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Differences from draft-ietf-manet-tora-spec-01.txt
IETF MANET Working Group V. Park
INTERNET-DRAFT Naval Research Laboratory
draft-ietf-manet-tora-spec-02.txt S. Corson
University of Maryland
22 October 1999
Temporally-Ordered Routing Algorithm (TORA) Version 1
Functional Specification
Status of this Memo
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Abstract
This document provides 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 (to the greatest extent possible) the generation
of far-reaching control message propagation from the dynamics of the
network topology. The basic, underlying algorithm is neither
traditionally distance-vector nor link-state; it is one of a family
of algorithms referred to as "link reversal" algorithms. In
particular, the protocol's reaction to certain link failures is
structured as a temporally-ordered sequence of diffusing
computations, each computation consisting of a sequence of directed
link reversals. The protocol can operate in either a reactive,
proactive or mixed mode.
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1 Introduction
The Temporally-Ordered Routing Algorithm (TORA) [1] is an adaptive
routing protocol for multihop networks. It 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 when possible.
Its operation can be biased towards high reactivity (i.e., low time
complexity) and bandwidth conservation (i.e., low communication
complexity) rather than routing optimality (i.e., continuous
shortest-path computation). Its design and flexability make it
potentially well-suited for use mobile ad hoc networks (MANETs).
TORA is based, in part, on the work presented in [2] and [3]. A key
concept in the protocol's design is an attempt to de-couple (to the
greatest extent possible) the generation of far-reaching control
message propagation from the dynamics of the network topology. The
scope of TORA's control messaging is typically localized to a very
small set of nodes near a topological change. TORA includes a
secondary mechanism that is independent of network topology dynamics,
which allows far-reaching control message propagation as a means of
route optimization or soft-state route verification.
TORA is distributed, in that nodes need only maintain information
about adjacent nodes (i.e., one-hop knowledge). Like a distance-
vector routing approaches, TORA maintains state on a per-destination
basis. Its design allows reactive operation, in which sources
initiate the establishment of routes to a given destination on-
demand, 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. TORA
maintains loop-free routing, and typically provides multiple routes
for any source/destination pair that requires a route. In the event
of a network partition, the protocol detects the partition and erases
invalid routes.
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
identified by an IP address. Associated with each interface is a
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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)
communicating using the *same* communications technology.
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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
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. 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 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 "null" height
are considered undirected and cannot be used for forwarding.
Collectively, the heights of the routers and the link directional
assignments form a multipath routing structure, in which all directed
paths lead downstream to the destination.
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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--resulting a sequence of directed link
reversals (caused by the re-selection of router heights) to re-orient
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 route optimization, 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), clear (CLR), and
optimization (OPT).
3.1 Protocol State
At any given time, an ordered quintuple, HEIGHT = (tau[i], oid[i],
r[i], delta[i], i), is associated with each node i, where i is the
unique ID of the node. Conceptually, the quintuple associated with
each node represents the height of the node as defined by two
parameters: a reference level and an offset with respect to the
reference level. The reference level is represented by the first
three values in the quintuple, while the offset is represented by the
last two values. A new reference level is defined each time a node
loses its last downstream link due to a link failure. The first value
representing the reference level, tau[i], is a time tag set to the
"time" of the link failure. For now, it is assumed that all nodes
have synchronized clocks. This could be accomplished via interface
with an external time source such as the Global Positioning System
(GPS) [5] or through use of an algorithm such as the Network Time
Protocol [6]. This time tag need not actually indicate or be "time,"
nor will relaxation of the synchronization requirement invalidate the
protocol. The second value, oid[i], is the originator-ID (i.e., the
unique ID of the node that defined the new reference level). This
ensures that the reference levels can be totally ordered
lexicographically, even if multiple nodes define reference levels due
to failures that occur simultaneously (i.e., with equal time tags).
