Routing

Routing is the process of determining the path that data must follow through a network to get from an origin to a destination. In the context of systems and networks, routing refers to how devices, such as routers and switches, use protocols and algorithms to make decisions about the route that data packets should take. 

Routing concepts 

• Router: A network device that is responsible for routing data traffic between different networks. It uses routing tables and routing protocols to decide the best path to send a packet. 

• Routing table: A database on a router that stores routes to different destinations. Each entry in the routing table includes a destination address, a network mask, and the next hop address. 

• Routing protocol: A set of rules and algorithms that routers use to exchange routing information and make routing decisions. Examples include RIP (Routing Information Protocol), OSPF (Open Shortest Path First) and BGP (Border Gateway Protocol). 

Types of routing 

• Static routing: Routes are manually configured by a network administrator. It is simple and consumes less router resources, but does not automatically adapt to changes in the network. 

• Dynamic routing: Uses routing protocols to automatically discover and maintain routes. Allows the network to adapt to changes, such as the addition of new routers or link failures. 

• Interior Routing (IGP): It is used within a single autonomous network, such as a LAN (Local Area Network). Some protocols of this type are RIP and OSPF. 

• External routing (EGP): It is used between different autonomous networks. BGP is the standard protocol for external routing, essential for the operation of the Internet. 

Routing protocols 

• RIP (Routing Information Protocol): It uses the number of hops as a metric to determine the best route. It is simple, but less efficient in large networks due to its limit of 15 hops. 

• OSPF (Open Shortest Path First): Use the algorithm to find the shortest route based on the cumulative cost of links. It is suitable for large and complex networks.  

• BGP (Border Gateway Protocol): Used for routing between different autonomous systems on the Internet. BGP makes decisions based on policy and routing attributes, and is essential for the scalability and stability of the overall network. 

Routing algorithms 

• Link-State algorithm: Each router has a complete view of the network topology and calculates the best route using Dijkstra's algorithm. OSPF is an example of a protocol that uses this algorithm. 

• Distance-Vector algorithm: Each router only knows the distance to its immediate neighbours and shares this information with them. RIP uses this algorithm, updating the routing tables at regular intervals. 

• Path vector routing algorithm: Used by BGP, where routing decisions are based on attributes and policies beyond simple hop counts or link costs.