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Tuesday, 29 May 2012

Protocol and Cabling

A protocol is a set of rules that governs the communications between computers on a network. In order for two computers to talk to each other, they must be speaking the same language. Many different types of network protocols and standards are required to ensure that your computer (no matter which operating system, network card, or application you are using) can communicate with another computer located on the next desk or half-way around the world. The OSI (Open Systems Interconnection) Reference Model defines seven layers of networking protocols. The complexity of these layers is beyond the scope of this tutorial; however, they can be simplified into four layers to help identify some of the protocols with which you should be familiar.

OSI Layer
Common Protocols
HTTP | FTP | SMTP | DNS | Telnet
Data Link
           OSI model related to common network protocols

The original Ethernet standard was developed in 1983 and had a maximum speed of 10 Mbps (phenomenal at the time) over coaxial cable. The Ethernet protocol allows for bus, star, or tree topologies, depending on the type of cables used and other factors. This heavy coaxial cabling was expensive to purchase, install, and maintain, and very difficult to retrofit into existing facilities.
The current standards are now built around the use of twisted pair wire. Common twisted pair standards are 10BaseT, 100BaseT, and 1000BaseT. The number (10, 100, 1000) ands for the speed of transmission (10/100/1000 megabits per second); the "Base" stands for "baseband" meaning it has full control of the wire on a single frequency; and the "T" stands for "twisted pair" cable. Fiber cable can also be used at this level in 10BaseFL.

Fast Ethernet
The Fast Ethernet protocol supports transmission up to 100 Mbps. Fast Ethernet requires the use of different, more expensive network concentrators/hubs and network interface cards. In addition, category 5 twisted pair or fiber optic cable is necessary. Fast Ethernet standards include:
  • 100BaseT - 100 Mbps over 2-pair category 5 or better UTP cable.
  • 100BaseFX - 100 Mbps over fiber cable.
  • 100BaseSX -100 Mbps over multimode fiber cable.
  • 100BaseBX - 100 Mbps over single mode fiber cable.
Ethernet Protocol Summary

Twisted Pair, Coaxial, Fiber
10 Mbps
Fast Ethernet
Twisted Pair, Fiber
100 Mbps
Gigabit Ethernet
Twisted Pair, Fiber
1000 Mbps

What is Network Cabling?
Cable is the medium through which information usually moves from one network device to another. There are several types of cable which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Understanding the characteristics of different types of cable and how they relate to other aspects of a network is necessary for the development of a successful network.
  • Unshielded Twisted Pair (UTP) Cable
  • Shielded Twisted Pair (STP) Cable
  • Coaxial Cable
  • Fiber Optic Cable
  • Cable Installation Guides
  • Wireless LANs
  • Unshielded Twisted Pair (UTP) Cable
Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks.

The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated six categories of wire (additional categories are emerging).

When running cable, it is best to follow a few simple rules:
  • Always use more cable than you need. Leave plenty of slack.
  • Test every part of a network as you install it. Even if it is brand new, it may have problems that will be difficult to isolate later.
  • Stay at least 3 feet away from fluorescent light boxes and other sources of electrical interference.
  • If it is necessary to run cable across the floor, cover the cable with cable protectors.
  • Label both ends of each cable.
  • Use cable ties (not tape) to keep cables in the same location together.
Advantages of wireless networks:
  • Mobility - With a laptop computer or mobile device, access can be available throughout a school, at the mall, on an airplane, etc. More and more businesses are also offering free WiFi access ("Hot spots").
  • Fast setup - If your computer has a wireless adapter, locating a wireless network can be as simple as clicking "Connect to a Network" -- in some cases, you will connect automatically to networks within range.
  • Cost - Setting up a wireless network can be much more cost effective than buying and installing cables.
  • Expandability - Adding new computers to a wireless network is as easy as turning the computer on (as long as you do not exceed the maximum number of devices).
Disadvantages of wireless networks:
  • Security - Be careful. Be vigilant. Protect your sensitive data with backups, isolated private networks, strong encryption and passwords, and monitor network access traffic to and from your wireless network.
  • Interference - Because wireless networks use radio signals and similar techniques for transmission, they are susceptible to interference from lights and electronic devices.
  • Inconsistent connections - How many times have you hears "Wait a minute, I just lost my connection?" Because of the interference caused by electrical devices and/or items blocking the path of transmission, wireless connections are not nearly as stable as those through a dedicated cable.
  • Speed - The transmission speed of wireless networks is improving; however, faster options (such as gigabit Ethernet) are available via cables. If you are only using wireless for internet access, the actual internet connection for your home or school is generally slower than the wireless network devices, so that connection is the bottleneck. If you are also moving large amounts of data around a private network, a cabled connection will enable that work to proceed much faster.