ABOUT NETWORKING

WHAT IS NETWORKING ?

Networking is a connection of nodes via from media in which the nodes have the capability to send and receive data that is called networking.

NETWORK TOPOLOGY:-

WHAT IS TOPOLOGY ?

Topology is the method in which networks are physically connected With each other i.e called topology.

DIFFERENT TYPES OF TOPOLOGY:-

v Mesh topology

v Star topology

v Bus topology

v Ring topology

MESS TOPOLOGY:-

Ø It is a fully connected topology.

Ø In mess topology, every device has an dedicated point to point link to every other device.(point-to-point means connect two device directly Together.

Ø In a mesh topology each device/PC is connected to every other device/PC in the network by its own cable, which means vast amounts of cables for any sizeable network.

Ø The Mesh topology having separate cables for each connection if any one cable to break ,it does not incapacitate the entire system.

Ø Every time you add a devices to a mesh network you have to run cables to each of the other devices.

Ø The amount of cables you will need for a mesh network can be calculated by: CN = (D * (D-1)) / 2 (where CN is Cables Needed, and D is the amount of devices on the network)

Ø If your network was going to have 4 devices then you would need 4 * 3 / 2 = 6 cables

Ø The problems come with a large network, imagine a 40 device network: 40 * 39 / 2 = 780 cables

Ø When you need to add a single device to a Mesh network the job can be very complex, for example if you had a network of 15 devices, to add one device would mean adding 15 cables to the network.

ADVANTAGES OF MESH TOPOLOGY:-

Ø Mess topology is more reliable.

Ø It is more flexible.

Ø It is very expensive.

Ø It is more secured and privacy is well maintained.(when every Message travels along a dedicated line, only the intended recipient Sees this message).

DISADVANTAGES OF MESH TOPOLOGY:-

Ø It is costlier.

Ø The amount of cabling and the no. of I/O ports required, that’s why installation and reconnection are difficult.(because every device connected to other device).

STAR TOPOLOGY:-

Ø In a Star topology each devices has a dedicated point-to-point link only to

central controller such as a Hub or Switch or router.

Ø The devices are not directly linked to one another. Here data travels through

the hub to all other devices. i.e cotroller acts as an exchange.

Ø If one device wants to send data to another device, that time first device

sends the data to the controller, which then relays the data to the other

connected device.

Hub are two types-

n Active hub

n Simple hub

Active hub :- it release the data and refresh the data.

Simple hub:- it only release the data.

Ø In a Star topology, if one device/cable failure, it will not affect the another network .

Ø If centralising device or server failure that time all devices fails.

A star network requires more cable.

Ø Physically adding new devices to a Star network is very simple compared to any of the other topologies.

Example-In our college computer lab is use in star topology.

ADVANTAGES OF STAR TOPOLOGY:-

Ø It is much easier to modify or add new computers to a star network without disturbing the rest of the network.

Ø It is reliable.

Ø It is flexibility.

Ø The failure of a single device or cable does not bring down the entire network.

Ø It is easy to install and reconfigure (that is each device needs only one link and one i/o to connect it to any no. of others).

DISADVENTAGES OF STAR TOPOLOGY:-

Ø If the central hub fails, the whole network fails to operate .

Ø It is costlier .

Ø It is less expensive than a mesh topology.

USES OF STAR TOPOLOGY:-

Ø It is used in local-area-network(LAN).

Ø High speed LAN often use a star topology with a central hub.

BUS TOPOLOGY:-

Ø Bus topology is a multipoint structure.

Ø Bus consists of a single linear cable called a trunk/backbone link all the devices in a network.

Ø A Bus topology can be both Physical and Logical .

Ø Network nodes are connected to the bus cable by drop line and tapes.

1. Drop lines – it is connection between a node and the main cable.

2. Taps – A tape is a connector either splices into the main cable or punctures

the sheathing of a cable to create a contact with the metallic core.

Terminators should be applied to both ends of the longest path.

Ø Data is sent to all computers on the trunk. Each computer examines every packet on the wire to determine who the packet is for and accepts only messages addressed to them.

