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NET 211 - Wireless Networking
Chapter 1, The World of Wireless; Chapter 2, Wireless Local
Area
Networks
Objectives:
This lesson presents background on wireless networks and
begins discussion of Wireless LAN standards. Objectives
important to this lesson:
- Wireless Applications
- Wireless: Advantages and Disadvantages
- Types of Wireless Networks (actually, sizes)
- Wireless technologies and LAN standards
- Standards Organizations and Regulatory Agencies
- Understanding Standards
- Common Wireless Standards
- Client Hardware and Software
- WLAN Infrastructure
Concepts:
Chapter 1
The chapter begins with a description of a disruptive technology as "an
innovation that fills a new role that an existing device or technology
could not". (Ciampa, page 2) The author gives us some examples of
technologies that have supplanted other technologies, so his
proposition seems to be that innovation replaces older technology when
the innovation does something the older one did not, or does something
better than the older one. The author is correct, but too sweeping in
some of his assertions.
- steamships - this technology replaced
sailing ships as a better solution for commerce, but sails still exist
for pleasure craft
- telephones - this technology replaced telegraphy,
which still exists, but telegrams are now sent over a different
infrastructure, mostly by independent vendors
- automobiles - this technology replaced
commercial use of horse drawn vehicles in most places; Mackinac Island
and Amish communities are examples of isolated exceptions to this; cars
did not replace horses in general
- word processors - this technology replaced
typewriters as the default choice for business,
where the supporting technology for word processors exists
Applications
As I have noted about word processing, if the supporting
technological infrastructure for a given invention is not common, that
invention will not become a common technology. Most of the readers of
our text live in the midst of technology, but the whole world does not,
so let's accept some of Mr. Ciampa's assertions with a little
reluctance. They will not all be true for everyone.
The author spends about ten pages discussing uses to which
wireless technology has been applied in several different occupations
and industries.
- education - generic recommendations are made about easy
connection to networks and resources for teachers and students
- business - the ability to access the network from any
location in your building is noted, whether the user is moving to a new
office/cubicle, having lunch, or going to a meeting
- construction - mobile record keeping and updating, location
management with GPS (Global Positioning System) equipment, and project
management are mentioned
- warehouse management - management of inventory with RFID
(Radio Frequency Identification) tags and management software are
discussed
- manufacturing - RFID management of raw and finished
materials is mentioned
- travel - wireless communication for travelers and for
people running travel services is mentioned
- public safety - wireless access to data networks for police
and fire personnel is mentioned, as well as communication between all
levels in their organizations
- health care - immediate wireless update for patient
information and doctors' orders is mentioned
The
text continues to discuss advantages and disadvantages inherent in
wireless systems:
Advantages
- mobility - users can use a network without having to be
close to an available wired connection point
- access - connection to networks can be offered where it is
not practical to run wires; the text mentions that some cities offer
municipal networks, systems of hot spot connections to a network
service run by the city
- connectivity - connection to ISPs (Internet Service
Providers) may not be possible for some remote users unless they use a
wireless solution such as data services from a cell phone company;
wired or fiber connections between locations for companies in highly
populated areas may be much more expensive than wireless solutions due
to the cost of digging and laying cable in densely populated urban areas
- deployment - network cable is a common construction
standard now, but older buildings never had it, making wireless
solutions the easiest to deploy; the author is ignoring the fact that someone
has to have a connection to a wired network that the Wireless Access
Points (WAPs) can use as their connection to the rest of the world
(This is really the same problem as connectivity. It is simply
expressed from the point of view of the Local Area Network manager.)
Disadvantages
- security issues - the author presents several bullets that
need expansion: wireless transmissions can be intercepted; wireless
networks can be easier to join and attack; employees have been known to
add their own WAPs to networks, which they typically do not protect
against intrusion; older wireless security protocols are well known and
no longer secure
- radio signal interference - often called radio frequency
interference (RFI), this is when your wireless signals are disrupted by
any nearby device that transmits radio signals on a similar frequency
to the one you are using
- range of coverage - this one proves that the author needs a
proofreader: ten feet is about 3 meters, not 33 meters, and that is a
common limitation on Bluetooth
signals; other technologies have longer ranges, but all are shorter
than a standard network cable can be run; some Bluetooth systems can
work at a distance of 10 meters (about 33 feet)
- slow speed - the author means narrow bandwidth;
the number of bits we can push through a network in a given time
interval will be greater in a wired network than in a wireless network,
if we are given a choice of which to use
Types of wireless networks are discussed next, but the author
is merely classifying them according to the relative size
of the area they serve, not by their technologies. As the author
mentions at the end of this section, the designations below can
overlap, and they are only rough designations, not true measures.
