Re: VOIP Troubles
Wait for 12.1.5(T) Cisco IOS. [skipped] follow) here come the questions: 1.Has anyone else implemented VOIP in slow links successfully? 2.Is anyone else having QOS problems with their VOIP implementations? 3.Do I need to prioritize the voice traffic through the local network? 4.Has anyone tried turning off traffic shaping and letting the voice and data compete for bandwidth? Thanks in advance for your feedback! Thanks, Chris Boyd, CCNA Network Support Alex Lee, Inc. 120 4th Street SW Hickory, NC 28601 (828) 323-4103 http://www.alexlee.com -- --- WBW, xander CCNP+Voice, CCIE very soon :-) _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: VOIP Troubles
You can also try calculating bandwidth at www.erlang.com John Deatherage wrote: Some things that might help: 1. Are you using CODEC like G.729 that works at an 8Kbps bit rate? If not, you'll be hating life.2. Bandwidth at full rate Multilink PPP (MLPPP) or FRF.12 will still be 17.2kbps.3. You need QoS, even if you can burst to port speed at 56kbps.4. Consider LLQ for Frame Relay for your QoS, which is now supported in IOS as of 12.1(2)T. We had to use this to get good voice quality on a moderately saturated FR link with a 1.544mbps CIR.5. You may need QoS on your LAN if the links are congested near the 3640. Look at QoS as an end-to-end solution.6. Perform ping tests from the 3640 to your remote sites to get a better idea of how many ms the round trip is. Try pings from both sides. Things to keep in mind:- VoIP overhead will kill you - you need to do testing to figure out exactly how much bandwidth you are using.- Good luck doing this over 56kbps, even if you use the full line. - Original Message - From: Chris Boyd To: [EMAIL PROTECTED] Sent: Friday, November 10, 2000 1:08 PM Subject: VOIP Troubles All right guys I need some help I have been working with Cisco for a while now on a VOIP issue. The problems lies in both call disconnects and voice distortion. We have followed all the steps for traffic shaping (QOS) and rtp header-compression but these do not seem to help. We have 150 remote sites all running 2600's with FXS modules that all come back into the host site where we have 2 7206's. Each of these links are 56k frame-relay links with 16k CIR running very few applications mostly small transactions and Citrix clients. The call must then traverse two internal Ethernet segments, routing through our 6509 backbone switch and then into a 3640 before hitting the PBX. Cisco seems to think that we need to increase our bandwidth to support the voice traffic, however, that is not something I have been able to sell to the "powers that be". We sold this idea on cutting cost and in our estimations for upping the CIR to even 32k will be significant cost increase. Right now I am shaping to 16k with an 8k committed burst so at any one time I should be able to burst to 24k. Assuming that I am able to burst to port speed (56k) why would I have call distortion unless there is some latency coming through the ISP's switch? We also have another company site that also comes back in this way and we have no problems with those calls.O.K. that being said (and hopefully not too confusing to follow) here come the questions: 1.Has anyone else implemented VOIP in slow links successfully?2.Is anyone else having QOS problems with their VOIP implementations?3.Do I need to prioritize the voice traffic through the local network?4.Has anyone tried turning off traffic shaping and letting the voice and data compete for bandwidth? Thanks in advance for your feedback! Thanks, Chris Boyd, CCNA Network Support Alex Lee, Inc. 120 4th Street SW Hickory, NC 28601 (828) 323-4103 http://www.alexlee.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: VOIP Troubles
Some things that might help: 1. Are you using CODEC like G.729 that works at an 8Kbps bit rate? If not, you'll be hating life. 2. Bandwidth at full rate Multilink PPP (MLPPP) or FRF.12 will still be 17.2kbps. 3. You need QoS, even if you can burst to port speed at 56kbps. 4. Consider LLQ for Frame Relay for your QoS, which is now supported in IOS as of 12.1(2)T. We had to use this to get good voice quality on a moderately saturated FR link with a 1.544mbps CIR. 5. You may need QoS on your LAN if the links are congested near the 3640. Look at QoS as an end-to-end solution. 