Configuring Link and Multilink Services Logical Interfaces

You configure multilink and link services interface properties at the logical unit level. Default settings for multilink and link services logical interface properties are described in Default Settings for Multilink and Link Services Logical Interfaces.

For general information about logical unit properties or family inet properties, see the Junos OS Network Interfaces Library for Routing Devices. For information about multilink and link services properties you configure at the family inet hierarchy level, see Configuring the Links in a Multilink or Link Services Bundle.

Multilink and link services interfaces support the following logical interface encapsulation types:

• MLPPP

• Multilink Frame Relay (MLFR) end-to-end

By default, the logical interface encapsulation type on multilink interfaces is MLPPP. The default logical interface encapsulation type on link services interfaces is MLFR end-to-end. For general information on encapsulation, see the Junos OS Network Interfaces Library for Routing Devices.

You can also configure physical interface encapsulation on link services interfaces. For more information, see Configuring Encapsulation for Link Services Physical Interfaces.

To configure multilink or link services encapsulation, include the encapsulation type statement at the following hierarchy levels:

• [edit interfaces interface-name unit logical-unit-number]

• [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]

You must also configure the T1, E1, or DS0 physical interface with the same encapsulation type.

By default, the drop timeout parameter is disabled. You can configure a drop timeout value to provide a recovery mechanism if individual links in the multilink or link services bundle drop one or more packets. Drop timeout is not a differential delay tolerance setting, and does not limit the overall latency. However, you need to make sure the value you set is larger than the expected differential delay across the links, so that the timeout period does not elapse under normal jitter conditions, but only when there is actual packet loss. You can configure differential delay tolerance for link services interfaces only. For more information, see Configuring Differential Delay Alarms on Link Services Physical Interfaces with MLFR FRF.16.

To configure the drop timeout value, include the drop-timeout statement:

drop-timeout milliseconds;

You can include this statement at the following hierarchy levels:

• [edit interfaces interface-name unit logical-unit-number]

• [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]

For link services interfaces, you also can configure the drop timeout value at the physical interface level by including the drop-timeout statement at the [edit interfaces ls-fpc/pic/port:channel mlfr-uni-nni-bundle-options] hierarchy level:

drop-timeout milliseconds;

By default, the drop timer has a value of 500 ms for bundles greater than or equal to the T1 bandwidth value, and 1500 ms for other bundles. Any CLI-configured value overrides these defaults. Values can range from 1 through 2000 milliseconds. Values less than 5 milliseconds are not recommended, and a configured value of 0 reverts to the default value of 2000 milliseconds.

If you configure the drop-timeout statement with a value of 0, it disables any resequencing by the PIC for the specified class of MLPPP traffic. Packets are forwarded with the assumption that they arrived in sequence, and forwarding of fragmented packets is disabled for all classes. Fragments dropped as a result of this setting will increment the counter at the class level.

Alternatively, you can configure the drop-timeout statement at the [edit class-of-service fragmentation-maps map-name forwarding-class class] hierarchy level. The behavior and the default and range values are identical, but the setting applies only to the specified forwarding class. Configuration at the bundle level overrides configuration at the class-of-service level.

By default, compression of the inner PPP header in the MLPPP payload is enabled. To disable compression, include the disable-mlppp-inner-ppp-pfc statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level. For example:

interfaces lsq-1/2/0 {
    unit 0 {
        encapsulation multilink-ppp;
        disable-mlppp-inner-ppp-pfc;
        multilink-max-classes 4;
        family inet {
            address 10.50.1.2/30;
        }
    }
}

For more information about CoS configuration, see the Junos OS Class of Service User Guide for Routing Devices. You can view the configured drop-timeout value and the status of inner PPP header compression by issuing the show interfaces interface-name extensive command.

For multilink and link services logical interfaces with MLPPP encapsulation only, you can configure a fragmentation threshold to limit the size of packet payloads transmitted across the individual links within the multilink circuit. The software splits any incoming packet that exceeds the fragmentation threshold into smaller units suitable for the circuit size; it reassembles the fragments at the other end, but does not affect the output traffic stream. The threshold value affects the payload only; it does not affect the MLPPP header. By default, the fragmentation threshold parameter is disabled.

To configure a fragmentation threshold value, include the fragment-threshold statement:

fragment-threshold bytes;

You can include this statement at the following hierarchy levels:

• [edit interfaces interface-name unit logical-unit-number]

• [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]

For link services interfaces, you also can configure a fragmentation threshold value at the physical interface level by including the fragment-threshold statement at the [edit interfaces ls-fpc/pic/port:channel mlfr-uni-nni-bundle-options] hierarchy level:

fragment-threshold bytes;

The maximum fragment size can be from 128 through 16,320 bytes. The Junos OS automatically subdivides packet payloads that exceed this value. Any value you set must be a multiple of 64 bytes (Nx64). The default value, 0, results in no fragmentation.

You can set the minimum number of links that must be up for the multilink bundle as a whole to be labeled up. By default, only one link must be up for the bundle to be labeled up. A member link is considered up when the PPP Link Control Protocol (LCP) phase transitions to open state.

The minimum-links value should be identical on both ends of the bundle.

To set the minimum number, include the minimum-links statement:

minimum-links number;

You can include this statement at the following hierarchy levels:

• [edit interfaces interface-name unit logical-unit-number]

• [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]

For link services interfaces, you also can configure the minimum number of links at the physical interface level by including the minimum-links statement at the [edit interfaces ls-fpc/pic/port:channel mlfr-uni-nni-bundle-options] hierarchy level:

minimum-links number;

The number can be from 1 through 8. The maximum number of links supported in a bundle is 8. When 8 is specified, all configured links of a bundle must be up.