- Wireless Personal Area Network (WPAN) - very short range
methods are used for one person to connect to their own devices
- Wireless Local Area Network (WLAN) - the author hints at a
reality we should accept, that a wireless LAN is often a supplement to
a wired LAN: this is true of the rest of these designations as well;
the range and throughput measures mentioned in the text vary with the
wireless protocols being used and with each location, due to signal
interference and blockage; typical coverage is within one building
- Wireless Metropolitan Area Network (WMAN) - meant to cover
several blocks or a small city, this is actually a series of WLANs that
are linked together with longer range technologies or standard ones
- Wireless Wide Area Network (WWAN) - the example in the text
is of a user connecting to the Internet by attaching a cellular
wireless data connection device, which the text calls a 4G (Fourth
Generation) cellular device and a Long Term Evolution (LTE). This type
of connection is limited in use to areas serviced by cellular data
providers. They typically only provide service in larger metropolitan
areas.
Wireless Standards
The text lists five organizations whose job is to either
create, define, and standardize methods for making networks and
wireless products work, or to regulate how people comply with legal
regulations about such standards.
- International Telecommunication Union Radio Communication
Sector (ITU-R)
- a body whose regulations are meant to be followed by manufacturers in
all countries; it is mainly concerned with managing the use of any part
of the electromagnetic spectrum
- Federal Communications Commission (FCC)
- an agency of the United States federal government that regulates the
transmission of electronic signals, wirelessly or on cable media;
primarily concerned with the spectrum portions used by television,
radio, satellite, and cable signal providers
- International Organization for Standardization (ISO)
- a multinational trade association composed of delegates from
standards organizations from various countries; it is concerned with
many kinds of activities, including wireless activities
- Institute of Electrical and Electronic Engineers (IEEE)
- the organization responsible for most of our networking standards
including those for wireless operations; the text mentions several IEEE
standards: IEEE 802.3 (commonly called the Ethernet standard), IEEE
802.5 (Token Ring standard), 802.11a, 802.11b, 802.11g, 802.11n,
802.11ac (multiple standards for wireless networking), and IEEE
802.15.1 (Bluetooth).
The graphic on page 24 depicts the progression of a proposed standard
from an IEEE Study Group, to a Task Group, to a Work Group, to a
proposal to amend the existing standards, to a published standard.
- WI-FI
Alliance - another trade association that checks devices for
compliance with various standards
Chapter 2
Chapter 2 continues the discussion of standards by making it
clear that an industry that depends on equipment and software that must
operate cooperatively must have standards for such cooperation to
happen.
- Standards allow interoperability
between software and hardware from different vendors
- Standards create competition
between vendors when they know you are free to change to a product from
a competitor. This can lead to lower
costs for products and services.
- Standards can protect
you from buying proprietary technology that is no longer supported by a
vendor
The text lists three kinds of standards that you may encounter:
- de facto standards
are really just common practices, or commonly used technology
- de jure standards
are established by an organization empowered to create and enforce some
kind of standard
- consortium created
standards are established by common agreement among
practitioners who participate in formal discussions and adoption of
standards
The text moves on to discuss Wireless LAN standards. It
presents a list of various IEEE standards and the years they were
adopted. The four shown in bold below are the ones that have
dominated the field.
- IEEE 802.11, 1999
- IEEE 802.11a, 1999
- IEEE 802.11b, 1999
- IEEE 802.11d, 2001
- IEEE 802.11g, 2003
- IEEE 802.11h, 2003
- IEEE 802.11i, 2004
- IEEE 802.11j, 2004
- IEEE 802.11e, 2005
There have been other standards since these, notably IEEE 802.11n
(2009) and IEEE 802.11ac.
The text discusses some of them in more detail.
- 802.11 - Described
how a wireless LAN might be implemented using either radio waves or
some form of light that humans cannot perceive. Only provided
bandwidths of 1 or 2 Mbps.
- 802.11b - Added
technology to increase bandwidth to 5.5 or 11 Mbps, and to allow
devices to be up to 350 feet apart. When stations are located
increasingly farther apart, the bandwidth between those stations is
dropped down to lower levels.
- 802.11a - This
standard supports data rates of 54, 48, 36, 24, 18,12, 9, and 6 Mbps.
Sounds great, but its effective range was much less. The text states
that devices could be no more than 100 feet apart.
- 802.11g - This
standard included the best features of the 802.11a and 802.11b
standards. It offered the bandwidth selections of the 802.11a standard,
and the range of the 802.11b standard.
