UNIT IV: ROUTING PROTOCOLS:
DESIGN ISSUES:-
The modern research has found a variety of applications and systems with vastly
varying requirements and characteristics in Wireless Sensor Networks (WSNs). The
research has led to materialization of many applications specific routing protocols
which must be energy-efficient. As a consequence, it is becoming increasingly
difficult to discuss the design issues requirements regarding hardware and software
support. Implementation of efficient system in multidisciplinary research such as
WSNs is becoming very difficult.
3.1 LIMITED ENERGY CAPACITY: Since sensor nodes are battery powered, they
have limited energy capacity. Energy poses a big challenge for network designers in
hostile environments. Furthermore, when the energy of a sensor reaches a certain
threshold, the sensor will become faulty and will not be able to function properly,
which will have a major impact on the network performance.
3.2 SENSOR LOCATIONS: Another challenge that faces the design of routing
protocols is to manage the locations of the sensors. Most of the proposed protocols
assume that the sensors either are equipped with global positioning system (GPS)
receivers or use some localization technique [3] to learn about their locations.
3.3 LIMITED HARDWARE RESOURCES: Sensor nodes have also limited processing
and storage capacities, and thus can only perform limited computational
functionalities. These hardware constraints present many challenges in software
development and network protocol design for sensor networks.
3.4 MASSIVE AND RANDOM NODE DEPLOYMENT: Sensor node deployment in
WSNs is application dependent and can be either manual or random which finally
affects the performance of the routing protocol. In most applications, sensor nodes
can be scattered randomly in an intended area or dropped massively over an
inaccessible or hostile region.
3.5 NETWORK CHARACTERISTICS AND UNRELIABLE ENVIRONMENT: A sensor
network usually operates in a dynamic and unreliable environment. The topology of a
network, which is defined by the sensors and the communication links between the
sensors, changes frequently due to sensor addition, deletion, node failures,
damages, or energy depletion. Also, the sensor nodes are linked by a wireless
medium, which is noisy, error prone, and time varying. Therefore, routing paths
should consider network topology dynamics due to limited energy and sensor
mobility as well as increasing the size of the network to maintain specific application
requirements in terms of coverage and connectivity.
3.6 DATA AGGREGATION: Since sensor nodes may generate significant redundant
data, similar packets from multiple nodes can be aggregated so that the number of
transmissions is reduced. Data aggregation technique has been used to achieve
energy efficiency and data transfer optimization in a number of routing protocols. 3.7
Diverse sensing application
,requirements: Sensor networks have a wide range of diverse applications. No
network protocol can meet the requirements of all applications. Therefore, the routing
protocols should guarantee data delivery and its accuracy so that the sink can gather
the required knowledge about the physical phenomenon on time.
3.8 SCALABILITY: Routing protocols should be able to scale with the network size.
Also, sensors may not necessarily have the same capabilities in terms of energy,
processing, sensing, and particularly communication. Hence, communication links
between sensors may not be symmetric, that is, a pair of sensors may not be able to
have communication in both directions. This should be taken care of in the routing
protocols.
3.9 MOBILITY: Network topology is highly dynamic due to movement of nodes.
Hence, an ongoing session suffers frequent path breaks. Disruption occurs due to
the movement of either intermediate nodes in the path or end nodes. Wired network
routing protocols cannot be used in adhoc wireless networks because the nodes are
here are not stationary and the convergence is very slow in wired networks. Mobility
of nodes results in frequently changing network topologies. Routing protocols for ad
hoc wireless networks must be able to perform efficient and effective mobility
management.
3.10 BANDWIDTH CONSTRAINT: - Abundant bandwidth is available in wired
networks due to the advent of fiber optics and due to the exploitation of wavelength
division multiplexing (WDM) technologies. In a wireless network, the radio band is
limited, and hence the data rates it can offer are much less than what a wired
network can offer. This requires that the routing protocols use the bandwidth
optimally by keeping the overhead as low as possible.
3.11 ERROR-PRONE SHARED BROADCAST RADIO CHANNEL: - The broadcast
nature of the radio channel poses a unique challenge in ad hoc wireless networks.
The wireless links have time-varying characteristics in terms of link capacity and link
error probability. This requires that the adhoc wireless network routing protocol
interact with the MAC layer to find alternate routes through better-quality links.
Transmissions in ad hoc wireless networks result in collisions of data and control
packets. Therefore, it is required that ad hoc wireless network routing protocols find
paths with less congestion.
GOALS OF ROUTING PROTOCOLS
There are following goals of Routing Protocols: -
Find the “optimal route”.
Rapid Convergence.
