Download Lecture 1 to 5 - Spartans Fall-14

Introduction and Networking Fundamental
Data networks
• Businesses needed a solution that would
successfully address the following three
problems:
– How to avoid duplication of equipment and resources
– How to communicate efficiently
– How to set up and manage a network
Network history
• In the 1980s users with stand-alone computers started to share files using
modems to connect to other computers. This was referred to as point-topoint, or dial-up communication
• Bulletin boards became the central point of communication in a dial-up
connection. Drawbacks to this type of system were:
– That there was very little direct communication
– Availability was limited to only with those who knew about the location of
the bulletin board
– Required one modem per connection. If five people connected
simultaneously it would require five modems connected to five separate
phone lines
• From the 1960s-1990s, the DoD (Department of Defense, USA) developed
large, reliable, WANs (Wide Area Networks) for military and scientific
reasons.
• In 1990, the DoDs WAN eventually became the Internet
In Our Highway Analogy...
• What is flowing?
– Traffic
• What different forms flow?
– Cars, Trucks, Buses, etc.
• What rules govern flow?
– Traffic Laws & Rules of Courtesy
• Where does the flow occur?
– Streets
In Computer Networks...
• What is flowing?
– Data
• What different forms flow?
– Text, Video, Audio
• What rules govern flow?
– Standards & Protocols
• Where does the flow occur?
– Wires, Fiber, Atmosphere
Physical Topologies
Physical topology is the actual layout of the wire or media
Logical Topology
Logical topology defines how media is accessed by hosts
1. Broadcast means that each host sends its data to all
other hosts on the network medium.
Non-deterministic - there is no order that the stations must
follow to use the network. First come, first served.
Example: Ethernet
2. Token Passing controls network access by passing an
electronic token sequentially to each host.
When a host receives the token, that host can send data
on the network.
If the host has no data to send, it passes the token to the
next host and the process repeats itself.
Examples: Token Ring, FDDI ( where Fiber Distributed Data Interface (FDDI) is a standard
for data transmission in a local area network. )
Networking Terminology
End-user devices provide users with a
connection to the network.
Also referred to as hosts.
Allow users to share, create, and obtain
information.
Note: The Macintosh or Mac, is a line
of personal computers (PCs) designed,
developed, and marketed by Apple Inc.
Network devices provide
transport for data between
end-user devices. Provide
cable connections, extensions,
concentration. Conversion of data
formats, and management of data
transfers.
Networking Terminology
Repeater: A repeater is an electronic device that receives a
network signal, cleans it of unnecessary noise, and regenerates it.
The signal is retransmitted at a higher power level, or to the other
side of an obstruction, so that the signal can cover longer
distances without degradation. In most twisted pair Ethernet
configurations, repeaters are required for cable that runs longer
than 100 meters. With fiber optics, repeaters can be tens or even
hundreds of kilometers apart.
OR
In telecommunication, the term repeater has the following standardized
meanings:
– An analog device that amplifies an input signal regardless of its nature
(analog or digital).
– A digital device that amplifies, reshapes, retimes, or performs a
combination of any of these functions on a digital input signal
for retransmission. A repeater that includes the retiming function is also
known as a regenerator.
Repeater
• Extend the physical length
• No network function has been changed
• Location is matter
Function of repeater
Repeater is not exactly as same as Amplifier
Networking Terminology (Continued..)
Hub: A repeater with multiple ports is known as a hub. Repeaters work on
the physical layer of the OSI model. Repeaters require a small amount of time
to regenerate the signal. This can cause a propagation delay that affects
network performance. As a result, many network architectures limit the
number of repeaters that can be used in a row, e.g., the Ethernet 5-4-3 rule.
Hubs have been mostly obsoleted by modern switches; but repeaters are used
for long distance links, notably undersea cabling.
Ethernet: Ethernet is a family of computer networking technologies for local
area (LAN) and larger networks. It was commercially introduced in 1980 while
it was first standardized in 1983 as IEEE 802.3
The Ethernet standards comprise several wiring and signaling variants of
the OSI physical layer in use with Ethernet. The original 10BASE5 Ethernet
used coaxial cable as a shared medium. Later the coaxial cables were replaced
with twisted pair and fiber optic links in conjunction with hubs or switches.
