Computer Networks and Securities Midterm

Which of the following descriptions below correspond to a "nuts-and-bolts" view of the Internet? Select one or more of the answers below that are correct. [Hint: more than one of answers below are correct]. -A collection of billions of computing devices, and packet switches interconnected by links. -A platform for building network applications. -A "network of networks". -A place I go for information, entertainment, and to communicate with people. -A collection of hardware and software components executing protocols that define the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

-A collection of billions of computing devices, and packet switches interconnected by links. -A "network of networks". -A collection of hardware and software components executing protocols that define the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

Which of the following statements about CDNs are true? Select all that apply. -CDN stands for Content Distribution Network. -CDNs are formed when multiple service providers form economic and/or political agreements to transmit data to customers in the collaborating providers' networks. -CDNs store multiple copies of content at multiple geographic locations. -CDN stands for Collaborative Data Network.

-CDN stands for Content Distribution Network. -CDNs store multiple copies of content at multiple geographic locations.

Which of the following statements apply to authoritative DNS servers (as opposed to root-level DNS, top-level DNS, or local DNS)? Select all that apply. -Maintained either by an organization or by that organization's service provider -13 logical servers worldwide -Responsible for .com, .org, .net, .edu, etc. -Responsible for country domains, such as .cn, .uk, .fr, .ca, .jp, etc. -Responsible for an organization's named hosts -Doesn't strictly belong to the DNS hierarchy -Official contact of last resort -The first server that a client requests a name from

-Maintained either by an organization or by that organization's service provider -Responsible for an organization's named hosts

When writing network applications, which of the following should be taken into consideration? Select all that apply. -Network application developers must manage all aspects of the connection, including the physical layer. -Network applications should be able to run on end systems (possibly different types of end systems) -Network applications should be able to run on network-core devices -Network applications should be able to communicate over a network

-Network applications should be able to run on end systems (possibly different types of end systems) -Network applications should be able to communicate over a network

Which of the following problems can be caused by network congestion? Select all that apply. -Packet loss -Unnecessary duplicate transmissions -Long delays -Socket buffer overload

-Packet loss -Unnecessary duplicate transmissions -Long delays

Which of the following are functions of the network layer? Select all that apply. -Video streaming -Social networking -Routing -Forwarding

-Routing -Forwarding

Which of the following techniques is used to allow networks to operate with a mix of IPv4 and IPv6 routers? Select all that apply. -NAT -Tunneling -Checksum processing -DHCP

-Tunneling

Which of the following are ways that a host can get an IP address within its network? Select all that apply. -Use DHCP (Dynamic Host Configuration Protocol) to dynamically get an :address from a server -Hard-coding by system admin in a configuration file -Petition the Elders of the Internet to allow the host to connect -Get allocated a group of addresses from its provider's address space

-Use DHCP (Dynamic Host Configuration Protocol) to dynamically get an :address from a server -Hard-coding by system admin in a configuration file

Protocol

A set of rules that guides and/or governs communication between two or more entities

Physical Layer

Bits "on the wire"; the media through which hosts are connected

Processor

Part of the management control plane; handles routing

Throughput

The rate at which bits are sent from the sender to the receiver

Input ports

Where data enters the router; receives data from link layer, looks up appropriate opposite port using forwarding table in memory

Output ports

Where data leaves the router; encapsulates data to send it to link layer and through the link

Which of the following statements about DHCP are true? Select all that apply. -DHCP stands for Dedicated Host Control Packet. -DHCP stands for Dynamic Host Configuration Protocol. -DHCP allows a network server to gain exclusive control of the host device. -DHCP allows hosts to dynamically obtain an IP address from a network server when it joins the network.

-DHCP stands for Dynamic Host Configuration Protocol. -DHCP allows hosts to dynamically obtain an IP address from a network server when it joins the network.

Which of the following statements describe TCP slow start? Select all that apply. -When connection begins, rate is increased exponentially until the first loss event. -Slow start begins with a triple duplicate ACK to initialize the connection rate. -Slow start does not increase quickly enough to be useful for modern internet usage. -Initial rate is slow, but ramps up exponentially fast.

-When connection begins, rate is increased exponentially until the first loss event. -Initial rate is slow, but ramps up exponentially fast.

