Alcatel-Lucent 7450 Manual page 664

hello-reduction
Syntax
Context
Description
Page 664
factor — Specifies the number of keepalive messages that should be sent on an idle LDP session in
the hello timeout interval.
Values 1 — 255
hello-reduction {enable factor | disable}
no hello-reduction
config>router>ldp>targeted-session>ipv4
config>router>ldp>targeted-session>ipv6
config>router>ldp>targeted-session>peer
config>router>ldp>targ-session>peer-template
This command enables the suppression of periodic targeted Hello messages between LDP peers once
the targeted LDP session is brought up.
When this feature is enabled, the target Hello adjacency is brought up by advertising the Hold-Time
value the user configured in the "hello timeout" parameter for the targeted session. The LSR node
will then start advertising an exponentially increasing Hold-Time value in the Hello message as soon
as the targeted LDP session to the peer is up. Each new incremented Hold-Time value is sent in a
number of Hello messages equal to the value of the argument factor, which represents the dampening
factor, before the next exponential value is advertised. This provides time for the two peers to settle
on the new value. When the Hold-Time reaches the maximum value of 0xffff (binary 65535), the two
peers will send Hello messages at a frequency of every [(65535-1)/local helloFactor] seconds for the
lifetime of the targeted-LDP session (for example, if the local Hello Factor is three (3), then Hello
messages will be sent every 21844 seconds.
The LSR node continues to compute the frequency of sending the Hello messages based on the
minimum of its local Hold-time value and the one advertised by its peer as in RFC 5036. Thus for the
targeted LDP session to suppress the periodic Hello messages, both peers must bring their advertised
Hold-Time to the maximum value. If one of the LDP peers does not, the frequency of the Hello
messages sent by both peers will continue to be governed by the smaller of the two Hold-Time
values.
When the user enables the hello reduction option on the LSR node while the targeted LDP session to
the peer is operationally up, the change will take effect immediately. In other words, the LSR node
will start advertising an exponentially increasing Hold-Time value in the Hello message, starting with
the current configured Hold-Time value.
When the user disables the hello reduction option while the targeted LDP session to the peer is
operationally up, the change in the Hold-Time from 0xffff (binary 65535) to the user configured
value for this peer will take effect immediately. The local LSR will immediately advertise the value
of the user configured Hold-Time value and will not wait until the next scheduled time to send a
Hello to make sure the peer adjusts its local hold timeout value immediately.
In general, any configuration change to the parameters of the T-LDP Hello adjacency (modifying the
hello adjacency Hello Timeout or factor, enabling/disabling hello reduction, or modifying hello
reduction factor) will cause the LSR node to trigger immediately an updated Hello message with the
updated Hold Time value without waiting for the next scheduled time to send a Hello.
7450 ESS MPLS Guide