[Tinyos-2-commits] CVS: tinyos-2.x/doc/txt tep124.txt,1.1,1.2

Thu Feb 8 19:03:59 PST 2007

Update of /cvsroot/tinyos/tinyos-2.x/doc/txt
In directory sc8-pr-cvs10.sourceforge.net:/tmp/cvs-serv14820

Modified Files:
	tep124.txt 
Log Message:
edit; incorporate comments from todays meeting

Index: tep124.txt
===================================================================
RCS file: /cvsroot/tinyos/tinyos-2.x/doc/txt/tep124.txt,v
retrieving revision 1.1
retrieving revision 1.2
diff -C2 -d -r1.1 -r1.2
*** tep124.txt	6 Feb 2007 15:32:29 -0000	1.1
--- tep124.txt	9 Feb 2007 03:03:57 -0000	1.2
***************
*** 1,7 ****
  ============================
! Link Quality Exchange Protocol (LQEP)
  ============================

! :TEP: 114 
  :Group: Network Protocol Working Group 
  :Type: Documentary
--- 1,7 ----
  ============================
! The Link Estimation Exchange Protocol (LEEP)
  ============================

! :TEP: 124 
  :Group: Network Protocol Working Group 
  :Type: Documentary
***************
*** 25,31 ****
  ============================================================================

! The memo documents the Link Quality Exchange Protocol (LQEP). Nodes
! use LQEP to exchange information about the quality of links to the
! neighbors.

  1. Introduction
--- 25,31 ----
  ============================================================================

! The memo documents the Link Estimation Exchange Protocol (LEEP). Nodes
! use LEEP to estimate and exchange information about the quality of
! links to the neighbors.

  1. Introduction
***************
*** 36,40 ****
  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 LQEP to determine
  the out-bound link qualities. Bi-directional link quality is computed
  using thus learned in-bound and out-bound link qualities.
--- 36,40 ----
  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.
***************
*** 48,53 ****
  Quality of the link between any two nodes describes the probability
  with which data link layer packets can be received without any
! error. The link between the nodes A and B may have different quality
! in A to B and B to A directions.

  2.2 In-bound Link Quality
--- 48,54 ----
  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.

  2.2 In-bound Link Quality
***************
*** 55,62 ****

  In a node pair (A,B), with B as the node of reference, in-bound link
! quality is defined as a value ranging from 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 transmitted packets
! or using link quality indicators (LQI,RSSI) provided by the radio on
  the node B, or some other methods.

--- 56,63 ----

  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 transmitted packets or using
! link quality indicators such as LQI and RSSI provided by the radio on
  the node B, or some other methods.

***************
*** 67,71 ****
  quality is defined as the quality of the link from B to A. B can
  determine the out-bound link quality if A advertises its in-bound link
! qualities. LQEP is the protocol that is used to exchange the in-bound
  link qualities.

--- 68,72 ----
  quality is defined as the quality of the link from B to A. B can
  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.

***************
*** 73,120 ****
  --------------------------------------------------------------------

! Link Information Entry is a tuple (n,q) where q is the in-bound link
! quality from the node n.

! 2. Link Quality Exchange Protocol (LQEP)
  ============================================================================

! 2.1 Assumptions
  --------------------------------------------------------------------

! Following are the assumptions made by LQEP:

! 2.1.1. The data link frame has a single-hop source field.
! 2.1.2. The data link layer provides a broadcast address.
! 2.1.3. The data link layer provides the length of the LQEP frame.

! 2.2 The Protocol
  --------------------------------------------------------------------

  To compute the bi-directional link quality, in-bound link quality must
! be exchanged among the neighbors. LQEP maintains a sequence number
! that is incremented by one for each outgoing LQEP frame. LQEP frame
! transmits this sequence number and Link Information entries describing
! the in-bound link qualities for a subset of its neighbors. When a node
! receives the LQEP frame and finds its node id in one of the Link
! Information entries, the node MUST use the second element of that
! tuple as its out-bound link quality to the neighbor identified by the
! data link source address. The LQEP sequence number SHOULD be used to
! estimate the in-bound link quality.