Number the layers of the internet protocol stack in order from top (1) to bottom (5). Link Layer Application Layer Transport Layer Physical Layer Network Layer

1. Application Layer 2. Transport Layer 3. Network Layer 4. Link Layer 5. Physical Layer

Which of the following are transport services that an application might need? Select all that apply. Security - requiring encryption to be effective Data integrity - requiring reliable data transfer to be effective Throughput - requiring a minimum amount to be effective Timing - requiring a minimum delay to be effective

All of the above

What are the two types of HTTP messages? -Request and response -Fetch and decode -Post and sync -Require and repose

Request and response

Network Layer

Routes data from one host to another

Which of the following statements about the "match plus action" abstraction are true? Select all that apply. -"Match plus action" involves forwarding packets to any available output port, with no consideration of the destination. -"Match plus action" involves matching bits in the arriving packet, and taking the appropriate action based on that match. -"Match plus action" can be used to copy, drop, modify, or log packets. -"Match plus action" is not used because it violates the end-to-end argument.

-"Match plus action" involves matching bits in the arriving packet, and taking the appropriate action based on that match. -"Match plus action" can be used to copy, drop, modify, or log packets.

Which of the following statements apply to root-level DNS servers (as opposed to top-level DNS, authoritative DNS, or local DNS)? Select all that apply. -Maintained either by an organization or by that organization's service provider -13 logical servers worldwide -Responsible for .com, .org, .net, .edu, etc. -Responsible for country domains, such as .cn, .uk, .fr, .ca, .jp, etc. -Responsible for an organization's named hosts -Doesn't strictly belong to the DNS hierarchy -Official contact of last resort -The first server that a client requests a name from

-13 logical servers worldwide -Official contact of last resort

Which of the following statements describe a non-persistent HTTP connection (as opposed to a persistent connection). Select all that apply. -Multiple objects can be sent over the same connection before it is closed. -The server leaves the connection open after sending each response. -At most, one object is sent over the connection before it is closed. -A new connection must be established for each object requested, requiring a handshake for each new connection, resulting in 2 round-trip times (RTTs) for each referenced object. -The server closes the connection after sending each response. -Can take as little as 1 round-trip time (RTT) for all referenced objects.

-At most, one object is sent over the connection before it is closed. -A new connection must be established for each object requested, requiring a handshake for each new connection, resulting in 2 round-trip times (RTTs) for each referenced object. -The server closes the connection after sending each response.

Which of the following statements about DNS are true? Select all that apply. -DNS servers provide name resolution, connecting IP addresses to human-readable names. -DNS servers maintain Anonymous's global blacklist of clients who are never allowed to access the internet. -DNS stands for Domain Name System. -DNS stands for Do Not Service.

-DNS servers provide name resolution, connecting IP addresses to human-readable names. -DNS stands for Domain Name System.

Which of the following properties of NAT are controversial? Select all that apply. -NAT helps solve the IPv4 address shortage, but that should be left to IPv6. -NAT provides an additional layer of security. -NAT violates the end-to-end argument because it involves a network-layer device manipulating port numbers. -NAT is used extensively in home and institutional networks.

-NAT helps solve the IPv4 address shortage, but that should be left to IPv6. -NAT violates the end-to-end argument because it involves a network-layer device manipulating port numbers.

Which of the following statements about NAT are true? Select all that apply. -NAT stands for Network Address Translation. -NAT stands for Nearby Automatic Transmitter. -NAT allows all devices in a local network to share one IPv4 address from an outside point of view. -NAT is a protocol for automatically transmitting data to nearby hosts.

-NAT stands for Network Address Translation. -NAT allows all devices in a local network to share one IPv4 address from an outside point of view.

Which of the following pieces of information are used by UDP to identify the source or destination of a datagram? Select all that apply. -Destination MAC address -Source IP address -Source port number -Destination port number -Destination IP address -Source MAC address

-Source port number -Destination port number

Which of the following statements about TCP are true? Select all that apply. -TCP provides flow control and congestion control. -TCP provides means to establish connections. -TCP does not establish a connection. -TCP provides unreliable, unordered delivery. -TCP is a no-frills extension of "best-effort" IP -TCP stands for Transmission Control Protocol. -TCP stands for Tachyon Chronoton Pulse. -TCP provides reliable, in-order delivery.

-TCP provides flow control and congestion control. -TCP provides means to establish connections. -TCP stands for Transmission Control Protocol. -TCP provides reliable, in-order delivery.

Which of the following was the initial motivation behind the development of IPv6? -IPv4 does not support modern applications such as social media or video streaming. -The 32-bit IPv4 address space would be completely allocated (the world would run out of IP addresses). -IPv4 is too old to be useful. -IPv4 is too expensive to maintain.

-The 32-bit IPv4 address space would be completely allocated (the world would run out of IP addresses).

