 |
||
|
||
|
||
|
||
Definition
In information technology, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain subnetworks.
The most common
A given network can also be characterized by the type of data transmission technology in use on it (for example, a TCP/IPSystems Network Architecture network); by whether it carries voice, data, or both kinds of signals; by who can use the network (public or private); by the usual nature of its connections (dial-up or switched, dedicated or nonswitched, or virtual connections); and by the types of physical links (for example, optical fibre, coaxial cable, and Unshield Twisted pair). Large telephone networks and networks using their infrastructure (such as the Internet) have sharing and exchange arrangements with other companies so that larger networks are created.
Personal Area Network (PAN)
A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that are used in a PAN are printers, fax machines, telephones, PDAs and scanners. The reach of a PAN is typically about 20-30 feet (approximately 6-9 meters), but this is expected to increase with technology improvements.
Local Area Network (LAN)
This is a network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library may have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet.
Campus Area Network (CAN)
This is a network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, office building, or a military base. A CAN may be considered a type of MAN (metropolitan area network), but is generally limited to a smaller area than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area.
Metropolitan Area Network (MAN)
A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town/city. Routers, switches and hubs are connected to create a Metropolitan Area Network.
Global Area Network
Global Area networks (GAN) specifications are in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc.
In computer science the elements of a network are arranged in certain basic shapes (see figure):
- Ring: The ring network connects each node to exactly two other nodes, forming a circular pathway for activity or signals - a ring. The interaction or data travels from node to node, with each node handling every packet.
- Mesh is a way to route data, voice and instructions between nodes. It allows for continuous connections and reconfiguration around broken or blocked paths by “hopping” from node to node until the destination is reached.
- Star: The star network consists of one central element, switch, hub or computer, which acts as a conduit to coordinate activity or transmit messages.
- Fully connected: Self Explanatory
- Line - Everything connected in a single line.
- Tree: This consists of tree-configured nodes connected to switches/concentrators, each connected to a linear bus backbone. Each hub rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only.
- Bus: In this network architecture a set of clients are connected via a shared communications line, called a bus.
Common basic network devices:
- Gateway: device sitting at a network node for interfacing with another network that uses different protocols.
- Router: a specialized network device that determines the next network point to which to forward a data packet toward its destination. Unlike a gateway, it cannot interface different protocols.
- Bridge: a device that connects multiple network segments along the data link layer .
- Switch: a device that allocates traffic from one network segment to certain lines (intended destination(s)) which connect the segment to another network segment. So unlike a hub a switch splits the network traffic and sends it to different destinations rather than to all systems on the network.
- Hub:
connects multiple Ethernet segments together making them act as a
single segment. When using a hub, every attached device shares the same broadcast domain and the same collision domain. Therefore, only one computer connected to the hub is able to transmit at a time. Depending on the network topology, the hub provides a basic level 1 OSI model connection among the network objects (workstations, servers, etc). It
provides bandwidth which is shared among all the objects, compared to switches, which provide a dedicated connection between individual nodes.
- Repeater: device to amplify or regenerate digital signals received while setting them from one part of a network into another.
Peer-based
The biggest security threats facing IT managers and LAN administrators is increasingly the threat from inside. One such threat: unsuspecting users whose laptop from home carries a virus that can infect an entire network.
One defense is peer-based security -- rather than the timeworn approach of firewalls, antivirus software, and patches, all defending against Internet incursions.
Server-based
Capability based
ACL-based
In networkings, ACL refers to a list of rules detailing service port or (network) daemon names that are available on a host or other layer 3 device, each with a list of hosts and/or networks permitted to use the service. Both individual servers as well as routers can have network ACLs. Access control lists can generally be configured to control both inbound and outbound traffic, and in this context they are similar to firewalls.
Advantages:
1. Easy to communicate
2. Sharing data and resources
3. Save cost
4. Faster
5. Collaborate
6. Backup and Security centralized
Disadvantages:
1. No security
2. Loss of atonomy
3. Virus, Trojan and Worm virus
