On Jun 15, 2008, at 8:54 PM, jiwen zhang wrote:
> Hello Omprakash :
> I have some questions about the interface CtpInfo .
> Firstly , i am puzzled to the meaning of some fields in
> routetable.
> in the structure routing_table_entry (TreeRouting.h), there are
> some information of the current node . the field of parent in
> route_info_t should be the parent of one neighbor in the
> routetable , and what does the ETX mean ? is it the the neighbor's
> parent's EXT or the neighbor's the ETX ?(the EXT here should be the
> path metric to the root??) .
>
> i have seen the implementation of CtpInfo in CtpRoutingEngineP,
> and i have interest to the command which get the neighbors'
> information.
> command uint16_t CtpInfo.getNeighborLinkQuality(uint8_t n) {
> return (n < routingTableActive)? call
> LinkEstimator.getLinkQuality(routingTable[n].neighbor):0xffff;
> }
> command uint16_t CtpInfo.getNeighborRouteQuality(uint8_t n) {
> return (n < routingTableActive)? call
> LinkEstimator.getLinkQuality(routingTable[n].neighbor) +
> routingTable[n].info.etx:0xfffff;
> }
> in my opinion , the command of getNeighborLinkQuality returns a
> value of the quality between the current node and this neighbor in
> the routetable .
> if the field of ETX in route_info_t is the neighbor's EXT to the
> root , i think the command getNeighborRouteQuality returns a value
> of path metric between the current node and the root node through
> this neighbor (which is the sum of this neighbor's ETX to the root
> and the quility between the current node and the neighbor node).
>
> the command Ctp.getEtx(uint16_t* etx) will return the value of the
> path metric between the current node and the root through the node's
> parent. i find there are some differencs with the way in
> CtpInfo.getNeighborRouteQuality.
> *etx = routeInfo.etx + evaluateEtx(call
> LinkEstimator.getLinkQuality(routeInfo.parent));
> and the function evaluateEtx() is
> uint16_t evaluateEtx(uint16_t quality) {
> return (quality + 10);
> }
>
> i don't know whether i have expressed the problem distinctly , i
> think the two ways have the difference of "10" . am i
> right ,Omprakash ? can you give me an explain?
They do. If you read the LEEP and CTP TEPs, they talk about this. CTP
advertises route ETX as a 16-bit fixed point number with two decimal
fractional digits. I.e., the ETX*100. LEEP advertises link ETX as an 8-
bit fixed point number with one decimal fractional digit. I.e., the
ETX*10.
Phil
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