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RE: Overflow circuit
- From: Mailing List Subscriptions
- Date: Sun Mar 28 05:55:30 2004
None of the satellite circuit I have worked on during the last five years
has been more than 550 ms RTT. They are all C-band VSAT type systems in
North America and Latin America. The economy (both $$ and quality) of
satellite is such that it is only considered ...
1) No reasonably priced or reliable terrestial alternative is available.
This has generally been the case for mineral exploration type operations.
Political motivations have also come into play in some cases, e.g. when an
unfriendly jurisdiction/neighbour exists between A and B.
2) When you don't have 2-4 weeks for all the xLEC/IXC/PTT to agree on things
so that you can come up with an end-to-end build design, then spend another
6-8 weeks coordinating the build out, and it is not unusual to spend yet
another week or two for the said xLEC/IXC/PTT to blame each other when the
circuit won't turn up because someone left a piece of tone generating test
equipment plugged in. I can turn up a sat circuit in as little as 24-hours
once the teleport is in place (typically 2-3 weeks for remote locations).
The same also goes for increasing/descreasing bandwidth on demand (can be
3) When you need to reduce the number of points of failures to that single
(30,000 km * 2) hop.
4) When you need a reliable/cheaper backup/overflow to the primary
terrestial circuit (my original question for starting this thread ;)
> -----Original Message-----
> From: email@example.com [mailto:firstname.lastname@example.org] On
> Behalf Of Alexei Roudnev
> Sent: Saturday, March 27, 2004 11:21 PM
> To: Rafi Sadowsky
> Cc: Steven M. Bellovin; Michel Py; email@example.com
> Subject: Re: Overflow circuit
> 500 RTT, + 150 jitter buffer, + something else... it will be
> 700 - 800 msec, more likely. When we worked with a few
> sattelliite lines (5 years ago), I never saw ping rtt less
> than 800 msec. Of course, it does not mean that you can not
> see RTT = 500 msec (but I never saw it).
> But I was talking aboutt other thing - ~1second delay != bad
> quality, it is just a delay, which means that, if you have
> good echo cancellers (which is interesting question) and
> follow talking discipline, you can talk without any problems.
> It explains, why satellite links + VoIP can be a good
> combination (moreover; after satellite delay, which is 500 -
> 600 msec, VoIP additional delay ,which is 50 - 150 msec, does
> not change overall delay so much, as in case of VoIP over bad
> link _vs_ traditional telephony (200 msec vs 20 msec = 10
> times; 800 msec vs. 600 msec = 30%).
> > ## On 2004-03-27 19:30 -0800 Alexei Roudnev typed:
> > AR>
> > AR> It means, that satellite (with it's 1 second delay and
> > Geosynchronous satellite IP link RTT can be just over 500 mill-sec
> > (real life experience) IMHO thats a rather significant difference
> > --
> > Rafi