aco330 quiz3 notes

True or False: It is possible for two TCP segments with source port 80 to be sent by the sending host to different clients.

True

True or False: It is possible for two UDP segments to be sent from the same socket with source port 5723 at a server to two different clients.

True

True or False: On the sending side, the UDP sender will take each application-layer chunk of data written into a UDP socket and send it in a distinct UDP datagram. And then on the receiving side, UDP will deliver a segment's payload into the appropriate socket, preserving the application-defined message boundary.

True

True or False: The transport layer provides for host-to-host delivery service?

True

True or False: When computing the Internet checksum for two numbers, a single flipped bit (i.e., in just one of the two numbers) will always result in a changed checksum.

True

True or False: When multiple UDP clients send UDP segments to the same destination port number at a receiving host, those segments (from different senders) will always be directed to the same socket at the receiving host.

True

Compute the Internet checksum value for these two 16-bit words: 11110101 11010011 and 10110011 01000100 a) 01010110 11100111 b) 01101110 11010101 c) 01010110 11101000 d) 01011110 11000101

a) 01010110 11100111

True or False: When computing the Internet checksum for two numbers, a single flipped bit in each of the two numbers will always result in a changed checksum.

False

True or False: When multiple TCP clients send TCP segments to the same destination port number at a receiving host, those segments (from different senders) will always be directed to the same socket at the receiving host.

False

True or false: Consider an HTTP Web server using persistent connections. Suppose the server spawns a separate process for each client that connects to the server. Then each of these spawned processes will have different server port numbers.

False

Compute the Internet checksum value for these two 16-bit words: 01000001 11000100 and 00100000 00101011 a) 10011110 00010000 b) 10011110 00010001 c) 10011110 00001111 d) 01101110 11010101

a) 10011110 00010000

The destination IP address of the IP datagram containing the UDP segment (B) sent in reply is: Answers: 60.54.75.24, 128.119.40.186, 3546, 24, 10.0.0.1, 80, 4829 Questions: a) The source port number of the UDP segment (B) sent in reply is: b) The source IP address of the IP datagram containing the UDP segment (B) sent in reply is: c) The destination port number of the UDP segment (B) sent in reply is: d) The destination IP address of the IP datagram containing the UDP segment (B) sent in reply is:

a) 3546 b) 128.119.40.186 c) 4829 d) 60.54.75.24

Check all of the services below that are provided by the TCP protocol. a) A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender. b) In-order data delivery c) A congestion control service to ensure that multiple senders do not overload network links. d) A message abstraction, that preserves boundaries between message data sent in different socket send calls at the sender. e) A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers. f) A guarantee on the maximum amount of time needed to deliver data from sender to receiver. g) A guarantee on the minimum amount of throughput that will be provided between sender and receiver. h) Reliable data delivery

a) A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender. b) In-order data delivery c) A congestion control service to ensure that multiple senders do not overload network links. e) A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers. h) Reliable data delivery

Answer list: Chunk, Video frame, Manifest, Enter deep, Over The Top (OTT), DASH Organize: a) A unit of video, each of which may be encoded at multiple different rates, stored in different files. b) A file containing the location and encoding rate of files corresponding to video segments in a video. c) An approach that allows a client to adapt the encoding rate of retrieved video to network congestion conditions. d) A CDN approach that stores content in access networks, close to clients.

a) Chunk b) Manifest c) DASH d) Enter Deep

True or False: The network layer's best-effort delivery service means that IP makes its "best effort" to deliver segments between communicating hosts, but it makes no guarantees. In particular, it does not guarantee segment delivery, it does not guarantee orderly delivery of segments, and it does not guarantee the integrity of the data in the segments. a) Correct! The network layer's best effort service doesn't really provide much service at all, does it? b) Nope. The network layer's best effort service doesn't really provide much service at all, does it?

a) Correct! The network layer's best effort service doesn't really provide much service at all, does it?

Which of the fields below are in a UDP segment header? [Hint: note the use of the word "header" in this question statement.] a) Length (of UDP header plus payload) b) Internet checksum c) Data (payload) d) Upper layer protocol e) Source port number f) Destination port number g) Source IP address h) Sequence number

a) Length (of UDP header plus payload) b) Internet checksum e) Source port number f) Destination port number

What is meant by transport-layer multiplexing? a) Taking data from one socket (one of possibly many sockets), encapsulating a data chuck with header information - thereby creating a transport layer segment - and eventually passing this segment to the network layer. b) Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket. c) Taking data from multiple sockets, all associated with the same destination IP address, adding destination port numbers to each piece of data, and then concatenating these to form a transport-layer segment, and eventually passing this segment to the network layer. d) Receiving a transport-layer segment from the network layer, extracting the payload, determining the destination IP address for the data, and then passing the segment and the IP address back down to the network layer.

a) Taking data from one socket (one of possibly many sockets), encapsulating a data chuck with header information - thereby creating a transport layer segment - and eventually passing this segment to the network layer.

