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Spanakis ManolisCS539
Computer Science Department
16/03/2005
Mobile Ad-hoc NETworks Mobile Ad-hoc NETworks Routing ProtocolsRouting Protocols
Hmm, A MANETmakes sense.
Dad, you can useNelson if I am
too fast.Hi, Marge.I miss you.
I can hear u, Lisa.Can u hear me?
Yes. What areyou doing,
Nelson?
Be home early,Homer.
The Simpson'sThe Simpson's
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/manet-charter.html
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.
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.
Goals and Milestones:Done Post as an informational Internet-Drafts a discussion of mobile ad-hoc networking and issues.
Done Agenda bashing, discussion of charter and of mobile ad hoc networking draft.
Done Discuss proposed protocols and issues. Redefine charter.
Done Publish Informational RFC on manet design considerations
Done Review the WG Charter and update
Done Submit AODV specification to IESG for publication as Experimental RFC
Done Develop I-D for potential common manet encapsulation protocol approach
Done Submit initial I-D(s) of candidate proposed routing protocols and design frameworks
Done Promote implementation, revision, and testing of initial proposed I-D(s)
Done Explore basic performance and implementation issues of initial approaches
Done Explore proposed proactive protocol design commonalities
Done Submit DSR specification to IESG for publication as Experimental RFC
Done Submit OLSR specification to IESG for publication as Experimental RFC
Done Submit TBRPF specification to IESG for publication as Experimental RFC
Done Develop a further focused problem statement and address an approach for a common engineering work effort
Done Reevaluate the WG's potential based on the problem statement consensus
Mar 05 Submit initial ID of RMP for WG review
Mar 05 Submit initial ID of PMP for WG review
Mar 05 Submit inital ID of generalized MANET flooding approach
Jun 05 Revise WG documents and review
Nov 05 Document initial implementation progress and experience Revise documents based upon implementation experience
Feb 06 Submit RMP specification and supporting documentation to IESG for publications as Proposed Standard
Feb 06 Submit PMP specification and supporting documentation to IESG for publications as Proposed Standard
Feb 06 Submit MANET flooding specification to IESG for publication as Experimental Standard
Mar 06 Review and update milestones
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 Protoc
ol 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)
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 timeRoutes between nodes may potentially contain
multiple hopsNumber of hosts in the network
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
MANET Applications
Body Area Networkingbody sensors network,
Personal area Networkingcell phone, laptop, ear
phone, wrist watch Emergency operations
search-and-rescue (earthquakes, boats, airplanes…)
policing and fire fighting
Military environmentssoldiers, tanks, planes,
battlefield Civilian environments
taxi cab networkmeeting roomssports stadiumsboats, small aircraft
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
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)
What’s 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
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.
Recent Research TopicsRecent Research Topics
RoutingBetter metric, higher throughputA high-throughput path metric for multi-hop wireless routing. MobiCom 03.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.Enhancing TCP fairness in ad-hoc networks using neighborhood RED. MobiCom 03.Improving fairness among TCP flows crossing wireless ad-hoc and wired networks. Improving fairness among TCP flows crossing wireless ad-hoc and wired networks.
MobiHoc 03.MobiHoc 03.
MAC LayerMAC protocol for directional antennasA MAC protocol for full exploitation of directional antennas in ad-hoc wireless networks. A MAC protocol for full exploitation of directional antennas in ad-hoc wireless networks.
MobiHoc 03.MobiHoc 03.
Recent Research Topics (cont.)Recent Research Topics (cont.)
Security Reliable routing against malicious nodesAriadne: A secure on-demand routing protocol for ad-hoc networks. MobiCom 2002.Ariadne: A secure on-demand routing protocol for ad-hoc networks. MobiCom 2002.
Power ManagementPower saving and power controlAsynchronous wakeup for ad hoc networks. MobiHoc 2003. Asynchronous wakeup for ad hoc networks. MobiHoc 2003.
A power control MAC protocol for ad hoc network. MobiCom 2002.A power control MAC protocol for ad hoc network. MobiCom 2002.