Ø Bus is a passive topology which means only

One computer at a time can send a message.

Ø The problems can come when adding a new device to an existing Bus topology network.

ADVANTAGES OF BUS TOPOLOGY:-

Ø It is easy to use and understand.

Ø Less no. of cable required.

Ø It is inexpensive simple network.

Ø It is easy to installation.

DISADVANTAGES OF BUS TOPOLOGY:-

Ø It is very difficult to reconnection and fault isolation.

Ø It can be difficult to add new device.

Ø It require modification or replacement of the backbone when adding new device.

Ø If cable break or loose connector or fails, the whole network not working.

USES:-

Ø Bus topology was one of the first topology Used in the design of early local area

network(LAN).

Ø Ethernet LAN can be use a bus topology.

RING TOPOLOGY:-

Ø Computers are connected on a single circle of cable.

Ø In ring topology each device has an dedicated point-to-point connection only the two devices on the either side of it.

Ø The signal is passed along the ring in one direction from device to device, until it reachers the destination.

Ø In a ring, a signal is circulating at all times.

Ø Here signal is circulating by anticlockwise.

Ø Each device in the ring incorporates a repeater.

Ø When a device receives receives a signal intended for another devices. its repeater regenerates the Bits and passes them along.

Ø If one device does not receive a signal within a specified period ,it can issue an alarm. The alarm alerts the network operator to the problem and its location.

Ø If one device/cable fails then the whole network goes down.

Ø Adding a new device to an existing physical Ring network can be complicated.

Arbitrary mechanism means token.

Ø Here token ring or FDDI(fiber distributed data interface) used.

Ø Here no termination is required because it is a ring. there is no end of its ring.

Ø Token passing is used in token ring networks.

Ø The token is passed from one computer to the next, only the computer with the token can transmit.

Ø This topology is faster.

Ø This type of topology can be found in peer-to-peer network.

ADVANTAGES OF RING TOPOLOGY:-

Ø It is relatively easy to install and reconfigure.

Ø It is more reliable.

Ø Security is less.

Ø Cost is less.

Ø It is more reliable.

DISADVANTAGES OF RING TOPOLOGY:-

Ø It is unidirectional.

Ø If failure of one computer on the ring can affect the whole network.

Ø It is difficult to troubleshoot a ring network

Ø Adding and removing devices disrupts the network.

Distributed Medium Access Control for Next Generation

Distributed Medium Access Control for Next Generation

CDMA Wireless Networks

Generic Distributed Network Model

We focus on a generic network model where a number of wireless mobile nodes are organized in a flat fashion, communicating with each other via one-hop or multiple-hop connections without any central control. Connections to outside correspondence nodes are supported through a gateway (e.g., in the wireless backbone) or an access point (e.g.,in ad hoc networks or WPAN).

In the past decade, code-division multiple access (CDMA) technology has been developed and deployed popularly with great success in the second-generation (2G) cellular systems (e.g., IS-95). It also been selected as the major multiple access technology for the third-generation (3G) systems. CDMA has many promising merits such as universal frequency reuse, soft handoff, and high spectrum efficiency.

Desired Features of Distributed MAC:

AMAC scheme is to coordinate the mobile nodes access to the shared medium such that efficiency can be achieved. Although MAC schemes in traditional cellular networks and WLAN have been extensively studied in the literature, more efforts are still needed for distributed MAC supporting multimedia traffic in the network without a central controller.

In a centralized network such as the cellular network, the central controller makes decisions on when and how the mobile nodes should access the medium. However, in a network without a central controller, MAC is carried out in a collectively coordinated manner, where a mobile node determines its access behavior according to its local observation.

Features Of Distributed MAC:

Quality of service (QOS) support

Service differentiation

Low overhead

Bandwidth Efficiency

Distributed Code Assignment

Generally, before a transmission, the transmitter and receiver need to know the code (sequence) to be used. In cellular networks, the BS collects information from all the nodes, and informs them what codes are used in upcoming transmissions. However, as our network model dose not have central authority, distributed code assignment is desired.

