CLIENT SERVER

Request

Response

1. List the functions of the application layer.

Ans. The functions of the application layer are:

a)It is responsible for facilitating interaction between many applications like WWW, EMAIL, FTP, and DNS, and servers like mail server and FTP server.b)It interfaces directly to and performs common application services for the application processes; it also issues requests to the presentation layer.

2. What is DNS? .DNS is a name resolution service that resolves host names to the IP addresses. DNS has a hierarchical and distributed database that contains mappings of host names with the corresponding IP addresses.

3. Explain the working of DNS with an example.

Ans.DNS is a name resolution service that resolves host names to IP addresses. A DNS server resolves host names to IP addresses for DNS queries sent by the DNS clients. These queries can be in the form of a name resolution query or a resource record. The resolver sends a User Datagram Protocol (UDP) packet to the local DNS server. The DNS server searches its table and returns the IP address, which matches the domain name. DNS has a hierarchical and distributed database that contains mappings of host names with the corresponding IP addresses.

Resource records are stored in a specific portion of the DNS database called the DNS zone. A DNS zone contains resource records along with the owner names.

For example, an application program calls a procedure with its domain name as parameter. The procedure sends an UDP packet to the local DNS server. The DNS server searches its table and returns the IP address which matches the Domain name. The program can now establish a TCP connection or send UDP packets.

4. What is an iterative resolution?

Ans. Iterative resolution refers to the name resolution technique in which a server sends back the information to a client or sends the name of the server that has the information. The client then iterates by sending a request to this referred server. This server may return the information itself or send the name of another server. This process continues till the time the client receives the required information.

5. Write a brief note on SMTP.

Ans. SMTP is a protocol that transfers mail reliably and efficiently. SMTP is independent of a particular transmission subsystem and needs only a reliable ordered data stream channel. An important feature of SMTP is its capability to relay mail across transport service environments.

6. Discuss the working of POP3 in an e-mail system. What are its limitations?

Ans.When users check their e-mail, the e-mail client connects to the POP3 server by using port 110. The POP3 server requires an account name and a password.The POP3 server issues a series of commands to bring copies of user e-mail messages to user’s local machine. Generally, it will then delete the messages from the server (unless the user chooses the not to option in the e-mail client).

Once the connection has been established, the POP3 protocol goes through three stages in sequence:

a)Authorization b) Transactions c) Update

The authorization state deals with the user log in. The transaction state deals with the user collecting e-mail messages and marking them for deletion from the mailbox. The update state causes the e-mail messages to deleted. During the authorization state, at times, when the server is set for three passwords trials, if you give the wrong password thrice, your mail box will get locked.

7. POP3 servers have certain limitations such as:

a)There is no folder structure for sorting e-mail messages that are saved on the POP3 server. The server has only one folder for incoming mails, which is the inbox. b)No rules can be set at the POP3 server. All rules are set at the client end only. If a user’s machine crashes, e-mail messages can only be recovered if a copy of them is left on the server. c)To check e-mail, users have to download them first and only then they can view their mails on the e-mail client software. User cannot see mails first and then download the required mails. If there are spam e-mail messages in the inbox that can be dangerous for the computer, these will also get downloaded and the user has to delete them.

Reference (http://www.evenmail.com/pop3.imap.html)

8. What is WWW?

Ans.The WWW is a hypertext-based system that provides a uniform and a user-friendly interface for accessing the resources on the Internet. It is an information space in which the items of interest, referred to as resources, are identified by global identifiers called Uniform Resource Identifiers .

9. Discuss the architecture of WWW.

Ans.The architecture of WWW is two tiered. It consists of the client and the server. The client (web browser) requests for a web page. This page is retrieved from the server. The architecture depends on three key standards: HTML for encoding document content, Uniform Resource Locator (URL) for naming remote information objects in a global namespace, and HTTP for staging the transfer. The following figure shows the two-tiered architecture of WWW.

CLIENTSERVER DATABASE

Request

Response

Two-Tier Architecture of WWW

If the web pages are interacting with the database, then the architecture becomes three-tiered, as shown in the following figure.

