draft-ietf-manet-lanmar-02.txt   draft-ietf-manet-lanmar-03.txt 
IETF MANET Working Group Mario Gerla IETF MANET Working Group Mario Gerla
INTERNET-DRAFT Xiaoyan Hong INTERNET-DRAFT Xiaoyan Hong
Expiration: November 17, 2001 Li Ma Expiration: June 17, 2002 Li Ma
University of California, Los Angeles University of California, Los Angeles
Guangyu Pei Guangyu Pei
Rockwell Science Center Rockwell Scientific Company
May 17, 2001 December 17, 2001
Landmark Routing Protocol (LANMAR) for Large Scale Ad Hoc Networks Landmark Routing Protocol (LANMAR) for Large Scale Ad Hoc Networks
<draft-ietf-manet-lanmar-02.txt> <draft-ietf-manet-lanmar-03.txt>
Status of This Memo Status of This Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is subject to all provisions
all provisions of Section 10 of RFC 2026 except that the right to of Section 10 of RFC2026.
produce derivative works is not granted.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note Task Force (IETF), its areas, and its working groups. Note
that other groups may also distribute working documents as that other groups may also distribute working documents as
Internet-Drafts. Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at and may be updated, replaced, or obsoleted by other documents at
any time. It is inappropriate to use Internet-Drafts as reference any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress". material or to cite them other than as "work in progress".
skipping to change at page 2, line 15 skipping to change at page 2, line 15
efficiently reflected in the addressing scheme. It assumes that efficiently reflected in the addressing scheme. It assumes that
an IP like address is used consisting of a group ID (or subnet ID) an IP like address is used consisting of a group ID (or subnet ID)
and a host ID, i.e. <Group ID, Host ID>. A landmark is dynamically and a host ID, i.e. <Group ID, Host ID>. A landmark is dynamically
elected in each group. The route to a landmark is propagated elected in each group. The route to a landmark is propagated
throughout the network using a Distance Vector mechanism. throughout the network using a Distance Vector mechanism.
Separately, each node in the network uses a "scoped" routing Separately, each node in the network uses a "scoped" routing
algorithm (e.g., FSR) to learn about routes within a given (max algorithm (e.g., FSR) to learn about routes within a given (max
number of hops) scope. To route a packet to a destination outside number of hops) scope. To route a packet to a destination outside
its scope, a node will direct the packet to the landmark its scope, a node will direct the packet to the landmark
corresponding to the group ID of such destination. Once the packet corresponding to the group ID of such destination. Once the packet
is within the scope of the landmark, it will typically be routed approaches the landmark, it will typically be routed directly to
directly to the destination. Remote groups of nodes are the destination. A solution to nodes outside of the scope of their
"summarized" by the corresponding landmarks. The solution to landmark (i.e., drifters) is also addressed in the draft. Thus,
drifters (i.e., nodes outside of the scope of their landmark) is by "summarizing" in the corresponding landmarks the routing
also handled by LANMAR. Landmark dynamic election enables LANMAR information of remote groups of nodes and by using the truncated
to cope with mobile environments. Thus, by using the truncated local routing table, LANMAR dramatically reduces routing table size
local routing table and the "summarized" landmark distance vector, and routing update overhead in large networks. The dynamic
LANMAR dramatically reduces routing table size and update overhead election of landmarks enables LANMAR to cope with mobile
in large nets. LANMAR is well suited to provide an efficient and environments. LANMAR is well suited to provide an efficient and
scalable routing solution in large, mobile, ad hoc environments in scalable routing solution in large, mobile, ad hoc environments in
which group behavior applies and high mobility renders traditional which group behavior applies and high mobility renders traditional
routing schemes inefficient. routing schemes inefficient.
