Re: [Roll] MRHOF ETX

Philip Levis <pal@cs.stanford.edu> Fri, 08 June 2012 17:36 UTC

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From: Philip Levis <pal@cs.stanford.edu>
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Date: Fri, 8 Jun 2012 10:36:09 -0700
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To: "Reddy, Joseph" <jreddy@ti.com>
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Subject: Re: [Roll] MRHOF ETX
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On Jun 8, 2012, at 10:24 AM, Reddy, Joseph wrote:

> The advertised Rank of the parent is a 16-bit value that has integer and fractional parts. The MinHopRankIncrease parameter determines the length of the Integer/Fraction parts. 

I think you're misreading MRHOF, and misinterpreting MinHopRankIncrease. The MRHOF draft tries to be very explicit about this. MRHOF with ETX encodes the ETX in Rank, but MinHopRankIncrease can change the computation. If MinHopRankIncrease is greater than 128, then Rank no longer really encodes a fixed-point version of ETX, it encodes ETX plus a per-hop penalty.

> Now when the draft says to add the Rank and link ETX parameters, clearly this cannot be a simple addition of the Rank with either ETX or (ETX*128). Instead, the ETX value must be converted to the same Integer/Fraction representation as the Rank ( i.e., using MinHopRankIncrease )

Disagree -- the draft is pretty explicit on what you do, and it's not this.

Phil