Transcript Communications Networks: Fundamental Concepts and Key

Communications Networks:
Fundamental Concepts and Key
Architectures
Leon-Garcia and Widjaja
University of Toronto
Outline of Course
• C1 Networks and Services Survey
– Appendix A1 Queues
– Online tutorial Probability
• C2 Applications and Layered Architectures
– (Skip 2.4 Berkeley API)
• C3 Digital Transmission Fundamentals
• C4 Transmission Systems
– (Skip 4.4, 4.6, 4.7 on telephone details)
Course Outline Continued
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C5 Peer-Peer Protocols
(C6 skip LANs) covered in CS487
C7 Packet Switching Nets
C8 TCP/IP
– (Skip 8.8)
C1 Intro to Nets
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1.1 Networks and Services
1.2 Approaches to Network Design
1.3 Internet and Packet Switching
1.4 Factors in Network Evolution
1.1 Networks and Services
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Definition of network
TV Broadcasting
Telephone Service PSTN POTS
Cellular Phones
Email
Web
Video on Demand
1.2 Approaches to Network
Design
• Network Functions and Topology
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Terminals
Connectivity
Switches
Access Network
Multiplexers
LANS, Metropolitan net, WANs
Topologies
Addressing (Flat vs. Hierarchical)
Traffic Control
Network Management
(a) A switch provides the network to a cluster of users
Network
Access network
(b) A multiplexer connects two access networks
Figure 1.7
Message, Packet and Circuit
Switching
– Telegraph Network (Message)
– Internet (Packet)
– Telephone Network (Circuit)
• Table 1.1 Not Functions but rather
dimensions of classifying nets
Telegraph
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Sam F. B. Morse Baltimore to DC 1837
Binary representation
Relay Hardware, Relay, MD
Message Switching
Multiplexing Edison, Bell
Teletype Networks
Telephone
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Alexander Graham Bell 1876 Boston
Circuit Switching Hierarchy
Analog Transmission
Grafting of Digital Traffic
Huge Investment, particularly local drops
(last mile)
(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
Figure 1.10
Toll
Tandem
Tandem
CO
CO
CO
CO
CO
Fig. 1.11 Part of the Hierarchy for Telephone Switching
Figure 1.11
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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.
Telephone call set up
Figure 1.1
Internet
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Packet Switching
Taste of History SAGE, SABRE, ARPANET
Terminal Oriented Nets
Multiplexers
LANs flat addressing Ethernets
WAN Routers
TCP/IP Protocol Suite
(
(a) Time-Shared Computers & Cables for Input
Devices
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C
T
T
(b) Dial In
C
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T
T
T
Modem
Pool
PSTN
Modem
T
T = terminal
Figure 1.12
Poll to terminal
C
Response from terminal
T
T
T
T
Sharing a multidrop line
Figure 1.13
Ethernet Local Area Network (LAN)
transceivers
  
 

(a)
Original bus version
Current star version
Figure 1.17
AMES
McCLELLAN
UTAH
BOULDER
GWC
CASE
RADC
ILL
CARN
LINC
USC
AMES
MIT
MITRE
UCSB
STAN
SCD
ETAC
UCLA
RAND
TINKER
BBN
HARV
NBS
ARPANET about 1972
Figure 1.16
An internetwork, not the
Internet, necessarily
net 3
G
net 1
G
G
G
net 2
net 5
G
net 4
G
G = gateway
Figure 1.18
Retrieving a Web page over the Internet
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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.
Figure 1.4
1.3 Key Factors in Network
Evolution
• Rapid Improvement of Communications
and Computer Performance – “Rapid
Technology Push”
• “Market Pull”
• Regulation
• Standards
Transmission capacity (bits/second)
Evolution of network capacity
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
1975
2000
Figure 1.9
Factors involved in success of a new service
Technology
Standards
Regulation
Market
Figure 1.19