Mobile agent

Mobile agent:

In computer science, the word mobile agent can be defined as a composition of computer software and data that is able to migrate or we can say that move)from one computer to another autonomously and continue its execution on the destination computer.
But in actuality, the mobile agent is the code/object on the move which travels in its itinerary within the network of connected nodes.
A mobile agent is also a type of software agent, with the feature of autonomy, social ability, learning, and most significantly, mobility.
A mobile agent is a process that can transport its state from one environment to another, with its data intact, and be capable of performing appropriately in the new environment.
Mobile agents decide when and where to move.
When a mobile agent decides to move, it saves its own state (process image), transports this saved state to the new host, and resumes execution from the saved state.
A mobile agent is a specific form of mobile code, within the field of code mobility.

There are two types of mobile agents and the classification is based on their migration path-

Mobile agents with predefined path: Have static migration path.
Free-roaming mobile agent: Have dynamic migration path. Depending upon the present network condition the mobile agent chooses its path.

Characteristics of mobile agent

Characteristics of mobile agent:

1. Migration

2. Data acquisition

3. Route determination

4. Communication

1. Migration:

Mobility is the characteristic that allows agents to move between network nodes, but migration is the function that controls how this transfer is achieved.
Although a mobile agent is essentially an executing process, the governing factor that distinguishes it from a normal process is the fact that not all of its instructions have to be executed on the same node.
Migration is normally forced upon a process by the system, due to resource location, load balancing, and other similar factors. This is generally a complex and intensive operation.
With mobile agents, it is the agent who decides when to move and the underlying infrastructure must support and execute this request.

There are two approaches to moving agents between network nodes:-

1. State-oriented.

This system allows agents to move at any point in their execution, usually through a mobility imperative (such as go, jump or move).
When this command is initiated, the current state of the agent is encapsulated and transferred across the network to the receiving network node. Once received, execution of the agent resumes at the instruction following the mobility imperative.
The capture of an agent's state can be achieved either by the agent itself or by the infrastructure, both of which are non-trivial tasks.

2. Stateless:

With a stateless system, agents can move at any point in the code but restart their execution from the beginning of their code rather than the point of migration.
This means that before the agent can move, all state information must be written to a data repository or knowledge base that is encapsulated and transferred with the agent.
At the receiving network node, if it needs to, the agent must restore its state manually from the repository.
Such systems are easy to migrate, but make writing the agent difficult since all of the state store/restore burden resides with the agent.

2. Data acquisition:

Mobile agents interrogate their local environment to acquire the information necessary to achieve their goals.
This information needs to be filtered locally by the agent before it is either stored with the agent or forwarded to some receiving destination (such as the original network node of the agent). Therefore, mobile agent systems need to have an appreciation of the resources with which they are working.

3. Route determination:

Once an agent has finished with a network node, it must make a decision of where to move to next. The acquisition of data leading to this decision can be derived by one of three methods:

Predetermination: This is where the agent is given the destinations that it must visit when it is launched. This is useful in situations where the activities of an agent need to be carefully controlled, for example, when making consistent alterations to resources or where the order in which network nodes are visited is important.
Dynamic determination: This method dictates that the agent has been given complete freedom over the network nodes that it can visit. The mobile agent may simply make a random choice, which is quite difficult unless it knows what nodes are available, or it may make a decision based upon its own node-knowledge history or information gained from other agents. This type of freedom is useful for data mining agents where a wide field of interrogation is required.
Hybrid determination: This is an amalgamation of pre-and dynamic-determination methods. Put simply, the mobile agent is given a list of destination nodes that it must (or must not) visit, but can still exercise some discretion if a potential node offers data or services that are compatible with the agent's goals. Alternatively, the agent is equipped with a set of criteria that determine the type of nodes that it can visit; nodes that do not fit these criteria cannot be visited by the agent. This is useful in situations where the speed (and maybe quality) of data return is more important than the depth of data covered.

4. Communication

The ability for agents to communicate is fundamental to mobile agent systems. There are two methods for agent communication to take place:-

Network-oriented: Agents communicate through some network-based mechanism, such as message passing. This means that the communicating parties do not have to be residing on the same node or even the same network.
Node-oriented: Agents communicate through some local inter-process communication mechanism, such as files, shared memory, or anonymous pipes. This means that the communicating parties must be currently executing on the same network node.

What is mobile agent? Discuss the characteristics of mobile agent.

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