighter constraint somewhere
between my ISP and the Internet site than between me and my ISP.  But
pulling data from multiple site simultaneously at those rates is nice.

For instance: you can do interactive data (ssh) and voice-over-IP at the
same time with 128k.  Tweak your router using the tos bits and you can
run ssh even while downloading that ISO image via ftp.

>OK, you'll notice it the three times a month you have to download
>something over 10 MB, but the rest of the time it just doesn't
>matter that much.  I went from 128kbit ISDN to 1.5Mbit cable
>download speeds a few months ago, and while I notice the difference,
>it's not a _huge_ difference (until I go to download a 600 MB .iso).

Exactly.

>At these speeds, latency is just as important as bandwidth for how
>fast the net "feels," and probably more important.

Ditto.