Networking, The OSI Layer Network Model

Networking

Networking is a means of connecting computers together so that they can share data, such as files and programs, and resources, such as printers and modems. As with all other computer-related subjects, the subject of networking can be broken down into two categories:

Network hardware
Network software

Network architecture is the overall design of the network, including the physical components, network technologies, interfacing software and the protocols needed to establish reliable communication among each computer or workstation, which is called a network station, a node, or a host.

Data is sent over a network as bits and bytes that have been translated into electronic signals using the following steps:

1. Data is divided into segments, each of which has a header and trailer attached. The headers and trailers are called a frame, and the entire unit is called a packet.

2. The data packets are sent as independent units over the network.

3. At the receiving end, the header and trailer information is removed, and the data within the packets is reassembled into contiguous data.

Sending data over a network is similar to shipping a computer to a destination.

1. The computer (data) is disassembled and packed into several boxes with address labels attached (headers and trailers).

2. When the boxes arrive, the components (data segments) are unpacked and reassembled into a complete computer.

3. The units (the combination of shipping boxes, labels, and computer components) are the data packets.

4. While in transit, the computer (data) cannot function as a computer because it has been temporarily disassembled. Once it arrives at its destination, the packing is removed, and the computer is reassembled and ready for use.

For PCs, it is the job of the network card to break the data into segments and enclose each segment in headers and trailers, thus creating individual packets. The segments are reassembled back into contiguous data on the receiving end. In the computer shipping analogy, think of the network card in the sending PC as the packing and shipping department and the network card in the receiving PC as the person who receives the boxes, unpacks them, and assembles the computer system. There are two approaches to managing a network: a peer-to-peer network where each individual workstation manages its own security and resources, and a client-server network that is managed by a single server. Windows NT calls these two types of networks workgroups and domains, respectively.

The OSI Layer Network Model

In the 1970s, when manufacturers were beginning to build networking software, firmware, and hardware to connect computers, each manufacturer developed its own standards of communication within its proprietary network design.

In the early 1980s, manufacturers began to make attempts to standardize networking so those networks from different manufacturers could communicate. Two bodies that were leaders in this standardization are the following:

International Organization for Standardization (ISO)

Institute of Electrical and Electronics Engineers (IEEE)

One major effort of the IEEE was to standardize Token Ring and Ethernet protocols, which are both considered industry standards for networking at the network interface card level.