Voice Services Configuration Guidelines

The Adaptive Services (AS) and Multiservices PICs support the compressed Real-Time Transport Protocol (CRTP) on the lsq-fpc/pic/port interface type. This enables voice over IP (VoIP) traffic to use low-speed links more effectively, by compressing the 40-byte IP/User Datagram Protocol (UDP)/RTP header down to from 2 to 4 bytes in most cases.

Note: J Series routers also support VoIP routing through the Avaya TGM550 media gateway module. This is a separate product from the adaptive services suite and is not supported on M Series and T Series routers. For more information, see the Junos OS Interfaces and Routing Configuration Guide.

For link services IQ interfaces (lsq) only, you can configure CRTP with multiclass MLPPP (MCML). MCML greatly simplifies packet ordering issues that occur when multiple links are used. Without MCML, all voice traffic belonging to a single flow is hashed to a single link in order to avoid packet ordering issues. With MCML, you can assign voice traffic to a high-priority class, and you can use multiple links. For more information about MCML support on link services IQ interfaces, see Configuring Link Services and CoS on Services PICs.

Link services IQ interfaces use a bundle configuration. For more information, see Layer 2 Service Package Capabilities and Interfaces and Multilink and Link Services Logical Interface Configuration Overview.

Note: On LSQ interfaces, all multilink traffic for a single bundle is sent to a single processor. If CRTP is enabled on the bundle, it adds overhead to the CPU. Because T3 network interfaces support only one link per bundle, make sure you configure a fragmentation map for compressed traffic on these interfaces and specify the no-fragmentation option. For more information, see Configuring Delay-Sensitive Packet Interleaving and Configuring CoS Fragmentation by Forwarding Class on LSQ Interfaces.

Voice services do not require a separate service rules configuration, but you need to configure both services interfaces and network interfaces, as described in the following topics: