NETWORK STANDARDS

Standards allows the combination of products from different manufacturers to work together.

Standards are defined based on either operation of computers or manufacturers of the devices.

Basic recommended standards; Closed system V-series Recommendation X-series Recommendation I-series Recommendation Open System / Open System Interconnection (OSI)

Environment

Most of the early computer devices manufactured by different vendors tends to communicate with their own brand only.

IBM

IBM

APPLEX

Connection between device & modem that is connected to Public Service Telephone Network (PSTN).

PSTN is a collection of public networks based on voice in the entire world.

The device is called Data Terminal Equipment (DTE).

PSTN

ModemDTE

A set of data & interface communication protocol to connect DTE to public data network is recommended in X-series.

PSTNDTE DTE

A set of data & interface communication protocol to connect DTE to the Integrated Services Digital Network (ISDN) lines.

Enables data & voice to be sent using digital connection from end-to-end.

ISDNDTE DTE

Theoretical representations of what happens when 2 computers communicate with each other.

Uses structuring technique known as layering & communication functions are partitioned into these layers.

Open Systems Interconnection – a standard reference model consisting of documents by ISO & CCITT merged together.

Application Layer

Presentation Layer

Network Layer

Data Link Layer

Physical Layer

Session Layer

Transport Layer

Host layers

Media layers

7th layer of the OSI Model & facilitates the communication between software application & lower network services.

Relates to the services that directly supports user applications.

Layer provides means for the user to access information on the network through an application.

Protocols supporting application layer; File Transfer Protocol(FTP) – used for

uploading/downloading files from & to FTP server Simple Mail Transfer Protocol(SMTP) – used by most of the

email software to send/receive email from email server. Hypertext Transfer Protocol(HTTP) – used by web browser

to send/receive information over internet to web server.

Function; to define the format used to exchange data among networked computers. (works as translator for the data over the network)

When dissimilar systems like IBM, APPLE & SUN computer communicate, a certain amount of translation & byte re-ordering is needed & it is done by this layer.

Different applications uses different data encoding & compressing techniques, & presentation layer does the encoding.

This layer responsible for converting protocols, translating & encrypting the data (also converting character set & expanding graphics commands)

Function: to coordinate & maintain the communication between 2 computers over a network. Synchronizes user tasks by placing check points in

the data stream. The checkpoints breaks the data into smaller groups

for error checking. So if the network fails, only data after the last check point have to be re-transmitted.

Also sets the terms of communication by deciding which computer will communicate first (priority) & how long it can communicate (duration) over the network.

Provides additional connection level beneath the session layer.

Ensures packets are delivered error free, in sequence & without losses / duplication. (verified, reliable & error free)

Large data units received from session layer are broken down into smaller units called segments = process called segmentation.

Also handle flow control & error handling of data. Transport layer protocols: Transmission Control

Protocol(TCP), Sequenced Packet Exchange(SPX) & User Datagram Protocol(UDP)

Function to translate network addresses into their physical counterparts & decide how to route data.

Each computer connected to network has a unique address.

Addressing = a system for assigning unique identification numbers to devices on a network.

It manages the switching & routing of data packets as well as handles the traffic problems.

Ex network layer protocol: IP, IPX

Controls the electrical impulses that enter & leave the network cable.

Sends data frames from the network layer to physical layer.

Data frame = an organized, logical structure in which data can be placed.

Responsible for providing error-free transfer of these frames from one computer to another through physical layer.

Accepts frames from the data link layer & generate voltage to transmit signals.

Signals are made of electrical impulses that, when issues in a certain pattern, represents information.

Hardware oriented & deals with all aspects of establishing & maintaining a physical link between communicating computers.

Also defines how cables are connected to Network Interface Card (NIC) (ex, how many pins in the connector & the function of each pin)

Also defines transmission technique that will be used.

OSI LAYER FUNCTION

Application Interaction at the user / application level

Presentation Translation of data

Session Maintains a session between computers on a network

Transport Makes sure that transmissions are received

Network Manages addressing & routing of the packets

Data Link Physical addressing of packets & error correction

Physical Manages the connection to the media.

Set of standards, rules that led networked computers communicate / share information over network such as Ethernet or Token ring.

Commonly used protocols; TCP/IP IPX NetBIOS/NetBEUI

Consists of 2 protocols: Transmission Control Protocol(TCP) & Internet Protocol(IP)

Defines how network data is addressed from a source to destination & data arrangement after its arrived.

Operates at network layer TCP = transport layer : manages relationship

between computers. Datagram/packet is a chunk of IP data at TCP layer.

APPLICATION

PRESENTATION

SESSION

TRANSPORT

NETWORK

DATA LINK

PHYSICAL

APPLICATION

TRANSPORT

INTERNET

NETWORK INTERFACE PHYSICAL

Packet A collection of data sent through a network & usually

refers to data unit that is sent to any OSI layer

Datagram Refers to network layer’s data unit such as IP datagram

Frame Refers to data unit that is brought by data link layer.

IPX can pass through any network topology. It is self configurable & builds address of computer

system from Netware address & Physical/Media Access Control(MAC) address. (network card’s)

When network is linked physically, IPX will automatically configure & quickly start delivering data packets. (no need for different network addresses for computers)

Disadvantage: IPX is broadcast based protocol and NOT part of TCP/IP which is the prime protocol for internet! So IPX cannot be used for Internet traffic

APPLICATIONPRESENTATION

SESSION

TRANSPORT

NETWORK

DATA LINK

PHYSICAL

Netware Core Protocol

Service Advertising

Protocol

Routing Information

Protocol

IPX

Medium Access Protocols(Token Ring, Ethernet, ARCnet)

Designed for small LAN network & not suitable for WAN network since it cannot pass between 2 networks unless routers are connected them both.

Advantages : uses alphanumerical name which is easily understood by human.

ANNA

SHAM

Sending computer

Receiving computer

International Organization for Standardization (ISO) World’s largest developer of standards. Primal activity is the development of technical

standards ISO is a network of national standard institutes of 157

countries with a central secretariat in Geneva. OSI Reference Model was drafted by ISO. www.iso.org

Internet Engineering task Force (IETF) Large open international community Community includes network designers,

operators, vendors, researches & those who are concerned with the evolution of Internet architecture.

Institution Of Electrical & Electronics Engineering (IEEE) Non profit organization & world’s leading

professional association for the advancement of technology.

More than 365000 members from over 150 countries.

Areas of interest : aerospace system, computers & telecommunications, electric power, consumer electronics, biomedical engineering etc.

www.ieee.org

International Telecommunication Union (ITU) An international organization within the United

Nations System where private & government sector coordinate global telecom networks & services.

The American National Standards Institute (ANSI) Develops & use voluntary consensus standards IN US &

represents the need & views of US stakeholders in standardization forums around the globe.

www.ansi.org