BIT 3554 Exam 1 KC

Routing versus forwarding. Choose one the following two definitions that makes the correct distinction between routing versus forwarding. a. Forwarding is the local action of moving arriving packets from router's input link to appropriate router output link, while routing is the global action of determining the source-destination paths taken by packets. b. Routing is the local action of moving arriving packets from router's input link to appropriate router output link, while forwarding is the global action of determining the source-destination paths taken by packets.

Forwarding is the local action of moving arriving packets from router's input link to appropriate router output link, while routing is the global action of determining the source-destination paths taken by packets.

What protocol (or protocols) constitutes the "thin waist" of the Internet protocol stack? Check all that apply. HTTP TCP IP Ethernet DNS WiFi

IP

True or False: with TCP's flow control mechanism, where the receiver tells the sender how much free buffer space it has (and the sender always limits the amount of outstanding, unACKed, in-flight data to less than this amount), it is not possible for the sender to send more data than the receiver has room to buffer. True False

True

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 False

True; Recall that two different processes may have different sockets, both associated with the same local port number (say 80, for HTTP) on a host.  But, if there are two sockets with the same local port number, how is it that when segments arrive for that host, that data is demultiplexed to the correct port?   Anwser: because TCP demultiplexing happens on the basis of four values (source and destination port numbers, and IP addresses) rather than just on the basis of the destination port number, as is done for UDP.

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 False

True; UDP demultiplexing happens solely on the basis of destination port number. Thus, segments with the same destination port number at a host will have their data demultiplexed to the same socket.

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 False

True; Your answer is correct. Recall that the application-layer program explicitly specifies the destination host IP address and port number when sending into a UDP socket, and that a single UDP socket (with a given source port number) can therefore be used to send to multiple UDP clients.

Computing Packet Transmission Delay(1). Suppose a packet is L = 1500 bytes long (one byte = 8 bits), and link transmits at R = 1 Gbps (i.e., a link can transmit bits 1,000,000,000 bits per second). *image 2* What is the transmission delay for this packet? .000012 secs .00012 secs .0000015 secs .0015 secs 666,666 secs

.000012

4.2-7a.Packet scheduling. Consider the pattern of red and green packet arrivals to a router's output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under FCFS scheduling. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7 6 5 4 3 2 1). *image 8*

1 2 3 4 5 6 7

What is a protocol? Which of the following human scenarios involve a protocol (recall: "Protocols define the format, order of messages sent and received among network entities, and actions taken on message transmission, receipt")? 1. One person asking, and getting, the time to/from another person. 2. A person reading a book. 3. A person sleeping. 4. Two people introducing themselves to each other. 5. A student raising her/his hand to ask a really insightful question, followed by the teaching acknowledging the student, listening carefully to the question, and responding with a clear, insightful answer. And then thanking the student for the question, since teachers love to get questions.

1, 4, 5

Match the description of each component of packet delay to its name in the pull down list. 1. Time needed to perform an integrity check, lookup packet information in a local table and move the packet from an input link to an output link in a router. 2. Time spent waiting in packet buffers for link transmission. 3. Time spent transmitting packets bits into the link. 4. Time need for bits to physically propagate through the transmission medium from end one of a link to the other.

1. Processing delay 2. Queueing delay 3. Transmission delay 4. Propagation delay

Packet switching versus circuit switching (2). Which of the characteristics below are associated with the technique of circuit switching? 1. Reserves resources needed for a call from source to destination. 2. Resources are used on demand, not reserved in advance. 3. Data may be queued before being transmitted due to other user's data that's also queueing for transmission. 4. Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM) are two approaches for implementing this technique. 5. Congestion loss and variable end-end delays are possible with this technique. 6. This technique is used in the Internet. 7. This technique was the basis for the telephone call switching during the 20th century and into the beginning of this current century.

1, 4, 7

What is the value of caching in the local DNS name server? Check all that apply. 1. DNS caching provides for faster replies, if the reply to the query is found in the cache. 2. DNS caching results in less load elsewhere in DNS, when the reply to a query is found in the local cache. 3. DNS caching provides prioritized access to the root servers, since the DNS request is from a local DNS cache. 4. DNS caching provides the ability to serve as authoritative name server for multiple organizations.

