Transcript
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 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 4
-- Application Layer (rlogin, ftp, SMTP, POP3, IMAP, HTTP..) -- Transport Layer(a.k.a Host-to-Host)
Level 3 Level 2
(TCP, UDP, ARP, ICMP, etc.) -- Network Layer (a.k.a. Internet) (IP) -- (Data) Link Layer / MAC sub-layer
Level 1
(a.k.a. Network Interface or Network Access Layer) -- Physical Layer
Level 5
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 telephoneswitching 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
UC CENIC January 2009
http://doc.cenic.org/tools/topology_map.pl?network=uc
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)
f 0 1/ T0
SIGNALS and SYSTEMS Periodic signals --
f(t+T) = f(t)
Period = T (seconds)
Frequency = 1/ Period (“cycles” / sec. = Hertz (Hz)
Radian frequency:
2 f
(radians/sec.)
SIGNALS and SYSTEMS Reference: Signals, Systems and Tranforms Leland B. Jackson Addison 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 N 1 x(t ) a0 an cos(2 nf 0t ) bi sin(2 nf nt ) 2 n 1
an bn
1
1
2
x(t ) cos(2 nf t )d ( t ) 0
0
0
2
x(t ) sin(2 nf t )d ( t ) 0
0
0
1 f0 T0
is the “fundamental frequency”
0t 2 f 0 t 1 2 d (0t ) 2 f 0 dt 2 dt dt T0 T0
Fourier Series N 1 x(t ) a0 an cos(2 nf 0t ) bi sin(2 nf nt ) 2 n 1
Integration limits: when 0t 2
2
2 1 t 0 2 / T0 T0
,
then
so we get:
2 an T0 2 bn T0
T0
x(t ) cos(2 nf t )dt 0
0
T0
x(t ) sin(2 nf t )dt 0
0
Fourier Series N 1 x(t ) a0 an cos(2 nf 0t ) bi sin(2 nf nt ) 2 n 1
x(t )
ce
n
jn 2 f 0t
n
x(t )
Euler:
e
j 2 f i t
ce
n
jn 2 f 0t
i
cos(2 fi t ) j sin(2 fit )
Fourier Series
x(t )
ce
n
1 cn T0
jn 2 f 0t
n
T0 2
x(t )e
jn0t
dt
T0 2
We can show
cn a b 2 n
2 n
;
tan (bn / an ) 1
recall that
b a cos( ) b sin( ) a b cos( tan ( )) a 2
2
1
Phasors:
a
b a b 2
Phasors
2
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
