1.) Which of the following statements about ATM is false?

1. ATM uses fixed sized packets to transport data.
2. ATM has a higher data to header ratio than other transport protocols.
3. ATM protocol provides bandwidth on demand.
4. ATM's Quality of Service assurance is possible because it its connection oriented ideology.

Answer.

2.) ATM can only be used in ___?

1. Local Area Network
2. Connection oriented networks.
3. Wide Area Network
4. All of the above

Answer.

3.) Which statement about circuit switching is false?

1. A connection-oriented system can be implemented with a circuit switching system.
2. A physical connection between source and destination is established first.
3. Circuit switching is a form of store and forwarding. Each block of data is sent in its entirety before being retransmitted to the next router until it reaches its destination.
4. Once communication begins, there will be no further interruptions.

Answer.

4.) Which of these statements is correct?

1. ATM is a connection oriented system and is implemented with circuit switching.
2. The OSI network model is the only correct model.
3. The internet has a connectionless network layer but it can run over ATM even though ATM has a connection oriented layer.
4. Different types of networks can be connected with the same hardware.

Answer.

5.) The problem of bridging connectionless LANs with ATM can be solved by

1. introducing a LAN Emulation Server.
2. a fully connected topology.
3. virtual circuits.
4. having repeaters to boost the signals.

Answer.

6.) What does CSMA/CD stand for?

1. Carrier Sense Multiple Access with Collision Detection
2. Cross Switching Modem Account (Compact Distribution)
3. Connective Sequence of Multiple Arrays with Cross Distortion
4. None of the above

Answer.

7.) Which of the following types of protocol data may be carried by an Ethernet system?

I. TCP/IP
II. Novell
III. AppleTalk

1. I only
2. III only
3. I & III
4. I, II & III

Answer.

8.) What is the difference between full-duplex and half-duplex transmission?

1. Full-duplex transmission can be used for Gigabit Ethernet but half-duplex transmission cannot.
2. In full-duplex transmission, signals can travel in both directions on the same connection simultaneously, while in half-duplex transmission, signals cannot travel in opposite directions simultaneously.
3. Full-duplex transmission can be used between multiple workstations and a repeater.
4. None of the above.

Answer.

9.) Which of the following is/are true of an Ethernet system?

I. A large Ethernet LAN can be created by connecting Ethernet segments in a loop.
II. If two Ethernet frames are sent down a channel at the same time, there will be a collision and both frames will be discarded and never sent.
III. Data signals from a computer are transmitted serially down a shared channel to every station of the system.

1. I only
2. III only
3. I & III
4. I, II & III

Answer.

10.) . Which of the following are fields of an Ethernet frame?

I. Data field
II. Frame Check Sequence field
III. Source Ethernet Address field

1. I only
2. III only
3. I & III
4. I, II & III

Answer.

Answers

1.)
Options 1, 3 and 4 are correct. With ATM, data is transmitted as small constant sized packets. When an ATM connection is established, a virtual circuit is set up, which reserves a predetermined bandwidth for the duration of the communication. This connection oriented ideology means that a sustained level of bandwidth can be maintained. This also provides the necessary mechanism to ensure that a connection is not delayed or interrupted by network traffic, hence offering a guaranteed Quality of Service.
Option 2 however, is wrong. ATM has a smaller packet size than other protocols. Each packet has attached with it a header. Hence it has a lower data to header ratio.
The correct answer is thus 2.

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2.)
One of ATM's strength is its ability to scale seamlessly from the desktop to LAN to WAN. ATM is not interested in the type of data it receives. It can be a series of Ethernet frames, ASCII text or data stream from a token ring system. The ATM protocol was designed to handle different data, hence making the system insensitive to the network types that it is connected to.
The correct answer is thus 4.

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3.)
A connection-oriented service is modelled after a phone network. A physical connection is maintained for the duration of a communication. Circuit switching establishes a physical connection between source and destination. In setting up this connection, it incurs two delays. The first is associated with the time taken to hunt for a path. The other is the propagation time of the actual data. Once the connection has been made, there are no further interruptions in the communication. Circuit switching does not support a store and forward system. Data from the source flows directly to the destination via the dedicated connection.
The correct answer is 3.

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4.)
Statement 1 is wrong. Although ATM is a connection oriented system, it is not implemented with circuit switching. ATM is a packet switching protocol.
Statement 2 is also wrong. There OSI is not the only network reference model. The TCP/IP model is another model that exist. In fact, the OSI model has several problems associated with it; its session layer has little use in most applications, and the presentation layer is practically empty, while the network, data link and network layers are so full that subsequent work has split them into multiple layers. In addition to being complex, another problem with OSI is that some functions like flow control and error control occur in several layers, making it inefficient.
Statement 3 is correct. If the Internet needs to run over an ATM based subnet, then the host first establishes an ATM connection to the destination before sending independent (IP) packets over it.
Statement 4 is wrong. The point to note here is that each gateway can only modify the frame fields relevant to its layer. So a bridge for example is unable to deal with headers from layer 3 and above, where as a multiprotocol router knows if its payload contains an IP or IPX packet. In other words, to bridge networks that have differing layer 3, hardware that connects at that level is needed.
The correct answer is thus 3.

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5.)
The problem to note here is that connectionless LANs operate by having a broadcasting transmission paradigm. ATM does not support broadcasting. In a broadcasting LAN, a host might send a message asking for a computer with a certain IP address. One way for this to be emulated is by introducing another server, the LES or LAN Emulation Server. Its job is to look up a network layer address. A host thus sends a packet to the LES, who returns the corresponding ATM address. This address is then used by the host to send the encapsulated packets to the correct destination.
The correct answer is thus 1.

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6.)
CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection and is the protocol designed to provide fair access to the channel shared by stations on the Ethernet.
The correct answer is thus 1.

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7.)
The Ethernet is merely a transport system that carries packages of data between computers. The system doesn’t care what is in the packages.
The correct answer is thus 4.

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8.)
Statement I is false. Full-duplex and half-duplex transmission can both be used for Gigabit Ethernet. In fact, they can be used for the original Ethernet and Fast Ethernet too.
Statement II is correct.
Statement III is false. Only half-duplex transmission can be used between multiple workstations and a repeater. Full-duplex transmission can only be used for point-to-point connections and cannot be used for shared port connections.
The correct answer is thus 2.

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9.)
Statement I is false. An Ethernet system will not function correctly if there are loop paths present so it must be guaranteed that segments are never connected in a loop.
Statement II is false. If two Ethernet frames are sent down a channel at the same time, there will be a collision and after a random interval interval of time, both stations will attempt to transmit again.
Statement III is true.
The correct answer is thus 2.

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10.)
Statement I is true. The data field contains 46 to 1500 bytes of data that will be transmitted by the Ethernet frame.
Statement II is true. The frame check sequence field is a 32 bit Cyclical Redundancy Check which checks the integrity of the bits in the frame to ensure that the frame has arrived intact.
Statement III is true. The sourc Ethernet address field is a 48 bit long address normally pre-assigned to each Ethernet interface when it is manufactured.
The correct answer is thus 4.

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