Lecture 11: Router Architectures

Today's lecture covered the routers architecture. Explaining that there are two key router functions: routing and forwarding. Running routing algorithms to decide best path to reach its destination and fowarding data from the input link to the output link.
Input ports,output ports and switching fabric are important components of a router. Input ports perform the physical layer functions(line termination), the data link layer functions(data-link processing) and the network layer functions(lookup,fowarding and queuing). Import queuing takes place when data arrives faster than it can forward into switching fabic. Head of the Line blocking (HOL) queuing is when data at the front of the queue stops other data in the queue from moving forward. Switching fabric connects the routers input ports to its output ports. There are three types of switching fabrics: memory, bus and crossbar. And the output ports performs the reverse of the input port functions.
The lecture also covered bridges. A bridge connects networks. They are needed for two reasons; it strengthens signals if communication is large and provides autonomy.
The bridge must have a database to keep track of which hosts are on which networks. To do this the system administrator can hard code the addressses or the bridge could learn the information as it goes. A learning bridge can move from one network to another and hosts can be added at any time. This would allow no manual setup from humans. The problem with this is the possibility of looping in a system of two or more bridges. Some of the ways to fix this issue is to have the bridges detect loops and feed it back to the user or design the bridge to prune itself so there is no loops in the network.