Juniper Networks 10.4 EthernetOAM Connectivity Fault Management

•Faultisolation, verification, and recovery(isolation and verification are providedby a

combinationof protocols, whilerecovery is the function of protocols such as spanning

tree)

Theloopback protocol used in Ethernet OAM is modeledon the standard IP ping. After

afault is detected, the loopbackprotocol performs fault verification and isolationunder

thedirection of a networkoperator. Theloopback is performed using request and response

messagepairs. A unicast loopbackmessage is generated by a MEP and a loopback reply

isgenerated by the destination MIP or MEP.The target MAC address is learnedby the

continuitycheck protocolor linktrace protocol. The loopbackmessage's packet is always

forwardedto a unique port by the originating MEP,as determined by a MAC tablelookup

orthe MEP interface MAC address. The targetMIP or MEP generates a unicast loopback

replyin response to the received loopbackmessage. The loopback message followsthe

samepath as a data packet, and intermediatebridges simply forward the packet to the

destinationMIP or MEP.

Documentation

MXSeries Ethernet Services Routers SolutionsPage•

•EthernetOAM Connectivity Fault Managementon page 104

•Example:Configuring Ethernet CFM over VPLS on page105

•Example:Configuring Ethernet CFM on Bridge Connections on page112

•Example:Configuring Ethernet CFM on Physical Interfaceson page 116

EthernetOAM Connectivity Fault Management

Themost complete connectivity faultmanagement (CFM) is defined in IEEE 802.1ag.

Thistopic emphasizes the use of CFM in a Metro Ethernet environment.

Themajor features of CFM are:

•Faultmonitoring using the continuity check protocol.This is a neighbor discovery and

healthcheck protocol which discoversand maintains adjacencies at the VLAN or link

level.

•Pathdiscoveryand fault verificationusing the linktrace protocol. Similar toIP traceroute,

thisprotocol maps the path taken to a destinationMAC address through one or more

bridgednetworks between the source and destination.

•Faultisolation using the loopback protocol.Similar to IP ping, this protocol works with

thecontinuity check protocol during troubleshooting.

CFMpartitions the service network into various administrativedomains. For example,

operators,providers, and customersmay be part of different administrative domains.

Eachadministrative domain is mapped into one maintenancedomain providing enough

informationtoperform its own management, thus avoiding securitybreaches and making

end-to-endmonitoring possible. Each maintenance domain is associatedwith a

maintenancedomain level from 0 through 7.Level allocation is based on the network

hierarchy,where outermost domains are assigneda higher level than the innermost

domains.Customer end points have to highest maintenance domain level.In a CFM

Junos10.4 MX Series Ethernet ServicesRouters Solutions Guide