! 2.3 LQEP Frame
  --------------------------------------------------------------------

! A LQEP frame has a header, the payload, and a footer with the Link
  Information (LI) entries as shown in this diagram:

    -------------------------------------------------------------
!   |   LQEP   | Payload | LI Entry | LI Entry | ... | LI Entry |
    |  Header  |         |     1    |     2    |     |     n    |
    -------------------------------------------------------------

! 2.3.1 LQEP header

! The following diagram shows the LQEP header format:
                             1
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
--- 74,127 ----
  --------------------------------------------------------------------

! Link Information Entry created by node k is a tuple (n,q) where q is
! the in-bound link quality from node n to k.

! 3. The Link Estimation Exchange Protocol (LEEP)
  ============================================================================

! 3.1 Assumptions
  --------------------------------------------------------------------

! Following are the assumptions made by LEEP:

! 3.1.1. The data link frame has a single-hop source field.
! 3.1.2. The data link layer provides a broadcast address.
! 3.1.3. The data link layer provides the length of the LEEP frame.

! 3.2 The Protocol
  --------------------------------------------------------------------

  To compute the bi-directional link quality, in-bound link quality must
! be exchanged among the neighbors. LEEP maintains a sequence number
! that is incremented by one for each outgoing LEEP frame. The sequence
! number in the LEEP frame MUST be incremented by one even if the data
! link layer retransmits the LEEP frame. The LEEP sequence number MAY be
! used to count the number of missing packets to estimate the in-bound
! 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
! node identified by the data link source address.

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

! A LEEP frame has a header, the payload, and a footer with the Link
  Information (LI) entries as shown in this diagram:

    -------------------------------------------------------------
!   |   LEEP   | Payload | LI Entry | LI Entry | ... | LI Entry |
    |  Header  |         |     1    |     2    |     |     n    |
    -------------------------------------------------------------

+ The number of Link Information entries can be different in each
+ outgoing LEEP frame. The number of Link Information entries MUST not
+ increase the size of the LEEP frame beyond the maximum payload length
+ 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:
                             1
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
***************
*** 127,135 ****

  nentry - Number of Link Information entries in the footer
! seqno - LQEP sequence number.
! rsrvd - Reserved

! 2.3.2 Link Information Entry

  The following diagram shows the Link Information Entry format:
--- 134,142 ----

  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:
***************
*** 146,168 ****
  node id: the link layer address of the neighbor
  link quality: The in-bound link quality from the node identified by node id

! 7. Implementation
  ============================================================================

! The following files in ``tinyos-2.x/tos/lib/net/le`` provide a reference 
! implementation of LQEP described in this TEP.

!   * ``LinkEstimator.h`` and ``LinkEstimatorP``

! The reference implementation uses the LQEP sequence number to estimate
! the in-bound link quality. The implementation tries to append Link
! Information entry for all the neighbors in its neighbor table by
! sending the largest possible data link frame. If there is still not
! enough room to fit all the Link Information entries, it uses a
! round-robin policy to select the entries to be exchanged that could
! not fit in the previous LQEP frame.

! 8. Author's Address
  ============================================================================

--- 153,178 ----
  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
  ============================================================================

! The following files in ``tinyos-2.x/tos/lib/net/le`` provide a
! reference implementation of LEEP described in this TEP.

!   * ``LinkEstimator.h`` and ``LinkEstimatorP.nc``

! The reference implementation uses the LEEP sequence number to count
! the number of missing packets to estimate the in-bound link
! quality. The implementation tries to append Link Information entry for
! all the neighbors in its neighbor table by sending the largest
! possible data link frame. If there is still not enough room to fit all
! the Link Information entries, it uses a round-robin policy to select
! 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.

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

***************
*** 176,177 ****
--- 186,191 ----
  |

+ 6. Citations
+ ============================================================================
+ 
+ .. [1] TEP 123: The Collection Tree Protocol.