CS601 Data Communication GDB Solution Spring 2013

Discussion Topic

Suppose a national security agency wants to connect local networks of its two offices using some transmission media. As they are required to transmit very sensitive information over the transmission media so security and reliability of the information are the critical issues in this scenario. They have different options i.e. wireless and wired (coaxial, fiber optics and etc.) media to connect these offices. You are required to suggest a suitable transmission media to directly connect these offices and discuss how will your suggested media fulfill their requirements?


Transmission media selection should be based on quality needed over some estimated distance. In some cases, security may also be an issue.

Where SANs are concerned, I believe short wavelength optical fiber cabling is the best choice for most environments. Copper does not really support meaningful distances and long wavelength cabling is overkill for local cable runs.

Also, higher speed networks will work with fiber but might not support copper. Fiber optic cables are more secure and are much more difficult to snoop.

It would be convenient to construct a network of only one medium. But that is impractical for anything but an extremely small network. In general, networks use combinations of media types. There are three main categories of media types:

  • Copper cable—Types of cable include unshielded twisted-pair (UTP), shielded twisted-pair (STP), and coaxial cable. Copper-based cables are inexpensive and easy to work with compared to fiber-optic cables, but as you’ll learn when we get into the specifics, a major disadvantage of cable is that it offers a rather limited spectrum that cannot handle the advanced applications of the future, such as teleimmersion and virtual reality.
  • Wireless—Wireless media include radio frequencies, microwave, satellite, and infrared. Deployment of wireless media is faster and less costly than deployment of cable, particularly where there is little or no existing infrastructure (e.g., Africa, Asia-Pacific, Latin America, eastern and central Europe). Wireless is also useful where environmental circumstances make it impossible or cost-prohibitive to use cable (e.g., in the Amazon, in the Empty Quarter in Saudi Arabia, on oil rigs).
  • There are a few disadvantages associated with wireless, however. Historically, wireless solutions support much lower data rates than do wired solutions, although with new developments in wireless broadband, that is becoming less of an issue (see Part IV, “Wireless Communications”). Wireless is also greatly affected by external impairments, such as the impact of adverse weather, so reliability can be difficult to guarantee. However, new developments in laser-based communications—such as virtual fiber—can improve this situation. (Virtual fiber is discussed in Chapter 15, “WMANs, WLANs, and WPANs.”) Of course, one of the biggest concerns with wireless is security: Data must be secured in order to ensure privacy.
  • Fiber optics—Fiber offers enormous bandwidth, immunity to many types of interference and noise, and improved security. Therefore, fiber provides very clear communications and a relatively noise-free environment. The downside of fiber is that it is costly to purchase and deploy because it requires specialized equipment and techniques.

Twisted pair is the most common, because it is cheapest. Shielded twisted pair is similar, but has a foil around the outside of the pairs to prevent electrical noise, which is good if the cable has to pass over floresent lights. Coaxial is getting outdated, because usually requires a token ring topology. Twisted pair uses a Star topology which means all lines star off from a switch. Optical fiber cable is used for longer distance runs (100 Meters or more), because it does not have the loss of copper wire.
So for a ‘large company’ it depends on the building size. Usually they have fiber between 2 (or more) office buildings, and twisted pair inside the building from the switch to each workstation. If a cable run needs to be over 100 Meters in 1 building, then either thier needs to be another switch in betweeen or a fiber