Lecture 20 Detailed Notes on Routing and Network Strategies

Introduction to Telecommunications

  • Telecommunications involves transmitting information over distances for communication purposes.
  • Networks are a key component of telecommunications, allowing different devices to communicate effectively.

Review: Local Area Network (LAN)

  • Topology: Layout of the network and how devices are connected.
  • LAN Protocol (LLC): Logical Link Control (LLC) manages protocol access to the physical network.
  • Delay in LAN: Refers to the time it takes for data to travel across the network.

Routing (Chapter 19)

  • Routing is a complex and critical aspect of packet-switched networks.
  • A path or route must be determined for data packets.
  • More than one route might be possible for packet transmission.
  • Routing is essential for efficient communication in networks.

Routing Characteristics in Packet-Switched Networks

  • Correctness: Ensures each packet is delivered correctly.
  • Simplicity: The routing process should be straightforward.
  • Robustness: Ability to deliver packets despite localized failures or overloads.
  • Stability: Should not overly react to network changes.
  • Fairness: Equitable treatment of all users in the network.
  • Optimality: Routes should be optimal based on certain criteria (e.g., cost, delay).
  • Efficiency: Involves low processing overhead and resource utilization.

Routing Performance Criteria

  • Criteria include: Number of hops, cost, delay, and throughput.
  • Decision Time:
    • Virtual Circuit: Decisions made at connection establishment.
    • Datagram: Decisions made before packets are placed in the outgoing buffer.
  • Decision Place: Decisions can be made at each node, a central node, or the originating node.

Routing Strategies

  • Four Key Strategies:
    1. Fixed Routing: Pre-established routes based on least-cost algorithms.
    2. Flooding: Packets are sent out on every outgoing link except the incoming link.
    3. Random Routing: One outgoing link randomly chosen based on probability.
    4. Adaptive Routing: Routes adjust according to network conditions (e.g., congestion).

Fixed Routing Strategy

  • A route is predetermined for each source-destination pair.
  • A central routing directory can be distributed to all nodes.
  • Routes change only with network topology changes.
  • Advantages: Simplicity; Disadvantages: Inflexible during congestion or failures; useful for small networks.

Flooding Strategy

  • A packet is sent through every outgoing link, excluding the arrival link.
  • Unique identifiers and hop counters can manage duplicates.
  • Advantages: Robustness; tries all possible routes; Disadvantages: High traffic loads.

Random Routing Strategy

  • Involves selecting an outgoing link randomly based on a probability distribution.
  • Advantages: No need for network information; Disadvantages: May not optimize for cost or hops.

Adaptive Routing Strategy

  • Algorithms change routes based on network conditions like congestion.
  • Advantages: Encourages performance improvement and congestion control; Disadvantages: Complexity, requires extra traffic for information gathering.
  • Can be characterized by the source of network information (local, adjacent nodes, all nodes) and control type (distributed or centralized).

Routing in Wireless Sensor Networks

  • Designed for power efficiency.
  • Sensor networks are typically data-centric and benefit from data aggregation.
  • Ideal designs incorporate attribute-based addressing and location awareness.

Energy-efficient Routing in Wireless Sensor Networks

  • Choosing routes based on Power Availability (PA).
  • Sample network routing possibilities with PA considerations:
    • Route options, their total PA, and total energy (α) costs are computed to determine optimal routes for efficient energy utilization.