L1: Introduction to Communication Networks (Telegraph & Telephone) Outline

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1 EECS 3213 Fall 2014 L1: Introduction to Communication Networks (Telegraph & ) Sebastian Magierowski York University 1 Outline Course texts, mark breakdown, topics Telegraph A connectionless message-switching A connection-oriented circuit-switching 2 1

Textbook & Topics Textbook: Communication Networks Ch. 1 8 1. Network Introduction (1.1-1.2) 2. Models, Layers and Applications (2.1-2.5) 3. Digital Information & Transmission (3.1-3.9) 4.

2 Textbook & Topics Textbook: Communication Networks Ch Network Introduction ( ) 2. Models, Layers and Applications ( ) 3. Digital Information & Transmission ( ) 4. Data Link Protocols ( ) 5. Multiple Access & LANs (6.1,6.2,6.6,6.7) 6. Packet Switching ( ) 7. TCP/IP Architecture ( ) 3 Overview Basic Internet operations and applications structure, addressing, routing, DNS, HTTP, etc. Basic principles sharing, metrics, scalability Physical layer (communications THEORY!!!!) signals, modulation, error detection, error correction, wires Data Link layer Flow control, framing Medium Access Control Dynamic medium control, ALOHA, Ethernet Network Layer routing & IP Transport Layer TCP 4 2

Telegraph 1850 s text message service Tap on machine that sends voltage pulses A basic circuit 5 Digital Communications (1850s style) Conceptually convert

3 Telegraph 1850 s text message service Tap on machine that sends voltage pulses A basic circuit 5 Digital Communications (1850s style) Conceptually convert text into sequence of dots and dashes Morse Code Morse Code Morse Code Morse Code A J S 2 B K T 3 C L U 4 D M V 5 E N W 6 F O X 7 G P Y 8 H Q Z 9 I R

4 Physical Signal Characteristics Ideal signal as a function of time What does it actually look like? Intersymbol interfrence (ISI) 7 A Little Telegraph Quantification What was the data rate of this technology? (In bps) Operators could send 30 words-per-minute (wpm) Think of the dots/dashes as 1s/0s Or approximate the bits per character for constant length code 8 4

5 Keyboard Baudot multiplexer let 5 operators use a line at the same time Boosted the rate to? A 3 A 2 A 1 B 2 B 1 C 2 C 1 D 3 D 2 D 1 Baudot Multiplexer 5 bits / character Multiplexing A 2 D 1 C 1 B 1 A 1 Baudot Demultiplexer Paper Tape Printer Paper Tape Printer Paper Tape Printer Paper Tape Printer 9 Message Switching Vast of stations arose Operator examines source & destination address and routes the message to next most reasonable switch Source store-and-forward : examine message in full before sending to next node (as opposed to cut-through) Message Message Switches Message Message Destination Transmission by occasional connections referred to as message-switching indirect connection 10 5

The ~ 30 years after telegraph (1876 Bell s patent) Direct conversion of sound pressure to an electrical analog sound Microphone analog electrical signal Loudspeaker sound No need for digital

6 The ~ 30 years after telegraph (1876 Bell s patent) Direct conversion of sound pressure to an electrical analog sound Microphone analog electrical signal Loudspeaker sound No need for digital translation, a direct end-user service Plug and play Rough data rate? Shannon s Theorem 11 The Network Originally sold in pair What s the problem with this? N users requires???? connections 1000 users 499,500 connections 12 6

local central office) 13 The Switch Physical (copper) connection set up when call is made (a) Circuit Switching

7 The Network The birth of the switching office (and Bell Company, 1877) a wiring hub Run a wire between the customer and the telephone company switching office Now only need N connections to central office (CO) (aka end office or local central office) 13 The Switch Physical (copper) connection set up when call is made (a) Circuit Switching Human Switch (contrast with Strowger Switch (1888) message switching) now all digital verbal instructions number dialed 14 7

8 Network Hierarchy long distance carrier (AT&T, Verizon, etc.) 1 2 ~150 regions IXC POP ~150 COs per region Tandem office End office ~10k local loops To local loops per end office (end office = (central office) LATA 1 LATA 2 LATA 3 central office) 15 Path of a Call Phone signal out on copper pair i. After a call is placed, the voice data To local phone travel company along a pair of copper wires to a box with 100s local of ed inputs phone company box. This box contains hundreds To a digital concentrator of wire pairs. that digitizes the signal 2. The call is then routed to a "digital concentrator," where it is digitized at a sample rate of 8,000 Then via coaxial cable or fiber samples per second. to the phone company s switching station 3. The digitized information is then sent usually via coaxial or^iber Then perhaps to the switching optic cable to station the phone company's of a long distance switching station, where it will be routed to its destination. And so on, with the possibility of satellite call, the signal is transmission 4. If the call is a local simply looped back into the local system. If it is a long-distance call, the signal is forwarded to the EECS 3213, F14 long-distance. L1: Introduction [Kercher, Penguin] 16 8

Switching Station New York has 80 for 8,000,000 140 West St. Among the most 33 Thomas St. The 29-story Long 811 Tenth Ave.

is 1 4 0 West St., a 31-story once the name of the AT&T division the AT&T switching station in on Pearl St.