1,2

Which of the following statements is true regarding an IP address? (Zero, one or more of the following statements is true). 1. An IP address is associated with an interface. 2. If a host has more than one interface, then it has more that one IP address at which it can be reached. 3. If a router has more than one interface, then it has more that one IP address at which it can be reached. 4. It is not necessary for a device using the IP protocol to actually have an IP address associated with it.

1,2,3

What is meant by an IP subnet? (Check zero, one or more of the following characteristics of an IP subnet) 1. A set of device interfaces that can physically reach each other without passing through an intervening router. 2.A set of devices that always have a common first 16 bits in their IP address. 3. A set of devices that have a common set of leading high order bits in their IP address. 4. A set of devices all manufactured by the same equipment maker/vendor.

1,3

Which of the characteristics below are associated with a client-server approach to structuring network applications (as opposed to a P2P approach)? 1. There is a server that is always on. 2. There is not a server that is always on. 3. There is a server with a well known server IP address. 4. A process requests service from those it contacts and will provide service to processes that contact it. 5. HTTP uses this application structure.

1,3,5

In DASH (Dynamic, Adaptive Streaming over HTTP), a server divides a video file into chunks that ... (pick best completion from below) 1. ... 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. 2. ... are download smallest-chunk-first in order to maximize the number of chunks received. 3. ... 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. 4. ... are downloaded just before their playout time. Chunking is used primarily because a viewer may jump around (e.g., fast forward) in a video. 5. ... allow premium users to avoid watching chunks that contain commercials.

1. ... 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.

Which of the following fields occur ONLY in the IPv6 datagram header (i.e., appear in the IPv6 header but not in the IPv4 header)? Check all that apply. 1. 128-bit source and destination IP addresses. 2. The IP version number field. 3. The time-to-live (or hop limit) field. 4. The header checksum field. 5. The flow label field. 6. The header length field. 7. The options field. 8. The upper layer protocol (or next header) field.

1. 128-bit source and destination IP addresses. 5. The flow label field.

What is the Internet? Which of the following descriptions below correspond to a "nuts-and-bolts" view of the Internet? 1. A collection of billions of computing devices, and packet switches interconnected by links. 2. A platform for building network applications. 3. A "network of networks". 4. A place I go for information, entertainment, and to communicate with people. 5. 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.

1. A collection of billions of computing devices, and packet switches interconnected by links. 3. A "network of networks". 5. 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.

What information does the type "A" resource record hold in the DNS database? Check all that apply. 1. A hostname and an IP address. 2. A domain name and the name of the authoritative name server for that domain. 3. An alias name and a true name for a server. 4. A name and the name of the SMTP server associated with that name.

1. A hostname and an IP address.

Which of the following statements about pipelining are true? One or more statements may be true. 1. A pipelined sender can have transmitted multiple packets for which the sender has yet to receive an ACK from the receiver. 2. With pipelining, a receiver will have to send fewer acknowledgments as the degree of pipelining increases 3. With pipelining, a packet is only retransmitted if that packet, or its ACK, has been lost. 4. With a pipelined sender, there may be transmitted packets "in flight" - propagating through the channel - packets that the sender has sent but that the receiver has not yet received.

1. A pipelined sender can have transmitted multiple packets for which the sender has yet to receive an ACK from the receiver. 4. With a pipelined sender, there may be transmitted packets "in flight" - propagating through the channel - packets that the sender has sent but that the receiver has not yet received.

Match the function of a layer in the Internet protocol stack to its its name in the pulldown menu. 1. Protocols that are part of a distributed network application. 2. Transfer of data between one process and another process (typically on different hosts). 3. Delivery of datagrams from a source host to a destination host (typically). 4. Transfer of data between neighboring network devices. 5. Transfer of a bit into and out of a transmission media.

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

What are advantages of implementing transport-layer functionality in QUIC at the application layer? Select all that apply. 1. As an application-layer protocol, QUIC can be updated/modified at "app frequency" rather than at the frequency of operating system updates. 2. QUIC's performance can be better optimized at the application-layer, so it will have better performance than if these functions were implemented in the operating system. 3. QUIC performs both congestion control and error recovery different from TCP, leveraging all of the knowledge that has built up since TCP was first standardized, and therefore has better performance than TCP. 4. QUIC can establish all connection parameters (security, reliability, flow and congestion control)in just one handshake rather than separately in two.

