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Configuring Services Interfaces for Voice Services

You define voice service properties such as compression by configuring statements and values for a voice services interface, specified by the interface type lsq- (ls- on J-series Services Routers). You can include the following statements:

encapsulation mlppp;
family inet {
address address;
}
compression {
rtp {
f-max-period number;
maximum-contexts number <force>;
port {
minimum port-number;
maximum port-number;
}
queues [ queue-numbers ];
}
}
fragment-threshold bytes;

You can include these statements at the following hierarchy levels:

The following sections provide detailed instructions for configuring for voice services on services interfaces:

Configuring the Logical Interface Address for the MLPPP Bundle

To configure the logical address for the MLPPP bundle, include the address statement:

address address {
...
}

You can configure this statement at the following hierarchy levels:

address specifies an IP address for the interface. AS and MultiServices PICs support only IP version 4 (IPv4) addresses, which are therefore configured under the family inet statement.

For information on other addressing properties you can configure that are not specific to service interfaces, see the JUNOS Network Interfaces Configuration Guide.

Configuring Compression of Voice Traffic

You can specify how a services interface handles voice traffic compression by including the compression statement:

compression {
rtp {
f-max-period number;
maximum-contexts number <force>;
port {
minimum port-number;
maximum port-number;
}
queues [ queue-numbers ];
}
}

You can include this statement at the following hierarchy levels:

The following statements configure the indicated compression properties:

Configuring Delay-Sensitive Packet Interleaving

When you configure CRTP, the software automatically enables link fragmentation and interleaving (LFI). LFI reduces excessive delays by fragmenting long packets into smaller packets and interleaving them with real-time frames. This allows real-time and non-real-time data frames to be carried together on lower-speed links without causing excessive delays to the real-time traffic. When the peer interface receives the smaller fragments, it reassembles the fragments into their original packet. For example, short delay-sensitive packets, such as packetized voice, can race ahead of larger delay-insensitive packets, such as common data packets.

By default, LFI is always active when you include the compression rtp statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level. You control the operation of LFI indirectly by setting the fragment-threshold statement on the same logical interface. For example, if you include the fragment-threshold 256 statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level, all IP packets larger than 256 bytes are fragmented.

Example: Configuring Compression of Voice Traffic

Configure compression on a T1 interface with MLPPP encapsulation. Configure fragmentation for all IP packets larger than 128 bytes.

[edit interfaces]
t1-1/0/0 {
unit 0 {
family mlppp {
bundle lsq-1/1/0.1;
}
}
}
lsq-1/1/0 {
encapsulation mlppp;
unit 1 {
compression {
rtp {
port minimum 2000 maximum 64009;
}
}
family inet {
address 30.1.1.2/24;
}
fragment-threshold 128;
}
}
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