Network Structure

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 nodesNetwork Infrastructure• Lines• Equipment to interconnect the linesNetwork Transmission Media• Copper wire• Radio transmission lines• Silicon fibre strandsTypes of Copper Wire Lines• Overhead copper wire• Twisted pair cable• Polyquad cable• Coaxial CableOverhead 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 circuitTwisted Pair Cable• Same characteristics as overhead wires• Less unsightly• More circuits per routePolyquad Cable• Can be used for low frequency radio signals• Can be used for low rate digital transmissionCoaxial Cable• Better direct current characteristics than overhead wires or twisted pair cable• Can be used to transmit high frequency radio signalsTypes of Radio Lines• Microwave - line of sight terrestrial• Microwave - earth satelliteMicrowave Radio - Line of Sight• Can be affected by adverse weather• May be subjected to physical obstruction• Could be harmful to people and/or animalsFibre 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 yearsNodes• Used to:** Interconnect links or bearers** Derive communications channels** Enhance network signals** Produce, accept, or pass signalsNetwork Topology• Fully Interconnected• Bus• Ring• Star• Interconnected Star• Interconnected Star Plus Ring• Through Connected Link• The Tandem Principle• Hierarchical StructureBearers • Consist of:** Copper wire cables** Fibre-optic cables** Radio transmission links• Serve:** User access networks** Wide area networksUser Access Networks• Traditionally a copper wire pair connecting users’ premises to the public networkOften referred to as:** the local loop** the last kilometre or mile** the local distribution networkTransmission 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