Computer networks for the home

Transcription

1 Technical paper Computer networks for the home Computer networks for the home An overview This paper gives information about current and emerging technologies for networking computers in the home. It is worth noting that much of the information here would also be relevant to schools wishing to create a small network or add a small number of devices to their existing network. In recent years, there has been an upsurge in the use of computers and computer devices in the home and a rise in owning multiple devices. It is thus anticipated that the need for computer networks in the home is likely to increase. Creating a computer network at home provides many of the same advantages that a school or a small enterprise network would gain. Depending on the sort of network chosen, these gains can include: increased flexibility of internet access from various locations in the home internet access from two or more devices using a single internet access point. sharing peripheral devices such as printers sharing files between devices sharing applications from a main computer to other devices attached to the network using the network for home entertainment, such as gaming or accessing centrally stored music files. What types of home networks are there? There are many types of solutions to networking in the home. Some options include: wire your house or a room in your house with data cables install some form of wireless networking link your computers through the existing power cables link your computers through the existing telephone cable. How does a home network work? In general, the principle of a home network is no different to that of a network in an educational establishment. That is, two or more devices need to be able to interact with each other over a wired or wireless connection. The interaction between the devices could be simply to share the same internet connection or to share files and computer peripherals. Wireless networks There are a number of wireless (radio) technologies currently available. The family is widely promoted but a range of alternatives also exists. Wireless family many educational establishments now use equipment and this same technology could be used in the home. In brief, a wireless access card is needed for each device in order for it to be connected to the network. An 'access point' may also be needed if more than two devices want to share a peripheral or the same internet access. There are a number of different standards, which are covered in depth in Becta s Wireless Local Area Networks (WLANs) technical information sheet [ Becta page 1 of 10

2 Infrared networks this technology uses infrared light to maintain a connection between devices. It is a convenient technology as many devices, especially portable devices, have infrared ports built into them. There are two types of infrared networks: direct infrared and diffuse infrared. Direct networks Direct infrared networks need a clear line of sight between devices to make a connection. As most laptops already have infrared ports, a basic peer-to-peer network for such tasks as file sharing could be established by simply pointing the infrared devices towards each other. Diffuse networks Diffuse infrared technology operates by flooding an area with infrared light. The infrared signal bounces off the walls and ceiling so that a receiver in a device can pick up the signal regardless of the position of the device. This makes it more suitable than direct infrared for tasks where mobility of devices is an issue, and where multiple devices need to share the same network for tasks such as sharing peripherals and files. Unlike direct infrared, the data rates are contended and thus are shared between the number of devices needing simultaneous network access. Wireless touch screen a wireless touch screen is a wireless computer display screen that is sensitive to human touch allowing a user to interact with the computer by touching pictures or words on the screen. Recently this technology has been taken a stage further and now the touch screen can be carried from room to room while interacting with the main base PC via a wireless network link. This allows access to files stored on the home s main PC and the internet via the main PC when the wireless touch screen in located elsewhere in the home. Currently, wireless touch screens use Microsoft s technology and are marketed as Smart Displays. They are only available for use with Microsoft s XP operating system and only one touch screen can be used at a time with the base PC. It is important to note that currently if the smart display is in use, the base PC cannot be used independently. Personal area networks a personal area network (PAN) in a home networking context is the interconnection of devices within the range of an individual person and it typically uses wireless technology. (The use of short-range wireless technology is what distinguishes PANs from LANs.) For example, a person travelling with a laptop, a personal digital assistant (PDA), and a mobile phone could interconnect them via a short-range radio link. This kind of PAN could also be connected to the internet or other networks. There are several types of PAN solutions available one of the most widely available is based on the 'Bluetooth' specification. Bluetooth can be found built into many devices such as PDAs and laptops, but external adapters can also be purchased. It is possible to connect devices using a Bluetooth access point in a similar way to the technology, although data rates are much slower. HomeRF (home radio frequency) this technology doesn t require an access point. Each device needs a HomeRF card. This can either be attached via a USB cable or integrated into the device. Future development work on HomeRF products has now stopped and whilst it may be still be possible to buy these products in the UK it is unlikely that they will feature strongly in future home networks. Wired networks Wired networks obviously require some sort of wiring between devices. Those wishing to network devices at home using a wired network can either introduce new cables into their homes using technologies such as Ethernet or use their existing cabling or wiring as with technologies such as Powerline. Ethernet this technology is used extensively by large schools, companies and other institutions that network their computers. It currently offers the fastest data rates of any home networking solution and it is very reliable and robust. However Ethernet networks generally require a higher degree of Becta page 2 of 10

