Homework2

Suppose you want to obtain a Web page associated with the link contains one base html file and 24 reference objects. Let RTT denote the round-trip time between the local host and the server containing the objects. Assuming zero transmission delay. Further assume the IP address for the associated URL is cached in your local host, so no DNS lookup is necessary. How much time elapses from when the client clicks on the link until the client receives all objects if non-persistent HTTP without parallel is used? A) 14RTT B) 3RTT C) 26RTT D) 50RTT

D) 50RTT

When a client sends a DNS query to a DNS server, which port numbers are typically used by the client and the server? A) Client uses port 53, server uses a random port selected by the OS B) Client uses port 443, server uses port 53 C) Client uses port 53, server uses port 80 D) Client uses a random port selected by the OS, server uses port 53

D) Client uses a random port selected by the OS, server uses port 53

What is the primary difference between FTP and FTPS in terms of port numbers? A) FTP uses port 20/21, while FTPS uses port 80 B) FTP uses port 20/21, while FTPS uses port 25 C) FTP and FTPS use the same port number D) FTP uses port 20/21, while FTPS uses ports 989/990

D) FTP uses port 20/21, while FTPS uses ports 989/990

The user agents are email app. At point 4 in the diagram, what protocol is being used? A) POP3 B) TLS（HTTPs） C) IMAP D) SMTP

D) SMTP

Which protocol uses port 22 by default and provides a secure method for remote login and other secure network services? A) Telnet B) FTP C) HTTP D) SSH

D) SSH

Which of the following is a significant advantage of P2P architecture over the client-server model? A) Limited resource sharing B) Centralized control and management C) High infrastructure costs D) Scalability and flexibility

D) Scalability and flexibility

Suppose you want to obtain a Web page associated with the link contains one base html file and 10 reference objects. How many HTTP request/response message and TCP connection will be established if Persistent-HTTP without Piplining is used? 10, 3 11, 3 11, 1 3, 3

11, 1

Suppose you want to obtain a Web page associated with the link contains one base html file and 10 reference objects. How many HTTP request/response message and TCP connections will be established if Non-persistent http connection with 5 parallel allowed? 11, 11 10, 10 11, 6 11, 1

11, 11

Suppose you want to obtain a Web page associated with the link contains one base html file and 24 reference objects. Let RTT denote the round-trip time between the local host and the server containing the objects. Assuming zero transmission delay. Further assume the IP address for the associated URL is cached in your local host, so no DNS lookup is necessary. How much time elapses from when the client clicks on the link until the client receives all objects if persistent HTTP withOUT pipelining is used? A) 26RTT B) 50RTT C) 14RTT D) 3RTT

A) 26RTT

Which of the following DNS server provides authoritative hostname to IP mappings for organization's named hosts A) Authoritative DNS server B) Top Level Domain (TLD) servers C) Local DNS server D) DNS root servers

A) Authoritative DNS server

Which of the following port will be used if SMTP is transmitted over TSL? A) 143 B) 587 C) 25 D) 21

B) 587

Which of the following is true about HTTP/1.0? A) It supports persistent connections by default B) Each request/response pair requires a new TCP connection C) It uses multiplexing to handle multiple requests D) It supports server push

B) Each request/response pair requires a new TCP connection

What is the major improvement of HTTP/2 Versus HTTP/1.1? A) HTTP/2 allows objects in a persistent connection to be sent while HTTP/1.1 doesn't support it B) 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. C) HTTP/2 provides enhanced security by using transport layer security (TLS) D) HTTP/2 has many new HTTP methods and status codes.

B) 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.

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

D) Store/serve multiple copies of videos at multiple geographically distributed sites

The user agents is web browser (webmail). At point 2 in the diagram, what protocol is possibly being used? A) SMTP B) POP3 C) IMAP D) TLS （HTTPs）

D) TLS （HTTPs）

What is the purpose of the conditional HTTP GET request message? A) To allow a server to only send the requested object to the client if the client is authorized to received that object B) To allow a server to only send the requested object to the client if the server is not overloaded C) To allow a server to only send the requested object to the client if the client has never requested that object before D) To allow a server to only send the requested object to the client if this object has changed since the server last sent this object to the client.

D) To allow a server to only send the requested object to the client if this object has changed since the server last sent this object to the client.

