phils comments

diff --git a/doc/txt/tep123.txt b/doc/txt/tep123.txt
index 942a24f9b8962b37081d48376cb46f8ea0444de7..55c85930354c6f6bf797194c97ab3d8b0ea22d48 100644 (file)
--- a/doc/txt/tep123.txt
+++ b/doc/txt/tep123.txt
@@ -66,13 +66,17 @@ neighbors. These provide an estimate of the number of transmissions it
 takes for the node to send a unicast packet whose acknowledgment is
 successfully received.
 
 takes for the node to send a unicast packet whose acknowledgment is
 successfully received.
 

-CTP has several mechanisms in order to improve delivery reliability,
-but it does not promise 100\% reliable delivery. It is best effort, but
-a best effort that *tries very hard.*
+CTP has several mechanisms in order to achieve high delivery
+reliability, but it does not promise 100\% reliable delivery. It is a
+best effort protocol.

 
 

-CTP is designed for relatively low traffic rates. Bandwidth-limited systems
-might benefit from a different protocol, which can, for example, pack
-multiple small frames into a single data-link packet.
+CTP is designed for relatively low traffic rates such that there is
+enough space in the channel to transmit and receive routing frames
+even when the network is forwarding collection data
+frames. Bandwidth-limited systems or high data rate applications might
+benefit from a different protocol, which can, for example, pack
+multiple small frames into a single data-link packet or employ rate
+control mechanisms.

 
 
 3. Collection and CTP
 
 
 3. Collection and CTP


@@ -163,7 +167,7 @@ distinction is important for duplicate suppression in the presence
 of routing loops. If a node suppresses origin packets, then if
 asked to forward the same packet twice due to a routing loop, it will
 drop the packet. However, if it suppresses packet instances, then it
 of routing loops. If a node suppresses origin packets, then if
 asked to forward the same packet twice due to a routing loop, it will
 drop the packet. However, if it suppresses packet instances, then it

-will route succesfully in the presence of transient loops unless the
+will route successfully in the presence of transient loops unless the

 THL happens to wrap around to a forwarded packet instance.
 
 A node MUST send CTP data frames as unicast messages with link-layer 
 THL happens to wrap around to a forwarded packet instance.
 
 A node MUST send CTP data frames as unicast messages with link-layer 


@@ -237,12 +241,12 @@ increasing randomized timer. The implementation resets the timer to a
 small value when one or more of the following conditions are met:
 
  1) The routing table is empty (this also sets the P bit)
 small value when one or more of the following conditions are met:
 
  1) The routing table is empty (this also sets the P bit)

- 2) The node's routing ETX increases by >= 1 trasmission
+ 2) The node's routing ETX increases by >= 1 transmission

  3) The node hears a packet with the P bit set
 
 The implementation augments the LEEP link estimates with data
 transmissions. This is a direct measure of ETX. Whenever the data path
  3) The node hears a packet with the P bit set
 
 The implementation augments the LEEP link estimates with data
 transmissions. This is a direct measure of ETX. Whenever the data path

-transmits a packet, it tells the link estimator the destimation and
+transmits a packet, it tells the link estimator the destination and

 whether it was successfully acknowledged. The estimator produces an
 ETX estimate every 5 such transmissions, where 0 successes has an ETX
 of 6.
 whether it was successfully acknowledged. The estimator produces an
 ETX estimate every 5 such transmissions, where 0 successes has an ETX
 of 6.


@@ -256,8 +260,9 @@ the rate at which CTP collects data estimates is proportional to
 the transmission rate, then it can quickly detect a broken link and
 switch to another candidate neighbor.
 
 the transmission rate, then it can quickly detect a broken link and
 switch to another candidate neighbor.
 

-The component ``tos/lib/net/le/LinkEstimatorP`` implements the
-link estimator. It couples LEEP-based and data-based estimates.
+The component ``tos/lib/net/4bitle/LinkEstimatorP`` implements the
+link estimator. It couples LEEP-based and data-based estimates as
+described in [4]_.

