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Configuring Link Services and Multilink Interfaces

Multilink Point-to-Point Protocol (MLPPP) enables you to bundle multiple PPP links into a single logical link. Multilink Frame Relay (MLFR) enables you to bundle multiple Frame Relay data-link connection identifiers (DLCIs) into a single logical link. MLPPP and MLFR provide service option granularity between low-speed T1 and E1 services and higher-speed T3 and E3 services. You use MLPPP and MLFR to increase bandwidth in smaller, more cost-effective increments. In addition to providing incremental bandwidth, bundling multiple links can add a level of fault tolerance to your dedicated access service, because you can implement bundling across multiple Physical Interface Cards (PICs), protecting against the failure of any single PIC.

The JUNOS software supports four Multilink Protocol (MP)-based services PICs: the Adaptive Services PIC, Multilink Services PIC, Link Services PIC, and Voice Services PIC. For more information about the Adaptive Services PIC, see Configuring Adaptive Services Interfaces. For more information about the Voice Services PIC, see Configuring Voice Services Interfaces.

At the logical unit level, the Multilink Services, Link Services, and Voice Services PICs support the MLPPP and MLFR FRF.15 encapsulation types. At the physical interface level, the Adaptive Services, Link Services, and Voice Services PICs also support the MLFR FRF.16 encapsulation type.

MLPPP is supported on interface types ls-fpc/pic/port, lsq-fpc/pic/port, ml-fpc/pic/port, and vsp-fpc/pic/port.

MLFR Frame Relay Forum (FRF)15 is supported on interface types ml-fpc/pic/port, ls-fpc/pic/port, and vsp-fpc/pic/port. For MLFR FRF.15, multiple permanent virtual circuits (PVCs) are combined into one aggregated virtual circuit (AVC). This provides fragmentation over multiple PVCs on one end and reassembly of the AVC on the other end.

MLFR FRF.16 is supported on the AS PIC interface, lsq-fpc/pic/port and the Link Services PIC interface, ls-fpc/pic/port:channel, which denotes a single MLFR FRF.16 bundle. For MLFR FRF.16, multiple links are combined to form one logical link. Packet fragmentation and reassembly occur on a per-VC basis. Each bundle can support multiple VCs. Link Services PICs can support up to 256 DLCIs per MLFR FRF.16 bundle. The physical connections must be E1, T1, channelized DS3-to-DS1, channelized DS3-to-DS0, channelized E1, channelized STM1, or channelized intelligent queuing (IQ) interfaces. When you bundle channelized interfaces using the link services interface, the channelized interfaces require M-series Enhanced FPCs.

The standards for MLPPP, MLFR FRF.15, and MLFR FRF.16 are defined in the following specifications:

To configure multilink and link services logical interface properties, include the following statements:

interface-name {

    unit logical-unit-number {

        dlci dlci-identifier;

        drop-timeout milliseconds;

        encapsulation type;

        fragment-threshold bytes;

        interleave-fragments;

        minimum-links number;

        mrru bytes;

        multicast-dlci dlci-identifier;

        short-sequence;

        family family {

            address address {

                destination address;

            }

            bundle interface-name;

            }

        }

    }

}

You can include these statements at the following hierarchy levels:

To configure link services physical interface properties, include the mlfr-uni-nni-bundle-options statement at the [edit interfaces interface-name] hierarchy level:

[edit interfaces interface-name]

encapsulation type;

mlfr-uni-nni-bundle-options {

    acknowledge-retries number;

    acknowledge-timer milliseconds;

    action-red-differential-delay (disable-tx | remove-link);

    drop-timeout milliseconds;

    fragment-threshold bytes;

    hello-timer milliseconds;

    lmi-type (ansi | itu);

    minimum-links number;

    mrru bytes;

    n391 number;

    n392 number;

    n393 number;

    red-differential-delay milliseconds;

    t391 number;

    t392 number;

    yellow-differential-delay milliseconds;

}

This chapter is organized as follows:

For examples of multilink and link services interface configuration, see the following sections:

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