In this course, our target is understand the meaning of network infrastructure, differentiate between core and access networks, understanding the meaning of ‘bearer’, and which bearers are used in different parts of the network and ‘node’, and the network configurations to interconnect nodes
Network Infrastructure
• Lines
• Equipment to interconnect the lines
Network Transmission Media
• Copper wire
• Radio transmission lines
• Silicon fibre strands
Types of Copper Wire Lines
• Overhead copper wire
• Twisted pair cable
• Polyquad cable
• Coaxial Cable
Overhead Copper Wire Lines
• Wires suspended from poles and masts
• Wires have to be insulated from one another
• Wires have to be insulated from earth
• Wires have to form a complete end-to-end circuit
Twisted Pair Cable
• Same characteristics as overhead wires
• Less unsightly
• More circuits per route
Polyquad Cable
• Can be used for low frequency radio signals
• Can be used for low rate digital transmission
Coaxial Cable
• Better direct current characteristics than overhead wires or twisted pair cable
• Can be used to transmit high frequency radio signals
Types of Radio Lines
• Microwave - line of sight terrestrial
• Microwave - earth satellite
Microwave Radio - Line of Sight
• Can be affected by adverse weather
• May be subjected to physical obstruction
• Could be harmful to people and/or animals
Fibre Optic Technology
• Uses Light Amplification by Stimulated Emission of Radiation (LASER)
• Precursor was clear atmosphere line of sight
• Then wave guidance
• Technology is still being refined after more than 30 years
Nodes
• Used to:
** Interconnect links or bearers
** Derive communications channels
** Enhance network signals
** Produce, accept, or pass signals
Network Topology
• Fully Interconnected
• Bus
• Ring
• Star
• Interconnected Star
• Interconnected Star Plus Ring
• Through Connected Link
• The Tandem Principle
• Hierarchical Structure
Bearers
• Consist of:
** Copper wire cables
** Fibre-optic cables
** Radio transmission links
• Serve:
** User access networks
** Wide area networks
User Access Networks
• Traditionally a copper wire pair connecting users’ premises to the public network
Often referred to as:
** the local loop
** the last kilometre or mile
** the local distribution network
Transmission Bearer Networks
• Used to link:
** telephone exchanges
** packet switching exchanges
** frame relay exchanges etc
• Analogue networks used coaxial cable and microwave links
• Digital networks use fibre-optic cable
• Used to provide transmission infrastructure
Monday, November 12, 2007
Network Structure
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.