Unit-1

1. What is mean by data communication?Data communication is the exchange of data (in the form of 1s and 0s) between twodevices via some form of transmission medium (such as a wire cable).

2. What are the three criteria necessary for an effective and efficient network?The most important criteria are performance, reliability and security.Performance of the network depends on number of users, type of transmissionmedium, the capabilities of the connected h/w and the efficiency of the s/w.Reliability is measured by frequency of failure, the time it takes a link to recover from thefailure and the network’s robustness in a catastrophe.Security issues include protecting data from unauthorized access and viruses.

3. What are the three fundamental characteristics determine the effectiveness of thedata communication system?The effectiveness of the data communication system depends on three fundamentalcharacteristics:Delivery: The system must deliver data to the correct destination.Accuracy: The system must deliver data accurately.Timeliness: The system must deliver data in a timely manner.

4.Define Network.A network is a set of devices connected by physical media links. A network isrecursively is a connection of two or more nodes by a physical link or two or more networksconnected by one or more nodes.

5. What is a Link?At the lowest level, a network can consist of two or more computers directly connectedby some physical medium such as coaxial cable or optical fiber. Such a physical medium is called as Link.

6. What is a node?A network can consist of two or more computers directly connected by some physical mediumsuch as coaxial cable or optical fiber. Such a physical medium is called as Links and the computer itconnects is called as Nodes.

7. Name the factors that affect the performance of the network.a. Number of Usersb. Type of transmission mediumc. Hardwared. Software

8. What are the key design issues of a computer Network?a. Connectivityb. Cost-effective Resource Sharing

c. Support for common Servicesd. Performance

9.Define Bandwidth and LatencyNetwork performance is measured in Bandwidth (throughput) and Latency (Delay). Bandwidthof a network is given by the number of bits that can be transmitted over the network in a certain period of time. Latency corresponds to how long it t5akes a message to travel from one end off a network to the other. It is strictly measured in terms of time.

10.What are the categories of Transmission media?a. Guided Mediai. Twisted –Pair cable1. Shielded TP2. Unshielded TPii. Coaxial Cableiii. Fiber-optic cableb. Unguided Mediai. Terrestrial microwaveii. Satellite Communication

11.What is the DC component?Direct current is a zero-frequency signal with constant amplitude.

12.Define Data rate?—Rate of data transmission in bits per second

13.What is Protocol?A protocol is a set of rules that govern all aspects of information communication.

14.What are the key elements of protocols?The key elements of protocols area. SyntaxIt refers to the structure or format of the data, that is the order in which they arepresented.b. SemanticsIt refers to the meaning of each section of bits.c. TimingTiming refers to two characteristics: When data should be sent and how fast they can besent.

15.List the layers of OSIa. Physical Layerb. Data Link Layerc. Network Layerd. Transport Layer

e. Session Layerf. Presentation Layerg. Application Layer

16. Which layers are network support layers?a. Physical Layerb. Data link Layer andc. Network Layers6. Which layers are user support layers?a. Session Layerb. Presentation Layer andc. Application Layer

17. Which layer links the network support layers and user support layers?The Transport layer links the network support layers and user support layers.

18. What are the concerns of the Physical Layer?Physical layer coordinates the functions required to transmit a bit stream over a physical medium.a. Physical characteristics of interfaces and mediab. Representation of bitsc. Data rated. Synchronization of bitse. Line configurationf. Physical topologyg. Transmission mode

19. What are the responsibilities of Data Link Layer?The Data Link Layer transforms the physical layer, a raw transmission facility, to a reliable linkand is responsible for node-node delivery.a. Framingb. Physical Addressingc. Flow Controld. Error Controle. Access Control

20.What are the responsibilities of Network Layer?The Network Layer is responsible for the source-to-destination delivery of packet possibly acrossmultiple networks (links).a. Logical Addressingb. Routing