Robustness.
Configurable to respond to changes in many variables
(changes in bandwidth, delay, queue size, policy, etc.).
Ease of configuration.
Determine good paths from source to destination.
“Good” = least cost
, • Least propagation delay.
• Least cost per unit bandwidth (e.g., $ per Gbit/s)
• Least congested (workload-driven).
“Path” = a sequence of router ports (links).
Make networks resilient to failures.
Routers & links can fail without taking down the entire
network. Entire subsets can be unreachable; rest still
reachable. Hence, the protocol must be distributed.
CLASSIFICATION OF ROUTING PROTOCOLS
Routing is a process in which the layer 3 devices (either router or layer 3 switches)
find the optimal path to deliver a packet from one network to another. Dynamic
routing protocols use metric, cost, and hop count to identify the best path from the
path available for the destination network. There are mainly 3 different classes of
routing protocols:
Routing protocols are typically divided into categories like distance vector, link-state,
and hybrid protocols. Distance vector protocols, such as RIP, determine routes based
on the number of hops. Link-state protocols, like OSPF, rely on a more detailed
understanding of the entire network topology. Hybrid protocols, such as EIGRP,
incorporate elements from both approaches to balance efficiency and accuracy.
Types of Routing Protocols
There are mainly two types of Network Routing Protocols
Static
Dynamic
, A. STATIC ROUTING PROTOCOLS:-
Static routing protocols are used when an administrator manually assigns the path
from source to the destination network. It offers more security to the network.
ADVANTAGES:-
No overhead on router CPU.
No unused bandwidth between links.
Only the administrator is able to add routes
DISADVANTAGES:-
The administrator must know how each router is connected.
Not an ideal option for large networks as it is time intensive.
Whenever link fails all the network goes down which is not feasible in
small networks.
B. DYNAMIC ROUTING PROTOCOLS
Dynamic routing protocols are another important type of routing protocol. It helps
routers to add information to their routing tables from connected routers
automatically. These types of protocols also send out topology updates whenever
the network changes’ topological structure.
ADVANTAGES:-
Easier to configure even on larger networks.
It will be dynamically able to choose a different route in case if a link goes
down. It helps you to do load balancing between multiple links.
DISADVANTAGES
Updates are shared between routers, so it consumes bandwidth.
Routing protocols put an additional load on router CPU or RAM.
DESIGN ISSUES:-
The modern research has found a variety of applications and systems with vastly
varying requirements and characteristics in Wireless Sensor Networks (WSNs). The
research has led to materialization of many applications specific routing protocols
which must be energy-efficient. As a consequence, it is becoming increasingly
difficult to discuss the design issues requirements regarding hardware and software
support. Implementation of efficient system in multidisciplinary research such as
WSNs is becoming very difficult.
3.1 LIMITED ENERGY CAPACITY: Since sensor nodes are battery powered, they
have limited energy capacity. Energy poses a big challenge for network designers in
hostile environments. Furthermore, when the energy of a sensor reaches a certain
threshold, the sensor will become faulty and will not be able to function properly,
which will have a major impact on the network performance.
3.2 SENSOR LOCATIONS: Another challenge that faces the design of routing
protocols is to manage the locations of the sensors. Most of the proposed protocols
assume that the sensors either are equipped with global positioning system (GPS)
receivers or use some localization technique [3] to learn about their locations.
3.3 LIMITED HARDWARE RESOURCES: Sensor nodes have also limited processing
and storage capacities, and thus can only perform limited computational
functionalities. These hardware constraints present many challenges in software
development and network protocol design for sensor networks.
3.4 MASSIVE AND RANDOM NODE DEPLOYMENT: Sensor node deployment in
WSNs is application dependent and can be either manual or random which finally
affects the performance of the routing protocol. In most applications, sensor nodes
can be scattered randomly in an intended area or dropped massively over an
inaccessible or hostile region.
3.5 NETWORK CHARACTERISTICS AND UNRELIABLE ENVIRONMENT: A sensor
network usually operates in a dynamic and unreliable environment. The topology of a
network, which is defined by the sensors and the communication links between the
sensors, changes frequently due to sensor addition, deletion, node failures,
damages, or energy depletion. Also, the sensor nodes are linked by a wireless
medium, which is noisy, error prone, and time varying. Therefore, routing paths
should consider network topology dynamics due to limited energy and sensor
mobility as well as increasing the size of the network to maintain specific application
requirements in terms of coverage and connectivity.
