Spanakis Manolis CS539 Computer Science Department 16/03/2005

1
Spanakis ManolisCS539Computer Science
Department16/03/2005
Mobile Ad-hoc NETworks Routing Protocols
2
The Simpson's
Be home early, Homer.
Hmm, A MANET makes sense.
Yes. What are you doing, Nelson?
Dad, you can use Nelson if I am too fast.
Hi, Marge. I miss you.
I can hear u, Lisa.
Can u hear me?
3
IETF MANET Working Group

• The Mobile Ad-hoc Networking (manet) Working
  Group is a chartered working group within the
  Internet Engineering Task Force (IETF) to
  investigate and develop candidate standard
  Internet routing support for mobile, wireless IP
  autonomous segments.
• The charter and official IETF Home Page for manet
  are found at http//www.ietf.org/html.charters/m
  anet-charter.html

4
Description of Working Group

• Purpose of MANET working group
• standardize IP routing protocol functionality
  suitable for wireless routing application
  withinboth static and dynamic topologies with
  increased dynamics due to nodemotion or other
  factors.
• Approaches are intended to be
• relatively lightweight in nature
• suitable for multiple hardware and wireless
  environments, and address scenarios
• MANETs are deployed at the edges of an IP
  infrastructure
• hybrid mesh infrastructures (e.g., a mixture of
  fixed and mobile routers) should also be
  supported by MANET specifications and management
  features.

5
Description of Working Group

• Using mature components from previous work on
  experimental reactive and proactive protocols,
  the WG will develop two Standards track routing
  protocol specifications
• Reactive MANET Protocol (RMP)
• Proactive MANET Protocol (PMP)
• Both IPv4 and IPv6 will be supported.
• Routing security requirements and issues will
  also be addressed.

6
Goals and Milestones
7
Current Status

• Internet-Drafts
• The Dynamic Source Routing Protocol for Mobile Ad
  Hoc Networks (DSR) (264775 bytes)
• Dynamic MANET On-demand Routing Protocol (DYMO)
  (48518 bytes)
• Request For Comments
• Mobile Ad hoc Networking (MANET) Routing
  Protocol Performance Issues and Evaluation
  Considerations (RFC 2501) (28912 bytes)
• Ad Hoc On Demand Distance Vector (AODV) Routing
  (RFC 3561) (90356 bytes)
• Optimized Link State Routing Protocol (RFC 3626)
  (161265 bytes)
• Topology Dissemination Based on Reverse-Path
  Forwarding (TBRPF) (RFC 3684) (107963 bytes)

8
Mobile Ad Hoc Networks (MANET)

• Networks formed by a collection of wireless
  mobile hosts
• Without any pre-existing infrastructure or the
  aid of any centralized administration
• Network characteristics change over time
• Routes between nodes may potentially contain
  multiple hops
• Number of hosts in the network

9
Mobile Ad Hoc Networks (MANET)

• May need to traverse multiple links to reach a
  destination

10
Mobile Ad Hoc Networks (MANET)

• Mobility causes route changes

11
Why Ad Hoc Networks ?

• Ease and Speed in deployment
• Decreased dependence on infrastructure
• Only possible solution to interconnect a group of
  nodes
• Many Commercial Products available today

12
MANET Applications

• Body Area Networking
• body sensors network,
• Personal area Networking
• cell phone, laptop, ear phone, wrist watch
• Emergency operations
• search-and-rescue (earthquakes, boats,
  airplanes)
• policing and fire fighting

• Military environments
• soldiers, tanks, planes, battlefield
• Civilian environments
• taxi cab network
• meeting rooms
• sports stadiums
• boats, small aircraft

13
Variations

• Traffic characteristics may differ in different
  ad hoc networks
• bit rate, reliability requirements, unicast,
  multicast, host-based addressing, content-based
  addressing, capability-based addressing
• Ad-hoc networks may co-exist and co-operate with
  infrastructure-based networks
• Mobility characteristics may be different
• Speed, direction of movement, pattern of movement
• Symmetric vs Asymmetric
• Nodes capabilities and responsibilities