1. As an application-layer protocol, QUIC can be updated/modified at "app frequency" rather than at the frequency of operating system updates. 4. QUIC can establish all connection parameters (security, reliability, flow and congestion control)in just one handshake rather than separately in two.

DNS functions. Match the function of a server to a given type of DNS server in the DNS server hierarchy. 1. Provides authoritative hostname to IP mappings for organization's named hosts. 2. Replies to DNS query by local host, by contacting other DNS servers to answer the query. 3. Responsible for a domain (e.g., *.com, *.edu); knows how to contact authoritative name servers. 4. Highest level of the DNS hierarchy, knows how to reach servers responsible for a given domain (e.g., *.com, *.edu).

1. Authoritative DNS server 2. Local DNS server 3. Top Level Domain (TLD) servers 4. DNS root servers

Match the definition/function of an element or approach in a networked streaming video system, with its name. 1. A unit of video, each of which may be encoded at multiple different rates, stored in different files. 2. A file containing the location and encoding rate of files corresponding to video segments in a video. 3. An approach that allows a client to adapt the encoding rate of retrieved video to network congestion conditions. 4. A CDN approach that stores content in access networks, close to clients.

1. Chunk 2. Manifest 3. DASH 4. Enter deep

Which one of the following operations is not performed by NAT.? 1. Generating ACKs back to the TCP sender and then taking responsibility for reliably delivery the segment to its destination, possibly using a non-TCP reliable data transfer protocol. 2. On an outgoing datagram, changing the transport-layer port number of the transport-layer segment inside a datagram received from the LAN side of the NAT. 3. On an incoming datagram from the public Internet side of a NAT, changing the destination IP address of a datagram to a new destination IP address that is looked up in the NAT table, and (possibly after other actions), sending that IP datagram on to the LAN side of the NAT. 4. On an outgoing datagram, changing the source IP address of a datagram received from the LAN side of the NAT

1. Generating ACKs back to the TCP sender and then taking responsibility for reliably delivery the segment to its destination, possibly using a non-TCP reliable data transfer protocol.

Which of the fields below are in a UDP segment header? [Hint: note the use of the word "header" in this question statement.] 1. Internet checksum 2. Source IP address 3. Source port number 4. Destination port number 5. Upper layer protocol 6. Sequence number 7. Length (of UDP header plus payload) 8. Data (payload)

1. Internet checksum 3. Source port number 4. Destination port number 7. Length (of UDP header plus payload)

Consider the figure below, showing a link-layer frame heading from a host to a router. There are three header fields shown. Match the name of a header with a header label shown in the figure. *image 5* 1. Header H1 2. Header H2 3. Header H3

1. Link layer 2. Network Layer 3. Transport layer

For each of the actions below, select those actions below that are primarily in the network-layer data plane. The other actions that you don't select below then correspond to control-plane actions. 1. Looking up address bits in an arriving datagram header in the forwarding table. 2. Computing the contents of the forwarding table. 3. Moving an arriving datagram from a router's input port to output port 4. Monitoring and managing the configuration and performance of a network device. 5. Dropping a datagram due to a congested (full) output buffer.

1. Looking up address bits in an arriving datagram header in the forwarding table. 3. Moving an arriving datagram from a router's input port to output port 5. Dropping a datagram due to a congested (full) output buffer.

Match the name of an Internet layer with unit of data that is exchanged among protocol entities at that layer, using the pulldown menu. 1. Application layer 2. Transport layer 3. Network layer 4. Link layer 5. Physical layer

1. Message 2. Segment 3. Datagram 4. Frame 5. Bit

Consider the purposes/goals/use of different reliable data transfer protocol mechanisms. For the given purpose/goal/use match it to the RDT mechanism that is used to implement the given purpose/goal/use. 1. Lets the sender know that a packet was NOT received correctly at the receiver. 2. Used by sender or receiver to detect bits flipped during a packet's transmission. 3. Allows for duplicate detection at receiver. 4. Lets the sender know that a packet was received correctly at the receiver. 5. Allows the receiver to eventually receive a packet that was corrupted or lost in an earlier transmission.

1. NAK 2. Checksum 3. Sequence numbers 4. ACK 5. Retransmission

What is meant by transport-layer demultiplexing? 1. Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket. 2. 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. 3. 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. 4. 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.

