VOIP experts please!

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ajf

ajf

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Not sure if this comes under 'if you have to ask...'

Anyway, another little project I want to look at is voip as my understanding is nil to zero.
I have read several articles though so think I am getting a general understanding and want to know if I have got it right.
This would be used at home for testing on a Virginmedia phone line.
I also have a 10Mb Virgin cable line with modem and router.

If I got a Linksys SPA3102 that will do the initial link between pstn and network - yes?
I was then thinking of using a software pbx such as 3cx - Am I on the right lines so far?
I believe this would then give me the opportunity to test internal extensions, attended calling etc?
I assume though, as I only have a standard pstn line I can still only use one external call at a time and no direct dialling to extensions?
Using the broadband line I assume I could also start using a VOIP provider? Can I then make two simultaneous calls - one via pstn and one via broadband?

I noticed here:
http://forums.overclockers.co.uk/showpost.php?p=18383338&postcount=208

He is using Cisco equipment. Does the 2611xm plus the NM-2v and VIC cards effectively do the same as the SPA3102 but on a grander scale?
Would I better off using Cisco (given its wide use) or starting off simply with the Linksys hardware?

Any advice appreciated or links to 'how to' articles, although did find a couple of useful ones already.

Thanks
Andrew
 
Anyone?
If I am completely confused in the above let me know:)

Andrew
 
I had pretty much the same setup when I first started tinkering at home, although my linksys was the SPA3100 model I believe. I used a derivative of Asterisk in the form of pbx in a flash and I would recommend reading through some of the articles on http://nerdvittles.com/ especially around the security side of things.

I started off with the linksys using my PSTN line, then I decided to add a VOIP only line using my (then) 5Mb ADSL line. I then took the plunge and went completly voip, got rid of the Linksys and bought a number from my VOIP provider for around £3 a month. The house phones I use are a Cisco 7911 flashed with SIP firmware and a Siemens Gigaset A580 IP DECT basestation/handset.

The Cisco phone is mainly for show next to my computer, but it works perfectly well. The Siemens handset is mainly for the WAF and also the fact the the base station registers using SIP to the asterisk server and then all the phones register with DECT to the base station. Works exactly like using a PSTN line, but cheaper calls.

In answer to a couple of your questions, yes if you only have the PSTN line as the incoming line you could only make or receive one call, but calls between different extensions would work fine. If you also had a VOIP provider you can make more than one call at once but also set what order you want things used in (e.g. PSTN first, then VOIP), also you may be able to make more than one call over the internet depending on your provider. I use VOIPTalk and I believe I can have 2 lines (in or out) active at once using them.
 
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Oh also if your Internet is heavily used, you may have to look at implementing some sort of QoS or traffic shaping to make sure your voice server always has enough bandwidth to take a call. I believe its something along the lines of 32Kbps for an uncompressed voice call.
 
The SPA3102 is fine for a PSTN gateway but do need quite a bit of tweeking to get right with regard to call quality. I have also used a grandstream GXW 4104 which will give you 4 lines and seems to give better call quality.

With regard to the number of calls yes the via the PSTN gateway this is just like using a normal phone so only one call the limiting factor for voip is down to bandwidth and you voip provider
 
TheKnat said:
Oh also if your Internet is heavily used, you may have to look at implementing some sort of QoS or traffic shaping to make sure your voice server always has enough bandwidth to take a call. I believe its something along the lines of 32Kbps for an uncompressed voice call.
Click to expand...

G.711 is 64kbps per direction. For a home network you are unlikely to saturate the bandwidth so I would not go out of my way to configure QoS (not best practice).

Personally I would configure Callmanager Express on the 2600 router (make sure you have enough RAM and flash to support it!)

I have a 2621XM (with the NM-2V and a 2 port FXO card) configured to use a CUCM 7 server hosted in a VM. I then use a SIP client on my mobile phone to make and answer calls from the landline. This was however mainly setup for training purposes to get used to the new interface before we implemented it at work.
 
Thank you. As it is more for testing than anything bandwidth is not likely to be an issue.

The Cisco route makes sense from a usefulness point of view but looking into it ypu start getting sucked in to ever more complicated issues.
Most of the routers I have looked at (2621xm mainly) seem to need extra flash and memory to use the CME - although I assume I can use other software such as Asterisk and 3CX?
I have also been told I may need advipservices IOS? i cannot find what that adds so not sure if it is a must for a small test setup?
 
I run c2600-advipservicesk9-mz.124-15.T13 on my 2621xm but what it had previously c2600-ipvoicek9-mz.124-13f was also fine. I mainly upgraded to have a look at vpn configuration. These can be downloaded from the Cisco site if you have a login otherwise they can be found.
 
As you said, the Cisco method would probably be more relevant but I found it harder to get into the cisco VoIP circle rather than the open source side of things. All comes down to why you want to do it.
 
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