General Overview of Enterprise Networks

In this tutorial which titled General Overview of Enterprise Networks, we will identify different network types, Ascertain essential network characteristics, Ascertain main network functionality, Understand what is meant by transmission and Appreciate the need for signaling in networks. This is one of about 14 others articles.

Network Functionality
• Separate networks for voice, television, data and text is outmoded
• Separate networks may nevertheless be around for some time
• Ultimately the Public Switched Telephone Network (PSTN) and the Internet will become one
• Mobile networks will remove travel constraints
• Virtual reality will allow physical actions to be conducted remotely

Network Structures
• Start by considering what is needed to be achieved
• Networks must achieve functionality in an economic manner
• A variety of configurations are possible

Network Structures
• Star
• Multi-exchange
• Typical National Network Hierarchy

Typical National Network Hierarchy
• Lines within users’ premises
• Lines to users’ premises (the access network)
• Junction to interconnect local exchanges
• Trunks to interconnect trunk exchanges

Types of Network Node
• User nodes
• Service nodes
• Switching nodes
• Transmission nodes

Network Services
• Historically different networks were provided for different services
• Despite differences a common transmission infrastructure was used

Telecommunications Regulations
• Need to take account of :
** Control of pricing
** Access to customers
** Ensuring effectiveness of competition
** Public network protection from harm

Telecommunications Standards
• Needed to ensure interoperability between different :
** Networks
** Systems
** Countries

Telecommunications Standards Bodies
• International Telecommunications Union (ITU) was CCITT
• ITU consists of ITU-T and ITU-R
• International Standards Organization (ISO)
• European Telecommunications Standards Institute (ETSI)
• America Standards Institute (ANSI)
• Institute of Electrical and Electronic Engineers (IEEE)
• The Association Francais du Normalisation (AFNOR)
• The British Standards Institution (BSI)
• The Deutsches Institute fur Normung (DIN)

Telecommunications Standards Use
• Aid interworking between networks and features
• Aid interconnection between components
• Reduce complexity
• Promote and encourage competition

The ISO Reference Model for Open System Interconnection
• A model to describe all types of networks in 7 discrete layers
• Compliance with one layer ensures interworking with adjacent layers
• Sending layer passes information down to layer beneath until lowest layer is reached
• Information then passes up the layer stack at the receiving end
• Voice network need only comply with layers 1 to 3
• Data networks need to comply with layers 1 to 6

Reference ModelThe ISO Seven Layer
• Physical : Which deals with physical attachment to communications lines.
• Data Link : Which provides transfer and control of data over communications lines, error correction, etc.
• Network : Which adds destination switching, routing and relaying functions and presents these in a manner which is • independent of the actual network in use.
• Transport : Which provides user-to-user services, including multiplexing, to make the most effective use of network facilities. It enhances the quality of the service to that necessary for the application.
• Session : Which controls the dialogue between users and supports synchronization of their activity.
• Presentation : Which allows for the selection of the representation of data, resolving differences between systems.
• Application : Providing the interface to user applications and common services, such as file transfer and terminal support.