Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

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2.
Peer B receives the hello request and sends a hello ack to Peer A. The ack object
contains the following:
• Source instance = 8 (generated by Peer B for this adjacency)
•
Destination instance = 5 (because that is what Peer B detected in the source
instance from peer A)
3.
Peer A receives the hello ack and sends another hello request to peer B. The request
object contains the following:
• Source instance = 5 (generated by Peer A for this adjacency)
• Destination instance = 8 (the source instance generated by Peer B for this
adjacency)
The two peers continue exchanging hello messages until the LSP is torn down. The
following is true for these message exchanges unless a peer resets:
• Peer A always sends source instance= 5 and destination instance= 8 to Peer B.
•
Peer B always sends instance= 8 and destination instance= 5 to Peer A.
Determination That a Peer Has Reset
After the initial exchange of hello messages, both peers perform checks on the messages
they receive to determine whether the peer has reset.
Behavior of the Requesting Peer
The requesting peer examines the ack messages it receives. It compares the source
instance in each subsequent ack message with the previous value. If the value differs or
is set to zero, then the requesting peer treats the acknowledging peer as if communication
has been lost.
The requesting peer also determines whether the acknowledging peer is reflecting back
the requesting peer’s source instance. If the acknowledging peer advertises a wrong value
in the destination instance field of the ack message, then the requesting peer treats the
acknowledging peer as if communication has been lost.
Behavior of the Acknowledging Peer
The acknowledging peer examines the request messages it receives. It compares the
source instance in each subsequent request message with the previous value. If the value
differs or is set to zero, then the acknowledging peer treats the requesting peer as if
communication has been lost.
The acknowledging peer also determines whether the requesting peer is reflecting back
the acknowledging peer’s source instance. It compares the destination instance value in
each request message with the source instance value that it most recently advertised
to the requesting peer. If the requesting peer advertises a wrong value in the destination
instance field of the request message, then the acknowledging peer treats the requesting
peer as if communication has been lost.
Copyright © 2010, Juniper Networks, Inc. 262
JunosE 11.2.x BGP and MPLS Configuration Guide