Data rates were periodically increased from the original 10 megabits per
second to 100 gigabits per second.
Hub
• Actually is a multiport repeater
• Star / Tree Topology
Networking Terminology (Continued..)
An Ethernet hub, active hub, network hub, repeater hub, multiport repeater or hub is a device
for connecting multiple Ethernet devices together and making them act as a single network
segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of
any port appears at the output of every port except the original incoming. A hub works at
the physical layer (layer 1) of the OSI model.
Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it
detects a collision. In addition to standard 8P8C ("RJ45") ports, some hubs may also come with
a BNC and/or Attachment Unit Interface (AUI) connector to allow connection to
legacy 10BASE2 or 10BASE5 network segments.
10BASE2 (also known as cheapernet, thin Ethernet, thinnet, and thinwire) is a variant
of Ethernet that uses thin coaxial cable (RG-58A/U or similar, as opposed to the thicker RG-8
cable used in 10BASE5 networks), terminated with BNC connectors. During the mid to late
1980s this was the dominant 10 Mbit/s Ethernet standard, but due to the immense demand for
high speed networking, the low cost of Category 5 Ethernet cable, and the popularity
of 802.11 wireless networks, both 10BASE2 and 10BASE5 have become increasingly obsolete,
though they still exist in some locations.
Where BNC (Bayonet Neill–Concelman or Baby N Connector) connector is a miniature quick
connect/disconnect radio frequency connector used for coaxial cable.
Networking Terminology (Continued..)
Ethernet over twisted pair technologies use twisted-pair cables for the physical layer of
an Ethernet computer network.
Early Ethernet cabling had generally been based on various grades of coaxial cable, but in
1984, StarLAN showed the potential of simple unshielded twisted pair by using Cat3 cable—the
same simple cable used for telephone systems. This led to the development of 10BASE-T and
its successors 100BASE-TX and 1000BASE-T, supporting speeds of 10, 100 and
1000 Mbit/s respectively.
Often the higher-speed implementations support the lower-speed standards making it possible
to mix different generations of equipment; with the inclusive capability designated 10/100 or
10/100/1000 for connections that support such combinations. All these three standards
support both full-duplex and half-duplex communication.
All these standards use 8P8C connectors, and the cables from Cat3 to Cat7 have four pairs of
wires; though 10BASE-T and 100BASE-TX only require two of the pairs.
Networking Terminology (Continued..)
Bridge: A network bridge connects and filters traffic between two network
segments at the data link layer (layer 2) of the OSI model to form a single
network. This breaks the network's collision domain but maintains a unified
broadcast domain. Network segmentation breaks down a large, congested network
into an aggregation of smaller, more efficient networks.
Bridges come in three basic types:
– Local bridges: Directly connect LANs
– Remote bridges: Can be used to create a wide area network (WAN) link
between LANs. Remote bridges, where the connecting link is slower than
the end networks, largely have been replaced with routers.
– Wireless bridges: Can be used to join LANs or connect remote devices to
LANs.
Bridge
Bridge
• Divide a large network into smaller segment
• Isolating and controlling the link problems
(e.g. congestion)
• Regenerate signal + Checking Physical Address
and forward only to the specified segment
Function of a bridge
Multiport bridge
Networking Terminology (Continued..)
Switches: A network switch is a device that forwards and filters OSI layer
2 datagrams between ports based on the MAC addresses in the packets.
A switch is distinct from a hub in that it only forwards the frames to the physical ports
involved in the communication rather than all ports connected. It can be thought of as a
multi-port bridge. It learns to associate physical ports to MAC addresses by examining the
source addresses of received frames. If an unknown destination is targeted, the switch
broadcasts to all ports but the source. Switches normally have numerous ports,
facilitating a star topology for devices, and cascading additional switches.
Multi-layer switches are capable of routing based on layer 3 addressing or additional
logical levels. The term switch is often used loosely to include devices such as routers
and bridges, as well as devices that may distribute traffic based on load or based on
application content (e.g., a Web URL identifier).
Routers: A router is an internetworking device that forwards packets between networks
by processing the routing information included in the packet or datagram (Internet
protocol information from layer 3). The routing information is often processed in
conjunction with the routing table (or forwarding table). A router uses its routing table to
determine where to forward packets. (A destination in a routing table can include a "null"
interface, also known as the "black hole" interface because data can go into it, however,
no further processing is done for said data.)
