UNIT 3

WLAN Topologies, WLAN Standard IEEE 802.11, Comparison Of IEEE 802.11a, B, G

and N Standards, Wireless PANs, Hiper LAN, Wireless Local Loop, ATM, Virtual Private
Networks, Wireless Data Services, Common Channel Signaling, Various Networks for
Connecting to The Internet.

1.WLAN Topologies
WLAN Topologies
802.11 networks are flexible by design. You have the option of deploying three types of WLAN topologies:
 Independent basic service sets (IBSSs)
 Basic service sets (BSSs)
 Extended service sets (ESSs)
A service set is a logical grouping of devices. WLANs provide network access by broadcasting a signal across a wireless radio
frequency (RF) carrier. A receiving station can be within range of a number of transmitters. The transmitter prefaces its
transmissions with a service set identifier (SSID). The receiver uses the SSID to filter through the received signals and locate the
one it wants to listen to.

IBSS
 An IBSS consists of a group of 802.11 stations communicating directly with
one another. An IBSS is also referred to as an ad-hoc network because it is essentially a simple peer-to-peer WLAN. Figure 2-1
illustrates how two stations equipped with 802.11 network interface cards (NICs) can form an IBSS and communicate directly
with one another.

BSS

A BSS is a group of 802.11 stations communicating with one another. A BSS

requires a specialized station known as an access point (AP). The AP is the central point of communications for all stations in a
BSS. The client stations do not communicate directly other client stations. Rather, they communicate with the AP, and the AP
forwards the frames to the destination stations. The AP might be equipped with an uplink port that connects the BSS to a wired
network (for example, an Ethernet uplink). Because of this requirement, a BSS is also referred to as an infrastructure BSS. Figure
2-2 illustrates a typical infrastructure BSS.

ESS

Multiple infrastructure BSSs can be connected via their uplink interfaces. In

the world of 802.11, the uplink interface connects the BSS to the distribution system (DS). The collection of BSSs interconnected
via the DS is known as the ESS. Figure 2-3 shows a practical implementation of an ESS. The uplink to the DS does not have to be
via a wired connection. The 802.11 specification leaves the potential for this link to be wireless. For the most part, DS uplinks are
wired Ethernet.

2 WLAN STANDARD IEEE 802.11

IEEE 802.11 standard, popularly known as WiFi, lays down the architecture and specifications of wireless LANs (WLANs).
WiFi or WLAN uses high frequency radio waves for connecting the nodes.
There are several standards of IEEE 802.11 WLANs. The prominent among them are 802.11, 802.11a, 802.11b, 802.11g, 802.11n
and 802.11p. All the standards use carrier-sense multiple access with collision avoidance (CSMA/CA). Also, they have support
for both centralised base station based as well as ad hoc networks.
1.IEEE 802.11

IEEE 802.11 was the original version released in 1997. It provided 1 Mbps or 2 Mbps data rate in the 2.4 GHz band and used
either frequency-hopping spread spectrum (FHSS) or direct-sequence spread spectrum (DSSS). It is obsolete now.

2.IEEE 802.11a
802.11a was published in 1999 as a modification to 802.11, with orthogonal frequency division multiplexing (OFDM) based air
interface in physical layer instead of FHSS or DSSS of 802.11. It provides a maximum data rate of 54 Mbps operating in the 5
GHz band. Besides it provides error correcting code. As 2.4 GHz band is crowded, relatively sparsely used 5 GHz imparts
additional advantage to 802.11a.
Further amendments to 802.11a are 802.11ac, 802.11ad, 802.11af, 802.11ah, 802.11ai, 802.11aj etc.
3.IEEE 802.11b
802.11b is a direct extension of the original 802.11 standard that appeared in early 2000. It uses the same modulation technique as
802.11, i.e. DSSS and operates in the 2.4 GHz band. It has a higher data rate of 11 Mbps as compared to 2 Mbps of 802.11, due to
which it was rapidly adopted in wireless LANs. However, since 2.4 GHz band is pretty crowded, 802.11b devices faces
interference from other devices.
Further amendments to 802.11b are 802.11ba, 802.11bb, 802.11bc, 802.11bd and 802.11be.

4.IEEE 802.11g
802.11g was indorsed in 2003. It operates in the 2.4 GHz band (as in 802.11b) and provides a average throughput of 22 Mbps. It
uses OFDM technique (as in 802.11a). It is fully backward compatible with 802.11b. 802.11g devices also faces interference from
other devices operating in 2.4 GHz band.

5.IEEE 802.11n

802.11n was approved and published in 2009 that operates on both the 2.4 GHz and the 5 GHz bands. It has variable data rate
ranging from 54 Mbps to 600 Mbps. It provides a marked improvement over previous standards 802.11 by incorporating multiple-
input multiple-output antennas (MIMO antennas).