Contents Contents
Status of This Memo . . . . . . . . . . . . . . . . . . . . . . . 1 Status of This Memo . . . . . . . . . . . . . . . . . . . . . . . 1
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Changes ....................................................... 5 2. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. General Terms . . . . . . . . . . . . . . . . . . . . . 5 3.1. General Terms . . . . . . . . . . . . . . . . . . . . . 5
3.2. Specification Language . . . . . . . . . . . . . . . . . 5 3.2. Specification Language . . . . . . . . . . . . . . . . . 6
4. Protocol Applicability . . . . . . . . . . . . . . . . . . . . 6 4. Protocol Applicability . . . . . . . . . . . . . . . . . . . . 6
4.1. Networking Context . . . . . . . . . . . . . . . . . . . 6 4.1. Networking Context . . . . . . . . . . . . . . . . . . . 6
4.2. Protocol Characteristics and Mechanisms . . . . . . . . 6 4.2. Protocol Characteristics and Mechanisms . . . . . . . . 6
5. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 8 5. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Protocol Descriptions . . . . . . . . . . . . . . . . . 8 5.1. Protocol Descriptions . . . . . . . . . . . . . . . . . 8
5.2. Landmark Election . . . . . . . . . . . . . . . . . . . 9 5.2. Landmark Election . . . . . . . . . . . . . . . . . . . 9
5.3. Drifters . . . . . . . . . . . . . . . . . . . . . . . . 10 5.3. Drifters . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Protocol Specifications . . . . . . . . . . . . . . . . . . . 10 6. Protocol Specifications . . . . . . . . . . . . . . . . . . . 10
6.1. Data Structures . . . . . . . . . . . . . . . . . . . 11 6.1. Data Structures . . . . . . . . . . . . . . . . . . . 10
6.1.1 Landmark Status tuple . . . . . . . . . . . . . . 11 6.1.1 Landmark Status tuple . . . . . . . . . . . . . . 11
6.1.2 Landmark Distance Vector . . . . . . . . . . . . 11 6.1.2 Landmark Distance Vector . . . . . . . . . . . . 11
6.1.3 Drifter List . . . . . . . . . . . . . . . . . . 11 6.1.3 Drifter List . . . . . . . . . . . . . . . . . . 11
6.1.4 Neighbor List . . . . . . . . . . . . . . . . . . 12 6.1.4 Neighbor List . . . . . . . . . . . . . . . . . . 11
6.2. LANMAR Update Message Format . . . . . . . . . . . . 12 6.2. LANMAR Update Message Format . . . . . . . . . . . . 11
6.2.1 Description of the fields . . . . . . . . . . . . 12 6.2.1 Description of the fields . . . . . . . . . . . . 12
6.3. Processing Landmark Updates . . . . . . . . . . . . . . 13 6.3. Processing Landmark Updates . . . . . . . . . . . . . . 13
6.3.1 Originating a Landmark in a Subnet . . . . . . . 13 6.3.1 Originating a Landmark in a Subnet . . . . . . . 13
6.3.2 Receiving Landmark Updates . . . . . . . . . . . 14 6.3.2 Receiving Landmark Updates . . . . . . . . . . . 13
6.3.3 Winner Competition . . . . . . . . . . . . . . . 14 6.3.3 Winner Competition . . . . . . . . . . . . . . . 14
6.4. Processing Drifter Updates . . . . . . . . . . . . . . . 14 6.4. Processing Drifter Updates . . . . . . . . . . . . . . . 14
6.4.1 Originating a Drifter Entry . . . . . . . . . . . 15 6.4.1 Originating a Drifter Entry . . . . . . . . . . . 14
6.4.2 Receiving Drifter Updates . . . . . . . . . . . . 15 6.4.2 Receiving Drifter Updates . . . . . . . . . . . . 14
6.4.3 Removing a Drifter Entry . . . . . . . . . . . . 15 6.4.3 Removing a Drifter Entry . . . . . . . . . . . . 15
6.5. Processing Neighbor List . . . . . . . . . . . . . . . . 15 6.5. Processing Neighbor List . . . . . . . . . . . . . . . . 15
6.6. Processing Lost Neighbor . . . . . . . . . . . . . . . . 15
7. Data Packet Forwarding . . . . . . . . . . . . . . . . . . . . 15 7. Data Packet Forwarding . . . . . . . . . . . . . . . . . . . . 15
8. Discussion about Storage and Processing Overhead for Drifters 16 8. Discussion about Storage and Processing Overhead for Drifters 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. Scoped Routing Operations . . . . . . . . . . . . . . . . . . 16
9.1. Fisheye State Routing Protocol . . . . . . . . . . . . . 16
9.2. Destination-Sequenced Distance Vector Routing Protocol . 16
9.3. Optimized Link State Routing Protocol . . . . . . . . . 16
References . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chair's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chair's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
This document describes the Landmark Routing Protocol (LANMAR) [1,2] This document describes the Landmark Routing Protocol (LANMAR) [1,2]
developed by the Wireless Adaptive Mobility (WAM) Laboratory [4] at developed by the Wireless Adaptive Mobility (WAM) Laboratory [4] at
Computer Science Department, University of California, Los Angeles. Computer Science Department, University of California, Los Angeles.
The concept of landmark routing was first introduced in wired area The concept of landmark routing was first introduced in wired area
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as a packet approaches its destination. as a packet approaches its destination.
LANMAR borrows the concept of landmark and extends it to the LANMAR borrows the concept of landmark and extends it to the
wireless ad hoc environment. LANMAR scheme does not require wireless ad hoc environment. LANMAR scheme does not require
predefined hierarchical address, but it uses the notion of landmarks predefined hierarchical address, but it uses the notion of landmarks
to keep track of logical subnets in which the members have a to keep track of logical subnets in which the members have a
commonality of interests and are likely to move as a "group" commonality of interests and are likely to move as a "group"
(e.g., brigade in the battlefield, a group of students from same (e.g., brigade in the battlefield, a group of students from same
class and a team of co-workers at a convention). Each such class and a team of co-workers at a convention). Each such
logical group has an elected landmark. For each group, logical group has an elected landmark. For each group,
underlying "scoped" routing algorithm will provide a one-level the underlying "scoped" routing algorithm will provide accurate
scope. The routing update packets are restricted only within the routing information for nodes within scope. The routing
scope. Accurate routing information for nodes within scope is update packets are restricted only within the scope. The
maintained. The routing information to remote nodes (nodes outside routing information to remote nodes (nodes outside the node's
the node's scope) is "summarized" by the corresponding landmarks. scope) is "summarized" by the corresponding landmarks. Thus,
Thus, the LANMAR scheme largely reduces the routing table size and the LANMAR scheme largely reduces the routing table size and
the routing update traffic overhead. It greatly improves the routing update traffic overhead. It greatly improves
scalability. scalability.
