Great question! The reason the link layer header is removed by the router is that each layer only needs the information relevant to it. Here’s a breakdown of why that happens:
- Link Layer Header (Data Link Layer):
- The link layer header is used for communication between devices on the same network, such as your computer and a router, or between routers in the same network.
- It contains information such as the MAC address (hardware address) of the sending and receiving devices.
- When your packet leaves your device (say, your laptop), the link layer header is added to ensure it can be successfully delivered over the local network (e.g., Ethernet).
- Router’s Role:
- When the packet reaches a router, the router is responsible for routing the packet based on its IP address.
- However, the router does not need the link layer information to route the packet over the network. The link layer header was only necessary for local delivery, so the router removes it.
- Next Hop:
- The router inspects the IP header (from the Internet layer) to determine where to send the packet next.
- The link layer header is then recreated for the next hop because, in the next network, a new link layer address (MAC address) will be required.
So in short, the link header is removed by the router because it’s specific to local network communication, and the router only deals with the IP address to route the packet to the correct destination.