It250 - Data Commun & Networks Midterm
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.