The maximum received reconstructed unit (MRRU) is the maximum packet size that the multilink interface can process. It is similar to a maximum transmission unit (MTU), but applies only to multilink bundles. By default, the MRRU is set to 1500 bytes. You can configure a different MRRU value if the peer equipment allows this. The MRRU accounts for the original payload, for example the Layer 3 protocol payload, but does not include the 2-byte PPP header or the additional MLPPP or MLFR header applied while the individual multilink packets are traversing separate links in the bundle.

To configure a different MRRU value, include the mrru statement:

mrru bytes;

You can include this statement at the following hierarchy levels:

• [edit interfaces interface-name unit logical-unit-number]

• [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]

For link services interfaces, you also can configure a different MRRU at the physical interface level by including the mrru bytes statement at the [edit interfaces ls-fpc/pic/port:channel mlfr-uni-nni-bundle-options] hierarchy level. The MRRU size can range from 1500 through 4500 bytes.

You can configure separate family mtu values on the following protocol families under bundle interfaces: inet, inet6, iso, and mpls. If not configured, the default value of 1500 is used on all except for mpls configurations, in which the value 1488 is used.

For MLPPP, the sequence header format is set to 24 bits by default. You can configure an alternative value of 12 bits, but 24 bits is considered the more robust value for most networks.

To configure a different sequence header value, include the short-sequence statement:

short-sequence;

You can include this statement at the following hierarchy levels:

• [edit interfaces interface-name unit logical-unit-number]

• [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]

For MLFR FRF.15, the sequence header format is set to 24 bits by default. This is the only valid option.

For link services IQ (lsq-) interfaces, Junos OS class of service (CoS) is fully supported and functions as described in the Junos OS Class of Service User Guide for Routing Devices. For more information and detailed configuration examples, see Layer 2 Service Package Capabilities and Interfaces.

On SRX Series Firewalls, the lsq- interface is an internal interface, which is not associated with a physical interface. For information about link services on SRX Series Firewalls, see the Junos OS Interfaces Configuration Guide for Security Devices.

For information about CoS functions and link services on M Series or T Series routers, see the following sections:

• CoS for Link Services Interfaces on M Series and T Series Routers
• Example: Configuring CoS on Link Services Interfaces

[edit interfaces]
ls-7/0/0 {
    unit 0 {
        encapsulation multilink-ppp;
        interleave-fragments;
        family inet {
            filter {
                output lfi_ls_filter;
            }
            address 10.54.0.2/32 {
                destination 10.54.0.1;
            }
        }
    }
}
ge-7/2/0 {
    unit 0 {
        family inet {
            address 192.168.1.1/24;
        }
    }
}
ce1-7/3/6 {
    no-partition interface-type e1;
}
e1-7/3/6 {
    encapsulation ppp;
    unit 0 {
        family mlppp {
            bundle ls-7/0/0.0;
        }
    }
}
ce1-7/3/7 {
    no-partition interface-type e1;
}
e1-7/3/7 {
    encapsulation ppp;
    unit 0 {
        family mlppp {
            bundle ls-7/0/0.0;
        }
    }
}
[edit class-of-service]
classifiers {
    dscp dscp_default {
        import default;
    }
    inet-precedence inet-precedence_default {
        import default;
    }
}
code-point-aliases {
    dscp {
        af11 001010;
        af12 001100;
        af13 001110;
        af21 010010;
        af22 010100;
        af23 010110;
        af31 011010;
        af32 011100;
        af33 011110;
        af41 100010;
        af42 100100;
        af43 100110;
        be 000000;
        cs1 001000;
        cs2 010000;
        cs3 011000;
        cs4 100000;
        cs5 101000;
        cs6 110000;
        cs7 111000;
        ef 101110;
    }
    inet-precedence {
        af11 001;
        af21 010;
        af31 011;
        af41 100;
        be 000;
        cs6 110;
        cs7 111;
        ef 101;
        nc1 110;
        nc2 111;
    }
}
forwarding-classes {
    queue 0 be;
    queue 1 ef;
    queue 2 af;
    queue 3 nc;
}
interfaces {
    ge-7/2/0 {
        scheduler-map sched-map;
        unit 0 {
            classifiers {
                dscp dscp_default;
            }
        }
    }
    e1-7/3/6 {
        scheduler-map sched-map;
    }
    e1-7/3/7 {
        scheduler-map sched-map;
    }
    ls-7/0/0 {
        scheduler-map sched-map;
        unit 0 {
            classifiers {
                inet-precedence inet-precedence_default;
            }
        }
    }
}
scheduler-maps {
    sched-map {
        forwarding-class af scheduler af-scheduler;
        forwarding-class be scheduler be-scheduler;
        forwarding-class ef scheduler ef-scheduler;
        forwarding-class nc scheduler nc-scheduler;
    }
}
schedulers {
    af-scheduler {
        transmit-rate percent 25;
        buffer-size percent 25;
    }
    be-scheduler {
        transmit-rate percent 25;
        buffer-size percent 25;
    }
    ef-scheduler {
        transmit-rate percent 25;
        buffer-size percent 25;
    }
    nc-scheduler {
        transmit-rate percent 25;
        buffer-size percent 25;
    }
}
[edit firewall]
filter lfi_ls_filter {
    term term0 {
        from {
            destination-address {
                192.168.1.3/32;
            }
            precedence 5;
        }
        then {
            count count-192-168-1-3;
            forwarding-class af;
            accept;
        }
    }
    term default {
        then {
            log;
            forwarding-class best effort;
            accept;
        }
    }
}