Three-Tier Architecture of WWW

10. Explain the client side and server side events when a user clicks on a URL.

Ans.The client side events when a user clicks on a URL are as follows:

1. The browser locates the URL.2. The browser asks DNS for the IP address.3. DNS replies with the IP address.4. The browser makes the Transmission Control Protocol (TCP) connection to Port 80 on the machine with the above IP

address.5. The browser sends a request for the specific file.6. The server sends the required file.7. The TCP connection is closed.8. The browser displays all text information.9. The browser displays all images.

When a user clicks on a URL, the server side events are as follows:

1. Server accepts a TCP connection from a client.2. Server searches the file associated with the web page.3. File from the disk is retrieved. 4). The web page is returned to the client. 5. TCP connection is released.

11. What is the difference between SMTP and POP3?

Ans:SMTP (Simple Mail Transfer Protocol) is used for the relaying and delivery of messages. SMTP by default works on 25 port. An email client sends the email to SMTP server, The server accepts incoming connections and copies message from them into the appropriate mailboxes.

If a message cannot be delivered, an error report containing the first part of the undeliverable message is returned to the sender. SMTP is a simple ASCII protocol.

POP3 (Post Office Protocol) is used for retrieving mails from the mail server. POP3 by default works on 110 port.

POP3 begins when the user starts the mail client. The mail client establishes a TCP connection with the message transfer agent at port 110. Once the connection has been established, the POP3 protocol goes through three states in sequence:

1. Authorization. 2. Transactions. 3. Update.

12. What is routing? Differentiate between the two types of routing, direct routing and indirect routing.

Ans.Routing is the process of moving information across an internetwork from a source router to a destination router. Routing occurs at the third layer of the Open System Interconnect (OSI) model, known as the network layer. Routing protocols use metrics to evaluate what path will be the best for a packet to travel.

The differences between direct routing and indirect routing are as follows.

Direct Routing Indirect Routing

In direct routing, packet delivery occurs when the source and destination of the packet is located on the same physical network or if the packet delivery is between the last router and the destination host.

In indirect routing, the packet goes from router to router until it reaches the router connected to the same physical network as its final destination.

In direct routing, the address mapping is between the IP address of the final destination and the physical address of the final destination.

In an indirect routing, the address mapping is between the IP address of the next router and the physical address of the next router.

A packet delivery always involves one direct routing.

A packet delivery may or may not involve indirect routing.

4. Direct Routing Versus Indirect Routing

13. Discuss the various stability features of RIP.

Ans.The stability features of RIP are:

Hop-count limit: This feature limits the number of hops allowed in a path from source to destination. The maximum number of hops in a path is 15. If for some reasons the router receives a routing update that contains a new or changed entry, and if increasing the metric value by 1 causes the metric to be infinity (that is, 16), the network destination is considered unreachable. Hold-down timers: This feature is useful in preventing routing information from flooding the network when network links

are unstable. Split horizons: This feature prevents routing loops within the network.

14. What is the purpose of the route timeout timer?

Ans.The purpose of the route timeout timer is to help purge invalid routes from a RIP node. Routes that are not refreshed for a given period of time are likely to be invalid because of some change in the network. Thus, RIP maintains a timeout timer for each known route. When a route's timeout timer expires, the route is marked invalid but is retained in the table until the route-flush timer expires.

15. What is the maximum network diameter of a RIP network?

Ans.The maximum network diameter of a RIP network is 15 hops.

16. What are the drawbacks of RIP?

Ans:The drawbacks of RIP are:

RIP takes a long time to stabilize after a router failure or link failure. RIP uses more broadcasting than OSPF and hence requires more network bandwidth.

17. What is the difference between RIP and OSPF?

Ans:The main difference between RIP and OSPF is that RIP only keeps track of the closest router for each destination address whereas OSPF keeps track of a complete topological database of all connections in the local network.

18. What is a metric? What are some of the metrics used by the routing protocols?

Ans:A metric is a standard of measurement, such as path bandwidth, which is used by routing algorithms to determine the optimal path to a destination. Some of the metrics used by the routing protocols are path length, reliability, delay, bandwidth, load, and communication cost.

19. How does an audio medium differ from a video medium?

Ans.Audio: It deals with only voice. For example, a song or a lecture on any university site.

Video: It has got both voice and live image, such as a movie, a song, or a clipping of a lecture.