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

Check all of the services below that are provided by the TCP protocol. 1. Reliable data delivery. 2. In-order data delivery 3. A guarantee on the maximum amount of time needed to deliver data from sender to receiver. 4. A congestion control service to ensure that multiple senders do not overload network links. 5. A guarantee on the minimum amount of throughput that will be provided between sender and receiver. 6. A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers. 7. A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender. 8. A message abstraction, that preserves boundaries between message data sent in different socket send calls at the sender.

1. Reliable data delivery. 2. In-order data delivery 4. A congestion control service to ensure that multiple senders do not overload network links. 6. A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers. 7. A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender.

Match the functionality of a protocol with the name of a the email protocol (if any) that implements that functionality. 1. Pushes email from a mail client to a mail server. 2. Pulls mail from one mail server to another mail server. 3. Pulls email to a mail client from a mail server.

1. SMTP 2. Neither SMTP or IMAP 3. IMAP

TCP connection management. Match the description of a TCP connection management message with the name of the message used to accomplish that function. 1. A message from client to server initiating a connection request. 2. A message from server to client ACKing receipt of a SYN message and indicating the willingness of the server to establish a TCP connection with the client. 3. A message indicating that the sending side is initiating the protocol to terminate a connection. 4. A message sent in response to a request to terminate a connection, ACKing that the side receiving this message is also willing to terminate the connection 5. A general purpose error message used during connection set up or tear down to let the other side know that an error has occurred, and that the referenced connection should be shut down.

1. SYN mesage 2. SYNACK message 3. FIN message 4. FINACK message 5. RESET message

For the given function of a field in the TCP segment, select the name of that field from the pull-down list. 1. This field contains the port number associated with the sending socket for this TCP segment. 2. This field contains application data that was written into a socket by the sender of this TCP segment. 3. This field contains the index in the sender-to-receiver byte stream of the first byte of that data in the payload carried in this segment. 4. This field contains the index in the byte stream of the next in-order byte expected at the receiver 5. If set, this segment cumulatively ACKs all data bytes up to, but not including, the byte index in the ACK value field of this segment. 6. This field contains the number of available bytes in the TCP receiver's buffer. 7. This field contains the Internet checksum of the TCP segment and selected fields in the IP datagram header. 8. This field contains the number of bytes in the TCP header.

1. Source port number 2. Data (or payload). 3. Sequence number 4. ACK number field 5. ACK bit 6. Receiver advertised window 7. Checksum 8. Header length field

Check all of the statements below about where (in the network) the network layer is implemented that are true. 1. The network layer is implemented in hosts at the network's edge. 2. The network layer is implemented in routers in the network core. 3. The network layer is implemented in Ethernet switches in a local area network. 4. The network layer is implemented in wired Internet-connected devices but not wireless Internet-connected devices.

1. The network layer is implemented in hosts at the network's edge. 2. The network layer is implemented in routers in the network core.

Where is transport-layer functionality primarily implemented? 1. Transport layer functions are implemented primarily at the hosts at the "edge" of the network. 2. Transport layer functions are implemented primarily at the routers and switches in the network. 3. Transport layer functions are implemented primarily at each end of a physical link connecting one host/router/switch to another one host/router/switch.

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

Access network per-subscriber speeds. Match the access network with the approximate speeds that a subscriber might experience. (Note: if you look these up, do so in the 8E textbook or the slides, or video -- since link access speeds are always increasing over the years). 1. Ethernet 2. 4G cellular LTE 3. 802.11 Wifi 4. Cable access network 5. Digital Subscriber Line

1. Wired. Up to 100's Gbps per link 2. Wireless. Up to 10's Mbps per device 3. Wireless. 10's to 100's of Mbps per device 4. Wired. Up to 10's to 100's of Mbps downstream per user 5. Wired. Up to 10's of Mbps downstream per user

Use the pulldown menu to match a congestion control approach to how the sender detects congestion. 1. The sender infers segment loss from the absence of an ACK from the receiver. 2. Bits are set at a congested router in a sender-to-receiver datagram, and bits are in the returned to the sender in a receiver-to sender ACK, to indicate congestion to the sender. 3. The sender measures RTTs and uses the current RTT measurement to infer the level of congestion.

