Pardon my ignorance, but I was hoping someone could clear up something for me. - For a few POTS lines, digium has a single port card for that, or a T1 card to a channel bank. - For 10 or more lines, digium has a T1 or E1 card for that too based on PRI channels - For 100's to 1000's of lines, I suspect a soft-switch is in order??? A traditional phone company will sell: - POTS lines for small quantities - PRI channels over one or more T1 lines - ??? for 100's to 1000's of lines??? Unlike PRI channels, we are all able to get better than 64k using a variety of different codecs. So how is it possible to get more out of a link/bridge (pardon my lack of proper technical terms) to the public phone systems?? If a codec can drop a channel down to 8k, then a single T1 should be capable of supporting nearly 184 concurrent calls right?? I suspect this is where a softswitch comes in, but it is not clear to me. Do you call up a phone company and ask for a block of T1's using SS7 signalling, or MGCP, and plug it into a softswitch?? If that is even partialy correct, does that decrease the cost (HERE IS THE KEY) for access to public lines? I'm sure the softswitch (again assuming I'm partially right) costs around $100k. Asterisks shows support for MGCP channels, does that help in this fuzzy scenario? Perhaps I am way off, but I do hope someone can clarify some of these things for me, or at least get a laugh at my quesions and wording <grin> Cheer, Darren
Darren, The answer (unfortunately) is "sort of" and "it depends" ----- Definitions ----- LEC = Local Exchange Carrier CLEC = Competitive LEC IXC = Interexchange Carrier (LD company) ----------------------- In most cases a traditional phone company is going to want to hand off TDM (circuit switched) services to you. This is true whether you are a normal business or a CLEC/IXC. If you are a CLEC with SS7 connectivity (and an assigned point code) they will hand off T1s and do the signalling out of band over the SS7 connections. In-band signalling is possible, but not common anymore. I know that in the late-90s in SouthWestern Bell land they often wanted to hand off calls from their 1AESS switches in MF format rather than SS7. A typical business would be handed either in-band signalled T1s or PRIs. I don't know of any cases where private enterprises have gotten their own point codes and SS7 connectivity, but someone else may have an example. In the market now are firms which offer the end-user individual or business VoIP origination/termination of both local and LD calls. While the customer of these firms sees a VoIP interface I would bet that the hand-off to the terminating LEC is still done via TDM circuits. This may change in the future as the IXCs complete their transitions to VoIP internal trunking networks. I don't expect the LECs to change rapidly though. Their cost-recovery and depreciation models are based on their switches lasting a loooooooong time. If anyone has an example of a traditional US LEC offering VoIP hand-off and termination I'd love to hear about it. I just haven't heard of a real-world example yet. Depending on the size of the deployment, a softswitch may be the way to go for hand-off to a LEC. Given the size of typical carrier grade softswitches though, I'd think that is something you'd only be looking at if you were a very large enterprise or some type of carrier. The size of the enterprise and the mix of traffic would determine where the crossover is between a softswitch and another solution. Actually, you could make a case that * is a softswitch. Really you're just talking about scale here. The big question is when does a * server run out of gas? If you have 4 quad-PRI boards in a system you can provision 368 trunks via PRIs. Depending on the average length of call that is quite a bit of trunking. I've seen CLEC trunk-groups to the access tandem that were smaller than that. Hopefully this answers some of your questions..... THX/BDH On Fri, 2003-11-07 at 20:05, Darren Martz wrote:> Pardon my ignorance, but I was hoping someone could clear up something for > me. > > - For a few POTS lines, digium has a single port card for that, or a T1 card > to a channel bank. > - For 10 or more lines, digium has a T1 or E1 card for that too based on PRI > channels > - For 100's to 1000's of lines, I suspect a soft-switch is in order??? > > A traditional phone company will sell: > - POTS lines for small quantities > - PRI channels over one or more T1 lines > - ??? for 100's to 1000's of lines??? > > Unlike PRI channels, we are all able to get better than 64k using a variety > of different codecs. So how is it possible to get more out of a link/bridge > (pardon my lack of proper technical terms) to the public phone systems?? If > a codec can drop a channel down to 8k, then a single T1 should be capable of > supporting nearly 184 concurrent calls right?? > > I suspect this is where a softswitch comes in, but it is not clear to me. Do > you call up a phone company and ask for a block of T1's using SS7 > signalling, or MGCP, and plug it into a softswitch?? If that is even > partialy correct, does that decrease the cost (HERE IS THE KEY) for access > to public lines? I'm sure the softswitch (again assuming I'm partially > right) costs around $100k. > > Asterisks shows support for MGCP channels, does that help in this fuzzy > scenario? > > Perhaps I am way off, but I do hope someone can clarify some of these things > for me, or at least get a laugh at my quesions and wording <grin> > > Cheer, > Darren > > _______________________________________________ > Asterisk-Users mailing list > Asterisk-Users@lists.digium.com > http://lists.digium.com/mailman/listinfo/asterisk-users >
