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DES-7200 Configuration Guide Chapter 3 MPLS Reliability Configuration
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z Adopting MPLS OAM mechanism. This mechanism can effectively detect, verify and locate
defects or faults originating from the MPLS layer. However, the standardization of MPLS
OAM mechanism is still underway, and various OAM mechanisms are merely at the
preliminary stage in real network applications. OAM feature is not supported by all network
devices.
z Hello packet mechanism using MPLS signaling protocol. This mechanism takes a longer
time to detect faults (generally in seconds or more time). Therefore, this mechanism will
result in the loss of substantial traffic.
MPLS BFD mechanism can address the aforementioned problems. It has the following features:
z Supporting intercommunication. Providing an unified detection mechanism for the entire
network.
z Allowing fast detection. Capable of providing light-load fast detection, speeding up the
activation of standby forwarding path, and improving MPLS network reliability.
z BFD can be used to detect faults in the data plane of MPLS LSP forwarding path.
Meanwhile, BFD is also more suitable for being implemented in hardware or firmware due to
its fixed packet format.
3.2.1.2 MPLS BFD feature
Introducing the mode to establish and detect MPLS BFD sessions.
BFD session establishment
BFD uses My Discriminator and Your Discriminator to identify multiple BFD sessions between
the same pair of systems. The means of discriminator configuration can be divided into: 1)
manual configuration; 2) automatic configuration.
Manual configuration will manually configure my discriminator and your discriminator of BFD. In
this way, before BFD session is established, there is no need to negotiate and learn your
discriminator through the discriminator carried in the LSP Ping echo packet. The BFD session
will be established directly.
Automatic configuration uses the discriminator carried in the LSP Ping echo packet to negotiate
and learn your discriminator before it can establish the BFD session.
The following paragraphs will describe the procedures of establishing BFD session. At the initial
stage of BFD session, two ends sending packets play either the active role or the passive role.
Whether the Ingress LSR or Egress LSR play an active role or passive is determined by the