Computer networks are the main connectivity mechanism for passing data in an electronic environment. A network is composed of several computers connected by a wired or wireless medium so data and other resources can pass through for sharing.
A computer network may be as small as two computers connected by wire or wireless medium to as big as millions of computers connected throughout the internet. There are generally five classifications of network connectivity which are personal area network (PAN), local area network (LAN), campus area network (CAN), metropolitan are network (MAN) and wide area network (WAN).
Computer networks may also be classified according to the hardware technology used in connecting each device. The classification include Ethernet, wireless, LAN, Home PNA and power line communication.
The arrangement of computers in a network can also vary. The network topology refers to geometric forms in network connectivity. This could also describe the way computers see each other in relation to their logical order. Examples of network topologies are mesh, ring, star, bys, star-bus combination, tree or hierarchical topologies. It is good to note that although topology implies form, network topology is really independent of the physical placement or layout of computers. For instance, a star topology does not literally mean that computers form a star but it means that computers are connected using a hub which has many points to imply a star form.
Perhaps the biggest aspect of computer connectivity is the use of communications protocol. In a network, different formats of data are being shared by different computer systems which may have different hardware and software specifications. Communications protocol tries to break down the disparity so that data could be shared and appropriately processed.
Communications protocol are the set of rules and standards by which data is represented, signaled, authenticated and corrected before or after sending over the channel of communication. For example, in a voice communication like the case of radio dispatcher talking to mobile stations, they follow a standard set of rules on how to exchange communication.
A communication protocol may be hard to generalize because of the varied purposes and different degree of sophistication. But most connectivity protocols commonly have the following properties:
- communicating devices detect the physical connection whether it is wired or wireless
- devices do handshaking, a process of trying to find out if the other one exists
- negotiation about different characteristics of the connection
- determining the start and end a message
- formatting of a message for compatibility
- determining how to deal with corrupted message
- detecting unexpected data loss and acting on the appropriate steps
- properly closing the connection
The internet, the largest arena for computer and data connectivity, the protocols are assigned by the Internet Engineering Task Force (IETF) in close coordination with the W3C and ISO/IEC standard bodies. These bodies deal mainly with standards of the TCP/IP and Internet protocol suite.
The Institute of Electrical and Electronics Engineers (IEEE) an international non-profit, professional organization also sets communication protocols among electronic and electrical devices.
Some of the major protocol stacks include open standards for connectivity including the Internet protocol suite (TCP/IP), file transfer protocol (FTP), Open Systems Interconnection (OSI), iSCSI, Network File System (NFS) and Universial Plug and Play (UPnP).
Proprietary standard protocols include DECnet, AppleTalk, Systems Network Architecture (SNA) and Distributed Systems Architecture (DSA).