Cisco 1720 / QoS question for VoIP services

[Superwormy]

Can the Cisco 1720 be set up to give priority to SIP/IAX connections for VoIP?

i.e.: If I have a huge file I'm uploading, and I'm making VoIP calls, I want it to throttle back the file upload so that VoIP gets the bandwidth/speed it needs. Is it do-able with a Cisco 1720?

 

[narzy]

I love Cisco questions in these forums, I'm surprised someone hasn't answered this one yet. Unfortunately I don't know if you can do it or not, I haven't played with QoS much, I know it can be done through the Cisco SDM on the 1841 routers but you have to tweak some IOS CLI stuff for VoIP after that...so I'm sure it is doable I'm just not sure how...

 

[drebo]

Per the Cisco Website, the 1720 does support QoS.

However, you shouldn't really have an issue unless your file upload has high TCP overhead or has tons of active connections (such as a bit torrent).

For reference, I've got a client with three locations and a single Asterisk server. Each location is connected to the main location via VPN over a 768K SDSL line, which is shared with both data and voice. We're able to accomodate many calls over the line in addition to their normal data traffic without much issue.

 

[jlazzaro]

i believe the 1720 does indeed support QoS, though you may need a newer image.

Originally posted by: drebo
For reference, I've got a client with three locations and a single Asterisk server. Each location is connected to the main location via VPN over a 768K SDSL line, which is shared with both data and voice. We're able to accomodate many calls over the line in addition to their normal data traffic without much issue.

whether you actually notice issues with voice calls or not is irrelevant. best practice, give preference to your bearer and signaling traffic. if not, itll bite you in the butt eventually.

 

[drebo]

Indeed. I didn't mean to imply that QoS is worthless...I was simply pointing out that normal data activity shouldn't impact VoIP traffic much, if at all.

 

[jhayx7]

Cisco AutoQOS

 

[p0lar]

Originally posted by: jlazzaro
i believe the 1720 does indeed support QoS, though you may need a newer image.

Originally posted by: drebo
For reference, I've got a client with three locations and a single Asterisk server. Each location is connected to the main location via VPN over a 768K SDSL line, which is shared with both data and voice. We're able to accomodate many calls over the line in addition to their normal data traffic without much issue.

whether you actually notice issues with voice calls or not is irrelevant. best practice, give preference to your bearer and signaling traffic. if not, itll bite you in the butt eventually.

The 1720 does support it, but the most difficult part doesn't lie in the QoS or even IOS selection, but a protocol inspection such that the IOS knows to prioritize the proper outbound UDP port selected when negotiating the RTP connection.

The two protocols operate in similar ways with respect to signaling, but IAX uses a single port for both the RTP and signaling, which makes NAT and QoS extremely simple. SIP generally uses UDP/5060 for its signaling, and attempts to negotiate between UDP 16384 and 32768 for its RTP stream on the terminating client. Some instances will use ports > 51k, but that depends on the protocol implementation.