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 andnetwork management principles
Both have to provide networking functionalities in a completely unmanaged and decentralized environmentIe. To determine how queries (packets) are guided
through the network
Routing Overview
Mobile wireless hostsOnly subset within range at given timeWant to communicate with any other node
Routing Overview
Network with nodes, edges
Goal: transfer message from one node to anotherWhich is the “best” path?Who decides - source or
intermediate nodes?
msg
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)
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
MANET Routing
Standardization effort led by IETF Mobile Ad-hoc Networks (MANET) task grouphttp://www.ietf.org/html.charters/manet-cha
rter.html9 routing protocols in draft stage, 4 drafts
dealing with broadcast / multicast / flow issues
Other protocols being researchedutilize geographic / GPS info, ant-based
techniques, etc.
MANET Routing Properties
Qualitive PropertiesDistributed operation Loop FreedomDemand Based
OperationSecurity Sleep period operationUnidirectional link
support
Quantitative PropertiesEnd-to-End data
throughputDelaysRoute Acquisition timeOut of order delivery
(percentage)Efficiency
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
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 mobilityenergy consumptionhost position
Dynamic Solution much more difficult to be deployed
Routing Protocols
No Routing Plain Flooding (PF)
Proactive protocols: determine routes independent of traffic determine routes independent of traffic pattern, traditional link-state and distance-vector routing pattern, traditional link-state and distance-vector routing protocols are proactiveprotocols are proactive.. Destination Sequence Distance Vector (DSDV) Link State Routing
Reactive protocols: discover routes and maintain them only discover routes and maintain them only if needed.if needed. Dynamic Source Routing (DSR) Ad-hoc On-Demand Distance Vector Routing (AODV)
Hybrid protocols Zone Based Routing (ZBR)
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
Flooding for Data Delivery
B
A
S E
F
H
JC
G
IK
Z
Y
M
• 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 Packet P may not be delivered to node R at all, despite the use of flooding
N
L
R
Flooding for Data Delivery
B
A
S E
F
H
JC
G
IK
• 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)
Z
Y
M
N
L
R
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 highersmall data packets infrequent transfersmany topology changes occur between
consecutive packet transmissions Potentially higher reliability of data delivery
Flooding for Data Delivery: Disadvantages
Very high overheadData packets may be delivered to too many
nodes who do not need to receive them
Lower reliability of data deliveryIf Broadcasting is unreliable (ie. 802.11 MAC)
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)
Dynamic Source Routing
Draft RFC at http://www.ietf.org/internet-drafts/draft-ietf-manet-dsr-07.txt
Source routing: entire path to destination supplied by source in packet headerUtilizes extension header following
standard IP header to carry protocol information (route to destination, etc.)
DSR Protocol Activities
Route discoveryUndertaken when source needs a route
to a destinationRoute maintenance
Detect network topology changesUsed when link breaks, rendering
specified path unusableRouting (easy!)
Details
Intermediate nodes cache overheard routes “Eavesdrop” on routes contained in headersReduces need for route discovery
Intermediate node may return Route Reply to source if it already has a path storedEncourages “expanding ring” search for route
Details (cont.)
Destination may need to discover route to source to deliver Route Replypiggyback Route Reply onto new Route Request
to prevent “infinite loop”
Route Request duplicate rejection:Source includes identification number in Route
RequestPartial path inspected for “loop”
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 RequestPiggybacks Route Error on new Route Request to
clear intermediate nodes’ route caches, prevent return of invalid route
Issues
ScalabilityDiscovery messages broadcast throughout
network Broadcast / Multicast
Use Route Request packets with data includedDuplicate rejection mechanisms prevent “storms”
Multicast treated as broadcast; no multicast-tree operation definedScalability issues
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
Represents a node that has received RREQ for D from S
M
N
L
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
Represents transmission of RREQ
Z
YBroadcast transmission
M
N
L
[S]
[X,Y] Represents list of identifiers appended to RREQ
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
• Node H receives packet RREQ from two neighbors: potential for collision
Z
Y
M
N
L
[S,E]
[S,C]
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
• Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once
Z
Y
M
N
L
[S,C,G]
[S,E,F]
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
• Nodes J and K both broadcast RREQ to node D• Since nodes J and K are hidden from each other, their transmissions may collide
N
L
[S,C,G,K]
[S,E,F,J]
Route Discovery in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
• Node D does not forward RREQ, because node D is the intended targetintended target of the route discovery
M
N
L
[S,E,F,J,M]
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)
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 headerhence the name source routing
Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded
Route Reply in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
N
L
RREP [S,E,F,J,D]
• 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 it’s own rout discovery to S.