3 technical knowledge to install than the two other solutions covered below and new cabling is obviously more expensive than the alternative of using the existing wiring in the home. Powerline this technology uses the existing electricity cabling in the home to form the wiring for a network. Data is thus transported via the electricity cables to a computer device. The computer device could be installed with a Powerline Peripheral Component Interconnect (PCI) card and thus it could interface directly with the electricity cables, or the computer device could be a Powerline switch or hub. As most rooms in a typical house have one or more power outlets, a network can easily be set up with one or more devices in each room if necessary. The data transfer rates for the latest Powerline standard (PowerPlug 1.0) are now comparable with networks such as b, and Powerline equipment is becoming less expensive and more widely available. Phoneline the concept of a Phoneline network (often referred to as HomePNA) is similar to that of a Powerline network. The existing wiring inside the home (in this case twisted copper telephone cable) is used to form the wiring of the network. As many homes have more than one telephone socket to service a single telephone line, a network can be formed. Where only a single socket is available, extra telephone wiring would have to be installed. Phoneline technology allows voice calls and the transportation of data from one computer to the next to be made simultaneously. There is some concern about this type of technology when it is used with an Asymmetric Digital Subscriber Line (ADSL) as the internet access technology. The concern is about interference between the Phoneline signal and the ADSL signal. Phoneline equipment is still available in the UK, and it may still be a viable home networking option provided access to the internet is not via ADSL. Network interface cards For all of the technologies outlined above a network interface card (NIC) or a network adapter will be needed for each device so that the interface to the network can be established and maintained. In some cases this NIC or network adapter may be built in to the device already (such as with Bluetooth enabled devices) but in others a card or adapter for each networked device will need to be purchased. Table 1 typical costs for home networking technologies Typical costs Ethernet NIC 15 Ethernet category 5 cabling 2 per metre Powerline PCI card 120; switch 250 Phoneline 60 for a two-device starter kit products NIC 60 Access points PANs Bluetooth access points Bluetooth adapters 50 Infrared Direct infrared adapters 45 Wireless touch screen 1,000 Becta page 3 of 10

4 Accessing the internet via a home network While many people may want to network the devices in their home for activities such as file sharing, others may simply wish to share an internet connection between multiple devices. There are two main ways to achieve this. It is possible to use one of the home s computers to act as a proxy server for all other devices that want access to the internet. Many current computer systems have the functionality to allow a computer to act as a proxy server for all other devices via application software functionality. While this is a cost-effective solution, it does mean that the computer acting as a proxy server has to be stationary and switched on for other devices to be able to use the internet. A hardware router could be installed. This router would be connected to the internet access point and then all other devices would be connected to the router. In a typical home network, the router would have to have proxy server functionality as well so that it could identify the correct individual devices on the network to send the incoming data to. There are many such routers on the market today and both wired (for example, Linksys Etherfast Router) and wireless (Apple s Airport Extreme and Cisco s Aironet) versions are available. Many of the routers on the market are multi-functioned, for example, many wireless routers have ADSL modems built in and are also wireless access points. It is worth noting that most routers connect to the internet access point via an Ethernet connection and not via the universal serial bus (USB) port typically used by ADSL modems. If simultaneous access to the internet is needed, then a high-speed access technology such as ADSL would be worth considering. For example, with multiple devices simultaneously accessing the internet via a modem connected to the public switched telephone network (PSTN), the 56Kbps would, in theory, become shared between the devices. There may also be a need to clarify whether the contract with the internet service provider (ISP) allows multiple devices to access to the internet. For both solutions, the same considerations would have to be given to the NICs that would be needed, and whether connecting to the hardware router or proxy server would be via a wireless or wired connection. What content/applications can home networking deliver? There are two main considerations that need some advanced planning when referring to delivering content and applications across home networks. Firstly, whether it is possible to share the content or applications across multiple devices or whether the content and applications are limited to a single device (as in the case of Smart Displays). The second consideration is whether the data rates for a particular networking technology are suitable for the sort of content and applications that are to be shared. Table 2 maximum theoretical data rates for home networking technologies Related standard Maximum theoretical data rates Ethernet IEEE Mbps (10baseT) 100Mbps (100baseT) Powerline HomePlug (version 1.0) 14Mbps (NB earlier competing standards had significantly slower data rates) Becta page 4 of 10

