Introduction to Networks

Transcription

1 Introduction to Networks Network Topology How we interconnect network users Network Hierarchy The connection between network topology and geographical size Telecommunication (Phone Networks) Circuit Switching Multiplexing SONET OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 1

2 The Simplest Network Topology Network Node Network Node Transmission Link OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 2

3 Bus Topology Very easy to add a device to the bus Common topology for connecting devices by Ethernet The network must handle Collisions OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 3

4 Star and Hub Topology HUB No collisions Devices easily added by connecting them to the hub, but may require more wiring than a bus OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 4

5 Recovery from Link Failure A link failure isolates a node in a network with star topology until the link can be repaired. OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 5

6 Ring Topology A ring is the simplest topology for which all nodes remain connected after a link failure. OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 6

7 Dual Rings Dual uni-directional rings, with working (W) and protection (P) rings are are part of the popular SONET networking protocol OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 7

8 Mesh Topology Mesh networks are used to connect nodes that are distributed over large geographical areas. OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 8

9 Recovery from Link Failure Networks with mesh topology are robust OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 9

10 Network Hierarchy Core/Wide Area Networks - 100's to 100's of kilometers - Countries, Continents Data Rate, Cost Metropolitan/Aggregation Networks - 10's of kilometers - Cities Access/Local Area Networks - kilometers - Campuses, Neighborhoods, Buildings, Homes OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 10

11 Networks = Fiber Amplifier Signal Dispersion Compensation Transmission links are lengths of optical fiber (or free-space beam paths) that may have components inserted that condition the optical signal OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 11

12 Network Nodes Transceiver = Electrical Input Diode Laser/ LED Driver Photodiode Output Input = Tranceiver + Tranceiver + Electrical Output Post Amp TIA Most nodes contain one or more optical transceivers OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 12

13 Network Nodes OEO ADM = Signals Tranceiver Electrical Signals Add-Drop Multiplexer Electrical Signals Tranceiver Signals Electrical Input = Add Electrical Output = Drop Nodes such as an add-drop multiplexer, process data in the electrical domain OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 13

14 O-O Network Nodes OO = Splitter OO = λ 1 λ j λ n Add-Drop Multiplexer λ 1 λ i λ n λ i λ j Transparent optical-to-optical nodes are becoming more common. OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 14

15 Telecommunication (Phone) Networks Central Office/ Local Exchange Phone networks are Circuit Switched meaning that links are allocated to phone call for the entire duration of the call. OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 15

16 Time Division Multiplexing Data Steam 1 Data Steam 2 Data Steam 3 Time Division Multiplexer Combined Data Stream Data Steam 4 Time Division Multiplexing (TDM) combines lower data rate signals into higher data rate signals OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 16

17 Time Division Multiplexing Digital Service Level 0 64 kbps DS0 DS1 DS1 Time Division Multiplexer DS1 Electrical Data Steam Mbps DS1 DS1 Time Division Multiplexer STS-1 Electrical Data Stream Mbps Transmitter OC-1 Data Stream Mbps DS1 Many individual phone calls carried by Digital Service Level 0 (DS0) links can be multiplexed for transmission over long distances. An OC-1 ( Carrier 1) carries 672 phone calls. OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 17

18 The Synchronous Network (SONET) Hierarchy Signal Designation Data Rate (Mbps) Phone Call Capacity OC OC OC OC OC OC , OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 18

19 Wavelength Division Multiplexing Transmitter λ 1 λ 1, λ 2, λ n λ 1 Receiver Transmitter λ 2 λ 2 Receiver Fiber Amplifier Dispersion Compensation Transmitter λ n Wavelength Division Multiplexer De-Multiplexer λ n Receiver A wavelength division multiplexed (WDM) link with 80 OC-192 wavelength channels operates at close to 1 Terabit per second and carries just over 10,000,000 simultaneous phone calls OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 19

20 The International Telecommunication Union (ITU) Grid 100 GHz Wavelength (nm) The ITU specifies wavelengths centered at THz spaced by 50 GHz GHz to be used for WDM. OPTI 500, Spring 2011, Lecture 2, Introduction to Networks 20