In addition, in order to recover from landmark failures, In addition, in order to recover from landmark failures,
a "landmark" node is elected in each subnet. Landmark election a "landmark" node is elected in each subnet. Landmark election
provides a flexible way for the LANMAR protocol to cope with a provides a flexible way for the LANMAR protocol to cope with a
dynamic and mobile network. The protocol also provides a solution dynamic and mobile network. The protocol also provides a solution
for drifters (Nodes that are outside the fisheye scopes of the for nodes that are outside the scopes of the landmarks of
landmarks of their logical groups). Extra storage, processing and their logical groups (drifters). Extra storage, processing and
line overhead will be incurred for landmark election and drifter line overhead will be incurred for landmark election and drifter
bookkeeping. However, the design of the algorithms provides bookkeeping. However, the design of the algorithms provides
solutions without compromising scalability. For example, the solutions without compromising scalability. For example, the
routing overhead for handling drifters is typically small if the routing overhead for handling drifters is typically small if the
fraction of drifting nodes is small. More analysis is given in fraction of drifting nodes is small. More analysis is given in
Section 8. Section 8.
The LANMAR runs on top of a proactive routing protocol. It The LANMAR runs on top of a proactive routing protocol. It
requires that the underlying routing protocol support the scoped requires that the underlying routing protocol support the scoped
subnetworking. Fisheye State Routing Protocol (FSR) [7,8] is subnetworking. Fisheye State Routing Protocol (FSR) [7,8] is
such a protocol that supports LANMAR. In FSR, the link state such a protocol that supports LANMAR. In FSR, the link state
protocol is used within the scope. The fisheye scope protocol is used within the scope. The scope technique
technique can also be applied to a distance vector type protocol, can also be applied to a distance vector type protocol,
such as DSDV [3], in which the hop distance can be used to such as DSDV [3], in which the hop distance can be used to
bind the scope for routing message updating. The main advantage of limit the scope of routing message updating. The main advantage of
LANMAR is that the routing table includes only the nodes within the LANMAR is that the routing table includes only the nodes within the
scope and the landmark nodes. This feature greatly improves scope and the landmark nodes. This feature greatly improves
scalability by reducing routing table size and update traffic O/H. scalability by reducing routing table size and update traffic O/H.
Thus the Landmark Routing Protocol provides an efficient and Thus the Landmark Routing Protocol provides an efficient and
scalable routing solution for a mobile, ad hoc environment while scalable routing solution for a mobile, ad hoc environment while
keeping line and storage overhead (O/H) low. Moreover, the keeping line and storage overhead (O/H) low. Moreover, the
election provides a much needed recovery from landmark failures. election provides a much needed recovery from landmark failures.
2. Changes 2. Changes
Major changes from version 02 to version 03:
- A drifter sequence number is used in drifter list to indicate
each new occurrence of a drifter.
- Processing of lost neighbors is added.
- A separate section describing the modifications made to various
proactive protocols. Operations of these protocols will then
only perform within a certain hop distances.
- Editorial changes.
Major changes from version 01 to version 02:
- Update of "Status of This Memo".
Major changes from version 00 to version 01: Major changes from version 00 to version 01:
- A destination sequence number for each landmark is used to - A destination sequence number for each landmark is used to
ensure loop-free updates for a particular landmark. ensure loop-free updates for a particular landmark.
- Landmark updates are propagated in separate messages, instead of - Landmark updates are propagated in separate messages, instead of
being piggybacked on local routing updates. This modification being piggybacked on local routing updates. This modification
decouples landmark routing from the underlying proactive routing decouples landmark routing from the underlying proactive routing
protocol. protocol.
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node node
A MANET router that implements Landmark Routing Protocol. A MANET router that implements Landmark Routing Protocol.
neighbor neighbor
Nodes that are within the radio transmission range. Nodes that are within the radio transmission range.
scope scope
A zone that is bounded by hop distances. A network area that is centered at each node and bounded
by a certain maximum hop distances.
host protocol host protocol
A proactive protocol underlies the Landmark Routing Protocol. Also known as local routing protocl, i.e., a proactive
protocol that works together with the Landmark Routing
Protocol, but only operates within the scope of each node.
underlying protocol
This term is used interchangeably with host protocol.
scoped routing protocol
A routing protocol that only exchanges routing information
up to a certain hop distance (scope).
subnet subnet
Logical groups of nodes that present similar motion behavior. Logical groups of nodes that present similar motion behavior.
group group
This term is used interchangeably with subnet. This term is used interchangeably with subnet.
