Understanding Network Routing: Static vs Dynamic Protocols

Posted on Jan 4, 2025 in Language

Network Routing Fundamentals

Routing: It is the function responsible for selecting the routes to be followed by messages through the network. This process, carried out at the Network layer, requires the identification of unique equipment. Routing processes are performed by special devices called routers.

Routing Tables

Routers know the location of possible recipients of the messages because they manage their own “maps”. These maps are representations of network topology that are stored in special tables. The table of a router can be created in two ways:

Static Routing

It consists of manually editing the routing tables to include routes that do not vary. These table entries are created when there is only one route to a destination and this will not change anytime soon. It’s also useful for safety when you want to prevent outside users from getting detailed information about the state of the network, intercepting messages that are sent to information routers when using dynamic protocols.

Dynamic Routing

It consists of activating a routing protocol that allows sending routing information between devices to create tables with dynamic entries. These table entries are dynamic, meaning they change as you change the state of the network. This mechanism is better than static routes as they keep very updated information on the status of the network, making routing more effective and efficient. For dynamic routing, routers need to keep routing tables with information about the best routes and send information between them to modify and update these tables based on network status. For this reason, the dynamic routing protocol must define what types of messages will be used to update the routing information, how, and when to send them.

Dynamic Routing Protocol Objectives
  • Choosing the Best Route: The best route selection can be made based on many criteria, such as distance, number of intermediate equipment to the destination, less congested routes, links with higher transmission capacity, and more reliable routes.
  • Simplicity: It is important that the routing algorithm is simple, so that routers do not require large requirements in processor and memory consumption. A simple algorithm also facilitates the growth of the network, avoiding delays in the transmission of messages.
  • Robustness: The routing protocol must be prepared to face all kinds of unexpected or unlikely events, so as to avoid blockages or malfunctions in the routers.
  • Speed: When changes occur in the network, such as installing new equipment and communication links or some stop working, it is important that the routing protocol calculates routes in the shortest possible time to avoid lost messages. This is the algorithm reached as soon as possible the state of convergence, which is reached when all the network routers have calculated the best routes to all possible destinations.
  • Growth: It is important to consider the possibilities of the routing algorithm to function optimally in a network of small or large size.

Characteristics of Dynamic Routing Protocols

  1. Métrica: Dynamic routing protocols value each of the routes to potential destinations to determine which is the best in terms of speed or reliability. This assessment should be quantitative so that the algorithms can compare the routes and decide where to send the information at all times. This parameter is called a metric and is a numerical value calculated by the routers and sent to their neighbors for information. The lower the metric value, the better the route is considered. The calculation of the metric can be as simple as counting the number of intermediate routers between the source and destination or as complex as assessing the transmission rate and degree of congestion of a link. In general, dynamic routing algorithms can take into account the following parameters when performing the calculation of the metric:
    • Speed Transmission: The transmission capacity of the link, expressed in bps (bits per second).
    • Delay: The time the message needs to reach its destination.
    • Congestion: Number of messages circulating through the path and are processed by intermediate routers.
    • Reliability: Rate of messages that reach their destination compared to the lost ones.
    • Saltos: Number of intermediate routers to the destination.
    • Cost: Used in networks with pricing to express the economic cost of sending the message to its destination.
  2. Equilibrado load: Most dynamic routing protocols can include multiple entries in their routing tables that specify the same destinations with the same or different metric value. In this way, you can achieve load balancing, where the router sends messages to the same destination but through different routes. This allows for better distribution of the workload on the network, resulting in more efficient use of the network. RIP load balancing is performed only when the paths to the same destination have the same metric. However, IGRP allows load balancing even if the paths to the same destination have different metrics, also taking into account the speed of transmission links.
  3. Bucles routing: In routing protocols based on distance vector, it is possible that situations arise in which the messages traverse the same routers, which are known as loops. These loops are due to inconsistent entries in routing tables, which are recorded when the network takes a long time to reach the state of convergence. It is very undesirable for loops to occur on a network and for messages to remain indefinitely spinning. In this situation, it is best that any of the routers realize this and end up discarding the message. For the routers to be able to distinguish and discard messages brought into loops, it is necessary that these include information on the hop count, i.e., the number of intermediate routers that have gone through, so that when it reaches a certain value, it can be discarded. This maximum value should be set to a value greater than the number of hops that exist between the two destinations furthest away from the network.
  4. Distancias administrative: In a network architecture, it is easy to find different routing protocols. For this reason, many routers work with several routing algorithms at once, whether static or dynamic. When a router works with other routing protocols simultaneously, each will have its own boards and its own metrics, the latter calculated based on different measures. In this situation, it is logical to find that each protocol records the same entries in its table, but with different metric values. The problem that arises has to do with using different measures of metrics for different protocols; they are not directly comparable. To solve this problem of comparison of routes between different routing protocols, the administrative distance is defined, which is the value of reliability of a protocol. The lower this value, the more reliable a protocol is considered among others, and the routes will most often be selected with respect to others.