Title: Spanakis Manolis CS539 Computer Science Department 16/03/2005
1Spanakis ManolisCS539Computer Science
Department16/03/2005
Mobile Ad-hoc NETworks Routing Protocols
2The 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?
3IETF 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
4Description 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.
5Description 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.
6Goals and Milestones
7Current 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)
8Mobile 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
9Mobile Ad Hoc Networks (MANET)
- May need to traverse multiple links to reach a
destination
10Mobile Ad Hoc Networks (MANET)
- Mobility causes route changes
11Why 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
12MANET 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
13Variations
- 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
14Issues 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.
17Recent 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.
18Recent 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.
19Ad-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
20Ad-hoc p2p a Comparison
21Ad-hoc p2p - Differences
22Ad-hoc p2p - Similarities
23Routing in Mobile Ad-Hoc Networks
24Routing Overview
- Mobile wireless hosts
- Only subset within range at given time
- Want to communicate with any other node
25Routing Overview
- Network with nodes, edges
- Goal transfer message from one node to another
- Which is the best path?
- Who decides - source or intermediate nodes?
26Which path?
- Generally try to optimize one of the following
- Shortest path (fewest hops)
- Shortest time (lowest latency)
- Shortest weighted path (utilize available
bandwidth, battery)
27Who 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
28MANET 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.
29MANET 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
30MANET 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
31Why 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
32Routing 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)
33Trade-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
34Routing Protocols
35Flooding for Data Delivery
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36Flooding for Data Delivery
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Broadcast transmission
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37Flooding for Data Delivery
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38Flooding for Data Delivery
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39Flooding for Data Delivery
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- 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
40Flooding for Data Delivery
Y
Z
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41Flooding for Data Delivery
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- 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)
42Flooding 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
43Flooding 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)
44Flooding 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)
45Dynamic 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.)
46DSR 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!)
47Details
- 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
48Details (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
49Route 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
50Issues
- 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
51Route Discovery in DSR
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Represents a node that has received RREQ for D
from S
52Route Discovery in DSR
Y
Broadcast transmission
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Represents transmission of RREQ
X,Y Represents list of identifiers appended
to RREQ
53Route Discovery in DSR
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- Node H receives packet RREQ from two neighbors
- potential for collision
54Route Discovery in DSR
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S,E,F
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S,C,G
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- Node C receives RREQ from G and H, but does not
forward - it again, because node C has already forwarded
RREQ once
55Route Discovery in DSR
Y
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S
E
F
S,E,F,J
B
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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
56Route Discovery in DSR
Y
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S
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S,E,F,J,M
F
B
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- Node D does not forward RREQ, because node D
- is the intended target of the route discovery
57Route 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)
58Dynamic 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
59Route Reply in DSR
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S
RREP S,E,F,J,D
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- 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.
60Data Delivery in DSR
Y
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DATA S,E,F,J,D
S
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Packet header size grows with route length
61DSR 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
62DSR 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
63DSR 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
64Ad-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
65AODV 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!)
66Route 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
67Route 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
68Route Requests in AODV
Y
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69Route Requests in AODV
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Broadcast transmission
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70Route Requests in AODV
Y
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71Reverse Path Setup in AODV
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- Node C receives RREQ from G and H, but does not
forward - it again, because node C has already forwarded
RREQ once
72Reverse Path Setup in AODV
Y
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B
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73Reverse Path Setup in AODV
Y
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- Node D does not forward RREQ, because node D
- is the intended target of the RREQ
74Route Reply in AODV
Y
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B
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A
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Represents links on path taken by RREP
75Route 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
76Forward Path Setup in AODV
Y
Z
S
E
F
B
C
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A
G
H
D
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Forward links are setup when RREP travels
along the reverse path Represents a link on the
forward path
77Data Delivery in AODV
Y
DATA
Z
S
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F
B
C
M
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J
A
G
H
D
K
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N
- Routing table entries used to forward data
packet. - Route is not included in packet header.
78Why 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 )
79Summary 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
80Hybrid Protocols
81Zone 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
82ZRP Example withZone Radius d 2
S performs route discovery for D
S
D
F
Denotes route request
83ZRP 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
84ZRP Example with d 2
S performs route discovery for D
S
D
F
Denotes route taken by Data
85Implementation Issues
86Implementation IssuesWhere to Implement Ad Hoc
Routing
- Link layer
- Network layer
- Application layer
87Issues 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
88Related Standards Activities
89Internet 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
90Related 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
91DYMO
- 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
93Goals
- Create a unicast route
- Simple, small
- Easy to implement
- Extendable
- Enhancements optimizations
- IPv4 and IPv6
- Basic internet connectivity
- Use what we know
94Route 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
95Route 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
96DYMO 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