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Page 33 | AlliedWare™ OS How To Note: VPNs for Corporate Networks
branch office
1
How to prioritise outgoing VoIP traffic from the branch
office
1
router
Add the following steps after step 11 on page 22.
In this example, the originating VoIP appliance has marked VoIP traffic and VoIP signalling
packets with DSCP 48.
create classifier=48 ipds=48
VoIP data packets are small. They can be significantly delayed by big packets on the WAN
port, especially on slow links. Therefore, you may find it helpful to reduce the MTU for all
packets on the WAN port, for example, to 256 bytes.
set int=ppp0 mtu=256
You also need to make sure that all large packets are fragmented, even if they were
previously set to not be fragmented.
set int=ppp0 frag=yes
Enable software QoS (SQoS), create an SQoS traffic class, and define a small queue size.
ena sqos
cre sqos tr=1 prio=15 maxq=10
Create an SQoS policy, assign the traffic class to this policy, and define a suitable virtual
bandwidth for the interface being used.
cre sqos policy=1 virt=120kbps
add sqos policy=1 tr=1
add sqos tr=1 classifier=48
Apply the policy to the VPN between branch office
1
and headquarters.
set sqos interface=ipsec-hq tunnelpolicy=1
1. Create classifiers
2. Reduce the MTU
3. Set up software QoS to ensure VoIP traffic has high priority
4. For the site-to-site VPN, apply the SQoS policy to the tunnel