CMPE 150 – Winter 2009 Lecture 3 January 13, 2009 P.E. Mantey

CMPE Introduction to Computer Networks Instructor: Patrick Mantey Office: Engr. 2 Room 595J Office hours: Tuesday 3-5 PM TA: Anselm Kia Web site: Text: Tannenbaum: Computer Networks (4 th edition – available in bookstore, etc. )

Syllabus

Today’s Agenda Standards Layered Network Architecture - review Networks and History Physical Layer Signals and Systems Fourier Analysis Communication Theory

Standards Required to allow for interoperability between equipment Advantages Ensures a large market for equipment and software Allows products from different vendors to communicate Disadvantages Freeze technology May be multiple standards for the same thing

Standards Organizations IEEE ANSI Internet Society ISO ITU-T (formally CCITT) ATM forum

Network Standardization Who’s Who in the Telecommunications World Who’s Who in the International Standards World Who’s Who in the Internet Standards World

ITU Main sectors Radiocommunications Telecommunications Standardization Development Classes of Members National governments Sector members Associate members Regulatory agencies

IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with  are hibernating. The one marked with † gave up.

Metric Units The principal metric prefixes.

Reference Models The TCP/IP reference model.

Reference Models Protocols and networks in the TCP/IP model initially.

Comparing OSI and TCP/IP Models Concepts central to the OSI model Services Interfaces Protocols

A Critique of the OSI Model and Protocols Why OSI did not take over the world Bad timing Bad technology Bad implementations Bad politics

Bad Timing “The apocalypse of the two elephants.”

A Critique of the TCP/IP Reference Model Problems: Service, interface, and protocol not distinguished Not a general model Host-to-network “layer” not really a layer No mention of physical and data link layers Minor protocols deeply entrenched, hard to replace

Hybrid Model The hybrid reference model used by Tannenbaum

Internet Layering Level 5 -- Application Layer (rlogin, ftp, SMTP, POP3, IMAP, HTTP..) Level 4-- Transport Layer(a.k.a Host-to-Host) (TCP, UDP, ARP, ICMP, etc.) Level 3-- Network Layer (a.k.a. Internet) (IP) Level 2-- (Data) Link Layer / MAC sub-layer (a.k.a. Network Interface or Network Access Layer) Level 1-- Physical Layer

Example Networks The Internet Connection-Oriented Networks: X.25, Frame Relay, and ATM Ethernet Wireless LANs: 802:11

Architecture of the Internet

TCP/IP Reference Model Protocols and networks in the TCP/IP model initially.

Characteristics Internet Layer Connectionless Internet Protocol (IP) Task is to deliver packets to destination Transport Layer Transmission Control Protocol (TCP) Connection-oriented Reliable User Datagram Protocol (UDP) Connectionless Unreliable

TELCO Networks Connection-Oriented Networks X.25 Frame Relay ATM Fixed Route (set up at start of call) Quality of Service Billing – for connection time

T’s and D’s

T1 Time-division multiplexed stream of 24 telephone channels The basic technology upon which all T-carrier facilities are based Uses a full-duplex digital signal over two wire pairs. Bandwidth of Mbps through telephone- switching network Uses AMI or B8ZS coding.

O’s

SONET Synchronous Optical NETwork Synchronous Digital Hierarchy (SDH) Europe Internet for CARRIERS Worldwide standard Multiplex multiple digital channels Management support for –Operations –Administration –Maintenance

X.25 and Frame Relay X First Public Data Network – 1970s –Call and connect “Data Terminal Equipment” –Simple packet structure –Implemented “virtual circuit” connections –Flow control, hop-by-hop error control –Multiplexing – up to 4095 circuits at a time Frame Relay – 1980s (up to 2Mbps) –Limited error control, flow control –VC based packet switching --“wide area LAN”

Asynchronous Transfer Mode Vintage mid -1980s Goal to unify voice networks and data networks Packet Switching with virtual circuits (“channels”) Fixed-length packets (“cells”) 53 bytes –5 byte header, 48 byte “payload” –Virtual channel header (VCI) –No retransmission link-by-link Error correction codes only Envisioned to reach the end user Used widely today for backbones

ATM Virtual Circuits A virtual circuit.

ATM Virtual Circuits (2) An ATM cell.

The ATM Reference Model The ATM reference model.

The ATM Reference Model (2) The ATM layers and sublayers and their functions

Ethernet Architecture of the original Ethernet.

Wireless LANs (a) Wireless networking with a base station. (b) Ad hoc networking.

Wireless LANs (2) The range of a single radio may not cover the entire system.

Wireless LANs (3) A multicell network.

The ARPANET (a) Structure of the telephone system. (b) Baran’s proposed distributed switching system.

The ARPANET (2) The original ARPANET design. IMP = Interface Message Processor (Honeywell DDP-316)

The ARPANET (3) Growth of the ARPANET (a) December (b) July 1970.(c) March (d) April (e) September 1972.

NSFNET The NSFNET backbone in 1988.

UC CENIC January 2009

SIGNALS and SYSTEMS

What is a signal?

SIGNALS and SYSTEMS What is a signal? What is a system?

SIGNALS and SYSTEMS What is a signal? What is a system?

SIGNALS and SYSTEMS What is a signal? What is a system? Signal: time varying function produced by physical device (voltage, current, etc.)

SIGNALS and SYSTEMS What is a signal? What is a system? Signal: time varying function produced by physical device (voltage, current, etc.) System: device or process (algorithm) having signals as input and output Input x(t) output y(t)

SIGNALS and SYSTEMS

ax(t) ay(t) a 1 x 1 (t) + a 2 x 2 (t) a 1 y 1 (t) + a 2 y 2 (t) Superposition

SIGNALS and SYSTEMS Periodic signals -- f(t+T) = f(t) Period = T (seconds) Frequency = 1/ Period (“cycles” / sec. = Hertz (Hz)

SIGNALS and SYSTEMS Periodic signals -- f(t+T) = f(t) Period = T (seconds) Frequency = 1/ Period (“cycles” / sec. = Hertz (Hz) Radian frequency: (radians/sec.)

SIGNALS and SYSTEMS Reference: Signals, Systems and Tranforms Leland B. Jackson Addison Wesley

SIGNALS and SYSTEMS

100MHz square wave What bandwidth required for transmission?

SIGNALS and SYSTEMS Periodic Signal --- Composed of sinusoids MATLAB Demo

SIGNALS and SYSTEMS Periodic Signal --- Composed of sinusoids

Fourier Series is the “fundamental frequency”

Fourier Series Integration limits: when, then so we get:

Fourier Series Euler:

Fourier Series We can show ; recall that

Phasors: Phasors

References Stallings, W. Data and Computer Communications (7th edition), Prentice Hall 2004 chapter 1 Web site for Stallings book Web sites for IETF, IEEE, ITU-T, ISO Internet Requests for Comment (RFCs) Usenet News groups comp.dcom.* comp.protocols.tcp-ip