Proactive CC/CV (using BFD) Configuration

Generally applicable proactive OAM parameters are configured using templates.

Proactive CC and CV uses BFD parameters such as Tx/Rx timer intervals, multiplier, and other session/fault management BFD parameters. These are configured using a BFD Template. The BFD Template may be used for non-MPLS-TP applications of BFD, and therefore contains the full set of possible configuration parameters for BFD. Only a sub-set of these may be used for each application.

Generic MPLS-TP OAM and fault management parameters are configured in the OAM Template.

Named templates are referenced from the MPLS-TP Path MEP configuration, so different parameter values are possible for the working and protect paths of a tunnel.

The BFD Template is configured as follows:

config
   router
      bfd
         [no] bfd-template <name>
            [no] transmit-interval <transmit-interval>
            [no] receive-interval <receive-interval> 
            [no] echo-receive <echo-interval> 
            [no] multiplier <multiplier> 
            [no] type <cpm-np>
            exit

The parameters are as follows:

transmit-interval transmit-interval and the receive-interval receive-interval: these are the transmit and receive timers for BFD packets. If the template is used for MPLS-TP, then these are the timers used by CC packets. Values are in ms: 10 ms to 100 000 ms, with 1ms granularity. Default 10ms for CPM3 or better, 1 sec for other hardware. For MPLS-TP CV packets, a transmit interval of 1 s is always used.
multiplier multiplier: integer 3 to 20. Default: 3. This parameter is ignored for MPLS-TP combined cc-v BFD sessions, and the default of 3 used, as per RFC6428.
echo-receive echo-interval: sets the minimum echo receive interval (in ms), for a session. Values: 100 ms to 100 000 ms. Default: 100. This parameter is not used by a BFD session for MPLS-TP.
type cpm-np: selects the CPM network processor as the local termination point for the BFD session. This is enabled by default.

If the BFD timer values as shown above are changed in a template, any BFD sessions on MEPs to which that template is bound tries to renegotiate their timers to the new values.

Caution:

The BFD implementations in some MPLS-TP peer nodes may not be able to handle renegotiation, as allowed by Section 3.7.1 of RFC6428, and may take the BFD session down. This can result in unwanted behavior, such as an unexpected protection switching event. We recommend that users of the system exercise caution when modifying the BFD timer values after a BFD session is up.

Commands within the BFD-template use a begin-commit model. To edit any value within the BFD template, a begin needs to be executed after the template context has been entered. However, a value is still stored temporarily until the commit is issued. After the commit is issued, values are actually used by other modules like the mpls-tp module and BFD module.

A BFD template is referenced from the OAM template. The OAM Template is configured as follows:

config
   router
      mpls
         mpls-tp
            [no] oam-template <name>
               [no] bfd-template <name>
               [no] hold-time-down <interval> 
               [no] hold-time-up <interval>
            exit

hold-time-down interval: 0-5000 deciseconds, 10ms steps, default 0. This is equivalent to the standardized hold-off timer.
hold-time-up interval: 0-500 centiseconds in 100ms steps, default 2 seconds This is an additional timer that can be used to reduce BFD bouncing.
bfd-template name: the named BFD template to use for any BFD sessions enabled under a MEP for which the OAM template is configured.

An OAM template is then applied to a MEP as described above.