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Brian thanks for your input I did read the whoooole post very informative
thanks again Doug
----- Original Message -----
From: "Brian Mense" <bmense@xxxxxxxxxx>
To: <omega-list@xxxxxxxxxx>
Sent: Wednesday, August 21, 2002 12:00 PM
Subject: Re: Sattelite datafeed faster than landlines ?
> It's going to be very hard for anyone to profess that satellite or land
> based is faster as a generic statement. There are to many other factors
to
> consider that impact the throughput of the connection.
>
> Satellite delay is caused by the distance that the signal has to travel
from
> the VSAT unit to the satellite. This delay of ¼ second is present in all
> satellite-based services including the long-distance phone call that we
use
> today. The throughput performance however, remains unaffected.
>
> A single hop delay is the delay caused by the transmission from a VSAT
unit
> to another unit. However, certain VSAT topology uses the master
hub-station
> as the transit gateway to connect between two remote units and that
> introduces a two hop delay for each transmission or a 1/2 second delay.
> Voice calls are especially sensitive to the delay as are TCP conversation
> that haven't been 'tuned' for transmission over a satellite connection.
>
> xDSL and Cable technologies don't suffer from the same delay that a
> satellite connection suffers from but there are many other issues that
> affect 'speed' that the service providers don't draw attention too.
>
> Cable networks are a shared bandwidth asymetrical technology. You have a
> 10Mb upstream connection MAX and a 28Mb downstream MAX in most cases. The
> upstream is the connection from your PC to the internet and the downstream
> is the inverse. What most cable companies do is aggregate multi CMTS
hubs,
> what you connect into at their site, into a single connection to the
> internet. The connection to the internet can range from as slow as 56K to
> 144Mb. Typically they use multiple T1's (1.544Kb) to the internet. Some
do
> have the faster connection such as ATM(144Mb) or T3 (45Mb) connections,
but
> if they do they will only typically have two or four.
>
> Now do the math, on cable they typically try to limit the PC to about
> 250-500 PC per CMTS Upstream/Downstream, the folks you share the bandwidth
> with. If you take 500PC's/28Mb=56K per PC on average worst case. Now the
> cable operator usually has many subscribers, say they have 10,000 customer
> on a fully max out system. If they have a max of 500 users per CMTS unit
> and each unit is capable of delivering 28Mb to the users, that's 560Mb of
> data at one time that can be sustained in their system.
> (10000Users/500PerCMTS*28Mb=560Mb). Now their connection to the internet
> could be the a typical best case 144Mb connection x 2 for 288Mb. There
are
> faster, but not common. That's almost a 2-1 oversubscription. That is an
> excellent ratio and not realistic, more common is a 6-1 to 10-1
> oversubscription. So they expect only 1 person out of 6 to 10 to be using
> the system as the same time. I like cable because it's truely takes
> advantage of the fact that not everyone is transmitting at one time. You
> can have as much as 28Mb available to you, if configured so.
>
> xDSL is not a shared connection, as is the case with cable, your limited
to
> what you paid for. Folks believe this is a benefit for xDSL users, but
only
> if the service provider doesn't oversubscribe the links. When they do
> oversubscribe the links you can have a connection that is slower than a
> dialup connection at busy times. How can this be.... Well most xDSL
system
> are asymetrical, you might have 128Kb upstream and 1.544Mb downstream.
Now
> this bandwidth isn't shared and you have it all to yourself, to the what's
> referred to as the DSLAM. The DSLAM is where your connection terminates.
> That's where your 128Kb/1.544Mb connection guarantee stops. The question
is
> then how do they have there DSLAM connected to the internet. Let's take
the
> same example as above and say there are 10000 users. In a downstream
> configuration that is a MAX of 15G of bandwidth in their network.
> (10000Users*1.544Mb=15.44G) Now take the above example of an
> oversubscription of 10-1, which would result in the service provider
having
> 1.5Gb of bandwidth to the internet, not likely. So they usually use the
> same type of connection as cable, but oversubscribe it a bit more. So
lets
> say they have four 45Mb connections, that would be an oversubscription of
> 1-85.
>
> Enough of the figures don't lie, but liars figure examples. I believe the
> most important aspect to consider is the stability and consistancy of the
> connection. I have both an internet connection feed as well as a
satellite
> connection. By far the satellite connection provides a much more stable
and
> consistant connection than does the internet. Both of them do suffer from
> delays during fast markets. Then again is the delay our connection or the
> data from the exchange?
>
> Not sure if all my ramblings are going to be helpful, but I figure a few
of
> you might make it to the end of the message. :) The key is not the
> quantity (speed), but the quality (reliable). Satellite wins that contest
> imho
>
> Brian
>
>
> ----- Original Message -----
> From: "cwest" <cwest@xxxxxxxxxxxx>
> To: <omega-list@xxxxxxxxxx>
> Sent: Wednesday, August 21, 2002 10:23 AM
> Subject: RE: Sattelite datafeed faster than landlines ?
>
>
> > Non-terrestrial is always slower, but the delay may not be relevant as
its
> > only a few seconds at the most. However, shared bandwidth is another
issue
> > with satellites and that can cause considerable delays, relatively.
> >
> > -----Original Message-----
> > From: Robert Linders [mailto:Robert@xxxxxxxxxxxxxx]
> > Sent: Wednesday, August 21, 2002 6:01 AM
> > To: omega-list@xxxxxxxxxx
> > Subject: Sattelite datafeed faster than landlines ?
> >
> > << File: Clear Day Bkgrd.jpg >> Hi List,
> > I seem to have a discussion with a friend of mine who claims that a
> > sattelite connection (for instance with S&P Comstock) has a faster
> > throughput than a landline (internet ADSL or T1).
> >
> > I believe that due to the propagation delay (signal travels up and down
to
> > the sattelite) the landline should "always" be faster !
> >
> > Any ideas?
> > Anybody with experience or maybe who has both ?
> >
> > Thanks
> > Robert
> >
> > =================================
> > Robert Linders
> > Orlando
> > Robert@xxxxxxxxxxxxxx
> > =================================
> >
>
>
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