Routers
Routers in an internet
Routers
• Act like stations on a network
• Multi-home
• Definition (Goal)
– “Learning how to get from here to there."
– “Process of discovering, selecting, and employing
paths from one place to another (or to many
others) in a network” [from David M. Piscitello, Bellcore and A. Lyman Chapin, BBN]
Routing Principle
• Goal: Arriving at the destination
• Considerations:
– Direct route (shortest)
– Reliable route
– Cheap route
– Safe route
– Scenic (Attractive) route 
Network protocols
• Protocol suites are collections of protocols that enable
network communication from one host through the network
to another host.
• Protocols control all aspects of data communication such as:
–
–
–
–
–
How the physical network is built
How computers connect to the network
How the data is formatted for transmission
How that data is sent
How to deal with errors
LAN
 Operate within limited geographical area
 Allow multi-access to high bandwidth media
 Control network privately under local administration
 Provide full-time connectivity to local services
 Connect physically adjacent devices
MAN
 Spans a metropolitan area such as a city or suburban area
 Usually consists of LANs in a common geographic area
 Example: a bank with multiple branches may utilize a MAN
WAN
 Operate over a large geographical area
 Allow access over serial interfaces operating at lower speeds
 Provide full-time and part-time connectivity
 Connect devices separated over wide areas
SAN
 High-performance network to move data to/from storage areas
 Separate, dedicated network avoids traffic conflict
VPN
 Private network constructed within public network such as Internet
 Access VPNs, Intranet VPNs, Extranet VPNs
Metropolitan-area networks (MANs)
• A MAN is a network that spans a metropolitan area such as a city or
suburban area.
• Usually consists of 2 or more LANs in a common geographic area.
• Ex: a bank with multiple branches may utilize a MAN.
• Typically, a service provider is used to connect two or more LAN sites
using private communication lines or optical services.
Storage-area networks (SANs)
• A SAN is a dedicated, high-performance network used to move data
between servers and storage resources.
• Separate, dedicated network, that avoids any traffic conflict between
clients and servers
• SANs offer the following features:
– Performance – allows concurrent access of disk or tape arrays
by two or more servers at high speeds
– Availability – have disaster tolerance built in, because data can
be mirrored using a SAN up to 10km or 6.2 miles away.
– Scalability – Like a LAN/WAN, it can use a variety of
technologies. This allows easy relocation of backup data,
operations, file migration, and data replication between
systems.
SAN
Virtual private network (VPN)
• A VPN is a private network that is constructed within a
public network such as the Internet.
• It offers secure, reliable connectivity over a shared public
network infrastructure such as the Internet.
Benefits of VPNs
• Three main types of VPNs:
– Access VPNs – provide remote access to a mobile worker and a
small office/home office (SOHO) to the hq of the Intranet or
Extranet over a shared infrastructure. Access VPNs use analog,
dialup, ISDN, DSL, cable technologies
– Intranet VPNs – link regional and remote offices to the hq of the
internal network over a shared infrastructure using dedicated
connections. They allow access only to the employees of the
enterprise.
– Extranet VPNs – link business partners to the hq of the network
over a shared infrastructure using dedicated connections. They
allow access to users outside the enterprise
VPNs
Bandwidth
•
•
•
•
Bandwidth is limited by physics and technology
Bandwidth is not free
Bandwidth requirements are growing at a rapid rate
Bandwidth is critical to network performance
Throughput
Throughput refers to actual measured bandwidth, at a specific
time of day, using specific Internet routes, and while a specific
set of data is transmitted on the network.
Often far less than the maximum possible digital bandwidth.
Factors that determine throughput:
 Internetworking devices
 Type of data being transferred
T = Time S = Size
 Network topology
BW = Bandwidth
 Number of users on the network P = Throughput
 User computer
 Server computer
 Power conditions
Using layers to analyze problems in a flow of materials
• The concept of layers is used to describe communication
from one computer to another
• The information that travels on a network is generally
referred to as data or a packet
• A packet is a logically grouped unit of information that moves
between computer systems.
• As the data passes between layers, each layer adds additional
information that enables effective communication with the
corresponding layer on the other computer.
