Networking Objectives Part 2

SMK N 1 GEMPOL : Networking Objectives Part 2

OSI Protocol Stack Model

No book on networking would be complete without discussing the Open System Interconnection (OSI) model. This book is more interested in the lower layers of the protocol stack. One of the central goals of network design is to build reliable networks for applications to use.So a good design starts at the bottom of the stack, letting the upper layers ride peacefully on a stable architecture. Software people take a completely different view of the network. They tend to be most concerned about the upper layers, from Layer 7 down to about Layer 4 or 5. Network designers are most concerned with Layers 1 through 4 or 5. Software people don’t care much about cabling, as long as it doesn’t lose their data. Network designers don’t care much about the data segment of a packet, as long as the packet meets the standard specifications. This fact alone explains much of my bias in focusing on the lower parts of the stack. There are excellent books on network programming that talk in detail about the upper layers of the stack. That is largely beyond the scope of this book, however.


The Seven Layers
The OSI model is a useful way of thinking about networking. It’s important not to confuse it with reality, of course. The most commonly used networking protocols, such as TCP/IP, don’t completely match the model. But it is still a useful model.


Table 1-1 shows this simple model in its usual form.