Transmission rate / Bandwidth

A measurement of the speed at which data can be passed into a link

Approximately how much of the internet uses IPv6? ~60-70% ~15-20% ~30-33% 100%

~30-33%

Which of the following descriptions below correspond to a "services" view of the Internet? Select one or more of the answers below below that are correct below that are correct. [Hint: more than one of answers below are correct]. -A collection of billions of computing devices, and packet switches interconnected by links. -A platform for building network applications. -A "network of networks". -A place I go for information, entertainment, and to communicate with people. -A collection of hardware and software components executing protocols that define the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

-A platform for building network applications. -A place I go for information, entertainment, and to communicate with people.

Which of the following statements about sockets are true? Select all that apply. -A socket serves as a "door" through which application to application communication can occur. -Two sockets, one on each side, are used to allow communication with other applications. -Only the receiving side needs a socket to communicate with another application. -Only the sending side needs a socket to communicate with another application. -Processes send and receive information through sockets.

-A socket serves as a "door" through which application to application communication can occur. -Two sockets, one on each side, are used to allow communication with other applications. -Processes send and receive information through sockets.

Which of the following statements about congestion avoidance algorithms are true? Select all that apply. -MISD (Multiplicative Increase, Subtractive Decrease) is a TCP approach for congestion control has been shown to optimize congested flow rates network-wide. -AIMD (Additive Increase, Multiplicative Decrease) is a TCP approach for congestion control has been shown to optimize congested flow rates network-wide. -CUBIC is a TCP approach for congestion control that is used by many Linux servers. -AIMD (Additive Increase, Multiplicative Decrease) is a TCP approach for congestion control that is used by many Linux servers.

-AIMD (Additive Increase, Multiplicative Decrease) is a TCP approach for congestion control has been shown to optimize congested flow rates network-wide. -CUBIC is a TCP approach for congestion control that is used by many Linux servers.

Which of the following fields are found in a TCP header? Select all that apply. -Acknowledgment number -Source MAC address -Destination port number -Length -Options -Sequence number -Source port number -Checksum -Receive window (rwnd) -Destination MAC address

-Acknowledgment number -Destination port number -Length -Options -Sequence number -Source port number -Checksum -Receive window (rwnd)

Which of the following are Quality of Service (QoS) Guarantees that can be provided by a network structure? -Bandwidth -Anonymity -Order -Affordability -Authenticity -Timing -Loss

-Bandwidth -Order -Timing -Loss

Which of the following are characteristics of congestion control? Select all that apply. -Controlled by the receiver window field (rwnd). -Controlled by the C and E bits/flags, perceived packet loss, and/or perceived packet delay. -Used to prevent a receiver from being overwhelmed with data. -Used to prevent a network from being overwhelmed with traffic.

-Controlled by the C and E bits/flags, perceived packet loss, and/or perceived packet delay. -Used to prevent a network from being overwhelmed with traffic.

Which of the following statements about cookies are true? Select all that apply. -Cookies are used to maintain state between transactions, allowing users to login to websites, view emails, and create shopping carts. -Cookies use a unique ID to allow a server to identify a client. -Cookies are stored by the server. -Cookies are stored by the client. -Cookies are only used for advertisements, and should be banned completely. -Cookies never contain identifying information about clients.

-Cookies are used to maintain state between transactions, allowing users to login to websites, view emails, and create shopping carts. -Cookies use a unique ID to allow a server to identify a client. -Cookies are stored by the client.

Which of the following pieces of information are used by TCP to identify the source or destination of a datagram? Select all that apply. -Source MAC address -Destination IP address -Source port number -Destination MAC address -Destination port number -Source IP address

-Destination IP address -Source port number -Destination port number -Source IP address

Which of the following fields are found in a UDP header? Select all that apply. -Options -Source MAC address -Acknowledgment number -Destination port number -Sequence number -Destination MAC address -Length -Source port number -Checksum -Receive window (rwnd)

-Destination port number -Length -Source port number -Checksum

Which of the following statements apply to local DNS servers (as opposed to root-level DNS, top-level DNS, or authoritative DNS)? Select all that apply. -Maintained either by an organization or by that organization's service provider -13 logical servers worldwide -Responsible for .com, .org, .net, .edu, etc. -Responsible for country domains, such as .cn, .uk, .fr, .ca, .jp, etc. -Responsible for an organization's named hosts -Doesn't strictly belong to the DNS hierarchy -Official contact of last resort -The first server that a client requests a name from

-Doesn't strictly belong to the DNS hierarchy -The first server that a client requests a name from

Which of the following are ways that a network can get the subnet part of IP address? Select all that apply. -Hard-coding by system admin in a configuration file -Use DHCP (Dynamic Host Configuration Protocol) to dynamically get an address from a server -Get allocated a group of addresses from its provider's address space -Petition the Elders of the Internet to allow the host to connect

-Get allocated a group of addresses from its provider's address space -Petition the Elders of the Internet to allow the host to connect

Which of the following statements about HTTP are true? Select all that apply. -HTTP maintains state: the server retains information about past client requests. -HTTP stands for Hyper-Text Transfer Protocol -HTTP is stateless: the server maintains no information about past client requests. -HTTP stands for How To Transport Programs

-HTTP stands for Hyper-Text Transfer Protocol -HTTP is stateless: the server maintains no information about past client requests.

