Subject: Question on Route expiration timer

From: George Aggelou <[email-masked]>
Date: Tue, 14 Dec 1999 14:05:57 +0000

Dear MANET-All,
 
I have a question on the route lifetime timer.
 
- Scenario:  Upon a call arrival at some node A, if A does not have a
route to route the call to its destination (DEST) it initiates a Route
Discovery process if one is not pending for the same destination. 
Saythat before the Route Discovery timeout period a valid Route Reply is
received.  If this happens a route entry for DEST is added in A's
routing table and the entry's lifetime is set to  (now +
Route_Lifetime).  From this point, node A can send all new and pending
packets to DEST.
 
However a problem arises when the call duration is greater than the
Route_Lifetime (which is often the case!).  This is because, even though
the newly discovered route may be functioning well until *and after* its
expiration, node A must proceed and delete it from its table and a new
route should be re-discovered to route the packets of the active call in
progress.  
 
- The question:  Is this the approach that you all follow?  I mean,
there should be some means for the source of data (node A) to be
receiving some feedback (e.g., from DEST) for the route in use, so as to
be able to figure out whether the active route is still functioning or
not and, hence, for the scenario described above, to update the
Route_Lifetime of the pending route. Therefore, it avoids the route
discovery "hassle" in the case where the pending route seems to be still
valid!   

- Here is an alternative: As long as a call is in progress do not delete
a pending route *as long as* no failure messages are reported back to
the source for this route.  However, I believe this is an aggressive use
of soft-state protocols!

If any of you has proposed (or can suggest now!) any alternative on this
issue please drop a line.

Regards,
George A.

-- 
*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.     
George Aggelou			     	
Centre for Communications Systems Research   
Mobile Communications Research Group      		
University of Surrey  		     

http://www.ee.surrey.ac.uk/Personal/G.Aggelou
*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.

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From: Miguel Sanchez <[email-masked]>
Date: Tue, 14 Dec 1999 16:46:38 +0100

Hi George,

Here is my line:

As long as a route is performing well, you could *extend* its lifetime.
Either there is call in progress or not (er ... a connection). Therefore,
when a route is delivering traffic, it is getting a lifetime extension or
refresh. You still will need a timer to remove it from your routing table
after a certain amount of time without being used (based on the idea that
the probability of being valid yet is low after some time).

I think this is close to your alternative proposal.

Regards,

Miguel

--
Miguel Sanchez Lopez                            |       [email-masked]
Universidad Politecnica de Valencia             | voice:+3496 387 9700
Camino de Vera, 14                              | fax:  +3496 387 7579
46071 VALENCIA (Spain)                          |