6.IEEE 802.11p
802.11 is an amendment for including wireless access in vehicular environments (WAVE) to support Intelligent Transportation
Systems (ITS). They include network communications between vehicles moving at high speed and the environment. They have a
data rate of 27 Mbps and operate in 5.9 GHz band.

3.IEEE Wireless Standards & Comparsions of IEEE 802.11Aa,B,G,and N

standards
The Wi-Fi Alliance created a naming system to aid the general public in differentiating between different versions of IEEE 802.11.

 IEEE 802.11: This is the original standard created in 1997 but currently defunct. The version supports a maximum
connection speed of 1Mbps. Unfortunately, devices using this version are no longer produced and don’t work on today’s
equipment.
  IEEE 802.11a: This second version was developed in 1999 and works on a 5GHz Wi-Fi band. The version was released
hoping that it will encounter less interference, especially since most devices then used the 2.4GHz band. Nonetheless,
IEEE 802.11a is faster, with maximum data rates of 1.5Mbps to 54Mbps.
 IEEE 802.11b: This version was also developed in 1999 but used the typical unregulated radio signaling frequency of the
2.4GHz band. It comes with a maximum speed of 11Mbps, and it is the version that increased Wi-Fi’s popularity. Most
vendors preferred using these frequencies due to low production costs. Unfortunately, its unregulated nature means that
IEEE 802.11b can face interference from cordless phones, ovens, and all other devices using the 2.4GHz range.
 IEEE 802.11g: This 2003 sequel improved the maximum data rates of 54Mbps while maintaining the reliable 2.4GHz band
usage, which explains its widespread adoption. Also called Wi-Fi 3, this standard combines the good features of IEEE
802.11b and IEEE 802.11a. As such, it is compatible with backward technologies, meaning that 802.11b APs can work with
IEEE 802.11g adapters.
 IEEE 802.11n: The IEEE 802.11n, otherwise called Wireless N or Wi-Fi 4, was developed to improve the bandwidth rates
provided by IEEE 802.11g. This standard uses several antennas and wireless signals, popularly known as MIMO
technology, contrary to the one used by IEEE 802.11g. 802.11n was ratified by industry standards in 2009, enabling it to
provide maximum network bandwidths of 600Mbps. It also offers a better Wi-Fi range compared to previous standards
since it has a higher signal intensity. The only drawback of this standard is that it is more expensive than IEEE 802.11g.
 IEEE 802.11ac: Also called Wi-Fi 5, this Wi-Fi standard was created in 2014 and primarily supports the 5GHz frequency
band. It offers increased bandwidth, with potential speeds exceeding 1Gbps using multiple spatial streams and advanced
modulation techniques. While the standard operates on 5GHz for high speeds, it also supports 2.4GHz frequencies to
maintain compatibility with older devices. It is backward compatible with previous Wi-Fi standards such as 802.11a/b/g/n.
This was the initial Wi-Fi standard that facilitated the utilization of multiple input/multiple output (MIMO) technology,
allowing the use of multiple antennas on both transmitting and receiving devices to minimize errors and enhance speed.
 IEEE 802.11ax: The IEEE 802.11ax, also known as Wi-Fi 6, is the recent and game-changing Wi-Fi standard that is up to 10
times faster than 802.11ac. It features a maximum data rate of 1.3Gbs and operates on both 2.4GHz and 5GHz
frequencies.

Here is the 802.11 standard chart to help you understand the differences more intuitively:

Standar Year Frequency Range Range

Speed
d Released (GHz) (Indoor) (Outdoor)
 802.11 1997 2.4 2Mbps 20m 100m

802.11a 1999 5 1.5-54Mbps 35m 120/5000m

802.11b 1999 2.4 11Mbps 35m 120m

802.11g 2003 2.4 54Mbps 38m 140m

802.11n 2009 2.4/5 600Mbps 70m 250m

802.11ac 2013 2.4/5 450/1300Mbps 35m -

802.11ax 2019 2.4/5 10-15Gbs 30m 120m

IEEE 802.11ac and 802.11ax Comparison

While both 802.11ac and 802.11ax provide robust performance for modern wireless networks, they differ significantly in their
design goals and practical applications. 802.11ac is popular for its high throughput and low latency, especially when dealing with
high-definition video streaming and online gaming. It relies heavily on the 5GHz band for compatibility with older devices. In
contrast, 802.11ax not only more than doubles the speed of 802.11ac, but also introduces advanced technologies such as
OFDMA and MU-MIMO, which significantly increase the efficiency and capacity of the network. 802.11ax not only supports the
2.4GHz and 5GHz frequency bands but also has the ability to expand into the future 6GHz frequency band, making it the ideal
solution for future IoT devices and high-density network environments. IEEE 802.11ax not only supports the 2.4GHz and 5GHz
bands but also has the ability to expand to the future 6GHz band, making it ideal for future IoT devices and high-density network
environments.
4.WPAN :
Wireless Personal Area Network in short known as WPAN. Actually WPAN is PAN (Personal Area Network) where the
interconnected devices are centered around a person’s workspace and connected through wireless medium. That’s why it is
also called as Person’s centered short range wireless connectivity. Typically the range is within about 10 meters means very
short range. Plugging in is one of the key concept in WPAN as within a close proximity WPAN-equipped devices communicate
with each other as like they are connected through cable. Unlike WLAN (Wireless Local Area Network) where there is a
requirement of infrastructure setup, in WPAN connection involves little or no infrastructure. In general, if we will see this
WPAN provides power efficient and inexpensive solutions to be implemented for a wide range of devices within a short range
distance.
As in WPAN mostly the connection between the devices happens within the building or in a room (short range) So, let’s take
an example of WiFi connection through which two friends are chatting, sharing documents with each other in room.
Some more examples of WPAN includes Wireless mouse, Wearable devices, USB flash drives, Digital cameras, Bluetooth, Wi-
Fi, Thermostats, Security systems, Lighting controls, Motion sensors, Personal server and Leak sensors etc.
As per IEEE, Wireless Personal Area Network is classified into 3 classes i.e
1. High-rate WPAN (HR-WPAN) : It is defined in the IEEE 802.15.3 standard. Data throughput is > 20 Mbps.
2. Medium-rate WPAN (MR-WPAN) : It is defined in the IEEE 802.15.1 standard. Data throughput is 1 Mbp.
3. Low-rate WPAN (LR-WPAN) : It is defined in the IEEE 802.15.4 standard. Data throughput is < 0.25 Mbps.
Applications of WPAN :
 Short range connectivity for multimedia applications
  Hands free devices connection
 Industrial sensor applications
WPAN Topologies :
As mostly use of WPAN is within short range so it is mainly used for general purpose uses and with little industrial requirement
implementations which supports below network connectivity arrangements (network topology)
1. Star Topology
1. Mesh Topology
2. Cluster Tree Topology
Technologies used in WPAN :
1. Bluetooth
2. ZigBee
3. Infrared
4. Z-wave
5. Wireless Body Area Network (WBAN)
Features of WPAN :
 Low cost, Little or No infrastructure setup
 Short range communication
 Small personal network , use anywhere
 Wide range of devices
 Low power consumption
 No complex connectivity
Advantages of WPAN :
 Security
 Portability
 Easy Connectivity
 Stability
Disadvantages of WPAN :
 Short range
 Transfer speed

5.HIPERLAN
 The main idea behind HIPERLAN is to provide an infrastructure or ad-hoc wireless system with a small radius.

HIPERLAN emerged in 1991 with the goal of achieving higher data rates than the 802.11 standard. It was approved in 1996. A
second version was introduceced in 2000. This version is designed as a fast wireless connection and can be used with various
networks, such as UMTS backbone, ATM, and IP networks. HiperLAN/2 can also be used as a home network and supports a data
rate of up to 54 Mbps.

Components of a HIPERLAN include:

 Physical Layer: This layer provides the standard functions, including radio frequency functions.
 Link Adaptation: This standard allows the access point to convey information in an uplink or downlink direction. The
HIPERLAN physical layer also specifies some link adaptation algorithms to be used.
 Data Link Control (DLC) Layer: This layer includes the Media Acces Control (MAC), Radio Link Control (RLC), Dynamic
Frequency Selection (DFS) and Error Control (EC) protocols.
 Convergence Layer: Its basic function is to provide the HIPERLAN DLC and physical access to other data networks.
HiperLAN (High Performance Radio LAN) is a wireless LAN standard developed as a European alternative to the IEEE 802.11
standards. Let me break it down for you:
1. HiperLAN/1:
o Planning for the first version of the standard, called HiperLAN/1, began in 1992, while planning for IEEE 802.11 was
already underway.
o The goal of HiperLAN/1 was to achieve a higher data rate than 802.11.
o Approved in 1997, HiperLAN/1 covers the physical layer and the media access control (MAC) part of the data link
layer.
o It features a new sublayer called the Channel Access and Control sublayer (CAC), which handles access requests to
channels.
o HiperLAN/1 uses FSK and GMSK modulations in the 5 GHz frequency range.
o Notably, it can forward data packets using several relays, extending communication beyond the radio range.
1
o Power-saving nodes (p-savers) set specific wake-up patterns to conserve energy .
2. HiperLAN/2:
o HiperLAN/2, completed in February 2000, is designed for fast wireless connections across various networks.
o It operates in the 5 GHz band and supports data rates of up to 54 Mbit/s.
o HiperLAN/2 serves as a backbone network for UMTS, ATM, IP networks, and even home networks like HiperLAN/1
.
6.WLL Architecture:
The Wireless Local Loop (WLL) architecture replaces traditional copper wires with wireless links, connecting subscribers to the
local central office. It consists of several components, including the PSTN (Public Switched Telephone Network), Switch
Function, WANU (Wireless Access Network Unit), and WASU (Wireless Access Subscriber Unit).
The PSTN serves as a circuit-switched network, while the Switch Function manages connections between WANUs. The WANU
takes care of authentication, operation, routing, and data transmission, whereas the WASU is installed at the subscriber’s
location. With its cost-effectiveness, enhanced security through digital encryption, scalability options, and various features like
internet access, voice services, data transfer capabilities, and fax services – WLL proves to be a dependable solution for
telecommunication requirements specifically in remote or rural areas.