6. Perform ping tests from the 3640 to your remote sites to get a better idea of how many ms the round trip is. Try pings from both sides. Things to keep in mind: - VoIP overhead will kill you - you need to do testing to figure out exactly how much bandwidth you are using. - Good luck doing this over 56kbps, even if you usethe full line. - Original Message - From: Chris Boyd To: [EMAIL PROTECTED] Sent: Friday, November 10, 2000 1:08 PM Subject: VOIP Troubles All right guys I need some help I have been working with Cisco for a while now on a VOIP issue. The problems lies in both call disconnects and voice distortion. We have followed all the steps for traffic shaping (QOS) and rtp header-compression but these do not seem to help. We have 150 remote sites all running 2600's with FXS modules that all come back into the host site where we have 2 7206's.Each of these links are 56k frame-relay links with 16k CIR running very few applicationsmostly small transactionsand Citrix clients. The call must then traverse two internal Ethernet segments, routing through our 6509 backbone switch and then into a 3640 before hitting the PBX. Cisco seems to think that we need to increase our bandwidth to support the voice traffic, however, that is not something I have been able to sell to the "powers that be". We sold this idea on cutting cost and in our estimations for upping the CIR to even 32k will be significant cost increase. Right now I am shaping to 16k with an 8kcommitted burst so at any one time I should be able to burst to 24k. Assuming that I am able to burst to port speed (56k)why would I have call distortion unless there is some latencycoming through the ISP's switch? We also have another company site that also comes back in this way and we have no problems with those calls.O.K. that being said (and hopefully not too confusing to follow) here come the questions: 1. Has anyone else implemented VOIP in slow links successfully? 2. Is anyone else having QOS problems with their VOIP implementations? 3. Do I need to prioritize the voice traffic through the local network? 4. Has anyone tried turning off traffic shaping and letting the voice and data compete for bandwidth? Thanks in advance for your feedback! Thanks, Chris Boyd, CCNANetwork SupportAlex Lee, Inc.120 4th Street SWHickory, NC 28601(828) 323-4103http://www.alexlee.com
Re: VOIP Troubles
1) Yes, and we had some of the same issues. The biggest was that we had tohard code the codec on all interfaces. For some reason the default codec G729ar8 wasn't always being selected or detected and since it's the default you can't hard code it. We had to opt for G729r8. We had point to point 56K circuits so it was much easier to deal with. Oh yea, we also tried to do a voice class to change the default codec for a whole router, but we had a couple of routers that ignored the voice class config, which is why we ended up hard coding every interface. 2) I think this is more an issue that IOS is a work in progress. We've always had to use an Early Deployment release to fix an issue. ( and in the process broke something else...) 3) Do it anyway. 4) Yep, and you'll be sorry you did. Even on full point to point T1's, I've seen issues. Just a suggestion, but have you considered putting voice cards in the 7206's and going VOFR? Rodgers Moore ""Chris Boyd"" [EMAIL PROTECTED] wrote in message 001d01c04b5a$6df29c50$[EMAIL PROTECTED]">news:001d01c04b5a$6df29c50$[EMAIL PROTECTED]... All right guys I need some help I have been working with Cisco for a while now on a VOIP issue. The problems lies in both call disconnects and voice distortion. We have followed all the steps for traffic shaping (QOS) and rtp header-compression but these do not seem to help. We have 150 remote sites all running 2600's with FXS modules that all come back into the host site where we have 2 7206's.Each of these links are 56k frame-relay links with 16k CIR running very few applicationsmostly small transactionsand Citrix clients. The call must then traverse two internal Ethernet segments, routing through our 6509 backbone switch and then into a 3640 before hitting the PBX. Cisco seems to think that we need to increase our bandwidth to support the voice traffic, however, that is not something I have been able to sell to the "powers that be". We sold this idea on cutting cost and in our estimations for upping the CIR to even 32k will be significant cost increase. Right now I am shaping to 16k with an 8kcommitted burst so at any one time I should be able to burst to 24k. Assuming that I am able to burst to port speed (56k)why would I have call distortion unless there is some latencycoming through the ISP's switch? We also have another company site that also comes back in this way and we have no problems with those calls.O.K. that being said (and hopefully not too confusing to follow) here come the questions: 1. Has anyone else implemented VOIP in slow links successfully? 2. Is anyone else having QOS problems with their VOIP implementations? 3. Do I need to prioritize the voice traffic through the local network? 4. Has anyone tried turning off traffic shaping and letting the voice and data compete for bandwidth? Thanks in advance for your feedback! Thanks, Chris Boyd, CCNANetwork SupportAlex Lee, Inc.120 4th Street SWHickory, NC 28601(828) 323-4103http://www.alexlee.com