Networking Models
• The historical and technical standard of the
Internet is the TCP/IP model
• The U.S. Department of Defence created the
TCP/IP reference model, to design a network
that could survive any conditions, including a
nuclear war
Application layer handles issues of representation,
encoding, and dialog control.
 Transport layer deals with the quality of service issues
of reliability, flow control, and error correction
 Internet layer is to divide TCP segments into packets
and send them from any network. Best path determination
and packet switching occur at this layer
 Network Access layer (aka host-to-network layer)
concerned with all components, both physical and logical,
that are required to make a physical link

Application layer
•
•
•
•
•
•
Trivial File Transfer Protocol (TFTP)
File Transfer Protocol (FTP)
Network File System (NFS)
Simple Mail Transfer Protocol (SMTP)
Simple Network Management Protocol (SNMP)
Domain Name System (DNS)
Transport layer
TCP and UDP
• Segmenting upper-layer
application data
• Sending segments from
one end device to
another end device
TCP only
• Establishing
end-to-end
operations
• Flow control provided by
sliding windows
• Reliability provided by
sequence numbers and
acknowledge me
Internet layer
• The purpose of the Internet layer is to select the best path through the
network for packets to travel
• IP provides connectionless, best-effort delivery routing of packets.
• Internet Control Message Protocol (ICMP) provides control and
messaging capabilities.
• ARP resolves MAC address, for known IP addresses.
• Reverse Address Resolution Protocol (RARP) determines IP addresses
when the MAC address is known
Network access layer
The network access layer defines
the procedures for interfacing with
the
network
hardware
and
accessing
the
transmission
medium.
Drivers for software applications,
modem cards and other devices
operate at the network access
layer
OSI Model
• Reduces complexity
• Standardizes interfaces
• Facilitates modular engineering
• Ensures interoperable technology
• Accelerates evolution
• Simplifies teaching and learning
• The OSI reference model was released in 1984 to help network
builders implement networks that could communicate
(interoperability)
• The OSI reference model is the primary model for network
communications
• The process of moving information between computers is
divided into seven smaller and more manageable steps
Presentation
Session
Transport
Network
Data-Link
Physical
DATA
SEGMENT
PACKET
FRAME
BITS
0101010101010101010
DECAPSULATION
Application
Destination
ENCAPSULATION
Source
Application
Presentation
Session
Transport
Network
Data-Link
Physical
OSI Top 3 Layers – Application issues



Application
 provides network services to the user's applications
 file, print, message, database and application services
 HTTP, SMTP, FTP
Presentation
 responsible for manipulating data’s appearance as needed
by the Application layer
 Data encryption, compression and translation services
 JPEG, MIDI, QuickTime, EBCDIC to ASCII
Session
 establish and maintain communication between two hosts
 Dialogue control
 NFS, SQL, RPC
5/3/2017
NESCOT CATC
46
OSI Lower 4 Layers – Data Transport issues




Transport
 PDU (protocol data unit ) – Segment
 the transport layer establishes, maintains, and tears down virtual circuits
 Windowing
 TCP and UDP
Network
 PDU - Packet
 Routing
 Data packets and route update packets
 connectivity and path selection between two hosts
Data-Link
 PDU - Frame
 physical addressing, network topology, network access, error notification,
ordered delivery of frames, and flow control
 Ethernet LCC and MAC layers
Physical
 PDU – bits
 Cabling, standards
TCP/IP Vs OSI
Similarities of the OSI and TCP/IP models:
•
•
•
•
•
NOTE:
Both have layers
Both have application layers, though they include very different services
Both have comparable transport and network layers
Packet-switched, not circuit-switched, technology is assumed
Networking professionals need to know both models
Circuit switching is a methodology of implementing a telecommunications network in which two network
nodes establish a dedicated communications channel (circuit) through the network before the nodes may
communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the
communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit.
