Before starting our discussion on the topics, let’s learn some basics to help get better knowledge on this topic.
What does an input port in a router do?
Input, output, switching fabric, and routing processors make up a generic router. The point of attachment for a physical link and the point of entrance for incoming packets are both input ports.
What is the role of the forwarding table within a router?
To determine the outgoing link interface to which an incoming packet will be routed via switching fabric, entries are kept in a router’s forwarding table.
What is the difference between forwarding and routing?
The intricate process of network engineering includes both routing and forwarding. While forwarding is the active transportation of the data to its endpoint, routing acquires all the information that data needs to reach its endpoint.
Now, let’s get into the topic,
Using the forwarding table, the router transfers the packet that has arrived at the input link to the correct (or appropriate) output link.
• Each router’s forwarding table is kept up to date by the routing processor.
• At each input port, keeps a shadow copy of the forwarding table.
• At each input port, the shadow copy supports local packet forwarding decisions.
• It’s not necessary to rely on a centralized routing processor to decide how to forward packets.
• Because packet forwarding decisions are made at multiple points across the router, a bottleneck in forwarding processing that could otherwise occur can be avoided.
As a result, a high-speed router keeps a shadow copy of the forwarding table at each input port.
When utilizing the shadow copy, the decision regarding the forwarding of data is performed locally at each input port rather than through the use of a centralized routing processor. This type of scattered forwarding eliminates the potential for a bottleneck in the forwarding procedure to occur at a single location within the router.