Networks Standardisation & Protocols

Learning Objectives Explain the advantages of standardisation and describe some areas of standardisation such as file formats, ISDN, OSI model and its use together with communications protocols.

Standardisation Needed so that computer systems can talk to each other. Without standards there would be a proliferation of formats and it would not be possible to move data electronically.

Character set The symbols that a computer (software) can recognise which are represented by binary codes that the computer understands.

Character Representation Over the years different computer designers have used different sets of binary codes for representing characters in a character set. This has led to great difficulty in transferring information from one computer to another. i.e. which binary code represents each character. i.e. which binary code represents each character. So we needed a standard character set. The most common one is ASCII. The most common one is ASCII.

Common File Formats Text files (Text Only) Hold individual characters (with no formatting) as ASCII code. Hold individual characters (with no formatting) as ASCII code. Used to transfer data between application packages. Used to transfer data between application packages. Rich Text Format files (RTF) Complex format used to store data from a word processor. Complex format used to store data from a word processor. Includes information about fonts, sizes, colour and styles. Includes information about fonts, sizes, colour and styles.

Text Only V RTF A document saved as a text only file is smaller in memory size and so faster to transmit than the same document saved as a RTF file. A text only file is likely to be compatible with another user’s software and so is more likely to be readable at the destination.

Common File Formats Comma Separated Variable files (CSV) Used to transfer tabular data between applications. Used to transfer tabular data between applications. Each field is separated by a comma. Each field is separated by a comma. Tab Separated Variable files Used to transfer tabular data between applications. Used to transfer tabular data between applications. Each field is separated by a tab character. Each field is separated by a tab character.

Common File Formats Picture files Used to represent pictures in digital format. Used to represent pictures in digital format. Many different formats such as BMP, JPEG, GIF & MPEG. Many different formats such as BMP, JPEG, GIF & MPEG. JPEG & MPEG involve compression techniques that allow pictures to be quickly transferred over the Internet. JPEG & MPEG involve compression techniques that allow pictures to be quickly transferred over the Internet.

Common File Formats Sound files As with picture files, there are many different formats that store sound in digital form. As with picture files, there are many different formats that store sound in digital form. e.g. WAV, MP3, AVI e.g. WAV, MP3, AVI Storing sound requires a great deal of memory. Storing sound requires a great deal of memory. Video Files Different formats for storage of video moving images. Different formats for storage of video moving images. e.g. WMV, MPG e.g. WMV, MPG Storing moving video images requires a huge amount of memory. Storing moving video images requires a huge amount of memory. MPG involve compression techniques that allow video to be quickly transferred over the Internet. MPG involve compression techniques that allow video to be quickly transferred over the Internet. MPG has also allowed the introduction of many more television channels through a more efficient use of the bandwidth available over the media used. MPG has also allowed the introduction of many more television channels through a more efficient use of the bandwidth available over the media used.

Standardisation Of Software Microsoft Office is the standard software suite as it used by 90% of computer users.

Common Communications Media Methods of transferring data over a wide area. Most common is ISDN (Integrated Services Digital Network) connections. Used as worldwide standard format by telephone companies to connect digital exchanges. Used as worldwide standard format by telephone companies to connect digital exchanges. Most homes use analogue connections to the local exchange but after that ISDN. Most homes use analogue connections to the local exchange but after that ISDN.

ISDN User Digital Exchange Digital links Analogue links

Protocol A set of rules to allow communication between devices / computers / machines. Each rule standardises a particular aspect of communication e.g. bit rate etc..

Layered Protocols Protocols can be divided into subdivisions or ‘layers’ to allow manufacturers of peripherals and software programmers to design for a particular layer. If the whole protocol was treated as a single entity then every time a small change is made (e.g. hardware/software is changed) the whole protocol would need to be altered. If the whole protocol was treated as a single entity then every time a small change is made (e.g. hardware/software is changed) the whole protocol would need to be altered. However, in a layered protocol, individual layers can be altered (e.g. hardware/software is changed) without altering other layers. However, in a layered protocol, individual layers can be altered (e.g. hardware/software is changed) without altering other layers.

OSI (Open Systems Interconnection) The standard layered protocol we use today. It is a standard description for communications and computer network protocol design. It is a standard description for communications and computer network protocol design. Application HTTP (HyperText Transfer Protocol), Presentation Data representation and encryption Session Inter-host communication Transport TCP (Transmission Control Protocol) e.g. Odd / Even Parity, Check Sums etc.. Network IP (Internet Protocol) Data Link Physical addressing (MAC & LLC) Physical Media, signal and binary transmission e.g. Serial / Parallel transmission, Bit Rate, …

HTTP (HyperText Transfer Protocol ) A standard communications protocol for the transfer of information on intranets and the World Wide Web.

TCP/IP TCP (Transmission Control Protocol) A protocol for the transmission of data and provides error checking and flow control. A protocol for the transmission of data and provides error checking and flow control. IP (Internet Protocol) A protocol for source and destination addressing, sequencing and routing. A protocol for source and destination addressing, sequencing and routing.

Disadvantages of Standardisation Too much power in hands of those whose standards are adopted. Stifles innovation. Puts those with no standard systems at a disadvantage.

Plenary Explain the need for standardisation in modern computer systems and give examples where standardisation is important.

Plenary Standardisation necessary so that computer systems can talk to each other. Common file formats. Common communications media like ISDN. Common communication protocols like http. Use of layered protocols (OSI or TCP/IP are the standard ones we use today) to allow manufacturers to design for a particular layer. Standardisation of software (use of Office by 90% of computer users). Standard character sets.

Plenary What is a protocol?

Plenary A set of rules to allow communication between computers.