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VOIP

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mlngo2020

Technical User
Joined
Nov 11, 2002
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MY
Hi,
We are now in progress of configure Cisco 3600 & 2600 to enable the VOIP. We have a 32K leased line and we want to allocate 16k for data and the remaining for voice/fax. We have no problem if only data or voice is using but when both is running, I'm facing very bad quality voice. We tried enable the RSVP but no success. Or I can use ip precedence command. Please help.

Thanks,
Walau
 
32K as in 32Kbps? My recommendation, don't waste your time..

That amount of bandwidth isn't really enough to successfully implement any VoIP...

with your Fax, you must run the G711 codec which requires 85Kbps including all of the overhead.. with IP RTP header compression you could get it down to about 64Kbps though..

like I said though. Don't waste your time..


BuckWeet
 
Hi,
Our requirement here is a voice/fax line. One at a time and meanwhile we may need it for file transfer (50K perday) that'a all. Currenly, I can connect it through FXO interface and talk to remote site without any problems. What we want to achieve here is to control the bandwidth and let this ONLY voice/fax line have a higher priority.
Please advice,
Thanks.
 
As I said before, you have to have G711 Codec (also fax-relay) to run faxes with VoIP.. so you would in reality need link that could give you a dedicated 128Kbps (since they come in chunks of 64Kbps)


BuckWeet
 
Hi,
As I said, I have no problem with data, fax or voice if we use it one at a time either voice or fax or data transfer. But, when I use voice and data together, I will facing very bad voice quality.
Please advice,
Thanks.
 
buckweet, why are you saying "don't waste your time"? Is it because you don't think VoIP is not a mature enough technology at this point to implement and there will always be quality issues, or is it because the amount of bandwidth he's trying to use is too low? It sounds like the latter, but I wanted to make sure. We're thinking about replacing our old AT&T G3Si with VoIP next year, and was just wondering.
-Thanks
 
Its because his bandwidth is too low to run anything..

To run fax with VOIP you must use the uncompressed codec..
With all the overhead it'll take the call up to about 80Kbps or so.. He has 32Kbps.. thats not enough. A single call at G729 without IP header compression is around 26Kbps.. If he even took the voice down to G723, with the overhead it'll run about 12Kbps.. Still only leaving 20Kbps, which isn't much at all. In the end he wants to run FAX/VOICE/DATA across a 32Kbps pipe.. You could do the voice and data, and may get good results. But FAXing won't work..

I do feel VoIP is a mature technology. Thats what I do for a living. I install converged communications systems. I work on AVAYA, CISCO, and NEC IP telephony systems.. And they do work..


You're talking about replacing that G3SI, all I can say is upgrade it.. AVAYA cannot be touched with it comes to features.. Cisco Callmanager is lacking in that very much..
You're G3SI could be upgraded to support IP telephony. Depending on your version of system now, you might just need to upgrade the processor, the main cabinet, and throw in a Media Processor and Control LAN board and thats all.. Don't get me wrong, Callmanager is coming on strong and fast. But for you, I'd just upgrade it since you have all that infrastructure already.


There are plus and minuses to each system, which I'd be glad to discuss with you, if you have any questions..
 
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