Over what set of bytes is the checksum field in the UDP header computed over? a) The entire UDP segment, except the checksum field itself, and the IP sender and receive address fields b) Just the UDP header but not the payload. c) The entire UDP segment, except the checksum field itself.

a) The entire UDP segment, except the checksum field itself, and the IP sender and receive address fields

When a UDP segment arrives to a host, in order to direct the segment to the appropriate socket, the OS uses a) the destination port number b) the source IP address c) the source port number d) all of the above

a) the destination port number

Which of the following statements are true about a checksum? a) A checksum is computed at a sender by considering each byte within a packet as a number, and then adding these numbers (each number representing a bytes) together to compute a sum (which is known as a checksum). b) The receiver of a packet with a checksum field will add up the received bytes, just as the sender did, and compare this locally-computed checksum with the checksum value in the packet header. If these two values are different then the receiverknows that one of the bits in the received packet has been changed during transmission from sender to receiver. c) The sender-computed checksum value is often included in a checksum field within a packet header. d) The receiver of a packet with a checksum will add up the received bytes, just as the sender did, and compare this locally-computed checksum with the checksum value in the packet header. If these two values are the same then the receiver knowsthat all of the bits in the received packet are correct, i.e., that no bits have been changed during transmission from sender to receiver.

all except d

What is meant by transport-layer demultiplexing? a) Taking data from one socket (one of possibly many sockets), encapsulating a data chuck with header information - thereby creating a transport layer segment - and eventually passing this segment to the network layer. b) Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket. c) Taking data from multiple sockets, all associated with the same destination IP address, adding destination port numbers to each piece of data, and then concatenating these to form a transport-layer segment, and eventually passing this segment to the network layer. d) Receiving a transport-layer segment from the network layer, extracting the payload, determining the destination IP address for the data, and then passing the segment and the IP address back down to the network layer.

b) Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket.

Manifest file. What is the purpose of a manifest file in a streaming multimedia setting? a) Allows a video service to log the video and the server from which a client streams a video. b) To let a client know where it can retrieve different video segments, encoded at different rates c) To allow a client to reserve bandwidth along a path from a server to that client, so the client can view a stream video without impairment. d) To let a OTT (Over-the-top) video server know the video that the client wants to view.

b) To let a client know where it can retrieve different video segments, encoded at different rates

In DASH (Dynamic, Adaptive Streaming over HTTP), a server divides a video file into chunks that ... (pick best completion from below) a) allow premium users to avoid watching chunks that contain commercials. b) are stored, each encoded at multiple rates (video quality). The client plays the video chunk-by-chunk, with each chunk requested at encoding rate that fits the available bandwidth at the time. c) are download smallest-chunk-first in order to maximize the number of chunks received. d) are downloaded just before their playout time. Chunking is used primarily because a viewer may jump around (e.g., fast forward) in a video. ... are stored, each encoded at multiple rates (video quality). The client receives multiple video chunks (encoded at different rates) and plays out the chunks that best fit the screen size

b) are stored, each encoded at multiple rates (video quality). The client plays the video chunk-by-chunk, with each chunk requested at encoding rate that fits the available bandwidth at the time.

Why is the UDP header length field needed? a) (a) and (b) above b) To make the header and even number of bytes c) Because the payload section can be of variable length, and this lets UDP know where the segment ends. d) Because this field is needed in TCP as well.

c) Because the payload section can be of variable length, and this lets UDP know where the segment ends.

What approach is taken by a CDN to stream content to hundreds of thousands of simultaneous users? a) Serve video from a single central "mega-server" with ultra-high-speed network connectivity, and high-speed storage. b) Allow client devices to send requested content to each other, in order to offload the CDN infrastructure. c) Store/serve multiple copies of videos at multiple geographically distributed sites. d) Proactively push videos to a client device before they're requested, using machine learning to predict requested videos.

c) Store/serve multiple copies of videos at multiple geographically distributed sites.

Where is transport-layer functionality primarily implemented? a) Transport layer functions are implemented primarily at each end of a physical link connecting one host/router/switch to another one host/router/switch. b) Transport layer functions are implemented primarily at the routers and switches in the network. c) Transport layer functions are implemented primarily at the hosts at the "edge" of the network.

c) Transport layer functions are implemented primarily at the hosts at the "edge" of the network.

Check all of the services below that are provided by the UDP protocol. a) A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender. b) In-order data delivery c) A congestion control service to ensure that multiple senders do not overload network links. d) A message abstraction, that preserves boundaries between message data sent in different socket send calls at the sender. e) A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers. f) A guarantee on the maximum amount of time needed to deliver data from sender to receiver. g) A guarantee on the minimum amount of throughput that will be provided between sender and receiver. f) Reliable data delivery

d) A message abstraction, that preserves boundaries between message data sent in different socket send calls at the sender.

When a TCP segment arrives to a host, the socket to which the segment is directed depends on a) the destination port number b) the source port number c) the source IP address of the datagram that encapsulated the segment d) all of the above

d) all of the above

UDP has which of the following characteristics: a) three-way hand shake for connection establishment b)connection state at the server c) regulated send rate d) none of the above

d) none of the above