1. UNIT-IV ROUTING PROTOCOLS Contents:
Issues in Designing a Routing Protocol for Ad-hoc Wireless Networks.
Classification of Routing Protocols
Table –Driven Routing Protocols.
On – Demand Routing Protocols.
Hybrid Routing Protocols.
Routing Protocols with Efficient Flooding Mechanisms.
Hierarchical Routing Protocols.
Power – Aware Routing Protocols.
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2. INTRODUCTION:
Routing protocols used in wired networks cannot be directly applied to ad-hoc wireless networks. Because Ad-hoc networks are
Highly dynamic topology
No infrastructure for centralized administration
Bandwidth constrained
Energy constrained
For the above reasons, we need to design new routing protocols for ad hoc networks.
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3. Issues in Designing a Routing Protocol:
Mobility:
Ad hoc is highly dynamic due to the movement of nodes
Node movement causes frequent path breaks
The path repair in wired network has slow convergence.
Bandwidth Constraint:
Wireless has less bandwidth due to the limited radio band, Less data rate and difficult to maintain topology information.
Frequent change of topology causes more overhead of topology maintenance
Error-prone shared broadcast radio channel:
Wireless links have time varying characteristics in terms of link capacity and link-error probability.
Hidden terminal problem causes packet collision.
Target: Interact with MAC layer to find better-quality link and find routes with less crowding.
Hidden and exposed terminal problems.
Resource Constraints:
Limited battery life and limited processing power
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4. Characteristics of a Routing Protocol:
The Routing protocol for ad-hoc wireless networks should have the following characteristics:
It must be fully distributed
It must be adaptive to frequent topology changes caused by the mobility of nodes.
Route computation and maintenance must involve a minimum number of nodes. Each node in the network must have quick access to routes, that is, minimum connection setup time is desired.
It must be localized, as global state maintenance involves a huge state propagation control overhead.
It must be loop-free and free from hard/old routes.
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5. Characteristics of a Routing Protocol: …Cntd
The number of packet collisions must be kept to a minimum by limiting the number of broadcasts made by each node.
It must converge to optimal routes once the network topology becomes stable. The convergence must be quick.
Optimally use scarce resource such as bandwidth, computing power, memory, and battery.
Remote parts of the network must not cause updates in the topology information maintained by this node.
Provide quality of service and support for time sensitive traffic.
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6. Classifications of Routing Protocols:
Routing protocol can be broadly classified into four categories :
Routing information update mechanism
Use of temporal information for routing
Routing topology
Utilization of specific resource
These classification is not mutually exclusive
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7. Classifications of Routing Protocols: …Cntd
Based on the Routing Information Update Mechanism
• Proactive or Table-driven routing protocols
– Maintain routing information in the routing table
– Routing information is flooded in the whole network
– Runs path-finding algorithm with the routing table
• Reactive or On-demand routing protocols
– Obtain the necessary path while required
• Hybrid routing protocols
– In the zone of given node : use table-driven
– Out of the zone of given node : use on-demand
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8. Classifications of Routing Protocols: …Cntd
Based on the Use of Temporal Information for Routing
• Using past temporal information
– Past status of the links or
– the status of links at the time of routing to make routing decision
• Using future temporal information
– Expected future status of the links to make decision
– Node lifetime is also included
Ex: remaining battery charge, prediction of location, and link availability
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9. Classifications of Routing Protocols: …Cntd
Based on the Routing Topology
• Flat topology routing protocols
– Flat addressing scheme similar to IEEE LANs
– Globally unique addressing mechanism for nodes
• Hierarchical topology routing protocols
– Logical hierarchy
– Associated addressing scheme
– May based on geographical information or hop distance
Based on the Utilization of Specific Resource
• Power-aware routing
– Minimize consumption of resource
Ex: Battery power
• Geographical information assisted routing
– Improve the routing performance
– Reduce control overhead
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10. Classifications of Routing Protocols: …Cntd
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11. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
These are table-driven protocols. These are extensions of the wired network routing protocols. They maintain the global topology information in the form of tables at every node.
These tables are updated frequently in order to maintain consistent and accurate network state information.
We consider:
Destination Sequenced Distance Vector Routing Protocol (DSDV);
Wireless Routing Protocol (WRP);
Cluster Head Gateway Switch Routing Protocol (CGSR).
Source-Tree Adaptive Routing Protocol (STAR);
Common Positives:
Low delay of route setup process: all routes are immediately available;
Common Negatives:
High bandwidth requirements: updates due to link loss leads to high control overhead;
Low scalability: control overhead is proportional to the number of nodes;
High storage requirements: whole table must be in memory.
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12. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Destination Sequenced Distance Vector Routing Protocol (DSDV):
Modification of the Bellman-Ford algorithm where each node maintains:
the shortest path to destination;
the first node on this shortest path.
