NET 102 - Networking Essentials II
Chapter 9, Network Customization; Chapter 10, Wireless
This lesson discusses other features of networks, and
features of wireless networks. Objectives important to this lesson:
- SAN and NAS storage
- Voice over IP (VoIP)
- Virtual Networking
- Cloud computing
- Wireless concepts and standards
- Wireless configuration
- Designing a wireless network
- Implementing a wireless network
- Wireless security
- Wireless troubleshooting
Chapter 9, Network Customization
first topic in chapter 9 is storage consolidation. The material
discusses two related systems: Network
Attached Storage (NAS)
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.
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.
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.
are some reasons for running virtual
- 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
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.
devices require management
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
- 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
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.