14
Issues in Mobile Ad-hoc Networks

• Limited wireless transmission range
• Broadcast nature of the wireless medium
• Hidden terminal problem
• Packet losses due to transmission errors
• Mobility-induced route changes
• Mobility-induced packet losses
• Battery constraints
• Potentially frequent network partitions
• Ease of snooping on wireless transmissions
  (security hazard)

15

• Whats unique about a MANET ?
• Moving nodes ? ever changing topology
• Wireless links
• ? various and volatile link quality
• Pervasive (cheap) devices
• ? Power constraints
• Security
• Confidentiality, other attacks

16

• MANET Protocol Zoo
• Topology based routing
• Proactive approach, e.g., DSDV.
• Reactive approach, e.g., DSR, AODV, TORA.
• Hybrid approach, e.g., Cluster, ZRP.
• Position based routing
• Location Services
• DREAM, Quorum-based, GLS, Home zone etc.
• Forwarding Strategy
• Greedy, GPSR, RDF, Hierarchical, etc.

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Recent Research Topics

• Routing
• Better metric, higher throughput
• A high-throughput path metric for multi-hop
  wireless routing. MobiCom 03.
• Transport Layer
• TCP performance throughput, fairness, etc.
• Enhancing TCP fairness in ad-hoc networks using
  neighborhood RED. MobiCom 03.
• Improving fairness among TCP flows crossing
  wireless ad-hoc and wired networks. MobiHoc 03.
• MAC Layer
• MAC protocol for directional antennas
• A MAC protocol for full exploitation of
  directional antennas in ad-hoc wireless networks.
  MobiHoc 03.

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Recent Research Topics (cont.)

• Security
• Reliable routing against malicious nodes
• Ariadne A secure on-demand routing protocol for
  ad-hoc networks. MobiCom 2002.
• Power Management
• Power saving and power control
• Asynchronous wakeup for ad hoc networks. MobiHoc
  2003.
• A power control MAC protocol for ad hoc network.
  MobiCom 2002.

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Ad-hoc p2p a Comparison

• P2P is based on an IP network
• Ad-hoc is based on a mobile radio network
• Mobile Ad-hoc and Peer-to-Peer Networks hold many
  similarities concerning their
• routing algorithms and
• network management principles
• Both have to provide networking functionalities
  in a completely unmanaged and decentralized
  environment
• Ie. To determine how queries (packets) are guided
  through the network

20
Ad-hoc p2p a Comparison
21
Ad-hoc p2p - Differences
22
Ad-hoc p2p - Similarities
23
Routing in Mobile Ad-Hoc Networks
24
Routing Overview

• Mobile wireless hosts
• Only subset within range at given time
• Want to communicate with any other node

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Routing Overview

• Network with nodes, edges
• Goal transfer message from one node to another
• Which is the best path?
• Who decides - source or intermediate nodes?

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Which path?

• Generally try to optimize one of the following
• Shortest path (fewest hops)
• Shortest time (lowest latency)
• Shortest weighted path (utilize available
  bandwidth, battery)

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Who determines route?

• Source (path) routing Like airline travel
• Source specifies entire route
• Intermediate nodes just forward to specified next
  hop
• Destination (hop-by-hop) routing Like postal
  service
• Source specifies only destination in message
  header
• Intermediate nodes look at destination in header,
  consult internal tables to determine appropriate
  next hop

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MANET Routing

• Standardization effort led by IETF Mobile Ad-hoc
  Networks (MANET) task group
• http//www.ietf.org/html.charters/manet-charter.ht
  ml
• 9 routing protocols in draft stage, 4 drafts
  dealing with broadcast / multicast / flow issues
• Other protocols being researched
• utilize geographic / GPS info, ant-based
  techniques, etc.

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MANET Routing Properties

• Qualitive Properties
• Distributed operation
• Loop Freedom
• Demand Based Operation
• Security
• Sleep period operation
• Unidirectional link support

• Quantitative Properties
• End-to-End data throughput
• Delays
• Route Acquisition time
• Out of order delivery (percentage)
• Efficiency

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MANET Routing Properties

• No distinction between routers and end nodes
  all nodes participate in routing
• No external network setup self-configuring
• Efficient when network topology is dynamic
  (frequent network changes links break, nodes
  come and go)
• Self Starting
• Adapt to network conditions

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Why is Routing in MANET different ?

