[manet] AODV: Confusion about signed comparison sequence numbers
Bart Braem <bart.braem@ua.ac.be> Fri, 29 October 2004 07:34 UTC
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From: Bart Braem <bart.braem@ua.ac.be>
To: manet@ietf.org
Date: Fri, 29 Oct 2004 09:10:42 +0200
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Subject: [manet] AODV: Confusion about signed comparison sequence numbers
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I am having a problem understanding chapter 6.1 of the AODV RFC: how does the comparison of sequence numbers work: "This comparison MUST be done using signed 32-bit arithmetic, this is necessary to accomplish sequence number rollover. If the result of subtracting the currently stored sequence number from the value of the incoming sequence number is less than zero, then the information related to that destination in the AODV message MUST be discarded, since that information is stale compared to the node's currently stored information." Now I don't understand why it's not the other way round: when the value is larger than zero, then ... Because when I have to number that are smaller than 2^31-1 they have their most significant bit on 0. Then, according to what I know and can find, the unsigned and the signed integer value are the same. So what's written in the RFC is: if the currently stored sequence number is smaller then the incoming sequence number (their difference is negative), then the newer information MUST be discarded? I know there must be a mistake in my reasoning, but where? Thanks a lot for any information, Bart _______________________________________________ manet mailing list manet@ietf.org https://www1.ietf.org/mailman/listinfo/manet
- [manet] AODV: Confusion about signed comparison s… Bart Braem
- Re: [manet] AODV: Confusion about signed comparis… Bart Braem
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