CSE courses and subjects

salam guys it is informed to all the students of computer system engineering that now they can access their related subject Books and also a lot of courses books like CCNA CCNP Web designing development and a lot more just have a little overview Click here

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working of dns

How DNS works ?

The Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most prominently, it translates domain names, which can be easily memorized by humans, to the numerical IP addresses needed for the purpose of computer services and devices worldwide. The Domain Name System is an essential component of the functionality of most Internet services because it is the Internet's primary directory service

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 this is the begning of the cource mobile and wirless system




LectureOutline Lecture Outline
TheWirelessVision The Wireless Vision
Technical Challenges
h il ? Why Wireless ? 
Types of Wireless Communications
Current Wireless Systems
SpectrumRegulation&Standards Spectrum Regulation & Standards
Main Point
WirelessVision Wireless Vision
Multimedia Wireless Communications Any Time and Anywhere
Applications:
Wireless Information Devices
Wireless LANs
WirelessVideo/M sic Wireless Video/Music
Multimedia Home Networks
Smart Homes/Appliances
Remote Learning/Medicine
Sensorand AdHoc Networks Sensor and Ad-Hoc Networks
Autonomous Vehicles/Robots

TechnicalChallenges Technical Challenges
 Hardware
Multimode operation
Multilayer Design
Multimode operation
Small, lightweight, low power
High‐frequency components
 Communication Link Design
 b ll ffi i ii hi Fast, robust, spectrally efficient communication techniques
Mitigation of wireless channel impairments
 Multiple Access and Resource Allocation
Efficientschemesthatmaximizesystemcapacity Efficient schemes that maximize system capacity
Dynamic resource allocation and efficient spectral reuse
 Networking.
Routing and mobility management for mobile users out gad ob ty aage eto ob euse s
Network reliability, flexibility, and scalability
Deliver QoS to applications/application adaptation
Performance gap with wireline system

Multimediarequirements Multimedia requirements 
Voice Data Video
Delay  < 100 ms ‐ < 100 ms 
Packet loss < 1% < 1%
BER 10
–3
10
–6
10
–6
BER 10 10 10
Data rate  8‐32 Kbps 1‐100 Mbps 1‐20 Mbps
Traffic  Continuous Bursty Continuous 

Wireless(Why?) Wireless (Why?) 
Freedomofwires Freedom of wires
No cost of installing wires or rewiring 
No bunches of wires running here and there g
“auto‐magical” instantaneous communication 
without physical connection setup, e.g.,  
Bluetooth, Wi‐Fi
Global coverage
Communication can reach where wiring is not 
feasible or costly, e.g., rural areas, old buildings, 
battlefieldsvehicles outerspaceetc

Wireless(Why?) Wireless (Why?)
Stayconnected Stay connected
Roaming allows to stay connected anywhere 
anytime
rapidly growing market attests to public need for 
mobilityandun‐interuppted access mobility and uninteruppted access  
Feasibility
Servicesreachyouwhereyougo(Mobility) Services reach you where you go  (Mobility) 
Connect to multiple devices simultaneously (no 
physicalconnectionrequired)

WirelessvsMobile Wireless vsMobile 
Wirelessdonotnecessarilymeanmobile Wireless do not necessarily mean mobile 
il b Wireless systems may be 
Fixed (e.g., metropolitan networks)
Portable (e.g., interaction between TV and VCR)
Mobile (e.g., mobile phones) 

TypesofWirelessCommunication Types of Wireless Communication
Mobile 
Cellular phones (GSM/cdma2000) 
Portable Portable 
IEEE 802.11
Fixed 
IEEE 802.16 (Wireless MAN) –first tested in south 
korea! 

Types of Wireless communication 

 Radio Transmission 
Easily generated, travel long distance, easily penetrate 
buildings. 
Problems: 
•Frequency dependent 
•Relatively low bandwidth for data communication 
•Strict spectrum regulations 
 Microwave Transmission 
Widely used for long distance communications 
GivesahighS/Nratio relativelyinexpensive Gives a high S/N ratio, relatively inexpensive 
Problems:
•Do not pass through buildings (Shadowing) 
•Weatherandfrequencydependent


Types of Wireless communication 
Infrared and millimeter wave
Widely used for short range communications 
Unable to pass through solid objects 
Udf id il LAN tf td Used for indoor wireless LANs, not for outdoors 
Light‐wave transmission  
UnguidedopticalsignalsuchasLaser Unguided optical signal such as Laser
Connect two LANs via optical communications 
Unidirectional, easy to install, do not require license
Problems: 
•Unable to pass through rain or thick fog
•Laser beam can easily be diverted by turbulent air 


 Current Wireless Systems
 Point‐to‐PointWirelessLinks PointtoPoint Wireless Links
 Cellular Systems
 Wi l LAN  Wireless LANs
 Wireless WANs
 Ad‐Hoc Wireless Networks
 Satellite Systems
 HomeRF and Bluetooth