3.2. Specification Language 3.2. Specification Language
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [5]. document are to be interpreted as described in RFC 2119 [5].
4. Protocol Applicability 4. Protocol Applicability
4.1. Networking Context 4.1. Networking Context
LANMAR is best suited for large scale mobile ad hoc wireless LANMAR is best suited for large scale mobile ad hoc wireless
networks. The landmark scheme on top of "scoped" routing algorithm networks. The landmark scheme on top of a "scoped" routing
has large advantages in reducing routing update packet size and algorithm has large advantages in reducing routing update packet
keeping progressive accurate routes to remote nodes. It achieves size and keeping reasonably accurate routes to remote nodes.
high data packet delivery ratio. Moreover, the fact that the route It achieves high data packet delivery ratio. Moreover, the fact
error is blurred by distance obviously reduces the sensitivity to that the route error is blurred by distance obviously reduces the
network size. sensitivity to network size.
LANMAR is also suited for high mobility ad hoc wireless networks. LANMAR is also suited for high mobility ad hoc wireless networks.
This is because in a mobility environment, a change on a link far This is because in a mobile environment, a change on a link far
away from the source does not necessarily cause a change in the away from the source does not necessarily cause a change in the
routing table at the source and that all the information about routing table at the source since all the information about
remote nodes is summarized by landmarks. remote nodes is summarized by landmarks.
4.2. Protocol Characteristics and Mechanisms 4.2. Protocol Characteristics and Mechanisms
* Does the protocol provide support for unidirectional links?(if so, * Does the protocol provide support for unidirectional links?(if so,
how?) how?)
No. No.
* Does the protocol require the use of tunneling? (if so, how?) * Does the protocol require the use of tunneling? (if so, how?)
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5. Protocol Overview 5. Protocol Overview
5.1. Protocol Descriptions 5.1. Protocol Descriptions
As mentioned in Section 1, the landmark concept we adopt here uses As mentioned in Section 1, the landmark concept we adopt here uses
the notion of logical subnets in which the members have a the notion of logical subnets in which the members have a
commonality of interests and are likely to move as a "group". commonality of interests and are likely to move as a "group".
Each logical subnet has one node serving as a "landmark" of that Each logical subnet has one node serving as a "landmark" of that
subnet. The protocol requires that the landmark of each subnet have subnet. The protocol requires that the landmark of each subnet have
the knowledge of all the members in its group. The LANMAR protocol the knowledge of all the members in its group. The LANMAR protocol
also uses a scope at each node. The size of the scope is a also uses a routing scope at each node. The size of the scope is a
parameter measured in hop distance. It is chosen in such a way that parameter measured in hop distance. It is chosen in such a way that
if a node is at the center of a subnet, the scope will cover the if a node is at the center of a subnet, the scope will cover the
majority of the subnet members. If the shape of a subnet is likely majority of the subnet members. If the shape of a subnet is likely
to be a cycle, the center node's scope will cover all the members of to be a cycle, the center node's scope will cover all the members of
the subnet. If this center node is elected as a landmark, it the subnet. If this center node is elected as a landmark, it
fulfills the requirement of the protocol. The elected landmark fulfills the requirement of the protocol. The elected landmark
uses a destination sequence number to ensure its routing entry uses a destination sequence number to ensure its routing entry
update is loop-free. The landmarks are propagated in a update loop-free. The landmarks are propagated in a
distance vector mechanism. Each node maintains a distance vector distance vector mechanism. Each node maintains a distance vector
for landmarks of all the subnets. The size of the landmark distance for landmarks of all the subnets. The size of the landmark distance
vector equals to the number of logical subnets and thus landmark vector equals to the number of logical subnets and thus landmark
nodes. If a landmark does not locate at the center, there will be nodes. If a landmark does not locate at the center, there will be
some members drifting off its scope. The landmark will keep a some members drifting off its scope. The landmark will keep a
distance vector for drifters of its group. The distance vectors distance vector for drifters of its group. The distance vectors
for landmarks and drifters are exchanged among neighbors in for landmarks and drifters are exchanged among neighbors in
periodical routing update packets. periodical routing update packets.
The LANMAR relies on an underlying proactive protocol with the The LANMAR relies on an underlying proactive protocol with the
ability of providing "scoped" routing. In the scoped routing, each ability of providing "scoped" routing. In the scoped routing, each
node broadcasts routing information periodically to its immediate node broadcasts routing information periodically to its immediate
neighbors. In each update packet, the node sends routing table neighbors. In each update packet, the node includes all the
entries within its scope. The host routing protocol uses sequence routing table entries within the scope centered at it.
numbers for routing entries. Each node advances its sequence
number before sending an update packet. Through the exchange
process, the table entries with larger sequence numbers replace
the ones with smaller sequence numbers.
Let's take, for example, the FSR as our host protocol. For nodes
within the scope, the updating is in a certain frequency. But
for nodes beyond the scope, the update frequency is reduced to
zero; Only the update frequency of the landmark nodes remains
unaltered. As a result, each node maintains accurate routing
information for in-scope nodes and keep routing directions to the
landmark nodes for out-scope nodes, or say, for remote groups.