WLL components:
1. PSTN: It is Public Switched Telephone Network which is a circuit switched network. It is a collection of world’s
interconnected circuit switched telephone networks.
2. Switch Function: Switch Function switches the PSTN among various WANUs.
3. WANU: It is short for Wireless Access Network Unit. It is present at the local exchange office. All local WASUs are
connected to it. Its functions includes: Authentication, Operation & maintenance, Routing, Transceiving voice and
data. It consists of following sub-components:
 Transceiver: It transmits/receives data.
 WLL Controller: It controls the wireless local loop component with WASU.
 AM: It is short for Access Manager. It is responsible for authentication.
  HLR: It is short for Home Location Register. It stores the details of all local WASUs.
4. WASU: It is short for Wireless Access Subscriber Units. It is present at the house of the subscriber. It connects the
subscriber to WANU and the power supply for it is provided locally.
5. Advantages of WLL:

 It eliminates the first mile or last mile construction of the network connection.
 Low cost due to no use of conventional copper wires.
 Much more secure due to digital encryption techniques used in wireless communication.
 Highly scalable as it doesn’t require the installation of more wires for scaling it.
6. Features of WLL:

 Internet connection via modem

 Data service
 Voice service
 Fax service

7.What Is an Automated Teller Machine (ATM)?

An automated teller machine (ATM) is an electronic banking outlet that allows customers to complete basic transactions
without the aid of a branch representative or teller. Anyone with a credit card or debit card can access cash at most ATMs,
either in the U.S. or other countries.

ATMs are convenient, allowing consumers to perform quick self-service transactions such as deposits, cash withdrawals, bill
payments, and transfers between accounts.

Fees are commonly charged for cash withdrawals by the bank where the account is located, by the operator of the ATM, or by
both. Some or all of these fees can be avoided by using an ATM operated directly by the bank network that holds the account.
Using an ATM abroad can cost more than using one in the U.S. due to exchange rates or transaction fees

The first ATM appeared at a branch of Barclays Bank in London in 1967, though there are reports of a cash dispenser in use in
Japan in the mid-1960s.23 The interbank communications networks that allowed a consumer to use one bank’s card at another
bank’s ATM followed in the 1970s.

Within a few years, ATMs had spread around the globe, securing a presence in every major country. They now can be found
even in tiny island nations such as Kiribati and the Federated States of Micronesia.4
The World Bank, World Bank Open Data. “Automated Teller Machines (ATMs) (Per 100,000 Adults) .”
ATMs are also known automated bank machines (ABMs), cashpoints, or cash machines.

Types of ATMs

There are two main types of ATMs. Basic units only allow you to withdraw cash and receive updated account balances.

Types of ATMs
There are two types of ATMs. The simple basic unit helps you to check your bank account balance, withdraw money, get a mini
account statement, change your ATM PIN, or receive bank account updates. There are other complex units that provide facilities
for cheque or cash deposits as well as a line of credit.

Apart from this, there are onsite and offsite ATMs. The onsite ATMs are installed within the bank premises, whereas the offsite
ATMs are present in various parts of the country to ensure that people can avail the basic banking facilities without visiting a
bank branch.

ATMs can be Categorized into the Following Labels:

 Orange Label ATMs: Share transactions

 Yellow Label ATMs: e-commerce transactions
 Green Label ATMs: Agricultural transactions
 White Label ATMs: Owned by TATA Group
 Pink Label ATMs: For female customers
 Brown Label ATMs: Operated by a third-party service provider

Advantages of ATMsr

The following are the advantages of ATMs:

 Banks provide ATM services 24*7.

