Session IP address changes

[Chris Nogradi <[e-mail]>]

Dave,

the base BFD draft in section 6.3 paragraph 3 suggests that a BFD peer could 
decide to change its IP address and that this change would be transparent to 
the running BFD session since it is demultiplexing based on the 
discriminator.  However, it would seem that the receiving node would have to 
react to this change by sending all BFD packet for this session to the new 
address in order to guarantee that the session does not go down.  If this is 
the case, it would seem that it would be beneficial to require nodes to send 
a BFD packet with the new address as soon as it is changed to ensure that the 
peer is quickly made aware of the change.  It would also be important to 
document in the packet reception processing the point at which the new 
address should start being used (I assume at the same time the peer 
discriminator is set).  One scenario I would think that would benefit from 
this is for IS-IS neighbors.   

For OSPF and eBGP, the session staying up in the event of an IP address 
change, should not matter as the adjacencies will be torn down anyway. But in 
the case of static routes, if the address of the peer changes, the BFD 
session should go down.  Seeing that this is the case, it would seem 
appropriate to only allow the IP address change when ALL routing protocols 
using the BFD session support it or don't care.

What do you think?

Thanks,

Chris