A packet directed to a remote destination initially aims at the
landmark of that remote group; as it gets closer to the landmark,
it may eventually switch to the accurate route to the destination
provided by in-scope nodes of the destination.
5.2. Landmark Election 5.2. Landmark Election
Dynamic election/re-election of landmark node is essential for Dynamic election/re-election of landmark node is essential for
LANMAR to work in a wireless mobile environment. Basically, each LANMAR to work in a wireless mobile environment. Basically, each
node tracks other nodes of its group in its scope and computes node tracks other nodes of its group in its scope and computes
"weight", e.g. the number of the nodes it has found. At the "weight", e.g. the number of the nodes it has found. At the
beginning of the LANMAR, no landmark exists. Protocol LANMAR beginning of the LANMAR, no landmark exists. Protocol LANMAR
only uses the host protocol functionality. As host routing only uses the host protocol functionality. As host routing
computation progresses, one of the nodes will learn (from computation progresses, one of the nodes will learn (from
the host protocol's routing table) that more than a certain number the host protocol's routing table) that more than a certain number
of group members (say, T) are in its scope. It then proclaims of group members (say, T) are in its scope. It then proclaims
itself as a landmark for this group and adds itself to the landmark itself as a landmark for this group and adds itself to the landmark
distance vector. Landmarks broadcast the election weights to distance vector. Landmarks broadcast the election weights to
the neighbors jointly with the landmark update packets. the neighbors jointly with the landmark distance vector update
packets.
When more than one node declares itself as a landmark in the same When more than one node declares itself as a landmark in the same
group, as the landmark information floods out, each node will group, as the landmark information floods out, each node will
perform a winner competition procedure. Only one landmark for each perform a winner competition procedure. Only one landmark for each
group will survive and it will be elected. To avoid flapping group will survive and it will be elected. To avoid flapping
between landmarks (very possible in a mobile situation), we use between landmarks (very possible in a mobile situation), we use
hysteresis in the replacement of an existing landmark. I.e., the hysteresis in the replacement of an existing landmark. I.e., the
old Landmark is replaced by the new one only if its weight is, say old Landmark is replaced by the new one only if its weight is, say
less than 1/2 of the weight of the current election winner. Once less than 1/2 of the weight of the current election winner. Once
ousted, the old leader needs the full weight superiority to be ousted, the old leader needs the full weight superiority to be
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neighbor, say j, then j will retain the entry to member l only if neighbor, say j, then j will retain the entry to member l only if
d(j,l) is smaller than the scope or d(j,L) is smaller than d(i,L). d(j,l) is smaller than the scope or d(j,L) is smaller than d(i,L).
The latter condition occurs if j is on the shortest path from i The latter condition occurs if j is on the shortest path from i
(and therefore from l) to L. This way, a path is maintained from (and therefore from l) to L. This way, a path is maintained from
the landmark to each of its members, including drifters. The the landmark to each of its members, including drifters. The
procedure starts from l, at the time when a node finds it becomes procedure starts from l, at the time when a node finds it becomes
a drifter. It informs the landmark hop by hop about its presence. a drifter. It informs the landmark hop by hop about its presence.
The occurrences of drifters are dynamic in a mobile network. In The occurrences of drifters are dynamic in a mobile network. In
order to timely remove the staled drifter information, the time order to timely remove the staled drifter information, the time
when a node hears a drifter is recorded. when a node hears a drifter is recorded. A node monitors whether
it becomes a drifter periodically and refreshes its occurrence
along the path towards the landmark.
6. Protocol Specifications 6. Protocol Specifications
This section discusses the operation of LANMAR routing protocol. This section discusses the operation of LANMAR routing protocol.
The sending and receiving of landmark updates are in the proactive The sending and receiving of landmark updates are in the proactive
nature. The routing packets are processed separately from nature. The routing packets are processed separately from
ordinary data packets. ordinary data packets.
6.1. Data Structures 6.1. Data Structures
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6.1.3. Drifter List 6.1.3. Drifter List
The drifter list (DFDV) of LANMAR provides the next hop information The drifter list (DFDV) of LANMAR provides the next hop information
of the drifters known to the current node. The entries are updated of the drifters known to the current node. The entries are updated
with landmark update message. The latest time a drifter is heard with landmark update message. The latest time a drifter is heard
is recorded in DFDV. The DFDV works as a part of routing table. is recorded in DFDV. The DFDV works as a part of routing table.
