Subject: [manet] Routing protocol (DSR) guarentees of packet delivery

From: [email-masked] (Noah H. Miller)
Date: 13 Sep 2002 10:24:33 EDT

Hello,

What requirements must the routing protocol of a MANET fulfill with regard to packet delivery?  It seems there are no guarentees of 100% packet delivery or sequential packet delivery.  But my question pertains specifically to packet duplication: must a ro
uting protocol guarentee that no packets will be duplicated?

The question is also specific to a problem in DSR, draft 7.  DSR stores in a Maintenance Buffer all the packets that it has pushed down onto the MAC layer for delivery.  If the MAC layer notifies the Maintenance Buffer that a packet with next-hop address 
X failed, all the packets in the Maintenance Buffer with next-hop address X will be removed (section 4.5).  Now, consider the case of two packets pushed to address X.  Packet 1 fails, and both Packets 1 and 2 are removed from the Maintenance Buffer, salva
ged, and retransmitted on a different route with next-hop address Z.  However, Packet 2 with next-hop address X is still in the MAC layer waiting for delivery, now alongside Packet 2 with next-hop address Z.  Packet 2:X may actually be delivered, if node 
X moves back into contact, and so the destination of Packet 2 may receive two copies, one through X and one through Z.
Is this a problem with the draft?  Is there a correction to avoid this duplication?  Or does it not matter?

Thank you,
Noah Miller
ISTS, Dartmouth College
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