[asterisk-users] Moving from DSL to T1

[Kevin Keane]

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Hans Witvliet
Sent: Sunday, September 12, 2010 11:52 PM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: Re: [asterisk-users] Moving from DSL to T1

On Sun, 2010-09-12 at 15:32 -0700, Kevin Keane wrote:
> In terms of telephony, a T-1 can make a huge difference over DSL. DSL 
> gives you a lot of raw bandwidth, true, but for voice that really 
> doesn't matter all that much. Voice calls only take a relatively small 
> amount of bandwidth anyway; you can fit dozens of concurrent calls 
> into a DSL or T-1. When used strictly for telephony (non-VoIP), a T-1 
> is designed for 24 concurrent calls, each one takes up 56kbit. For 
> VoIP use, most providers tell you that a phone call takes up about 
> 80kbit/s.
> 
>  
> 
> What really matters is the latency, and T-1 is a huge improvement over 
> DSL in that area. The easiest way to measure latency is the ping time 
> to a server that is "close to you" Internet-wise. A DSL has latencies 
> of between 40ms (if it's extremely good and not too many other people 
> are using it) and 1000ms (if there is a problem somewhere). A good T-1 
> may have latencies as low as 5 ms or so. Also, with a T-1 the 
> bandwidth is guaranteed and bidirectional. With a DSL line, you may 
> get burstable bandwidth - you don't actually have that bandwidth, you 
> just get to compete for excess bandwidth with your neighbors.

You consider 40ms extremely good???
Either your isp or youself must have a considerable number of hops to cross.
At home (cheap abo) i got following transit delays (round trip) national 15 ms international 17-35 transatlatic or satelite is above 200ms

At work
national 3-4 ms
international 20-25 ms

****
(sorry about the weird quoting - Outlook insists on top-posting!)
Wow. I think I have to move to the Netherlands. The European telecom landscape is quite a bit different from US, so I'm not completely surprised. The USA no longer has the fastest Internet in the world anyway.

My numbers are from an AT&T DSL line in California, suburban San Diego county, and just around the corner from the central office. So it is not the distance (with DSL, the distance does make quite a difference). On the other hand, there are several hops just to get to the Internet backbone.

Your work numbers sound like what I have seen with a T-1 here.

 

> Latency also is the reason VoIP does not work at all over satellite 
> connections even though they tend to have plenty of bandwidth.
Please define "does not work at all over satellite" ???
Sure, it is not studio HIFI quality, but is th same quality as you get from official commercial telco providers.
We still have voip over S-band and X-band satelites running NOW between NL and afghanistan. All the people are more than satisfied.

**********
Should have been more specific. I was talking about Internet over satellite in the USA. I believe those are geostationary TV satellites. I am not familiar with S-band and X-band, but assume they are in lower orbit. That would explain how it can work for you.


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