1. end-end 2. network-assisted 3. delay-based

What is the maximum throughput achievable between sender and receiver in the scenario shown below? *image 3* 1.5 Mbps 10 Mbps 11.5 Mbps

1.5 Mbps

How is the sending rate typically regulated in a TCP implementation? 1. By using the retransmission timeout timer and counting the number of bytes sent since the last timeout to compute the sending rate since that last timeout, and then making sure its sending rate never exceed the rate set by AIMD. 2. By keeping a window of size cwnd over the sequence number space, and making sure that no more than cwnd bytes of data are outstanding (i.e, unACKnowledged). The size of cwnd is regulated by AIMD.

2

Packet switching versus circuit switching (1). Which of the characteristics below are associated with the technique of packet switching? 1. Reserves resources needed for a call from source to destination. 2. Resources are used on demand, not reserved in advance. 3. Data may be queued before being transmitted due to other user's data that's also queueing for transmission. 4. Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM) are two approaches for implementing this technique. 5. Congestion loss and variable end-end delays are possible with this technique. 6. This technique is used in the Internet. 7. This technique was the basis for the telephone call switching during the 20th century and into the beginning of this current century.

2, 3, 5, 6

What is the Internet (2)? Which of the following descriptions below correspond to a "services" view of the Internet? 1. A collection of billions of computing devices, and packet switches interconnected by links. 2. A platform for building network applications. 3. A "network of networks". 4. A place I go for information, entertainment, and to communicate with people. 5. 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.

2, 4

Which of the characteristics below are associated with a P2P approach to structuring network applications (as opposed to a client-server approach)? 1. There is a server that is always on. 2. There is not a server that is always on. 3. There is a server with a well known server IP address. 4. A process requests service from those it contacts and will provide service to processes that contact it. 5. HTTP uses this application structure.

2,4

What information does the type "NS" resource record hold in the DNS database? Check all that apply. 1. A hostname and an IP address. 2. A domain name and the name of the authoritative name server for that domain. 3. An alias name and a true name for a server. 4. A name and the name of the SMTP server associated with that name.

2. A domain name and the name of the authoritative name server for that domain.

What is the role of an authoritative name server in the DNS? (Check all that apply) 1. It is a local (to the querying host) server that caches name-to-IP address translation pairs, so it can answer authoritatively and can do so quickly. 2. It provides the definitive answer to the query with respect to a name in the authoritative name server's domain. 3. It provides the IP address of the DNS server that can provide the definitive answer to the query. 4. It provides a list of TLD servers that can be queried to find the IP address of the DNS server that can provide the definitive answer to this query.

2. It provides the definitive answer to the query with respect to a name in the authoritative name server's domain.

What is meant by saying that DHCP is a "plug and play" protocol? 1. The host needs to "plug" (by wire or wirelessly) into the local network in order to access ("play" in) the Internet 2. No manual configuration is needed for the host to join the network. 3. The network provides an Ethernet jack for a host's Ethernet adapter.

2. No manual configuration is needed for the host to join the network.

HTTP/3: QUIC connection establishment. How many RTTs are needed to establish an HTTP/3 connection (i.e., before data can begin to flow between client and server) using QUIC? 1. Two RTTs - one to establish reliability and congestion control parameters, and one to establish TLS security parameters. 2. One RTT. Reliability, congestion control, flow control, and security parameters are established in the first two parts of the setup handshake, which takes one RTT. 3. Zero RTTs. HTTP is stateless.

2. One RTT. Reliability, congestion control, flow control, and security parameters are established in the first two parts of the setup handshake, which takes one RTT.

What approach is taken by a CDN to stream content to hundreds of thousands of simultaneous users? 1. Serve video from a single central "mega-server" with ultra-high-speed network connectivity, and high-speed storage. 2. Store/serve multiple copies of videos at multiple geographically distributed sites. 3. Proactively push videos to a client device before they're requested, using machine learning to predict requested videos. 4. Allow client devices to send requested content to each other, in order to offload the CDN infrastructure.

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

What is the purpose of the Dynamic Host Configuration Protocol? 1. To configure the interface speed to be used, for hardware like Ethernet, which can be used at different speeds. 2. To obtain an IP address for a host attaching to an IP network. 3. To get the 48-bit link-layer MAC address associated with a network-layer IP address. 4. To configure the set of available open ports (and hence well-known services) for a server.