Brooklyn Bridge, is clad in white 375 Pearl St.

with windows York Company and Manhattan. The building, built represented by black vertical stripes.

in 1974, is said to be able to withstand Made 0/steel, brick, and stone, it nuclear fallout and has enough survived the

About 100,000 lines served by a station two Switching Stations Switching stations are the lynchpin of telephone

Each switching center contains a complex array of computer-controlled digital and fiber optic equipment that fulfills a

Each also contains sophisticated power, ventilation, and cooling systems to ensure the continued operation of the

One feature absent from many switching stations is windows: the absence of glass panes helps to protect telephone switches

In addition to switching stations, New York's telecommunications infrastructure includes carrier hotels, which locate

local and long-distance s. Perhaps the premier carrier hotel in the world is located at 60 Hudson St.

Over 100 domestic and Full 0/computer-controlled digital international telecom companies are housed there, including and

9 Switching Station New York has 80 for 8,000, West St. Among the most 33 Thomas St. The 29-story Long 811 Tenth Ave. Like other notable of New York's switching Lines Building (Long Lines w a s switching stations, the function of stations is West St., a 31-story once the name of the AT&T division the AT&T switching station in on Pearl St., adjacent to the facility constructed in 1926 as t h a t operated the long-distance Clinton has determined its shape. Brooklyn Bridge, is clad in white 375 Pearl St. The New York Company switching station the headquarters of the original New toll ) stands sentry in lower marble slabs with windows York Company and Manhattan. The building, built represented by black vertical stripes. more recently Verizon's centra! office. in 1974, is said to be able to withstand Made 0/steel, brick, and stone, it nuclear fallout and has enough survived the collapse of its neighbor, backup energy to operate for 7 World Trade Center, on 9 / 1 1. full weeks. About 100,000 lines served by a station two Switching Stations Switching stations are the lynchpin of telephone communications, and there are 80 or so of them spread out across the five boroughs. Each switching center contains a complex array of computer-controlled digital and fiber optic equipment that fulfills a variety of functions: call processing, billing, distribution, and enhanced features for subscribers. Each also contains sophisticated power, ventilation, and cooling systems to ensure the continued operation of the equipment. One feature absent from many switching stations is windows: the absence of glass panes helps to protect telephone switches and sensitive electronic equipment from dust, temperature, and humidity. In addition to switching stations, New York's telecommunications infrastructure includes carrier hotels, which locate carriers and service providers together to allow direct connections between them and to facilitate access to multiple local and long-distance s. Perhaps the premier carrier hotel in the world is located at 60 Hudson St. in Manhattan, the former Western Union headquarters. Over 100 domestic and Full 0/computer-controlled digital international telecom companies are housed there, including and fiber optic equipment, AT&T, Cable & Wireless, GTE-Verizon, Time Warner switching stations provide a variety of different connection paths Telecom, Qwest, and [Kercher, Penguin] for voice calls and data circuits. L1: Introduction EECS 3213, F14 Global Crossing. 17 Three Phases of a Connection 1. Connection set up connection oriented: a that establishes a connection before transmitting information circuit switching: formation of dedicated path between source and destination 2. Information transfer 3. Connection release EECS 3213, F Pick up phone Dial tone. Dial number Network selects route; Sets up connection; Called party alerted Exchange voice signals Hang up. 18 9

10 Digitization of the Network Pulse Code Modulation 64 kbps uncompressed voice signal (8-bit sample every 125 µs) Time Division Multiplexing (TDM) Put multiple signals on the trunk T1 carrier method sends a signal from one of 24 messages every 125 us (24*8+1)/125 us = Mbps Digital Switching (no analog conversion) No need to go back to analog at switch Optical Transmission bps!!! 19 10

L1: Introduction to Communication Networks. Outline

SC/CSE 3213 Winter 2014 L1: Introduction to Communication Networks Sebastian Magierowski York University 1 Outline Course texts, mark breakdown, topics Telegraph A connectionless message-switching network