• Host mobility
• link failure/repair due to mobility may have
  different characteristics than those due to other
  causes
• Rate of link failure/repair may be high when
  nodes move fast
• New performance criteria are used
• route stability despite mobility
• energy consumption
• host position
• Dynamic Solution much more difficult to be
  deployed

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Routing Protocols

• No Routing
• Plain Flooding (PF)
• Proactive protocols determine routes independent
  of traffic pattern, traditional link-state and
  distance-vector routing protocols are proactive.
• Destination Sequence Distance Vector (DSDV)
• Link State Routing
• Reactive protocols discover routes and maintain
  them only if needed.
• Dynamic Source Routing (DSR)
• Ad-hoc On-Demand Distance Vector Routing (AODV)
• Hybrid protocols
• Zone Based Routing (ZBR)

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Trade-Offs

• Latency of route discovery
• Proactive protocols may have lower latency since
  routes are maintained at all times
• Reactive protocols may have higher latency
  because a route from X to Y will be found only
  when X attempts to send to Y
• Overhead of route discovery/maintenance
• Reactive protocols may have lower overhead since
  routes are determined only if needed
• Proactive protocols can (but not necessarily)
  result in higher overhead due to continuous route
  updating
• Which approach achieves a better trade-off
  depends on the traffic and mobility patterns

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Routing Protocols
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Flooding for Data Delivery
Y
Z
S
E
F
B
C
M
L
J
A
G
H
R
K
I
N
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Flooding for Data Delivery
Y
Broadcast transmission
Z
S
E
F
B
C
M
L
J
A
G
H
R
K
I
N
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Flooding for Data Delivery
Y
Z
S
E
F
B
C
M
L
J
A
G
H
R
K
I
N
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Flooding for Data Delivery
Y
Z
S
E
F
B
C
M
L
J
A
G
H
R
K
I
N
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Flooding for Data Delivery
Y
Z
S
E
F
B
C
M
L
J
A
G
H
R
K
I
N

• Nodes J and K both broadcast packet P to node R
• Since nodes J and K are hidden from each other,
  their
• transmissions may collide
• gt Packet P may not be delivered to node
  R at all,
• despite the use of flooding

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Flooding for Data Delivery
Y
Z
S
E
F
B
C
M
L
J
A
G
H
R
K
I
N
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Flooding for Data Delivery
Y
Z
S
E
F
B
C
M
L
J
A
G
H
R
K
I
N

• Flooding completed
• Nodes unreachable from S do not receive packet
• Flooding may deliver packets to too many nodes
• (in the worst case, all nodes reachable from
  sender
• may receive the packet)

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Flooding for Data Delivery Advantages

• Simplicity
• Efficient than other protocols when rate of
  information transmission is low enough
• overhead of explicit route discovery/maintenance
  incurred is higher
• small data packets
• infrequent transfers
• many topology changes occur between consecutive
  packet transmissions
• Potentially higher reliability of data delivery

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Flooding for Data Delivery Disadvantages

• Very high overhead
• Data packets may be delivered to too many nodes
  who do not need to receive them
• Lower reliability of data delivery
• If Broadcasting is unreliable (ie. 802.11 MAC)

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Flooding of Control Packets

• Many protocols perform (potentially limited)
  flooding of control packets, instead of data
  packets
• The control packets are used to discover routes
• Discovered routes are subsequently used to send
  data packet(s)

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Dynamic Source Routing

• Draft RFC at http//www.ietf.org/internet-drafts/d
  raft-ietf-manet-dsr-07.txt
• Source routing entire path to destination
  supplied by source in packet header
• Utilizes extension header following standard IP
  header to carry protocol information (route to
  destination, etc.)

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DSR Protocol Activities

• Route discovery
• Undertaken when source needs a route to a
  destination
• Route maintenance
• Detect network topology changes
• Used when link breaks, rendering specified path
  unusable
• Routing (easy!)