- 802.11n - This
standard provided the potential of using two
frequencies at once to increase throughput up to 600 Mbps. Range was
supposed to increase, but the IEEE only reports the same effective
range as 802.11g.
|
frequency
|
channels, channel
bandwidth
|
data throughput |
range |
802.11a
|
5 GHz band
|
52, 23 not overlapping, 20 MHz each
|
up to 54 Mbps |
25-75 feet
|
802.11b
|
2.4 GHz band
|
14, 3 not overlapping,
22 MHz each
|
up to 11 Mbps
|
100-150 feet
|
802.11g
|
2.4 GHz band |
14, 3 not overlapping,
22 MHz each |
54 Mbps |
100-150 feet
|
802.11n
|
2.4 or 5 GHz bands, or
both with multiple antennas |
14, 3 not overlapping,
20 or 40 MHz each
|
65 to 600 Mbps |
100-150 feet
|
802.11ac
|
5 GHz band |
5, up to 80 MHz wide
|
78 Mbps to 433
Mbps/data stream
|
TBD
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The text changes topics to discuss hardware and software used
in wireless LANs. Its first topic is wireless connection devices.
- Wireless Network Interface
Cards (Wireless NICs) - The text explains that a typical
wireless NIC works like a regular NIC, but it also includes a radio and
antenna (which may be hidden from the user) that typically communicate
with a Wireless Access Point which is connected to a standard LAN. A
wireless NIC may plug into a standard bus slot in a motherboard, it may
incorporated in the motherboard itself, or it may plug into a USB port
or a PC Card socket.
- Wireless Client Software
- Software must be used to interface bettween the standard network
signals that the computer would send (on a wired Ethernet, for example)
and the drivers for the wireless NIC. It may be part of the operating
system, such as WLAN Autoconfig
found in Windows Vista and Windows 7.
The text continues with a discussion of commonly used wireless
infrastructure devices, which are used at the periphery and inside
networks.
- Access Points (APs) - also called Wireless Access Points (WAPs); these devices are the
interfaces between wireless devices and a network; they connect to a
wired network like any other device, but they act like switches through
which wireless devices gain access to the wired LAN; typically, they
have three components:
- one or more antennas and one or more radio transceivers,
depending on the standard being used
- software to connect devices attached to the network of
the WAP to each other; devices that join the WAP's network are assigned
IP addresses from the WAP
- a network port to connect the WAP to a wired network,
bridging the two networks
- Autonomous Access Points
- these are access points that also perform encryption and authentication; these devices
maintain their own autonomous network
that connects to the wired network, which means that these devices are
more like routers than like switches, and that they will assign station
IDs to the connecting wireless devices
- Lightweight Access Points
- these APs are like a halfway
step between Access Points (which are actually lighter) and Autonomous Access
Points; these devices coordinate the connection of wireless devices to
the network; their actions are not autonomous, they are managed through
a wireless LAN controller
which does the actual coordination
- Mesh Access Points (MAPs) - This concept addresses a
problem the previous examples share. If every version of an access
point (lower case, generic term) has to be connected to a LAN, this
becomes a problem if you don't have LAN jacks everywhere you want an
AP, such as at a county fairground. A Mesh Access Point is part of a
wireless mesh network (WMN): each MAP connects to other MAPs that are
in range, and only one of them has to be connected to a wire LAN for
all of them to have access to it. The text refers to the connections
from one MAP to another as a hop,
which is the same term used to describe a connection from one router to
another. The MAPs are essentially cell towers in a small cell network.
The text also mentions another kind of WMN that does not use MAPs. It
is talking about a collection of wireless clients that pass signals
from one to another more like a peer to peer network. This is called an
ad hoc wireless mesh network.
- WLAN Bridges - As the text explains, a bridge is a device
that connects two network segments, which can improve network
performance by isolating traffic to one side of the bridge or the
other. A wireless bridge makes a wireless connection between two
network segments. The text describes two types. A wireless workgroup bridge connects
two network segments that are a short distance apart. A remote wireless bridge is more
powerful and can be used to connect network segments that are separated
by greater distances.
- Gateways - devices
that serve as entry or exit points for a network
- Enterprise Encryption
Gateways (EEGs) - sits
between a wired network and a wireless network; its purpose is to do
the encryption and authentication services that a regular AP cannot do
- Residential WLAN Gateways
- this is the device that Comcast or Time Warner or another cable
provider placed in your house if you use one of them as your ISP; this
device provides wireless access, firewall service, routing, switching,
and DHCP service to a residential customer
- Power over Ethernet (PoE)
Devices - devices that are equipped to receive their operating
power through a UTP Ethernet cable (DC) instead of through a standard
AC power cord; this technology requires a means of supplying DC power
through the Ethernet cable, which is commonly achieved by using PoE Enabled Ethernet Switches
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