Internet & Home networking
Prof. J. Won-Ki Hong
jwkhong@postech.ac.kr
Dept. of Computer Science & Engineering
POSTECH
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Internet & Home Networking
Contents
Data Communication Network
Internet & World Wide Web
Home Networking
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Internet & Home Networking
Data Communication Network
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Internet & Home Networking
Brief History of Computer Networks
• 1960’s – “How can we transmit bits across a
communication medium efficiently and reliably?”
• 1970’s – “How can we transmit packets across a
communication medium efficiently and reliably?”
• 1980’s – “How can we provide communication
services across a series of interconnected
networks?
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Internet & Home Networking
• 1990’s – “How can we provide high-speed,
broadband communication services to support
high-performance computing and multimedia
applications across the globe?”
• 2000's – What do you think will dominate in the
next 10 years?
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A Communication Model
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Sender
Input
Information
m
Input
Device
3
Input data g
or signal
g(t)
Transmitted
signal
s(t)
Transmitter
Source System
4
5
Received
signal
r(t)
Output data g’
or signal
g’(t)
’
Transmission
medium
Receiver
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Output
Information
m’
Output
Device
Receiver
1
Destination System
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Common Communication Tasks
Data encoding: the process of transforming input data or
signals into signals that can be transmitted
Signal generation: generating appropriate electromagnetic signals to be transmitted over a transmission
medium
Synchronization: timing of signals between the
transmitter and receiver ; when a signal begins and when
it ends; duration of each signal
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Internet & Home Networking
Error detection and correction: ensuring that
transmission errors are detected and corrected
Flow control: ensuring that the source does not
overwhelm the destination by sending data faster than
the receiver can handle
Multiplexing: a technique used to make more efficient
use of a transmission facility. This technique is used at
different levels of communication
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Addressing: indicating the identity of the intended
destination
Routing: selecting appropriate paths for data being
transmitted
Message formatting: conforming to the appropriate format
of the message to be exchanged
Security: ensuring secure message transmission
Systems management: configuring the system, monitoring
its status, reacting to failures and overloads, and planning
for future growth
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Internet & Home Networking
Communication Network
A communication network is a collection of devices
connected by some communications media
• Example devices are:
–
–
–
–
–
–
–
mainframes, minicomputers, supercomputers
workstations, personal computers
printers, disk servers, robots
X-terminals
Gateways, switches, routers, bridges
Cellular phone, Pager, TRS
Refrigerator, Television, Video Tape Recorder
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Internet & Home Networking
• Communications Media
– twisted pairs
– coaxial cables
– line-of-sight transmission: lasers, infra-red, microwave,
radio
– satellite links
– fiber optics
– Power line
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Internet & Home Networking
Network Structures
Point-to-Point Networks
• each communication line connects a pair of nodes
• a packet (or message) is transmitted from one node to
another
• intermediate nodes, in general, receive and store
entire packet and then forward to the next node
• also called “store-and-forward” or “pack-switched”
• some topologies: star, ring, tree
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Internet & Home Networking
Broadcast Networks
• have a single communication line shared by all
computers on the network
• packets sent by a host are received by all computers
• some topologies: bus, satellite, radio
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Internet & Home Networking
Types of Communication Networks
• Local Area Networks (LANs)
–
–
–
–
< a few km
high data transmission rate (at least several Mbps)
ownership usually by a single organization
e. g., Ethernet, IBM Token Ring, Token Bus, FDDI, Fast
Ethernet, ATM, Gigabit Ethernet
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POSTECH LAN (1998.6)
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POSTECH LAN (1999. 3)
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• Metropolitan Area Networks (MANs)
–
–
–
–
–
up to 50 km
fibre optics is a popular technology for MANs
may be private or public
may involve a number of organizations
e.g., cable TV networks (CATV), ATM networks
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Internet & Home Networking
• Wide Area Networks (WANs)
–
–
–
–
a few km to thousands of km
point-to-point networks (also called long-haul networks)
lower data transmission rate than LANs
fiber optics is a popular technology for MANs ownership
usually by more than a single organization
– e.g., ARPANET, MILNET (US military), CA*NET, NSFNET,
KREONET, BoraNet, KORNET, INET, Internet
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Internet in Korea (1995.5)
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Internet in Korea (1999.6)
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Growth of Internet Users in Korea
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Growth of Internet Hosts in Korea
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Computer Communication Architecture
• Computer Communication – the exchange of
information between computers for the purpose of
cooperative action
• Computer Network – a collection of computers
interconnected via a communication network
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• Protocol – agreement required between the
communication entities and consists of three
components:
Syntax: data format and signal levels
Semantics: control information for coordination and error
handling
Timing: speed matching and sequencing
• Communications Architecture – a structured set of
modules that implements the communication function
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ISO-OSI Reference Model
• International Standards Organization (ISO) – Open
Systems Interconnection (OSI) Reference model is a
framework for connecting computers on a network
• Motivation?