 
 6.2 Routing Engine
 ------------------------------------------------------------------------------
 
 6.2 Routing Engine
 ------------------------------------------------------------------------------


@@ -274,7 +279,7 @@ implements the routing engine.
 ------------------------------------------------------------------------------
 
 The component ``tos/lib/net/ctp/CtpForwardingEngineP`` implements the
 ------------------------------------------------------------------------------
 
 The component ``tos/lib/net/ctp/CtpForwardingEngineP`` implements the

-forwarding engine. It has five repsonsibilities:
+forwarding engine. It has five responsibilities:

 
  1) Transmitting packets to the next hop, retransmitting when necessary, and
     passing acknowledgment based information to the link estimator
 
  1) Transmitting packets to the next hop, retransmitting when necessary, and
     passing acknowledgment based information to the link estimator


@@ -360,3 +365,6 @@ along the path.
        in Wireless Sensor Networks." In Proceedings of the First USENIX
        Conference on Networked Systems Design and Implementation (NSDI), 2004.
 .. [3] TEP 119: Collection.
        in Wireless Sensor Networks." In Proceedings of the First USENIX
        Conference on Networked Systems Design and Implementation (NSDI), 2004.
 .. [3] TEP 119: Collection.

+.. [4] Rodrigo Fonseca, Omprakash Gnawali, Kyle Jamieson, and Philip Levis.
+       "Four Bit Wireless Link Estimation." In Proceedings of the Sixth Workshop
+       on Hot Topics in Networks (HotNets VI), November 2007.

diff --git a/doc/txt/tep124.txt b/doc/txt/tep124.txt
index 3a16cfe9128ce91d86f7327015a9af3ee91ba97e..24024230397c4ff8ec6e9cb949cbca9a4503d11a 100644 (file)
--- a/doc/txt/tep124.txt
+++ b/doc/txt/tep124.txt
@@ -35,9 +35,15 @@ 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
 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

-packet reception rate (PRR) estimates to packets. Other nodes hearing 
+packet reception rate (PRR) estimates to packets. Other nodes hearing

 these packets can combine the in-bound PRR values with their own
 these packets can combine the in-bound PRR values with their own

-in-bound values to compute bi-directional link quality.
+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
+bootstrapping values in the link quality table; data transmission
+statistics are later used to make these estimates more accurate.

 
 2. Definitions
 ============================================================================
 
 2. Definitions
 ============================================================================


@@ -103,7 +109,17 @@ link quality from the transmitter. LEEP MUST transmit Link Information
 entries describing the in-bound link qualities for a subset of its
 neighbors. The Link Information entry on the LEEP frame allows the
 receiver node to find the out-bound link quality to the transmitter
 entries describing the in-bound link qualities for a subset of its
 neighbors. The Link Information entry on the LEEP frame allows the
 receiver node to find the out-bound link quality to the transmitter

-node identified by the data link source address.
+node identified by the data link source address. Thus, LEEP is also a
+way for nodes to discover new nodes and links in the network.
+
+Link quality estimation is inherently imperfect - data transmission
+and link quality estimation might be done at different timescales. The
+PRR for LEEP frames (broadcast) and data frames (unicast) might be
+different. So LEEP is better used as a link quality bootstrapping
+mechanism. The link quality estimate can be made more accurate later
+using data transmission statistics.
+
+

 
 3.3 LEEP Frame
 --------------------------------------------------------------------
 
 3.3 LEEP Frame
 --------------------------------------------------------------------


@@ -179,6 +195,10 @@ the entries to be exchanged that could not fit in the previous LEEP
 frame. The LEEP frames are transmitted whenever the CTP [1]_ beacons,
 sent as a LEEP payload, are sent.
 
 frame. The LEEP frames are transmitted whenever the CTP [1]_ beacons,
 sent as a LEEP payload, are sent.
 

+Another reference implementation resides in
+``tinyos-2.x/tos/lib/net/le``. This implementation is described in
+detail in [2]_.
+

 5. Author's Address
 ============================================================================
 
 5. Author's Address
 ============================================================================
 


@@ -195,3 +215,6 @@ sent as a LEEP payload, are sent.
 ============================================================================
 
 .. [1] TEP 123: The Collection Tree Protocol.
 ============================================================================
 
 .. [1] TEP 123: The Collection Tree Protocol.

+.. [2] Rodrigo Fonseca, Omprakash Gnawali, Kyle Jamieson, and Philip Levis.
+       "Four Bit Wireless Link Estimation." In Proceedings of the Sixth Workshop
+       on Hot Topics in Networks (HotNets VI), November 2007.