[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04

IETF MANET Working Group                                         V. Park
INTERNET-DRAFT                                                 S. Corson
draft-ietf-manet-tora-spec-04.txt             Flarion Technologies, Inc.
                                                            20 July 2001


         Temporally-Ordered Routing Algorithm (TORA) Version 1
                        Functional Specification

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   This document provides both a functional description and a detailed
   specification of the Temporally-Ordered Routing Algorithm (TORA)--a
   distributed routing protocol for multihop networks. A key concept in
   the protocol's design is an attempt to de-couple the generation of
   far-reaching control message propagation from the dynamics of the
   network topology. The basic, underlying algorithm is neither
   distance-vector nor link-state; it is a member of a class referred to
   as link-reversal algorithms. The protocol builds a loop-free,
   multipath routing structure that is used as the basis for forwarding
   traffic to a given destination. The protocol can simultaneously
   support both source-initiated, on-demand routing for some
   destinations and destination-initiated, proactive routing for other
   destinations.







Park, Corson             Expires 20 January 2002                [Page 1]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


1 Introduction

   The Temporally-Ordered Routing Algorithm (TORA) [1] is an adaptive
   routing protocol for multihop networks that possesses the following
   attributes:
     *  Distributed execution,
     *  Loop-free routing,
     *  Multipath routing,
     *  Reactive or proactive route establishment and maintenance, and
     *  Minimization of communication overhead via localization of
        algorithmic reaction to topological changes.
   TORA is distributed, in that routers need only maintain information
   about adjacent routers (i.e., one-hop knowledge). Like a distance-
   vector routing approach, TORA maintains state on a per-destination
   basis. However, TORA does not continuously execute a shortest-path
   computation and thus the metric used to establish the routing
   structure does not represent a distance. The destination-oriented
   nature of the routing structure in TORA supports a mix of reactive
   and proactive routing on a per-destination basis. During reactive
   operation, sources initiate the establishment of routes to a given
   destination on-demand. This mode of operation may be advantageous in
   dynamic networks with relatively sparse traffic patterns, since it
   may not be necessary (nor desirable) to maintain routes between every
   source/destination pair at all times. At the same time, selected
   destinations can initiate proactive operation, resembling traditional
   table-driven routing approaches. This allows routes to be proactively
   maintained to destinations for which routing is consistently or
   frequently required (e.g., servers or gateways to hardwired
   infrastructure).

   TORA is designed to minimize the communication overhead associated
   with adapting to network topological changes. The scope of TORA's
   control messaging is typically localized to a very small set of nodes
   near a topological change. A secondary mechanism, which is
   independent of network topology dynamics, is used as a means of route
   optimization and soft-state route verification. The design and
   flexability of TORA allow its operation to be biased towards high
   reactivity (i.e., low time complexity) and bandwidth conservation
   (i.e., low communication complexity) rather than routing
   optimality--making it potentially well-suited for use in dynamic
   wireless networks.

2 Terminology

   MANET router or router:
      A device--identified by a "unique Router ID" (RID)--that executes
      a MANET routing protocol and, under the direction of which,
      forwards IP packets. It may have multiple interfaces, each



Park, Corson             Expires 20 January 2002                [Page 2]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


      identified by an IP address. Associated with each interface is a
      physical layer communication device. These devices may employ
      wireless or hardwired communications, and a router may
      simultaneously employ devices of differing technologies. For
      example, a MANET router may have four interfaces with differing
      communications technologies: two hardwired (Ethernet and FDDI) and
      two wireless (spread spectrum and impulse radio).

   adjacency:
      The name given to an "interface on a neighboring router".

   medium:
      A communication channel such as free space, cable or fiber through
      which connections are established.

   communications technology:
      The means employed by two devices to transfer information between
      them.

   connection:
      A physical-layer connection--which may be through a wired or
      wireless medium--between a device attached to an interface of one
      MANET router and a device utilizing the same communications
      technology attached to an interface on another MANET router. From
      the perspective of a given router, a connection is a (interface,
      adjacency) pair.

   link:
      A "logical connection" consisting of the logical *union* of one or
      more connections between two MANET routers. Thus, a link may
      consist of a heterogeneous combination of connections through
      differing media using different communications technologies.

   neighbor:
      From the perspective of a given MANET router, a "neighbor" is any
      other router to which it is connected by a link.

   topology:
      A network can be viewed abstractly as a "graph" whose "topology"
      at any point in time is defined by set of "points" connected by
      "edges." This term comes from the branch of mathematics bearing
      the same name that is concerned with those properties of geometric
      configurations (such as point sets) which are unaltered by elastic
      deformations (such as stretching) that are homeomorphisms.

   physical-layer topology:
      A topology consisting of connections (the edges) through the
      *same* communications medium between devices (the points)



Park, Corson             Expires 20 January 2002                [Page 3]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


      communicating using the *same* communications technology.

   network-layer topology:
      A topology consisting of links (the edges) between MANET routers
      (the points) which is used as the basis for MANET routing. Since
      "links" are the logical union of physical-layer "connections," it
      follows that the "network-layer topology" is the logical union of
      the various "physical-layer topologies."

