Delivery:)
Refers to the way a packet is handled by the underlying networks under the control of
network layer.
Forwarding:)
This refers to the way a packet is delivered to the next station.
Routing:)
This refers to the way routing tables are created to help in forwarding.
Delivery
- The network layer supervises the handling of the packets by the underlying physical networks.
- We define this handling as the delivery of a packet.
- The sender can easily determine if the delivery is direct. It can extract the network address of the destination using the mask and compare this address with the address of the network to which it is connected.
- In indirect delivery, the packet goes from router to router until it reaches the one connected to the same physical network as its final destination.
- A delivery always involves one direct delivery but zero or more indirect deliveries. The last delivery is always a direct delivery.
FORWARDING
- Forwarding means to place the packet in its route to its destination.
- Forwarding requires a host or a router to have a routing table.
- When a router has received a packet to be forwarded, it looks at this table to find the route to the final destination.
- Number of entries in the routing table need to be managed.
- The next-hop method reduces the contents of the routing table.
- Host-specific versus network-specific method.
- In host-specific methods, there is an entry for every destination host connected to the same physical network.
- In the network-specific method, only one entry that defines the address of the destination network itself. Means we treat all hosts connected to the same network as one single entity.
Instead of listing all networks in the entire internet, host A can have one entry called the default (normally defined as network address 0.0.0.0)