Which of the following statements about middleboxes are true? Select all that apply. -Middleboxes are part of why the "thin waist" of the internet isn't so thin anymore. -Middleboxes are any intermediary box performing functions apart from normal, standard functions of an IP router on the data path between a source host and a destination host. -Middleboxes are not used because they violate the end-to-end argument. -Middleboxes cause too much complication to be useful.

-Middleboxes are part of why the "thin waist" of the internet isn't so thin anymore. -Middleboxes are any intermediary box performing functions apart from normal, standard functions of an IP router on the data path between a source host and a destination host.

Which of the following statements describe a persistent HTTP connection (as opposed to a non-persistent connection). Select all that apply. -Multiple objects can be sent over the same connection before it is closed. -The server closes the connection after sending each response. -The server leaves the connection open after sending each response. -At most, one object is sent over the connection before it is closed. -A new connection must be established for each object requested, requiring a handshake for each new connection, resulting in 2 round-trip times (RTTs) for each referenced object. -Can take as little as 1 round-trip time (RTT) for all referenced objects.

-Multiple objects can be sent over the same connection before it is closed. -The server leaves the connection open after sending each response. -Can take as little as 1 round-trip time (RTT) for all referenced objects.

Which of the following statements about network neutrality are true? Select all that apply. -Network neutrality has no political implications, and has never been regulated in the United States. -Network neutrality affects principles such as the protection of free speech and can encourage innovation and competition. -Network neutrality allows paid prioritization of internet services. -Network neutrality allows lawful content to be blocked. -Network neutrality is how an ISP should share/allocate its resources.

-Network neutrality affects principles such as the protection of free speech and can encourage innovation and competition. -Network neutrality is how an ISP should share/allocate its resources.

Which of the following characteristics apply to end-end congestion control? Select all that apply. -Violates the end-to-end argument -No explicit feedback from the network -Routers provide direct feedback to sending/receiving hosts -Congestion is inferred from observed loss or delay -Routers may indicate congestion level or explicitly set sending rate -The approached used by TCP

-No explicit feedback from the network -Congestion is inferred from observed loss or delay -The approached used by TCP

Which of the following statements apply to top-level DNS servers (as opposed to root-level DNS, authoritative DNS, or local DNS)? Select all that apply. -Maintained either by an organization or by that organization's service provider -13 logical servers worldwide -Responsible for .com, .org, .net, .edu, etc. -Responsible for country domains, such as .cn, .uk, .fr, .ca, .jp, etc. -Responsible for an organization's named hosts -Doesn't strictly belong to the DNS hierarchy -Official contact of last resort -The first server that a client requests a name from

-Responsible for .com, .org, .net, .edu, etc. -Responsible for country domains, such as .cn, .uk, .fr, .ca, .jp, etc.

Which of the following characteristics apply to network-assisted congestion control? Select all that apply. -The approached used by TCP -Routers may indicate congestion level or explicitly set sending rate -No explicit feedback from the network -Congestion is inferred from observed loss or delay -Routers provide direct feedback to sending/receiving hosts -Violates the end-to-end argument

-Routers may indicate congestion level or explicitly set sending rate -Routers provide direct feedback to sending/receiving hosts -Violates the end-to-end argument

Which of the following statements about SMTP are true? Select all that apply. -SMTP is used for email. -SMTP stands for Single Marked Transmission Program -SMTP is used for streaming video. -SMTP stands for Simple Mail Transfer Protocol

-SMTP is used for email. -SMTP stands for Simple Mail Transfer Protocol

Which of the following types of applications need to use network connectivity to function? Select all that apply. -Calculator -Social applications (Facebook, Twitter, etc.) -Text messaging applications -E-mail applications -Basic drawing applications (Paint, Sketch, etc.) -Basic word processing applications (Notepad, Notes, etc.)

-Social applications (Facebook, Twitter, etc.) -Text messaging applications -E-mail applications

When we say that the Internet is a "network of networks," we mean? Check all that apply. -The Internet is made up of a lot of identical networks that are interconnected to each other. -The Internet is made up of a lot of different networks that are interconnected to each other. -The Internet is the fastest network ever built. The Internet is made up of access networks at the edge, tier-1 networks at the core, and interconnected regional and content provider networks as well.

