On Oct 29, 2008, at 12:30 PM, David Gibbons wrote: > Fair enough, I guess I was concentrating on this line in Jerry's > message :) >> The only reason I can think of not to is to eliminate the cost of >> the second cable. > > I believe you're mistaken about the QOS though. >> QoS is not required on lightly loaded links and will do nothing for >> you on over loaded ones. > > QOS will absolutely allow voice traffic to pass with priority over > heavily loaded links -- this is in fact the reason that it would be > implemented. Obviously giving priority to the voice traffic on these > heavily loaded links serves to mitigate both latency and jitter. > >> The concern is almost never one of taking bandwidth away from the >> desktop, but one of the desktop taking bandwidth >> (especially by introducing latency) away from the phone. > > Agreed -- but with VLAN tagging and QOS, the issue of how much > bandwidth the desktop uses and/or needs becomes moot since the phone > is given priority. > > Dave > > David Gibbons wrote: >> Two separate networks? Did I miss something? I feel like I'm taking >> crazy pills! Two separate physical networks means twice the hassle, >> twice the maintenance, twice the cost, twice the headache. Not to >> mention the fact that the whole idea of VOIP is to simplify IT and >> focus on converging data and voice networks. >> >> This is what VLANs and QOS do best. I dare say it's what they were >> designed foe. I can't think of any reason that I would ever >> recommend two ports per desk to support telephony -- ever. It's >> ludicrous to think that two ports will be better than one if we're >> setting up our VLANs and QOS properly. A phone takes very, very >> little bandwidth away from the desktop and a decent one will >> support tagging its frames for the alternate voice VLAN. >> >> --snip-- >> In almost all cases it is much better to have two seperate networks. >> This may be impractical in some smaller installs, but in any office >> setting we always do this. The only reason I can think of not to is >> to >> eliminate the cost of the second cable. >> --snip-- >> > > > That's two _logically_ separate networks. The key point is that the > "last yard" cable to the phone is not shared with the computer. > The issue is not a lack of bandwidth but that the phone has to try and > get its little packets inserted between the massive packets of a > database lookup or file transfer in a timely manner (latency and > jitter). > > You might get away with a single logical network on a smaller site > or a > larger one with very light traffic. > > QoS is not required on lightly loaded links and will do nothing for > you > on over loaded ones. I only use it on WAN links where bandwidth is > more > expensive.
Allow me to clarify. Yes I do advocate seperate cable runs for phones and computers. Do not care if they both use a single switch as long as they are VLANd on seperate paths, either port based or tag based. And before everyone starts up again - :) - let me say that YES, I do install single cable fully integrated systems - when I manage the network. If I remember the OP was looking for real world examples and guidance. In the real world, just last week I picked up a new customer, drove 6 hours to a branch office of theirs that kept complaining about voice performance, and threw out the hub I found they had installed when they moved into their brand new building. Had a nice new switch - which I was told about - for their pc's. But all phones were on a hub - which I had not been told about. The new switch had been sent down to plug the phones into, but yeah. So in the real world I really like the KISS principle. Of course if there are qualified data folk ALWAYS makeing sure network is setup properly then feel free to disregard. _______________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
