View Full Version : options for remote extensions???

12-22-2008, 12:16 PM
Hi !!! here´s my problem: I nedd to join 5 ip telephones thought internet, which scenaries can I deploy to fix this problem??? my client has only PSTN lines without no SIP lines and an ADSL conection to wan. Those extensions will be in a branch office. Thank you for your help!!! I'll wait for your response soon!!!


12-22-2008, 02:08 PM
Omar, you have a few considerations to explain to the customer.

They may have a DSL connection that is fine for internet with PC's but they may not have what it takes for bothway SIP trafic.. ie

1500k / 256k DSL connection is fine to a point. that is ... you have a 256k up stream which is good for 1 x 711u/a connections for sip at any one time providing no one on the network is sending at the same time.

If you have a 512k / 128k then only 0 x 711u/a connection is possible at any one time.

A 256k / 64k = 0 x calls.

If you have a symetric service ie..

256k / 256k then 0 x SIP at 711u/a , 512k / 512k then 3 x SIP at 711u/a

The above I have found to be what actually works in the field for any IP system.

I have had companies complain about patchy broken up telephone calls in the past and when I looked at their configurations I have found they were trying to push 4 or more G711u/a calls down a 512k symetrical pipe.

I showed them the statistics for both way communications and explained what could be achieved. They ended up buying G729 licenses to cater for more calls ( aka Asterisk ). The other alternative would have been to increase the pipe which would have allowed the same at the higher codec.

You might want to chech the following calculator out : http://www.asteriskguru.com/tools/bandwidth_calculator.php

Total bandwidth for 3 x 711u/a
calls over a 512k symetrical
(incoming and outgoing):
477.76 Kbps
0.47 Mbps
59.72 KBps
0.06 MBps

<End Waffle> ;)

If you understand what is needed for the internet side then you only have the connectivity left . ie the SIP extensions on the WAN port.

Providing you have 3 x SIP extension lines available to be used as remote extensions then it is a matter of activating them as that type of service and you should be up and running.

Now for softphones - you can buy the Epygi softphone licence this is the best option when you need to monitor extensions remotely for the condition of the telephones at the office or if you dont need that then you could use a generic softphone like Counterpaths XLITE. The other alternative is to use SNOM 300 telephones ( SNOM are great when it comes to remote extensions and will make it easier to implement )

If all else fails - send David a PM :D