It250 - Data Commun & Networks Midterm

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What's the Data unit for Physical layer?

bits

A router filters packets based on the _________ destination addresses

network-layer

Twisting in a twisted-pair help reduce the

noise

What would be the consequence if a connection fails in a star topology.

only the failing connection is affected. All other connections/links remain active.

A link-layer switch is a connecting device that operates in the _________ layer(s)

physical and data-link

A router is a connecting device that operates in the _________ layer(s)

physical, data-link, and network

In a __________ link, the link is not shared between devices.

point-to-point

In a datagram network, the destination address _______________

remains the same from the source to the destination.

A _______ breaks up collision domain and broadcast domain

router

A _______ increases the number of broadcast domains.

router

What's the Data unit for Transport layer?

segment

In the 1-persistent approach, when a station finds an idle line, it _______

sends immediately

Looping problems in a set of switches can be eliminated using __________ algorithm.

spanning-tree

From the four basic network topologies (mesh, star, bus, ring), which one is collision free.

star, mesh

In ___ TDM, slots are dynamically allocated to improve bandwidth efficiency.

statistical

A _______ breaks up collision domain and increases bandwidth

switch

A _______ increases the number of collision domains.

switch

In ___ TDM, each input connection has an allotment in the output even if it is not sending data.

synchronous

If the sender is a host and wants to send a packet to another host on another network, the logical address that must be mapped to a physical address is ______.

the destination IP address in the datagram header

The sender is a router that has received a datagram destined for a host in the same network. The logical address that must be mapped to a physical address is______.

the destination IP address in the datagram header

An ARP reply is normally ____________

unicast

What's the Data unit for Network layer?

user datagram

In a _________ network, all packets in a message follow the same path.

virtual circuit

What is the number of physical links in a fully connected mesh network with n nodes?

(n(n-1))/2

Identify the two principles upon which the protocol layering is based on.

1. Corresponding layers at both end should be identical. 2. Each layer needs to have two opposite tasks.

A router is involved in _________________ layers of the TCP?IP protocol suite.

3

In a circuit-switching network, we have _____ phase(s).

3

The TCP/IP protocol suite consists of _________ layers.

5

Why does a router normally have more than one interface?

An interface is a connection to a link. A router has more than one interface because it is an internetwork device meaning it is connected to different links enabling internetwork communication. Router used one interface for each network it is connected to.

________ data are continuous and take continuous values.

Analog

____________ is a type of transmission impairment in which the signal loses strength due to the resistance of the transmission medium.

Attenuation

What is the difference between bandwidth and throughput?

Bandwidth is a Theoretical data transfer rate. Throughput is a actual data transfer rate.

The __________ product defines the number of bits that can fill the link.

Bandwidth-delay

How many collision domains and broadcast domains are in the network described? A router connecting a hub and switch. A hub connected to 3 computers. A switch connected to 3 computers.

Broadcast domains - 2 Collision domains - 5

We need RTS and CTS packets in _____ protocol.

CDMA/CA

In the __________ random-access method, collision is avoided.

CSMA/CD

Which of the following is a variation of twisted-pair cable used to connect network devices and hosts?

Crossover cable Straight through cable rollover cable

The _____ technique expands the bandwidth of a signal by replacing each data bit with n bits using a spreading code.

DSSS (Direct Sequence Spread Spectrum)

_______ signals can have only a limited number of values in a time interval.

Digital

_________ data have discrete states and take discrete values.

Digital

Which multiplexing technique is used for analog signals?

FDM (Frequency Division Multiplexing)

What is the difference between half-duplex and full-duplex transmission modes?

Half-duplex: each station can both transmit and receive, but not at the same time. Full-duplex: both stations can transmit and receive simultaneously.

Explain why collision is an issue in random access protocols but not in controlled access protocols.

In random access protocol, transmission is random and stations compete with one another to access the medium.

List some strategies in CSMA/CA that are used to avoid collision.

Interframe Space (IFS) Contention window Acknowledgement

What are some factors that determine whether a communication system is a LAN or WAN?

LAN: privately owned, limited is size, interconnects hosts. WAN: created and run by telecommunication companies, wider geographical span, interconnects connecting devices.

From the four basic network topologies (mesh, star, bus, ring), which one is more reliable.

Mesh

_____ is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

Multiplexing

_________ is a type of transmission impairment in which an outside source such as crosstalk corrupts a signal.

Noise

A router connects three links (networks). Which of the following layers can the router be involved with?

Physical layer Data-link layer Network layer

Which of the following are the most important criteria of a network?

Security, Performance, Reliability

Discuss the main benefit of protocol layering model.

Separation of services from implementation / modularity

Why is the destination hardware address all 0s in the ARP request message?

Since the sender does not know the sender MAC address (goal of the ARP), the field is populated with 0s.

We can divide ____ into two different schemes: synchronous or statistical.

TDM (Time Division Multiplexing)

_________ is (are) a channelization protocol.

TDMA, FDMA, CDMA

Discuss the performance metrics of a data communication network.

Throughput, Delay, reliability, security

Why are protocols needed in a communication system?

To govern/manage communication

Which of the following is an example of a controlled-access protocol?

Token passing

UTP and STP are different implementations of ____________ cable.

Twisted-pair

Which of the following is a guided medium?

Twisted-pair cable Coaxial cable fiber-optic cable

An ARP request is normally ____________

Unicast

A __________ is a local address. Its jurisdiction is over a local network.

link-layer address

From the four basic network topologies (mesh, star, bus, ring), which one is more expensive to implement.

mesh

Which multiplexing technique involves signals composed of light beams?

WDM (Wavelength Division Multiplexing)

_____ is an analog multiplexing technique to combine optical signals.

WDM (Wavelength Division Multiplexing)

How many IP addresses and how many link-layer addresses should a router have when it is connected to five links?

When connected to 5 links, a router should have 5 IP addresses and 5 link-layer addresses

From the four basic network topologies (mesh, star, bus, ring), which one is the most effective in fault isolation.

mesh, star

Name the four basic network topologies.

mesh, star, bus, ring.

When you connect to the internet to send an email to a friend, you are using....

a packet-switched network

What would be the consequence if a connection fails in a bus topology.

all transmissions stop

Which of the following is not a guided medium?

atmosphere

In a __________ link, the link is shared between devices.

broadcast

Media access control can be presented only in a ____________ link(s)

broadcast

Identify the five components of a data communication system.

message, sender, receiver, transmission medium, protocol

A link-layer switch filters packets based on the _________ destination addresses

data-link

In a ________ network, each packet is treated independently from all other packets.

datagram

In a _________ network, each packet in a message may follow a different path.

datagram

In a datagram network, the routing table is based on the ____ in the packet

destination address

A packet at the data-link layer is normally called a ____________

frame

What's the Data unit for Data Link layer?

frame

A _______ has no filtering capability

hub

Frequency and period are ___________

inverse of each other.


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