SRW Series QoS configuration for VoIP

[Haitham Kassas]

Hello Cisco experts,

I have SRW224G4 switch in an office connected to the internet through port1, Asterisk server through port 9, Internal computers through ports 16-24.

Currently, voice is cutting in the inbound direction when computer users are using Internet. I am trying to make some QoS configuration in which remote IAX2 phone, which uses UDP port 4569, will not be affected by Internet usage made by internal computers.

I have logged in to the switch management webpage, I found a section for (QoS), but I need some help in specifying which parameter should I configure.

Internet connection speed is 1mbps DL / 512kbps UL. I can configure Asterisk to mark packest with some TOS if required.

[tcsillag83 · Accepted solution]

One way to do it would be to configure Asterisk to assign a DSCP value of 46 to voice packets.

Then on the SRW224G4, use:

CoS Settings tab / QoS mode: Basic

Basic tab / Trust mode: DSCP

That would give priority to voice packets inside your network.

Possible problems:

• your ISP will most likely clear DSCP markings on packets going out of the network
• rare case: your ISP might charge you more for packets marked with DSCP 46 (not likely on an ADSL connection)
• bottleneck will be the ADSL router, so if possible, you should implement QoS based on DSCP on that device
• if some PC based software uses DSCP markings, it'll get priority also

Hope this helps!

Cheers,

Tamas