CONTENTS Network communications standards – Ethernet – TCP/IP Other network protocols – The 802.11 standard – Wireless application protocol Questions
In order for devices to connect from different manufacturers over different networks, the networks must use similar techniques of transferring data. Network standards are developed by organisations such as the Institute of Electrical and Electronics Engineers (IEEE) to overcome incompatibility issues. A network standard defines guidelines that specify the way computers access the medium to which they are attached, the type of medium used, the speed of which data flows and the physical technology used.
A standard that defines how two network devices communicate is called a protocol. Manufacturers of hardware and software must design their products in accordance with the standards to ensure the device can communicate with the network. Standards are important in the IT industry as, without them, only devices from the same manufacturer would be able to communicate. Also allows for consistent interfaces which makes it easier for users to learn how to use new applications.
Ethernet A popular network standard that allows personal computers to contend for access to the network. A collision occurs if two computers attempt to send data at the same time and the computers must try resending the data. Based on bus topology but can be wired in a star pattern. Most popular LAN standard due to it being relatively inexpensive and easy to install and maintain. Use cables to transmit data. Original Ethernet standard is slow compared to today’s standards.
Fast Ethernet -> transmits data and information at speeds of 100 Mbps (up to 10x faster than original standard). Gigabit Ethernet -> In use in many graphic-design studios. Provides an even higher speed of transmission ( up to 10x faster than Fast Ethernet). When a workstation needs to transmit, checks network to ensure it isn’t busy, then broadcasts a ‘packet’. The packet is received by all workstations on the network, but only the workstation it is addressed to will read it. If a collision occurs, network jams and the packets will be re-sent after a random amount of time.
TCP/IP Transmits data by breaking it up into packets and transmitting these over the internet. Important part of IP protocol is the IP address. IP addressing standard – four numbers between 0 and 255 divided by full stops – defines a mechanism to provide a unique address for each computer on a network. Each packet contains the data, recipient (destination) information, sender (origin) information, and sequence information used to reassemble the data at the destination.
Packets travel along the fastest available path, using devices called routers to avoid congestion and broken links on the way to the recipient’s computer. The technique of breaking a message into individual packets, sending the packets along the best available route, and reassembling the data, is referred to as ‘packet switching’.
Network communications protocols package the messages from the client computers and send the packets across the network. The protocol takes care of the addressing, routing and the correct and accurate delivery of the packets. Common protocols include: Apple File Protocol (AFP), Microsoft’s NetBIOS Extended User Interface (NetBEUI), and Novell’s Sequential Packet Exchange and Internetwork Packet Exchange (SPX and IPX).
The 802.11 standard Developed by IEEE. Specifies how two wireless computers or devices communicate via radio waves with each other. Uses techniques similar to those of the Ethernet standard. Easily integrated into existing wired Ethernet networks. Range of wireless communications – up to 300 metres in open areas outside, approx. 50 metres inside buildings. Popular in locations where there is no existing wired system, or construction of building makes it difficult to add a wired network.
Wireless application protocol Wireless application protocol (WAP) allows wireless mobile devices to access the Internet and its services. Uses a client-server network. The wireless device contains the client software, which connects to Internet service provider’s (ISP) server. WAP-enabled devices include phones, pagers, notebooks etc.
Questions Why do manufacturers of network hardware and software follow standards? Briefly describe how an Ethernet network transmits data. In what situations would the TCP/IP protocol be most useful? Explain what the term ‘packet switching’ means. What network transmission standard would be useful for an office located in a building with solid stone walls?