ELEN 602 Computer Communications Networks Instructor Narasimha Reddy Contact reddy ee tamu edu 845 7598 320 F Wisenbaker Textbook Communication Networks by Leon Garcia Widjaja Class notes available http ee tamu edu reddy ee602 02 html Teaching Assistant Grader To Be Announced TA Office Hours To Be Announced Grading Homeworks 30 Tests 60 Project 10 ELEN 602 Lecture 1 1 Some Communication Networks Flying Pigeons Marathon Runners Reflecting Mirrors Telephone Telegraph Cable TV Internet Satellite based cable telephone ELEN 602 Lecture 1 2 Telephone Functioning 1 2 3 4 5 6 Telephone Office The caller picks up the phone triggering the flow of current in wires that connect to the telephone office Telephone Office The current is detected and a dial tone is transmitted by the telephone office to indicate that it is ready to receive the destination number Telephone Office The caller sends this number by pushing the keys on the telephone set Each key generates a pair of tones that specify a number In the older phone sets the user dials a number which in turn generates a corresponding number of pulses Telephone Office The equipment in the telephone office then uses the telephone network to attempt a connection If the destination telephone busy then a busy tone is returned to the caller If the destination telephone is idle then ringing signals are sent to both the originating and destination telephones Telephone Office The ringing signals are discontinued when the destination phone is picked up and communication can then proceed Telephone Office Either of the users terminate the call by putting down a receiver ELEN 602 Lecture 1 3 Web Access Steps 1 2 3 4 5 6 The user clicks on a link to indicate which document is to be retrieved The browser must determine the address that contains the document It does this by sending a query to its local name server Once the address is known the browser establishes a connection to the specified machine usually a TCP connection In order for the connection to be successful the specified machine must be ready to accept TCP connections The browser runs a client version of HTTP which issues a request specifying both the name of the document and the possible document formats it can handle The machine that contains the requested document runs a server version of HTTP It reacts to the HTTP request by sending an HTTP response which contains the desired document in the appropriate format The TCP connection is then closed and the user may view the document ELEN 602 Lecture 1 4 Realplayer example Copyright 1995 2000 RealNetworks Inc All rights reserved RealPlayer is a trademark of RealNetworks Inc ELEN 602 Lecture 1 5 Steps in Communication US Mail Compose the letter based on the user office personal Package it for transport put it in an envelope address to and from it leave it in a well known port mailbox Postman picks up the mail local post office sorts it for further transport Number of letters may be bundled and transported to remote city Remote post office sorts them by local addresses postman delivers it to the To mailbox Remote person picks up the mail receives the message ELEN 602 Lecture 1 6 Work in generic communication Addressing how to address the comm for transport telephone numbers US Mail addresses IP addresses Name to address translation phone directory address book DNS name resolution Routing which way to send a piece of comm to reach B from point A East coast US mail may go to Houston New York Transport how to actually move the data mail bits Trucks planes with US mail telephone wires LAN Multiplexing of different pieces of communication ELEN 602 Lecture 1 7 What you will learn in this class Addressing IPv4 and IPv6 Routing routing protocols Name resoultion DNS Transport Physical media Ethernet SONET FDDI ATM etc Multiplexing switches routers Queuing theory delay loss analysis Protocols TCP IP Some Applications http email etc ELEN 602 Lecture 1 8 t1 t0 Network ELEN 602 Lecture 1 9 a A switch provides the network to a cluster of users Network Access network b A multiplexer connects two access networks ELEN 602 Lecture 1 10 1 a a 2 3 b 4 A c Metropolitan network A consists of access subnetworks a b c d d Metropolitan b A ELEN 602 Lecture 1 National network consists of regional subnetworks Metropolitan network A is part of regional subnetwork 11 Transmission capacity bits second 1 0E 14 DWDM 1 0E 12 SONET OC 48 1 0E 10 T 4 carrier 1 0E 08 T 1 carrier 1 0E 06 1 0E 04 Baudot multiplex 1 0E 02 1 0E 00 Printing telegraph 1850 1875 1900 1925 1950 ELEN 602 Lecture 1 1975 2000 12 a A switch in the form of an operator with a patch cord panel not shown b Cords interconnect user sockets providing end to end connection ELEN 602 Lecture 1 13 Toll Tandem Tandem CO CO CO CO CO ELEN 602 Lecture 1 14 a Time Shared Computers Cables for Input Devices C T T b Dial In C T T T Modem Pool PSTN Modem T T terminal ELEN 602 Lecture 1 15 Poll to terminal C Response from terminal T T T ELEN 602 Lecture 1 T 16 T Host Mux Address Info ELEN 602 Lecture 1 T T 17 Host T Chicago T T San Francisco New York City Atlanta ELEN 602 Lecture 1 18 AMES McCLELLAN UTAH BOULDER GWC CASE RADC ILL CARN LINC USC AMES MIT MITRE UCSB STAN SCD ETAC UCLA RAND TINKER BBN HARV ELEN 602 Lecture 1 NBS 19 transceivers a b ELEN 602 Lecture 1 20 G net 1 net 3 G G G net 2 net 5 G net 4 G G gateway ELEN 602 Lecture 1 21 Technology Standards Market Regulation ELEN 602 Lecture 1 22 Capability Capability Third type of invention Second type of invention Initial class of invention a time b ELEN 602 Lecture 1 time 23