Communication Network EKT 331 Mohd Alif Hasmani B

Communication Network EKT 331 Mohd Alif Hasmani B. Abd Ghani School of Computer & Communication Engineering KUKUM 04 -9798915 / 013 -9215261

Assessment l. Final Exam - 50 % l. Course Work – 50 % l. Lab / Mini Project – 30 % l. Test – 20%

References l. Alberto Leon-Gracia and Indra Widjaja, “Communication Network – Fundamental Concepts and Key Architectures”, Mc. Graw Hill, 2004 l. William Stalling, “Data and Computer Communication”, 6 th Edition, Prentice Hall, 2000 l. Andrew S. Tanenbaum, “Computer Networks”, PH PTR, 2003

Chapter 1 : Introduction to Communication Networks and Services

Communication Services & Applications l l A communication service enables the exchange of information between users at different locations. Communication E-mail services & applications are everywhere. E-mail server Exchange of text messages via servers

Communication Services & Applications l l A communication service enables the exchange of information between users at different locations. Communication services & applications are everywhere. Web Browsing Web server Retrieval of information from web servers

Communication Services & Applications l l A communication service enables the exchange of information between users at different locations. Communication services & applications are everywhere. Instant Messaging Direct exchange of text messages

Communication Services & Applications l l A communication service enables the exchange of information between users at different locations. Communication services & applications are everywhere. Telephone Real-time bidirectional voice exchange

Communication Services & Applications l l A communication service enables the exchange of information between users at different locations. Communication services & applications are everywhere. Cell phone Real-time voice exchange with mobile users

Communication Services & Applications l l A communication service enables the exchange of information between users at different locations. Communication services & applications are everywhere. Short Message Service Fast delivery of short text messages

What is a communication network? Communication Network l l l The equipment (hardware & software) and facilities that provide the basic communication service Virtually invisible to the user; Usually represented by a cloud Equipment l Routers, servers, switches, multiplexers, hubs, modems, … l Facilities l l Copper wires, coaxial cables, optical fiber Ducts, conduits, telephone poles … How are communication networks designed and operated?

Communication Network Architecture Network architecture: the plan that specifies how the network is built and operated l Architecture is driven by the network services l Overall communication process is complex l Network architecture partitions overall communication process into separate functional areas called layers Next we will trace evolution of three network architectures: telegraph, telephone, and computer networks l

Network Architecture Evolution l Telegraph Networks l l Telephone Networks l l Circuit Switching Analog transmission → digital transmission Mobile communications Internet l l Message switching & digital transmission Packet switching & computer applications Next-Generation Internet l Multiservice packet switching network

Bell’s Telephone l l Alexander Graham Bell (1875) working on harmonic telegraph to multiplex telegraph signals Discovered voice signals can be transmitted directly l l Microphone converts voice pressure variation (sound) into analogous electrical signal Loudspeaker converts electrical signal back into sound Telephone patent granted in 1876 Bell Telephone Company founded in 1877 Signal for “ae” as in cat Microphone sound Loudspeaker analog electrical signal sound

Bell’s Sketch of Telephone

Signaling l Signaling required to establish a call l l Flashing light and ringing devices to alert the called party of incoming call Called party information to operator to establish calls Signaling + voice signal transfer

The N 2 Problem l l For N users to be fully connected directly Requires N(N – 1)/2 connections Requires too much space for cables Inefficient & costly since connections not always on 1 N = 1000 N(N – 1)/2 = 499500 2 N . . . 4 3

Telephone Pole Congestion

Circuit Switching Patchcord panel switch invented in 1877 Operators connect users on demand l l l Establish circuit to allow electrical current to flow from inlet to outlet Only N connections required to central office l 1 N N– 1 3 2

Manual Switching

Strowger Switch l l Human operators intelligent & flexible l But expensive and not always discreet Strowger invented automated switch in 1888 l Each current pulse advances wiper by 1 position l User dialing controls connection setup Decimal telephone numbering system Hierarchical network structure simplifies routing l Area code, exchange (CO), station number 1 st digit 2 nd digit . . . 0 0 0. . 9 0 9 9 9

Strowger Switch

Hierarchical Network Structure Toll CO = central office Tandem CO CO CO Telephone subscribers connected to local CO (central office) Tandem & Toll switches connect CO’s

Three Phases of a Connection 1. 2. Connection set up Telephone network Pick up phone Dial tone. Telephone network Dial number 3. Telephone network Network selects route; 4. Information transfer Connection release Telephone network 5. Telephone network 6. Telephone network Sets up connection; Called party alerted Exchange voice signals Hang up.

