Ad-Hoc Routing Protocols (Characteristics)

Classification of the Characteristics of Ad-Hoc Protocols and Routing-Strategies

Extension of Lang2003 and Murthy2004.

In general, routing can be divided into two strategies:
Adaptive Routing vs. Not-Adaptive Routing

Adaptive: Changes of the network-topology are adapted by the routing-strategy
Not-Adaptive: The routing is done using fixed tables

For Ad-Hoc-Netorks, only adaptiv strategies are usefull.
Reactive Routing/On-Demand Routing vs. Proactive Routing/Table-Driven Routing vs. Hybrid Routing

Reactive/On-Demand
- A route is only calculated, when it is needed
- Does not try to keep routing-information everytime to all node
Proactive/Table-Driven
- Routes are calculated before one is needed
- Tries to keep routing-information to all nodes everytime up-to-date
- Update of the tables:
  - Event-driven: only if a change is recoginzed
  - Periodically
Hybrid
- Reactive and Proactive at the same time
- E.g.: Intra-Zone: Proactiv, Inter-Zone: Reactiv

Distance-Vector Routing vs. Link-State Routing

Distance-Vector
- Calculates the distance to all nodes
- Exchange of these information only with the neighbours
Link-State
- Mesuare the distance to the neighbours
- Exchange of these information with all nodes

Flat Routing vs. Hierarchical Routing / Clustered Routing

Hierarchical Routing / Clustered Routing:
- Trying to structure/cluster the network
- Clusterhead:
  - Responsible for the creation and extension of a cluster
  - Builds up a hierarchie of clusters
  - Manages the communication inside a cluster
- Gateway-Node:
  - Responsible for the communication between clusters
  - Maybe bottleneck
Flat Routing:
- Network has no hierarchy

Geographical Routing / Positionbased Routing / Direction-Based Routing

No routing-tables
Information is send in any way in the direction of the destination
No overhead to find or update routes

But:

Position required
Determination of the position via
- internal search-process
- external service

Uniform vs. Non-Uniform

Uniform: All nodes are equal
Non-Uniform: Some nodes have special roles, e.g. Clusterhead, Gateway-Node

Full vs. Reduced Topology Information

Full: All topology-information will be distributed
Reduced: Only a fraction of the known topology-information will be distributed

Past History vs. Prediction

Past History: Information of past statuses is used to make a decision
Prediction: Expectation of future statuses are used to make routing decisions

Broadcast

Local Multicast: Only to some nodes in transmission-distance
Local Broadcast: Only to the nodes in transmission-distance
Networkwide Broadcast: Flooding
Restricted Networkwide Broadcast: Flooding with a time-to-live

Recovery Strategy

Mechansims to keep or to restore routes

Link-Reversal Routing

Does not try to find an (somehow) optimal way
Only tries to find any way

Source-Routing

The sender specifies the way to go
Under the circumstances, a node inbetween can decide to redefine the way

Route-Selection-Strategies