NET 102 - Networking Essentials II

Chapter 9, Network Customization; Chapter 10, Wireless Networking


This lesson discusses other features of networks, and features of wireless networks. Objectives important to this lesson:

  1. SAN and NAS storage
  2. Voice over IP (VoIP)
  3. Virtual Networking
  4. Cloud computing
  5. SCADA
  6. Wireless concepts and standards
  7. Wireless configuration
  8. Antennas
  9. Designing a wireless network
  10. Implementing a wireless network
  11. Wireless security
  12. Wireless troubleshooting
Chapter 9, Network Customization

The first topic in chapter 9 is storage consolidation. The material discusses two related systems: Network Attached Storage (NAS) and Storage Area Network (SAN). One version of a SAN uses servers that are normally connected to a LAN (Local Area Network). Those servers are also connected to a SAN switch, essentially putting them on another network that has access to a dedicated file storage device, in this case the SAN server. These servers will use different network protocols when storing on the SAN than they would when storing on devices on the general LAN. The SAN server is actually not a true server, in that it does not have the capacity to function as a general purpose computer. It is primarily an interface to the storage devices.

A NAS device is simply that, a device "hung" on an existing network that provides additional storage beyond what it already on workstations and servers on the LAN. A NAS device is a member of your LAN, and it will use common network file protocols. The NAS device is described as having all the capabilities of a general purpose computer, in addition to its role as a storage device.

One distinction between the two systems is that the NAS system can provide file service like any other network resource, but the SAN system needs to be accessed at a lower level, which is described as block-oriented or sector-oriented access. A security related distinction is that NAS devices can be exploited and protected in the same way as hard drives on any other computer on your LAN. Using NAS devices on a network without high bandwidth connections to the NAS device can produce a service bottleneck.

verything else. An alternative is to write rules for everything you want to deny, then allow everything else. It is not uncommon for a rule database to contain a mixture of rules that allow and deny packets. This is probably the most common approach. The section on firewall rules is pretty extensive, and a bit beyond what we want for this course, so we will continue to the next item.

VoIP - Voice over IP networks use IP (Internet Protocol) to pass voice signals over data networks. The voice signals are chopped into pieces, sealed into packets, and the packets are sent across data networks to devices that receive the packets and turn them back into voice signals.

This chapter is also about virtualization, which means running a program on a computer that acts like a separate computer. On a large server, you might do this several times, allowing each virtual machine to act like a separate device that will not affect the others if anything goes wrong.

These are some reasons for running virtual machines.

  • reduced power cost - running several virtual machines on one device takes no more power than running the device without the virtual machines on it
  • reduced hardware cost - this is debatable, but the concept is that we buy one good computer that will server as several slightly lesser computers
  • system recovery - the best thing about a virtual device is that it can be reloaded quickly if it fails or is compromised; if it is corrupted or taken over, just kill the virtual device, start it again, and you are back in business; unlike a virus ridden computer, the virtual computer is saved as an image file that should have no error, problem, or infection.
  • quick setup - once you have an image file for a virtual device, you can copy the file to as many other real machines as you like and use it there, provided there is no problem with licensing

You should know about Microsoft's Virtual PC, which is free, and VMware, which is not. VirtualBox, from Oracle, is also a commonly used virtualization solution.

Virtual devices require management software to run them. You should know about two variations.

  • The management software of a server may be a hypervisor from VMware called ESX or one from Microsoft called Hyper-V. These run virtual servers.
  • The management software on a workstation is intended to run a virtual machine, and it may be VMware, Virtual PC, KVM, or VirtualBox.
  • The virtual software for a workstation can run a virtual server, but this is typically something we do in a class, not in the real world. In the real world, we would want a high end server to act as several servers.

The chapter mentions cloud computing, and should admit that the phrase has several definitions. This commercial spot for Microsoft is cute, but what has it got to do with "the cloud"? Couldn't she have just used Photoshop, like everyone else? Whatever she used, the cloud is irrelevant. We may as well proclaim that McDonalds has cloud based hamburgers. They offer Wi-Fi, don't they? How about the people trapped at the airport who access TV programs stored on their home computer? They remotely accessed their PC. Is the Internet "the cloud"? Sounds like smoke and mirrors so far. The only meaning that seems to be relevant is buying or leasing a service that you access across an Internet connection, which avoids your having to own storage, or programs, or some other IT component. It is a nice idea as long as you have connectivity, wide bandwidth, and zero system problems.

The last concepts to cover in this chapter are Supervisory Control and Data Acquisition (SCADA) and Process Control Systems (PCS) . We are told that a Process Control System is like the feedback loop between a thermostat and a furnace. In this example, it is meant to control the process of maintaining the temperature in a room. It measures the output of the system, and runs it as needed to reach and stay in the range of desired output. As you can see, this kind of control system takes a setting from an operator, but runs automatically once it is set,

A SCADA system is a large PCS. Examples are the systems that monitor and control the flow of power and water to customers. Systems that adjust traffic lights to accommodate changing traffic flow during a day are also examples. You may see that this kind of system is used to make social infrastructure work, making it a target for politically motivated hackers. For another explanation, take a trip to this article from TechNewsWorld. It should be clear that the access controls for these systems must be very secure, and that they must be limited to only the people meant to access them.

Chapter 10, Wireless Networking

This chapter discusses concepts that I spent several weeks covering the last time I taught NET 211. It seems reasonable to caution you that this material is evolving and that it is difficult to summarize on one page. Please browse through my notes for the NET 211 course, then come back to this class when you have caught your breath.

Week 5 Assignment: Labs for Chapters 9 and 10 (and all the chapters after that)

  1. Complete as many labs as you can, as soon as you can. For this week, concentrate on doing the labs in Chapters 9 and 10 of the TestOut lessons. Repeat the labs until you score at least 80% on them.
  2. When you have done what you can for this week, capture a screen that shows your current progress, and submit it to me as this week's report of your progress.