 It helps in reducing the workload on bank staff.
 ATMs provide seamless services without any error.
 ATMs are a better resource for travellers.
Functions of ATMs
Given below are the functions of ATMs:

 Cash withdrawal
 Mini account statement
 Cash transfer
 Account balance details
 Deposit of money

Basic Parts of an ATM

Given below are the basic parts of an ATM:

Input Devices

 Keypad: Keypad is used to insert numbers, clear them or cancel a transaction. The customers use keypads to enter their
ATM PIN and the cash amount that they want to withdraw
 Card Reader: An ATM consists of a space where you can insert your ATM card. The ATM card contains a magnetic card on
its back that has the account details. The card reader gathers the account information and sends it to the server.

Output Devices

 Cash Dispenser: Cash is stocked in the ATM by the bank officials. The cash dispenser helps you to collect cash after
withdrawing a specific amount from the ATM.
 Display Screen: The display screen guides the user about the steps related to cash withdrawal, checking account balance,
or changing ATM PIN.
 Speaker: There is a speaker in every ATM which provides audio instructions to carry out transactions and access the
machine.
 Receipt Printer: Once the ATM transaction is completed, the receipt printer records the transaction type, remaining
account balance, and amount withdrawn.

ATMs have increased the convenience and accessibility of the people. You can withdraw money at any time, including
on holidays and after business hours.
8.What is a VPN?
A virtual private network (VPN) is a technology that creates a safe and encrypted connection over a less secure network, such
as the Internet. A Virtual Private Network is a way to extend a private network using a public network such as the Internet.
The name only suggests that it is a “Virtual Private Network”, i.e. user can be part of a local network sitting at a remote
location. It makes use of tuneling protocols to establish a secure connection.History of VPNs
ARPANET introduced the idea of connecting distant computers in the 1960s. The foundation for current internet connectivity
was established by ensuring the development of protocols like TCP/IP in the 1980s. Particular VPN technologies first appeared
in the 1990s in response to the growing concerns about online privacy and security.
How Does a VPN Work?
Let us understand VPN with an example think of a situation where the corporate office of a bank is situated in Washington,
USA. This office has a local network consisting of say 100 computers. Suppose other branches of the bank are in Mumbai,
India, and Tokyo, Japan. The traditional method of establishing a secure connection between the head office and the branch
was to have a leased line between the branches and head office which was a very costly as well as troublesome job. VPN lets
us effectively overcome this issue.
The situation is described below
 All 100 hundred computers of the corporate office in Washington are connected to the VPN server(which is a well-
configured server containing a public IP address and a switch to connect all computers present in the local network
i.e. in the US head office).
 The person sitting in the Mumbai office connects to The VPN server using a dial-up window and the VPN server
returns an IP address that belongs to the series of IP addresses belonging to a local network of the corporate office.
 Thus person from the Mumbai branch becomes local to the head office and information can be shared securely over
the public internet.
 So this is the intuitive way of extending the local network even across the geographical borders of the country.
VPN is well Exploited all Across the Globe
We will explain to you with an example. Suppose we are using smartphones regularly. Spotify Swedish music app that is not
active in India But we are making full use of it sitting in India. So how ?? VPN can be used to camouflage our geolocation.
 Suppose the IP address is 101.22.23.3 which belongs to India. That’s why our device is not able to access the Spotify
music app.
 But the magic began when we used the Psiphon app which is an Android app used to change the device IP address to
the IP address of the location we want(say US where Spotify works seamlessly).
  The IP address is changed using VPN technology. Basically what happens is that your device will connect to a VPN
server of the respective country that you have entered in your location textbox of the Psiphon app and now you will
inherit a new IP from this server.
Now we typed “What is my IP address”? Amazingly the IP address changed to 45.79.66.125 which belongs to the USA And
since Spotify works well in the US, we can use it now being in India (virtually in the USA). Is not that good? obviously, it is very
useful.