   IP routing fabric:
      The heterogeneous mixture of communications media and technologies
      through which IP packets are forwarded whose topology is defined
      by the network-layer topology.

3 Protocol Functional Description

   This section is intended to provide an overview of the protocol and
   insight into its operation. The protocol specification provided in a
   subsequent section is intended to serve as the basis for protocol
   implementations. Thus, in the case of any discrepancies between the
   description in this section and the subsequent specification section,
   the specification section should be considered more athoritative.

   TORA has been designed to work on top of lower layer mechanisms or
   protocols that provide the following basic services between
   neighboring routers:
     *  Link status sensing and neighbor discovery
     *  Reliable, in-order control packet delivery
     *  Link and network layer address resolution and mapping
     *  Security authentication
   Events such as the reception of control messages and changes in
   connectivity with neighboring routers trigger TORA's algorithmic
   reactions.

   A logically separate version of TORA is run for each "destination" to
   which routing is required. The following discussion focuses on a
   single version of TORA running for a given destination. The term
   destination is used herein to refer to a traditional IP routing
   destination, which is identified by an IP address and mask (or
   prefix). Thus, the route to a destination may correspond to the
   individual address of an interface on a specific machine (i.e., a
   host route) or an aggregation of addresses (i.e., a network route).

   TORA assigns directions to the links between routers to form a
   routing structure that is used to forward datagrams to the
   destination. A router assigns a direction ("upstream" or
   "downstream") to the link with a neighboring router based on the
   relative values of a metric associated with each router. The metric



Park, Corson             Expires 20 January 2002                [Page 4]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   maintained by a router can conceptually be thought of as the router's
   "height" (i.e., links are directed from the higher router to the
   lower router). The significance of the heights and the link
   directional assignments is that a router may only forward datagrams
   downstream. Links from a router to any neighboring routers with an
   unknown or undefined height are considered undirected and cannot be
   used for forwarding. Collectively, the heights of the routers and the
   link directional assignments form a loop-free, multipath routing
   structure in which all directed paths lead downstream to the
   destination, see Figure 1. Note that in this example, C is closer to
   the destination than B in terms of number of hops, but the height
   metric of C is greater than that of B.


    .-----.     .-----.     .-----.
    |  A  |---->|  B  |<----|  C  |    Relative height of the routers
    `-----'     `-----'     `-----'    ------------------------------
       ^           |           |
       |           |           |            H(C) > H(B) > H(E) > H(DEST)
       |           |           |
       |           v           v     H(D) > H(A) > H(B) > H(E) > H(DEST)
    .-----.     .-----.     .-----.
    |  D  |---->|  E  |---->| DEST|
    `-----'     `-----'     `-----'

       Figure 1:  Conceptual representation of the directed acyclic
         graph defined by the relative height of network routers.

   TORA can be separated into four basic functions: creating routes,
   maintaining routes, erasing routes, and optimizing routes. Creating
   routes corresponds to the selection of heights to form a directed
   sequence of links leading to the destination in a previously
   undirected network or portion of the network. Maintaining routes
   refers to the adapting the routing structure in response to network
   topological changes. For example, following the loss of some router's
   last downstream link, some directed paths may temporarily no longer
   lead to the destination. This event triggers a sequence of directed
   link reversals (caused by the re-selection of router heights), which
   re-orients the routing structure such that all directed paths again
   lead to the destination. In cases where the network becomes
   partitioned, links in the portion of the network that has become
   partitioned from the destination must be marked as undirected to
   erase invalid routes. During this erasing routes process, routers set
   their heights to null and their adjacent links become undirected.
   Finally, TORA includes a secondary mechanism for optimizing routes,
   in which routers re-select their heights in order to improve the
   routing structure. TORA accomplishes these four functions through the
   use of four distinct control packets: query (QRY), update (UPD),



Park, Corson             Expires 20 January 2002                [Page 5]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   clear (CLR), and optimization (OPT).

3.1 Creating Routes

   Creating routes can be initiated on-demand by a source or proactively
   by a destination. In either case, routers select heights with respect
   to the given destination and assign directions to the links between
   neighboring routers.

   In the on-demand mode, creating routes is accomplished via a query-
   reply mechanism using QRY and UPD packets. A source initiates the
   process by sending a QRY packet to its neighbors that identifies the
   destination for which a route is requested. The QRY packet is
   propagated out from the source (i.e., processed and forwarded by
   neighboring routers) until it is received by one or more routers that
   have a trusted route to the destination. As the QRY packet is
   forwarded, routers set a route-requested flag and discard any
   subsequent QRY packets received for the same destination. The route-
   requested flag supresses redundant route requests and reduces the
   need for subsequent route requests when a destination is temporarily
   unreachable. Routers that have a trusted route to the destination
   repsond to the QRY packet by sending an UPD packet to their neighbors
   that identifies the relevant destination and the height of the router
   sending the UPD packet. Routers also maintain the time at which an
   UPD packet was last sent to its neighbors and the time at which links
   to neighboring routers became active, to reduce redundant replies to
   a given route request. When a router with the route-requested flag
   set receives an UPD packet, it sets its height and sends an UPD
   packet to its neighbors that identifies the relevant destination and
   the new height of the router sending the UPD packet. Thus, routers in
   the network select heights for the requested desination, learn of
   their neighbors heights for the destination and assign link
   directions based on those heights. To ensure that a route request
   continues to propagate when the destination was initially
   unreachable, routers with the route-requested flag set must resend a
   QRY packet upon activation of a new link (i.e., discovery of a new
   neighbor).

