Re: [Manet-dt] DYMO Routing Information Freshness Check

In the previous version since comparison with a valid routing entry is
even more strict (Node.HopCnt > Route.HopCnt), the statement was not
required.

This version makes it very explicit which information is stale,
loop-prone, inferior (but still loop-free) and fresh.

Ian

On 6/26/06, Koojana Kuladinithi <koo@comnets.uni-bremen.de> wrote:
> Hi Ian,
>
> Under the Node.SeqNum == Route.SeqNum condition, you now assume that RM
> information is loop prone, if If Node.HopCnt >
>       Route.HopCnt + 1,.
>
> In the earlier version, you have checked the above condition when
> comparing only with invalid routes. Now, you are doing it for both valid
> & invalid route info. Is there any reason that you have changed this?
>
> Koojana
>
> > -----Original Message-----
> > From: Ian Chakeres [mailto:ian.chakeres@gmail.com]
> > Sent: 25 June 2006 22:16
> > To: Koojana Kuladinithi
> > Cc: manet-dt@ietf.org
> > Subject: Re: [Manet-dt] DYMO Routing Information Freshness Check
> >
> >
> > About the second part of your email. I've revised that area
> > (inferior). Here is the new text. This allows Node.SeqNum ==
> > Route.SeqNum+1 if the route is invalid. It also allows
> > Node.SeqNum == Route.SeqNum if the message is a RREP. I might
> > be missing a case, please give it a read and let me have your
> > comments.
> >
> > 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.  If the
> >       route is valid, then the new information is also inferior if
> >       Node.HopCnt == Route.HopCnt AND this RM 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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