What is the primary function of DNS in a network? A) To encrypt data sent over the internet B) To manage email delivery C) To monitor network traffic D) To resolve domain names to IP addresses

D) To resolve domain names to IP addresses

In DASH, a server divides a video file into chunks that A) are download smallest-chunk-first in order to maximize the number of chunks received B) are downloaded just before their playout time. Chunking is used primarily because a viewer may jump around (e.g., fast forward) in a video C) 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 D) 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

D) 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 statements about DNS is true? a) The DNS system is responsible for encrypting domain names b) A CNAME record is used to map a domain name to an IPv6 address c) DNS always uses TCP for all queries d) DNS primarily uses UDP for queries

d) DNS primarily uses UDP for queries

Which of the following statement is true about web caching? 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 uses more bandwidth coming into an institutional network where the client is located, if the cache is also located in that institutional network. Because if there is a cache miss, not just the client but the web cache server also needs to send request to the origin web server C) Web cache will works better in improving web application user experience if it has a smaller hit rate D) Caching allows an origin server to more carefully track which clients are requesting and receiving which web objects

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

Which of the following protocol will be used when you run "nslookup www.ung.edu"? A) DNS B) FTP C) SMTP D) HTTP

A) DNS

What is the primary role of a Content Distribution Network (CDN) in the context of video streaming? A) Distributing video content to end-users efficiently B) Capturing and storing user-generated video content C) Encoding and compressing video content D) Analyzing viewer engagement data

A) Distributing video content to end-users efficiently

Which of the following statement is true? A) HTTP is stateless means that an HTTP server does not remember anything about what happened during earlier steps in interacting with this HTTP client B) Based on BitTorrent protocol, the more you contribute to others in the P2P network, potentially, the faster you will get what you want from the network. So in a large P2P network, theoretically, if you never contribute, there is no way you can get what you want C) HTTP is stateless means that an HTTP client does not remember anything about what happened during earlier steps in interacting with this HTTP client D) If a network application use CS architecture, a client can get content or service from other clients within the network while the server is not on

A) HTTP is stateless means that an HTTP server does not remember anything about what happened during earlier steps in interacting with this HTTP client

Which of the following protocol is commonly used to enable a mail client to pull email from a mail server? A) IMAP B) FTP C) SMTP D) HTTP

A) IMAP

What is a significant advantage of HTTP/3.0 over previous versions? A) It reduces latency and improves performance by using QUIC B) It removes the need for persistent connections C) It uses TCP to improve reliability D) It maintains backward compatibility with HTTP/1.0

A) It reduces latency and improves performance by using QUIC

What is a key feature introduced in HTTP/1.1 that was not present in HTTP/1.0? A) Persistent connections (keep-alive) B) Multiplexing of requests C) Header compression D) Support for encryption with TLS

A) Persistent connections (keep-alive)

Which of the following protocols is typically associated with port 23 and is considered insecure for remote login due to the lack of encryption? A) Telnet B) FTP C) SSH D) HTTP

A) Telnet

Which of the following statement is true? A) The HTTP GET request message is sent by a web server to a web client to get the identity of the web client B) 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 C) The HTTP GET request message is used by a web client to post an object on a web server 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

B) 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

What is the primary purpose of Dynamic Adaptive Streaming over HTTP (DASH) in online video streaming? A) To ensure the content is streamed in a fixed quality to all viewers B) To adapt the video quality based on each viewer's network conditions C) To enable live streaming of video content D) To compress video files for faster streaming

B) To adapt the video quality based on each viewer's network conditions

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

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

What is the primary purpose of a web cache in a network architecture? A) To encrypt web traffic for secure communication B) To store and serve frequently accessed web resources C) To route web traffic between clients and servers D) To compress web content for faster transmission

B) To store and serve frequently accessed web resources

In your Web browser you click on a link to obtain a Web page. The IP address for the associated URL is not cached in your local host, so a DNS lookup is necessary to obtain the IP address. Suppose that four DNS servers are visited before your host receives the IP address from DNS. The first DNS server visited is the local DNS cache, with an RTT delay of RTT0 = 5 msecs. The second, third and fourth DNS servers contacted have RTTs of 10, 32, and 41 msecs, respectively. Initially, let's suppose that the Web page associated with the link contains exactly one object, consisting of a small amount of HTML text (with no reference object). Suppose the RTT between the local host and the Web server containing the object is RTTHTTP = 74 msecs. Assuming zero transmission time for the HTML object, how much time (in msec) elapses from when the client clicks on the link until the client receives the object? A) 162 B) 3 C) 236 D) 74

C) 236

Which of the following statement about 'HTTP cookie' is true? A) 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.] B) A cookie is a code used by a client to authenticate a person's identity to an HTTP server C) 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.] D) A cookie is used to spoof client identity to an HTTP server.

C) 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.]

In a P2P network, which of the following statements is true? A) Communication between peers always goes through intermediaries B) P2P networks cannot be scaled to accommodate additional peers C) Each peer has equal status and can act as both a client and a server D) There is a centralized server that manages all communication

C) Each peer has equal status and can act as both a client and a server

Suppose you want to obtain a Web page associated with the link contains one base html file and 24 reference objects. Let RTT denote the round-trip time between the local host and the server containing the objects. Assuming zero transmission delay. Further assume the IP address for the associated URL is cached in your local host, so no DNS lookup is necessary. How much time elapses from when the client clicks on the link until the client receives all objects if non-persistent HTTP with parallel capability is used, the parallel capability allows four TCP connections to be established at one time? A) 50RTT B) 3RTT C) 26RTT D) 14RTT

D) 14RTT

Which port number is typically used by HTTPS to secure web traffic? A) 22 B) 80 C) 21 D) 443

D) 443