It has the following fields: It has the following fields:
- Destination drifter address - Destination drifter address
- Next hop address - Next hop address
- Distance - Distance
- Drifter sequence number
- Last heard time - Last heard time
6.1.4. Neighbor List 6.1.4. Neighbor List
The neighbor list of LANMAR keeps current neighbor information for The neighbor list of LANMAR keeps current neighbor information for
a node. The latest time a neighbor is heard is recorded. The a node. The latest time a neighbor is heard is recorded. The
neighbor list has the following fields: neighbor list has the following fields:
- Neighbor address - Neighbor address
- Neighbor landmark flag - Neighbor landmark flag
- Last heard time - Last heard time
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| Next Hop Address 1 | | Next Hop Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Distance 1 | N_members 1 | Sequence Number 1 : | Distance 1 | N_members 1 | Sequence Number 1 :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: . . . : : . . . :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Drifter Address 1 | | Drifter Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Hop Address 1 | | Next Hop Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Distance 1 | ... : | Distance 1 | Drifter Sequence Number 1 | ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: . . . | : . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6.2.1. Description of the fields 6.2.1. Description of the fields
Landmark Flag Landmark Flag
The landmark flag of the sending node. The landmark flag of the original sender.
N_landmarks N_landmarks
The number of entries of the landmark distance vector. The number of entries of the landmark distance vector.
N_drifters N_drifters
The number of entries of the drifter list. The number of entries of the drifter list.
Reserved Reserved
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The first entry in the landmark distance vector. The first entry in the landmark distance vector.
Landmark Address 1, N_members 1 and Sequence Number 1 are the Landmark Address 1, N_members 1 and Sequence Number 1 are the
status tuple of the destination landmark. status tuple of the destination landmark.
Next Hop Address 1 and Distance 1 is the next hop and distance Next Hop Address 1 and Distance 1 is the next hop and distance
to the landmark. to the landmark.
These fields are repeated N_landmarks times for each entry in These fields are repeated N_landmarks times for each entry in
landmark distance vector. landmark distance vector.
Drifter Address 1, Next Hop Address 1 and Distance 1 Drifter Address 1, Next Hop Address 1, Distance 1 and
Drifter Sequence Number 1
The first entry in the drifter list. The first entry in the drifter list.
Next Hop Address 1 and Distance 1 are the next hop and distance Next Hop Address 1 and Distance 1 are the next hop and distance
to the Drifter Address 1. to the Drifter Address 1.
These fields are repeated N_drifters times for each entry in These fields are repeated N_drifters times for each entry in
the drifter list. the drifter list.
The length of the message is limited to the maximum IP packet size. The length of the message is limited to the maximum IP packet size.
In that case, multiple packets may be required to broadcast all the In that case, multiple packets may be required to broadcast all the
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6.3.1. Originating a Landmark in a Subnet 6.3.1. Originating a Landmark in a Subnet
Every time a node detects a neighbor change, it recalculates the Every time a node detects a neighbor change, it recalculates the
number of group members in its scope. The new number of group number of group members in its scope. The new number of group
members is recorded in its election weight field. If this members is recorded in its election weight field. If this
number is greater than a threshold T, the node qualifies as a number is greater than a threshold T, the node qualifies as a
landmark only when it is the only landmark for the group so far, landmark only when it is the only landmark for the group so far,
or it wins the election when competing with the existing landmark. or it wins the election when competing with the existing landmark.
When it becomes a landmark, it increases its sequence number by 2. When it becomes a landmark, it increases its sequence number by 2.
The old landmark entry is replaced with the new winner. The Its current landmark status tuple will be inserted into the LMDV
or the existing landmark is replaced with the new winner. The
landmark entry will be broadcast to neighbors with the next update landmark entry will be broadcast to neighbors with the next update
packet. Every time before a landmark sends updates, it increases packet.
its sequence number and copies it to LMDV.
6.3.2. Receiving Landmark Updates 6.3.2. Receiving Landmark Updates
When a node receives a landmark update message, it compares its When a node receives a landmark update message, it compares its
LMDV entries with the incoming LMDV updates for each subnet. LMDV entries with the incoming LMDV updates for each subnet.
A landmark update corresponding to a new subnet will be copied. A landmark update corresponding to a new subnet will be copied.
An update having the same landmark as already given (in node's LMDV) An update having the same landmark as already given (in node's LMDV)
will be accepted only if it contains a larger sequence number. will be accepted only if it contains a larger sequence number.
If an update contains a different landmark for the same subnet as If an update contains a different landmark for the same subnet as
recorded in LMDV, only one landmark will be elected through a recorded in LMDV, only one landmark will be elected through a
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6.4.1. Originating a Drifter Entry 6.4.1. Originating a Drifter Entry
By checking the distance to the landmark of its group, each node By checking the distance to the landmark of its group, each node
easily knows whether it has become a drifter. If the distance is easily knows whether it has become a drifter. If the distance is
larger than the scope, the node will put itself into its drifter larger than the scope, the node will put itself into its drifter
list. This drifter information will be sent back to the landmark list. This drifter information will be sent back to the landmark
hop by hop along the shortest path to it which can be learned from hop by hop along the shortest path to it which can be learned from
the LMDV. For each drifter, only the node on its shortest path the LMDV. For each drifter, only the node on its shortest path
to the landmark needs to receive its information, so before the to the landmark needs to receive its information, so before the
entry is broadcast, the next hop to landmark is attached with entry is broadcast, the next hop to landmark is attached with
its entry. The DFDV will be propagated with the next update packet. its entry. Each drifter maintains a drifter sequence number.
