On Thursday 27 July 2006 15:50, Henry Coleman [VoIP-PBX.ca] wrote: > A DSL and Cable broadband (with load balancing) 1.6 Mbs upstream (2x > 800kbs) - cost $100 per month
Unless you've actually *done* proper load balancing across multiple connections you're simply pissing up a rope with numbers like that. I've been using redundant internet links to multihomed address space at a colocation facility in order to improve reliability of connections for a while now. While you can get some increased bandwidth out of it (especially if it's for different streams of data) it is NOT as simple as "I have two 800kbps uplinks, that gets me 1600kbps upstream with two of 'em." Even with route caching turned off, the Linux kernel caches routes to some extent. (of course I'm assuming Linux here... If you're not then you could be blowing my entire theory out of the water :-) Also, as far as I am aware, Bell Canada's DSLAMs do not support MPPE which would allow true channel bonding. (This is coming from my brother, who is a network engineer for the data side of Bell) - it is possible that the equipment can handle this but he has seen no evidence of it actually being provisioned. I too ran the numbers a while ago... Let me see if I can dig it up... nope. The kwlug forums disappeared. Basically my numbers came down to this: A decent internet connection and an "IP PRI" or DIDs from a *reliable* provider will save you boatloads, even if you pay per-minute for local and incoming calls. I'll see if I can recreate the numbers again tonight, but my standard recommendation to business these days is that if they can't get a PRI, they can gang up on my PRI on a "close hop" network. It's not as stupidly failsafe as 1FL lines, but the "artistic license" that can be taken with the call routing and integration with your existing data network is phenomenal. Also if you provide a simple IVR with voicemail on the box on the PRI itself tempoary outages can be pretty painless. I typically recommend a single 1FL for 911 and security, with fax coming in via t.38 or a fax reception service. With a "close enough" network you could get away with FOIP that does not use t.38 (I've been doing this for 2 years now, but I am cheating.) > As a rule of "thumb" 23 channels would support 50 to 75 extensions > Being conservative, a good DSL or Cable Broadband connection should > be able to handle 10 simulatanious calls 23 lines for 50-75 extensions? You're assuming that every other to every third person in the office is on the phone at any given time? I suppose it depends on industry and office type... here (Benshaw) we have about 30 people in the office and I think that we've hit a high water mark of about 8 simultaneous calls over the last 24 months, when we moved to our new facility and every call came in over Asterisk. We have a lot of sales and customer service people too... those are are two biggest departments. (quick numbers: 47k calls since January 6 2006, 60k calls if you include the small business we're sharing our PRI with. Approximately 286 calls a day.) Our PRI has only 15 B channels turned up. Your assumption that 800kbps is going to handle 10 calls is not very conservative, either. 80kbps "wire" bandwidth for a ulaw call and I would suggest that maybe 8 concurrent calls will get through with enough margin to not make me sweat or get complaints of choppy audio. :-) Trunking IAX2 will drastically reduce this, of course, as will moving to gsm or g729 for the voice codec, although I have found that some office-dwellers get very irate when their telephones sound as good as a good cell call. -A.