The third value, r[i], is a single bit used to divide each of the
unique reference levels into two unique sub-levels. This bit is used
to distinguish between the original reference level and its
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corresponding, higher, reflected reference level. When a distinction
is not required, both the original and reflected reference levels
will simply be referred to as "reference levels." The first value
representing the offset, delta[i], is an integer used to order nodes
with respect to a common reference level. This value is instrumental
in the propagation of a reference level. How delta is selected will
be clarified in a subsequent section. Finally, the second value
representing the offset, i, is the unique ID of the node itself. This
ensures that nodes with a common reference level and equal values of
delta (and in fact all nodes) can be totally ordered
lexicographically at all times.
Each node i (other than the destination) maintains its height,
HEIGHT. Initially the height of each node in the network (other than
the destination) is set to NULL, HEIGHT = (-, -, -, -, i), where i is
the unique ID of the node. Subsequently, the height of each node i
can be modified in accordance with the rules of the protocol. The
height of the destination j is always ZERO, HEIGHT = (0, 0, 0, 0, j),
where j is the unique ID of the destination for which the algorithm
is running). In addition to its own height, each node i maintains a
height table with an entry HT_NEIGH[k] for each neighbor k. Initially
the height of each neighbor is set to NULL, HT_NEIGH[k] = (-, -, -,
-, k). If the destination j is a neighbor of node i, node i sets the
corresponding height entry to ZERO, HT_NEIGH[j] = (0, 0, 0, 0, j).
Each node i (other than the destination) also maintains a link-status
table with an entry LNK_STAT[k] for each link (i, k), where node k is
a neighbor of node i. The status of the links is determined by the
height of the node, HEIGHT, and its height entry for the neighbor,
HT_NEIGH[k]. The link is directed from the higher node to the lower
node. If a neighbor k is higher than node i, the link is marked
upstream (UP). If a neighbor k is lower than node i, the link is
marked downstream (DN). If the neighbor's height entry, HT_NEIGH[k],
is NULL, the link is marked undirected (UN). Finally, if the height
of node i is NULL, then any neighbor's height that is not NULL is
considered lower, and the corresponding link is marked downstream
(DN). When a new link (i, k) is established (i.e., node i has a new
neighbor k), node i adds entries for the new neighbor to the height
and link-status tables. If the new neighbor is the destination j, the
corresponding height entry is set to ZERO, HT_NEIGH[j] = (0, 0, 0, 0,
j); otherwise it is set to NULL, HT_NEIGH[k] = (-, -, -, -, k). The
corresponding link-status entry, LNK_STAT[k], is set as outlined
above. Nodes need not communicate any routing information upon link
activation.
3.2 Creating Routes
Creating routes requires use of the QRY and UPD packets. A QRY packet
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consists of the destination-ID, j, which identifies the destination
for which the algorithm is running. An UPD packet consists of the
destination-ID, j, and the height of the node i that is broadcasting
the packet, HEIGHT.
Each node i (other than the destination) maintains a route-required
flag, which is initially un-set. Each node i (other than the
destination) also maintains the time at which the last UPD packet was
broadcast and the time at which each link (i, k), where node k is
neighbor of node i, became active.
When a node with no directed links and an un-set route-required flag
requires a route to the destination, it broadcasts a QRY packet and
sets its route-required flag. When a node i receives a QRY it reacts
as follows:
a) If the receiving node i has no downstream links and its route-
required flag is un-set, it re-broadcasts the QRY packet and sets
its route-required flag.
b) If the receiving node i has no downstream links and the route-
required flag is set, it discards the QRY packet.
c) If the receiving node i has at least one downstream link and
its height is NULL, it sets its height to HEIGHT = (tau[k],
oid[k], r[k], delta[k] + 1, i), where HT_NEIGH[k] = (tau[k],
oid[k], r[k], delta[k], k) is the minimum height of its non-NULL
neighbors, and broadcasts an UPD packet.
d) If the receiving node i has at least one downstream link and
its height is non-NULL, it first compares the time the last UPD
packet was broadcast to the time the link over which the QRY
packet was received became active. If an UPD packet has been
broadcast since the link became active, it discards the QRY
packet; otherwise, it broadcasts an UPD packet.