– to reduce the complexity of networking software
– as a step towards international standardization of the various
protocols
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• The main principles applied to the OSI layered
architecture are
– each layer represents a layer of abstraction,
– each performs a set of well-defined functions,
– implementation of a layer should not affect adjacent layers, and
inter-layer communication should be minimized
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OSI Stack
OSI Stack
OSI Stack
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
Physical
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Functions of the OSI Layers
1. Physical layer – responsible for the electromechanical interface to the communications media
2. Data link layer – responsible for transmission,
framing and error control over a single communications
link.
3. Network layer – responsible for data transfer across
the network, independent of both the media comprising
the underlying subnetworks and the topology of those
subnetworks.
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Internet & Home Networking
4. Transport layer – responsible for reliability and
multiplexing of data transfer across the network (over
and above that provided by the network layer) to the
level required by the application.
5. Session layer – responsible for establishing,, and
managing sessions between cooperating applications.
6. Presentation layer – responsible for providing
independence to the application process from
differences in data representation (syntax).
7. Application layer – ultimately responsible for
managing the communications between applications.
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Internet & Home Networking
How Communication Takes Place Between the Layers
• communication takes place between peer entities.
• a layer provides services to the layer above it.
• services are available at SAPs (Service Access Points) –
analogous to telephone numbers and street addresses
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Relation Between Layers at an Interface
IDU
ICI
Layer N + 1
SDU
SAP
ICI
Interface
Layer N entities
exchange N-PDUs
in their layer N
Protocol
Layer N
SDU
SDU
SAP = Service Access Point
IDU = Interface Data Unit
SDU = Service Data Unit
PDU = Protocol Data Unit
ICI = Interface Control Information
Header
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• On the sending side:
– a layer receives a PDU (Protocol Data Unit) from the layer
above it, with some ICI (Interface Control Information) (such
as address, data size, etc.).
– the layer ads some PCI (Protocol control Information) to the
APDU and passes the enlarged PDU to the layer below along
with more ICI.
– A layer may also fragment a PDU into several smaller pieces to
be passed separately to the layer below (in this case, the peer
entity at the receiving end will reassemble the fragments).
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• At the receiving end:
– a layer receives a PDU from the layer below.
– The layer strips off the PCI added by its peer, and passes the
PDU to the layer above it.
– If the sending layer fragmented a PDU, its peer is responsible
for reassembling it before passing it up.
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Internet & Home Networking
Other Communication Models
The Anarchistic Network Model
• have been used mostly in PCs
The TCP/IP Model
• only 5 layers exist
• used mostly in Internet network applications
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Internet & Home Networking
The Anarchistic
Network Model
Application
The OSI Model
Application
Presentation
Operating
System
The TCP/IP Model
Application
Session
Transport
Network
Transport
Controller
Data Link
Data Link
Physical
Physical
Physical
Network
the network
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Internet & Home Networking
Communication Service Types
• Connection-oriented service
– modeled after the telephone system
– must establish a connection before use, and terminates the
connection when finished.
– FIFO guaranteed.
– the path from the sender to receiver is fixed.
– resources are pre-allocated at setup time
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Internet & Home Networking
• Connectionless service
– modeled after the postal system
– no connection required, but instead full addressing required in
each message
– FIFO not guaranteed.
– the path is not fixed
– resources are dynamically allocated
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Standards Organizations
ITU-T (International Telecommunication Union Telecommunications Sector) - formerly CCITT (International
Telegraph and Telephone Consultative Committee), a
committee within ITU, a United Nations agency, responsible
for X.25, X.21, X.400, X.500, X.700, X.900, etc.