Differences of the OSI and TCP/IP models:
• TCP/IP combines the presentation and session layer into its
application layer
• TCP/IP combines the OSI data link and physical layers into one
layer
• TCP/IP appears simpler because it has fewer layers
• TCP/IP transport layer using UDP does not always guarantee
reliable delivery of packets as the transport layer in the OSI model
does
Connecting Devices
Networking Devices
Repeaters
Bridges
Internetworking
Devices
Routers
Gateways
Connecting Devices
Hub
Gateways (protocol converter)
A gateway
SNA network (IBM)
Netware network (Novell)
Connecting Devices
Networking Devices
Repeaters
Bridges
Internetworking
Devices
Routers
Gateways
Other devices
• Multiprotocol routers
• Brouters (Bridge Router)
• Switches
Single VS. Multiprotocol router
Brouter
Backbone Network
Bus Backbone
Star Backbone
Virtual LAN (VLAN)
VLANs create broadcast domains
VLAN with backbone switch
Copper Media
Cable specifications
Coaxial cable
Shielded twisted pair (STP)
• Costs more and harder to install
than UTP
• Must be grounded at both ends
• Reduces both internal and
external sources of interference
Unshielded twisted pair (UTP)
•
•
Relies on cancellation effect
produced by the twisting to limit
signal degradation caused by
EMI and RFI
Easier to install, thinner and less
expensive
Straight-Through, Rollover and Crossover Cables
Straight-Through
 Used for up-links
Crossover
 Used for linking devices
at the same level
Rollover
 Used for connecting a
terminal to the console
port
Cross 1 with 3 and 2 with 6
Optical Media
•
•
•
lRadio, microwaves, radar, visible light, x-rays, and gamma rays are all types of
electromagnetic waves
The wavelength of the light in optical fiber is either 850 nm, 1310 nm, or 1550 nm
In a vacuum light travels at 300,000 kps - light travels at slower speeds through air, water,
and glass
Reflection is the change in direction of a wavefront at an interface between two different media so that the
wavefront returns into the medium from which it originated.
Refraction is the change in direction of a wave due to a change in its transmission medium. Due to change of
medium, the phase velocity of the wave is changed but its frequency remains constant.
Two conditions must be met to prevent loss due to refraction and
achieve Total Internal Reflection:
1. The core of the optical fiber has to have a larger index of refraction
than the cladding.
2. The angle of incidence must be greater than the critical angle for
the core and its cladding.
The numerical aperture of a
core is the range of angles of
incident light rays entering the
fiber that will be completely
reflected .
Index of refraction (refractive
index ) “n” of a substance (optical
medium) is a dimensionless number
that describes how light, or any
other radiation, propagates through
that medium. It is defined as
, where c is the speed of light in
vacuum and v is the speed of light in
the substance.
Orange jacket
Kevlar
Plastic buffer
Cladding
Core
Other Optical Components
There are two types of light sources:
1. Light Emitting Diode (LED) producing infrared light with wavelengths of either
850nm or 1310 nm
Used with multimode fiber in LANs.
2. LASER producing a thin beam of intense infrared light with wavelengths of
1310nm or 1550 nm
Used with single-mode fiber over longer distance
Extra care should be exercised to prevent eye injury
Fibre-optic receivers are called PIN photodiodes (p-intrinsic-n diodes)
On single-mode fiber, the ST (Straight
Tip) connector is frequently used.
With multimode fiber the SC (Subscriber
Connector ) connector is used
EM Spectrum
ISM band
902 – 928 Mhz
2.4 – 2.4835 Ghz
5.725 – 5.785 Ghz
LF
30kHz
10km
MF
300kHz
1km
VHF
HF
3MHz
30MHz
100m
10m
UHF
300MHz
1m
SHF
3GHz
EHF
30GHz
300GHz
1cm
100mm
10cm


X rays

infrared visible UV
1 kHz
1 MHz
1 GHz
1 THz
1 PHz
Gamma rays
1 EHz
Propagation characteristics are different in each frequency band
 20 Hz to ~14 kHz, acoustic — normal range of adult human hearing (most children and
some animals perceive sounds outside this range, most teens and children can hear
frequencies from 14 kHz up to ~16 kHz where most adults can't)
 530 kHz to 1.710 MHz, electromagnetic — AM radio broadcasts
EM Spectrum









42 MHz to 260 MHz, electromagnetic — VHF terrestrial TV broadcast channels
88 MHz to 108 MHz, electromagnetic — FM radio broadcasts
902 MHz to 928 MHz, common cordless telephone frequency in the US
0.8 to 2.3 GHz, (electromagnetic) - mobile phone conversation channels.
2.4 GHz, (electromagnetic) - microwave ovens, Wireless LANs and cordless phones (starting in
1998).
