Razvans comments

diff --git a/doc/txt/tep123.txt b/doc/txt/tep123.txt
index 477d87dc30f3645e81918cea8f646445705e6db2..942a24f9b8962b37081d48376cb46f8ea0444de7 100644 (file)
--- a/doc/txt/tep123.txt
+++ b/doc/txt/tep123.txt
@@ -31,6 +31,18 @@ collection roots in a network.
 1. Introduction
 ==============================================================================
 
 1. Introduction
 ==============================================================================
 

+A collection protocol delivers data to one of possibly several data
+sinks, providing a many-to-one network layer. Collection is a
+fundamental component of most sensor network applications. The
+Collection Tree Protocol (CTP) is a reference Collection protocol in
+TinyOS 2.x. The users use Collection interfaces described in TEP 119
+[3]_ to use CTP in their applications.
+
+In this TEP, after a brief discussion of Collection and CTP, we
+specify the CTP routing and data frames. CTP uses routing frames to
+update and build collection tree in the network. CTP uses data frames
+to deliver application payload to the sink.
+

 2. Assumptions and Limitations
 ==============================================================================
 
 2. Assumptions and Limitations
 ==============================================================================
 


@@ -93,13 +105,17 @@ is to not consider routes with an ETX higher than a reasonable constant.
 The value of this constant is implementation dependent.
 
 Packet duplication is an additional problem that can occur in CTP.
 The value of this constant is implementation dependent.
 
 Packet duplication is an additional problem that can occur in CTP.

-Packet duplication occurs when a node receives a data frame successfully
-and transmits an ACK, but the ACK is not received. The sender retransmits
-the packet, and the receiver receives it a second time. This can have
-disasterous effects over multiple hops, as the duplication is exponential.
-For example, if each hop on average produces one duplicate, then on the
-first hop there will be two packets, on the second there will be four,
-on the third there will be eight, etc.
+Packet duplication occurs when a node receives a data frame
+successfully and transmits an ACK, but the ACK is not received. The
+sender retransmits the packet, and the receiver receives it a second
+time. This can have disasterous effects over multiple hops, as the
+duplication is exponential.  For example, if each hop on average
+produces one duplicate, then on the first hop there will be two
+packets, on the second there will be four, on the third there will be
+eight, etc. CTP keeps a small cache of packet signature for the
+packets it has seen to detect packet duplicates. When a new packet
+arrives, if its signature results in cache hit, CTP drops the packet
+because it is a duplicate.

 
 Routing loops complicate duplicate suppression, as a routing loop may
 cause a node to legitimately receive a packet more than once. Therefore,
 
 Routing loops complicate duplicate suppression, as a routing loop may
 cause a node to legitimately receive a packet more than once. Therefore,


@@ -131,7 +147,7 @@ The CTP data frame format is as follows::
 
 Field definitions are as follows:
 
 
 Field definitions are as follows:
 

-  * P: Routing pull. The P bit allows nodes to request routing information from other nodes. If a node with a valid route hears a packet with the P bit set, it SHOULD transmit a routing frame in the near future.
+  * P: Routing pull. The P bit allows nodes to request routing information from other nodes. If a node with a valid route hears a packet with the P bit set, it SHOULD transmit a routing frame in the near future. Data frames are unicast so only the destination of the unicast transmission responds to the P bit in the data frame.

   * C: Congestion notification. If a node drops a CTP data frame, it MUST set the C field on the next data frame it transmits.
   * THL: Time Has Lived. When a node generates a CTP data frame, it MUST set THL to 0. When a node receives a CTP data frame, it MUST increment the THL. If a node receives a THL of 255, it increments it to 0.
   * ETX: The ETX routing metric of the single-hop sender. When a node transmits a CTP data frame, it MUST put the ETX value of its route through the single-hop destination in the ETX field.  If a node receives a packet with a lower gradient than its own, then it MUST schedule a routing frame in the near future.
   * C: Congestion notification. If a node drops a CTP data frame, it MUST set the C field on the next data frame it transmits.
   * THL: Time Has Lived. When a node generates a CTP data frame, it MUST set THL to 0. When a node receives a CTP data frame, it MUST increment the THL. If a node receives a THL of 255, it increments it to 0.
   * ETX: The ETX routing metric of the single-hop sender. When a node transmits a CTP data frame, it MUST put the ETX value of its route through the single-hop destination in the ETX field.  If a node receives a packet with a lower gradient than its own, then it MUST schedule a routing frame in the near future.


@@ -170,7 +186,7 @@ The CTP routing frame format is as follows::
 
 The fields are as follows:
   
 
 The fields are as follows:
   

-  * P: Same as data frame.
+  * P: Same as data frame with one difference: Routing frames are broadcast so multiple nodes respond to the P bit in the routing frame.

   * C: Congestion notification. If a node drops a CTP data frame, it MUST set the C field on the next routing frame it transmits.
   * parent: The node's current parent.
   * metric: The node's current routing metric value.
   * C: Congestion notification. If a node drops a CTP data frame, it MUST set the C field on the next routing frame it transmits.
   * parent: The node's current parent.
   * metric: The node's current routing metric value.


@@ -185,6 +201,8 @@ below its own. When a parent hears a child advertise an ETX below its
 own, it MUST schedule a routing frame for transmission in the near
 future.
 
 own, it MUST schedule a routing frame for transmission in the near
 future.
 

+A node MUST send CTP routing frames as broadcast messages.
+

 6. Implementation
 ==============================================================================
 
 6. Implementation
 ==============================================================================
 


@@ -341,7 +359,4 @@ along the path.
        Self-Regulating Algorithm for Code Maintenance and Propagation
        in Wireless Sensor Networks." In Proceedings of the First USENIX
        Conference on Networked Systems Design and Implementation (NSDI), 2004.
        Self-Regulating Algorithm for Code Maintenance and Propagation
        in Wireless Sensor Networks." In Proceedings of the First USENIX
        Conference on Networked Systems Design and Implementation (NSDI), 2004.

-       
- 
-
-
+.. [3] TEP 119: Collection.