The MPLS WG Archive

[Gaitonde Anandprasanna <prasanna@csa.iisc.ernet.in>]

I have some doubts about the Hello Message extension of RSVP-TE
Draft of RSVP-TE 07.txt

One basic doubt is this :


 If no Instance values are received, via either REQUEST or ACK
   objects, from a neighbor within a configured number of
   hello_intervals, then a node MUST presume that it cannot communicate
   with the neighbor.  The default for this number is 3.5.   


>From this paragraph i feel that if my nighbour does not support Hello
messages then obviosly he will just discrad  them and i wont get any
response to my Hello request messages. the i mght consider the
communication to be lost. Though this is not the case .
 I am confused about this??

And as per the above argument even the part of the draft(shown below)is
not well understood by me.


 The Hello extension is specifically designed so that one side can use
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   the mechanism while the other side does not.  Neighbor failure
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   detection may be initiated at any time.  This includes when neighbors
   first learn about each other, or just when neighbors are sharing Resv
   or Path state.


Please let me know.

Second difficulty:

Please refer Section 5.3:


 The receiver of a HELLO REQUEST object SHOULD also verify that the
   neighbor is reflecting back the receiver's Instance value.  This is
   done by comparing the received Dst_Instance field with the
   Src_Instance field value most recently transmitted to that neighbor.
   If the neighbor continues to advertise a wrong non-zero value after a
   configured number of intervals, then the node MUST treat the neighbor
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   as if communication has been lost. 

And one more paragraph for ACK meesages

 The receiver of a HELLO ACK object MUST also verify that the neighbor
   is reflecting back the receiver's Instance value.  If the neighbor
   advertises a wrong value in the Dst_Instance field, then a node MUST
   treat the neighbor as if communication has been lost. 

In this paragraph there is no menion of whether we should wait for some
number of hello intervals before considering the communication to be
lost.??
I think we should consider the number of hello intervals here also right??




Thanx in advance


Pras