Each time a node finds itself a drifter, the sequence number
will be increased by 2. The DFDV will be propagated with the
next update packet.
6.4.2. Receiving Drifter Updates 6.4.2. Receiving Drifter Updates
Upon receiving an update packet, the DFDV part is retrieved and Upon receiving an update packet, the DFDV part is retrieved and
processed. If an entry of incoming DFDV indicates that the current processed. If an entry of incoming DFDV indicates that the current
node is its next hop to the landmark, i.e., the current node is on node is its next hop to the landmark, i.e., the current node is on
the drifter's shortest path to the landmark, the current node will the drifter's shortest path to the landmark, the current node will
insert or update its drifter list. The receiving time is stamped insert or update its drifter list. The receiving time is stamped
in the DFDV. The node sending the update packet is recorded as the in the DFDV. The node sending the update packet is recorded as the
next hop to the drifter. The reverse path to the drifter is thus next hop to the drifter. The reverse path to the drifter is thus
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6.5. Processing Neighbor List 6.5. Processing Neighbor List
When a node receives either a landmark update or a host protocol When a node receives either a landmark update or a host protocol
routing update, the neighbor list is inserted if the update comes routing update, the neighbor list is inserted if the update comes
from a new neighbor, or the corresponding neighbor entry is from a new neighbor, or the corresponding neighbor entry is
updated. Current time is recorded with the entry. The updated. Current time is recorded with the entry. The
neighbor list is also search at this time for possible lost neighbor list is also search at this time for possible lost
neighbors according to the time stamps. If such a neighbor is neighbors according to the time stamps. If such a neighbor is
found, it is removed from the list. found, it is removed from the list.
6.6. Processing Lost Neighbor
A lost neighbor will be discovered by checking staled entries in
the neighbor list or by feedback from the MAC layer protocol.
A neighbor loss leads to searches in LMDV and DFDV. If the lost
neighbor happens to be the next hop to a landmark or a drifter,
the corresponding table entry is removed.
7. Data Packet Forwarding 7. Data Packet Forwarding
Data packets are relayed hop by hop. The host protocol routing Data packets are relayed hop by hop. The host protocol routing
table, drifter list and landmark distance vector are looked up table, drifter list and landmark distance vector are looked up
sequentially for the destination entry. If the destination is sequentially for the destination entry. If the destination is
within a node's scope, the entry can be found directly in the within a node's scope, the entry can be found directly in the
routing table and the packet is forwarded to the next hop node. routing table and the packet is forwarded to the next hop node.
Otherwise, the drifter list DFDV is searched for the destination. Otherwise, the drifter list DFDV is searched for the destination.
If the entry is found, the packet is forwarded using the next hop If the entry is found, the packet is forwarded using the next hop
address from DFDV. If not, the logical subnet field of the address from DFDV. If not, the logical subnet field of the
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path to the drifter. The total number of extra routing entries is path to the drifter. The total number of extra routing entries is
sqrt(N)*L*(F*N/L) where N/L is the average logical group size. sqrt(N)*L*(F*N/L) where N/L is the average logical group size.
Thus, the extra storage per node is F*sqrt(N). Now, let us assume Thus, the extra storage per node is F*sqrt(N). Now, let us assume
that the number of nodes in the scope = # of landmarks = logical that the number of nodes in the scope = # of landmarks = logical
group size = sqrt(N). Then, the basic routing table overhead per group size = sqrt(N). Then, the basic routing table overhead per
node (excluding drifters) is 3*sqrt(N). Thus, the extra overhead node (excluding drifters) is 3*sqrt(N). Thus, the extra overhead
caused by drifters is F/3. If 20% of the nodes in a group are caused by drifters is F/3. If 20% of the nodes in a group are
outside of the landmark scope, i.e., have drifted, the extra outside of the landmark scope, i.e., have drifted, the extra
routing O/H required to keep track of them is only 7%. routing O/H required to keep track of them is only 7%.
9. Scoped Routing Operations
9.1. Fisheye State Routing protocol
Fisheye State Routing (FSR) [7][8] is easy to adapt to a host
protocol. A two level Fisheye scope is used when FSR is used
for host protocol. For nodes within the scope, the updating
is in a certain frequency. But for nodes beyond the scope,
the update frequency is reduced to zero; Only the update
frequency of the landmark nodes remains unaltered. As a result,
each node maintains accurate routing information for in-scope
nodes and keep routing directions to the landmark nodes for
out-scope nodes, or say, for remote groups. A packet directed
to a remote destination initially aims at the landmark of that
remote group; as it gets closer to the landmark, it may
eventually switch to the accurate route to the destination
provided by in-scope nodes of the destination.
9.2. Destination-sequenced Distance Vector Routing protocol
Distance Vector type routing protocols use smaller routing
tables (comparing to Link State type) and generate lower routing
overhead. Destination-sequenced Distance Vector Routing (DSDV) [3]
uses destination sequenced sequence numbers to prevent the
forming of loops. The protocol can also work together with
LANMAR. The modifications include containing only the
destinations within the local scope in the periodic routing
update messages and turning off the triggered updates.
