Subject: [manet] DYMO routing information's usefulness

From: "Romain Thouvenin" <[email-masked]>
Date: Mon, 26 Feb 2007 13:12:28 +0100

Hi,

You'll probably show me that I am wrong, but it seems that there is a
mistake in DYMO specs, sections 5.2.1.3 and 5.2.1.4.

In the text of 5.2.1.3, the information is supposed to be inferior if
Node.HopCnt >= Route.HopCnt (for a non-broken route during a RREQ),
but according to the pseudo-code test, it is when Node.HopCnt >
Route.HopCnt.

The completeness test in 5.2.1.4 agrees with the test of 5.2.1.3, and
thus disagrees with the text. But I would have thought that equivalent
information must be discarded during a RREQ because even if it
loop-free, the information will be forwarded twice by each node on the
rest of the path toward the target node. This seems to be confirmed on
a small example. Did I miss something ?

Thanks for your clarifications,
Romain

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From: "Romain Thouvenin" <[email-masked]>
Date: Mon, 26 Feb 2007 13:25:16 +0100

> Thanks for your clarifications,

Oh maybe it is because we want to let nodes receive additional
information added to the different RMs ?
But in this case, the target node will issue several RREP, won't it ?

Romain

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From: "Ian Chakeres" <[email-masked]>
Date: Mon, 26 Feb 2007 08:09:09 -0800

Excellent catch. I'll correct the pseudo code to match the text.

Ian Chakeres

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From: Henner Jakob <[email-masked]>
Date: Wed, 28 Feb 2007 13:55:18 +0100

I do have some problems with the 'superior check' aswell.

Superior routes:
The first part checks if the new information has a higher sequence number. If so, it is superior.
In the second part the hop count is checked the same way for RREQs and RREPs, though within the inferior check they are handled different. Why they do differ in the Route.Broken flag I do not understand.
The third part is wrong. The sequence number is not checked, so it's possible an information with lower sequence number is marked superior.
If you put another pair of brackets to check if the sequence number are equal, it's still wrong. If the route is not broken, and the new route has the same hop count, it is inferior in case of a RREQ!
Maybe in the third part it should be Route.Broken == true.

For now I will use the negated form of stale, loop-possible and inferior information to determine if it's superior. It's longer, but I think it's correct.

regards,
Henner Jakob

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From: "Ian Chakeres" <[email-masked]>
Date: Wed, 28 Feb 2007 07:34:26 -0800

I've already revised the superior pseudo-code. Does this look right to you?

   (Node.SeqNum - Route.SeqNum > 0) OR
   ((Node.SeqNum == Route.Seqnum)
    AND (Node.HopCnt <= Route.HopCnt + 1)
    AND ((Route.Broken == true)
        OR ((Node.HopCnt < Route.HopCnt)
           AND (RM is RREQ))))

Ian