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Details

• Intermediate nodes cache overheard routes
• Eavesdrop on routes contained in headers
• Reduces need for route discovery
• Intermediate node may return Route Reply to
  source if it already has a path stored
• Encourages expanding ring search for route

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Details (cont.)

• Destination may need to discover route to source
  to deliver Route Reply
• piggyback Route Reply onto new Route Request to
  prevent infinite loop
• Route Request duplicate rejection
• Source includes identification number in Route
  Request
• Partial path inspected for loop

49
Route Maintenance

• Used when link breakage occurs
• Link breakage may be detected using link-layer
  ACKs, passive ACKs, DSR ACK request
• Route Error message sent to source of message
  being forwarded when break detected
• Intermediate nodes eavesdrop, adjust cached
  routes
• Source deletes route tries another if one
  cached, or issues new Route Request
• Piggybacks Route Error on new Route Request to
  clear intermediate nodes route caches, prevent
  return of invalid route

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Issues

• Scalability
• Discovery messages broadcast throughout network
• Broadcast / Multicast
• Use Route Request packets with data included
• Duplicate rejection mechanisms prevent storms
• Multicast treated as broadcast no multicast-tree
  operation defined
• Scalability issues

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Route Discovery in DSR
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Represents a node that has received RREQ for D
from S
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Route Discovery in DSR
Y
Broadcast transmission
Z
S
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Represents transmission of RREQ
X,Y Represents list of identifiers appended
to RREQ
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Route Discovery in DSR
Y
Z
S
S,E
E
F
B
C
M
L
J
A
G
S,C
H
D
K
I
N

• Node H receives packet RREQ from two neighbors
• potential for collision

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Route Discovery in DSR
Y
Z
S
E
F
S,E,F
B
C
M
L
J
A
G
H
D
K
S,C,G
I
N

• Node C receives RREQ from G and H, but does not
  forward
• it again, because node C has already forwarded
  RREQ once

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Route Discovery in DSR
Y
Z
S
E
F
S,E,F,J
B
C
M
L
J
A
G
H
D
K
I
N
S,C,G,K

• Nodes J and K both broadcast RREQ to node D
• Since nodes J and K are hidden from each other,
  their
• transmissions may collide

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Route Discovery in DSR
Y
Z
S
E
S,E,F,J,M
F
B
C
M
L
J
A
G
H
D
K
I
N

• Node D does not forward RREQ, because node D
• is the intended target of the route discovery

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Route Reply in DSR

• Route Reply can be sent by reversing the route in
  Route Request (RREQ) only if links are guaranteed
  to be bi-directional
• To ensure this, RREQ should be forwarded only if
  it received on a link that is known to be
  bi-directional
• If unidirectional (asymmetric) links are allowed,
  then RREP may need a route discovery for S from
  node D
• Unless node D already knows a route to node S
• If a route discovery is initiated by D for a
  route to S, then the Route Reply is piggybacked
  on the Route Request from D.
• If IEEE 802.11 MAC is used to send data, then
  links have to be bi-directional (since Ack is
  used)

58
Dynamic Source Routing (DSR)

• Node S on receiving RREP, caches the route
  included in the RREP
• When node S sends a data packet to D, the entire
  route is included in the packet header
• hence the name source routing
• Intermediate nodes use the source route included
  in a packet to determine to whom a packet should
  be forwarded

59
Route Reply in DSR
Y
Z
S
RREP S,E,F,J,D
E
F
B
C
M
L
J
A
G
H
D
K
I
N

• Node D sends back a Reply (RREP) to S with the
  pathNOTE If node D does not know a rout back to
  S it might be necessary to start its own rout
  discovery to S.

