Summary

In this chapter we have examined the characteristics of the TCP and UDP protocols, which implement transport in the TCP/IP stack. In addition, we have examined how these protocols underlie higher-level application protocols such as SMTP and HTTP. Without reliable delivery provided by TCP and lightweight delivery provided by UDP, application protocols would be unable to function.

Questions

1.	What is the purpose of the DATA command? Indicates that the data being sent is message data. Indicates that the host speaks ESMTP. Lists local members of a mailing list. Indicates that the host speaks SMTP.
2.	What is the purpose of the EHLO command? Indicates that the data being sent is message data. Indicates that the host speaks ESMTP. Lists local members of a mailing list. Indicates that the host speaks SMTP.
3.	What is the purpose of the EXPN command? Indicates that the data being sent is message data. Indicates that the host speaks ESMTP. Lists local members of a mailing list. Indicates that the host speaks SMTP.
4.	What is the purpose of the HELO command? Indicates that the data being sent is message data. Indicates that the host speaks ESMTP. Lists local members of a mailing list. Indicates that the host speaks SMTP.
5.	The QUIT command is used for what purpose? Contains the address of the sender. Ends a session. Contains the address of the recipient. Verifies that a recipient address exists as a user account on the system.
6.	The RCPT command is used for what purpose? Contains the address of the sender. Ends a session. Contains the address of the recipient. Verifies that a recipient address exists as a user account on the system.
7.	The VRFY command is used for what purpose? Contains the address of the sender. Ends a session. Contains the address of the recipient. Verifies that a recipient address exists as a user account on the system.
8.	The MAIL command is used for what purpose? Contains the address of the sender. Ends a session. Contains the address of the recipient. Verifies that a recipient address exists as a user account on the system.
9.	What is the correct description of the HTTP code 200? OK Created Accepted Non-Authoritative Information
10.	What is the correct description of the HTTP code 201? OK Created Accepted Non-Authoritative Information
11.	What is the correct description of the HTTP code 202? OK Created Accepted Non-Authoritative Information
12.	What is the correct description of the HTTP code 203? OK Created Accepted Non-Authoritative Information
13.	What is the correct description of the HTTP code 204? No Content Reset Content Partial Content Bad Request
14.	What is the correct description of the HTTP code 205? No Content Reset Content Partial Content Bad Request
15.	What is the correct description of the HTTP code 206? No Content Reset Content Partial Content Bad Request

Answers

1.	A. The DATA command indicates that the data being sent is message data.
2.	B. The EHLO command indicates that the host speaks ESMTP.
3.	C. The EXPN command lists local members of a mailing list.
4.	D. The HELO command indicates that the host speaks SMTP.
5.	B. The QUIT command ends a session.
6.	C. The RCPT command contains the address of the recipient.
7.	D. The VRFY command verifies that a recipient address exists as a user account on the system.
8.	A. The MAIL command contains the address of the sender.
9.	A. The HTTP code 200 indicates “OK.”
10.	B. The HTTP code 201indicates “Created.”
11.	C. The HTTP code 202 indicates “Accepted.”
12.	D. The HTTP code 203 indicates “Non-Authoritative Information.”
13.	A. The HTTP code 204 indicates “No Content.”
14.	B. The HTTP code 205 indicates “Reset Content.”
15.	C. The HTTP code 206 indicates “Partial Content.”