CS6250 COMPUTER NETWORK FINAL
EXAM 2025/2026 QUESTIONS WITH
VERIFIED CORRECT SOLUTIONS ||
100% GUARANTEED PASS
<BRAND NEW VERSION>
1. What is encapsulation, and how is it used in a layered model? - ANSWER ✓
In networking model, the terms encapsulation and de-encapsulation refer to
a process in which protocol information is added to the data and removed
from the data when it passes through the layers.
Protocol information can be added before and after the data. If information is
added before the data, it is known as header. If information is added after the
data, it is known as trailer.
2. What is the end-to-end (e2e) principle? - ANSWER ✓ When a function has
to be supported in a networked system, the designer often asks if it should be
implemented at the end systems; or should it be implemented within the
communication subsystem that interconnects all the end systems. The end-
to-end argument or principle states that it's proper to implement the function
in the end systems. The communication system itself may provide a partial
implementation but only as a performance enhancement.
The architecture and growth of the Internet was shaped by the end-to-end
principle. It allowed us to keep the Internet simple and add features quickly
to end systems. The principle enabled innovation.
3. End to End Principle Example - ANSWER ✓ An example of the end-to-end
principle is that of an arbitrarily reliable file transfer between two endpoints
in a distributed network of a varying, nontrivial size:[3] The only way two
endpoints can obtain a completely reliable transfer is by transmitting and
, acknowledging a checksum for the entire data stream; in such a setting,
lesser checksum and acknowledgment (ACK/NACK) protocols are justified
only for the purpose of optimizing performance - they are useful to the vast
majority of clients, but are not enough to fulfill the reliability requirement of
this particular application. A thorough checksum is hence best done at the
endpoints, and the network maintains a relatively low level of complexity
and reasonable performance for all clients
4. What is the EvoArch model? - ANSWER ✓ an hourglass model that consists
of six protocol and application layers that originate from a single bubble -
IPv4
5. Repeater - ANSWER ✓ Physical Layer - A repeater operates at the physical
layer. Its job is to regenerate the signal over the same network before the
signal becomes too weak or corrupted so as to extend the length to which the
signal can be transmitted over the same network. An important point to be
noted about repeaters is that they do not amplify the signal. When the signal
becomes weak, they copy the signal bit by bit and regenerate it at the
original strength. It is a 2 port device.
6. Hub - ANSWER ✓ Physical Layer - A hub is basically a multiport repeater.
A hub connects multiple wires coming from different branches, for example,
the connector in star topology which connects different stations. Hubs
cannot filter data, so data packets are sent to all connected devices. In other
words, collision domain of all hosts connected through Hub remains one.
Also, they do not have intelligence to find out best path for data packets
which leads to inefficiencies and wastage.
7. Bridge - ANSWER ✓ Data Link Layer - A bridge is a repeater, with add on
the functionality of filtering content by reading the MAC addresses of source
and destination. It is also used for interconnecting two LANs working on the
same protocol. It has a single input and single output port, thus making it a 2
port device.
8. DARPA Paper:
Main Goal - ANSWER ✓ Multiplexed utilization of existing interconnected
networks
9. DARPA Paper:
, Secondary Goals - ANSWER ✓ 1. Survivability
2. Multiple types of service
3. Variety of networks
4. Distributed management
5. Cost effective
6. Ease of attachment
7. Accountability
10.Fate Sharing (definition) - ANSWER ✓ It is acceptable to lose state
information for an entity if that entity is lost.
(i.e. If a router crashes, its routing tables can be lost)
11.Fate Sharing (consequences) - ANSWER ✓ 1. Protects against any number
of intermediate failures (vs. replication)
2. More trust placed in the host machine (vs. an architecture where the
network ensures reliable delivery)
12.DARPA Paper:
Survivability Mechanisms - ANSWER ✓ Fate sharing, replication
13.DARPA Paper:
Datagram (usefulness) - ANSWER ✓ Eliminates the need for connection
state within intermediate switching nodes.
Provides a basic building block out of which a variety of types of service can
be implemented.
Represents the minimum network service assumption, which has permitted a
wide variety of networks to be incorporated into various Internet
realizations.
14.DARPA Paper:
Datagram (definition) - ANSWER ✓ The fundamental architectural feature
of the Internet - the entity which is transported across the underlying
networks.
Important note: The role of the datagram is as a building block, and not as a
service in itself.
, 15.Network Service:
Basic Assumptions - ANSWER ✓ The network can transport a packet or
datagram of reasonable size, and it will be delivered with reasonable but not
perfect reliability.
The network must have some suitable form of addressing if it is more than a
point-to-point link.
16.Network Services:
Explicitly Not Assumed - ANSWER ✓ 1. Reliable or sequenced delivery
2. Network level broadcast or multicast
3. Priority ranking of transmitted packets
4. Support for multiple types of service
5. Internal knowledge of failures, speeds, or delays
17.Why Flow Control in TCP is Based on Byte Number (vs. packet number) -
ANSWER ✓ 1. Permits the insertion of control information into the
sequence space of the bytes. (later dropped)
2. Permits the TCP packet to be broken up into smaller packets if needed.
(later moved to the IP layer)
3. Permits a number of small packets to be gathered together into one larger
packet if retransmission of the data is necessary. (turned out to be critical)
18.DARPA Paper:
"Flow" / "Soft State" - ANSWER ✓ A building block to replace the
datagram.
It would identify a sequence of packets traveling from source to destination,
without assuming any particular type of service.
The type of service would be enforced by the end points,w hich would
periodically send messages to ensure that the proper type of service was
being associated with the flow.
19.Narrow Waist - ANSWER ✓ Every internet device "speaks" IP - allows
interconnection of existing networks while hiding underlying technology
from applications.