There are three kinds of codes that can be used

v Common code

v Receiver based code

v Transmitter based code

Distributed Interference Control

By proper code assignment to the CDMA transmissions, collisions among them can be avoided. However the interference among simultaneous transmissions with unique codes should also be managed Generally, power control can be applied to manage the interference levels in the network, targeting at guaranteed transmission accuracy of each link. Power control can be executed in two manners: global or incremental.

A global power control approach re-assigns the power levels of all the links in the network at any time when there is a change in link activities, e.g., when a new link is admitted or an existing link is completed.

In the incremental power control, it is important for a candidate transmitter to know the interference tolerance level of active links.

The Proposed Distributed MAC

In our network model, the MAC is to coordinate the one-hop transmission from a transmitter to one of its neighbors. Each node has its own transmitting code and receiving code, the information of which is available to its neighbors through some information exchanges in the routing protocol.

I am discussed the limitations of existing distributed CDMA-based MAC schemes when applied to our generic network model with distributed control. By letting active receivers estimate potential increase in the interference level, our proposed MAC scheme can achieve bit-level QoS, low overhead, accurate channel and interference estimation, and high bandwidth efficiency.

e-Wallet THE FUTURE OF CARDS

e-Wallet THE FUTURE OF CARDS

Abstract:

Using the basic concepts of Embedded Systems, an idea for changing the future of Cards (Banking, Petro, Health, Televoice, etc.) is proposed in this paper. Requirement of a special card reader, limited lifetime, acceptance being the main disadvantages of today’s traditional cards, led to the design of e-Wallet. The main objective of e-Wallet is to make paperless money transaction easier. The main idea behind this paper is to bring in a cheaper, more versatile and much more easily usable kind of a card. Using this e-Wallet the transaction procedure can be as simple as: the customer goes to the point of sale (POS), does the purchasing and when it comes to the payment, the customer submits his e-Wallet to vender who connects it to his terminal (PC).The vender displays the billing information to the customer who finalizes it. The amount in the e-Wallet is updated accordingly. Later at periodic intervals, the vender intimates the bank (in case of credit cards) which transfers the amount from the customer’(s) account to his. The advantages of e-Wallet are its ease of use (doesn’t require a separate card reader), ease of maintenance, flexibility, safety, being the primary ones. The designing of the card is similar to any other embedded card. The designing cost of the card (e-Wallet) being as low as the price of a pizza. There are ample enhancements to this application from credit cards to televoice cards. Unlike traditional cards which are application oriented, all the applications’ software can be embedded into this e-Wallet which provides multi-functionality.

Introduction:

With the advent of computers many technologies are taking this world by a surprise. These include Embedded Systems (ES), Artificial Intelligence (AI), Neural Networks (NN), Fuzzy Logic, Bluetooth and many more are upcoming. This paper deals with Embedded Systems in a new perspective.

In easy terms, Embedded Systems can be viewed as a combination of hardware and software components, in which the software is implanted into the hardware to do the specific job. These ES were implemented in various fields from Battery chargers to Aviation Systems besides Cell phones (GSM, GPRS, CDMA, etc.). These ES are being developed in ‘leaps and bounds’. The never-ending efforts of many scientists in the field of ES led to the evolution of Smart Technology (ST).

Using the basic concept of ES, an idea for changing the future of Cards (Banking, Petro, Health etc.) is proposed in this paper. To interpret this idea, it is first needed to know the pros & cons of today’s ‘traditional’ cards. Consider the example of banking:

The magnetic stripe cards used for transactions are as simple as visiting cards, with a magnetic tape to hold the user information. The basic advantages of these cards are:

Ease of mobility Ease of use

Coming to the disadvantages of these cards, few are listed here under:

· Easy Duplication

· Requires a special card reader

· Networking problems

· No memory to hold the current balance

· Limited lifetime

· No particular user authentication

· Unsecured remote transaction

· Limited acceptance

· Vulnerable to moisture, heat, dirt etc.

