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CS6250 COMPUTER NETWORKS EXAM 1
ACTUAL EXAM PREP/STUDY GUIDE 2026 ALL
QUESTIONS AND CORRECT DETAILED
ANSWERS ALREADY A GRADED WITH EXPERT
FEEDBACK|CURRENTLY TESTING |NEW AND
REVISED
What is the EvoArch model? - ANSWER- An hourglass shaped model
of the Internet where the outer bands are more frequently modified or
replaced and the further in you go the harder it is for that layer to be
altered or modified.
Explain a round in the EvoArch model. - ANSWER- EvoArch is a
discrete-time model that is executed over rounds. At each round, we
perform the following steps: A) We introduce new nodes, and we place
them randomly at layers. B) We examine all layers, from the top to the
bottom, and we perform the following tasks: 1) We connect the new
nodes that we may have just introduced to that layer, by choosing
substrates based on the generality probabilities of the layer below s(l−1),
and by choosing products for them based on the generality probability of
the current layer s(l). 2) We update the value of each node at each layer
l, given that we may have new nodes added to the same layer l. 3) We
examine all nodes, in order of decreasing value in that layer, and remove
the nodes that should die. C) Finally, we stop the execution of the model
when the network reaches a given number of nodes.
What are the ramifications of the hourglass shape of the internet? -
ANSWER- A. Many technologies that were not originally designed for
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the internet have been modified so that they have versions that can
communicate over the internet (such as Radio over IP).
B. It has been a difficult and slow process to transition to IPv6, despite
the shortage of public IPv4 addresses.
Repeaters, hubs, bridges, routers operate on which layers? - ANSWER-
Repeaters and Hubs work over L1 (Physical Layer)
Bridges and Layer 2-Switches work over L2 (Data link layer)
Routers and Layer 3-Switches work over L3 (Network layer)
What is a bridge, and how does it "learn"? - ANSWER- A bridge is a
device with multiple inputs/outputs. A bridge transfers frames from an
input to one (or multiple) outputs. Though it doesn't need to forward all
the frames it receives.
A learning bridge learns, populates and maintains a forwarding table.
The bridge consults that table so that it only forwards frames on specific
ports, rather than over all ports. So how does the bridge learn? When the
bridge receives any frame this is a "learning opportunity" to know which
hosts are reachable through which ports. This is because the bridge can
view the port over which a frame arrives and the source host.
What is a distributed algorithm? - ANSWER- A distributed algorithm is
an algorithm designed to run on computer hardware constructed from
interconnected processors. Distributed algorithms are used in many
varied application areas of distributed computing, such as
telecommunications, scientific computing, distributed information
processing, and real-time process control.
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https://en.wikipedia.org/wiki/Distributed_algorithm
Explain the Spanning Tree Algorithm. - ANSWER- The algorithm runs
in "rounds" and at every round each node sends to each neighbor node a
configuration message with three fields: a) the sending node's ID, b) the
ID of the roots as perceived by the sending node, and c) the number of
hops between that (perceived) root and the sending node.
At every round, each node keeps track of the best configuration message
that it has received so far, and it compares that against the configuration
messages it receives from neighboring nodes at that round.
At the very first round of the algorithm, every node thinks that it is the
root.
What is the purpose of the Spanning Tree Algorithm? - ANSWER- The
purpose of the Spanning Tree Algorithm is to prevent broadcast storm
through the network and cause stalls or heavy congestion.
The spanning tree also prevents loops (cycles) from occurring in a
network.
What does the transport layer provide? - ANSWER- The transport layer
is the logical connection. Transport layer consists of TCP and UDP
protocols. The transport layer provides an end-to-end connection
between two applications that are running on different hosts. Of course
the transport layer provides this logical connection regardless if the hosts
are in the same network. User datagram protocol (UDP) and the
Transmission Control Protocol (TCP).
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-Some applications that use UDP include video streaming, DNS, and
Online Multiplayer Games.
- Some applications that use TCP include Web, SMTP and FTP
What is a packet for the transport layer called? - ANSWER- WA
segment. (If it is a TCP packet)
Datagram (If it is UDP packet)
What are the two main protocols within the transport layer? - ANSWER-
User datagram protocol (UDP) and the Transmission Control Protocol
(TCP).
What is multiplexing, and why is it necessary? - ANSWER-
Multiplexing is the ability for a host to run multiple applications using
the network simultaneously. It's necessary to ensure multi-tasking with
the host.
Multiplexing essentially combines multiple signals into one with 1 IP
and multiple ports, where each application binds itself to a port. Allow
multiple apps to communite to different servers with 1 IP address
Describe the two types of multiplexing/demultiplexing. - ANSWER- 1.
Connectionless Multiplexing/Demultiplexing: Uses the UDP socket that
consists of a two-tuple made up of a destination IP address and port.
Transport layer identifies port from receiverd datagram that includes the
port.
