Subject: [manet] AODVv2 Lost SeqNum handling and boot period

From: "Mercieca, Victoria" <[email-masked]>
Date: Mon, 23 Feb 2015 16:31:00 +0000

Hi all,

I have a few comments on the behaviour of an AODVv2 router when it loses its sequence number (and the same behaviour applies at boot time too). I wonder if anyone else has any thoughts?

When our router has lost its SeqNum, we want to avoid any renewal of routes we originated, i.e. routes to our Router Clients. Those are the only routes in the network associated with our old SeqNum.

1. Why would we not forward RREQ or RREP originated by another router? These don't renew any information relating to the router's own SeqNum.

2. Similar to point 1, if the router's SeqNum is lost, why would it mark the routes it has learned so far as Invalid? They have nothing to do with the lost SeqNum. We can safely forward data to other destinations. The router could actually still forward data packets to its Router Clients, as long as SeqNum information about those routes is deleted from other routers at MAX_SEQNUM_LIFETIME after it was learned.

3. If all routes are marked as Invalid on a router with lost SeqNum, what happens if during the wait period, RREQs and RREPs are received? The draft says they get processed, so they should update the route state from Invalid. The router is not allowed to regenerate the RteMsg, but can it use those routes to forward packets? Or do we need to check before forwarding a packet that we are not in the lost SeqNum wait period? Would we buffer any arriving packets, or send RERR?

4. As an optional feature, should the router store any RREQs it would have responded to if it wasn't in the waiting period, and respond to them after the MAX_SEQNUM_LIFETIME timeout? Otherwise, other routers could have sent RREQs which were ignored, and reached the maximum number of retries and be waiting the RREQ_HOLDDOWN_TIME before retrying, delaying the restart in connectivity.

5. I know the idea of sending a RERR about a router client doesn't quite make sense, but hypothetically, if we were to send a RERR about all our Router Clients when we realise our SeqNum is lost, could the special sequence number of zero be used in the RERR to indicate that routers receiving the RERR should reset or delete any previous information? Then we can start using our new SeqNum sooner? We might not be able to rely on this RERR reaching all the routers in the network though.

Any comments are welcome.

Regards,
Victoria Mercieca

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