   In the proactive mode, the destination initiates the creating routes
   process by sending an OPT packet that is processed and forwarded by
   neighboring routers. The OPT packet identifies the destination, the
   mode of operation for the destination and the height of the router
   sending the OPT packet. The OPT packet also contains a sequence
   number used to uniquely identify the packet and ensure that each
   router processes and forwards a given OPT packet from a destination
   at most once. As the OPT packet is forwarded, routers set their mode
   of operation correspondingly, reselect their heights, and send an OPT
   packet to their neighbors that identifies the relevant destination



Park, Corson             Expires 20 January 2002                [Page 6]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   and the new height of the router sending the UPD packet.

3.2 Maintaining Routes

   Maintaining routes is only performed for nodes that have a height
   other than NULL. Furthermore, any neighbor's height that is NULL is
   not used for the computations. A node i is said to have no downstream
   links if HEIGHT < HT_NEIGH[k] for all non-NULL neighbors k. This will
   result in one of five possible reactions depending on the state of
   the node and the preceding event. Each node (other than the
   destination) that has no downstream links modifies its height, HEIGHT
   = (tau[i], oid[i], r[i], delta[i], i), as follows:

      Case 1 (Generate):

         Node i has no downstream links (due to a link failure).

         (tau[i], oid[i], r[i])=(t, i, 0), where t is the time of the
         failure.

         (delta[i],i)=(0, i)

         In essence, node i defines a new reference level. The above
         assumes node i has at least one upstream neighbor. If node i
         has no upstream neighbors it simply sets its height to NULL.

      Case 2 (Propagate):

         Node i has no downstream links (due to a link reversal
         following reception of an UPD packet) and the ordered sets
         (tau[k], oid[k], r[k]) are not equal for all neighbors k.

         (tau[i], oid[i], r[i])=max{(t[k], oid[k], r[k]) of all
         neighbors k}

         (delta[i],i)=(delta[m]-1, i), where m is the lowest neighbor
         with the maximum reference level defined above.

         In essence, node i propagates the reference level of its
         highest neighbor and selects a height that is lower than all
         neighbors with that reference level.

      Case 3 (Reflect):

         Node i has no downstream links (due to a link reversal
         following reception of an UPD packet) and the ordered sets
         (tau[k], oid[k], r[k]) are equal with r[k] = 0 for all
         neighbors k.



Park, Corson             Expires 20 January 2002                [Page 7]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


         (tau[i], oid[i], r[i])=(tau[k], oid[k], 1)

         (delta[i],i)=(0, i)

         In essence, the same level (which has not been "reflected") has
         propagated to node i from all of its neighbors. Node i
         "reflects" back a higher sub-level by setting the bit r.

      Case 4 (Detect):

         Node i has no downstream links (due to a link reversal
         following reception of an UPD packet), the ordered sets
         (tau[k], oid[k], r[k]) are equal with r[k] = 1 for all
         neighbors k, and oid[k] = i (i.e., node i defined the level).

         (tau[i], oid[i], r[i])=(-, -, -)

         (delta[i],i)=(-, i)

         In essence, the last reference level defined by node i has been
         reflected and propagated back as a higher sub-level from all of
         its neighbors. This corresponds to detection of a partition.
         Node i must initiate the process of erasing invalid routes as
         discussed in the next section.

      Case 5 (Generate):

         Node i has no downstream links (due to a link reversal
         following reception of an UPD packet), the ordered sets
         (tau[k], oid[k], r[k]) are equal with r[k] = 1 for all
         neighbors k, and oid[k] != i (i.e., node i did not define the
         level).

         (tau[i], oid[i], r[i])=(t, i, 0), where t is the time of the
         failure

         (delta[i],i)=(0, i)

         In essence, node i experienced a link failure (which did not
         require reaction) between the time it propagated a reference
         level and the reflected higher sub-level returned from all
         neighbors. This is not necessarily an indication of a
         partition. Node i defines a new reference level.

   Following determination of its new height in cases 1, 2, 3, and 5,
   node i updates all the entries in its link-status table; and
   broadcasts an UPD packet to all neighbors k. The UPD packet consists
   of the destination-ID, j, and the new height of the node i that is



Park, Corson             Expires 20 January 2002                [Page 8]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   broadcasting the packet, HEIGHT. When a node i receives an UPD packet
   from a neighbor k, node i reacts as described in the creating routes
   section and in accordance with the cases outlined above. In the event
   of the failure a link (i, k) that is not its last downstream link,
   node i simply removes the entries HT_NEIGH[k] and LNK_STAT[k] in its
   height and link-status tables.

