Oam Remote And Local Loopback Feature; Interrelationship Of Oam Link-Fault Management With Ethernet Subsystems - Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010 Configuration Manual

JUNOSe 11.1.x Link Layer Configuration Guide

OAM Remote and Local Loopback Feature

Remote loopback mode ensures link quality between the router and a remote peer
during installation or troubleshooting. JUNOSe Software can place a remote entity
into loopback mode (if remote loopback mode is supported by the remote entity).
When you place a remote entity into loopback mode, the interface receives the
remote loopback request and puts the interface into remote loopback mode. When
the interface is in remote loopback mode, all frames except OAM PDUs are looped
back without any changes made to the frames. OAM PDUs continue to be sent and
processed.
A local OAM entity in active mode can start a remote loopback of its peer through a
Loopback Control OAM PDU that contains the option to enable loopback. During the
initiation phase, the local OAM entity discards any locally sourced non-OAM PDUs.
When the peer receives a loopback request, and assuming that it supports the service,
it sets the forwarding state to loop any received non-OAM PDUs; any locally generated
non-OAM PDUs are discarded while in loopback (Figure 32 on page 233). This
forwarding state is conveyed to the peer using an Information OAM PDU. When the
Information OAM PDU is received after loopback is disabled, the local OAM entity
resumes transmission of locally sourced non-OAM PDUs, in addition to OAM PDUs.
You can prevent two active mode OAM entities from simultaneously placing each
other into loopback mode by making sure that the lower valued source address is
the entity that is placed in loopback mode (Figure 32 on page 233).
Because OAM PDUs are processed during remote loopback, variables can be retrieved
to measure the link performance. The initiating OAM entity stops the remote loopback
process by sending another Loopback Control OAM PDU with the option to disable
the looping of any non-OAM PDUs. When the loopback feature is enabled, the
forwarding process counts the number of packets and bytes transmitted to the peer,
and the number of packets and bytes received from the peer.
NOTE: The peer in loopback mode might intentionally discard data frames to
accommodate OAM traffic. OAM PDUs are assigned a higher priority than regular
data packets when oversubscription of the allocated bandwidth occurs.
Related Topics

Interrelationship of OAM Link-Fault Management with Ethernet Subsystems

802.3ah OAM assists the monitoring of individual Ethernet links. Link aggregation
mechanisms, such as 802.3ad, operate above the 802.3ah sublayer. Figure 33 on
240
OAM Remote and Local Loopback Feature
OAM Messages on page 230
Configuring 802.3ah OAM Link-Fault Management on page 242
Example: Enabling Remote Loopback Support on the Local Interface on page 250
ethernet oam lfm remote-loopback supported
ethernet oam lfm remote-loopback