20. What is streaming?

Ans.Streaming is the process of receiving stored audio/video application from a server where they are placed. A client begins to play either an audio or a video once the media player of the client’s PC begins receiving the audio or video file from the server. During the process, the client will be playing audio/video from one location in the file while it is receiving the remaining parts of the file from the server. In other words, streaming avoids long download times and the need to store the entire file on the user's computer.

21. What are the drawbacks of the present Internet to drive the multimedia data?

Ans.The Internet has some drawbacks with regard to multimedia data. For example, the media player does not communicate with the streaming server directly. This delay, before play-out begins, is typically unacceptable for audio/video clips of moderate length. For this reason, audio/video streaming implementations typically have the server send the audio/video file directly to the media player process. In other words, a direct socket connection is made between the server process and the media player process.

22. Why do audio and video file need to be compressed?

Ans.Compression is required to reduce the size of audio and video so that they can be easily transmitted over the Internet. For example, a single image consisting of 1024 pixel * 1024 pixels, with each pixel encoded into 24 bits requires 3 MB of storage without compression. There are eight bits, three each for the colors red, green, and blue. It would take approximately seven minutes to send the image over a 64 kbps link. If the image is compressed at a modest 10:1 compression ratio, the storage requirement is reduced to 300 Kbytes and the transmission time also drops by a factor of 10.

23. Explain the audio streaming process.

Ans. Audio streaming is the transfer of audio-encoded packets that are decoded and sent to the client’s soundcard upon reception. The host side is responsible for encoding and packetizing the audio stream. The client side is responsible for decoding the packets and sending the decoded audio to the sound card. There are delays inherent in the overall system. These delays are contributed by the encode/decode delay, transfer delay, buffer delay, modem delay, sound card delay, and other delays. As long as the delays are kept constant, then the audio will be delivered uninterrupted.

24. What is a streaming server?

Ans.Streaming servers are meant for the audio/video streaming applications. Upon client request, a server directs an audio or a video file to the client by sending the file into a socket. Both the TCP and UDP socket connections are used. Before sending the audio/video file to a network, the file is segmented, and the segments are typically encapsulated with special headers appropriate for audio and video traffic . Streaming servers send digital video for news, entertainment, or educational content over the Internet by using RTP/RTSP. A multimedia file gets uploaded on the server and streaming servers encodes content in the latest media formats including MPEG- 4 (Moving Picture Expert Group) and the AAC (Advanced Audio Coder) audio.

25. Discuss the features of Real Time Protocol (RTP).

Ans.The features of Real Time Protocol (RTP) are:

1)RTP provides end-to-end delivery services for data with real-time characteristics such as interactive audio and video. However, RTP itself does not provide any mechanism to ensure timely delivery. It needs support from the lower layers of OSI model that actually have control over resources in switches and routers. RTP depends on Resource Reservation Protocol (RSVP) to reserve resources and to provide the requested quality of service.

2)RTP provides timestamps, sequence numbers as hooks for adding reliability, flow, and congestion control for packet delivery, but implementation is totally left to the application.

3)RTP is a protocol framework that is deliberately not complete. It is open to new payload formats and new multimedia software. By adding new profile and payload format specifications, one can tailor RTP to new data formats and new applications.

4)The flow and congestion control information of RTP is provided by Real-Time Control Protocol (RTCP) sender and receiver reports.

5)RTP/RTCP provides functionality and control mechanisms necessary for carrying real-time content. But RTP/RTCP itself is not responsible for the higher-level tasks like assembly and synchronization. These have to be done at the application level.

26. Explain RTSP.1)RTSP is a protocol that enables a media player to control the transmission of a media stream. RTSP messages use the port number 544 from the media stream. The RTSP specification, RFC 2326, permits RTSP messages to be sent over TCP or UDP. 2)RTSP server keeps a track of the state of the client for each ongoing RTSP session. For example, the server keeps track of

whether the client is in an initialization state, a play state, or a pause state. The session and sequence numbers, which are part of each RTSP request and response, help the server to keep track of the session state. The session number is fixed throughout the entire session; the client increments the sequence number each time it sends a new message; the server echoes back the session number, and the current sequence number.

27.. What are WLANs?WLAN is a network that uses high-frequency radio waves rather than wires to communicate between nodes. WLAN technologies enable users to establish wireless connections within a local area such as within a corporate or campus building, or in a public space like airport. IEEE approved the 802.11 standard for WLANs, which specifies a data transfer rate of 1-2 Mbps.

