[Manet-dt] DYMO SeqNum Decisions

["Ian Chakeres" <[e-mail]>]

As an exercise in ensuring dymo sequence numbers work properly, I've
created a few slides discussing important dymo sequence number
decisions.

Pages 1 & 2 talk about judging routing information usefulness. The
goal is to not have loops, while not requiring nodes to increment
their OwnSeqNum unless absolutely necessary. Incrementing OwnSeqNum
essentially disqualifies existing routing information in the network
that may not be bad.

Pages 3 & 4 talk about incrementing OwnSeqNum. Since nodes issuing
RREQ don't know the state of routing tables at intermediate nodes,
they need to increment their sequence number. Otherwise, receiving
nodes might discard this information. The target on the other hand has
more information from the RREQ message (last known values and some
information about the route traversed). The target can use this
information to optimize sequence number incrementing.

Intermediate nodes that append their routing information have two
options, updating their sequence number and ensure it will be fresh at
other nodes, or not.  If the sequence number is not incremented it
might not be considered fresh by intermediate nodes. It is not clear
what the recommended procedure should be. Please make a suggestion. I
suggest incrementing OwnSeqNum.

Page 5 talks about the cases when an Intermediate node could reply.
Currently we don't define intermediate node replies, but it is a
useful concept. One more thing, I've introduced a concept "MaxAge"
which is the maximum amount of time a piece of routing information can
be maintained. This is to assist in reboots, by having a hard deadline
on the maximum amount of time that a node must wait before
participating.

Please review the flowcharts and let me know if something doesn't make
sense or is wrong.

Ian Chakeres

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