2. To obtain an IP address for a host attaching to an IP network.

What is meant by a cumulative acknowledgment, ACK(n)? 1. A cumulative ACK(n) allows the receiver to let the sender know that it has not yet received an ACK for packet with sequence number n. 2. A cumulative ACK(n) allows the receiver to let the sender know that it has not received any packets with a new sequence number since the last cumulative ACK(n) was sent. 3. A cumulative ACK(n) acks all packets with a sequence number up to and including n as being received.

3. A cumulative ACK(n) acks all packets with a sequence number up to and including n as being received.

What is meant by transport-layer multiplexing? 1. Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket. 2. 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. 3. 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. 4. 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.

3. 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.

What is the purpose of a manifest file in a streaming multimedia setting? 1. Allows a video service to log the video and the server from which a client streams a video. 2. 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. 3. To let a client know where it can retrieve different video segments, encoded at different rates 4. To let a OTT (Over-the-top) video server know the video that the client wants to view.

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

Check all of the phrases below that state a true property of a local DNS server. 1. The local DNS server record for a remote host is sometimes different from that of the authoritative server for that host. 2. The local DNS server is only contacted by a local host if that local host is unable to resolve a name via iterative or recursive queries into the DNS hierarchy. 3. The local DNS server holds hostname-to-IP translation records, but not other DNS records such as MX records. 4. The local DNS server can decrease the name-to-IP-address resolution time experienced by a querying local host over the case when a DNS is resolved via querying into the DNS hierarchy.

4. The local DNS server can decrease the name-to-IP-address resolution time experienced by a querying local host over the case when a DNS is resolved via querying into the DNS hierarchy.

Which of the following quality-of-service guarantees are part of the Internet's best-effort service model? Check all that apply. 1. Guaranteed delivery from sending host to receiving host. 2. Guaranteed delivery time from sending host to receiving host. 3. In-order datagram payload delivery to the transport layer of those datagrams arriving to the receiving host. 4. A guaranteed minimum bandwidth is provided to a source-to-destination flow of packets 5. None of the other services listed here are part of the best-effort service model. Evidently, best-effort service really means no guarantees at all!

5. None of the other services listed here are part of the best-effort service model. Evidently, best-effort service really means no guarantees at all!

Consider the scenario shown below, with four different servers connected to four different clients over four three-hop paths. The four pairs share a common middle hop with a transmission capacity of R = 300 Mbps. The four links from the servers to the shared link have a transmission capacity of RS = 50 Mbps. Each of the four links from the shared middle link to a client has a transmission capacity of RC = 90 Mbps. What is the maximum achievable end-end throughput (an integer value, in Mbps) for each of four client-to-server pairs, assuming that the middle link is fairly shared (divides its transmission rate equally) and all servers are trying to send at their maximum rate? Your answer: [A] Mbps *image 4*

50 Mbps

How many calls can be carried? Consider the circuit-switched network shown in the figure below, with four circuit switches A, B, C, and D. Suppose there are 20 circuits between A and B, 19 circuits between B and C, 15 circuits between C and D, and 16 circuits between D and A. *image 1* What is the maximum number of connections that can be ongoing in the network at any one time? 70 20 16 39 31

70

Consider the three subnets in the diagram below. *image 7* What is the maximum # of interfaces in the 223.1.3/29 network? 8 128 There's no a priori limit on the number of interfaces in this subnet. Three hosts, as shown in the figure. 2**32

8

Which of the following network devices can be thought of as a "middlebox"? Check all that apply. IP router Network Address Translation box WiFi base station HTTP load balancer HTTP cache SDN controller

NAT box HTTP load balancer HTTP cache

Which of the following are advantages of using a web cache? Select one or more answers. a. Caching generally provides for a faster page load time at the client, if the web cache is in the client's institutional network, because the page is loaded from the nearby cache rather than from the distant server. b. Caching allows an origin server to more carefully track which clients are requesting and receiving which web objects. c. Overall, caching requires fewer devices/hosts to satisfy a web request, thus saving on server/cache costs. d. Caching uses less bandwidth coming into an institutional network where the client is located, if the cache is also located in that institutional network.

a,d

What is an HTTP cookie used for? a. A cookie is a code used by a server, carried on a client's HTTP request, to access information the server had earlier stored about an earlier interaction with this Web browser. [Think about the distinction between a browser and a person.] b. A cookie is used to spoof client identity to an HTTP server. c. A cookies is a code used by a server, carried on a client's HTTP request, to access information the server had earlier stored about an earlier interaction with this person. [Think about the distinction between a browser and a person.] d. A cookie is a code used by a client to authenticate a person's identity to an HTTP server. e. Like dessert, cookies are used at the end of a transaction, to indicate the end of the transaction.

a. A cookie is a code used by a server, carried on a client's HTTP request, to access information the server had earlier stored about an earlier interaction with this Web browser. [Think about the distinction between a browser and a person.]

