Network Routing Strategies and Performance Criteria

Performance Criteria for Data Transfer

Performance criteria are the most complex and critical factors to be analyzed before a transfer of data to achieve more effective performance. When determining the choice of route, you can choose based on:

• A path with the least number of hops.
• A path involving the least cost.

Instant Decisions and Routing Placement

The routing decision is made based on a packet or virtual circuit. When a routing decision is based on a datagram, it is taken individually for each packet. In the case of virtual circuits, internally governed packets belonging to that circuit will follow the same route.

A third case is Source Routing, in which the source station is the decision maker rather than the network nodes.

Node Responsibility in Routing Decisions

The node or nodes are responsible for routing decisions, which can be of two types:

• Distributed: This is the most common approach for added resilience, where each node has the responsibility to select an outgoing link.
• Centralized: A single designated node makes the decision (this could be in the Network Control Center). A major drawback is that a failure of this node produces a complete blockade of the network.

Static Routing Characteristics

• Specifications for each pair of origin-destination nodes identify the next node in the route.
• There is no need to know the full path, only the identity of the next node.
• There is no differentiation between Datagrams and Virtual Circuits, since all packets will follow the same route.
• Advantages: Simplicity and performance.
• Disadvantage: Lack of flexibility (no reaction to failure or congestion).

Flooding Techniques for High Priority

Flooding is used for high-priority messages when there is no precise information on the network. The source node sends a copy of the packet to the neighboring nodes, which then send them via links to other nodes until a copy reaches the destination.

Properties of Flooding:

1. All possible paths between the origin and destination nodes are tested.
2. A copy of the packet will use the least number of jumps.
3. The packets visit all nodes that are directly or indirectly connected to the origin.
4. This method generates a high volume of traffic.

Random and Adaptive Routing Strategies

Random Routing: This is an upgrade to previous methods for higher congestion control. It selects only one departure way to transmit the incoming packet. The outgoing link is chosen randomly without considering the previous link.

Adaptive Routing: Decisions change according to the conditions of the network. If the network experiences node or line failures, the system recognizes these cannot be part of the route. In cases of congestion, the zone will be bypassed through management.

• Nodes exchange information about the network status.
• This technique is used more frequently than static routing because it offers:

1. Improvement of services.
2. Mitigation of the emergence of serious congestion situations.

Packet Switching Network Fundamentals

In brief, a packet switching network consists of a "mesh" interconnection provided by telecommunications services, through which packets travel from source to destination.