Midterm Flashcards
Which of the following applications are naturally suitable for P2Parchitectures?
A. Distributed Computing
B. Instant Messaging
C. Video Streaming
D. None of the above
A-B-C
Consider a HTTP client wants to retrieve a Web document at a given URL. The IP address of the HTTP server is initially unknown. WhatApplication-layer and Transport-layer protocols besides HTTP are needed in this scenario?
A. UDP for DNS and TCP for HTTP
B. UDP for both DNS and HTTP
C. TCP for both DNS and HTTP
D. UDP for HTTP and TCP for DN
B
If 10 files are being transferred using FTP from server A to client Bin the same session. The number of TCP connections between A and B is:
A. 1
B. 10
C. 11
D. 2
C (1 control 10 data)
Which one of the following protocols delivers/stores mail to receiver mail server?
A. SMTP
B. POP3
C. IMAP
D. HTTP
A
In a router, queuing can occur:
A. in the input ports
B. in an interconnection network
C. in the output ports
D. all of the above
D
Telnet is a protocol for the ________ layer (i.e., one of the layers for the internet/OSI model)
Apllication
_________, refers to the per-router action of moving a packet arriving at an input port to the appropriate output port
Forwarding
________, refers to the process of determining the end-to-end path that a packet will take through the network
Routing
In a P2P system, nodes that take resources from a system without contributing in kind are called _______
Free-riders
In BitTorrent, a ________ is a server that maintains a list of all the peers that are actively downloading and uploading the file. The group of peers exchanging chunks of a file is referred to as _________
Tracker - Torrent
HTTP is a stateless protocol. However, using ______, web applications can keep stateful information about user’s activity.
Cookies
List 1 advantage and 1 disadvantage of having international standards for network protocols.
One advantage is that if everyone uses the standard, everyone can talk to everyone and people can create networking systems and products that interoperate.
A disadvantage is that once a standard has been widely adopted, it is difficult to change, even if new and better techniques or methods are dis-covered. Also, by the time it has been accepted, it may be obsolete.
List, in order, the layers of the TCP/IP stack, starting with the layer thatis part of your program implementation
Application Transport Network Link Physical
What is encapsulation and why is it important for the operation of a protocol stack?
Encapsulation is the concept of wrapping data from an upper layer’s protocol with a new header for the current layer and treating the upper layer’s data as uninterpreted. Encapsulation allows us to isolate the functionalityof a layer and change layer information without aecting the rest of theprotocol stack
Suppose the algorithms used to implement the operations at layer k is changed. How does this impact operations at layers k-1 and k+ 1?
This has no impact on the operations at layers k-1 or k+ 1.
Suppose there is a change in the service (set of operations) provided by layer k. How does this impact services at layers k-1 and k+ 1?
There is no impact at layer k-1, but operations in k+ 1 have to be reimplemented.
What are the main components of delay assuming packet switching is used along the network?
Processing
Queueing
Transmission
Propagation
What is the difference between transmission delay and propagation delay?
Transmission delay is the time needed to put the entire packet on the linkand is dependent on the length of the packet, while the propagation delayis the time needed for one bit to reach the other end of the link
How is propagation delay affected if the length of the packet is increased?
This delay is just a function of link length and its physical characteristics,so it is NOT affected.
Consider the following forms of non-Internet data distribution: FM radio, broadcast TV, and newspapers. Are these Push or Pull systems?
FM radio, broadcast TV, and newspapers are all push systems. Information is sent out via these media regardless of whether or not anyone is tuning in to the TV or radio stations, or buying the newspaper. Also,content is not individualized for the receiver.
Is the traditional Web browser/server aPushorPullsystem? Explain
The Web is a pull system because data is not transmitted to the browserunless it is explicitly requested by the browser. Some automated phoneresponse systems are non-Internet pull systems. For example, I may call anumber to get my horoscope, and enter my birth date in order to have myhoroscope read to me
SMTP transfers messages between mail servers using aPushsystem. Discuss the changes to SMTP operations if the transfer of messages betweenmail servers was implemented as a Pull system
mail servers must keep track of all existing mail servers and continuouslycheck for new e-mails. This would create a lot of trac on the network between two hosts
Suppose you use your web-based e-mail account (e.g., gmail) to send a message to your colleague, who accesses his mail from his mail server usingPOP3. Discuss how the message gets from your host to your friend’s host.List the series of application-layer protocols that are used to move the message between the two hosts.
The message is rest sent from my host to my mail server over HTTP. My mail mail server then sends the message to my friend’s mail server over SMTP. My friend then transfers the message from his mail server to his host over POP3.
Suppose you can configure your browser to open multiple simultaneous connections to a Web site? What are the advantages and disadvantages of having a large number of simultaneous TCP connections?
The advantage is that you will you potentially download the le faster. The disadvantage is that you may be hogging the bandwidth, thereby significantly slowing down the downloads of other users who are sharing the same physical links.
Application layer protocols implemented on the source and destination host must match (T/F)
T
It is not possible for an application to enjoy reliable data transfer when the application runs over UDP (T/F)
F
The application developer can put reliable data transfer into the application layer protocol. This would require a signicant amount of work and debugging,however.
HTTP, FTP, SMTP, and POP3 run on top of UDP (T/F)
F
The applications associated with those protocols require that all application data be received in the correct order and without gaps. TCP provides this service whereas UDP does not.
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. (T/F)
F
The web server will have the same port number for all processes.
Bandwidth Flooding is a DoS (Denial of Service) attack in which theattacker establishes a large number of half-open or fully open TCP connections at the target host (T/F)
F
his is a Connection Flooding attack.
In IP spoofing, the attacker interchanges the source and destination addresses in the sender’s IP datagram (T/F)
F
