CS 436 1-9

1.5-2 What's a "packet" really called? Transport layer

Segment

Time spent transmitting packets bits into the link.

Transmission Delay

1.5-1 Layers in the Internet protocol stack. Transfer of data between one process and another process (typically on different hosts).

Transport Layer

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

A & B

2.1-1 The client-server paradigm. Which of the characteristics below are associated with a client-server approach to structuring network applications (as opposed to a P2P approach)? a) There is a server that is always on. b) There is not a server that is always on. c) There is a server with a well known server IP address. d) A process requests service from those it contacts and will provide service to processes that contact it. e) HTTP uses this application structure.

A, C, & E

3.3-2 UDP header fields. Which of the fields below are in a UDP segment header? [Hint: note the use of the word "header" in this question statement.] a) Internet checksum b) Source IP address c) Source port number d) Destination port number e) Upper layer protocol f) Sequence number g) Length (of UDP header plus payload) h) Data (payload)

A, C, D, G

1.5-1 Layers in the Internet protocol stack. Protocols that are part of a distributed network application.

Application Layer

2.1-4 TCP service. 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, and F

1.5-2 What's a "packet" really called? Link layer

Frame

1.5-2 What's a "packet" really called? Physical layer

Bit

1.5-2 What's a "packet" really called? Network layer

Datagram

1.5-1 Layers in the Internet protocol stack. Transfer of data between neighboring network devices.

Link Layer

1.5-2 What's a "packet" really called? Application layer

Message

1.5-1 Layers in the Internet protocol stack. Delivery of datagrams from a source host to a destination host (typically).

Network Layer

1.5-1 Layers in the Internet protocol stack. Transfer of a bit into and out of a transmission media.

Physical Layer

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.

Processing Delay

Time spent waiting in packet buffers for link transmission.

Queuing Delay

1.4-2 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). What is the transmission delay for this packet? a) .000012 secs b) .00012 secs c) .0000015 secs d) .0015 secs e) 666,666 secs

a) .000012 secs

Computing throughput: a simple scenario. What is the maximum throughput achievable between sender and receiver in the scenario shown below? a) 1.5 Mbps b) 10 Mbps c) 11.5 Mbps

a) 1.5 Mbps

1.1-1 What is the Internet? Which of the following descriptions below correspond to a "nuts-and-bolts" view of the Internet? a) A collection of billions of computing devices, and packet switches interconnected by links. b) A platform for building network applications. c) A "network of networks". d) A place I go for information, entertainment, and to communicate with people. e) 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) A collection of billions of computing devices, and packet switches interconnected by links. c) A "network of networks". e) 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.

2.7-3 Server reply (UDP). How does the networked application running on a server know the client IP address and the port number to reply to in response to a received datagram? a) The application code at the server determines client IP address and port # from the initial segment sent by client, and must explicitly specify these values when sending into a socket back to that client. b) As the result of performing the accept() statement, the server has created a new socket that is bound to that specific client, and so sending into this new socket (without explicitly specifying the client IP address and port number) is sufficient to ensure that the sent data will be addressed to the correct client. c) The server will query the DNS to learn the IP address of the client. d) The server will know the port number being used by the client since all services have a well-known port number.

a) The application code at the server determines client IP address and port # from the initial segment sent by client, and must explicitly specify these values when sending into a socket back to that client.

2.7-2 TCP Sockets. Which of the following characteristics below are associated with a TCP socket? Check one or more that apply. a) socket(AF_INET, SOCK_STREAM) creates this type of socket b) socket(AF_INET, SOCK_DGRAM) creates this type of socket c) a server can perform an accept() on this type of socket d) provides unreliable transfer of a group of bytes (a "datagram"), from client to server e) provides reliable, in-order byte-stream transfer (a "pipe"), from client to server f) the application must explicitly specify the IP destination address and port number for each group of bytes written into a socket g) when contacted, the server will create a new server-side socket to communicate with that client h) data from different clients can be received on the same socket

a, c, e, g

1.1-2 What is the Internet (2)? Which of the following descriptions below correspond to a "services" view of the Internet? a) A collection of billions of computing devices, and packet switches interconnected by links. b) A platform for building network applications. c) A "network of networks". d) A place I go for information, entertainment, and to communicate with people.

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

2.7-1 UDP Sockets. Which of the following characteristics below are associated with a UDP socket? Check one or more that apply. a) socket(AF_INET, SOCK_STREAM) creates this type of socket b) socket(AF_INET, SOCK_DGRAM) creates this type of socket c) a server can perform an accept() on this type of socket d) provides unreliable transfer of a groups of bytes ("a datagram"), from client to server e) provides reliable, in-order byte-stream transfer (a "pipe"), from client to server f) the application must explicitly specify the IP destination address and port number for each group of bytes written into a socket g) when contacted, the server will create a new server-side socket to communicate with that client h) data from different clients can be received on the same socket

b, d, f, h

3.2-2 Transport-layer multiplexing. What is meant by transport-layer multiplexing? a) Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket. b) 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. c) 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. d) 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.

c) 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.

Time need for bits to physically propagate through the transmission medium from end one of a link to the other.

Propagation Delay

2.2-2 HTTP cookies. 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.]

2.4-3 What's in the DNS type A resource record? What information does the type "A" resource record hold in the DNS database? Check all that apply. a) A hostname and an IP address. b) A domain name and the name of the authoritative name server for that domain. c) An alias name and a true name for a server. d) A name and the name of the SMTP server associated with that name.

a) A hostname and an IP address.

2.4-1 DNS functions. Match the function of a server to a given type of DNS server in the DNS server hierarchy. a) Provides authoritative hostname to IP mappings for organization's named hosts. b) Replies to DNS query by local host, by contacting other DNS servers to answer the query. c) Responsible for a domain (e.g., *.com, *.edu); knows how to contact authoritative name servers. d) Highest level of the DNS hierarchy, knows how to reach servers responsible for a given domain (e.g., *.com, *.edu).

a) Authoritative DNS Server b) Local DNS Server c) Top Level Domain (TLD) server d) DNS Root servers

1.3-1 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.

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.

1.1-3 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")? a) One person asking, and getting, the time to/from another person. b) A person reading a book. c) A person sleeping. d) Two people introducing themselves to each other. e) 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.

a) One person asking, and getting, the time to/from another person. d) Two people introducing themselves to each other. e) 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.

3.2-1 Transport-layer demultiplexing. What is meant by transport-layer demultiplexing? a) Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket. b) 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. c) 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. d) 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.

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

3.5-2 TCP segment format. For the given function of a field in the TCP segment, select the name of that field from the pull-down list. a) This field contains the port number associated with the sending socket for this TCP segment. b) This field contains application data that was written into a socket by the sender of this TCP segment. c) 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. d) This field contains the index in the byte stream of the next in-order byte expected at the receiver e) This field contains the number of available bytes in the TCP receiver's buffer. f) This field contains the number of bytes in the TCP header.

a) Source Port Number b) Data (or playload c) Sequence Number d) ACK Number Field e) Receiver Advertised Window f) Header Length Field

2.2-3 The HTTP GET. 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.

2.2-1 "HTTP is stateless." 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.

2.1-3 UDP service. When an application uses a UDP socket, what transport services are provided to the application by UDP? 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.

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.