and the list goes on……

Keeping these pros & cons in view, the Smart Technology is introduced to develop a new class of cards. This stream of Smart Technology can be termed as Smart Card Technology (SCT). This smart card has a microprocessor or memory chip embedded in it that, when coupled with a reader, has the processing powerto serve many different applications. Such cards can be referred to as e-Wallet (electronic Wallet).

e-Waet:

The main objective of e-Wallet is to make paperless money transaction easier. The electronic wallet (e-Wallet) is just like a leather wallet as it does the same, in terms of e-cash. In today’s life where monetary value and security both, go hand in hand, it is difficult to satisfy customers using the routine cards. The main idea behind this paper is to bring in a cheaper, more versatile and much more easily usable kind of a card.

Salient features of e-Wallet are:

ü More than 40 years of data retention

ü Firewall encrypted security logic

ü Compatible with many supporting hardware.

ü No separate card reader is required to access our card.

ü Polarity reversal indicator is pre-built in our card.

ü Reusability of our card is unlimited.

ü Multiple card features are incorporated in the same card.

ü External complexities are less.

Transaction Procedure:

The e-Wallet cardholder goes to a point of sale (POS) location where the e-Wallet is accepted. Having chosen the goods he wishes to buy, he goes to the cash desk. Here, the merchant calculates the total value and enters it on the payment terminal using a keypad. The terminal then displays the amount on a small screen facing the cardholder, who confirms the amount by pressing an "OK" button. In less than a second, the value is transferred from the e-Wallet to the terminal, and the value remaining in the e-Wallet is adjusted. This is an off-line transaction. A message is displayed to both the cardholder and the merchant saying that the payment has been accepted.

Periodically, the merchant connects the terminal to his bank to do a collection that is to transfer the value collected in the terminal to his bank account. This is an on-line transaction. The terminal sends a message for each transaction to the e-Wallet host system, identifying the card number and issuer and the amount. The host system debits the float account of the issuer and credits the merchant's account. This typically takes a few seconds per transaction.

Merchants can program their terminals to automatically do collections each day, week or month, or when a specified value of transactions is reached. If merchants have a number of terminals (e.g. a vending machine operator, or a large supermarket) then they can use the "shuttle collection" system, where terminals download their data onto a special collection card, which in turn then downloads it into a central terminal, which is then used to perform an on-line collection.

Card Designing:

Application Specific Integrated Circuit:

Most of the home friendly electronic oriented products works on custom specified integrated circuit chips like electric oven, cellular phones, washing machines etc. Following this global trend we are using FIELD PROGRAMABLE GATE ARRAY (FPGA) belonging to the family of APPLICATION SPECIFIC INTEGRATED CIRCUIT.

Field Programmable Gate Array (FPGA):

FPGA is widely used in all consumer electronic devices because of its low cost and better reliability. It can be easily programmed by the end user and used in any applications. FPGA can be broadly classified into two types

1. Custom designed IC

2.General purpose IC

Custom design FPGA’s are developed by user specification from wafer level and final output is obtained. It is only suitable for mass production systems with unique programming .Another widely used one is general purpose FPGA’s which were supplied by the vendor in IC form where the user has to program to his requirements with the help of EDA tools (electronic device automation).

Internal Architecture of FPGA:

The internal blocks of FPGA IC are:

Embedded Microcontroller: The embedded microcontroller used here is ATMEL AT40K. It has the overall system control and it interprets the encryption algorithm. A dedicated logic is used for security measures such as personal identification number (pin) authentication or challenge response. The voltage level is: VCC= 1.8 +/- 0.15V.

Crypto Coprocessor: This is a custom designed unit (Modular Exponential unit) to implement encryption algorithm. Inside, it has a ROM to store the password used. It runs independent of the microcontroller unit and it minimizes the delay in data encryption and decryption. By using a crypto-coprocessor, the password in encrypted and stored and it would be almost impossible for a hacker to crack the password.

Random Word Generator: The random word generator unit generates a random word which replaces the password (correct password) in the buffers and other terminals with a random word after the transaction is over. Hence it is almost impossible to replicate the behavior of the ASIC and thereby obtain the encryption key or algorithm used.

