A/AS Level Computer Science for WJEC
Port number
MAC address
1
00:00:AE:3B:09:FF
2
00:00:4B:BC:00:E1
3
00:1A:D7:B6:CA:F2
Table 10.6: Table showing the MAC address of devices connected on various ports of a switch.
Router
e
Routers perform a very similar job to switches: they route packets to the correct port. Like a switch, they have an internal representation of which devices can be found on each port through the routing table. However, there are differences between the devices and they are used for very different purposes. Routers are used to connect different segments of a LAN together and allow access to the outside networks such as the internet.
Sa m
pl
Routers perform routing on IP addresses rather than MAC addresses. Sections of a network, known as sub-domains, can be assigned similar IP address ranges, which provide the router with more information to help it direct the packet. When connecting different parts of a LAN or WAN together, a router ultimately has to deal with more devices than a switch does. This is why routers tend to have a more powerful processor and are more expensive. Routers are necessary when connecting to any WAN, which is why the device you may use at home is a router.
Wireless interface card
A wireless interface card (WIC) connects to a wireless access point (WAP). A WAP is a device that allows wireless devices to connect to a wired network using Wi-Fi or similar standard. A WAP has a maximum number of devices that it can support and a physical broadcast range where connections are possible. It is possible to detect a wireless network by sitting outside a company’s premises, which is why security on a wireless network is a top priority. Wireless networks use encryption and require a special key in order to stop unauthorised people accessing the network. Home routers normally offer wireless connection and tend to have security set up by default. This is intended to protect data sent over the router, but the level of protection is only as strong as the encryption methods used. Some wireless security protocols, such as WEP, can be cracked very easily by a determined hacker. WPA2 is one of the more secure wireless protocols available at present. Wireless networks minimise the amount of cable needed when setting up the network, but are more error prone. Distance from the router, interference from other devices and even bad weather can impact the speed and quality of connection. When a wireless signal is low, packets may contain errors and the data will need to be resent. There are two main wireless technologies in use at the time of writing, 802.11 and Bluetooth. Both have their uses, but only 802.11 is used for networking. Bluetooth is used for connecting external devices, such as wireless handsets, to other devices.
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