We have a Comdial MP5000 phone system, and we have a branch office using the EP300 SIP phones over a VPN.
Ocasionally we get some scratchiness on the line, and I was told to turn on QoS in our Cisco 2811 routers on both sides. Which protocal should I use within QoS?
I see rtp audio, h323, rtcp, rtsp, and a few others. i was told that h323 wont work.
Thank you.
Your router needs to be either SIP aware or capable of picking up the precedence tag. I don't have my notes in front of me but if I remember correctly, the packets leaving the EP300 phones already have a precedence tag.
Thank aweaver.
I talked to my IT consulting company, and they said that I need to find out what the DSCP marking is, which i believe is the precedence tag you mentioned.
I figured out that rtp audio, h323/rtcp don't work. In my router rtp audios DSCP marking is just default, but h323/rtcp's DSCP marking is cs3. If you know what the DSCP marking is then i can add it.
Do you by chance know what that might be?
Update:
I found the DSCP for the EP300 SIP phones, and it is DSCP 40(cs5), but know I need to find out what port the phones use.
Anybody know what port they use?
The SIP protocol is not port specific. The port is negotiated for each call.
That is why a VPN or SIP-aware router is required, because port forwarding can't be really used to establish the connection.
Does that mean if I have a sip aware router I do not need a vpn?
Unfortunately I don't know the first-hand answer to that, since I've only done it with a VPN. Hopefully someone else who has used a SIP-aware router can answer that.
ComdialJim
As far as I know, the answer is "No." Sip aware allows for identification of SIP packets for QOS. It cannot allow for a peer to peer connection between two private IPs on disparate networks.