Subject: Re: [manet] #20 (aodvv2): Idle routes must be marked as active after re-use

From: "manet issue tracker" <[email-masked]>
Date: Tue, 23 Dec 2014 22:02:17 -0000

#20: Idle routes must be marked as active after re-use

Changes (by [email-masked]):

 * status:  new => closed
 * resolution:   => fixed

Comment:

 On 4/11/2014 6:21 PM, Charles E. Perkins wrote:

 > Here is some proposed text to resolve this issue:
  ...
 > Proposal: after the text:
 >> When a route is no longer Active, it
 >>         becomes an Idle route.
 >
 > The proposed text:
 >>         If an Idle route is used to forward a packet, it becomes
 >>         an Active route once again.
 >
 >
 > However, there may be a better solution which requires more extensive
 changes.
 > While the distinction between an active route and an idle route is
 interesting
 > to consider, the main difference between them is that an idle route is
 > preferred for deletion whenever space needs to be reclaimed.  The same
 effect
 > can be had by specifying that route table memory space be reclaimed by
 > deleting the oldest routes first.  I think this will produce some
 > simplification to the text without any real loss of clarity.

 ============================================================================

 On 4/30/2014 2:44 AM, Martin Heusse wrote:
 >
 > Does this really belong to the protocol specification? To me, if a node
 runs
 > out of memory space, it's a local decision to remove a route or the
 other.
 > The protocol will still operate properly. Granted, it's more efficient
 if
 > everyone follows pretty much the same policy :-)
 >
 > Now, removing the oldest route may not be the best idea: it's not
 unlikely
 > that the first route a "node" creates is the most important!
 >
 > Maybe a statement like: "routers should discard routes in order of least
 > recent usage" could be enough?
 > (And then, you don't have to care about idle/inactive/active route
 status.
 > This information is not exchanged between nodes, anyway.)

 ============================================================================

 On 5/28/2014 10:29 AM, Charles E. Perkins wrote:
 >
 > Hello Martin,
 >
 > Your points are well taken.  However, the "active status" of a route
 > is important when determining whether or not to report it as
 > broken.  Routes that are inactive don't need to be included in an
 > RERR message even if the next hop link is broken.  The way that
 > AODVv2 determines whether a route is active or not, is by
 > keeping track of how recently it has been used.
 >
 > Less important, but still with some value, is the distinction
 > between idle routes and expired routes.  An idle route can be
 > used to forward packets, and an expired route cannot.  However,
 > even an expired route contains one valuable field, namely the
 > latest known sequence number.  If there is no penalty, it can
 > be useful to keep that information in case there are some old
 > RREQ packets still being retransmitted (say, because of really
 > full queues at some nodes in the network).  This situation is
 > rare, but Murphy's law demands that it happen sometimes.
 > I don't believe there is any significant penalty for trying to
 > prevent it.
 >
 > Finally, there comes a time when even the sequence number
 > is potentially harmful.  This happens when it is so old that it
 > might have been duplicated by the node after rebooting.
 > It was shown some years ago that sequence numbers have to
 > be expunged after a time equal to the hold-down time for nodes
 > after reboot (MAX_SEQNUM_LIFETIME).

 ====================================================================

 No further problems have been identified with this solution, so it is
 proposed to close the issue.

-- 
-----------------------------------+------------------------------------
 Reporter:  [email-masked]  |       Owner:  [email-masked]
     Type:  defect                 |      Status:  closed
 Priority:  minor                  |   Milestone:
Component:  aodvv2                 |     Version:
 Severity:  Active WG Document     |  Resolution:  fixed
 Keywords:  idle route             |
-----------------------------------+------------------------------------

Ticket URL: <http://trac.tools.ietf.org/wg/manet/trac/ticket/20#comment:1>
manet <http://tools.ietf.org/manet/>