This protocol is characterized by the following:
Routes to destination are readily available at each node in the Routing Table (RT).
RTs are exchanged between neighbors at regular intervals.
RTs are also exchanged when significant changes in local topology are observed by a node.
RT updates can be of two types:
Incremental updates: Take place when a node does not observe significant changes in a local topology.
Full dumps: Take place when significant changes of local topology are observed;
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13. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Destination Sequenced Distance Vector Routing Protocol (DSDV):
The reconfiguration of path used for ongoing data transfer is done as follows:
The end node of the broken link sends a table update message with:
Broken link's weight assigned to infinity.
Sequence number greater than the stored sequence number for that destination.
Each node re-sends this message to its neighbors to propagate the broken link to the network;
Even sequence number is generated by end node, odd { by all other nodes.
Note: single link break leads to the propagation of RT updates through the whole network.
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14. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Destination Sequenced Distance Vector Routing Protocol (DSDV):
Route maintenance in DSDV is performed as follows:
when a neighbor node perceives a link break (node 3):
It sets all routes through broken link to 1.
Broadcasts its routing table.
Node 5 receives update message, it informs neighbors about the shortest distance to node 6.
This information is propagated through the network and all node updates their RTs.
Node 1 may now sends their packets through route 1−3−5−6 instead of 1−3−6.
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15. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Wireless Routing Protocol (WRP):
Similar to DSDV, but it uses multiple tables for routing processes.
Differs from table maintenance and in the update procedure.
– Uses a set of tables to maintain more accurate information instead of single topology information
– Not only updates distance for transmitted neighbor but also checks the other neighbors’ distance.
• Distance Table: Contains distance and predecessor(penultimate node) node for a destination
• Routing Table: Contains shortest distance, predecessor node, successor node(next node to reach destination), and status of the path
• Link Cost Table: Cost of relaying messages through each link and number of update periods passed since the last successful update was received (for detecting link breaks)
• Message Retransmission Table: Update message that is to be retransmitted with a counter. The counter is decremented after every update message retransmission.
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16. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Wireless Routing Protocol (WRP):
Break: Detected by number of update periods missed since successful transmission:
Each update message contains a list of updates;
A node marks each node in RT that has to acknowledge update message it transmitted.
Once the counter of MRL(message Retransmission List) reaches zero:
Entries in update message for which no acknowledgement received are to be retransmitted;
Update message is deleted.
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17. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Wireless Routing Protocol (WRP):
When a node detects a link break:
It sends an update message to its neighbors with link cost set to ∞;
All affected node update their routes when they receive update message.
The node that initiated the update message sends an alternative route from its DT.
It updates its RT and sends update message to its neighbors.
Nodes update its RTs if this received route is better than they have, otherwise they discard it.
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18. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Wireless Routing Protocol(WRP):
Advantages:
– Same as DSDV
– Has faster convergence and fewer table updates
Disadvantages:
– Need large memory and greater computing power because of the multiple tables
– At high mobility, the control overhead for updating table entries is almost the same as DSDV
– Not suitable for highly dynamic and large ad hoc
network
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19. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Cluster head Gateway Switch Routing protocol:
It is characterized by the following:
Nodes are organized into clusters, each having an elected cluster-head;
Cluster head provides a coordination within its transmission range (single hop);
Token-based scheduling is used within a cluster for sharing bandwidth between nodes;
All communications pass through the cluster head;
Communication between cluster is done using the common nodes (gateways with two interfaces).
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20. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Cluster head Gateway Switch Routing protocol:
Two tables are used in CGSR:
Cluster member table containing the destination cluster head for every node;
Routing table containing the next-hop node for every destination cluster
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21. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Cluster head Gateway Switch Routing protocol:
Advantages:
–Better bandwidth utilization.
–Easy to implement priority scheduling scheme
Disadvantages:
–Increase in path length
–Instability when cluster-head are high mobility
–Battery-draining rate at cluster-head is more than a normal node.
–Frequent changes in the cluster-head = multiple path
break
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22. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Source-Tree Adaptive Routing protocol (STAR):
There are two protocols with different aims:
Least Overhead Routing Approach (LORA): Minimize control overhead irrespective of optimality.
Optimum Routing Approach (ORA): Provide optimal routes irrespective of the control overhead.
The STAR protocol operates as follows:
Each node is required to:
Send an update message to its neighbors during initialization;
Send update messages about new destinations, chances of routing loops, costs of paths.
Every node broadcasts its source-tree information:
Wireless links used by the node in its preferred path to destinations.
Every node builds its partial graph of topology based on:
Its adjacent links with neighbors, source-tree broadcasts by neighbors.