 VPN also ensures security by providing an encrypted tunnel between the client and the VPN server.
 VPN is used to bypass many blocked sites.
 VPN facilitates Anonymous browsing by hiding your IP address.
 Also, the most appropriate Search engine optimization (SEO) is done by analyzing the data from VPN providers which
provide country-wise statics of browsing a particular product.
 VPNs encrypt your internet traffic, safeguarding your online activities from potential eavesdropping and cyber
threats, thereby enhancing your privacy and data protection.
Types of VPN
There are several types of VPN and these are vary from specific requirement in computer network. Some of the VPN are as
follows:
1. Remote Access VPN
2. Site to Site VPN
3. Cloud VPN
4. Mobile VPN
5. SSL VPN
For more details you can refer Types of VPN published article.
VPN Protocols
 OpenVPN: A cryptographic protocol that prioritises security is called OpenVPN. OpenVPN is compatible protocol that
provides a variety of setup choices.
 Point-To-Point Tunneling Protocol(PPTP): PPTP is not utilized because there are many other secure choices with
higher and more advanced encryption that protect data.
 WireGuard: Wireguard is a good choice that indicates capability in terms of performance.
 Secure Socket Tunneling Protocol(SSTP): SSTP is developed for Windows users by Microsoft. It is not widely used due
to the lack of connectivity.
 Layer 2 Tunneling Protocol(L2TP) It connects a user to the VPN server but lacks encryption hence it is frequently
used with IPSec to offer connection, encryption, and security simultaneously.
Why Should Use VPN?
 For Unlimited Streaming: Love streaming your favourite shows and sports games? A VPN is your ultimate companion
for unlocking streaming services.
 For elevating your Gaming Experience: Unleash your gaming potential with the added layer of security and
convenience provided by a VPN. Defend yourself against vengeful competitors aiming to disrupt your gameplay while
improving your ping for smoother, lag-free sessions. Additionally, gain access to exclusive games that may be
restricted in your region, opening up a world of endless gaming possibilities.
 For Anonymous Torrenting: When it comes to downloading copyrighted content through torrenting, it’s essential to
keep your IP address hidden. A VPN can mask your identity and avoid potential exposure, ensuring a safe and private
torrenting experience.
 For supercharging your Internet Speed: Are you tired of your Internet speed slowing down when downloading large
files? Your Internet Service Provider (ISP) might be intentionally throttling your bandwidth. Thankfully, a VPN can
rescue you by keeping your online activities anonymous, effectively preventing ISP throttling. Say goodbye to sluggish
connections and embrace blazing-fast speeds.
  Securing Public Wi-Fi: VPNs are essential for maintaining security when using public Wi-Fi networks, such as those in
coffee shops, airports, or hotels. These networks are often vulnerable to cyberattacks, and using a VPN encrypts your
internet connection, protecting your data from potential hackers and eavesdroppers when you connect to untrusted
Wi-Fi hotspots.
Are VPNs legal or illegal?
Using a VPN is legal in most countries, The legality of using a VPN service depends on the country and its geopolitical relations
with another country as well. A reliable and secure VPN is always legal if you do not intend to use it for any illegal activities
like committing fraud online, cyber theft, or in some countries downloading copyrighted content. China has decided to block
all VPNs (Virtual private network) by next year, as per the report of Bloomberg. Many Chinese Internet users use VPNs to
privately access websites that are blocked under China’s so-called “great firewall”. This is done to avoid any information
leakage to rival countries and to tighten the information security.
What to Look for When Choosing a VPN?
 Be sure the VPN has appropriate speed, a lot of providers have trouble keeping up with Netflix viewing or
downloading.
 Read both user and expert evaluations to gain a good idea of how well the VPN operates.
 Select a VPN provider that provides shared IP addresses.
 More servers translate into faster browsing because there will be less traffic on each one.
Benefits of VPN
 When you use VPN it is possible to switch IP.
 The internet connection is safe and encrypted with VPN
 Sharing files is confidential and secure.
 Your privacy is protected when using the internet.
 There is no longer a bandwidth restriction.
 It facilitates cost savings for internet shopping.
Limitations of VPN
 VPN may decrease your internet speed.
 Premium VPNs are not cheap.
 VPN usage may be banned in some nations.

9.Wireless Data Services

CPDP(Cellular Digital Packet Data) CPDP technology is used by telecommunication carriers to transfer data to
users via unused analog cellular networks. It uses the entire 30KHz channel of AMPS on shared basis. No extra
bandwidth required as it overlays itself on AMPS radio channels. Inexpensive and easy to construct. CPDP
doesn’t use MSC for routing, rather it has its own traffic routing capabilities. CPDP radio channel varies with
time.

1. CPDP(Cellular Digital Packet Data)

Every CPDP channel is duplex in nature with conventional first generation AMPS.

CDPD Infrastructur
CDPD - Layering

Application

Transport

Network Connectionless Network Protocol

IP/
CLNP Radio Resource Management Protocol
Data link RRMP
Mobile Data Link Protocol
MDLP
Media Access Control
Physical MAC
Physica Physical

Network layer CDPD Layer

CDPD Physical Layer

• 30KHz BW channels, shared with AMPS

• Separate forward and reverse channels

– Forward channel is continuous

– Reverse channel is multiple access.

• Gaussian Minimum-Shift Keying-GMSK

– GMSK compromises between channel bandwidth and decoder complexity.

