Transcript Evolution of Data Networks

ELEN 602 Computer Communications & Networks
Instructor: Narasimha Reddy
Contact: [email protected], 845-7598, 320 F Wisenbaker
Textbook: Communication Networks by Leon-Garcia & Widjaja
Class notes available: http://ee.tamu.edu/~reddy/ee602_02.html
Teaching Assistant/Grader: To Be Announced
TA Office Hours: To Be Announced
Grading: Homeworks: 30%, Tests: 60%, Project: 10%
ELEN 602 Lecture 1
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Some Communication Networks
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Flying Pigeons
Marathon Runners
Reflecting Mirrors
Telephone
Telegraph
Cable TV
Internet
Satellite-based cable/telephone
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Telephone Functioning
1.
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.
ELEN 602 Lecture 1
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Web Access Steps
1.
2.
3.
4.
5.
6.
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.
ELEN 602 Lecture 1
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Realplayer example
Copyright © 1995-2000, RealNetworks, Inc. All rights reserved. RealPlayer is a trademark
of RealNetworks, Inc.
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Steps in Communication - US Mail
• Compose the letter -- based on the user/office/personal
• Package it for transport -- put it in an envelope, address (to
and from) it, leave it in a well-known port (mailbox)
• Postman picks up the mail, local post office sorts it for
further transport
• Number of letters may be bundled and transported to
remote city
• Remote post office sorts them by local addresses, postman
delivers it to the To-mailbox
• Remote person picks up the mail, receives the message.
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Work in generic communication
• Addressing -how to address the comm. for transport
– telephone numbers, US Mail addresses, IP addresses
• Name-to-address translation -- phone directory, address
book, DNS name resolution
• Routing -- which way to send a piece of comm. to reach B
from point A
– East-coast US mail may go to Houston -New York
• Transport -- how to actually move the data/mail/bits/
– Trucks/planes with US mail, telephone wires, LAN
– Multiplexing of different pieces of communication
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What you will learn in this class?
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Addressing (IPv4 and IPv6)
Routing (routing protocols)
Name resoultion (DNS)
Transport
– Physical media (Ethernet, SONET, FDDI, ATM etc.)
– Multiplexing (switches/routers)
– Queuing theory -(delay/loss analysis)
– Protocols (TCP/IP)
• Some Applications - (http/email etc.)
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t1
t0
Network
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(a) A switch provides the network to a cluster of users
Network
Access network
(b) A multiplexer connects two access networks
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1*
a
(a)
2
b
4
3
A
c
Metropolitan network A
consists of access
subnetworks a, b, c, d.
d
Metropolitan
(b)
A
a
b
g
ELEN 602 Lecture 1
National network
consists of regional
subnetworks a, b, g.
Metropolitan network
A is part of regional
subnetwork a.
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Transmission capacity (bits/second)
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
ELEN 602 Lecture 1
1975
2000
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(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
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Toll
Tandem
Tandem
CO
CO
CO
CO
CO
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(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
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Poll to terminal
C
Response from terminal
T
T
T
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Host
Mux
.
.
.
T
T
Address
Info
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Host
San
Francisco
New York
City
T
T
Chicago
T
Atlanta
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AMES
McCLELLAN
UTAH
BOULDER
GWC
CASE
RADC
ILL
CARN
LINC
USC
AMES
MIT
MITRE
UCSB
STAN
SCD
ETAC
UCLA
RAND
TINKER
BBN
HARV
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NBS
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transceivers
(a)
  
 

(b)
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net 3
G
net 1
G
G
G
net 2
net 5
G
net 4
G
G = gateway
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Technology
Standards
Market
Regulation
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Capability
Capability
Third type of
invention
Second type of
invention
Initial class of
invention
(a)
time
(b)
ELEN 602 Lecture 1
time
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