Subject: [manet] DYMO-04 Comment Solicitation

From: "Ian Chakeres" <[email-masked]>
Date: Thu, 16 Mar 2006 14:22:48 -0800

DYMO-04 is available at
http://www.ietf.org/internet-drafts/draft-ietf-manet-dymo-04.txt. 
Please take a  minute to read over the document before the meeting
next week.

DYMO has been updated to use the new packet/message format
(http://www.ietf.org/internet-drafts/draft-ietf-manet-packetbb-00.txt).
I highly recommend you read the generalized packet/message format,
since it may be used as a common building block in the other MANET WG
documents.

I will elaborate on the changes to DYMO during my presentation at IETF
65 in Dallas next week.

If you have any comments about DYMO-04, please email me.

Ian Chakeres

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From: Ramon Aguero <[email-masked]>
Date: Tue, 21 Mar 2006 12:45:45 +0100

Hello Ian, all...

at least I have a question/comment; I hope you can clarify it for me.

Lest imagine that you have a chain of nodes, with an ongoing communication 
*just in one direction*, i.e.:
S -> 1 -> 2 -> 3 -> 4 -> D

S_SeqNum = X and D_SeqNum = D

At a particular moment in time, node 3 disappears, and therefore 2 
generates the corresponding RERR that reaches both 1 and S (which make the 
corresponding route entry to D invalid). However, a new node appears 
(substituting 3); in fact this could be there from the beginning, it has 
not any impact:

S -> 1 -> 2 -> 6 -> 4 -> D

when S has a new data packet addressed to D, it has to trigger a new Route 
Discovery procedure, so it increments its SN:

S_SeqNum = X + 1

The RREQ is then propagated towards D and all nodes update their routing 
table entries to S, as far as the SN has increased. When D receives the 
RREQ, and generates the corresponding RREP it does _NOT_ (does it?) 
increment its own sequence number, because the Target.SeqNum that S set in 
the RREQ is Y and the Target.HopCount was 5 (the same as the the 
Orig.HopCount).

Then it sends the RREP to 4, but 4 has already a route entry towards D with 
the same SeqNum and therefore, the corresponding RoutingBlock is NOT stale 
(Route.SeqNum == Node.SeqNum) BUT it has to be disregarded (the route is 
still valid and Node.HopCnt == Route.HopCnt), as far as this Node.Address 
is the originator address, the packet has to be dropped and therefore it 
never reaches 6 nor the rest of nodes...

If this was a bi-directional communication this wouldn't happen, but with 
one-way flow ( e.g. any stream ) there may be a problem, as far as the new 
route would be only learnt when node 4 invalidates its route table entry to 
D (i.e. 5 seconds timeout).

Can you please clarify whether all my assumptions are correct? Would this 
situation happen as I've drafted?

Cheers,
Ramón