Title: Internet
1Internet Home networking
- Prof. J. Won-Ki Hong
- jwkhong_at_postech.ac.kr
- Dept. of Computer Science Engineering
- POSTECH
2Contents
- Data Communication Network
- Internet World Wide Web
- Home Networking
3- Data Communication Network
4Brief History of Computer Networks
- 1960s How can we transmit bits across a
communication medium efficiently and reliably? - 1970s How can we transmit packets across a
communication medium efficiently and reliably? - 1980s How can we provide communication
services across a series of interconnected
networks?
5- 1990s 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?
6 A Communication Model
7 Common Communication Tasks
- Data encoding the process of transforming input
data or signals into signals that can be
transmitted - Signal generation generating appropriate
electro-magnetic 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
8- 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
9- 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
10 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
11- Communications Media
- twisted pairs
- coaxial cables
- line-of-sight transmission lasers, infra-red,
microwave, radio - satellite links
- fiber optics
- Power line
12 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
13- 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
14 Types of Communication Networks
- Local Area Networks (LANs)
- lt 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
15POSTECH LAN (1998.6)
16POSTECH LAN (1999. 3)
17- 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
18- 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), CANET,
NSFNET, KREONET, BoraNet, KORNET, INET, Internet
19Internet in Korea (1995.5)
20Internet in Korea (1999.6)
21Growth of Internet Users in Korea
22Growth of Internet Hosts in Korea
23 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
24- 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
25 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
26- 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
27 OSI Stack
OSI Stack
OSI Stack
Application
Application
Application
Presentation
Presentation
Presentation
Session
Session
Session
Transport
Transport
Transport
Network
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
28- Functions of the OSI Layers
- 1. Physical layer responsible for the
electro-mechanical 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.
29- 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.
30- 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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32- 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).
33- 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.
34 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
35(No Transcript)
36 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
37- 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
38 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
39- 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
40- Internet and World Wide Web
41History 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.
42Definitions
- A network of networks
- Based on TCP/IP (Transmission Control
Protocol/Internet Protocol) - A variety of services and tools
43Network 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 todays computers are connected
via Internet
44Based 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
45Variety 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
46World 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.
47Web 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
48Web 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
49HTML
- 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
50HTTP
- 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.
51URL
- 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.addressport/path/filen
ame - ftp//ftp.postech.ac.kr/pub/welcome.txt
- file///C/My Documents/resume.htm
- newshan.protocol.http
- telnet//vision.postech.ac.kr
- http//www.postech.ac.kr/index.html
52 53Definition
- the collection of technologies and services that
make it possible to connect - PCs
- Network devices
- Appliances
- Security equipment
54Why 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
55Technology 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
56Analogous 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
57Roles 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
58Connecting Everything
59Challenges 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
60Home Network Architecture
Public networks
PSTN, Internet
Camera
Printer
61Architecture 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
62TCP/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
63Web for Devices
Application specific size
64Example Web Devices
- Refrigerator PC Sharewave
65Example 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
66Example Web device
- Interactive TV from Spyglass
67Example Web devices
Internet Router from POSTECH
68Conclusion