21. What are the responsibilities of Transport Layer?The Transport Layer is responsible for source-to-destination delivery of the entire message.a. Service-point Addressingb. Segmentation and reassembly

c. Connection Controld. Flow Controle. Error Control

22. What are the responsibilities of Session Layer?The Session layer is the network dialog Controller. It establishes, maintains and synchronizes theinteraction between the communicating systems.a. Dialog controlb. Synchronization

23. What are the responsibilities of Presentation Layer?The Presentation layer is concerned with the syntax and semantics of the information exchangedbetween two systems.a. Translationb. Encryptionc. Compression

24. What are the responsibilities of Application Layer?The Application Layer enables the user, whether human or software, to access the network. Itprovides user interfaces and support for services such as e-mail, shared database management and other types of distributed information services.a. Network virtual Terminalb. File transfer, access and Management (FTAM)c. Mail servicesd. Directory Services

25.Dfine Topology?A topology refers to both the physical and logical layout of a network. The physical topology of a network refers to the actual layout of the computer cables and other network devices.

26.Types of topologie?Several topologies are in use for networks today. Some of the more common include.

Bus topologyRing topologyStar topologyMesh topologyTree topology

27.Define star topology? In the star topology, all computers and other network devices connect to a central device

called a hub or switch. Each connected device requires a single cable to be connected to the hub, creating a

point-to-point connection between the device and the hub.

Unit-21. What are the design issues of Data Link Layer?The Data Link Layer transforms the physical layer, a raw transmission facility, to a reliable linkand is responsible for node-node delivery.a. Framingb. Physical Addressingc. Flow Controld. Error Controle. Access Control

2.What is Flow Control?Flow control is a set of procedure that tells the sender how much data it can transmit before it must wait for an acknowledgement. It should not overwhelm the receiver.

24.Mention the categories of flow control.There are 2 methods have been developed to control flow of data across communication links.a) Stop and wait- send one from at a time.b) Sliding window- send several frames at a time.

Define sliding window flow control.In sliding window the sender can transmit several frame before needing an acknowledgement from the receiver.

Sender maintain detail about:Size of sender window.Last acknowledgement received.Last frame sent.

Receiver holds information about:Receiver window sizeLast acknowledgement sentLast frame received

23. What is Error Control ?any frames lost or damaged in transmission and coordinates the retransmission of those frames by the sender. In the data link layer, the term error control refers primarily to methods of error detection and retransmission.

25. What Automatic Repeat Request (ARQ)?Error control is both error detection and error correction. It allows the receiver to inform thesender of any frames lost or damaged in transmission and coordinates the retransmission of those frames by the sender. In the data link layer, the term error control refers primarily to

methods of error detection and retransmission. Error control in the data link layer is often implemented simply: Any time an error is detected in an exchange, specified frames are retransmitted. This process is called automatic repeat request (ARQ).

26. What is Stop-and-Wait Protocol?In Stop and wait protocol, sender sends one frame, waits until it receives confirmation from the receiver (okay to go ahead), and then sends the next frame.

27. What is Stop-and-Wait Automatic Repeat Request?Error correction in Stop-and-Wait ARQ is done by keeping a copy of the sent frame andretransmitting of the frame when the timer expires.

28.Compare Error Detection and Error Correction:The correction of errors is more difficult than the detection. In error detection, checks only anyerror has occurred. In error correction, the exact number of bits that are corrupted and location in the message are known. The number of the errors and the size of the message are important factors.

20.What are the types of errors?a. Single-Bit errorIn a single-bit error, only one bit in the data unit has changedb. Burst ErrorA Burst error means that two or more bits in the data have changed.

18.What are the functions of MAC?MAC sub layer resolves the contention for the shared media. It containssynchronization, flag, flow and error control specifications necessary to move informationfrom one place to another, as well as the physical address of the next station to receive androute a packet.

19.Difference between bridge and router?Bridge is the simpler of the two device and provide a mean of interconnecting similar LANsRouter is a more general purpose device capable of interconnecting variety of LANS and WANS.