5 Phoneline HomePNA version 1.1 1Mbps HomePNA version Mbps products IEEE b 11Mbps IEEE a 54Mbps PANs Bluetooth v Kbps Infrared IrDA - version 1.1 (Infrared Data Association) 9.6Kbps 4Mbps Wireless touch screen Smart Display (uses IEEE b) 11Mbps The advantages and disadvantages of different home networking technologies While some of the advantages and disadvantages between home networking technologies will already be apparent, some will only become apparent when thought is given to such issues as the use of the planned network, the number of devices in the network, and the available funds. These issues are discussed later in this paper. Below is a table that sets out some of the advantages and disadvantages of the technologies already discussed. Table 3 advantages and disadvantages of home networking technologies Ethernet Powerline Advantages Disadvantages Potential best usage Fast data rates Very reliable There is a great deal of technical support and information available Robust Uses existing electrical wiring Every room of a typical house has several electrical outlets Easy to install New cables need to be fitted More expensive to install than other networking technologies Requires a higher degree of technical knowledge to install Current number of suppliers are limited Not as fast as Ethernet Excellent for shared internet access, and where high speed file and peripheral sharing are needed and where mobility is not required Good for shared internet access, file sharing and peripheral sharing and where mobility is not required Becta page 5 of 10

6 Phoneline Inexpensive Quality of service is built into the network Reliable Operates at a constant 10Mbps, even when the phone is in use Easy to install family Many devices have NICs built in PANs Infrared Wireless touch screen Networks between devices can be formed dynamically Devices can be portable and still be connected to the network Many devices now shipped with short-range wireless as standard Easy to install Many devices shipped with infrared Useful for PANs Security better than some other wireless technologies Work from anywhere in the home via a portable screen Typically lighter than carrying a laptop Damage whilst moving around the home is limited to the screen and not to other hardware Extra phone line extensions may be needed if multiple devices are required on a network Need a phone jack close to each computer to avoid additional cabling Not as fast as Fast Ethernet (100Mbps) Possible interference issues with internet access technology Not as fast as Fast Ethernet May be interference issues with other wireless devices Signal may not be able to carry through several thick walls in a house Some products not backwards compatible Limited range Limited data rates Compatibility issues between different standards and occasionally between devices using the same standard Limited data rates in many products Limited range in many products Devices have to be located in same room and can be limited by line of sight Data rates vary significantly between infrared units At present only one touch screen can access the main PC at any one time If touch screen in use, the main PC cannot be used independently Currently similar price to b enabled entry level laptop Good for shared internet access, file sharing and peripheral sharing and where mobility is not required Good for laptops, desktops and handheld connected organisers inside and outside home where mobility is required Good for shared internet access Good for creating small personal networks between devices in an adhoc manner or networks where power usage needs to be kept to a minimum Direct infrared: good for ad-hoc networks where line of sight and fast data rates are not an issue Diffuse infrared: good for networks where a single room is used Good for gaining access to the main PC whilst on the move and where simultaneous access to multiple network devices is not required Becta page 6 of 10

7 Where is home networking used? It is not yet particularly common for computer networks to be installed in the home although the technologies that are used in home networking are the same or very similar to those used by small businesses in the commercial sector. According to Young People and ICT 2002 (a survey published by Becta on behalf of the DfES), 81per cent of households surveyed had access to a computer in the home (an increase from 78 per cent in 2001). Of the 68 per cent of households that owned computers, 32 per cent had two or more. In addition, access to portable devices such as laptops and palmtops steadily increased. The above figures show that access to a computer or even multiple computers is on the increase. Thus, it is possible to identify several scenarios where networking devices in the home may be useful. 1. It is presumed that the desire to access the internet from a single mobile device from various locations in the house will become increasingly common. Several of the solutions discussed above would enable this to happen. 2. With the use of the internet on the increase, and 44 per cent of those surveyed (Young People and ICT 2002) responding that a computer was located in a non-communal room of the house, it is presumed that access to the internet from multiple devices will increase and thus a way of simultaneously connecting multiple devices to the internet (as discussed above) will be needed. 3. It is also possible to buy hardware that allows simultaneous connection to the internet via advanced set-top boxes acting as home gateways for multiple devices such as televisions, computers and gaming consoles. These internet connections are likely to be realised by access technologies that allow fast data rates, such as broadband via twisted copper, cable or satellite. 4. Sharing and exchanging information from one device to the next or sharing of peripheral devices such as printers. 5. According to the previously mentioned survey, the majority of young people used a computer to play games, and a high percentage used a computer for listening to music. A home network of multimedia and gaming devices would allow interactive gaming between devices in the home and the sharing of music files. Issues about buying and installing home networking equipment Many issues need to be considered when buying equipment to provide a home network. Use of the network There are many different ways of using a network. It may be that a network is only needed occasionally to swap files from one device to another. Alternatively, the devices on the network may need to share the applications that are based on the main home computer. While a cheaper network solution with a slower data rate may be perfectly adequate for the first scenario, it is unlikely that it would be the best for the latter. Number of networked devices Giving consideration to the number of devices that need to be networked is crucial. If a home has many devices located in different rooms, then technologies such as Ethernet may well be inappropriate or costly as new cables will have to be laid and safely secured. Alternatively, if all the devices are in one room it may be practical and cost effective to use an Ethernet network. Becta page 7 of 10

