VoIP and WAN Bandwidth

yes. but the advantage of hosting it yourself is you can depend upon your uptime etc and know exactly whats going on.
we've only had one outage in the last two months (we've only had it two months) but it was a pain in the rear while it was down!
 
Right, I just need to get a little bit more of an understanding around hosting it yourself.

So effectively, you get some hardware in that allows you to convert a VoIP call from IP to PSTN?

Doesn't this mean you are no longer using an internet link for the call though?

Bare with my guys I really don't know too much about this, and most information I find seems to be around home-consumer type VoIP.

Thanks for the help so far :)
 
So you effectively use one 64kbit ISDN line, or a paired 128kbit line for one voice conversation, depending on the codec you select?

I'm guessing in theory then, renting an ISDN line and using that for VoIP should be cheaper than paying for a typical phone call? Or have I misunderstood?
 
Ah I see. I was just thinking to a codec that was posted earlier that had an ethernet requirement of 93kbit/s.

I suppose this all gets a little more complicated it you wanted to secure communications over the ISDN link, is that even possible?

Am I right in thinking that by using the ISDN line for outgoing calls rather than paying BT or whatever, you're monthly telecomms bill could possibly be reduced.
 
Wardie said:
Ah I see. I was just thinking to a codec that was posted earlier that had an ethernet requirement of 93kbit/s.

I suppose this all gets a little more complicated it you wanted to secure communications over the ISDN link, is that even possible?

Am I right in thinking that by using the ISDN line for outgoing calls rather than paying BT or whatever, you're monthly telecomms bill could possibly be reduced.
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What do you mean by "secure comms over the ISDN"?

Are you talking anti-wiretap etc or IT security? There is no IT security as such over a breakout voice call to ISDN. Once it leaves its in BT's hands.

However for internal calls you can use VLAN's (for segregation) and stream encryption (for security) to better protect the IP element of your call.
 
VeNT said:
missunderstood, afaik you use one 64k data line as a phone line per outgoing line you want
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Thats correct. If you rented an ISDN2e line that would give you 2 "channels" meaning two simultaneous external calls at any one time. If a third was initiated then you would get a "line busy" error until a channel was available again.

we have 8 active ISDN channels (on an ISDN30 circuit) which is enough for about 50 staff (unless its a call centre!)
 
VeNT said:
we're running a simple enough system here atm and have a couple of softphones and a couple of hard phones too but we find that even with QOS when someone uploads anything the VoIP quality dies thats with a 350k/s upload speed (speedtest.net)
two concurrent calls work ok but again uploads/downloads make things evil.
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I can only surmise your QOS sucks, on 2Mbit SDSL we can run 10 simultaneous calls and get 1.4Mbit download, flawless quality. Never been a problem, works for dozens of sites...
 
Wardie said:
If QoS is setup correctly surely you shouldn't really have any problems with people downloading at the same time (within reason and the router not being overloaded)
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Correct, certainly with Cisco QOS configured correctly you will no problems at all no matter how many people try to download or whatever. I've never yet managed to overload the router at a site doing basic QOS, I set out policy to use nothing less than a 2800 or 3800 for that sort of work but I think it'd work fine on an 1841 if you tried.
 
bigredshark, i'm going to drop you an e-mail this evening :)

I'm still not too sure I understand all this renting ISDN lines for outgoing calls, can is it really be cheaper than just having an ISP doing this for you?

I like to understand the technology and i'm not too sure what's going on here... Someone do a topology in paint ha-ha
 
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basicaly ISDN lines are just like normal phone lines but are IP based rather than PSTN and have a higher quality of signal
 
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I've got no special recommendations on codecs really, I just do the QOS on the core these days, my days of playing with callmanager are behind me.

Sure you can just have SIP/H323 trunks to your provider for voice calls but if you loose your internet you loose your phones, we use SIP trunks as our primary but the ISDN is there as a backup. We couldn't afford to loose both in one go (even with redundent internet connections the risk is too great)
 
So ISDN is a safe bet and generally more reliable? Is it often cheaper though? I'm assuming you can only use 1 ISDN line per call? So even if you're using a codec that requires 32kbit/s, you'll have to use one 64kbit ISDN line?

I need to do some reading as i'm not entirely sure how someone from the outside calls a VoIP phone. I'm guessing the basics of it are they dial your number, and the CallManager then routes it to the associated IP phone, in a similar fasion to NAT?
 
yeah, the PBX rings every phone logged into that extention (you can have other calling rules like if its not answered in 5 rings it moves to the next group or all phones or voicemail)
 
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