3.3 Erasing Routes

   Following detection of a partition (case 4), node i sets its height
   and the height entry for each neighbor k to NULL (unless the
   destination j is a neighbor, in which case the corresponding height
   entry is set to ZERO), updates all the entries in its link-status
   table, and broadcast a CLR packet. The CLR packet consists of the
   destination-ID, j, and the reflected reference level of node i,
   (tau[i], oid[i], 1). In actuality the value r[i] = 1 need not be
   included since it is always 1 for a reflected reference level. When a
   node i receives a CLR packet from a neighbor k it reacts as follows:

      a) If the reference level in the CLR packet matches the reference
      level of node i; it sets its height and the height entry for each
      neighbor k to NULL (unless the destination j is a neighbor, in
      which case the corresponding height entry is set to ZERO), updates
      all the entries in its link-status table and broadcasts a CLR
      packet.

      b) If the reference level in the CLR packet does not match the
      reference level of node i; it sets the height entry for each
      neighbor k (with the same reference level as the CLR packet) to
      NULL and updates the corresponding link-status table entries.
      Thus, the height of each node in the portion of the network that
      was partitioned is set to NULL and all invalid routes are erased.
      If (b) causes node i to lose its last downstream link, it reacts
      as in case 1 of maintaining routes.

3.4 Optimizing Routes

   TBD.

4 Protocol Specification

   The subsequent specification is intended to be of sufficient detail
   to serve as a template for implementations.

4.1 Configuration

   A router is configured with a router ID (RID), which must be unique
   among the set of routers collectively running TORA within a routing



Park, Corson             Expires 20 January 2002                [Page 9]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   domain. This value may correspond to one of the router's IP
   addresses.

   For each interface "i" of a router, the following parameters must be
   configured.

   IP_ADDR[i]     IP address of interface.
   ADDR_MASK[i]   Address mask of interface.
   PRO_MODE[i]    Indicates reactive/proactive mode of operation.
   OPT_MODE[i]    Indicates optimization mode of operation.
   OPT_PERIOD[i]  Period for optimization mechanism.

   For each interface, a network route corresponding to the address and
   mask of the interface may be added to the routing table.
   Additionally, TORA may respond to requests (i.e., QRY packets) for
   routes to destination addresses that match the set of addresses
   identified by the interface configurations. PRO_MODE[i] (0=OFF, 1=ON)
   indicates if routes to the destination identified by the
   corresponding interface address and mask should be created
   proactively. OPT_MODE[i] (00=OFF, 01=PARTIAL, 10=FULL, 11=reserved
   for future use) indicates the type (if any) of optimizations that
   should be used for the destination identified by the corresponding
   interface address and mask, while the OPT_PERIOD[i] sets the
   frequency at which the optimizations will occur.

4.2 State Variables

   A router maintains the state of the configuration parameters outlined
   above. In addition, for each interface a router maintains a sequence
   number that is incremented upon changes to the interface mode of
   operation.

   MODE_SEQ[i]  Sequence number associated with mode of interface "i".

   For each destination "j", a router maintains the following state
   variables.

   HEIGHT[j]      This router's height metric for routing to "j".
   MODE_SEQ[j]    Sequence number of most recent mode for "j".
   PRO_MODE[j]    Indicates reactive/proactive mode of operation for "j".
   OPT_MODE[j]    Indicates optimization mode of operation for "j".
   OPT_PERIOD[j]  Indicates optimization period for "j".
   RT_REQ[j]      Indicates whether a route request to "j" is pending.
   TIME_UPD[j]    Time last UPD packet regarding "j" sent by this router.

   For each destination "j", a router maintains a separate instance of
   the following state variables for each neighbor "k".




Park, Corson             Expires 20 January 2002               [Page 10]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   HT_NEIGH[j][k]  The height metric of neighbor "k."
   LNK_STAT[j][k]  The assigned status of the link to neighbor "k."
   TIME_ACT[j][k]  Time the link to neighbor "k" became active.

4.3 Auxiliary Variables

   For each destination "j" to which routing is required, a router may
   maintain the following auxiliary variables. Although each of the
   variables can be computed based on the entries in the LNK_STAT table,
   maintaining the values continuously may facilitate implementation of
   the protocol. Whether these variables are maintained continuously or
   computed when needed is implementation specific.

   NUM_ACTIVE[j]  Number of neighbors (i.e., active links).
   NUM_DOWN[j]    Number of links marked DN in the LNK_STAT table.
   NUM_UP[j]      Number of links marked UP in the LNK_STAT table.

4.4 Height Data Structure

   Each HEIGHT[j] and HT_NEIGH[j][k] entry requires a data structure
   that comprises five components. The first three components of the
   Height data structure represent the reference level of the height
   entry, while the last two components represent an offset with respect
   to the reference level. The five components of the Height data
   structure are as follows.