CellularSystem Cellular System
 A large  geographical region  g ggp g
is segmented into smaller 
“cells”. 
Transmitpowerlimitation Transmit power limitation 
Facilitates frequency spectrum 
re‐use
 Cellular network design 
issues 
Inter‐cell synchronization 
Handoff mechanism 
Frequencyplanning

CellularWirelessSystem Cellular Wireless System
Frequencyreuse Frequency reuse 
Frequency re‐use = 1
‐Higher spectral efficiency 
Frequency re‐use = 7
‐lower interference for cell‐edge users  
 Cellular Wireless System 
Frequencyreuse=3 Frequency reuse = 3 

CellularWirelessEvolution Cellular Wireless Evolution
4G
System beyond IMT‐2000 (IMT‐Advanced)
LTE/LTE‐Advanced, WiMax (802.16m)
3G
IMT 2000 Global standard | Wideband CDMA (‘00s)
UMTS/WCDMA/HSPA, CDMA2000, TD‐CDMA
2G
Digital modulation & roaming | TDMA & CDMA (‘90s)
GSM, IS‐95, PDC
1G Analog speech | FDMA (‘80s)
AMPS

Wireless Local Area Networks 
WLANconnectlocal computers WLAN connect local computers
100 m range, confined places 
Breaksdatainto packets Breaks data into packets
Channel access is shared (random access) 
 backbone internet provide best effort service
Problems:
Poor performance in some cases (e.g., video)
Limitedmobility

Satellite Systems
Coversverylarge areas Covers very large areas
Very useful in sparsely populated areas: rural 
areasseas mountains areas, seas, mountains  
 Different orbit heights
GEOs(39000km) LEOs(20000km) GEOs (39000 km), LEOs (20000 km) 
Optimized for one way transmission
Expensive base stations (satellite
Limitedquality/voicetransmission Limited quality/voice transmission 
Typical applications 
Weathersatellites Weather satellites
TV and radio satellites
Militarysatellites Military satellites
Telecommunication applications 
Globaltelephoneconnections Global telephone connections 
Backbone for Global Network
GPS

 Paging Systems 
Broadcoverageforshortmessages Broad coverage for short messages
Message broadcast from all BSs
Si l il Simple terminals
Low cost, low complexity, very low power devices 
Optimized for one way transmission
Call back, very hard , y
Replaced by Cellular! 

 Personal Area Networks 

 Bluetooth 
Cable replacement RF technology
Short range (10m, extendable to 100m)
Operate at around 2.45 GHz (2.40 to 2.45 GHz) crowded!  p
Divided into 79 channels
1 data (700 kbps) and three voice channels
1 Mbps data rate shared between 7 devices p
TDD duplex schemes 
Polling based multiple access
Widelysupported Widely supported 
FHSS is used to minimize interference & fading 
The modulation technique is Gaussian frequency‐shift keying
Themaximumtransmittedpoweris0dBm(1mW)

merging Wireless Networks 

AdhocWirelessNetworks Ad hoc Wireless Networks
Sensor Networks
iib dClS Distributed Control Systems
Ultra Wide Band (UWB) Systems 
 Ad‐Hoc Networks
 Peertopeercommunications Peer to peer communications 
 No backbone infrastructure
 Routing can be multi‐hop
 Topology is dynamic 
 Fully connected with different SINRs

 Sensor Networks 

Nodes powered by self rechargable batteries
Data flows to centralized locations 
Low per node rates but upto 1000 nodes
D hi hl ldi i d Data highly correlated in time and space
Nodes can cooperate in transmission, reception,  
compression andsignalprocessing

 Ultra Wide Band (UWB) Systems 
UltraWideBand(UWB)Systemsisan Ultra Wide Band (UWB) Systems is an 
emerging wireless technology that can 
transmitdataataround100Mbps(upto1000 transmit data at around 100 Mbps (upto1000 
Mbps) 
UWBtransmitsultralow powerradiosignals UWB transmits ultra low power radio signals 
with very narrow pulses (nanosecond) 
B fi l i i i Because of its low power requirements, it is 
very difficult to detect (hence secure)  

SpectrumRegulation Spectrum Regulation
 Spectral Allocation in US controlled by FCC  p y
(commercial) or OSM (defense)
 FCCauctionsspectralblocksforsetapplications FCC auctions spectral blocks for set applications.
 Some spectrum set aside for universal use
 Worldwide spectrum controlled by ITU‐R

Standards
 Interacting systems require standardization
 Companies want their systems adopted as standard
Alternativelytryforde‐factostandards Alternatively try for defacto standards
 Standards determined by TIA/CTIA in US
IEEE tddft dtd IEEE standards often adopted
 Worldwide standards determined by ITU‐T
In Europe, ETSI is equivalent of IEEE for standards 
development.
Main Points
 The wireless vision encompasses many exciting systems 
d li ti ltf titi and applications –plenty of opportunities
 Technical challenges transcend across all layers of the 
systemdesign–optionsforfurtherresearch system design –options for further research
 Wireless systems today have limited performance and 
interoperability –thatmotivatesustoworkon interoperability  that motivates us to work on 
improving system performance: further research
 Standardsandspectralallocationheavilyimpact the Standards and spectral allocation heavily impact the 
evolution of wireless technology –Integration of various 
types of wireless systems

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final year projects

the final year project in robotics regarding to computer system engineering

online hotel reservation using andriod application

using c# programming

Figure: The V2DIP2-32 module on a breadboard, with outputs controlled by simple C++ or C# programs running in Windows 7/Vista, without the need to install ...

