NAT (Network Address Translation)  

Network address translation is a scheme that allows two connected networks to use different and incompatible IP addressing schemes. Address translation allows hosts on a private internal  network to transparently communicate with destinations on an external network or vice versa. NAT also refers to the name of a device that performs these functions. NATs perform transparent routing, which refers to the translation of and routing of data grams between different address realms. An address realmis typically an inside network that uses its own addressing as compared to the external Internet. Traditional routers route packets within a single address realm.

Network Access Methods

See “Access Method, Network;” and MAC (Medium Access Control). 

Network Architecture

Network architectures define the standards and techniques for designing and building communication systems for computers and other devices. In the past, vendors developed their own architectures and required that other vendors conform to this architecture if they wanted to develop compatible hardware and software. There are proprietary network architectures such as IBM’s SNA(Systems Network Architecture)and there are open architectures like the OSI(Open Systems Interconnection)model defined by the International Organization for Standardization. If an architecture is open, no one vendor controls it and many vendors are free to design software and hardware that works with the architecture.       

Network Connection Technologies 

Network connection technologies are used to connect peripherals to computers, computers to computers, computers to network devices, network devices to network devices, and so on.

Network Core Technologies   

A core network is a central network into which other networks feed. It must have the bandwidth to support the aggregate bandwidth of all the networks feeding into it. Traditionally, the core network has been the circuit-oriented telephone system. More recently, alternative optical networks bypass the traditional core and implement packet-oriented                    

technologies.

Network Design and Construction

The three main areas to be concerned with in designing a network are as follows:                                                    

 *  Infrastructure   The cabling system, network devices, and architecture design (topology) of the network                                                                        

*  Routing and route management  Standard routing, cut-through routing, label switching, MPLS, and so forth                                                                     

 *  Control and management Prioritization, QoS, and management  Note that WAN access networks and public network core technologies are discussed  under “Network Access Services,” “Network Core Technologies,” “NPN (New Public Network),” and “Optical Networks.”  

Network Layer Protocols

 The OSI (Open Systems Interconnection) model is a standard defined by the International Organization for Standardization. It is a layered architecture in which each layer defines a specific type of communication. The bottom layer, called the physical layer, is responsible for transmitting these messages as bit streams across a physical medium. The layers immediately above the physical layer define how data is packaged for transport over the physical network .Further up the protocol stack are layers that define how sessions between computers are established and managed. The uppermost layers define how applications interface with the network. The OSI model helps developers create products that work over a large variety of   platforms and operating systems. The network layer is the third layer of the protocol stack, just above the physical and data link layers. It is the routing layer and the layer that is responsible for network addressing.

NGN (Next Generation Network) 

This is another name for the “new public network” or NPN. NPN, while not yet a reality, is an evolution of the existing incumbent carrier telephony networks to a single converged network .The old circuit-switched model gives way to a packet-oriented multi service (voice, video, data) network that supports QoS (quality of service) and unique hybrid services such as Internet call waiting.

Node  

 A node is a network-connected device such as a workstation, a server, or a printer. Network connection devices such as bridges and routers are not usually referred to as nodes on a network, even though they have network addresses. In the IP addressing scheme, network nodes such as computers are called “hosts,” while  routers are sometimes called “gateways,” an older term that is rarely used today because gateways refer to application layer devices that join systems or networks and provide translation services between them.