   HEIGHT.tau   Time the reference level was created.
   HEIGHT.oid   Unique id of the router that created the reference level.
   HEIGHT.r     Flag indicating if it is a reflected reference level.
   HEIGHT.delta Value used in propagation of a reference level.
   HEIGHT.id    Unique id of the router to which the height metric refers.

   To simplify notation in this specification, a height may be written
   as an ordered quintuple--e.g., HEIGHT[j]=(tau,oid,r,delta,id). The
   following two predefined values for a height are used throughout the
   specification of the protocol.

   NULL=(-,-,-,-,id)  An unknown or undefined height. Conceptually,
                      this can be thought of as an infinite height.

   ZERO=(0,0,0,0,id)  The assumed height of a given destination. Note
                      that here "id" is the unique id of the given
                      destination.

4.5 Determination of Link Status

   Each entry in the LNK_STAT table is maintained in accordance with the
   following rule.



Park, Corson             Expires 20 January 2002               [Page 11]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   if        HT_NEIGH[k]==NULL    then   LNK_STAT[k]=UN;
   else if   HEIGHT==NULL         then   LNK_STAT[k]=DN;
   else if   HT_NEIGH[k]<HEIGHT   then   LNK_STAT[k]=DN;
   else if   HT_NEIGH[k]>HEIGHT   then   LNK_STAT[k]=UP;

4.6 TORA Packet Formats

4.6.1 Query (QRY) Packet Format

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Version #   |      Type     |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Destination IP Address                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version #
      The TORA version number. This specification documents version 1.

   Type
      The TORA packet type. For QRY packet this field is set to 1.

   Reserved
      Field reserved for future use.

   Destination IP Address
      The IP address for which a route is being requested.

4.6.2 Update (UPD) Packet Format

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Version #   |      Type     |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Destination IP Address                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Destination IP Address Mask                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Mode Sequence #                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Mode     |               Optimization Period             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.tau                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.oid                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



Park, Corson             Expires 20 January 2002               [Page 12]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


      |      H.r      |                     H.delta                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.id                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version #
      The TORA version number. This specification documents version 1.

   Type
      The TORA packet type. For UPD packet this field is set to 2.

   Reserved
      Field reserved for future use.

   Destination IP Address
      The IP address for which a route is being requested.

   Destination IP Address Mask
      The network mask associated with the destination IP address.

   Mode Sequence #
      Sequence number associated with the subsequent mode and
      optimization period fields. Used for propagation of most recent
      mode state and to ensure each router processes mode information at
      most once.

   Mode
      The mode of operation associated with the destination IP address
      and mask. This field is used to indicate reactive/proactive
      routing and also the type (if any) of optimizations used for the
      destination.

   Optimization Period
      The period for optimization packets originated by the destination.

   H.tau
      The H.tau value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.oid
      The H.oid value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.r
      The H.r value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.delta



Park, Corson             Expires 20 January 2002               [Page 13]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


      The H.delta value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.id
      The H.id value, associated with the destination IP address and
      mask, of the router sending the UPD (i.e., unique router ID).

4.6.3 Clear (CLR) Packet Format

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Version #   |      Type     |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Destination IP Address                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Destination IP Address Mask                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.tau                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.oid                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.id                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version #
      The TORA version number. This specification documents version 1.

   Type
      The TORA packet type. For CLR packet this field is set to 3.

   Reserved
      Field reserved for future use.

   Destination IP Address
      The IP address for which a route is being requested.

   Destination IP Address Mask
      The network mask associated with the destination IP address.

   H.tau
      The H.tau value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.oid
      The H.oid value, associated with the destination IP address and
      mask, of the router sending the UPD.




Park, Corson             Expires 20 January 2002               [Page 14]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   H.id
      The H.id value, associated with the destination IP address and
      mask, of the router sending the UPD (i.e., unique router ID).

4.6.4 Optimization (OPT) Packet Format

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Version #   |      Type     |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Destination IP Address                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Destination IP Address Mask                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Mode Sequence #                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Mode     |               Optimization Period             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.tau                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.oid                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      H.r      |                     H.delta                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             H.id                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version #
      The TORA version number. This specification documents version 1.

   Type
      The TORA packet type. For OPT packet this field is set to 4.

   Reserved
      Field reserved for future use.

   Destination IP Address
      The IP address for which a route is being requested.

   Destination IP Address Mask
      The network mask associated with the destination IP address.

   Mode Sequence #
      Sequence number associated with the subsequent mode and
      optimization period fields. Used for propagation of most recent
      mode state and to ensure each router processes mode information at
      most once.



Park, Corson             Expires 20 January 2002               [Page 15]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   Mode
      The mode of operation associated with the destination IP address
      and mask. This field is used to indicate reactive/proactive
      routing and also the type (if any) of optimizations used for the
      destination.

   Optimization Period
      The period for optimization packets originated by the destination.

   H.tau
      The H.tau value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.oid
      The H.oid value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.r
      The H.r value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.delta
      The H.delta value, associated with the destination IP address and
      mask, of the router sending the UPD.

