Providing Rate-Limiting for VoIP Traffic

Because PGCP traffic flows involve voice traffic, the flows require quality of service that:

• Provides the bandwidth that the flow requires.
• Ensures that flows do not consume more resources than they need.
• Regulates flows that are nonconforming and present vastly greater rates of traffic.

This quality of service is provided through a two-rate three-color policing functionality on the MultiServices PIC. This policer complies with RFC 2698, A Two Rate Three Color Marker, September, 1999. With the rate limiting capability, the MultiServices PIC can police flows to conform to:

• Committed Information Rate (CIR)
• Peak Information Rate (PIR)
• Committed Burst Size (CBS)
• Peak Burst Size (PBS)

How the Rate-Limiting Feature Works

You use rate limiting with PGCP gates. To enable rate limiting for a PGCP gate, you need to provide traffic management package (TMAN) parameters in the PGCP signaling commands that operate on gates. You configure these parameters on the PGC. These parameters are:

• Tman/sdr—Sustained data rate. This parameter provides the CIR.
• Tman/pdr—Peak data rate. This parameter provides the PIR.
• Tman/mbs—Maximum burst size. This parameter provides the burst size. Both the CBS and the PBS defined in RFC 2698 map to the maximum burst size.

The PGC sends the rate-limiting parameters to the packet gateway in PGCP gate open and gate modify signaling requests. When the MultiServices PIC receives these parameters, it marks the packets red, yellow, or green as specified in RFC 2698. A packet is marked red if it exceeds the PIR. A packet is marked yellow if it exceeds the CIR. A packet is marked green if it does not exceed the CIR. Packets that are marked red are dropped by the Multiservices PIC.

Viewing Rate-Limiting Statistics

To view rate-limiting statistics on a VPG, use the show services pgcp gates gateway-name extensive or the show services pgcp gates gateway-name gate-id gate-id extensive operational mode command.