EXAM 2025/2026 QUESTIONS WITH
VERIFIED CORRECT SOLUTIONS ||
100% GUARANTEED PASS
<BRAND NEW VERSION>
1. What is encapsulation, and how is it used in a layered model? - ANSWER ✓
In networking model, the terms encapsulation and de-encapsulation refer to
a process in which protocol information is added to the data and removed
from the data when it passes through the layers.
Protocol information can be added before and after the data. If information is
added before the data, it is known as header. If information is added after the
data, it is known as trailer.
2. What is the end-to-end (e2e) principle? - ANSWER ✓ When a function has
to be supported in a networked system, the designer often asks if it should be
implemented at the end systems; or should it be implemented within the
communication subsystem that interconnects all the end systems. The end-
to-end argument or principle states that it's proper to implement the function
in the end systems. The communication system itself may provide a partial
implementation but only as a performance enhancement.
The architecture and growth of the Internet was shaped by the end-to-end
principle. It allowed us to keep the Internet simple and add features quickly
to end systems. The principle enabled innovation.
3. End to End Principle Example - ANSWER ✓ An example of the end-to-end
principle is that of an arbitrarily reliable file transfer between two endpoints
in a distributed network of a varying, nontrivial size:[3] The only way two
endpoints can obtain a completely reliable transfer is by transmitting and
, acknowledging a checksum for the entire data stream; in such a setting,
lesser checksum and acknowledgment (ACK/NACK) protocols are justified
only for the purpose of optimizing performance - they are useful to the vast
majority of clients, but are not enough to fulfill the reliability requirement of
this particular application. A thorough checksum is hence best done at the
endpoints, and the network maintains a relatively low level of complexity
and reasonable performance for all clients
4. What is the EvoArch model? - ANSWER ✓ an hourglass model that consists
of six protocol and application layers that originate from a single bubble -
IPv4
5. Repeater - ANSWER ✓ Physical Layer - A repeater operates at the physical
layer. Its job is to regenerate the signal over the same network before the
signal becomes too weak or corrupted so as to extend the length to which the
signal can be transmitted over the same network. An important point to be
noted about repeaters is that they do not amplify the signal. When the signal
becomes weak, they copy the signal bit by bit and regenerate it at the
original strength. It is a 2 port device.
6. Hub - ANSWER ✓ Physical Layer - A hub is basically a multiport repeater.
A hub connects multiple wires coming from different branches, for example,
the connector in star topology which connects different stations. Hubs
cannot filter data, so data packets are sent to all connected devices. In other
words, collision domain of all hosts connected through Hub remains one.
Also, they do not have intelligence to find out best path for data packets
which leads to inefficiencies and wastage.
7. Bridge - ANSWER ✓ Data Link Layer - A bridge is a repeater, with add on
the functionality of filtering content by reading the MAC addresses of source
and destination. It is also used for interconnecting two LANs working on the
same protocol. It has a single input and single output port, thus making it a 2
port device.
8. DARPA Paper:
Main Goal - ANSWER ✓ Multiplexed utilization of existing interconnected
networks
9. DARPA Paper:
, Secondary Goals - ANSWER ✓ 1. Survivability
2. Multiple types of service
3. Variety of networks
4. Distributed management
5. Cost effective
6. Ease of attachment
7. Accountability
10.Fate Sharing (definition) - ANSWER ✓ It is acceptable to lose state
information for an entity if that entity is lost.
(i.e. If a router crashes, its routing tables can be lost)
11.Fate Sharing (consequences) - ANSWER ✓ 1. Protects against any number
of intermediate failures (vs. replication)
2. More trust placed in the host machine (vs. an architecture where the
network ensures reliable delivery)
12.DARPA Paper:
Survivability Mechanisms - ANSWER ✓ Fate sharing, replication
13.DARPA Paper:
Datagram (usefulness) - ANSWER ✓ Eliminates the need for connection
state within intermediate switching nodes.
Provides a basic building block out of which a variety of types of service can
be implemented.
Represents the minimum network service assumption, which has permitted a
wide variety of networks to be incorporated into various Internet
realizations.
14.DARPA Paper:
Datagram (definition) - ANSWER ✓ The fundamental architectural feature
of the Internet - the entity which is transported across the underlying
networks.
Important note: The role of the datagram is as a building block, and not as a
service in itself.
, 15.Network Service:
Basic Assumptions - ANSWER ✓ The network can transport a packet or
datagram of reasonable size, and it will be delivered with reasonable but not
perfect reliability.
The network must have some suitable form of addressing if it is more than a
point-to-point link.
16.Network Services:
Explicitly Not Assumed - ANSWER ✓ 1. Reliable or sequenced delivery
2. Network level broadcast or multicast
3. Priority ranking of transmitted packets
4. Support for multiple types of service
5. Internal knowledge of failures, speeds, or delays
17.Why Flow Control in TCP is Based on Byte Number (vs. packet number) -
ANSWER ✓ 1. Permits the insertion of control information into the
sequence space of the bytes. (later dropped)
2. Permits the TCP packet to be broken up into smaller packets if needed.
(later moved to the IP layer)
3. Permits a number of small packets to be gathered together into one larger
packet if retransmission of the data is necessary. (turned out to be critical)
18.DARPA Paper:
"Flow" / "Soft State" - ANSWER ✓ A building block to replace the
datagram.
It would identify a sequence of packets traveling from source to destination,
without assuming any particular type of service.
The type of service would be enforced by the end points,w hich would
periodically send messages to ensure that the proper type of service was
being associated with the flow.
19.Narrow Waist - ANSWER ✓ Every internet device "speaks" IP - allows
interconnection of existing networks while hiding underlying technology
from applications.