   H.id
      The H.id value, associated with the destination IP address and
      mask, of the router sending the UPD (i.e., unique router ID).

4.7 Event Processing

4.7.1 Initialization

   TBD

4.7.2 Connection Status Change

   The TORA process receives notification of link status changes from
   lower layer mechanisms or protocols. It is anticipated that the TORA
   process will have access to all the information about the
   connections. Thus, upon notification, TORA will have sufficient
   information to determine if any new links have been established or
   any existing links have been severed. If either is the case, then
   TORA must proceed as outlined in appropriate subsequent section
   (4.7.3 or 4.7.4). In addition, since a link is potientially composed
   of multiple connections, it is also possible for a connection that
   was used in the routing table to be severed without resulting in the
   corresponding link being severed. In this case TORA must modify the



Park, Corson             Expires 20 January 2002               [Page 16]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   appropriate routing table entries.

4.7.3 Link with a New Neighbor "k" Established

   For each destination "j":

   Set TIME_ACT[j][k] to the current time and increment NUM_ACTIVE[j].

   If the neighbor "k" is the destination "j", then set
   HT_NEIGH[j][k]=ZERO, LNK_STAT[j][k]=DN and increment NUM_DOWN[j],
   else set HT_NEIGH[j][k]=NULL and LNK_STAT[j][k]=UN.

   If the RT_REQ[j] flag is set && neighbor "k" is the destination "j"
   then I) else II).

      I) Set HEIGHT[j]=HT_NEIGH[j][k].  Increment HEIGHT[j].delta.  Set
      HEIGHT[j].id to the unique id of this node.  Update LNK_STAT[j][n]
      for all n.  Unset the RT_REQ[j] flag.  Set TIME_UPD[j] to the
      current time.  Create an UPD packet and place it in the queue to
      be sent to all neighbors.  Event Processing Complete.

      II) If PRO_MODE==1 and HEIGHT[j]!=NULL then A) else B).

         A) Set TIME_UPD[j] to the current time.  Create an UPD packet
         and place it in the queue to be sent to all neighbors.  If the
         RT_REQ[j] flag is set, create a QRY packet and place it in the
         queue to be sent to all neighbors.  Event Processing Complete.

         B) If the RT_REQ[j] flag is set, create a QRY packet and place
         it in the queue to be sent to all neighbors.  Event Processing
         Complete.

4.7.4  Link with Prior Neighbor "k" Severed

   For each destination "j":

   Decrement NUM_ACTIVE[j].  If LNK_STAT[j][k]==DN, decrement
   NUM_DOWN[j].  If LNK_STAT[j][k]==UP, decrement NUM_UP[j].

   If NUM_DOWN[j]==0 then I) else II).

      I) If NUM_ACTIVE[j]==0 then A) else B).

         A) Set HEIGHT[j]=NULL.  Unset the RT_REQ[j] flag.  Event
         Processing Complete.

         B) If NUM_UP==0 then 1) else 2).




Park, Corson             Expires 20 January 2002               [Page 17]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


            1) If HEIGHT[j]==NULL then a) else b).

               a) Event Processing Complete.

               b) Set HEIGHT[j]=NULL.  Set TIME_UPD[j] to the current
               time.  Create an UPD packet and place it in the queue to
               be sent to all neighbors.  Event Processing Complete.

            2) Set HEIGHT[j].tau to the current time.  Set HEIGHT[j].oid
            to the unique id of this node.  Set HEIGHT[j].r=0.  Set
            HEIGHT[j].delta=0.  Set HEIGHT[j].id to the unique id of
            this node.  Update LNK_STAT[j][n] for all n.  Unset the
            RT_REQ[j] flag.  Set TIME_UPD[j] to the current time.
            Create an UPD packet and place it in the queue to be sent to
            all neighbors.  Event Processing Complete.

      II) Event Processing Complete.

4.7.5 QRY Packet Regarding Destination "j" Received from Neighbor "k"

   If the RT_REQ[j] flag is set then I) else II).

      I) Event Processing Complete.

      II) If HEIGHT[j].r==0 then A) else B).

         A) If TIME_ACT[j][k]>TIME_UPD[j] then 1) else 2).

            1) Set TIME_UPD[j] to the current time.  Create an UPD
            packet and place it in the queue to be sent to all
            neighbors.  Event Processing Complete.

            2) Event Processing Complete.

         B) If HT_NEIGH[j][n].r==0 for any n then 1) else 2).

            1) Find m such that HT_NEIGH[j][m] is the minimum of all
            height entries with HT_NEIGH[j][n].r==0.  Set
            HEIGHT[j]=HT_NEIGH[j][m].  Increment HEIGHT.delta.  Set
            HEIGHT[j].id to the unique id of this node.  Update
            LNK_STAT[j][n] for all n.  Set TIME_UPD[j] to the current
            time.  Create an UPD packet and place it in the queue to be
            sent to all neighbors.  Event Processing Complete.

            2) Set the RT_REQ[j] flag. If NUM_ACTIVE[j]>1 then a) else
            b).

               a) Create a QRY packet and place it in the queue to be



Park, Corson             Expires 20 January 2002               [Page 18]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


               sent to all neighbors.  Event Processing Complete.

               b) Event Processing Complete.