CS6250 COMPUTER NETWORKS EXAM 1
ACTUAL EXAM PREP/STUDY GUIDE 2026 ALL
QUESTIONS AND CORRECT DETAILED
ANSWERS ALREADY A GRADED WITH EXPERT
FEEDBACK|CURRENTLY TESTING |NEW AND
REVISED
What is the EvoArch model? - ANSWER- An hourglass shaped model
of the Internet where the outer bands are more frequently modified or
replaced and the further in you go the harder it is for that layer to be
altered or modified.
Explain a round in the EvoArch model. - ANSWER- EvoArch is a
discrete-time model that is executed over rounds. At each round, we
perform the following steps: A) We introduce new nodes, and we place
them randomly at layers. B) We examine all layers, from the top to the
bottom, and we perform the following tasks: 1) We connect the new
nodes that we may have just introduced to that layer, by choosing
substrates based on the generality probabilities of the layer below s(l−1),
and by choosing products for them based on the generality probability of
the current layer s(l). 2) We update the value of each node at each layer
l, given that we may have new nodes added to the same layer l. 3) We
examine all nodes, in order of decreasing value in that layer, and remove
the nodes that should die. C) Finally, we stop the execution of the model
when the network reaches a given number of nodes.
What are the ramifications of the hourglass shape of the internet? -
ANSWER- A. Many technologies that were not originally designed for
,2|P a g e
the internet have been modified so that they have versions that can
communicate over the internet (such as Radio over IP).
B. It has been a difficult and slow process to transition to IPv6, despite
the shortage of public IPv4 addresses.
Repeaters, hubs, bridges, routers operate on which layers? - ANSWER-
Repeaters and Hubs work over L1 (Physical Layer)
Bridges and Layer 2-Switches work over L2 (Data link layer)
Routers and Layer 3-Switches work over L3 (Network layer)
What is a bridge, and how does it "learn"? - ANSWER- A bridge is a
device with multiple inputs/outputs. A bridge transfers frames from an
input to one (or multiple) outputs. Though it doesn't need to forward all
the frames it receives.
A learning bridge learns, populates and maintains a forwarding table.
The bridge consults that table so that it only forwards frames on specific
ports, rather than over all ports. So how does the bridge learn? When the
bridge receives any frame this is a "learning opportunity" to know which
hosts are reachable through which ports. This is because the bridge can
view the port over which a frame arrives and the source host.
What is a distributed algorithm? - ANSWER- A distributed algorithm is
an algorithm designed to run on computer hardware constructed from
interconnected processors. Distributed algorithms are used in many
varied application areas of distributed computing, such as
telecommunications, scientific computing, distributed information
processing, and real-time process control.
,3|P a g e
https://en.wikipedia.org/wiki/Distributed_algorithm
Explain the Spanning Tree Algorithm. - ANSWER- The algorithm runs
in "rounds" and at every round each node sends to each neighbor node a
configuration message with three fields: a) the sending node's ID, b) the
ID of the roots as perceived by the sending node, and c) the number of
hops between that (perceived) root and the sending node.
At every round, each node keeps track of the best configuration message
that it has received so far, and it compares that against the configuration
messages it receives from neighboring nodes at that round.
At the very first round of the algorithm, every node thinks that it is the
root.
What is the purpose of the Spanning Tree Algorithm? - ANSWER- The
purpose of the Spanning Tree Algorithm is to prevent broadcast storm
through the network and cause stalls or heavy congestion.
The spanning tree also prevents loops (cycles) from occurring in a
network.
What does the transport layer provide? - ANSWER- The transport layer
is the logical connection. Transport layer consists of TCP and UDP
protocols. The transport layer provides an end-to-end connection
between two applications that are running on different hosts. Of course
the transport layer provides this logical connection regardless if the hosts
are in the same network. User datagram protocol (UDP) and the
Transmission Control Protocol (TCP).
, 4|P a g e
-Some applications that use UDP include video streaming, DNS, and
Online Multiplayer Games.
- Some applications that use TCP include Web, SMTP and FTP
What is a packet for the transport layer called? - ANSWER- WA
segment. (If it is a TCP packet)
Datagram (If it is UDP packet)
What are the two main protocols within the transport layer? - ANSWER-
User datagram protocol (UDP) and the Transmission Control Protocol
(TCP).
What is multiplexing, and why is it necessary? - ANSWER-
Multiplexing is the ability for a host to run multiple applications using
the network simultaneously. It's necessary to ensure multi-tasking with
the host.
Multiplexing essentially combines multiple signals into one with 1 IP
and multiple ports, where each application binds itself to a port. Allow
multiple apps to communite to different servers with 1 IP address
Describe the two types of multiplexing/demultiplexing. - ANSWER- 1.
Connectionless Multiplexing/Demultiplexing: Uses the UDP socket that
consists of a two-tuple made up of a destination IP address and port.
Transport layer identifies port from receiverd datagram that includes the
port.
