CMPE 150 – Winter 2009

CMPE 150 – Winter 2009

Lecture 3

January 13, 2009

P.E. Mantey

CMPE 150 -- Introduction to Computer Networks

Instructor: Patrick Mantey [email protected] http://www.soe.ucsc.edu/~mantey/

Office: Engr. 2 Room 595J Office hours: Tuesday 3-5 PM TA: Anselm Kia [email protected] Web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/

Text: Tannenbaum: Computer Networks (4th 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 ModelsConcepts central to the OSI model

Services InterfacesProtocols

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

http://www.netstreamsol.com.au/networking/notes/general/t1_e1_t3_e3_ds0_ds1_ds3.html

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 1.544 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.25 -- 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 802.11 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 1969. (b) July 1970.(c) March 1971. (d) April 1972. (e) September 1972.

NSFNET

The NSFNET backbone in 1988.

http://www.internet2.edu/pubs/networkmap.pdf

http://www.nlr.net/services/map/

http://doc.cenic.org/tools/topology_map.pl?network=uc

UC CENIC January 2009

SIGNALS and SYSTEMS

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)

a1 x1(t) + a2 x2(t) a1 y1(t) + a2 y2(t)

Superposition

SIGNALS and SYSTEMS

Periodic signals --

f(t+T) = f(t) Period = T (seconds)

Frequency = 1/ Period

(“cycles” / sec. = Hertz (Hz)

001/f T

SIGNALS and SYSTEMS

Periodic signals --

f(t+T) = f(t) Period = T (seconds)

Frequency = 1/ Period

(“cycles” / sec. = Hertz (Hz)

Radian frequency:

(radians/sec.)2 f

SIGNALS and SYSTEMS

Reference: Signals, Systems and TranformsLeland B. JacksonAddison Wesley

SIGNALS and SYSTEMS

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

2

0 0

0

2

0 0

0

1( )cos(2 ) ( )

1( )sin(2 ) ( )

n

n

a x t nf t d t

b x t nf t d t

00

0 0

0 00 0

1

2

1 2( ) 2 2

fT

t f t

d t f dt dt dtT T

is the “fundamental frequency”

0 01

1( ) cos(2 ) sin(2 )

2

N

n i nn

x t a a nf t b nf t

Fourier Series

Integration limits: when 0 2t , then

0 0 0

2 2 1

2 /t

T T

so we get:

0 01

1( ) cos(2 ) sin(2 )

2

N

n i nn

x t a a nf t b nf t

0

0

00 0

00 0

2( )cos(2 )

2( )sin(2 )

T

n

T

n

a x t nf t dtT

b x t nf t dtT

Fourier Series

Euler:

0 01

1( ) cos(2 ) sin(2 )

2

N

n i nn

x t a a nf t b nf t

2 cos(2 ) sin(2 )ij f ti ie f t j f t

02( ) jn f tn

n

x t c e

02( ) jn f t

in

x t c e

Fourier Series

02( ) jn f tn

n

x t c e

0

0

0

2

02

1( )

T

jn tn

T

c x t e dtT

We can show2 2

n n nc a b 1tan ( / )n nb a ;

recall that2 2 1cos( ) sin( ) cos( tan ( ))

ba b a b

a

Phasors:

Phasors

2 2a b

a

b

References Stallings, W. Data and Computer Communications

(7th edition), Prentice Hall 2004 chapter 1 Web site for Stallings book

http://williamstallings.com/DCC/DCC7e.html Web sites for IETF, IEEE, ITU-T, ISO Internet Requests for Comment (RFCs) Usenet News groups

comp.dcom.* comp.protocols.tcp-ip