20.Define Ethernet?Ethernet: It is a LAN protocol that is used in Bus and Star topologies and implements CSMA/CD as the medium access method

21.Draw Ethernet frame format?

22.Define the notation of Ethernet that differentiate its implementation?

• <data rate><Signaling method><Max segment length or cable type>

23.Ethernet evolution through four generations

Unit-31.What do you mean by switching network?Long distance transmission is typically done over a network of switched nodes and Nodes not concerned with content of data Data is routed by being switched from node to node

2.Mention two different Two different switching technologies— Circuit switching— Packet switching

3.Define Circuit switchingDedicated communication path between two stations• Three phases— Establish— Transfer— Disconnect• Must have switching capacity and channel capacity to establish connection• Must have intelligence to work out routing

4.List Circuit Switch Elements?Digital Switch— Provide transparent signal path between devices• Network Interface• Control Unit— Establish connections• Generally on demand• Handle and acknowledge requests• Determine if destination is free• construct path— Maintain connection— Disconnect

5.What do you mean by Blocking or Non-blocking?• Blocking— A network is unable to connect stations because all paths are in use— Used on voice systems• Short duration calls• Non-blocking— Permits all stations to connect (in pairs) at once— Used for some data connections

6.Define Location of Signaling?Subscriber to network— Depends on subscriber device and switch• Within network— Management of subscriber calls and network— more complex

7.What do you mean by In Channel Signaling?Use same channel for signaling and call— Requires no additional transmission facilities• Inband— Uses same frequencies as voice signal— Can go anywhere a voice signal can— Impossible to set up a call on a faulty speech path• Out of band— Voice signals do not use full 4kHz bandwidth— Narrow signal band within 4kHz used for control— Can be sent whether or not voice signals are present— Need extra electronics— Slower signal rate (narrow bandwidth)

8.What do you mean by Common Channel Signaling?Control signals carried over paths independent of voice channel— One control signal channel can carry signals for

multiple subscriber channels• Common control channel for these subscriber lines— Associated Mode• Common channel closely tracks inter-switch trunks— Disassociated Mode• Additional nodes (signal transfer points)• Effectively two separate networks

9.SS7 Signaling Network Elements?Signaling point (SP)— Any point in the network capable of handling SS7 control message• Signal transfer point (STP)— A signaling point capable of routing control messages• Control plane— Responsible for establishing and managingconnections• Information plane— Once a connection is set up, info is transferred in theinformation plane

10.State the principle of packet switching ?Data transmitted in small packets— Typically 1000 octets— Longer messages split into series of packets— Each packet contains a portion of user data plussome control info• Control info— Routing (addressing) info• Packets are received, stored briefly (buffered) and past on to the next node— Store and forward

11.List the advantage of packet switching?Line efficiency— Single node to node link can be shared by many packets over time— Packets queued and transmitted as fast as possible• Data rate conversion— Each station connects to the local node at its own speed— Nodes buffer data if required to equalize rates• Packets are accepted even when network is busy— Delivery may slow downPriorities can be used

12.List the switching concepts in packet switching?Packets handled in two ways— Datagram— Virtual circuit

13.Stae the principle of Datagram.• Each packet treated independently• Packets can take any practical route• Packets may arrive out of order• Packets may go missing• Up to receiver to re-order packets and recover from missing packets

14.Stae the principle of virtual circuitPreplanned route established before any packets sent• Call request and call accept packets establish connection (handshake)• Each packet contains a virtual circuit identifier instead of destination address• No routing decisions required for each packet• Clear request to drop circuit• Not a dedicated path

15.List three layer of X.25?— Physical— Link— Packet

16.What is the goal of internetworking ? The goal of internetworking is “universal service across heterogeneous networks” Routers must agree to forward information from a source on one network to a specified

destination or another. This task is complex because frame formats and addressing schemes used by the

underlying networks can differ. 17.What do you mean by routing and list its characterstics?

