Network Model Illustration

.

Wednesday

Network Model :: Network Layer

...

The network layer in a network model is responsible for the source-to-destination delivery of a packet, possibly across multiple network models (links). Whereas the data link layer oversees the delivery of the packet between two systems on the same network model (links), the network layer in a network model ensures that each packet gets from its point of origin to its final destination.

If two systems are connected to the same link, there is usually no need for a network layer in a network model. However, if the two systems are attached to different network models (links) with connecting devices between the network models (links), there is often a need for the network layer in network model to accomplish source-to-destination delivery. Figure 2.8 shows the relationship of the network layer to the data link and transport layers in a network model.


Network layer in a Network Model
Figure 2.8

Network layer in a network model



The network layer in a network model is responsible fcr the delivery of individual packets from the source host to the destination host.

Other responsibilities of the network layer in a network model include the following:

Logical addressing.

The physical addressing implemented by the data link layer handles the addressing problem locally. If a packet passes the network boundary, we need another addressing system to help distinguish the source and destination systems. The network layer in network model adds a header to the packet coming from the upper layer that, among other things, includes the logical addresses of the sender and receiver.

Routing.

When independent network models or links are connected to create internetworks (network of networks) or a large network model, the connecting devices (called routers or switches) route or switch the packets to their final destination. One of the functions of the network layer in network model is to provide this mechanism.

Figure 2.9 illustrates end-to-end delivery by the network layer in a network model.


end-to-end delivery by the network layer
Figure 2.9

Source-to-destination delivery




As the figure shows, now we need a source-to-destination delivery. The network layer at network model A sends the packet to the network layer at network model B. When the packet arrives at router B, the router makes a decision based on the final destination (F) of the packet. As we will see in later chapters, router B uses its routing table to find that the next hop is router E. The network layer at network model B, therefore, sends the packet to the network layer at network model E. The network layer at network model E, in turn, sends the packet to the network layer at network model F.


Next

...



Network Model

Layered Tasks in a Network Model

Network Model: THE OSI MODEL

Network Model :: Physical Layer

Network Model :: Data Link Layer

Network Model :: Network Layer

Network Model :: Transport Layer

Network Model :: Session Layer

Network Model :: Presentation Layer

Network Model :: Application Layer

TCP/IP protocol suite in a Network Model

Addressing system in a Network Model

Important Points about Network Model

...
Copyright © 2009 The-Network Model housebrooks. All Rights Reserved.

Stats