CS 440 EXAM 1 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026
What kind of network does Postal Service Model use? - Answers Packet-Switched Network
These are:
1. Connectionless - Don't have to reserve before sending
2. Packet-Oriented - large messages are chopped up into smaller pieces called packets - Answers
Packet-Switched Network
How does the postal service model work? - Answers 1. moves data from place to place using
forwarding straight to end points (hop by hop)
2. data carries destination address
3. Setup overhead is low or non-existent (it exists on the path)
What kind of network does the telco model use? - Answers Circuit-Switched Network
These are connection-oriented. (Must set up connection before sending) - Answers Circuit-Switched
Network
How does the TELCO model work? - Answers 1. source destination must be established before
message is sent
2. data does not need destination address and follows the established path
3. overhead does not exist on path, but does on setup and teardown
What is layering? - Answers Layering is a tool for abstraction to capture the properties that matter.
1. Each layer provides a new abstraction of how the network works
2. Each layer doesn't have to know unnecessary details. Just the important parts
3. Higher levels don't depend on how lower layers do their job
What are the benefits of layering? - Answers 1. It decomposes the problem of building a network into
more manageable components.
This makes things simpler because each layer has its own job which in turn {hopefully} makes it more
efficient
2. It provides a more modular design.
If a new service needs to be added, modifications may only need to be made to the functionality at
one layer, reusing the functions at other layers
What is a protocol? - Answers The abstract objects that make up the layers of a network system.
A protocol provides a communication service that higher-level objects use to exchange messages.
What is abstraction? - Answers The hiding of implementation details behind a well-defined interface.
It is a tool used to manage complexity
Each protocol defines 2 different interfaces. What are they? - Answers Service interface
Peer interface
What is service interface? - Answers It defines the operations that local objects can perform on the
protocol. This happens on the same computer.
What is peer interface? - Answers It defines the form and meaning of messages exchanged between
protocol peers to implement the communication service. This happens on another machine.
What does encapsulation mean? - Answers It is the process of adding a header (if attaching to the
front) or trailer (if attaching to the end) to the payload (message body) when it is moving down the
stack from the application layer.
, It is used for allowing peers to communicate with each other
the headers and trailers are defined by its protocol specification.
What is multiplexing and demultiplexing? - Answers Multiplexing and Demultiplexing is done (using
multiplexores) when a system resource needs to be shared by multiple users.
Data from multiple hosts is multiplexed onto a single switch.
Data is demultiplexed from the switch into separate flows to multiple receivers
List the 7 layers of the OSI Model and give a brief description of each. - Answers 7. application:
services exposed to the user
6. presentation: handles data formats
5. session: provides a namespace to manage message streams
4. transport: process to process communication.
bits are organized as messages
3. network: handles communication between nodes.
bits are organized as packets
2. data link: groups of bits organized as a frame.
gives us reliable delivery
1. physical: handles raw bits on the wire
What is the socket API? - Answers The endpoint for communication.
Where the local application process attaches to the network.
Defines the point between the applications running on top of the internet and the details of how the
internet is implemented
Server Pattern - Answers socket() - create the socket
bind() - attach the socket to the network address to the local participant
listen() - listen for incoming connections
accept() - accept the incoming socket connection
send() or receive() - sends or receives data
close() - close the socket
Client Pattern - Answers socket() - create the socket
connect() - connect to the desired network (server)
send() or receive() - send or receive data
close() - close the socket
Define Bandwidth - Answers 1. data rate - the number of bits that can be transmitted per unit time
2. frequency range - the width of the pulse on the link
Define latency - Answers the time it takes a bit to travel end-to-end over a length
What is one-way latency? - Answers How long it takes the bit to get from here to there
Define throughput - Answers Indicates the measured performance of the link vs. the theoretical
capacity (bandwidth)
Define Round Trip Time (RTT) - Answers Latency both ways
What kind of network does Postal Service Model use? - Answers Packet-Switched Network
These are:
1. Connectionless - Don't have to reserve before sending
2. Packet-Oriented - large messages are chopped up into smaller pieces called packets - Answers
Packet-Switched Network
How does the postal service model work? - Answers 1. moves data from place to place using
forwarding straight to end points (hop by hop)
2. data carries destination address
3. Setup overhead is low or non-existent (it exists on the path)
What kind of network does the telco model use? - Answers Circuit-Switched Network
These are connection-oriented. (Must set up connection before sending) - Answers Circuit-Switched
Network
How does the TELCO model work? - Answers 1. source destination must be established before
message is sent
2. data does not need destination address and follows the established path
3. overhead does not exist on path, but does on setup and teardown
What is layering? - Answers Layering is a tool for abstraction to capture the properties that matter.
1. Each layer provides a new abstraction of how the network works
2. Each layer doesn't have to know unnecessary details. Just the important parts
3. Higher levels don't depend on how lower layers do their job
What are the benefits of layering? - Answers 1. It decomposes the problem of building a network into
more manageable components.
This makes things simpler because each layer has its own job which in turn {hopefully} makes it more
efficient
2. It provides a more modular design.
If a new service needs to be added, modifications may only need to be made to the functionality at
one layer, reusing the functions at other layers
What is a protocol? - Answers The abstract objects that make up the layers of a network system.
A protocol provides a communication service that higher-level objects use to exchange messages.
What is abstraction? - Answers The hiding of implementation details behind a well-defined interface.
It is a tool used to manage complexity
Each protocol defines 2 different interfaces. What are they? - Answers Service interface
Peer interface
What is service interface? - Answers It defines the operations that local objects can perform on the
protocol. This happens on the same computer.
What is peer interface? - Answers It defines the form and meaning of messages exchanged between
protocol peers to implement the communication service. This happens on another machine.
What does encapsulation mean? - Answers It is the process of adding a header (if attaching to the
front) or trailer (if attaching to the end) to the payload (message body) when it is moving down the
stack from the application layer.
, It is used for allowing peers to communicate with each other
the headers and trailers are defined by its protocol specification.
What is multiplexing and demultiplexing? - Answers Multiplexing and Demultiplexing is done (using
multiplexores) when a system resource needs to be shared by multiple users.
Data from multiple hosts is multiplexed onto a single switch.
Data is demultiplexed from the switch into separate flows to multiple receivers
List the 7 layers of the OSI Model and give a brief description of each. - Answers 7. application:
services exposed to the user
6. presentation: handles data formats
5. session: provides a namespace to manage message streams
4. transport: process to process communication.
bits are organized as messages
3. network: handles communication between nodes.
bits are organized as packets
2. data link: groups of bits organized as a frame.
gives us reliable delivery
1. physical: handles raw bits on the wire
What is the socket API? - Answers The endpoint for communication.
Where the local application process attaches to the network.
Defines the point between the applications running on top of the internet and the details of how the
internet is implemented
Server Pattern - Answers socket() - create the socket
bind() - attach the socket to the network address to the local participant
listen() - listen for incoming connections
accept() - accept the incoming socket connection
send() or receive() - sends or receives data
close() - close the socket
Client Pattern - Answers socket() - create the socket
connect() - connect to the desired network (server)
send() or receive() - send or receive data
close() - close the socket
Define Bandwidth - Answers 1. data rate - the number of bits that can be transmitted per unit time
2. frequency range - the width of the pulse on the link
Define latency - Answers the time it takes a bit to travel end-to-end over a length
What is one-way latency? - Answers How long it takes the bit to get from here to there
Define throughput - Answers Indicates the measured performance of the link vs. the theoretical
capacity (bandwidth)
Define Round Trip Time (RTT) - Answers Latency both ways