8 Further, attention should be paid to the possibility of adding devices to the network later. This would be relatively easy with a Powerline network for example, but it might be a problem if a Phoneline network was chosen and the network needed to be extended to a room in the house that had no telephone point. Layout of the home All networking equipment has a limited range, although when using such technologies such as Ethernet in the home this is unlikely to be an issue technologies also have a considerable range (typically metres) but the data transfer rates lessen the further the networked device is placed away from an access point. For many networking technologies the effective range is limited and thus the home network may be limited by the distance that devices are positioned away from each other. Wireless technologies can suffer from interference from other home appliances or from the walls between devices being too thick for an effective signal to penetrate. If Phoneline technologies are used for a home network together with an ADSL internet connection, there is some evidence to show that there may be some interference issues between the Phoneline technology and the ADSL signal. Data rates The data transfer rates for the networking technologies described differ considerably. If a high number of devices in the home needed to share a network connection at the same time for activities such as streaming video to each device, then the data rate of a network may be an issue. Alternatively, if a number of devices in the home were being networked together to share a 512Kbps ADSL broadband connection, then the issue of data rates may be diminished as many of the networking technologies described above send data at a substantially higher data rate than 512Kbps. Available expertise Some of the networking technologies described above generally need a higher degree of technical expertise to install and maintain than other technologies. For example, an Ethernet network generally demands a higher degree of technical expertise to install and maintain than a Powerline network. Costs Implementation costs for the networks described vary considerably. Attention should be paid to what equipment is already available in the home. Questions worth considering include: How much new wiring will be needed if a wired network is chosen? Are there enough convenient power points for a Powerline network? And to plug in devices to the mains supply? Are there enough telephone points working from the same telephone number if a Phoneline network is being considered? Does any of the equipment already have a NIC such as a WLAN card, or will cards need to be purchased separately? Is the equipment widely available in the UK or will some of it need to be bought abroad? If equipment is bought from abroad is it compatible with UK equipment. Is the standard associated with the network equipment under consideration the latest version? If not it could be that the data rates, for example, are inferior to the latest version. If Phoneline or Powerline technologies are chosen, is the respective wiring in the home in good condition? Becta page 8 of 10

9 Line of sight Before line-of-sight technologies such as direct infrared are chosen for a home network, careful consideration should be given to whether a clear line of sight will always be available. Interoperability Many of the technologies mentioned in this document are interoperable, although it is worth considering if further technical expertise or equipment is needed to achieve this. In some cases, standards within technologies are not interoperable. For example, b network equipment is currently not interoperable with a wireless network equipment. Some suppliers are starting to design and supply home network gateways. These will allow computers, televisions, PDAs and other devices to gain access to the internet via one access point attached to the gateway. Whilst this will not solve all networking interoperability issues, it does mean that all devices attached to the gateway should be enabled to gain internet access simultaneously. Standards relating to home networking Ethernet [ Phoneline [ b/a/g [ Powerline [ Infrared [ Bluetooth [ Home RF (standard no longer available) Further sources of information Becta Wireless Local Area Networks technical paper [ [ Young People and ICT 2002 [ Reviews Phoneline [ Becta page 9 of 10

10 Powerline [ Smart displays [ Wireless networking [ Technical Ethernet [ Phoneline [ [ Powerline [ Smart displays [ [ Infrared [ Bluetooth (RTF document) [ HomeRF [ [ Network implementation [ sing/productdoc/en/hnw_requirements.asp] Becta page 10 of 10