3.6 DATA AGGREGATION: Since sensor nodes may generate significant redundant
data, similar packets from multiple nodes can be aggregated so that the number of
transmissions is reduced. Data aggregation technique has been used to achieve
energy efficiency and data transfer optimization in a number of routing protocols. 3.7
Diverse sensing application
,requirements: Sensor networks have a wide range of diverse applications. No
network protocol can meet the requirements of all applications. Therefore, the routing
protocols should guarantee data delivery and its accuracy so that the sink can gather
the required knowledge about the physical phenomenon on time.
3.8 SCALABILITY: Routing protocols should be able to scale with the network size.
Also, sensors may not necessarily have the same capabilities in terms of energy,
processing, sensing, and particularly communication. Hence, communication links
between sensors may not be symmetric, that is, a pair of sensors may not be able to
have communication in both directions. This should be taken care of in the routing
protocols.
3.9 MOBILITY: Network topology is highly dynamic due to movement of nodes.
Hence, an ongoing session suffers frequent path breaks. Disruption occurs due to
the movement of either intermediate nodes in the path or end nodes. Wired network
routing protocols cannot be used in adhoc wireless networks because the nodes are
here are not stationary and the convergence is very slow in wired networks. Mobility
of nodes results in frequently changing network topologies. Routing protocols for ad
hoc wireless networks must be able to perform efficient and effective mobility
management.
3.10 BANDWIDTH CONSTRAINT: - Abundant bandwidth is available in wired
networks due to the advent of fiber optics and due to the exploitation of wavelength
division multiplexing (WDM) technologies. In a wireless network, the radio band is
limited, and hence the data rates it can offer are much less than what a wired
network can offer. This requires that the routing protocols use the bandwidth
optimally by keeping the overhead as low as possible.
3.11 ERROR-PRONE SHARED BROADCAST RADIO CHANNEL: - The broadcast
nature of the radio channel poses a unique challenge in ad hoc wireless networks.
The wireless links have time-varying characteristics in terms of link capacity and link
error probability. This requires that the adhoc wireless network routing protocol
interact with the MAC layer to find alternate routes through better-quality links.
Transmissions in ad hoc wireless networks result in collisions of data and control
packets. Therefore, it is required that ad hoc wireless network routing protocols find
paths with less congestion.
GOALS OF ROUTING PROTOCOLS
There are following goals of Routing Protocols: -
Find the “optimal route”.
Rapid Convergence.
Robustness.
Configurable to respond to changes in many variables
(changes in bandwidth, delay, queue size, policy, etc.).
Ease of configuration.
Determine good paths from source to destination.
“Good” = least cost
, • Least propagation delay.
• Least cost per unit bandwidth (e.g., $ per Gbit/s)
• Least congested (workload-driven).
“Path” = a sequence of router ports (links).
Make networks resilient to failures.
Routers & links can fail without taking down the entire
network. Entire subsets can be unreachable; rest still
reachable. Hence, the protocol must be distributed.
CLASSIFICATION OF ROUTING PROTOCOLS
Routing is a process in which the layer 3 devices (either router or layer 3 switches)
find the optimal path to deliver a packet from one network to another. Dynamic
routing protocols use metric, cost, and hop count to identify the best path from the
path available for the destination network. There are mainly 3 different classes of
routing protocols:
Routing protocols are typically divided into categories like distance vector, link-state,
and hybrid protocols. Distance vector protocols, such as RIP, determine routes based
on the number of hops. Link-state protocols, like OSPF, rely on a more detailed
understanding of the entire network topology. Hybrid protocols, such as EIGRP,
incorporate elements from both approaches to balance efficiency and accuracy.
Types of Routing Protocols
There are mainly two types of Network Routing Protocols
Static
Dynamic
, A. STATIC ROUTING PROTOCOLS:-
Static routing protocols are used when an administrator manually assigns the path
from source to the destination network. It offers more security to the network.
ADVANTAGES:-
No overhead on router CPU.
No unused bandwidth between links.
Only the administrator is able to add routes
DISADVANTAGES:-
The administrator must know how each router is connected.
Not an ideal option for large networks as it is time intensive.
Whenever link fails all the network goes down which is not feasible in
small networks.
B. DYNAMIC ROUTING PROTOCOLS
Dynamic routing protocols are another important type of routing protocol. It helps
routers to add information to their routing tables from connected routers
automatically. These types of protocols also send out topology updates whenever
the network changes’ topological structure.
ADVANTAGES:-
Easier to configure even on larger networks.
It will be dynamically able to choose a different route in case if a link goes
down. It helps you to do load balancing between multiple links.
DISADVANTAGES
Updates are shared between routers, so it consumes bandwidth.
Routing protocols put an additional load on router CPU or RAM.