5.8 GHz, cordless phone frequency introduced in 2003
428 THz to 750 THz, electromagnetic — visible light, from red to violet
30 Petahertz (PHz), electromagnetic — x-rays
300 Exahertz (EHz) and above - gamma rays
Designation
Frequency
Wavelength
ELF
extremely low frequency
3Hz to 30Hz
100'000km to 10'000 km
SLF
superlow frequency
30Hz to 300Hz
10'000km to 1'000km
ULF
VLF
LF
ultralow frequency
very low frequency
low frequency
300Hz to 3000Hz
3kHz to 30kHz
30kHz to 300kHz
1'000km to 100km
100km to 10km
10km to 1km
MF
medium frequency
300kHz to 3000kHz
1km to 100m
HF
high frequency
3MHz to 30MHz
100m to 10m
VHF
very high frequency
30MHz to 300MHz
10m to 1m
UHF
ultrahigh frequency
300MHz to 3000MHz
1m to 10cm
SHF
superhigh frequency
3GHz to 30GHz
10cm to 1cm
EHF
extremely high frequency
30GHz to 300GHz
1cm to 1mm
EM Spectrum









42 MHz to 260 MHz, electromagnetic — VHF terrestrial TV broadcast channels
88 MHz to 108 MHz, electromagnetic — FM radio broadcasts
902 MHz to 928 MHz, common cordless telephone frequency in the US
0.8 to 2.3 GHz, (electromagnetic) - mobile phone conversation channels.
2.4 GHz, (electromagnetic) - microwave ovens, Wireless LANs and cordless phones (starting in
1998).
5.8 GHz, cordless phone frequency introduced in 2003
428 THz to 750 THz, electromagnetic — visible light, from red to violet
30 Petahertz (PHz), electromagnetic — x-rays
300 Exahertz (EHz) and above - gamma rays
Designation
Frequency
Wavelength
ELF
extremely low frequency
3Hz to 30Hz
100'000km to 10'000 km
SLF
superlow frequency
30Hz to 300Hz
10'000km to 1'000km
ULF
VLF
LF
ultralow frequency
very low frequency
low frequency
300Hz to 3000Hz
3kHz to 30kHz
30kHz to 300kHz
1'000km to 100km
100km to 10km
10km to 1km
MF
medium frequency
300kHz to 3000kHz
1km to 100m
HF
high frequency
3MHz to 30MHz
100m to 10m
VHF
very high frequency
30MHz to 300MHz
10m to 1m
UHF
ultrahigh frequency
300MHz to 3000MHz
1m to 10cm
SHF
superhigh frequency
3GHz to 30GHz
10cm to 1cm
EHF
extremely high frequency
30GHz to 300GHz
1cm to 1mm
IEEE Standards for Wireless
Wireless Media
802.11
802.11b
802.11a
802.11g
Includes Direct Sequence Spread Spectrum (DSSS)
applies to wireless devices operating within a 1 to 2 Mbps
range
Wi-Fi™ - Increased transmission capabilities to 11 Mbps
Typically speeds 2 to 4 Mbps
All 802.11b systems are backward compliant
Operate within 2.4 GHZ transmission band
Operate within 5 GHZ transmission band
No interoperability with 802.11b
Capable of throughput of 54 Mbps (typically 20-26 Mbps)
Same throughout as 802.11a
Backwards compatibility for 802.11b
Uses Othogonal Frequency Division Multiplexing (OFDM)
Wireless Devices and Topologies
Wireless network may consist of as few as two devices equipped with
wireless network interface controllers (NICs)
Access Point (AP) are installed to act as central hubs for the WLAN and to
solve NIC compatibility issues
APs are equipped with antennae and provide wireless connectivity over a specified area
referred to as a cell
• Three types of frames are used in wireless communication:
control, management, and data
• WLANs use CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance)
• WLAN authentication authenticates the device, not the user
• Authentication and Association types
1. Unauthenticated and unassociated
2. Authenticated and unassociated - The node has been
authenticated on the network but has not yet associated with the
access point
3. Authenticated and associated
• Wireless security can be difficult to achieve. Tools include:
EAP-MD5 Challenge, LEAP (Cisco), User authentication,
Encryption, Data authentication
• VPN technology effectively closes the wireless network