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23. Classifications of Routing Protocols: …Cntd
Proactive routing protocols:
Source-Tree Adaptive Routing protocol (STAR):
The following method is used to find paths:
if a node 1 wishes to send data to node N and does not have path in its source tree:
It sends update message to all neighbors and indicates that there is no path to N;
Neighbor that have the path, responses with update messages;
Node 1 updates its source tree and may begin transmission
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24. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
These protocols find paths to destination only when needed (on-demand) to transmit a packet.
We consider:
Dynamic Source Routing protocol (DSR);
Ad Hoc On-demand Distance Vector Routing protocol (AODV);
Temporally Ordered Algorithm (TORA)
Location Aided Routing (LAR);
Associativity-based Routing (ABR);
Signal Stability-based Adaptive Routing protocol (SSA);
These protocols have the following advantages and shortcomings:
Negatives:
High delay of route setup process: routes are established on-demand.
Low scalability: no route updates.
Low storage requirements: only needed routes are in cache.
Positives: Small control overhead: no route updates;
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25. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Dynamic Source Routing protocol (DSR):
This is a source-based routing protocol.
The difference between DSR and other on-demand routing protocols is that the other on-demand protocols periodically exchange hello packets.
Hello packets are used to inform neighbors about existence of the node.
DSR does not use hello packets.
The basic approach of this protocol is as follows:
During route contraction DSR floods a Route-Request packets in the network;
Intermediate nodes forward Route-Request if it is not redundant.
The destination node replies with Route-Reply;
The Route-Reply packet contains the path traversed/crossed by Route-Request packet;
The receiver responds only if this is a first Route-Request (not duplicate).
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26. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Dynamic Source Routing protocol (DSR):
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27. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Dynamic Source Routing protocol (DSR):
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28. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Ad-hoc On-demand Distance Vector routing protocol:
The major differences between AODV and DSR are as follows:
In DSR a data packet carries the complete path to be traversed.
In AODV nodes store the next hop information (hop-by-hop routing) for each data flow.
The Route-Request packet in AODV carries the following information:
The Source identifier (SrcID): This identifies the source;
The Destination identifier (DestID): This identifies the destination to which the route is required;
The Source Sequence Number (SrcSeqNum);
The Destination Sequence Number (DestSeqNum): indicates the freshness of the route.
The Broadcast identifier (BcastID): is used to discard multiple copies of the same Route-Request.
The Time to Live (TTL): this is used to not allow loops.
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29. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Ad hoc On-demand Distance Vector Routing protocol:
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30. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Ad hoc On-demand Distance Vector Routing protocol:
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31. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Ad hoc On-demand Distance Vector Routing protocol:
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32. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Temporally Ordered Algorithm (TORA):
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33. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Location Aided Routing (LAR):
LAR uses the location information.
LAR designates two zones for selective forwarding of control packets:
Expected Zone: This is a geographical zone in which the location of the terminal is predicted based on:
location of the terminal in the past.
mobility information of the terminal.
There is no info about previous location of the terminal the whole
network is the Expected Zone.
Request Zone: This is a geographical zone within which control packets are allowed to propagate:
this area is determined by the sender of the data packet;
control packets are forwarded by node within a Request Zone only;
if the node is not found using the first Request Zone, the size of Request Zone is increased.
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34. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Location Aided Routing (LAR):
Nodes decide whether to forward or discard packets based on two algorithms:
LAR type 1.
LAR type 2.
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35. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Location Aided Routing (LAR):
LAR type 1 algorithm works as follows:
The sender explicitly species the Request-Zone in the Route-Request packet.
The Request-Zone is the smallest rectangle that includes the source and the Expected-Zone.
When the node is in Expected-Zone, the Request-Zone is reduced to the Expected-Zone.
If the Route-Request packet is received by the node within Request-Zone, it forwards it.
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36. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Location Aided Routing (LAR):
LAR type 2 algorithm works as follows:
The sender includes the distance to the source in the Route-Request packet;
Intermediate nodes compute the distance to the destination:
if this distance is less than the distance between source and destination packet is forwarded;
otherwise the packet is discarded.
Distance in the packet is updated at every node with lower distance to destination.
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37. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Associativity-Based Routing protocol
It is characterized by the following:
On-demand beacon-based protocol;
Routes are selected based on temporal stability of wireless links:
To determine temporal stability, each node maintains the count of its neighbors' beacons.
The protocol operates as follows:
source node floods the Route-Request packet, all intermediate nodes forward this packet;
Route-Request packet carries the following:
the path it has traversed;
the beacon count for corresponding node in the path.
when the first Route-Request reaches the destination, the destination:
waits for Route-Select time to receive multiple copies of Route-Request;
selects the path that has the maximum number of stable links;
replies to the source with Route-Reply packet.
