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[Manet-dt] DYMO Routing Information Freshness Check

"Ian Chakeres" <ian.chakeres@gmail.com> Sat, 24 June 2006 17:01 UTC

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Date: Sat, 24 Jun 2006 10:01:07 -0700
From: "Ian Chakeres" <ian.chakeres@gmail.com>
To: manet-dt@ietf.org
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Subject: [Manet-dt] DYMO Routing Information Freshness Check
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In DYMO when a RREQ/RREP is received a node needs to check whether the
information is fresh. In the soon to be released new version I have
revised the description of the process (and categories) for routing
information freshness.

I would like you comments before submitting the ID. Please let me know
if you suggest any changes.

Thanks.
Ian

5.2.1.  Judging New Routing Information's Usefulness

   Given a routing table entry (Route.SeqNum, Route.HopCnt, and
   Route.ValidTimeout) and new routing information for a particular node
   in a RM (Node.SeqNum, Node.HopCnt, and RM message type - RREQ/RREP),
   the quality of the new routing information is evaluated to determine
   its usefulness.  The following comparisons are performed in order:

   1. Stale
      If Node.SeqNum - Route.SeqNum > 0 (using signed 16-bit arithmetic)
      the information is stale.  Using stale routing information is not
      allowed, since doing so might result in routing loops.

   2. Loop-prone
      If Node.SeqNum = Route.SeqNum the information maybe loop-prone,
      additional information must be examined.  If Route.HopCnt is
      unknown or set to zero (0), then the routing information is loop-
      prone.  Likewise, if Node.HopCnt is unknown or set to zero (0),
      then the routing information is loop-prone.  If Node.HopCnt >
      Route.HopCnt + 1, then the routing information is loop-prone.
      Using loop-prone routing information is not allowed, since doing
      so might result in routing loops.

   3. Inferior
      If Node.SeqNum == Route.SeqNum the information may be inferior,
      additional information must be examined.  If the route is valid
      (by examining Route.ValidTimeout and the current time), then the
      new information is inferior if Node.HopCnt > Route.HopCnt.
      Additionally, if the route is valid, then the new information is
      inferior if Node.HopCnt == Route.HopCnt and the Message containing
      the new information is a RREQ.

   4. Fresh
      Routing information that does not match any of the above criteria
      is loop-free and better than the information existing in the
      routing table.  This information should be used to update the
      routing table.

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