ISO (International Standards Organization): ISO 8073
(connection-oriented transport protocol)
ANSI (American National Standard Institute)
IEEE (Inst. of Electrical and Electronics Engineers): IEEE 802
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Internet & Home Networking
IETF (Internet Engineering Task Force): TCP/IP, FTP, SNMP
W3C (World-Wide Web Consortium): HTTP, HTML, XML
ATMF (ATM Forum) - ATM related standards
TMF (TeleManagement Forum) - formerly known as NMF,
Network Management Forum
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Internet & Home Networking
Internet and World Wide Web
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Internet & Home Networking
History of the Internet
1969 - Researchers at four US campuses create the first hosts of the ARPANET
1971 - The ARPANET grows to 23 hosts connecting universities and research centers
1973 - The ARPANET goes international with connections to England and Norway
1982 - The term "Internet" is used for the first time and TCP/IP is created
1992 - Internet Society is chartered. World-Wide Web released by CERN.
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Internet & Home Networking
Definitions
• A network of networks
• Based on TCP/IP (Transmission Control
Protocol/Internet Protocol)
• A variety of services and tools
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Internet & Home Networking
Network of networks
a group of two or more networks that are :
• interconnected physically
• capable of communicating and sharing data with each
other
• able to act together as a single network
• virtually all of today’s computers are connected via
Internet
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Internet & Home Networking
Based on TCP/IP
TCP/IP enables the different types of machines on
separate networks to communicate and exchange
information.
TCP/IP is
•
•
•
•
A suite of protocols
Rules for sending and receiving data across networks
Addressing
Management and verification
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Internet & Home Networking
Variety of services or tools
The Internet offer access to data, graphics, sound,
software, text, and people through a variety of
services and tools for communication and data
exchange
•
•
•
•
•
•
E-Mail
Usenet
FTP
Gopher
Telnet
World Wide Web
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Internet & Home Networking
World Wide Web
• A way to provide and access information resources on
the Internet
• Using Web Browser & Web Server
• Based on HTML and HTTP
• Multimedia
– Hypertext "links" can lead to other documents, sounds, images,
databases (like library catalogs), e-mail addresses, etc.
• Non-Linear
– There is no top, there is no bottom. Non-linear means you do
not have to follow a hierarchical path to information resources.
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Internet & Home Networking
Web Browser
• a piece of software that acts as an interface between the
user and the Internet, specifically the World Wide Web
• The browser acts on behalf of the user. The browser:
– contacts a web server and sends a request for information
– receives the information and then displays it on the user's
computer
• The browser can be graphical or text-based and can
make the Internet easier to use and more intuitive
• The helper applications are automatically invoked by
the browser when a user selects a link to a resource that
requires them
• A Web browser can be used on most of computers
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Internet & Home Networking
Web Server
• Also known as HTTP Server or HTTP Daemon
• The repository of web pages of which types are HTML
and any application data with MIME type
• Listens for HTTP requests from the web browsers,
serves those requests
• Designed to communicate with web browsers using
HTTP protocol
• Typically runs on general purpose computer
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Internet & Home Networking
HTML
• consists of standardized codes,or "tags", that are used to
define the structure of information on a web page
• defines several aspects of a web page including heading
levels, bold, italics, images, paragraph breaks and
hypertext links to other resources.
• a sub-language of SGML (Standard Generalized
Markup Language) that defines and standardizes the
structure of documents.
• standardized and portable: A document that has been
prepared using HTML can be viewed using a variety of
web browsers, such as Netscape and Lynx
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Internet & Home Networking
HTTP
• the set of rules, or protocol, that governs the transfer of
hypertext between two or more computers.
• Based on Client/Server paradigm
• Convey variety of Internet resources: HTML documents,
text files, graphics, animation and sound
• HTTP also provides access to other Internet protocols,
among them:
–
–
–
–
File Transfer Protocol (FTP)
Simple Mail Transfer Protocol (SMTP)
Network News Transfer Protocol (NNTP)
etc.
