You are asked to troubleshoot voice quality issues on your newly implement VoIP network.

Understanding the Problem:

The issue involves voice packets being dropped in a newly implemented VoIP network.

Voice packets are marked correctly for the expedited forwarding (EF) queue, indicating that classification is working as intended.

Dropped packets suggest that there may be insufficient resources allocated to handle the traffic in the EF queue.

Key Concepts:

Classifiers: These are used to mark packets so that they can be placed into the appropriate forwarding class. This step is already correctly implemented as indicated by the problem statement.

Rewrite Rules: These ensure that packets retain their markings as they transit the network, but this is not the issue here as packets are already marked correctly.

Policers: These control the rate of traffic to ensure it does not exceed specified limits, but policing is not required here as the issue is with packet drops due to insufficient resources.

Schedulers: These allocate resources (bandwidth, priority) to different queues to ensure that high-priority traffic (like VoIP) is transmitted with minimal delay and packet loss.

Solution: Configuring a Scheduler:

To prevent the EF queue from being starved of resources and to ensure voice packets are not dropped, you need to configure a scheduler. This scheduler will allocate appropriate bandwidth and priority to the EF queue.

Configuring Scheduler on Juniper Devices:

Here is a sample configuration to allocate bandwidth to the expedited forwarding queue:

set class-of-service schedulers voip-scheduler transmit-rate percent 20

set class-of-service schedulers voip-scheduler priority strict-high

set class-of-service forwarding-classes queue 1 expedited-forwarding

set class-of-service forwarding-classes queue 1 scheduler voip-scheduler

In this configuration:

The voip-scheduler is set to allocate 20% of the bandwidth and is given strict-high priority to ensure voice packets are transmitted with the highest priority.

The EF queue (queue 1) is associated with the voip-scheduler.

Verification:

Ensure the scheduler is applied and active on the interfaces handling the VoIP traffic.

Monitor the interface statistics to ensure that packet drops are minimized and voice quality issues are resolved.

References:

Juniper Networks Documentation on Class of Service

Configuring Schedulers