Building your PC:
Network Card 1 — Ethernet and Wireless Cards

Introduction

Network cards are computer peripherals that allow one machine to communicate directly with another. This could be through the medium of telephone wires, twisted-pair ethernet cables or radio-frequency signals. Communications can be either between local machines (a Local Area Network or LAN) or remotely with servers and distant computers (a Wide Area Network or WAN) or any combination of these. A home network is an example of a LAN and communication with your ISP is an example of a WAN.

Ethernet Cards:

Ethernet is a computer networking technology for local area networks (LANs); the name being derived from the nineteenth-century concept of a physical æther.

History:

Ethernet is one amongst a range of technologies developed at the Xerox PARC research site during the early 1970s. This original Ethernet ran at 3 Mbps and had an 8-bit destination and source address fields. In 1980 the 10Mbps Ethernet standard was published, with 48-bit destination and source addresses and a global 16-bit type field.

Ethernet technology is based on the concept of elements on a network sending messages in what was essentially an analogue of a radio system (except that it's held captive inside a common wire). And this is where the reference to ether comes from. Within the system each computer (or peer) has an unique 48-bit key known as the MAC address to ensure that all systems in an Ethernet network have distinct addresses. By default network cards come programmed with a globally unique address but this can generally be changed and there are a number of reasons for doing so.

These days, with the cost of ethernet components falling almost all modern motherboards have ethernet built-in. Originally computers were directly connected to one another with cable (originally 10-base T and now cat-5 twisted pair) and cables are still available for connecting computers together via ethernet (these are generally referred to as cross-over cables) and can be very useful for patching software and updating systems.

Ethernet Hubs

As Ethernet grew in popularity and ethernet networks grew large data losses because of long cable runs started to become a serious problem. As a result the Ethernet Hub was developed both to make the network more reliable and to make the inter-connection of cables easier. This also allowed cheaper unshielded twisted-pair cables to be employed over the standard BNC coaxial cables that had been used previously. The twisted-pair cables were (and still are) terminated with RJ45 connectors which also made inter-connection of these cables (and cable replacement) much easier. The use of twisted-pair cabling also removed the need for cable termination y making every segment point-to-point, so termination can be built into the hardware rather than requiring a special external resistor (as was needed by BNC cabling). Using hubs to inter-connect cables and boost cable signals also alleviated the problem of broken cables in that the prot could be closed down on the router without bringing down the entire network, which make ethernet networking much more robust and reliable.

Most modern Ethernet installations use Ethernet switches instead of hubs. Although the wiring is identical to hubbed Ethernet, switched Ethernet has several advantages over shared medium Ethernet including greater bandwidth and better isolation from misbehaving devices. Switched networks typically have a star topology (with each computer or device in the network connecting to the router). Initially, Ethernet switches work like Ethernet hubs, with all traffic being echoed to all ports. However, as the switch "learns" the end-points associated with each port, it ceases to send non-broadcast traffic to ports other than the intended destination. In this way, Ethernet switching can allow the full wire speed of Ethernet to be used by any given pair of ports on a single switch.

In the early days of Ethernet all the devices on the network had to operate at the same ethernet data transmission speed. However, with the advent of faster ethernet speeds (from 10Mbps to 100Mbps and now to 1Gbps) dual or multi-speed hubs were generated that effectively split the network into two sections, each acting like a hubbed network at its respective speed then acted as a two port switch between those two sections. This meant they allowed mixing of speeds without the cost of a Fast Ethernet switch.

With many broadband modems now acting as ethernet hubs/routers setting up a small home network has become easier and more cost effective than ever. All modern operating systems support the ethernet standard for communications and almost all motherboards have ethernet built-in. Setting up an ethernet network is as easy as plugging a cat5 cable into your pc and/or laptop and attaching these to your ethernet enabled ADSL modem. Using a wizard the presence of an ethernet network is established and you're up and running in minutes. Obviously this allows several computers within the home to share the same broadband connection to the internet simultaneously.

Wireless Cards

A wireless network is one that uses radio as the means of communication between machines on the network. With many notebook (laptop) computers incorporating wireless cards as standard wireless networks are becoming more commonplace. These networks also do away with the need for wiring as in a standard Ethernet network. Wireless cards (as left) are also available for desktop PCs and can be incorporated into your design if you are building your own PC. In essence, building a wireless network is a straightforward process. A number of wireless access points are connected to an ethernet backbone and the computers link to the access points and from there to the remainder of your network and to the internet.

The wireless standard currently lies at 802.11g (at 54 Mbps at 2.4GHz) though a 112Mbps 'n' standard should be available soon. These wireless standards currently work up to a range of about 20m (though interference can be a problem as can large obstacles. The latest wireless access points try to overcome some of these problems by using directional antennae that broadcast the signal in multiple directions and cover more of the available area within the house. There are also ethernet routers with built-in wireless which can be used as the basis of an entire home network.

Drawbacks of Wireless Networks

One of the big drawbacks of wireless networks is the general broadcasting of the signal. Anyone within a 20m range of an unencrypted wireless network signal can sniff on all the traffic, gain unauthorized access to internal network resources as well as to the Internet, possibly sending spam or doing illegal actions using the owner's IP address. Though the original wireless lan protocol offered a Wired Equivalent Privacy (WEP) security module. However, this has proved to be very insecure and anyone with the right software can crack WEP in minutes. Most savvy users employ solutions such as SSL, SSH, and various types of software encryption and these have become the preferred methods of securing wireless information transmission. It is also possible to use firewalls to block out all traffic except for those coming from trusted machines within the house. As a result a virtual private network (VPN) is created in the home. This is why almost all broadband modems and wireless access points now include firewalls. You should always use these firewalls and the various security measures offered by your operating system to secure your wireless network.

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