Re: [Roll] Some confusions in RFC 6719 (MRHOF)
Duong Ngoc Nguyen <nduong@purdue.edu> Thu, 29 November 2012 13:45 UTC
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Date: Thu, 29 Nov 2012 08:45:14 -0500
From: Duong Ngoc Nguyen <nduong@purdue.edu>
To: Philip Levis <pal@cs.stanford.edu>
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Cc: roll@ietf.org
Subject: Re: [Roll] Some confusions in RFC 6719 (MRHOF)
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Thanks. Sincerely, Duong Nguyen ----- Original Message ----- > From: "Philip Levis" <pal@cs.stanford.edu> > To: "Duong Ngoc Nguyen" <nduong@purdue.edu> > Cc: roll@ietf.org > Sent: Wednesday, November 28, 2012 4:27:25 PM > Subject: Re: [Roll] Some confusions in RFC 6719 (MRHOF) > Phil > > On Nov 7, 2012, at 11:55 AM, Duong Ngoc Nguyen wrote: > > > As I work with MRHOF, I find some statements are not consistent that > > I cannot resolve by myself. I'm very grateful if someone can help me > > overcome this confusion. > > > > 1. Which path cost is carried in Metric Container? > > > > Section 3.2.2 states: > > > > Once the preferred parent is selected, the node sets its > > cur_min_path_cost variable to the path cost corresponding to the > > preferred parent. The value of the cur_min_path_cost is carried in > > the Metric Container corresponding to the selected metric when DIO > > messages are sent. > > > > ==> it suggests Metric Container carries the cost through the best > > (i.e. preferred) parent. > > > > While section 3.4 states: > > > > Once the preferred parent is selected, the node sets its > > cur_min_path_cost variable to the path cost corresponding to its > > preferred parent. It then calculates the metric it will advertise > > in > > its metric container. This value is the path cost of the member of > > the parent set with the highest path cost. Thus, while > > cur_min_path_cost is the cost through the preferred parent, a node > > advertises the highest cost path from the node to the root through > > a > > member of the parent set. The value of the highest cost path is > > carried in the metric container corresponding to the selected > > metric > > when DIO messages are sent. > > > > ==> it suggests Metric Container carries the cost through the worst > > parent. > > 3.4 is correct. > > > 2. Which value is written to Rank field of DIO messsage's base > > object in case ETX is used? > > > > When ETX is the metric, node must not include Metric container, thus > > the rank field in DIO's base object is the only information to > > advertise to neighbors. > > > > Section 3.4 states: > > > > If ETX is the selected metric, a node MUST NOT advertise it in a > > metric container. Instead, a node MUST advertise an approximation > > of > > its ETX in its advertised Rank value, following the rules > > described > > in Section 3.3... > > > > ==> The phrase "in its advertised Rank value, following the rules > > described in Section 3.3." means we would write the value of node > > rank (computed by rules in section 3.3) into the rank field of DIO > > message. > > > > On the other hand, section 3.5 states: > > > > ... Once parent selection and rank computation is performed > > using the ETX metric, the node advertises the Rank and MUST NOT > > include a metric container in its DIO messages. While assigning > > Rank > > in this case, use the representation of ETX described in > > [RFC6551], > > i.e., assign Rank equal to ETX * 128. > > > > ==> The phrase "assign Rank equal to ETX * 128" suggests that we > > should write value of ETX of path cost to the rank field of DIO > > message. > > > > 3.4 is correct. The term "assign" is meant to describe the > transformation between ETX and rank values, not the Rank in the DIO. > > Phil
- [Roll] Some confusions in RFC 6719 (MRHOF) Duong Ngoc Nguyen
- Re: [Roll] Some confusions in RFC 6719 (MRHOF) Philip Levis
- Re: [Roll] Some confusions in RFC 6719 (MRHOF) Duong Ngoc Nguyen