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Data Delivery in DSR
Y
Z
DATA S,E,F,J,D
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Packet header size grows with route length
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DSR Advantages

• Routes maintained only between nodes who need to
  communicate
• reduces overhead of route maintenance
• Route caching can further reduce route discovery
  overhead
• A single route discovery may yield many routes to
  the destination, due to intermediate nodes
  replying from local caches

62
DSR Disadvantages

• Packet header size grows with route length due to
  source routing
• Flood of route requests may potentially reach all
  nodes in the network
• Care must be taken to avoid collisions between
  route requests propagated by neighboring nodes
• insertion of random delays before forwarding RREQ

63
DSR Disadvantages

• An intermediate node may send Route Reply using a
  stale cached route, thus polluting other caches
• Increased contention if too many route replies
  come back due to nodes replying using their local
  cache
• Route Reply Storm problem
• Reply storm may be eased by preventing a node
  from sending RREP if it hears another RREP with a
  shorter route

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Ad-hoc On-demand Distance Vector Routing

• Draft RFC at http//www.ietf.org/internet-drafts/d
  raft-ietf-manet-aodv-10.txt
• Hop-by-hop protocol intermediate nodes use
  lookup table to determine next hop based on
  destination
• Utilizes only standard IP header

65
AODV Protocol Activities

• Route discovery
• Undertaken whenever a node needs a next hop to
  forward a packet to a destination
• Route maintenance
• Used when link breaks, rendering next hop
  unusable
• Routing (easy!)

66
Route Discovery

• Route Request
• Source broadcasts Route Request (RREQ) message
  for specified destination
• Intermediate node Forward message toward
  destination
• Route Reply
• Destination unicasts Route Reply msg to source
• Intermediate node create next-hop entry for
  destination and forward the reply
• If source receives multiple replies, uses one
  with lowest hop count

67
Route Maintenance

• Used when link breakage occurs
• Detecting node may attempt local repair
• Route Error (RERR) message generated
• Contains list of unreachable destinations
• Sent to precursors neighbors who recently sent
  packet which was forwarded over broken link
• Propagated recursively

68
Route Requests in AODV
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
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Route Requests in AODV
Y
Broadcast transmission
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
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Route Requests in AODV
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
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Reverse Path Setup in AODV
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N

• Node C receives RREQ from G and H, but does not
  forward
• it again, because node C has already forwarded
  RREQ once

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Reverse Path Setup in AODV
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
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Reverse Path Setup in AODV
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N

• Node D does not forward RREQ, because node D
• is the intended target of the RREQ

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Route Reply in AODV
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Represents links on path taken by RREP
75
Route Reply in AODV

• An intermediate node (not the destination) may
  also send a Route Reply (RREP) provided that it
  knows a more recent path than the one previously
  known to sender S
• To determine whether the path known to an
  intermediate node is more recent, destination
  sequence numbers are used
• The likelihood that an intermediate node will
  send a Route Reply when using AODV is not as high
  as DSR

76
Forward Path Setup in AODV
Y
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N
Forward links are setup when RREP travels
along the reverse path Represents a link on the
forward path
77
Data Delivery in AODV
Y
DATA
Z
S
E
F
B
C
M
L
J
A
G
H
D
K
I
N

• Routing table entries used to forward data
  packet.
• Route is not included in packet header.

78
Why Sequence Numbers in AODV

• To avoid using old/broken routes
• To determine which route is newer
• To prevent formation of loops
• Assume that A does not know about failure of link
  C-D because RERR sent by C is lost
• Now C performs a route discovery for D. Node A
  receives the RREQ (say, via path C-E-A)
• Node A will reply since A knows a route to D via
  node B
• Results in a loop (for instance, C-E-A-B-C )

79
Summary AODV

• Routes need not be included in packet headers
• Nodes maintain routing tables containing entries
  only for routes that are in active use
• At most one next-hop per destination maintained
  at each node
• DSR may maintain several routes for a single
  destination
• Unused routes expire even if topology does not
  change

80
Hybrid Protocols
81
Zone Routing Protocol (ZRP)

• Zone routing protocol combines
• Proactive protocol which pro-actively updates
  network state and maintains route regardless of
  whether any data traffic exists or not
• Reactive protocol which only determines route to
  a destination if there is some data to be sent to
  the destination

82
ZRP Example withZone Radius d 2
S performs route discovery for D
S
D
F
Denotes route request
83
ZRP Example with d 2
S performs route discovery for D
S
D
F
E knows route from E to D, so route request need
not be forwarded to D from E
Denotes route reply
84
ZRP Example with d 2
S performs route discovery for D
S
D
F
Denotes route taken by Data
85
Implementation Issues
86
Implementation IssuesWhere to Implement Ad Hoc
Routing

