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JUNOS 10.1 Network Interfaces Configuration Guide
By default, translation of Frame Relay control bits is disabled. If you enable Frame
Relay control bit translation, the bits are translated in both directions (CE to PE and
PE to CE):
The Frame Relay control bits do not map to MPLS EXP labels, and do not affect
class-of-service (CoS) behavior inside the provider network.
You enable or explicitly disable translation of Frame Relay control bits by including
the
You can include these statements at the following hierarchy levels:
If you enable or disable Frame Relay control bit translation on one CE-facing interface,
you must configure the same Frame Relay control bit translation settings on the
other CE-facing interface.
If you change the Frame Relay control bit translation settings, the circuit goes down
and comes back up, which might result in traffic loss for a few seconds.
If you enable Frame Relay control bit translation, the number of supportable Layer 2
virtual private networks (VPNs) and Layer 2 circuits is reduced to one eighth of what
the router can support without Frame Relay control bit translation enabled.
For ATM2 IQ interfaces, the control word contains a field to carry ATM cell loss
priority (CLP) information by default. For more information, see "Configuring Layer
2 Circuit Transport Mode" on page 308.
For more information about Layer 2 circuits, see the JUNOS VPNs Configuration Guide
and the JUNOS Routing Protocols Configuration Guide. For a comprehensive example,
see the JUNOS Feature Guide.
Configuring the Media MTU on Frame Relay Interfaces
For Frame Relay interfaces, the default media maximum transmission unit (MTU) is
4482 bytes. (For a complete list of MTU values, see "Configuring the Media MTU"
on page 110.)
384
Configuring the Media MTU on Frame Relay Interfaces
Backward explicit congestion notification (BECN)—A header bit transmitted by
the destination router requesting that the source router send data more slowly.
From CE to PE—At ingress, the DE, FECN, and BECN header bits from the
incoming Frame Relay header are mapped to the control word.
From PE to CE—At egress, the DE, FECN, and BECN header bits from the control
word are mapped to the outgoing Frame Relay header.
translate-discard-eligible
(translate-discard-eligible | no-translate-discard-eligible);
(translate-fecn-and-becn | no-translate-fecn-and-becn);
[edit interfaces interface-name unit logical-unit-number family ccc]
[edit logical-systems logical-system-name interfaces interface-name unit
logical-unit-number family ccc]
and
translate-fecn-and-becn
statements:
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