Homenet Ews

Internet & Home networking

Prof. J. Won-Ki Hongjwkhong@postech.ac.kr

Dept. of Computer Science & Engineering

POSTECH

Internet & Home Networking

Contents

Data Communication Network

Internet & World Wide Web

Home Networking

Data Communication Network

• 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?

Brief History of Computer Networks

• 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?

A Communication Model

1 2 3 4 5 6

Input Information

Input data gor signal

Transmittedsignal

Receivedsignal

Output data g’or signal

g’(t) ’

OutputInformation

TransmissionmediumTransmitterInput

DeviceOutputDeviceReceiver

Source System Destination System

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

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

Addressing: indicating the identity of the intended destinationRouting: 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

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

• Communications Media– twisted pairs

– coaxial cables

– line-of-sight transmission: lasers, infra-red, microwave, radio

– satellite links

– fiber optics

– Power line

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

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

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

POSTECH LAN (1998.6)

POSTECH LAN (1999. 3)

• 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

• 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

Internet in Korea (1995.5)

Internet in Korea (1999.6)

Growth of Internet Users in Korea

Growth of Internet Hosts in Korea

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

• 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

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

• 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

Application

Presentation

Session

Transport

Network

Data Link

Physical

OSI Stack

Application

Presentation

Session

Transport

Network

Data Link

Physical

OSI Stack

Application

Presentation

Session

Transport

Network

Data Link

Physical

OSI Stack

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.

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.

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

Relation Between Layers at an Interface

ICI SDU

Header

Layer N

Interface

Layer N + 1

Layer N entitiesexchange N-PDUs in their layer N Protocol

SAP = Service Access PointIDU = Interface Data UnitSDU = Service Data UnitPDU = Protocol Data UnitICI = Interface Control Information

• 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).

• 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.

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

Application

Operating System

Controller

Physical

The AnarchisticNetwork Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

The OSI Model

Application

Transport

Network

Data Link

Physical

The TCP/IP Model

the network

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

• 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

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

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

Internet and World Wide Web

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.

Definitions

• A network of networks

• Based on TCP/IP (Transmission Control Protocol/Internet Protocol)

• A variety of services and tools

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

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

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

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.

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

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

• 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

• 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.

• 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

Home Networking

Definition

the collection of technologies and services that make it possible to connect• PCs

• Network devices

• Appliances

• Security equipment

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 networkingGolden age of 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/IPThe Web and TCP/IP

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 MegaTrend: From one Internet device per home to device per home to MANYMANY

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

Connecting Everything

NetworkNetworkcameracamera

CommunicationsCommunicationsand controland control

HomeRFHomeRF

HubHub

Power linePower line

networknetwork

HomePNAHomePNAPhone line networkPhone line network

Public networksPublic networksPSTN, InternetPSTN, Internet

PrinterPrinter

CameraCamera ScannerScanner

Web Web phonephone

IEEE 1394IEEE 1394

EntertainmentEntertainmentCenterCenter

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…

Home Network Architecture

End to endEnd to endbroadbandbroadband

Public networksPublic networksPSTN, InternetPSTN, Internet

CameraCamera PrinterPrinter

New media supportNew media support

Internet Internet ConnectionConnectionSharingSharing

Architecture for The Future

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

Leveraging Web Leveraging Web technologiestechnologies

Internet exists and it worksInternet exists and it works

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

Web for “Devices”

TCP/IP stackTCP/IP stack 30 ~ 90K bytes code30 ~ 90K bytes code30 ~ 80K gates on silicon30 ~ 80K gates on silicon

Embedded web Embedded web serverserver

20 ~ 80K bytes code20 ~ 80K bytes code30 ~ 90K gates on silicon30 ~ 90K gates on silicon

Ethernet, 1394 or Ethernet, 1394 or PPP/async driverPPP/async driver Device specific sizeDevice specific size

Device or serviceDevice or servicespecific code specific code Application specific sizeApplication specific size

Example Web Devices

Refrigerator PC: Sharewave

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

Example Web device

Interactive TV from Spyglass

Example Web devices

Internet Router from POSTECH

Conclusion

Homenet Ews

communication medium

internet home networkingprof

single communication

timing of signals

sight transmission

transmission errors

transmission facility

appropriate paths

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