On Chip Security Power Management: This unit protects the card (ASIC) against over voltage or under voltage and over frequency or under frequency of the clock signals given for operation.

Access Control: Access control unit protects the on chip memory. It provides address and data bus scrambling and detects any non-standard attempt to acquire memory access.

Flash ROM / ROM: Flash ROM stores the instruction set for the microcontroller unit, the necessary monitor routine programs and the application code. Here the flash ROM is used because there are 32 available instructions sets for different applications. But only one instruction set is used. If another instruction set is used the card can be used for only the specific application.

EEPROM: EEPROM is used to store the processed data i.e. the balance amount in the card. This part is of commercial importance as it holds the monetary information of the card. Also the EEPROM sends the data to be read for establishing transaction

RAM: It provides the workspace for both the microcontroller unit and the crypto co-processor. It’s where the actual comparison of the stored password (original password) and the given password for transaction to take place. Only if the given password is the actual password, the access is given to view the details of the card, deposition, withdrawal are allowed.

Serial Interface: It has six valid pins CS-chip select, CLK-external clock, DI-data input, D0-data input, VOC-voltage input, GND-ground. Actually a parallel printer port is used for interface of the card with PC. But only the six required pins of the printer ports are activated. Thus the advantages of parallel and serial communication are utilized. There is no need for a separate USB.

RF Interface: This unit provides establishment of transaction using Blue tooth technology, which is our future enhancement.

Internal 16 Bit Address/Data Bus:

This provides communication between different units inside ASIC chip. This ASIC chip is built satisfying ISO 7816 standards.

Operation:

Once the card is given the power supply all the units are activated.

The password is sought and the password is sent. The first bit is chip select then the start bit, two opcode bits, 6-address bits and 16 data bits.

The dedicated embedded microcontroller looks after this process.

Then the given password is sent to the RAM work space.

The password (original password) after decryption by the crypto processor is sent to the RAM.

Here the passwords are compared by the microcontroller. Only if the both the passwords are correct, the access control unit brings the flash ROM, EEPROM units of low impedance state.

Otherwise the units are kept in high impedance state.

The on-chip security power management unit provides the correct voltage and correct frequency (CLK signal) for functioning of the ASIC.

If the password is correct, then the microcontroller fetches the instructions from the instruction set in the FLASH ROM.

The balance amount can be fetched form the EEPROM, through the D0 pin of the serial interface.

After the transaction is over the balance amount is stored in the EEPROM through D1 pin of the serial interface.

Once the transaction is over, the random word generator generates a random word and sends it to the terminal ends and other buffers where the original password is present.

This protects the original password from being hacked by hackers.

Thus the ASIC is designed for effective transaction with proper security to the customers.

Features of e–Wallet:

• Refillable
• Infinite lifetime
• Current balance can be stored and read
• User authentication is provided
• Universal access
• Maximum possible cash
• Cannot be duplicated

Advantages of e-Wallet:

Ease of use:

• Withdraw or deposit value by telephone
• Pay the exact amount, no fiddling for change
• No signature required
• Immediate payment

In the future, access points may include mobile phones

Accessibility and convenience:

• Cash machines and telephones give more access points to funds in bank account
• Available 24 hours / 365 days
• Cash machines and telephones cannot run out of electronic cash

Flexibility:

• Transfer value by telephone
• Pay person to person
• For low or high values
• Multi-currency capability
• No age limit, so suitable for all the family

Safety and control:

• Spend only what you have
• Read your balance
• Load value at home
• Lock your card or wallet
• Keep track of what you have spent and where
• Customer is traceable if a lost card is found

With all the above mentioned features it is definite that the future of cards is definitely e-Wallet’s. Besides credit cards, this e-Wallet can also be extended into the following fields, namely:

ü Sim – card

ü Petro – card

ü Credit – card

ü Health – card

ü Intelligent web – surfing card

ü Insurance – card

ü Access – card

ü ATM

ü Televoice card

These are only the few to mention. Due to its ease of adaptability to its environment, this e-Wallet would certainly change the way people transact (monetary transactions).