4.7.6 UPD Packet Regarding Destination "j" Received from Neighbor "k"

   If MODE_SEQ field of received packet is greater than MODE_SEQ[j],
   update entries PRO_MODE[j], OPT_MODE[j], and MODE_SEQ[j].

   Update the entries HT_NEIGH[j][k], and LNK_STAT[j][k].  If the
   RT_REQ[j] flag is set and HT_NEIGH[j][k].r==0 then I) else II).

      I) Set HEIGHT[j]=HT_NEIGH[j][k].  Increment HEIGHT.delta.  Set
      HEIGHT[j].id to the unique id of this node.  Update LNK_STAT[j][n]
      for all n.  Unset the RT_REQ[j] flag.  Set TIME_UPD[j] to the
      current time.  Create an UPD packet and place it in the queue to
      be sent to all neighbors.  Event Processing Complete.

      II) If NUM_DOWN[j]==0 then A) else B).

         A) If NUM_UP[j]==0 then 1) else 2).

            1) If HEIGHT[j]==NULL then a) else b).

               a) Event Processing Complete.

               b) Set HEIGHT[j]=NULL.  Set TIME_UPD[j] to the current
               time.  Create an UPD packet and place it in the queue to
               be sent to all neighbors.  Event Processing Complete.

            2) If all HT_NEIGH[j][n], for all n such that HT_NEIGH[j][n]
            is non-NULL, have the same reference level then a) else b).

               a) If HT_NEIGH[j][n].r==0, for any n such that
               HT_NEIGH[j][n] is non-NULL, then i) else ii).

                  i) Set HEIGHT[j]=HT_NEIGH[j][n], where n is such that
                  HT_NEIGH[j][n] is non-NULL.  Set HEIGHT[j].r=1.  Set
                  HEIGHT[j].delta=0.  Set HEIGHT[j].id to the unique id
                  of this node.  Update LNK_STAT[j][n] for all n.  Set
                  TIME_UPD[j] to the current time.  Create an UPD packet
                  and place it in the queue to be sent to all neighbors.
                  Event Processing Complete.

                  ii) If HT_NEIGH[j][n].oid==id, where n is such that
                  HT_NEIGH[j][n] is non-NULL and id is the unique id of
                  this node, then x) else y).




Park, Corson             Expires 20 January 2002               [Page 19]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


                     x) Save the current values of HEIGHT[j].tau and
                     HEIGHT[j].oid in temporary variables.  Set
                     HEIGHT[j]=NULL.  Set NUM_DOWN[j]=0.  Set
                     NUM_UP[j]=0.  For every active link n, if the
                     neighbor connected via link n is the destination j,
                     set HT_NEIGH[j][n]=ZERO and LNK_STAT[j][n]=DN else
                     set HT_NEIGH[j][n]=NULL and LNK_STAT[j][n]=UN.
                     Create a CLR packet, with the previously saved
                     values of tau and oid, and place it in the queue to
                     be sent to all neighbors.  Event Processing
                     Complete.

                     y) Set HEIGHT[j].tau to the current time.  Set
                     HEIGHT[j].oid to the unique id of this node.  Set
                     HEIGHT[j].r=0.  Set HEIGHT[j].delta=0.  Set
                     HEIGHT[j].id to the unique id of this node.  Update
                     LNK_STAT[j][n] for all n.  Unset the RT_REQ[j]
                     flag.  Set TIME_UPD[j] to the current time.  Create
                     an UPD packet and place it in the queue to be sent
                     to all neighbors.  Event Processing Complete.

               b) Find n such that HT_NEIGH[j][n] is the maximum of all
               non-NULL height entries.  Find m such that HT_NEIGH[j][m]
               is the minimum of the non-NULL height entries with the
               same reference level as HT_NEIGH[j][n].  Set
               HEIGHT[j]=HT_NEIGH[j][m].  Decrement HEIGHT.delta.  Set
               HEIGHT[j].id to the unique id of this node.  Update
               LNK_STAT[j][n] for all n.  Set TIME_UPD[j] to the current
               time.  Create an UPD packet and place it in the queue to
               be sent to all neighbors.  Event Processing Complete.

         B) IF PRO_MODE changed from OFF to ON as a result of this UPD
         packet reception and HEIGHT[j]==NULL then 1) else 2)

            1) Find m such that HT_NEIGH[j][m] is the minimum of all
            non-NULL height entries.  Set HEIGHT[j]=HT_NEIGH[j][m].
            Increment HEIGHT[j].delta.  Set HEIGHT[j].id to the unique
            id of this node.  Update LNK_STAT[j][n] for all n.  Set
            TIME_UPD[j] to the current time.  Create an UPD packet and
            place it in the queue to be sent to all neighbors.  Event
            Processing Complete.

            2) Event Processing Complete.

