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WAN QoS (Cisco)

When working with a remote link, bandwidth can be limited and expensive. QoS becomes a requirement in these situations. Genesys verified the following configuration on a Cisco Catalyst 3640 and a Cisco Catalyst 2811 using a serial link configured at 1.5Mbs. In our test, the link was saturated with data traffic and we were unable to have clear telephone conversations. All calls experienced choppy audio.

After applying the QoS commands, the excessive data was delay or dropped from the queue on the gateways and the audio became clear. Below is the tested configuration with Cisco IOS version QoS configuration best practices. This example is based on a Cisco Catalyst 2811 and Cisco Catalyst 3640 in the following network scenario:

Make class maps to match voice packets and SIP signaling:

Start in privileged exec mode:

configure terminal
access-list 101 permit tcp any eq 8060 any
access-list 101 permit tcp any any eq 8060
class-map match-any voice
match ip dscp ef
exit
class-map match-any voip-control
match protocol sip
match access-group 101
exit

Note:
Using keywords such as sip match only standard IANA port numbers.

Make policy-maps and the bandwidth assignments.

Note:
Recommended values are for bandwidth assignment. Fair-queuing is for non-voice traffic.

From the global configuration mode:
```
policy-map voip-qos
class voip-control
bandwidth percent 2
class voice
bandwidth percent 70
class class-default
fair-queue
exit
```
Associate the policy to the WAN interface. This example uses the serial interface.

From the global configuration mode:
```
interface serial 1/0
service-policy output voip-qos
```

Many more tweaks are possible and there are many other methods you can use. This example gives you general guidelines. A WAN connection can also require shaping and policing.