The transport layer sits on top of the network layer, and provides its services using the services provided to it by the network layer. Thus it's important that we know what is meant by the network layer's "best effort" delivery service. 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?

What is the purpose of the HTTP GET message? a. The HTTP GET request message is used by a web client to request a web server to send the requested object from the server to the client. b. The HTTP GET request message is used by a web client to post an object on a web server. c. The HTTP GET request message is sent by a web server to a web client to get the identity of the web client. d. The HTTP GET request message is sent by a web server to a web client to get the next request from the web client.

a. The HTTP GET request message is used by a web client to request a web server to send the requested object from the server to the client.

4.2-4. Longest prefix matching. Consider the following forwarding table below. Indicate the output to link interface to which a datagram with the destination addresses below will be forwarded under longest prefix matching. (Note: The list of addresses is ordered below. If two addresses map to the same output link interface, map the first of these two addresses to the first instance of that link interface.) *image 7* A. 11001000 00010111 00010010 B. 11001000 00010111 00011000 00001101 C. 11001000 00010111 00011001 11001101 D. 10001000 11100000 00011000 00001101 E. 11001000 00010111 00011000 11001111 F. 11001000 00010111 00010001 01010101 G. 11001000 00010111 00011101 01101101

a. This is the first destination address in the list that maps to output port 0. b. This is the first destination address in the list that maps to output port 1. c. This is the first destination address in the list that maps to output port 2. d. This is the first destination address in the list that maps to output port 3. e. This is the second destination address in the list that maps to output port 1. f. This is the second destination address in the list that maps to output port 0. g. This is the second destination address in the list that maps to output port 2.

Suppose a client is sending an HTTP GET request message to a web server, gaia.cs.umass.edu. Suppose the client-to-server HTTP GET message is the following (same as in previous problem): GET /kurose_ross_sandbox/interactive/quotation2.htm HTTP/1.1Host: gaia.cs.umass.eduAccept: text/plain, text/html, text/xml, image/jpeg, image/gif, audio/mpeg, audio/mp4, video/wmv, video/mp4,Accept-Language: en-us, en-gb;q=0.1, en;q=0.7, fr, fr-ch, da, de, fiIf-Modified-Since: Wed, 09 Sep 2020 16:06:01 -0700User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11 Does the client have a cached copy of the object being requested? a. Yes, because this is a conditional GET, as evidenced by the If-Modified-Since field. b. Yes, because HTTP 1.1 is being used. c. No, because a client would not request an object if it had that object in its cache. d. There's not enough information in the header to answer this question.

a. Yes, because this is a conditional GET, as evidenced by the If-Modified-Since field.

Suppose a client is sending an HTTP GET message to a web server, gaia.cs.umass.edu. Suppose the client-to-server HTTP GET message is the following: GET /kurose_ross_sandbox/interactive/quotation2.htm HTTP/1.1Host: gaia.cs.umass.eduAccept: text/plain, text/html, text/xml, image/jpeg, image/gif, audio/mpeg, audio/mp4, video/wmv, video/mp4,Accept-Language: en-us, en-gb;q=0.1, en;q=0.7, fr, fr-ch, da, de, fiIf-Modified-Since: Wed, 09 Sep 2020 16:06:01 -0700User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11 Does the client have a cached copy of the object being requested? a. Yes, because this is a conditional GET. b. No, because the client would not request an object if it were cached. c. There's not enough information to answer this question.

a. Yes, because this is a conditional GET.