Used for selection of route with minimum hop and Least cost Complex, crucial aspect of packet switched networksCharacteristics required

CorrectnessSimplicityRobustnessStabilityFairnessOptimalityEfficiency

18.Routing StrategiesFixedFloodingRandomAdaptive

19.Define Fixed Routing

Single permanent route for each source to destination pairDetermine routes using a least cost algorithm Route fixed, at least until a change in network topology

20.Define Flooding ?No network info requiredPacket sent by node to every neighborIncoming packets retransmitted on every link except incoming linkEventually a number of copies will arrive at destinationEach packet is uniquely numbered so duplicates can be discardedNodes can remember packets already forwarded to keep network load in boundsCan include a hop count in packets

21Define Random Routing?z Node selects one outgoing path for retransmission of incoming packetz Selection can be random or round robinz Can select outgoing path based on probability calculationz No network info neededz Route is typically not least cost nor minimum hopz

22.Define Adaptive Routing?z Used by almost all packet switching networksz Routing decisions change as conditions on the network change

y Failurey Congestion

z Requires info about networkz Decisions more complexz Tradeoff between quality of network info and overheadz Reacting too quickly can cause oscillationz Too slowly to be relevant

23.Purpose of ICMP?• Extranormal communication among routers and hosts is sometimes necessary to:

– Report errors– Handle abnormal conditions– Update routing information

• The Internet Protocol defines a single mechanism for these types of messages is called ICMP.

•24.List the three beginning field of ICMP?

– TYPE (1 octet) - identifies the message– CODE (1 octet) - information about the subtype– CHECKSUM (2 octets) - covers the ICMP message –

25.When Congestion occur and how to control it?

When one part of the subnet (e.g. one or more routers in an area) becomes overloaded, congestion results. Because routers are receiving packets faster than they can forward them.One of two things must happen:

The subnet must prevent additional packets from entering the congested region until those already present can be processed.

The congested routers can discard queued packets to make room for those that are arriving

26.Mention Several techniques employed for Congestion?• Several techniques can be employed. These include:

– Warning bit– Choke packets– Load shedding– Random early discard– Traffic shaping

• The first 3 deal with congestion detection and recovery. The last 2 deal with congestion avoidance.

Unit-41. What is function of transport layer?The protocol in the transport layer takes care in the delivery of data from one application program on one device to an application program on another device. They act as a link between the upper layer protocols and the services provided by the lower layer.

2. What are the duties of the transport layer?The services provided by the transport layerEnd-to- end deliveryAddressingReliable deliveryFlow controlMultiplexing

3. What is the difference between network layer delivery and the transport layerdelivery?Network layer delivery

1) The network layer is responsible for the the source-to-destination delivery ofpacket2) The transport layer is responsible for source-to-destination delivery of the entiremessage.3) Transport layer delivery across multiple network links.4) The transport layer is responsible for source-to-destination delivery of the entiremessage.

4. What are the four aspects related to the reliable delivery of data?The four aspects are, Error control, Sequence control, Loss control, Duplicationcontrol.

5. What is meant by segment?At the sending and receiving end of the transmission, TCP divides long transmissionsinto smaller data units and packages each into a frame called a segment.

6. What is meant by segmentation?When the size of the data unit received from the upper layer is too long for thenetwork layer datagram or data link layer frame to handle, the transport protocol divides itinto smaller usable blocks. The dividing process is called segmentation.

7. The transport layer creates the connection between source and destination. Whatare the three events involved in the connection?For security, the transport layer may create a connection between the two end ports. Aconnection is a single logical path between the source and destination that is associatedwith all packets in a message. Creating a connection involves three steps:1) ıConnection establishment2) Data transfer & Connection release.8. What is meant by congestion?Congestion in a network occurs if user sends data into the network at a rate greaterthan that allowed by network resources.

