CPSC 471 Chapter 1 Study Set

What is the Internet? 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 the answers below are correct].

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

1.1-2 What is the Internet (2)? Which of the following descriptions below correspond to a "services" 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 place I go for information, entertainment, and to communicate with people. - A platform for building network applications.

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")? Select one or more answers below that are correct. [Hint: more than one of the answers below are correct.]

- 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. - One person asking, and getting, the time to/from another person. -Two people introducing themselves to each other.

1.5-2 What's a "packet" really called? Match the name of an Internet layer with unit of data that is exchanged among protocol entities at that layer, using the pulldown menu.

- Application layer = Message - Transport layer = Segment - Network layer = Datagram - Link layer = Frame - Physical layer = Bit

Packet switching versus circuit switching (1). Which of the characteristics below are associated with the technique of packet switching? Select all correct answers. [Hint: more than one of the answers is correct].

- Data may be queued before being transmitted due to other user's data that's also queueing for transmission. - This technique is used in the Internet. - Resources are used on demand, not reserved in advance. - Congestion loss and variable end-end delays are possible with this technique.

1.4-05 Computing Propagation Delay. Consider the network shown in the figure below, with three links, each with the specified transmission rate and link length. Assume the length of a packet is 8000 bits. The speed of light propagation delay on each link is 3x10^8 m/secWhat is the propagation delay at (along) link 2?

.0033 secs

Link Transmission Characteristics. Which of the following physical layer technologies has the highest transmission rate and lowest bit error rate in practice?

Fiber optic cable

Routing versus forwarding. Choose one of the following two definitions that makes the correct distinction between routing versus forwarding.

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 is "encapsulation"? Which of the definitions below describe what is meant by the term "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.

1.3-7 Packet switching or Circuit-switching? Consider a scenario in which 5 users are being multiplexed over a channel of 10 Mbps. Under the various scenarios below, match the scenario to whether circuit switching or packet switching is better.

- Each user generates traffic at an average rate of 2.1 Mbps, generating traffic at a rate of 15 Mbps when transmitting = Neither works well in this overload scenario - Each user generates traffic at an average rate of 2 Mbps, generating traffic at a rate of 2 Mbps when transmitting = circuit switching - Each user generates traffic at an average rate of 0.21 Mbps, generating traffic at a rate of 15 Mbps when transmitting = packet switching

1.7-1 Networking history - when did it happen? Match the networking event with the time frame when the event occurred.

- Early studies of packet switching by Baran, Davies, Kleinrock. = Early 1960's - First ARPAnet node is operational. = Late 1960's - Internetting: DARPA researchers connect three networks together. = 1970's - The Internet Protocol (IP) is standardized in RFC 791. = Early 1980's - Congestion control is added to the TCP protocol. = Late 1980's - The WWW starts up (note: the WWW design started at the end of previous decade). = 1990's - Software-defined networking begins. = 2000-2010 - The number of wireless Internet-connected devices surpasses the number of connected wired devices. = 2010 - 2020

Protocol headers. 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.

- Header H1 = Link layer - Header H2 = Network layer - Header H3 = Transport layer -

Suppose a packet is L = 1200 bytes long (one byte = 8 bits), and link transmits at R = 100 Mbps (i.e., a link can transmit bits 100,000,000 bits per second). What is the transmission delay for this packet?

.000096 secs

1.5-1 Layers in the Internet protocol stack. Match the function of a layer in the Internet protocol stack to the name of the layer implementing that function.

- Protocols that are part of a distributed network application. = Application Layer - Transfer of data between one process and another process (typically on different hosts). = Transport Layer - Delivery of datagrams from a source host to a destination host (typically). = Network Layer - Transfer of data between neighboring network devices. = Link layer - Transfer of a bit into and out of a transmission media. = Physical layer

1.3-3 Packet switching versus circuit switching (2). Which of the characteristics below are associated with the technique of circuit switching? Select all correct answers. [Hint: more than one of the answers is correct].

- Reserves resources needed for a call from source to destination. - This technique was the basis for the telephone call switching during the 20th century and into the beginning of this current century. - Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM) are two approaches for implementing this technique.

1.6-1 Security defenses. Match the description of a security defense with its name.

- Specialized "middleboxes" filtering or blocking traffic, inspecting packet contents inspections = Firewall - Provides confidentiality by encoding contents = Encryption - Used to detect tampering/changing of message contents, and to identify the originator of a message. = Digital signatures - Limiting use of resources or capabilities to given users. = Access control - Proving you are who you say you are. = Authentication

1.3-6 What is a network of networks? When we say that the Internet is a "network of networks," we mean? Check all that apply (hint: check two or more).

- 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.

1.4-01 Components of packet delay. Match the description of each component of packet delay to its name in the pull down list.

- 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 - Time spent transmitting packets bits into the link. = Transmission delay - Time need for bits to physically propagate through the transmission medium from end one of a link to the other. = Propagation delay

1.4-02 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?

.000012 secs

1.4-10 Computing utilization (3). 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. Assuming that the servers are all sending at their maximum rate possible, what are the link utilizations of the client links (with transmission capacity RC)? Enter your answer in a decimal form of 1.00 (if the utilization is 1) or 0.xx (if the utilization is less than 1, rounded to the closest xx).

0.56

1.4-09 Computing utilization (2). 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.Assuming that the servers are all sending at their maximum rate possible, what are the link utilizations of the shared link (with transmission capacity R)? Enter your answer in a decimal form of 1.00 (if the utilization is 1) or 0.xx (if the utilization is less than 1, rounded to the closest xx).

0.67

1.4-08 Computing utilization (1). 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.Assuming that the servers are all sending at their maximum rate possible, what are the link utilizations for the server links (with transmission capacity RS)? Enter your answer in a decimal form of 1.00 (if the utilization is 1) or 0.xx (if the utilization is less than 1, rounded to the closest xx).

1.00

1.4-06 Computing throughput: a simple scenario. What is the maximum throughput achievable between sender and receiver in the scenario shown below

1.5 Mbps

1.4.11 Computing maximum throughput. Consider the scenario shown below, with 10 different servers (three shown) connected to 10 different clients over ten three-hop paths. The 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 = 90 Mbps. Each of the four links from the shared middle link to a client has a transmission capacity of RC = 50 Mbps.

30 Mbps

1.4-07 Computing throughput. 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? [Note: Give your answer as an integer, with no leading zeros, and no decimal points.

50

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.

70

1.4-04 Computing Packet Transmission Delay (3). Consider the network shown in the figure below, with three links, each with the specified transmission rate and link length. Assume the length of a packet is 8000 bits.What is the transmission delay at link 2?

8 x 10^(-5) secs

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, slides, or video -- not in the 7E or earlier versions, since link access speeds are always increasing over the years).

Ethernet - Wired. Up to 100's Gbps per link. 4G cellular LTE - Wireless. Up to 10's Mbps per device. 802.11 WiFi - Wireless. 10's to 100's of Mbps per device. Cable access network - Wired. Up to 10's to 100's of Mbps downstream per user. Digital Subscriber Line - Wired. Up to 10's of Mbps downstream per user.