• 19.2kbps per channel.
IP/CLNP
RRMP
MDLP
MAC
Physical
CPDP – Data Link Layer-MDLP

• Provides logical data link connections on a radio channel by using the address contained in each packet
frame.
• Takes care of the packet sequence control.
• Error detection and flow control of the packet

CPDP-Layer 3-RRMP

• Manages radio channel resources of a CPDP system and enables M-ES to find the radio channel
without interfering with the AMPS communication.
• Handles BS identification and configuration messages for all M-ES stations.
Handles channel hopping commands, cell handoffs and M-ES change of power commands
 AMPS and CDPD

• CDPD runs alongside AMPS

– AMPS system is unaware of CDPD system

– CDPD system watches AMPS behavior

• AMPS generally has unused channels.

– Blocked calls when all channels are allocated.

– 1% block probability => all channels used only 1% of the time.

– Every time MSC chooses a channel for the BS, 30% of channel time is unused, which is exploited by the
CPDP network.
 Effects of CDPD on AMPS

• CDPD logically transparent to AMPS

• Can reduce AMPS service quality
– More channel usage by CDPD => increasedinterference.

Problems with CDPD

• Limited bandwidth
– 19.2kbps shared per channel
– Modern applications demand more bandwidth.
• Security
– “Man in the middle” identity theft attack
– IP network attacks
– Denial of Service attacks easy.

Potential Improvements

• Multichannel / multicarrier transmission

– Would allow faster rates with AMPS compatibility.
 • Security Improvements
– Secure against “man-in-the-middle” attacks.
• Switch to CDMA/GSM.
– Digital cellular services are more able to accommodate data services.

ARDIS(Advanced Radio Data Information Systems)

Channel Characteristics of ARDIS

Type of Message Retry Rate Packet Overhead

Short ARDIS Low High

message

Long ARDIS High Spread over the lgt.

message
Of the packet
 RAM Mobile Data (RMD)

named MOBITEX
 9.Common channel signaling

Common Channel Signaling

Purpose
In a multi-channel communications system, Common Channel Signaling (CCS) is signaling in which one channel in each link is
used for signaling to control, account for, and manage traffic on all channels of the link. The channel used for common-channel
signaling does not carry user information. With CCS, signals are carried by a separate network consisting of Signaling Data Links
(SDLs) and Signaling Transfer Points (STPs) to transfer digital signaling messages between exchanges. It is known as CCS because
SDLs can carry messages for trunks in many different trunk groups.
Supported Protocols
The CSP supports the following CCS protocols:
• Signaling System 7
• Integrated Services Digital Network
• Q Signaling (QSIG)
• DASS2/DPNSS
• V5.2 (Local Exchange side)
SS7
A telecommunications network served by common channel signaling is composed of a number of switching and processing
nodes interconnected by transmission links. To communicate using SS7, each of these nodes must implement the necessary
"within node" features of SS7 making that node a signaling point within the SS7 network. In addition, there is a need to
interconnect these signaling points such that SS7 signaling data may be conveyed between them. These data links are the
signaling links of the SS7 signaling network.
The combination of signaling points and their interconnecting signaling links form the SS7 signaling network.
ISDN
The main feature of Integrated Services Digital Network (ISDN) is the support of a wide range of service capabilities, including
voice and non-voice applications, in the same network by offering end-to-end digital connectivity. A key element of service
integration for an ISDN is the provision of a limited set of standard multi-purpose user-network interfaces. These interfaces
represent a focal point both for the development of ISDN network components and configurations and for the development of
ISDN terminal equipment and applications.
QSIG
The CSP supports the QSIG/PSS1 global signaling and control standard for Private Integrated Network Exchange (PINX)
applications, intended for use in private corporate ISDN networks. QSIG is a Euro-ISDN based protocol for digital Common
Channel Signaling (CCS) and is used to build private networks using Virtual Private Networks (VPNs) or leased lines.
Q Signaling (QSIG), an ISDN based protocol, enables signaling between different voice communications platforms and equipment
(nodes) in a multi-user environment. It is often referred to as an inter-PBX signaling system. It can also be deployed in a single-
user environment.
Internationally, QSIG is also known as Private Signaling System No. 1 (PSS1).
DASS2
DASS2 is a message-based signaling system following the ISO-based model developed by British Telecom to provide multi-line
Integrated Digital Access (IDA) interconnection to the BT network.
DPNSS
Digital Private Network Signaling System is a standard in Britain which enables Private Branch Exchanges (PBXs) from different
manufacturers to be tied together with E1 lines and pass calls transparently between each. The calls are made as easily as if the
phones were extensions off the same PBX and were simply intercom calls.
V5.2
V5.2 is a concentration protocol for digital Common Channel Signaling (CCS). It is called a concentration protocol because it can
accommodate more subscribers than existing physical ports. The V5.2 protocol is comprised of the LE (Local Exchange) side of
the protocol. The V5.2 protocol is used to establish, maintain, and release calls between an LE and an AN.
Excel’s V5.2 products include the hardware and software required to run and manage V5.2 on the Converged Services
Platform (CSP). This implementation supports only the Local Exchange (LE) side of V5.2.

