RC4 fixes for Epic support

[tinyos-2.x.git] / doc / txt / tep124.txt

diff --git a/doc/txt/tep124.txt b/doc/txt/tep124.txt
index bfd198ceadf808cb18d2daebe0ec3cd765df6759..b57e503668d1beaa8f08bba427c1695645ef9396 100644 (file)
--- a/doc/txt/tep124.txt
+++ b/doc/txt/tep124.txt
@@ -5,8 +5,8 @@ The Link Estimation Exchange Protocol (LEEP)
 :TEP: 124 
 :Group: Network Protocol Working Group 
 :Type: Documentary
-:Status: Draft
-:TinyOS-Version: 2.x
+:Status: Final
+:TinyOS-Version: > 2.1
 :Author: Omprakash Gnawali
 
 :Draft-Created: 05-Feb-2006
@@ -34,14 +34,14 @@ links to the neighbors.
 Routing protocols often require bi-directional link qualities to
 compute the routes. Nodes can estimate the quality of the in-bound
 link from a neighbor by estimating the ratio of successfully received
-messages and the total transmitted messages. LEEP appends in-bound
+messages to the total transmitted messages. LEEP appends in-bound
 packet reception rate (PRR) estimates to packets. Other nodes hearing
 these packets can combine the in-bound PRR values with their own
 in-bound values to compute bi-directional link quality. Thus, LEEP is
 a discovery and link table bootstrapping mechanism. The link quality
 is often fine-tuned using different mechanisms.
 
-Link quality estimates obtained using LEEP are often used as a
+Link quality estimates obtained using LEEP are often used as
 bootstrapping values in the link quality table; data transmission
 statistics can later be used to make these estimates more accurate.
 
@@ -53,8 +53,12 @@ statistics can later be used to make these estimates more accurate.
 
 In a node pair (A,B), with B as the node of reference, in-bound link
 quality is a value in the range of 0 to 255 that describes the quality
-of the link from A to B estimated by B by counting the successfully
-received packets from A among all the packets transmitted by B.
+of the link from A to B estimated by B as the ratio of successfully
+received to all packets transmitted by A. Thus, in-bound link quality
+is the empirical probability that a packet will be successfully
+received on a given link. A value of 255 represents a probability of 1
+and a value of 0 represents a probability of 0 of successfully
+receiving a packet on a given link.
 
 2.2 Out-bound Link Quality
 --------------------------------------------------------------------
@@ -65,16 +69,16 @@ determine the out-bound link quality if A advertises its in-bound link
 qualities. LEEP is the protocol that is used to exchange the in-bound
 link qualities.
 
-2.3 Link Quality
+2.3 Bi-directional Link Quality
 --------------------------------------------------------------------
 
-The link quality between a directed node pair (A,B) is the probability
-that a packet transmitted by A will be successfully received and
-acknowledged by B. The bidirectional link quality of an undirected
-node pair (A,B) is the product of the link quality of (A,B) and
-(B,A). This definition assumes independent link losses. It also
-includes the case when the link quality of (A,B) and (B,A) are
-different; this can occur due to local interference or noise.
+LEEP does not define or compute bi-directional link quality. LEEP
+provides a way to exchange sufficient information to compute in-bound
+and out-bound link qualities. These two link qualities can be used to
+compute the bi-directional link quality. Routing protocols often
+compute the bi-directional link quality of a node pair (A,B) as a
+function (product, min, etc.) of the link quality of (A,B) and (B,A).
+
 
 2.4 Link Information Entry
 --------------------------------------------------------------------