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38. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Associativity-Based Routing protocol:
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If the link break occurs then the node closer to the source initiates a local link repair as follows:
broadcasts locally route repair packet (local query (LQ)) with limited TTL;
if this node fails to repair, then the next node closer to destination initiates a route repair;

39. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Associativity-Based Routing protocol
Signal Stability-based Adaptive Routing protocol(SSA):
This protocol is characterized by the following:
On-demand beacon-based protocol;
Routes are selected based on temporal stability of wireless links:
Based on temporal stability, each links is classified to:
Stable
Unstable
To determine temporal stability, each node measures the signal strength of beacons.
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40. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Signal Stability-based Adaptive Routing protocol(SSA):
The whole protocols consist of the following two parts:
Dynamic Routing Protocol (DRP): Maintains the routing table interacting with DRPs on other hosts.
Forwarding protocol (FP): Responsible for forwarding of packets to destination.
The protocol operates as follows:
If no route in cache, the node floods the Route-Request packet;
Route-Request packet carries the path it has traversed;
If the intermediate node receives the Route-Request via stable link it forwards it. Otherwise(via unstable link) it drops it.
When the first Route-Request reaches the destination, the destination:
waits for Route-Select time to receive multiple copies of Route-Request;
selects the path that is most stable-if two or more paths are equal in stability, the shortest path is selected and if two or more shortest paths are available, random path among them is selected.
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41. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Signal Stability-based Adaptive Routing protocol(SSA):
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42. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Signal Stability-based Adaptive Routing protocol(SSA):
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43. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Flow-Oriented Routing Protocol:
FORP uses the predictive mechanism to estimate Link Expiration Time (LET):
It is based on location, mobility and transmission range of nodes involved in forwarding;
The minimum of LET determines the route expiration time (RET).
It is assumed that GPS is used to make prediction of LET.
Disadvantages:
Devises are expensive.
Can only operate at the open air (due to GPS).
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44. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Flow-Oriented Routing Protocol:
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45. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Flow-Oriented Routing Protocol:
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46. Classifications of Routing Protocols: …Cntd
Reactive routing protocols:
Flow-Oriented Routing Protocol:
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47. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Core Extraction Distributed Ad Hoc Routing Protocol:
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48. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Core Extraction Distributed Ad Hoc Routing Protocol:
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49. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Core Extraction Distributed Ad Hoc Routing Protocol:
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50. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Core Extraction Distributed Ad Hoc Routing Protocol:
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51. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Core Extraction Distributed Ad Hoc Routing Protocol:
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52. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Zone Routing Protocol (ZRP):
This protocols uses a combination of proactive and reactive routing protocols:
Proactive: in the neighborhood of r hops: Intra-zone routing protocol (IARP);
Reactive: outside this zone: Inter-zone routing protocol (IERP)
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53. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Zone Routing Protocol (ZRP):
The protocol operates as follows:
if the destination is within the zone, the source sends packets directly;
if not, the destination sends RouteRequest to peripheral nodes;
if any peripheral node, has the destination in its zone it replies with RouteReply;
if not, peripheral nodes sends RouteRequest to their peripheral nodes and so on;
if multiple RouteReply are received the best is chosen based on some metric.
If the broken link is detected:
Intermediate node repairs the link locally bypassing it (proactive routing)
End nodes are informed;
Sub-optimal pass but very quick procedure;
After several local reconfiguration, the source initiates global pass finding to find optimal.
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54. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Zone-based Hierarchical Link State Routing Protocol(ZHLS):
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55. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Zone-based Hierarchical Link State Routing Protocol(ZHLS):
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56. Classifications of Routing Protocols: …Cntd Hybrid routing protocols:
Zone-based Hierarchical Link State Routing Protocol(ZHLS):
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57. Classifications of Routing Protocols: …Cntd
Hierarchical routing protocols:
These protocols introduce hierarchy in the network to achieve the following benefits:
reduction in the size of routing tables;
better scalability.
Hierarchical State Routing protocol:
HSR is characterized by the following:
HSR uses multi-clustering to enhance resource allocation and management;
HSR denes different levels of clusters;
at every level leader is elected;
the first level is made of single-hop clusters (physical clustering);
the next level is comprised of leaders of clusters.
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58. Classifications of Routing Protocols: …Cntd
Hierarchical routing protocols:
Hierarchical state routing protocol:
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59. Classifications of Routing Protocols: …Cntd
Hierarchical routing protocols:
Hierarchical state routing protocol:
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60. Classifications of Routing Protocols: …Cntd
Hierarchical routing protocols:
Hierarchical state routing protocol:
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61. Classifications of Routing Protocols: …Cntd
Hierarchical routing protocols:
Fisheye State Routing protocol:
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62. Classifications of Routing Protocols: …Cntd
Hierarchical routing protocols:
Fisheye State Routing protocol:
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63. Classifications of Routing Protocols: …Cntd
Power-aware routing protocols:
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