Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 403)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 379
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RSVP-TE Hello
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Removing Hello support from one end of the link
Consider the case when both ends of the link supported RSVP-TE Hello messages and the
exchange of messages was normal as both links were up. Remove the support for Hello from one
side of the link. The other side keeps sending Hello Request messages, but the neighbor starts
ignoring these requests as it no longer wishes to participate in Hello messages exchange. In this
case, because the neighbor stops sending ACKs, the router considers this as a neighbor down case
and brings down all the RSVP sessions going over that interface. After a neighbor down event, Hello
message exchange starts off from scratch (re-initiates). If the neighbor does not respond to Hello
Requests, the router assumes that the neighbor does not support Hello because no ACK was ever
received after re-initiating Hello.
In addition, when RSVP Hello is supported only on one end of the link, the end that supports Hello
will send Hello Request messages until it hits the hello_tolerance limit and then stops sending any
further Hellos messages. It restarts sending Hellos when it receives a Hello message from the
neighbor and then again continues the two way communication as before.
CAUTION
Caution: When disabling RSVP hello, please disable it on both sides of the link at the same time
to avoid bringing down all the RSVP sessions going over that link.
Configuring Hello-tolerance
Hello-tolerance can be individually configured on both ends of the interface. Considering both sides
of the link are participating in Hello communication, if no Instance values are received, through
either of the REQUEST or ACK objects, from a neighbor within this configured hello-tolerance
number of hello-intervals, then this node presumes that it cannot communicate with the neighbor.
Configuring hello-acknowledgements
Configuring hello-acknowledgements command (on the global MPLS RSVP Hello level) enables the
router to respond back by sending Hello ACKs on neighbors not carrying any RSVP sessions. By
default, Hello ACKs are sent only to neighbors carrying RSVP sessions. This is an optimization.
Configuration steps
There are three parameters that can be configured for this feature. Two of them are at an
mpls-interface level and one is at the mpls-rsvp level.
RSVP Hello configuration at global MPLS RSVP level
Interval and tolerance for RSVP-TE Hello protocol can be configured at global MPLS RSVP level. The
global configuration is pushed to all the mpls-interfaces if interface level configurations are not
present. In addition to these two parameters, one more parameter can be configured at global
MPLS RSVP level (acknowledgements).
Backward compatibility
This is fully backward compatible because the feature is turned off by default.