28. What is modulation?Modulation is the addition of information or the signal to an electronic or optical signal carrier. There are several reasons to modulate a signal before transmitting signal in a medium. This includes the ability of various users sharing a medium and making the signal properties physically compatible with the propagation medium.

29. What is a carrier signal?A carrier signal is a specific frequency in an analog communication channel that is modulated with an information-carrying signal. Carrier signals are commonly used in Amplitude Modulation (AM), Frequency Modulation (FM), and other radio transmissions to differentiate among channels. You turn a radio dial to select a carrier frequency. The radio then amplifies the signal carried on the selected frequency. In AM, modulation changes the strength or amplitude of the carrier signal. In FM, the frequency of the carrier signal is modulated.

30. Define SNR. SNR stands for Signal-to-Noise Ratio. It is the ratio between the typical signal level and the softest signal that can be

produced accurately.31. What is BW?

BW stands for bandwidth, which is the range within a band of frequencies or wavelengths. BW can also be defined as the amount of data that can be transmitted in a fixed amount of time. For digital devices, bandwidth is usually expressed in bits per second or bytes per second (bps). For analog devices, bandwidth is expressed in cycles per second or Hertz (Hz).

32. List out the advantages and disadvantages of WLAN.

The advantages of WLAN are:

Flexibility: Within radio coverage, nodes can communicate without further restriction. Radio waves can penetrate walls, and senders and receivers can be placed anywhere.

Easy to use: The wireless networks are easy to set-up and use. Just plug-in a base station and equip your laptops with WLAN cards.

Robustness: Wireless networks can survive disasters. Networks requiring a wired infrastructure will break down completely some time. If one base station goes down, users may be able to physically move their PCs to be in range of another.

The disadvantages of WLAN are:

Quality of Service (QoS): WLANs typically offer lower quality than wired networks. The main reasons for offering low quality are lower bandwidth due to limitations in radio transmission, higher error rates due to interference (10 -4

instead of 10-10 for fiber optics), and higher delay/delay variation. Vulnerable to interference: If a powerful transmitter operating in the same band as the wireless network is nearby, the

wireless network could be rendered completely useless. Speed: Data speeds drop as the user moves further away from the access point. Operation within limited distance: Devices will only operate at a limited distance from an access point. Obstacles

between the access point and the user such as walls, glass, water, trees and leaves can also determine the distance of operation.

Safety and security: Using radio waves for data transmission might interfere with other high-tech equipment. Additionally, the open radio interface makes eavesdropping much easier in WLANs than in the case of fiber optics.

33. Compare radio and infrared transmission.

The differences between radio and infrared transmissions are as follows.

Radio Transmission IR Transmission

Radio transmission can cover larger areas and can penetrate walls, furniture, plants, and so on.

IR transmission cannot penetrate walls or other obstacles.

Radio transmission does not typically need a direct line of sight (LOS) to exist between the receiver and the sender if the frequencies are not too high.

For good transmission quality and high data rates, typically a LOS is needed between the sender and the receiver.

Radio transmission offers very high data transfer rates than Infrared. Current radio-based products offer transmission rates up to 10 Mbps.

IR transmission offers lower transmission rates. The products using the latest version of IR Data Association interface support data transfer rates up to 4 Mbps.

In this case, shielding is not so simple. Therefore, radio transmission can interfere with other senders and electrical devices can destroy data transmission via radio.

In this case, shielding is very simple. Therefore, electrical devices do not interfere with infrared transmission.

Radio transmission is only permitted in certain frequency bands. Very limited ranges of license-free bands are available worldwide, and those available are typically not the same in all countries.

No licenses are required for infrared technology.

Radio transmission is used for wide area networks (WAN) such as microwave links and mobile cellular phones.

IR technology is normally used for devices like PDAs, laptops, notebooks, mobile phones, and so on.

WLAN technologies such as IEEE 802.11, HIPERLAN, and Bluetooth make use of this type of transmission.

Only IEEE 802.11 makes use of this type of transmission.

