make header format diagram 16 bit wide instead of 17

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

diff --git a/doc/txt/tep124.txt b/doc/txt/tep124.txt
index 0e8c24137fc3789f8f7c25e34c1d888f938cb317..3a16cfe9128ce91d86f7327015a9af3ee91ba97e 100644 (file)
--- a/doc/txt/tep124.txt
+++ b/doc/txt/tep124.txt
@@ -1,6 +1,6 @@
-============================
+============================================================================
 The Link Estimation Exchange Protocol (LEEP)
-============================
+============================================================================
 
 :TEP: 124 
 :Group: Network Protocol Working Group 
@@ -34,10 +34,10 @@ 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. These in-bound link
-qualities are exchanged among the neighbors using LEEP to determine
-the out-bound link qualities. Bi-directional link quality is computed
-using thus learned in-bound and out-bound link qualities.
+messages and 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.
 
 2. Definitions
 ============================================================================
@@ -45,11 +45,13 @@ using thus learned in-bound and out-bound link qualities.
 2.1 Link Quality
 --------------------------------------------------------------------
 
-Quality of the link between any two nodes describes the probability
-with which data link layer packets can be received without any
-error. This definition assumes uncorrelated link losses. The link
-between the nodes A and B may have different quality in A to B and B
-to A directions.
+The link quality between a directed node pair (A,B) is the probability
+that a packet transmitted by A will be successfully received 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.
 
 2.2 In-bound Link Quality
 --------------------------------------------------------------------
@@ -107,7 +109,7 @@ node identified by the data link source address.
 --------------------------------------------------------------------
 
 A LEEP frame has a header, the payload, and a footer with the Link
-Information (LI) entries as shown in this diagram:
+Information (LI) entries as shown in this diagram::
 
   -------------------------------------------------------------
   |   LEEP   | Payload | LI Entry | LI Entry | ... | LI Entry |
@@ -121,38 +123,42 @@ allowed by the data link layer. A LEEP frame can have 0 Link
 Information entry.
 
 3.3.1 LEEP header
+--------------------------------------------------------------------
+
+The following diagram shows the LEEP header format::
 
-The following diagram shows the LEEP header format:
                            1
-       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-      |nentry | rsrvd |      seqno      |
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |nentry | rsrvd |     seqno     |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
 
 Field definitions:
 
-nentry - Number of Link Information entries in the footer
-seqno - LEEP sequence number.
-rsrvd - Reserved and must be set to 0.
+  * nentry - Number of Link Information entries in the footer
+  * seqno - LEEP sequence number.
+  * rsrvd - Reserved and must be set to 0.
 
 
 3.3.2 Link Information Entry
+--------------------------------------------------------------------
+
+The following diagram shows the Link Information Entry format::
 
-The following diagram shows the Link Information Entry format:
                            1
-       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-      |             node id             |
-      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+      |            node id            |
+      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | link quality  |
       +-+-+-+-+-+-+-+-+
 
 Field definitions:
 
-node id: the link layer address of the neighbor
-link quality: The in-bound link quality from the node identified by node id
-   to the node that transmits this Link Information entry
+  * node id: the link layer address of the neighbor
+  * link quality: The in-bound link quality from the node identified by node id
+    to the node that transmits this Link Information entry
 
 
 4. Implementation