I've seen this discussion before. The conclusion was, it is possible to route TDMoE through a VPN tunnel depending on the tunnel setup you are using (bridge + tunnel for example) however the latency would make it useless. TDMoE is designed for the same network. Unfortuanely I can't find a link for it, but I remember it distinctly.
Another, large issue, is that TDMoE uses T1 - style bandwidth constantly whether it is in use or not. Even if it were possible to route it, and even if the latency problem was solved, can you imagine your bandwidth surcharge of ~1.5Mbps constant? At the end of the day, emulating TDM through the use of IAX and a well written dialplan is totally the way to go. -----Original Message----- From: Steve Langstaff [mailto:[EMAIL PROTECTED] Sent: Thursday, January 26, 2006 8:16 AM To: Asterisk Users Mailing List - Non-Commercial Discussion Subject: RE: [Asterisk-Users] * point to point t1 solution? / alternatives Remember, however that TDMoE is TDMoE, not TDMoIP - it's not routable (unless you encapsulate it somehow, I guess). -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Bill Michaelson Sent: 26 January 2006 14:58 To: [email protected] Cc: [EMAIL PROTECTED] Subject: Re: [Asterisk-Users] * point to point t1 solution? / alternatives This has been an interesting discussion for me (except for the sniping). The last post led me, out of curiosity, to this wiki entry: http://www.voip-info.org/wiki-Asterisk+TDMoE I was unaware of this feature, and it looks pretty good. I've been pondering replacing some T1's by leveraging IP capacity but of course have run up against the QoS issue. My idea was different... I don't have production experience with precisely this type of application, but I ask for validation from this list. Pardon me for stating what is undoubtedly obvious to many... The key to assuring adequate performance in replacing a TDM link with IP is to assure that adequate idle time is reserved for voice on the IP segment(s) involved in the route. In this way, latency can be stabilized, and if maintained below a certain (arbitrary) threshold, performance can be deemed acceptable. The first step, of course, is to assure that the virtual TDM allocation does not exceed the available IP bandwidth (so leave a margin, which is huge in the example given). The next step is to use routers which respect the TOS field (however it is used; diffserv/whatever), and finally, to assure that no non-VoIP traffic can be injected into the path with higher routing priority. On a point-to-point link, a pair of typical Linux boxes can do all this. Given the original problem, I would place Asterisk boxes at either end of the link, and have them blend the ordinary traffic with the VoIP traffic (which would probably use IAX to relay calls between the T1s), while assuring (enforcing) that VoIP packets are marked as highest priority. There are varied ways of accomplishing this, and a good reference which I've used in the past can be found at: http://www.lartc.org/lartc.html Additionally, I think one could use the tunneling techniques described in that guide to encapsulate the non-VoIP traffic such that its packets' originally marked TOS values are preserved for transit outside the segment used for TDM emulation. In this way, that part of the segment bandwidth not required for VoIP would function as a dedicated link, allowing other prioritization of traffic such as interactive vs. bulk (or even other voice!), with the added advantage that it could use the reserved VoIP bandwidth when it is otherwise not required (albeit in the case of a T-1 over 10Mb, that's insignificant). Is this easier or harder than TDMoE as described? Does the TDMoE shared idle bandwidth? What about stability (I'm thinking of SW releases)? What other drawbacks or advantages are there? >Date: Wed, 25 Jan 2006 23:53:59 -0700 >From: "Damon Estep" <[EMAIL PROTECTED]> >Subject: [Asterisk-Users] * point to point t1 solution? >To: "Asterisk Users Mailing List - Non-Commercial Discussion" > <[email protected]> > >Can anyone point me to a reference or sample config for bypassing a >nailed up (point to point) t1 between two PBXs with asterisk and a pair >of t1 cards? > >Right now I have 2 Nortel norstars connected to each other via a leased >line t1. I also have a solid 10mbps low latency microwave link between >the 2 sites. > >My goal is to run an asterisk box at each end with a t1 card and >Ethernet card to act as a TDM<>SIP gateway to bypass the nailed T1 in a >relatively dumb configuration, with the goal of migrating off of the >norstars eventually. > > In past situations I would have done this with a pair of Cisco routers >with T1 interfaces in them but in this case I want to get asterisk into >the picture as an eventual replacement for the norstars. > > > > _______________________________________________ --Bandwidth and Colocation provided by Easynews.com -- Asterisk-Users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users _______________________________________________ --Bandwidth and Colocation provided by Easynews.com -- Asterisk-Users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users _______________________________________________ --Bandwidth and Colocation provided by Easynews.com -- Asterisk-Users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