Radio Transmission Versus Infrared Transmission

34. Discuss the architecture of WLAN.

WLAN architecture consists of three components:

Wireless end stations Access points Basic service sets (BSS)

The wireless end station can be any device that can communicate using the 802.11 standard. These devices include laptops, workstations, and PDAs, as well as printers and scanners.

The access point (AP) is a device. It acts as a network platform for connections between WLANs or to a wired LAN and as a relay between stations attached to the same AP.

BSS is the logical component of wireless architecture. In general, it is a set of wireless stations controlled by a single management function and has two configuration options that is, Infrastructure BSS (IBSS) and Extended Service Set (ESS).

In an IBSS, the stations communicate directly to one another without the need for an access point. An ESS is a set of infrastructure BSSs that appear as a single BSS. This is important for connection redundancy but has some security issues that need to be addressed.

35. Briefly explain the WLAN protocol architecture.

Ans.In a typical WLAN setup, the IEEE 802.11 standard WLAN (Access Point) gets connected to an IEEE 802.3 standard Ethernet (Switch/HUB) via a bridge. The higher layers (application, TCP, IP) look the same for the wireless node as for the wired node. The IEEE 802.11 standard only covers the physical layer (PHY) and medium access layer (MAC) like the other 802.x LANs do. The physical layer is sub divided into the Physical Layer Convergence Protocol (PLCP) and the Physical Medium Dependent Sub Layer.

The basic tasks of the MAC layer comprise medium access, fragmentation of user data, and encryption. The PLCP sublayer provides a carrier sense signal called Clear Channel Assessment (CCA), and provides a common PHY interface for the MAC, which is independent of the transmission technology.

36. Write a note on DSSS.

Ans.Direct Sequence Spread Spectrum (DSSS) is the alternative spread spectrum method, in which the signal is spread over a wide range of frequencies using a chipping code. In the case of IEEE 802.11 DSSS, spreading is achieved by using the 11-chip sequence (+1,-1,+1,+1,-1,+1,+1,+1,-1,-1,-1), which is also called the Barker code.

37. What is cryptography?

Ans.Cryptography is the science of using mathematics to encrypt and decrypt data. Cryptography enables us to store or transmit sensitive information across insecure networks (like the Internet) so that unauthorized users except the intended recipient cannot read it.

38.. Explain cryptographic algorithms.

Ans.A cryptographic algorithm, also referred to as cipher, is a mathematical function used in the encryption and decryption process. A cryptographic algorithm works in combination with a key. The key may be a word, number, or phrase used to encrypt the plain text, also called a message. The plain text encrypts to cipher text with different keys. The security of encrypted data is entirely dependent on the strength of the cryptographic algorithm and the secrecy of the key.

39. Explain the conventional encryption model?

Ans.Before the development of public key encryption, the conventional encryption (single-key encryption) was available to secure the networks.

There are two types of encryption, classical encryption and modern encryption techniques. These are key based algorithms known as symmetric and public key algorithms.

In conventional algorithms, the encryption key can be calculated from the decryption key. Alternatively, the decryption key can be calculated from the encryption key. In these algorithms, the encryption key and the decryption key are same. These algorithms are also called secret key algorithms, or the one key algorithm. In this encryption technique, the sender and receiver agree to use a key before they communicate securely. The security of the symmetric algorithm rests in the key. The key allows users to encrypt and decrypt messages by using any encryption and decryption algorithms.

40. What is Steganography?

Ans.Steganography is a technique that is used to hide the secret message in other messages.

A few examples of steganography are:

Character marking: Selected letters of printed or type written text are overwritten in pencil. The marks are ordinarily not visible unless the paper on which text is printed or type written is held at an angle to bright light.

Invisible ink: A number of substances can be used for writing but the ink leaves no visible trace until heat or a specific chemical is applied to the paper.

Pin punctures: Small pin punctures on selected letters are ordinarily not visible unless the paper is held up in front of a light.

Typewriter correction ribbon: This is a black ribbon used between typed lines typed. The results of typing with the correction tape are visible only in good light.

41. What is cryptology?

Ans:The study of both cryptography (enciphering and deciphering) and cryptanalysis (breaking a code system) together is called cryptology.

42. RTP

RTP defines a standardized packet format for delivering audio and video over the Internet. It was developed by the audio and video transport working group of the Internet Engineering Task Force (IETF) and first published in 1996 as RFC 1889.