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working of ssl

HOW SSL WORKS? (view)

SSL (Secure Socket Layer) is a cryptographic protocol encrypted with 128 or 256 bit key that provides secure connection between a browser and a server (where your web site is hosted). How SSL works – any data sent between the browser and your website is encrypted before sending and then decrypted after being received with this 128 or 256 bit key issued especially for you. A SSL certificate is issued by a trusted authority like RapidSSL or GeoTrust and installed specifically for a single hostname of your web site (e.g. https://secure.domain.com) where you need encrypted connection. In that way all the data transmitted between the hostname where your client is submitting personal details and the server (where you web site resides) is encrypted and signed as secured by this trusted SSL issuer. The presence of a SSL (https:// valid connection) on your web site increases the confidence of your sites’ visitors during the purchasing process.

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difference between static and dynamic and default routing

Difference between Static, Dynamic and Default Routing

Static Routing:

A static routing occurs when you manually add routes in each Router’s Routing table, Routing table should create, maintain, and update by a network administrator, manually. A static route to every network must be configured on every router for full connectivity. This provides a granular level of control over routing, but quickly becomes impractical on large networks. Routers will not share static routes with each other, thus reducing CPU/RAM overhead and saving bandwidth. However, static routing is not fault-tolerant, as any change to the routing infrastructure (such as a link going down, or a new network added) requires manual intervention. Routers operating in a purely static environment cannot seamlessly choose a better Route if a link becomes unavailable. Static routes have an Administrative Distance (AD) of 1, and thus are always preferred over dynamic routes, unless the default AD is changed. A static route with an adjusted AD is called a floating static route.
Command Syntax for Static Routing on Cisco Router

The syntax for the global configuration command used to enter a static route is:

ip route {destination prefix} {destination prefix mask} {Exit interface OR Next hop IP address} {Administrative Distance} {Permanent}

The following briefly outlines the advantages and disadvantages of static routing:

Advantages of Static Routing:

1. Minimal CPU/Memory overhead

2. There is no bandwidth update between Routers, which means you will save bandwidth on WAN links.

3. It adds security because the administrator can choose Routing access to certain networks only.
Disadvantages of Static Routing:

1. If any Infrastructure changes must be manually adjust the configuration in complete network.

2. No “dynamic” fault tolerance if a link goes down

3. Administrator must understand the complete internetwork and how each Router connected to configure properly.

4. Impractical on large network

Dynamic Routing:

A Dynamic Routing is when protocols are used to find networks and update Routing tables on Routers. A dynamic routing table is created, maintained, and updated by a routing protocol running on the router. Examples of routing protocols include RIP (Routing Information Protocol), EIGRP (Enhanced Interior Gateway Routing Protocol), and OSPF (Open Shortest Path First). Routers do share dynamic routing information with each other, which increases CPU, RAM, and bandwidth usage. However, routing protocols are capable of dynamically choosing a different (or better) path when there is a change to the routing infrastructure.
Difference between Routing Protocols and Routed Protocols

Do not confuse routing protocols with routed protocols:

A routed protocol is a Layer 3 protocol that applies logical addresses to devices and routes data between networks (such as IP)

A routing protocol dynamically builds the network, topology, and next hop information in routing tables (such as RIP, EIGRP, etc.)

The following briefly outlines the advantages and disadvantages of dynamic routing:

Advantages of Dynamic Routing:

1. Simpler to configure on larger networks

2. Will dynamically choose a different (or better) route if a link goes down

3. Ability to load balance between multiple links
Disadvantages of Dynamic Routing:

1. Updates are shared between routers, thus consuming bandwidth

2. Routing protocols put additional load on router CPU/RAM

3. The choice of the “best route” is in the hands of the routing protocol, and not the network administrator.

Default Routing:

A default routing is used only when one exit path from the Router. Default Routing can configure like a static route with the ip route command, but use 0.0.0.0 0.0.0.0 for the IP network and subnet mask followed by the next hop router’s IP address or Exit interface of the local Router. Have to also use the ip classless command since there aren’t any routes in the routing table. ip classless is enabled by default in IOS version 12.
Command Syntax for Default Routing on Cisco Router

Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.1.2

Router(config)# ip classless

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