Data Delivery in DSR
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
N
L
DATA [S,E,F,J,D]
Packet header size grows with route length
DSR: Advantages
Routes maintained only between nodes who need to communicatereduces 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
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
DSR: Disadvantages
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 cacheRoute Reply Storm problemReply storm may be eased by preventing a
node from sending RREP if it hears another RREP with a shorter route
Ad-hoc On-demand Distance Vector Routing
Draft RFC at http://www.ietf.org/internet-drafts/draft-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
AODV Protocol Activities
Route discoveryUndertaken whenever a node needs a
“next hop” to forward a packet to a destination
Route maintenanceUsed when link breaks, rendering next
hop unusableRouting (easy!)
Route Discovery
Route Request:Source broadcasts Route Request (RREQ)
message for specified destinationIntermediate node Forward message toward
destination Route Reply
Destination unicasts Route Reply msg to sourceIntermediate node create next-hop entry for
destination and forward the replyIf source receives multiple replies, uses one
with lowest hop count
Route Maintenance
Used when link breakage occurs Detecting node may attempt “local repair” Route Error (RERR) message generated
Contains list of unreachable destinationsSent to “precursors”: neighbors who recently
sent packet which was forwarded over broken linkPropagated recursively
Reverse Path Setup in AODV
B
A
S E
F
H
J
D
C
G
IK
• Node C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once
Z
Y
M
N
L
Reverse Path Setup in AODV
B
A
S E
F
H
J
D
C
G
IK
Z
Y
• Node D does not forward RREQ, because node D is the intended target of the RREQ
M
N
L
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
Forward Path Setup in AODV
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
N
L
Forward links are setup when RREP travels alongthe reverse path
Represents a link on the forward path
Data Delivery in AODV
B
A
S E
F
H
J
D
C
G
IK
Z
Y
M
N
L
• Routing table entries used to forward data packet.
• Route is Route is notnot included in packet header. included in packet header.
DATA
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 )
A B C D
E
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 nodeDSR may maintain several routes for a single
destination Unused routes expire even if topology does not
change
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
ZRP: Example withZone Radius = d = 2
SCA
EF
B
D
S performs routediscovery for D
Denotes route request
ZRP: Example with d = 2
SCA
EF
B
D
S performs routediscovery for D
Denotes route reply
E knows route from E to D, so route request need not beforwarded to D from E
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”
Internet Engineering Task Force (IETF) Activities
IETF manet (Mobile Ad-hoc Networks) working grouphttp://www.ietf.org/html.charters/manet-charter.html
IETF mobileip (IP Routing for Wireless/Mobile Hosts) working group http://www.ietf.org/html.charters/mobileip-charter.ht
ml IETF PILC (Performance Implications of Link
Characteristics) working grouphttp://www.ietf.org/html.charters/pilc-charter.htmlhttp://pilc.grc.nasa.gov
Related Standards Activities
BlueToothhttp://www.bluetooth.com
HomeRFhttp://www.homerf.org
IEEE 802.11http://grouper.ieee.org/groups/802/11/
Hiperlan/2http://www.etsi.org/technicalactiv/hiperlan2.htm
DYMO
Dynamic MANET On-demand Routing Protocol (DYMO) Ian Chakeres Elizabeth Belding-Royer Charlie Perkins
The Dynamic MANET On-demand (DYMO) routingprotocol 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.
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
Goals
Create a unicast route Simple, small
Easy to implement Extendable
Enhancements & optimizations IPv4 and IPv6 Basic internet connectivity Use what we know
Route Discovery
Routing Element (RE)Simple, common processingREBlock
RREQ => RE A=1 MANETcast RREP => RE A=0 Unicast hop-by-hop Path accumulation
Optional accumulation, processing and transmission
Route Maintenance
Avoid expiring good routesUpdate reverse route lifetime on data
receptionUpdate forward route lifetime on data
transmission Inform sources of broken routes quickly
Active links must be monitoredSeveral mechanisms available
Route Error (RERR) Optional additional invalid routes