RTP does not have a standard TCP or UDP port from which it communicates. The only standard that it obeys is that UDP communications are done on an even port and the next higher odd port is used for TCP communications. RTP uses UDP and defines format for additional information required by an application such as sequence number and time stamp.

43. CSMA/CA

CSMA/CA is a network contention protocol that listens to a network in order to avoid collisions, unlike CSMA/CD that deals with network transmissions once collisions have been detected. CSMA/CA contributes to network traffic because before any real data is transmitted, it has to broadcast a signal onto the network in order to listen for collision scenarios and to tell other devices not to broadcast.

44.Continuous Wave (CW)

CW is the simplest form of modulation. The output of the transmitter is switched on and off, typically to form the characters of the Morse code. Transmission with CW is simple and inexpensive. The transmitted CW signal occupies less than 500 Hz of frequency space. However, there is a disadvantage to this because the CW signals is difficult to hear on a normal receiver.

45.Which layer does congestion conrol?

Network Layer Flow Control - The data link layer manages flow control based on the capacities of the devices that are in communication. The network layer manages flow control to avoid congestion on the network. Network flow control is also referred to as Congestion Control. It can permit devices to negotiate a guaranteed data rate. Static and dynamic windows may also be employed. Receiving devices can control congestion by delaying the sending of acknowledgments. To prevent the transmitter from assuming the packet was lost some protocols define packets that signal congestion and enable receiving devices to request delays in transmission.

46.OSPF:-

Open Shortest Path First (OSPF) is a link-state routing protocol for Internet Protocol (IP) networks. It uses a link state routing algorithm and falls into the group of interior routing protocols, operating within a single autonomous system (AS). It is defined as OSPF Version 2 in RFC 2328 (1998) for IPv4.[1] The updates for IPv6 are specified as OSPF Version 3 in RFC 5340 (2008).[2]

OSPF is perhaps the most widely used interior gateway protocol (IGP) in large enterprise networks. IS-IS, another link-state dynamic routing protocol, is more common in large service provider networks. The most widely used exterior gateway protocol is the Border Gateway Protocol (BGP), the principal routing protocol between autonomous systems on the Internet.

47. SERVER:-

A server is a system (software and suitable computer hardware) that responds to requests across a computer network to provide, or help to provide, a network service. Servers can be run on a dedicated computer, which is also often referred to as "the server", but many networked computers are capable of hosting servers. In many cases, a computer can provide several services and have several servers running.Servers operate within a client-server architecture, servers are computer programs running to serve the requests of other programs, the clients. Thus, the server performs some tasks on behalf of clients. The clients typically connect to the server through the network but may run on the same computer. In the context of Internet Protocol (IP) networking, a server is a program that operates as a socket listener.[1]

48. SUBNET:-

A subnetwork, or subnet, is a logically visible subdivision of an IP network.[1] The practice of dividing a network into two or more networks is called subnetting.

All computers that belong to a subnet are addressed with a common, identical, most-significant bit-group in their IP address. This results in the logical division of an IP address into two fields, a network or routing prefix and the rest field or host identifier. The rest field is an identifier for a specific host or network interface.

49.COMPRESSION:-

Compression is the reduction in size of data in order to save space or transmission time

Compression basically employs redundancy in the data:

Compression is the reduction in size of data in order to save space or transmission time. For data transmission, compression can be performed on just the data content or on the entire transmission unit (including header data) depending on a number of factors.

Content compression can be as simple as removing all extra space characters, inserting a single repeat character to indicate a string of repeated characters, and substituting smaller bit strings for frequently occurring characters. This kind of compression can reduce a text file to 50% of its original size. Compression is performed by a program that uses a formula or algorithm to determine how to compress or decompress data.

50..what is bit rate? the number of bits per second that can be transmitted along a digital network.

51. BGP:-

Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information between autonomous systems (AS).[1] The protocol is often classified as a path vector protocol but is sometimes also classed as a distance vector routing protocol. The Border Gateway Protocol does not involve traditional Interior Gateway Protocol (IGP) metrics, but makes routing decisions based on path, network policies and/or rule-sets configured by a network administrator. The Border Gateway Protocol plays a key role in the overall operation of the Internet and is involved in making core routing decisions.The Border Gateway Protocol is the successor to the Exterior Gateway Protocol (EGP) and is currently the most widely used exterior gateway protocol by Internet service providers due to the fact that BGP allows for fully decentralised routing. BGP was originally designed to help transition from the core ARPAnet model to a decentralized system that included the NSFNET backbone and its associated regional networks.

