[Asterisk-Users] Should I choose DSL @ 1.5 or a full T1?

[Nir Simionovich]

Damon,

  I have no idea where you are getting your information from, but what 
you said makes no sense.
DSL based lines, be it ADSL or SDSL, are based upon a connection 
technology in the ATM
family. As a result, the upstream and downstream of the connection can 
be controlled seperately.
If someone offers you a 1.5 SDSL connection, it doesn't actually mean 
that you have 2x768kbps,
it may actually mean that you have 2x1.5Mbps. However, that speed is 
only towards your internet
provider, what you get beyond that point would be bound to your ISP's 
SLA and contract.

  Now, E1 and T1 lines are based upon a channel based connection, which 
means you get a line
with X number of data lines and a single control/signalling line. On T1 
it means that you have 23
lines dedicated for Voice/Data (each is 64kbps) and a single signaling 
line (64kbps). Now, lets
do a little math (23+1)*64 = 1536kbps = 1.536Mbps, hence the speed for a 
single T1 circuit.
Now, if you have a T1 installed, and you are currently using 512kbps of 
upload, it means that you
are physically using 8 lines out of the 23 data lines for uploading. You 
can then use the rest to what
ever purpose you want, but while those lines are in play, you won't be 
upload another 512kbps on
the same lines. The reason for that is that each of these lines operates 
on a seperate Time Slot
within the physical layer. Once a Time Slot is taken for a specific data 
flow, it can't be used for another
data flow.

  This actually means that a T1 will give you a shared 1.5Mbps towards 
your ISP, with speed that
vary on the upload and download, according to your usage. While when 
using a DSL, your quality
of service for the connection to the ISP is described by the policy of 
connection. In many countries
(eg: Israel, Turkey, China, UK), DSL lines are actually ADSL lines, 
where the downstream is around
1.5Mbps while the uplink is around 128kbps (just enough to do a little 
VoIP). Last time I was in the
UK, about 4 weeks ago, I noticed they are now selling 8Mbps ADSL 
connection to your house,
however, the uplink is 512kbps.

  I would suggest that you get all the information from your providers 
regarding the type of services
rendered on the SDSL line, and make sure that it's the right one for you.

Nir S


Damon Estep wrote:

>You are aware that DSL (even SDSL) is half duplex and a T1 is full
>duplex, right?
>
>1.5m sdsl can only do 768 sustained duplex, or 1.5 out 0 in, or 0 out
>1.5 in. a T1 will do 1.5 in and 1.5 out sustained.
>
>This is due to a separate transmit and receive path on a t1 and a shared
>path on sdsl.
>
>The s in sdsl means symmetrical, not duplex, that is that the signaling
>rate is the same in either direction, but still half duplex.
>
>For VoIP a t1 is worth double what a 1.5 sdsl is because of the duplex
>nature of the traffic, unlike most internet that is download-centric.
>
>-----Original Message-----
>From: asterisk-users-bounces at lists.digium.com
>[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Wiley
>Siler
>Sent: Monday, June 13, 2005 9:43 AM
>To: Asterisk Users Mailing List - Non-Commercial Discussion
>Subject: RE: [Asterisk-Users] Should I choose DSL @ 1.5 or a full T1?
>
>Speakeasy SDSL Is 1.5 Megs, is business class (so you get an SLA) and
>only costs around $100 per month. 
>
>W
>
>-----Original Message-----
>From: asterisk-users-bounces at lists.digium.com
>[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Robert
>Goodyear
>Sent: Friday, June 10, 2005 7:02 PM
>To: Asterisk Users Mailing List - Non-Commercial Discussion
>Subject: Re: [Asterisk-Users] Should I choose DSL @ 1.5 or a full T1?
>
>
>On Jun 10, 2005, at 6:38 PM, Michael Welter wrote:
>
>  
>
>>Barton Fisher wrote:
>>    
>>
>>>I'm looking to expand my bandwidth for my Asterisk PBX.  Why should I
>>>      
>>>
>
>  
>
>>>choose a T1 over DSL for my asterisk server?  I found someone 
>>>offering T1's for $290 a month + Loops or 3 Meg for $561 a month + 
>>>Loops.  Is this a good deal?
>>> Thanks
>>> Bart
>>>---------------------------------------------------------------------
>>>-
>>>--
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>>>      
>>>
>>Where are you located?  What CLEC gives you a T-1 for $290?
>>
>>    
>>
>
>FWIW I provisioned a PRI and a DS-1 for $300 each. Don't know if I'm
>getting a break for having a voice and a data circuit broken out from
>one fiber drop, but that's what I'm paying here in Orange County. Also,
>I had a business cable modem before, which was *allegedly* not shared
>for business customers (suspicious) and the throughput was a roller
>coaster, as was the latency. The DS-1 cleared all that up.
>
>/rg
>
>Robert Goodyear
>Brand Up LLC
>http://www.brand-up.com
>
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