Computer Networking : Principles, Protocols and Practice

Internet applications

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Internet applications

Multiple choice questions

The Domain Name System

  1. Which of the following DNS Resource Records should be queried to retrieve the IPv6 address associated to a name ?
The AAAA record.

The A record.

The NS record.

The MX record.

  1. You use the DNS to retrieve the IPv4 address associated to the name cnp3book.info.ucl.ac.be. Assuming that you need to start your query from the root of the domain name system, which of the following DNS record will you never query to obtain this information.

The AAAA record.

The A record.

The NS record.

The MX record.

Electronic mail

  1. Which of the following affirmations about electronic mail on the Internet are valid ? Select all the correct ones in the list.
The SMTP protocol is used to deliver email messages between servers and also between a client an a server.

The SMTP protocol is used by the recipient to retrieve his/her email messages.

The POP and IMAP protocols are used by the recipient to retrieve his/her email messages.
The SMTP protocol runs above the User Datagram Protocol (UDP).
The POP protocol runs above the User Datagram Protocol (UDP).
An email is a sequence of ASCII lines. The first lines contain the information required to deliver the email. An empty line is used to separate the header from the content of the email.
  1. The format of the Internet emails is defined in RFC 2822. This specification describes all the nitty details of the format of email messages. The bullets below show several email messages. Only one of them is syntactically valid. Which one ?
From: Alice <alice@example.net>
To: Bob <mary@example.com>
Subject: Saying Hello
Date: Fri, 21 Nov 1997 09:55:06 -0600

This is a message just to say hello.
So, "Hello".

From: Alice <alice@example.net>
Subject: Saying Hello
Date: Fri, 21 Nov 1997 09:55:06 -0600
To: Bob <mary@example.com>


This is a message just to say hello.
So, "Hello".

From: Alice "alice@example.net"
Subject: Saying Hello
Date: Fri, 21 Nov 1997 09:55:06 -0600
To: Bob "mary@example.com"

This is a message just to say hello.
So, "Hello".

From: Alice <alice@example.net>
Subject: Saying Hello
Date: Fri, 21 Nov 1997 09:55:06 -0600
To: Bob <mary@example.com>
This is a message just to say hello.
So, "Hello".

From: Alice "alice@example.net"
Subject: Saying Hello
Date: Fri, 21 Nov 1997 09:55:06 -0600
To: Bob "mary@example.com"
This is a message just to say hello.
So, "Hello".

From: Alice <alice@example.net>
Subject: Saying Hello
To: Bob <mary@example.com>

This is a message just to say hello.
So, "Hello" .
  1. The SMTP protocol is a key protocol for the delivery of Internet email messages. This protocol is a stateful protocol where the client sends commands to the server. Which of the following affirmations about the SMTP commands are correct ? Select all the valid ones.

The HELO command is the first command sent by a client on an SMTP session. It is always followed by a domain name as in the example below :

HELO uclouvain.be

The HELO command can be issued at any time during an SMTP session.

The MAIL FROM: command must be issued before the DATA comment. It contains as parameter a valid email address as in the example below :

MAIL FROM: <alice@example.net>

The MAIL FROM: command can only be issued after the DATA comment. It contains as parameter a valid email address as in the example below :

MAIL FROM: <bob@example.com>
The DATA command can only be issued once the MAIL FROM: and RCPT TO: commands have been issued. It is followed by the entire email message that is transmitted.
The QUIT command is the last command from an SMTP session. It terminates the session.
  1. The Base64 format, defined in RFC 2045 and RFC 4648 allows to encode any binary information in a sequence of ASCII characters. Only one affirmation below concerning Base64 is valid. Which one ?
Base64 encodes three 8 bits ASCII characters as a sequence of four characters.
Base64 encodes four 8 bits ASCII characters as a sequence of three characters.
A Base64 encoded string may contains the characters A-Z, a-z, 0-9 as well as +, / and =

A Base64 encoded string can only contain letters (A-Z and a-z) and digits (0-9)

A Base64 encoded string may contain the character =.

A Base64 encoded string may never contain the character =. .. comment:: This character may be used, only in the last characters of the Base64 encoded string if the number of bytes to be encoded is not a multiple of three.

The HyperText Transfer Protocol

  1. The Uniform Resource Identifiers (URI) defined in RFC 3986 are a key element of the world wide web. Among the URIs below, select the ones that are valid URIs.
http://example.net

http:example.net

http://example.net@/example.com

http://example.com:user/index.html

http:80//example.com/index.html

  1. The Uniform Resource Identifiers (URI) defined in RFC 3986 are used to indicate the domain name of the server that needs to be contacted to retrieve a document. Which of the following affirmations are valid for these URIs ?
In the http://example.net/example.com URI, the server name is example.com
In the http://example.net/example.com URI, the server name is example.net
In the http://example.net:1234/example.com/test.com URI, the server name is example.net
In the http://example.net:1234/example.com/test.com URI, the server name is example.com
In the http://example.net:1234/example.com/test.com URI, the server name is test.com
In the http://example.com@/example.net/test.com URI, the server name is example.net
In the http://example.com@/example.net/test.com URI, the server name is test.com
  1. Which of the following affirmations are valid concerning the HTTP protocol ? Select all the valid affirmations from the ones listed below.
HTTP is a stateless protocol.

HTTP is a stateful protocol.

HTTP supports three different methods : GET, HEAD and POST

HTTP supports a single method : GET

A HTTP request contains a method and sequence of header lines. It ends with a blank line.

The HTTP protocol can only be used to receive documents from a server.

  1. The extensibility of the HTTP protocol comes from the various header lines that it supports. Some of these header lines appear inside requests while others appear inside responses. Among the following affirmations about these headers, select the ones that are valid.
The Host header line can appear inside an HTTP request. It indicates the name of the server from which the document can be retrieved.

The Server header line can appear inside an HTTP request. It indicates the name of the server from which the document can be retrieved.

The Last-Modified header line is included in the HTTP responses. It contains as parameter the last modification date of the retrieved document.

The User-Agent header line can appear inside HTTP responses. It indicates the application that should process the response.

The Referrer header line may appear in HTTP requests. It indicates the URI that was visited before retrieving this URI.

The Content-Length, Content-Type and Content-Encoding header lines may appear inside HTTP requests.

The Content-Length, Content-Type and Content-Encoding header lines can only appear inside HTTP responses.

Verify your answers

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