52. function of transport layer?

Transport layer provides the following functions: • Addressing and multiplexing. • Reliability. • Framing. • Congestion control. • Operates process-to-process, not ...

53. checksum?

A checksum or hash sum is a small-size datum computed from an arbitrary block of digital data for the purpose of detecting errors that may have been introduced ...

54. RTP:-

Real-time Transport ProtocolFrom Wikipedia, the free encyclopedia

Jump to: navigation, search The Real-time Transport Protocol (RTP) defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and web-based push-to-talk features.

RTP is used in conjunction with the RTP Control Protocol (RTCP). While RTP carries the media streams (e.g., audio and video), RTCP is used to monitor transmission statistics and quality of service (QoS) and aids synchronization of multiple streams. RTP is originated and received on even port numbers and the associated RTCP communication uses the next higher odd port number.

RTP is one of the technical foundations of Voice over IP and in this context is often used in conjunction with a signaling protocol which assists in setting up connections across the network.

55.pop and its working ?

A point of presence (PoP) is an artificial demarcation point or interface point between communicating entities. It may include a meet-me-room.

In the US, this term became important during the court-ordered breakup of the Bell Telephone system. A point of presence was a location where a long-distance carrier (IXC) could terminate services and provide connections into a local telephone network (LATA).[1]

An Internet point of presence is an access point to the Internet. It is a physical location that houses servers, routers, ATM switches and digital/analog call aggregators. It may be either part of the facilities of a telecommunications provider that the Internet service provider (ISP) rents or a location separate from the telecommunications provider. ISPs typically have multiple PoPs, sometimes numbering in the thousands.[citation needed] PoPs are also located at Internet exchange points and colocation centres.

56. Layers of the TCP/IP Model

The Internet Protocol Suite, TCP/IP, is a suite of protocols used for communication over the internet. The TCP/IP model was created after the OSI 7 layer model for two major reasons. First, the foundation of the Internet was built using the TCP/IP suite and through the spread of the World Wide Web and Internet, TCP/IP has been preferred. Second, a project researched by the Department of Defense (DOD) consisted of creating the TCP/IP protocols. The DOD's goal was to bring international standards which could not be met by the OSI model. Since the DOD was the largest software consumer and they preferred the TCP/IP suite, most vendors used this model rather then the OSI. Below is a side by side comparison of the TCP/IP and OSI models.

TCP/IP Model VS. OSI Model

Application Layer 7 Application

Layer 6 Presentation

Layer 5 Session

Transport Layer 4 Transport

Internet Layer 3 Network

Network Access Layer 2 Data Link

Layer 1 Physical

12.

Wireless LAN & Wireless MAN - Two-day workshop on [18th & 19th March 2002] ... LANs & Wireless MANs are gaining importance because of intra-office and ... world; History; Driving factors; Wireless gadgets present and future applications ...

57. Information security:-

Information security, sometimes shortened to InfoSec, is the practice of defending information from unauthorized access, use, disclosure, disruption, modification, perusal, inspection, recording or destruction. It is a general term that can be used regardless of the form the data may take (electronic, physical, etc...)[1]

Two major aspects of information security are:

IT security: Sometimes referred to as computer security, Information Technology Security is information security applied to technology (most often some form of computer system). It is worthwhile to note that a computer does not necessarily mean a home desktop. A computer is any device with a processor and some memory (even a calculator). IT security specialists are almost always found in any major enterprise/establishment due to the nature and value of the data within larger businesses. They are responsible for keeping all of the technology within the company secure from malicious cyber attacks that often attempt to breach into critical private information or gain control of the internal systems.

Information assurance:

The act of ensuring that data is not lost when critical issues arise. These issues include but are not limited to: natural disasters, computer/server malfunction, physical theft, or any other instance where data has the potential of being lost. Since most information is stored on computers in our modern era, information assurance is typically dealt with by IT security specialists. One of the most common methods of providing information assurance is to have an off-site backup of the data in case one of the mentioned issues arise.