Suppose now the server sends the following HTTP response message the client: HTTP/1.0 200 OKDate: Wed, 09 Sep 2020 23:46:21 +0000Server: Apache/2.2.3 (CentOS)Last-Modified: Wed, 09 Sep 2020 23:51:41 +0000ETag:17dc6-a5c-bf716880.Content-Length: 418Connection: CloseContent-type: image/html Will the web server close the TCP connection after sending this message? a. Yes, the server will close this connection because version 1.0 of HTTP is being used, and TCP connections do not stay open persistently. b. Yes, because the HTTP response indicated that only one object was requested in the HTTP GET request. c. No, the server will leave the connection open as a persistent HTTP connection. d. There's not enough information in the response message to answer this question.

a. Yes, the server will close this connection because version 1.0 of HTTP is being used, and TCP connections do not stay open persistently.

Match the names of the principal router components (A,B,C,D below) with their function and whether they are in the network-layer data plane or control plane. *image 6* (A) are ... (B) is ... (C) are ... (D) is ...

a. input ports, operating primarily in the data plane. b. the switching fabric, operating primarily in the data plane. c. output ports, operating primarily in the data plane. d. the routing processor, operating primarily in the control plane.

Which of the following are changes between HTTP 1.1 and HTTP/2? Note: select one or more answers. a. HTTP/2 has many new HTTP methods and status codes. b. HTTP/2 allows objects in a persistent connection to be sent in a client-specified priority order. c. HTTP/2 allows a large object to be broken down into smaller pieces, and the transmission of those pieces to be interleaved with transmission other smaller objects, thus preventing a large object from forcing many smaller objects to wait their turn for transmission. d. HTTP/2 provides enhanced security by using transport layer security (TLS).

b,c

When an application uses a TCP socket, what transport services are provided to the application by TCP? Check all that apply. a. Throughput guarantee. The socket can be configured to provide a minimum throughput guarantee between sender and receiver. b. Loss-free data transfer. The service will reliably transfer all data to the receiver, recovering from packets dropped in the network due to router buffer overflow. c. Flow Control. The provided service will ensure that the sender does not send so fast as to overflow receiver buffers. d. Real-time delivery. The service will guarantee that data will be delivered to the receiver within a specified time bound. e. Best effort service. The service will make a best effort to deliver data to the destination but makes no guarantees that any particular segment of data will actually get there. f. Congestion control. The service will control senders so that the senders do not collectively send more data than links in the network can handle.

b,c,f

What do we mean when we say "HTTP is stateless"? In answering this question, assume that cookies are not used. Check all answers that apply. a. The HTTP protocol is not licensed in any country. b. An HTTP client does not remember anything about what happened during earlier steps in interacting with any HTTP server. c. An HTTP server does not remember anything about what happened during earlier steps in interacting with this HTTP client. d. An HTTP client does not remember the identities of the servers with which it has interacted. e. We say this when an HTTP server is not operational.

c. An HTTP server does not remember anything about what happened during earlier steps in interacting with this HTTP client.

If-Modified-Since. What is the purpose of the If-Modified-Since field in a HTTP GET request message a. To indicate to the server that the client wishes to receive this object, and the time it until it which it will cache the returned object b. To allow the server to indicate to the client that it (the client) should cache this object. c. To inform the HTTP cache that it (the cache) should retrieve the full object from the server, and then cache it until the specified time. d. To indicate to the server that the client has cached this object from a previous GET, and the time it was cached. e. To indicate to the server that the server should replace this named object with the new version of the object attached to the GET, if the object has not been modified since the specified time

d. To indicate to the server that the client has cached this object from a previous GET, and the time it was cached.

When an application uses a UDP socket, what transport services are provided to the application by UDP? a. Throughput guarantee. The socket can be configured to provide a minimum throughput guarantee between sender and receiver. b. Loss-free data transfer. The service will reliably transfer all data to the receiver, recovering from packets dropped in the network due to router buffer overflow. c. Flow Control. The provided service will ensure that the sender does not send so fast as to overflow receiver buffers. d. Real-time delivery. The service will guarantee that data will be delivered to the receiver within a specified time bound. e. Best effort service. The service will make a best effort to deliver data to the destination but makes no guarantees that any particular segment of data will actually get there. f. Congestion control. The service will control senders so that the senders do not collectively send more data than links in the network can handle.

e. Best effort service. The service will make a best effort to deliver data to the destination but makes no guarantees that any particular segment of data will actually get there.

Which of the following physical layer technologies has the highest transmission rate and lowest bit error rate in practice? Fiber optic cable Coaxial cable Twisted pair (e.g., CAT5, CAT6) 802.11 WiFi Channel Satellite channel 4G/5G cellular

fiber optic cable