Thanks Brian, and thanks again for the included definitions <grin> - that helped too. Your comments are really helping clear many questions. I suppose our intensions are to become an IXC. So if my local carrier is sporting old technology, they'll provide TDM services. So if I understood you correctly, the "in-band signaling" is typically SS7, and the alternative is typically PRI? Sounds like one carrier more of the call management tasks and the other is a more finished product - and you pay more for each PRI channel right? I know our local carrier recently upgraded the entire LD infrustructure to a Nortel VOIP solution (Telus in Canada). Perhaps they could provide VOIP channels as you indicated instead of TDM services. FYI: Telus spans across the entire Canada, and are a major carrier. They are also a major pain to deal with, and I'm not sure they'd be willing to sell a VOIP package. Hmmm.... if our target is to manage a maximum of 2000 concurrent calls (for arguement sake), I suppose a softswitch is overkill. Although I did notice that companies like MetaSwitch operate as small as 400 lines. So if our only option was a TDM based solution, and we used Asterisk as our "softswitch", what signaling would be ideal to keep the cost at a minimum? I don't recall Asterisk supporting SS7. Besides I read the Telco's only allow SS7 products they have tested and certified. I wonder what would happen if the carrier provided VOIP channels. I suppose it would still use T1s, but with what form of signaling? Cheers, Darren> Subject: Re: [Asterisk-Users] Softswitch > From: Brian D Heaton <bdheaton@c4i2.com> > To: asterisk-users@lists.digium.com > Organization: bdheaton@c4i2.com > Date: Fri, 07 Nov 2003 21:26:49 -0500 > Reply-To: asterisk-users@lists.digium.com > > Darren, > > The answer (unfortunately) is "sort of" and "it depends" > > ----- Definitions ----- > LEC = Local Exchange Carrier > CLEC = Competitive LEC > IXC = Interexchange Carrier (LD company) > ----------------------- > > > In most cases a traditional phone company is going to want to hand off > TDM (circuit switched) services to you. This is true whether you are a > normal business or a CLEC/IXC. If you are a CLEC with SS7 connectivity > (and an assigned point code) they will hand off T1s and do the > signalling out of band over the SS7 connections. In-band signalling is > possible, but not common anymore. I know that in the late-90s in > SouthWestern Bell land they often wanted to hand off calls from their > 1AESS switches in MF format rather than SS7. > > A typical business would be handed either in-band signalled T1s or > PRIs. I don't know of any cases where private enterprises have gotten > their own point codes and SS7 connectivity, but someone else may have an > example. > > In the market now are firms which offer the end-user individual or > business VoIP origination/termination of both local and LD calls. While > the customer of these firms sees a VoIP interface I would bet that the > hand-off to the terminating LEC is still done via TDM circuits. This > may change in the future as the IXCs complete their transitions to VoIP > internal trunking networks. I don't expect the LECs to change rapidly > though. Their cost-recovery and depreciation models are based on their > switches lasting a loooooooong time. If anyone has an example of a > traditional US LEC offering VoIP hand-off and termination I'd love to > hear about it. I just haven't heard of a real-world example yet. > > Depending on the size of the deployment, a softswitch may be the way to > go for hand-off to a LEC. Given the size of typical carrier grade > softswitches though, I'd think that is something you'd only be looking > at if you were a very large enterprise or some type of carrier. The > size of the enterprise and the mix of traffic would determine where the > crossover is between a softswitch and another solution. Actually, you > could make a case that * is a softswitch. Really you're just talking > about scale here. > > The big question is when does a * server run out of gas? If you have 4 > quad-PRI boards in a system you can provision 368 trunks via PRIs. > Depending on the average length of call that is quite a bit of > trunking. I've seen CLEC trunk-groups to the access tandem that were > smaller than that. > > Hopefully this answers some of your questions..... > > THX/BDH > >