9. Why the congestion occurs in network?Congestion occurs because the switches in a network have a limited buffer size tostore arrived packets.

10. What is meant by quality of service?The quality of service defines a set of attributes related to the performance of theconnection. For each connection, the user can request a particular attribute each serviceclass is associated with a set of attributes.

11.What do you mean by padding?The TCP header padding is used to ensure that the TCP header ends and data begins on a 32 bit boundary. The padding is composed of zeros

12. What is Round Trip Time?

The duration of time it takes to send a message from one end of a network to the other andback, is called RTT

13.What is Multiplexing?Multiplexing is the set of techniques that allows the simultaneous transmission of multipleSignals across a single data link.

14.List the application of TCP/IP?have a number of standard TCP/IP applications such as

Simple Mail Transfer Protocol (SMTP)File Transfer Protocol (FTP) – control and data connectionsTelnet

15.What is UDP? an alternative to TCP no guaranteed delivery no preservation of sequence no protection against duplication minimum overhead Just adds port addressing to IP

16.Draw the format of UDP?

t of U

UNIT-51. What is the purpose of Domain Name System?

Domain Name System can map a name to an address and conversely an address toname.

2. Discuss the three main division of the domain name space.Domain name space is divided into three different sections: generic domains, countrydomains & inverse domain.Generic domain: Define registered hosts according to their generic behavior, usesgeneric suffixes.Country domain: Uses two characters to identify a country as the last suffix.Inverse domain: Finds the domain name given the IP address.

3. Discuss the TCP connections needed in FTP.

FTP establishes two connections between the hosts. One connection is used for datatransfer, the other for control information. The control connection uses very simple rules ofcommunication. The data connection needs more complex rules due to the variety of datatypes transferred.

4. Discuss the basic model of FTP.The client has three components: the user interface, the client control process, and theclient data transfer process. The server has two components: the server control process andthe server data transfer process. The control connection is made between the controlprocesses. The data connection is made between the data transfer processes.

5. What is the function of SMTP?The TCP/IP protocol supports electronic mail on the Internet is called Simple MailTransfer (SMTP). It is a system for sending messages to other computer users based on emailaddresses. SMTP provides mail exchange between users on the same or differentcomputers.

6. What is the difference between a user agent (UA) and a mail transfer agent(MTA)?The UA prepares the message, creates the envelope, and puts the message inthe envelope. The MTA transfers the mail across the Internet.

7. How does MIME enhance SMTP?MIME is a supplementary protocol that allows non-ASCII data to be sent throughSMTP. MIME transforms non-ASCII data at the sender site to NVT ASCII data anddeliverers it to the client SMTP to be sent through the Internet. The server SMTP at thereceiving side receives the NVT ASCII data and delivers it to MIME to be transform feedback to the original data.

8. Why is an application such as POP needed for electronic messaging?

Workstations interact with the SMTP host, which receives the mail on behalf ofevery host in the organization, to retrieve messages by using a client-server protocol suchas Post Office Protocol, version 3(POP3). Although POP3 is used to download messages

from the server, the SMTP client still needed on the desktop to forward messages from theworkstation user to its SMTP mail server.

9. Write down the three types of WWW documents.The documents in the WWW can be grouped into three broad categories: static,dynamic and active.Static: Fixed-content documents that are created and stored in a server.Dynamic: Created by web server whenever a browser requests the document.Active: A program to be run at the client side.

10. What is the purpose of SNMP?

• SNMP is a framework that provides facilities for managing and monitoring network resources on the Internet.

11. List the Components of SNMP:

• SNMP agents

• SNMP managers

• Management Information Bases (MIBs)

• SNMP protocol itself

12. Define SNMP agent?

• SNMP agent is software that runs on a piece of network equipment (host, router, printer, or others) and that maintains information about its configuration and current state in a database

13. Define Traps?

• Traps are messages that asynchronously sent by an agent to a manager

• Traps are triggered by an event