• Link layer
• Network layer
• Application layer

87
Issues inMobile Ad Hoc Networking

• Issues other than routing have received much less
  attention so far
• Other interesting problems
• Address assignment problem
• MAC protocols
• Improving interaction between protocol layers
• Distributed algorithms for MANET
• QoS issues
• Applications for MANET
• Algorithms for dynamic networks
• Security
• Privacy, Authentication, Authorization, Data
  integrity
• Ad-Hoc Sensor networks
• Addressing based on data (or function) instead of
  name, send this packet to a temperature sensor

88
Related Standards Activities
89
Internet Engineering Task Force (IETF) Activities

• IETF manet (Mobile Ad-hoc Networks) working group
• http//www.ietf.org/html.charters/manet-charter.ht
  ml
• IETF mobileip (IP Routing for Wireless/Mobile
  Hosts) working group
• http//www.ietf.org/html.charters/mobileip-charter
  .html
• IETF PILC (Performance Implications of Link
  Characteristics) working group
• http//www.ietf.org/html.charters/pilc-charter.htm
  l
• http//pilc.grc.nasa.gov

90
Related Standards Activities

• BlueTooth
• http//www.bluetooth.com
• HomeRF
• http//www.homerf.org
• IEEE 802.11
• http//grouper.ieee.org/groups/802/11/
• Hiperlan/2
• http//www.etsi.org/technicalactiv/hiperlan2.htm

91
DYMO

• Dynamic MANET On-demand Routing Protocol (DYMO)
• Ian Chakeres
• Elizabeth Belding-Royer
• Charlie Perkins
• The Dynamic MANET On-demand (DYMO) routing
• protocol is intended for use by mobile nodes in
• wireless multihop networks. It offers quick
• adaptation to dynamic conditions, low processing
• and memory overhead, low network utilization, and
  
• determines unicast routes between nodes within
  the
• network.

92

• The Dynamic MANET On-demand (DYMO) routing
  protocol enables dynamic, reactive, multihop
  routing between participating nodes wishing to
  communicate. The basic operations of the protocol
  are route discovery and management. During route
  discovery the originating node causes
  dissemination of a Routing Element (RE)
  throughout the network to find the target node.
  During dissemination each intermediate node
  creates a route to the originating node. When the
  target node receives the RE it responds with RE
  unicast toward originating node. During
  propagation each node creates a route to the
  target node. When the originating node is reached
  routes have been established between the
  originating node and the target node in both
  directions. In order to react quickly to changes
  in the network topology nodes should maintain
  their routes and monitor their links. When a
  packet is received for a route that is no longer
  available the source of the packet should be
  notified. A Route Error (RERR) is sent to the
  packet source to indicate the current route is
  broken. Once the source receives the RERR, it
  will re-initiate route discovery if it still has
  packets to deliver. In order to enable extension
  of the base specification, DYMO defines the
  handling of unsupported extensions. By defining
  default handling, future extensions are handled
  in a predetermined understood fashion. DYMO uses
  sequence numbers to ensure loop freedom 3. All
  DYMO packets are transmitted via UDP on port TBD.
  Chakeres, et al. Expires July 5, 2005

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Goals

• Create a unicast route
• Simple, small
• Easy to implement
• Extendable
• Enhancements optimizations
• IPv4 and IPv6
• Basic internet connectivity
• Use what we know

94
Route Discovery

• Routing Element (RE)
• Simple, common processing
• REBlock
• RREQ gt RE A1 MANETcast
• RREP gt RE A0 Unicast hop-by-hop
• Path accumulation
• Optional accumulation, processing and
  transmission

95
Route Maintenance

• Avoid expiring good routes
• Update reverse route lifetime on data reception
• Update forward route lifetime on data
  transmission
• Inform sources of broken routes quickly
• Active links must be monitored
• Several mechanisms available
• Route Error (RERR)
• Optional additional invalid routes

96
DYMO Short Term Goals

• dymo-00 available
• feedback already received (more expected)
• dymo-01soon
• MANET list discussion
• Simple, quick implementation
• Looking for DYMO implementers
• Simulators and various OS
• Please contact us