Networking Midterm

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? [Note: you can findmore problems like this one

.000012 secs

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

1.5 Mbps

1.3-4 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 circuitsbetween D and A. What is the maximum number of connections that can be ongoing in the network at any one time?

70

1.1-1 What is the Internet? Which of the following descriptions below correspond to a "nuts-and-bolts" view of the Internet? Select oneor more of the answers below that are correct

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

3.1-4 Transport-layer services using UDP. Check all of the services below that are provided by the UDP protocol.

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

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 atthat layer, using the pulldown menu.

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

2.2-09 Why Web Caching? Which of the following are advantages of using a web cache? Select one or more answers.

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 loadedfrom the nearby cache rather than from the distant server, Caching uses less bandwidth coming into an institutional network where the client is located, if the cache is also located in that institutional network

1.2-1 Access network per-subscriber speeds. Match the access network with the approximate speeds that a subscriber mightexperience. (Note: if you look these up, do so in the 8E textbook, slides, or video -- not in the 7E or earlier versions, since link accessspeeds 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 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

1.2-2 Link Transmission Characteristics. Which of the following physical layer technologies has the highest transmission rate andlowest bit error rate in practice?

Fiber optic cable

1.3-1 Routing versus forwarding. Choose one of the following two definitions that makes the correct distinction between routing versusforwarding.

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 ofdetermining the source-destination paths taken by packets

2.1-1 The client-server paradigm. Which of the characteristics below are associated with a client-server approach to structuring networkapplications (as opposed to a P2P approach)?

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

2.1-2 The peer-to-peer (P2P) paradigm. Which of the characteristics below are associated with a P2P approach to structuring networkapplications (as opposed to a client-server approach)?

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

3.1-5 Network-layer functionality. The transport layer sits on top of the network layer, and provides its services using the servicesprovided 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:

True

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

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

Protocols that are part of a distributed networkapplication- Application Layer. Transfer of data between one process and anotherprocess (typically on different hosts)- Transport Layer. Delivery of datagrams from a source host to adestination 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.

3.1-3 Transport layer services using TCP. Check all of the services below that are provided by the TCP protocol

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

1.3-2 Packet switching versus circuit switching (1). Which of the characteristics below are associated with the technique of packetswitching? Select all correct answers. [Hint: more than one of the answers is correct].

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

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 messagecontents, and to identify the originator of a message- Digital signatrues. Limiting use of resources or capabilities to given users- Access control. Proving you are who you say you are- Authentication.

1.5-4 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 thatlayer.

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, lookuppacket information in a local table and move the packetfrom an input link to an output link in a router- Processing delay. Time spent waiting in packet buffers for linktransmission- Queueing delay. Time spent transmitting packets bits into the link- Transmission delay. Time need for bits to physically propagate through thetransmission medium from end one of a link to theother- Propagation delay.