If a node has the route-required flag set when a new link is
established, it must broadcast a QRY packet.
When a node i receives an UPD packet from a neighbor k, node i first
updates the entry HT_NEIGH[k] in its height table with the height
contained in the received UPD packet. Node i then updates the entry
LNK_STAT[k] in its link-status table and reacts as follows:
a) If the route-required flag is set (which implies that the
height of node i is NULL), node i sets its height to HEIGHT =
(tau[k], oid[k], r[k], delta[k] + 1, i)--where HT_NEIGH[k] =
(tau[k], oid[k], r[k], delta[k], k) is the minimum height of its
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non-NULL neighbors, updates all the entries in its link-status
table, un-sets the route-required flag and then broadcasts an UPD
packet that contains its new height.
b) If the route-required flag is not set, node i need only react
if it has lost its last downstream link. The section on
maintaining routes discusses the reaction that occurs if reception
of the UPD packet resulted in loss of the last downstream link.
3.3 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.
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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.
(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
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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
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.
3.4 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.
3.5 Optimizing Routes
TBD.
4 Protocol Specification
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The subsequent specification is intended to be of sufficient detail
to serve as a template for implementations.
4.1 Configuration
For each interface "i" of a router, the following configuration
parameters are maintained.
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.
A router is also configured with a router ID (RID), which must be
unique among the set of routers collectively running TORA.
4.2 State Variables
For each destination "j" to which routing is required, a router
maintains the following state variables.
HEIGHT[j] This router's height metric for routing to "j".
PRO_MODE[j] Indicates reactive/proactive mode of operation for "j".
OPT_MODE[j] Indicates optimization mode of operation for "j".
MODE_SEQ[j] Sequence number of most recent mode change regarding "j".
RT_REQ[j] Indicates whether a route to "j" is required.
TIME_UPD[j] Time last UPD packet regarding "j" sent by this router.
For each destination "j" to which routing is required, a router
maintains a separate instance of the following state variables for
each neighbor "k".
HT_NEIGH[j][k] The height metric of neighbor "k."
LNK_STAT[j][k] The assigned status of the link to neighbor "k."
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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.
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.
if HT_NEIGH[k]==NULL then LNK_STAT[k]=UN;
else if HEIGHT==NULL then LNK_STAT[k]=DN;
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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
TBD.
4.7 Event Processing
4.7.1 Initialization
TBD
4.7.2 Connection Status Change
The TORA process receives notification of link status changes. 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, 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 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
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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).
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.
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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
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).
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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).
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
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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).
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).
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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).
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
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TBD.
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).
[2] M.S. Corson and A. Ephremides, A distributed routing algorithm
for mobile wireless networks, Wireless Networks 1 (1995).
[3] E. Gafni and D. Bertsekas, Distributed algorithms for generating
loop-free routes in networks with frequently changing topology, IEEE
Trans. Commun. (January 1981).
[4] M.S. Corson and V. Park, An Internet MANET Encapsulation Protocol
(IMEP), draft-ietf-
[5] NAVSTAR GPS user equipment introduction, MZ10298.001 (February
1991).
[6] D. Mills, Network time protocol, specification, implementation
and analysis, Internet RFC-1119 (September 1989).
Author's Addresses
Vincent D. Park
Information Technology Division
Naval Research Laboratory
Washington, DC 20375
(202) 767-5098
vpark@itd.nrl.navy.mil
M. Scott Corson
Institute for Systems Research
University of Maryland
College Park, MD 20742
(301) 405-6630
corson@isr.umd.edu
Park, Corson Expires 22 April 2000 [Page 19]
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