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Configuring a Fragmentation Threshold

By default, the fragmentation threshold parameter is disabled. For interfaces with MLPPP encapsulation only, you can configure a fragmentation threshold to set a maximum size for 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.

Note: To ensure proper load balancing:

For Link Services MLFR (FRF.15 and FRF.16) interfaces, do not include the fragment-threshold statement in the configuration.
For MLPPP interfaces, do not include both the fragment-threshold statement and the short-sequence statement in the configuration.
For MLFR (FRF.15 and FRF.16) and MLPPP interfaces, if the MTU of links in a bundle is less than the bundle MTU plus encapsulation overhead, then fragmentation is automatically enabled. You should avoid this situation for MLFR (FRF.15 and FRF.16) interfaces and for MLPPP interfaces on which short-sequencing is enabled.

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 software 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.

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