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URL
•
•
•
•
a standardized addressing scheme for Internet resources
used to link documents on the Internet
the browser knows where to go to get the document
basic format of an URL
type-of-resource:// domain.address:port/path/filename
–
–
–
–
–
ftp://ftp.postech.ac.kr/pub/welcome.txt
file:///C|/My Documents/resume.htm
news:han.protocol.http
telnet://vision.postech.ac.kr
http://www.postech.ac.kr/index.html
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Home Networking
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Internet & Home Networking
Definition
the collection of technologies and services that make
it possible to connect
•
•
•
•
PCs
Network devices
Appliances
Security equipment
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Internet & Home Networking
Why now?
Building “Internet” into consumer products is now possible
• Standardization has occurred
• Costs are low
Low-cost, high-speed LAN and routers
• Ethernet, IEEE 1394, Phone Wire, PLC, RF, etc.
• Video rate networks - IEEE 1394,Gigabit Ethernet
Modem and broadband networking are becoming ubiquitous
Golden age of networking
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Internet & Home Networking
Technology Enablers
ADSL and HFC (cable) networks
• Enable broadband Internet to the home
LANs, power line carrier, phone line networks, and wireless
• Enable ubiquitous connectivity
Internet connection sharing
• Brings the Internet to everything in the home
The communications software infrastructure has been
determined:
The Web and TCP/IP
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Internet & Home Networking
Analogous History
•
•
•
•
Single to multiple cars per family
One to multiple phones per household
Multiple phone lines per house
One to multiple TVs per house
MegaTrend: From one Internet
device per home to MANY
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Internet & Home Networking
Roles for Home Networking
Data
• Extension of current use of Internet by PDAs, tablets,
multiple PCs
Communications
• Telephony, videophone, chat, conferencing
Entertainment
• Games, TV, high-fidelity audio
Control
• Lights, HVAC, security, appliances
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Internet & Home Networking
Connecting Everything
Public networks
PSTN, Internet
Network
camera
HomePNA
Phone line network
Power line
network
Hub
Web
phone
Printer
IEEE 1394
HomeRF
Communications
and control
Camera
Entertainment
Center
Scanner
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Internet & Home Networking
Challenges for deployment of home network
Ease of installation
• There are no Net admins at home…
Network configuration has to be automatic
• There are no Net admins at home…
Network health and recovery
• There are no Net admins at home…
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Internet & Home Networking
Home Network Architecture
Public networks
PSTN, Internet
Internet
Connection
Sharing
End to end
broadband
New media support
Camera
Printer
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Architecture for The Future
Leveraging Web technologies
Great standards exist today
• IETF: TCP/IP, DNS, DHCP, HTTP, SSL, LDAP, IPSEC
• W3C: HTML, XML
Great services exist today
• Today: eCommerce, search
• Early Stages: Internet audio/video,
IP Telephony - much like early 1950s TV
• Billions of Web hits served daily
Internet exists and it works
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TCP/IP and Web is the software infrastructure
Web is evolving
• HTTP v1.1 for performance improvements
• XML extends Web for software applications
– “Pages” can now be simply data
– Internet Explorer 5.0 has XML support
Easy to wrap existing programs/tools/systems in Web
• Programming language neutral
• Contents neutral
• Operating system neutral
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Internet & Home Networking
Web for “Devices”
Device or service
specific code
Application specific size
Embedded web
server
20 ~ 80K bytes code
30 ~ 90K gates on silicon
TCP/IP stack
30 ~ 90K bytes code
30 ~ 80K gates on silicon
Ethernet, 1394 or
PPP/async driver
Device specific size
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Example Web Devices
Refrigerator PC: Sharewave
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Example Web Devices
Internet-on-a-chip design from Toshiba Semiconductor
• Features:
–
–
–
–
Network Stack - TCP, IP, UDP and PPP
General Sockets - 4 - Email - SMTP, POP3 and MIME
Web - HTTPv1.0 and HTMLv3.2 (text only)
Japanese and English character support
• Interfaces:
–
–
–
–
CPU Interface (Generic 80x86 CPU Interface)
SRAM Interface
Physical Layer Interface (RS232C & parallel port)
Decoder Interface
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Example Web device
Interactive TV from Spyglass
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Example Web devices
Internet Router from POSTECH
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Conclusion
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