-The Internet is made up of a lot of different networks that are interconnected to each other. -The Internet is made up of access networks at the edge, tier-1 networks at the core, and interconnected regional and content provider networks as well.

Select the true statement below. -The adoption of IPv6 is taking so long primarily due to the cost of upgrading infrastructure to support it. -The adoption of IPv6 is taking so long primarily due to an overwhelming fear of technological improvement in the corporate world. -The adoption of IPv6 is taking so long primarily due to its slow speed compared to IPv4.

-The adoption of IPv6 is taking so long primarily due to the cost of upgrading infrastructure to support it.

Which of the following statements about the end-to-end argument are true? Select all that apply. -The end-to-end argument states that all network intelligence should be implemented at the core of the network, allowing the edges to consist of relatively simplistic devices. -The end-to-end argument states that all network intelligence should be implemented at the edges of the network, allowing the core to consist of relatively simplistic devices. -The end-to-end argument is encourages the use of middlebox technologies such as SDN, CDNs, and NAT. -The end-to-end argument is increasingly being violated by middlebox technologies such as SDN, CDNs, and NAT.

-The end-to-end argument states that all network intelligence should be implemented at the edges of the network, allowing the core to consist of relatively simplistic devices. -The end-to-end argument is increasingly being violated by middlebox technologies such as SDN, CDNs, and NAT.

Which of the characteristics below are associated with a client-server approach to structuring network applications (as opposed to a P2P approach)? -There is a server that is always on. -There is not a server that is always on. -There is a server with a well known server IP address. -A process requests service from those it contacts and will provide service to processes that contact it. -HTTP uses this application structure.

-There is a server that is always on. -There is a server with a well known server IP address. -HTTP uses this application structure.

Which of the characteristics below are associated with a P2P approach to structuring network applications (as opposed to a client-server approach)? -There is a server that is always on. -There is not a server that is always on. -There is a server with a well known server IP address. -A process requests service from those it contacts and will provide service to processes that contact it. -HTTP uses this application structure.

-There is not a server that is always on. -A process requests service from those it contacts and will provide service to processes that contact it.

Which of the following statements about UDP are true? Select all that apply. -UDP provides flow control and congestion control. -UDP provides unreliable, unordered delivery. -UDP provides reliable, in-order delivery. -UDP stands for User Datagram Protocol. -UDP is a no-frills extension of "best-effort" IP -UDP provides means to establish connections. -UDP stands for Unreliable Data Process. -UDP does not establish a connection.

-UDP provides unreliable, unordered delivery. -UDP stands for User Datagram Protocol. -UDP is a no-frills extension of "best-effort" IP -UDP does not establish a connection.

Which of the following are characteristics of flow control? Select all that apply. -Controlled by the C and E bits/flags, perceived packet loss, and/or perceived packet delay. -Used to prevent a network from being overwhelmed with traffic. -Used to prevent a receiver from being overwhelmed with data. -Controlled by the receiver window field (rwnd).

-Used to prevent a receiver from being overwhelmed with data. -Controlled by the receiver window field (rwnd).

Which of the following statements about web caches are true? Select all that apply. -Web caches cause unnecessary complication to internet communication, and are no longer used by anyone. -Web caches are also known as proxy servers. -Web caches act as both clients and servers. -Web caches can reduce response time and traffic.

-Web caches are also known as proxy servers. -Web caches act as both clients and servers. -Web caches can reduce response time and traffic.

Host

A device acting as a client and/or server, found at the edge of the network

Router

A device found at the core of the network that helps with the movement of communication traffic

Packet

A small chunk of an application-layer message

Which of the following are advantages of NAT? Select all that apply. -NAT allows a local network to change to a different ISP without changing the addresses of the devices within the network. -NAT allows hosts in the local network to change IP addresses without notifying any devices outside the network. -Only one IP address is needed from a provider ISP for all the devices connected to a router using NAT. -Devices within a local network using NAT are not directly visible to or addressable by devices outside the network.

All of the above

Which of the following types of devices need to implement network layer protocols? Select all that apply. -Routers -Servers -Clients

All of the above

Encapsulation

Taking data from the layer above, adding header fields appropriate for this layer, and then placing the data in the payload field of the "packet" for that layer

Link Layer

Transfers data between neighboring network elements

Application Layer

Transfers data from one application to another

High-speed switching fabric

Transfers data from one link to the appropriate opposite link

Transport Layer

Transfers data from one process to another

A subnet is a collection of device interfaces that can physically reach each other without passing through an intervening router. True or False

True