How to configure CBWFQ and LLQ for PPP

[TCC_2]

Core Issue

Low Latency Queueing (LLQ) is the key prioritization technique for enabling voice and data integration.

Resolution

To configure Low Latency Queueing (LLQ), perform these steps:

1. Create a class map for Voice over IP (VoIP) traffic, and define a match criteria.      
2. Create a class map for VoIP signaling, and define a match criteria (optional).      
3. Create a policy map, and associate it to the VoIP class maps.      
4. Enable LLQ by applying the policy map to the outbound WAN interface.

These documents provide useful information on Configuring Class-Based Weighted Fair Queuing (CBWFQ) and LLQ. They also provide a number of other good sources on configuring Quality of Service (QoS) for voice:

• Configuring Burst Size in Low Latency Queueing      
• Configuring CBWFQ and LLQ on MLPPP and Dialer Interfaces      
• Voice Quality

[BOB ATKINS]

These configuration do not work on Cisco 7513 routers with the following configuration:

RSP16 (Max memory)

VIP4-80 (Max memory) channelized DS3 blades

After running extensive tests we have found very poor QoS performance and high voice jitter and packet loss during period of heavy bulk data transfer.