9.3. Optimized Link State Routing protocol
Optimized Link State Routing (OLSR) [9] provides the facility
for scope-limited flooding of messages. The generic message
format contains a "Time To Live" field, which gives the maximum
number of hops that a message will travel. Each time a message
is retransmitted, the "Time To Live" field is decreased by 1.
When the value of this field is reduced to zero, the massage
will not be forwarded any more.
OLSR can be one of the underlying protocol of LANMAR. The
"Time To Live" field is set to the scope defined in LANMAR
when a message is originated. The advantage of the combination
is the scalability to both dense and sparse network with
large number of nodes and large terrain size.
Acknowledgments Acknowledgments
This work was supported in part by NSF under contract ANI-9814675, This work was supported in part by NSF under contract ANI-9814675,
by DARPA under contract DAAB07-97-C-D321, and by ONR under by DARPA under contract DAAB07-97-C-D321, and by ONR under
contract N00014-01-C-0016. contract N00014-01-C-0016.
References References
[1] G. Pei, M. Gerla and X. Hong, "LANMAR: Landmark Routing for [1] G. Pei, M. Gerla and X. Hong, "LANMAR: Landmark Routing for
Large Scale Wireless Ad Hoc Networks with Group Mobility", Large Scale Wireless Ad Hoc Networks with Group Mobility",
skipping to change at page 17, line 32 skipping to change at page 18, line 5
vol.18, no.4, Aug. 1988, pp. 35-42. vol.18, no.4, Aug. 1988, pp. 35-42.
[7] G. Pei, M. Gerla, and T.-W. Chen, "Fisheye State Routing: [7] G. Pei, M. Gerla, and T.-W. Chen, "Fisheye State Routing:
A Routing Scheme for Ad Hoc Wireless Networks", Proceedings of A Routing Scheme for Ad Hoc Wireless Networks", Proceedings of
ICC 2000, New Orleans, LA, Jun. 2000. ICC 2000, New Orleans, LA, Jun. 2000.
[8] G. Pei, M. Gerla, and T.-W. Chen, "Fisheye State Routing in [8] G. Pei, M. Gerla, and T.-W. Chen, "Fisheye State Routing in
Mobile Ad Hoc Networks", Proceedings of Workshop on Wireless Mobile Ad Hoc Networks", Proceedings of Workshop on Wireless
Networks and Mobile Computing, Taipei, Taiwan, Apr. 2000. Networks and Mobile Computing, Taipei, Taiwan, Apr. 2000.
[9] P. Jacquet, P. Muhlethaler, A. Qayyum, A. Laouiti, L. Viennot
and T. Clausen, "Optimized Link State Routing Protocol", Internet
Draft, IETF MANET Working Group, draft-ietf-manet-olsr-04.txt,
Mar. 2001.
Chair's Address Chair's Address
The MANET Working Group can be contacted via its current chairs: The MANET Working Group can be contacted via its current chairs:
M. Scott Corson M. Scott Corson
Institute for Systems Research Flarion Technologies, Inc.
University of Maryland Bedminster One
College Park, MD 20742 135 Route 202/206 South
Bedminster, NJ 07921
USA USA
Phone: +1 301 405-6630 Phone: +1 908 947-7033
Email: corson@isr.umd.edu Email: corson@flarion.com
Joseph Macker Joseph Macker
Information Technology Division Information Technology Division
Naval Research Laboratory Naval Research Laboratory
Washington, DC 20375 Washington, DC 20375
USA USA
Phone: +1 202 767-2001 Phone: +1 202 767-2001
Email: macker@itd.nrl.navy.mil Email: macker@itd.nrl.navy.mil
Authors' Addresses Authors' Addresses
Questions about this document can also be directed to the authors: Questions about this document can also be directed to the authors:
Mario Gerla Mario Gerla
3732F Boelter Hall 3732F Boelter Hall
Computer Science Department Computer Science Department
skipping to change at page 18, line 45 skipping to change at page 19, line 20
Computer Science Department Computer Science Department
University of California University of California
Los Angeles, CA 90095-1596 Los Angeles, CA 90095-1596
USA USA
Phone: +1 310 825-1888 Phone: +1 310 825-1888
Fax: +1 310 825-7578 Fax: +1 310 825-7578
Email: mary@cs.ucla.edu Email: mary@cs.ucla.edu
Guangyu Pei Guangyu Pei
Rockwell Science Center Rockwell Scientific Company
1049 Camino Dos Rios 1049 Camino Dos Rios
P.O. Box 1085 P.O. Box 1085
Thousand Oaks, CA 91358-0085 Thousand Oaks, CA 91358-0085
USA USA
Phone: +1 805 373-4639 Phone: +1 805 373-4639
Fax: +1 805 373-4383 Fax: +1 805 373-4383
Email: gpei@rsc.rockwell.com Email: gpei@rwsc.com
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