End-To-End Fragmentation And Reassembly; Frame Fragmentation; Frame Reassembly - Juniper JUNOSE SOFTWARE 11.2.X - LINK LAYER CONFIGURATION GUIDE 7-7-2010 Configuration Manual

JunosE 11.2.x Link Layer Configuration Guide

End-to-End Fragmentation and Reassembly

Frame Fragmentation

Frame Reassembly

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To enable SNMP link status processing for a Frame Relay subinterface, you must issue
the command from Subinterface Configuration mode.
Examples
host1(config-if)#snmp trap frame-relay link-status
host1(config-subif)#snmp trap frame-relay link-status
Use the no version to disable SNMP link status processing for a Frame Relay major
interface or subinterface.
See snmp trap frame-relay link-status.
The fragmentation and reassembly feature reduces excessive delays of Frame Relay
packets by breaking them up into smaller fragments and interleaving them with real-time
frames. By doing this, real-time and non-real-time data frames can be carried together
on lower-speed links without causing excessive delays to the real-time traffic. On receiving
the smaller fragments by the peer interface, the fragments are reassembled 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.
E Series routers support end-to-end fragmentation according to the FRF.12
Implementation Agreement standard. Unlike UNI and NNI fragmentation, end-to-end
supports fragmentation only at the endpoints. End-to-end fragmentation and reassembly
are supported only on non-multilink Frame Relay interfaces on cOC12/STM4 and CT3 12
FO modules.
You configure end-to-end fragmentation at the Frame Relay subinterface level.
Fragmentation is applied to all PVCs associated with the subinterface. In most cases,
fragmentation and reassembly are used together. Fragmentation and reassembly,
however, can be configured separately for each map class.
For additional information, see Frame Relay Forum—Frame Relay Fragmentation
Implementation Agreement, FRF.12 (December 1997).
When you enable fragmentation, you can specify a maximum payload size of the resulting
fragments. If the maximum payload size is not specified, the default value of 52 bytes is
used. When enabled, fragmentation begins when the portion of the packet that has not
been transmitted in previous fragments exceeds the configured maximum payload size.
The fragmentation process continues until the entire packet has been transmitted. Frames
that do not exceed the configured maximum payload size are not fragmented.
If you disable fragmentation, all packets transmitted by the Frame Relay subinterface
are transmitted intact.
When reassembly is disabled and a data frame is received, a few scenarios may occur:
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