Computer Connection Control l l Coordinate set up of telephone connections To implement new services such as caller ID, voice mail, . . . To enable mobility and roaming in cellular networks “Intelligence” inside the network A separate signaling network is required Computer Switch connects Inlets to Outlets Signaling . . . l A computer controls connection in telephone switch Computers exchange signaling messages to: . . . l Voice

Digitization of Telephone Network l Pulse Code Modulation digital voice signal l l Time Division Multiplexing for digital voice l l l T-1 multiplexing (1961): 24 voice signals = 1. 544 x 106 bps Digital Switching (1980 s) l l Voice gives 8 bits/sample x 8000 samples/sec = 64 x 103 bps Switch TDM signals without conversion to analog form Digital Cellular Telephony (1990 s) Optical Digital Transmission (1990 s) l l One OC-192 optical signal = 10 x 109 bps One optical fiber carries 160 OC-192 signals = 1. 6 x 1012 bps! All digital transmission, switching, and control

Elements of Telephone Network Architecture l Digital transmission & switching l l Circuit switching l l l User signals for call setup and tear-down Route selected during connection setup End-to-end connection across network Signaling coordinates connection setup Hierarchical Network l l l Digital voice; Time Division Multiplexing Decimal numbering system Hierarchical structure; simplified routing; scalability Signaling Network l Intelligence inside the network

Computer Network Evolution Overview l l 1950 s: Telegraph technology adapted to computers 1960 s: Dumb terminals access shared host computer l SABRE airline reservation system 1970 s: Computers connect directly to each other l ARPANET packet switching network l TCP/IP internet protocols l Ethernet local area network 1980 s & 1990 s: New applications and Internet growth l Commercialization of Internet l E-mail, file transfer, web, P 2 P, . . . l Internet traffic surpasses voice traffic

What is a protocol? l l Communications between computers requires very specific unambiguous rules A protocol is a set of rules that governs how two or more communicating parties are to interact l l Internet Protocol (IP) Transmission Control Protocol (TCP) Hyper. Text Transfer Protocol (HTTP) Simple Mail Transfer Protocol (SMTP)

A familiar protocol Caller replies Dials 411 “What city”? “Springfield” “What name? ” “Simpson” “Thank you, please hold” Caller waits Caller replies Caller waits Caller dials “Do you have a first name or street? ” System replies Operator replies “Evergreen Terrace” “Thank you, please hold” Operator replies System replies with number

Computer-to-Computer Networks l l As cost of computing dropped, terminal-oriented networks viewed as too inflexible and costly Need to develop flexible computer networks l l l Interconnect computers as required Support many applications Application Examples l l l File transfer between arbitrary computers Execution of a program on another computer Multiprocess operation over multiple computers

Elements of Computer Network Architecture l l l Digital transmission Exchange of frames between adjacent equipment l Framing and error control Medium access control regulates sharing of broadcast medium. Addresses identify attachment to network or internet. Transfer of packets across a packet network Distributed calculation of routing tables

Elements of Computer Network Architecture l l l Congestion control inside the network Internetworking across multiple networks using routers Segmentation and reassembly of messages into packets at the ingress to and egress from a network or internetwork End-to-end transport protocols for process-to-process communications Applications that build on the transfer of messages between computers. Intelligence is at the edge of the network.

Trends in Network Evolution l It’s all about services l l l Building networks involves huge expenditures Services that generate revenues drive the network architecture Current trends l l l Packet switching vs. circuit switching Multimedia applications More versatile signaling End of trust Many service providers and overlay networks Networking is a business

Multimedia Applications l l l Trend towards digitization of all media Digital voice standard in cell phones Music cassettes replaced by CDs and MP 3’s Digital cameras replacing photography Video: digital storage and transmission l l Analog VCR cassettes largely replaced by DVDs Analog broadcast TV to be replaced by digital TV VCR cameras/recorders to be replaced by digital video recorders and cameras High-quality network-based multimedia applications now feasible

More Versatile Signaling l Signaling inside the network l l l Connectionless packet switching keeps network simple & avoids large scale signaling complexity Large packet flows easier to manage using circuitlike methods that require signaling Optical paths also require signaling Generalized signaling protocols being developed End-to-End Signaling l l Session-oriented applications require signaling between the endpoints (not inside the network) Session Initiation Protocol taking off

End of Trust l Security Attacks l l l Firewalls & Filtering l l Spam Denial of Service attacks Viruses Impersonators Control flow of traffic/data from Internet Protocols for privacy, integrity and authentication

Servers & Services l Many Internet applications involve interaction between client and server computers l l l Enhanced services in telephone network also involve processing from servers l l Client and servers are at the edge of the Internet SMTP, HTTP, DNS, … Caller ID, voice mail, mobility, roaming, . . . These servers are inside the telephone network Internet-based servers at the edge can provide same functionality In future, multiple service providers can coexist and serve the same customers

Operations, Administration, Maintenance, and Billing l Communication like transportation networks l l l Highly-developed in telephone network l l l Traffic flows need to be monitored and controlled Tolls have to be collected Roads have to be maintained Need to forecast traffic and plan network growth Entire organizations address OAM & Billing Becoming automated for flexibility & reduced cost Under development for IP networks

Transmission Technology l l Relentless improvement in transmission High-speed transmission in copper pairs l l Higher call capacity in cellular networks l l Lower cost cellular phone service Enormous capacity and reach in optical fiber l l DSL Internet Access Plummeting cost for long distance telephone Faster and more information intensive applications

Standards l l New technologies very costly and risky Standards allow players to share risk and benefits of a new market l l Reduced cost of entry Interoperability and network effect Compete on innovation Completing the value chain l l Chips, systems, equipment vendors, service providers Example l 802. 11 wireless LAN products

Standards Bodies l Internet Engineering Task Force l l l International Telecommunications Union l l International telecom standards IEEE 802 Committee l l Internet standards development Request for Comments (RFCs): www. ietf. org Local area and metropolitan area network standards Industry Organizations l MPLS Forum, Wi. Fi Alliance, World Wide Web Consortium