11.Types of Internet Connection

An internet connection is a means by which individual devices or local networks are linked to the global internet, allowing them
to communicate and exchange data. There are many connections that can be used for internet access. All the connections have
their own speed range that can be used for different purposes like for home, or for personal use. In this article, we will discuss
different types of internet connections.
What is the Internet?
The Internet is a global network of computers connected. It allows people all over the world to communicate, share information,
and access a huge amount of data. You can use the Internet to send emails, browse websites, watch videos, play games, and
much more. It’s like a huge library and playground that you can access from your computer, phone, or other devices anytime and
anywhere.
Types of Internet Connection
1. Dial-Up Connection
A dial-up connection is established between your computer and the ISP server using a modem. A dial-up Connection is a cheap
and traditional connection that is not preferred these days as this type of connection is very slow.
To access the internet connection in the dial-up connection we need to dial a phone number on the computer and that’s why it
requires a telephone connection. It requires a modem to set up a dial-up connection, which works as interference between your
computer and the telephone line. In this connection, we can use either an internet connection or a telephone at a time.

Dial Up Connection
2. Broadband Connection
Broadband refers to high-speed internet access that is faster than traditional dial-up access. It is provided through either cable or
telephone composition. It does not require any telephone connection that’s why here we can use telephone and internet
connection simultaneously. In this connection, more than one person can access the internet connection simultaneously.
It is a wide bandwidth data transmission that transports several signals and traffic types. In this connection, the medium used
is coaxial cable, optical fiber cable, radio, or twisted pair cable.
Broadband-Connection
3. DSL (Digital Subscriber Line)
DSL stands for Digital Subscriber Line. It provides an internet connection through the telephone line(network). DSL is a form of
broadband communication that is always on, there is no need to dial a phone number to connect. DSL connection uses a router
to transport data and the speed of this connection range between 128k to 8Mbps depending on the service offered. A DSL
connection can translate data at 5 million bytes per second, or 5mbps.
DSL service can be delivered simultaneously with wired telephone service on the same telephone line due to high-frequency
bands for data.

DSL
4. Cable
It is a form of broadband access cable modem that can provide extremely fast access to the internet. The speed of this
connection varies which can be different for uploading data transmission or downloading.
It uses a cable modem to provide an internet connection and operates over cable TV lines. The speed of cable connection ranges
from 512k to 20Mbps.h

Cable
5. Satellite Connection
This type of connection is provided mainly in rural areas where a broadband connection is not yet offered. It accesses the
internet via a satellite that is in Earth’s orbit.
The signal travels from a long distance that is from earth to satellite and back again which provides a delayed connection.
Satellite connection speeds range from 512k to 2.0Mbps.
Satellite Connection
6. Wireless Connection
As the name suggests wireless connection does not use telephone lines or cables to connect to the internet. The wireless
connection uses a radio frequency band to connect to the internet. It is also an always-on connection and this connection can be
accessed from anywhere and speed may vary for different locations. It ranges from 5Mbps to 20Mbps.

Wireless Connection
7. Cellular
Cellular technology provides wireless Internet access through cell phones. Speed may vary depending on the service provider.
The most common are 3G and 4G which means from 3rd generation and 4th generation respectively. The speed of the 3G
cellular network is around 2.0Mbps and the 4G cellular network is around 21Mbps the goal of the 4G network is to achieve peak
mobile speeds of 100Mbps but the current speed of the 4G network is about 21Mbps.
Cellular
8. ISDN (Integrated Service Digital Network)
ISDN stands for Integrated Service Digital Network and it is a circuit-switched telephone network system, but it also provides
access to packet-switched networks that transmits both voice and data over a digital line. It provides a packet-switched
connection for data in increments of 64 kilobit/s.
ISDN connection provides better speeds and higher quality than traditional connections. It provided a maximum of 128kbit/s
bandwidth in both upstream and downstream directions.

ISDN
Components Required For Internet Connecton
 Modem: A device that modulates and demodulates signals for encoding and decoding digital data transmitted over a
telephone line or cable system.
 Router: A device that routes data from a local network to the internet and vice versa, often includes Wi-Fi capabilities.
 ISP (Internet Service Provider): The company that provides internet access to customers.
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