4.7.7 CLR Packet Regarding Destination "j" Received from Neighbor "k"

   If HEIGHT[j].tau and HEIGHT[j].oid match the values of tau and oid
   from the CLR packet and HEIGHT[j].r==1 then I) else II).



Park, Corson             Expires 20 January 2002               [Page 20]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


      I) Save the current values of HEIGHT[j].tau and HEIGHT[j].oid in
      temporary variables.  Set Height[j]=NULL.  Set NUM_DOWN[j]=0.  Set
      NUM_UP[j]=0.  For every active link n, if the neighbor connected
      via link n is the destination j, set HT_NEIGH[j][n]=ZERO and
      LNK_STAT[j][n]=DN else set HT_NEIGH[j][n]=NULL and
      LNK_STAT[j][n]=UN.  If NUM_ACTIVE[j]>1 then A) else B).

         A) Create a CLR packet, with the previously saved values of tau
         and oid, and place it in the queue to be sent to all neighbors.
         Event Processing Complete.

         B) Event Processing Complete.

      II) Set HT_NEIGH[j][k]=NULL and LNK_STAT[j][k]=UN.  For all n such
      that HT_NEIGH[j][n].tau and HT_NEIGH[j][n].oid match the values of
      tau and oid from the CLR packet and HT_NEIGH[j][n].r==1, set
      HT_NEIGH[j][n]=NULL and LNK_STAT[j][n]=UN.  If NUM_DOWN[j]==0 then
      A) else B).

         A) If NUM_UP==0 then 1) else 2).

            1) If HEIGHT[j]==NULL then a) else b).

               a) Event Processing Complete.

               b) Set HEIGHT[j]=NULL.  Set TIME_UPD[j] to the current
               time.  Create an UPD packet and place it in the queue to
               be sent to all neighbors.  Event Processing Complete.

            2) Set HEIGHT[j].tau to the current time.  Set HEIGHT[j].oid
            to the unique id of this node.  Set HEIGHT[j].r=0.  Set
            HEIGHT[j].delta=0.  Set HEIGHT[j].id to the unique id of
            this node.  Update LNK_STAT[j][n] for all n.  Unset the
            RT_REQ[j] flag.  Set TIME_UPD[j] to the current time.
            Create an UPD packet and place it in the queue to be sent to
            all neighbors.  Event Processing Complete.

         B) Event Processing Complete.

4.7.8 OPT Packet Regarding Destination "j" Received from Neighbor "k"

   If MODE_SEQ field of received packet is greater than MODE_SEQ[j] then
   I) else II).

      I) Update entries PRO_MODE[j], OPT_MODE[j], and MODE_SEQ[j].  If
      PRO_MODE[j] changed as a result of this OPT packet reception ||
      (OPT_MODE[j]==PARTIAL && HEIGHT[j]!=NULL) || OPT_MODE[j]==FULL
      then A) else B).



Park, Corson             Expires 20 January 2002               [Page 21]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


         A) Set HEIGHT[j]=ZERO.  Set HEIGHT[j].delta to the value of the
         DELTA field in the received OPT packet + 1.  Set HEIGHT[j].id
         to the unique id of this node.  Update LNK_STAT[j][n] for all
         n.  Unset the RT_REQ[j] flag.  Set TIME_UPD[j] to the current
         time.  Create an OPT packet and place it in the queue to be
         sent to all neighbors.  Event Processing Complete.

         B) Event Processing Complete.

      II) Event Processing Complete.

4.7.9 Mode Configuration Change or Optimization Timer Event for local
interface "i"
   Increment MODE_SEQ[i]. Create an OPT packet and place it in the queue
   to be sent to all neighbors. If OPT_MODE[i]==PARTIAL ||
   OPT_MODE[i]==FULL, schedule a local optimization timer event for
   interface "i" to occur at a time randomly selected between
   0.5*OPT_PERIOD[i] and 1.5*OPT_PERIOD[i] seconds based on a uniform
   distribution.  Event Processing Complete.

5 Security Considerations

   TBD.

6 Intellectual Property Rights Notice

   Both the University of Maryland and the U.S. Naval Research
   Laboratory have applied for patents relating to the technology
   described in this internet draft.

References

   [1] V. Park and M. S. Corson, A Highly Adaptive Distributed Routing
   Algorithm for Mobile Wireless Networks, Proc. IEEE INFOCOM '97, Kobe,
   Japan (1997).
   [4] M.S. Corson and V. Park, An Internet MANET Encapsulation Protocol
   (IMEP), draft-ietf-

Author's Addresses

   Vincent D. Park
   park@flarion.com
   (908) 947-7084

   M. Scott Corson
   corson@flarion.com
   (908) 947-7033




Park, Corson             Expires 20 January 2002               [Page 22]


INTERNET-DRAFT    Temporally-Ordered Routing Algorithm      20 July 2001


   Flarion Technologies, Inc.
   Bedminster One
   135 Route 202/206 South
   Bedminster, NJ 07921















































Park, Corson             Expires 20 January 2002               [Page 23]


Html markup produced by rfcmarkup 1.124, available from https://tools.ietf.org/tools/rfcmarkup/