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Web and Networking Essentials
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1
Question
What is a network application?
Page 2
Answer
A network application is a computer application that requires communication over the network, where layer two protocols are used by the client and server.
2
Question
Name three examples of network applications and their associated transport layer protocols.
Page 2
Answer
Email (SMTP), Web (HTTP), File transfer (FTP).
3
Question
What is the primary focus of security in web applications according to the material?
Page 3
Answer
Security in web applications is mainly achieved through security mechanisms of the transport layer.
4
Question
When was HTTP originally defined, and what is the version discussed in the material?
Page 3
Answer
HTTP was originally defined in 1991 (RFC 1945) and has undergone several revisions; the discussion is based on HTTP/1.1 (RFC 2616).
5
Question
What are the two transport layer protocols used by Internet applications?
Page 4
Answer
TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
6
Question
Why do Internet applications choose TCP over UDP?
Page 4
Answer
Applications choose TCP on the application to provide reliable data delivery.
7
Question
Which transport protocol is used for electronic mail?
Page 5
Answer
SMTP (Simple Mail Transfer Protocol) uses TCP.
8
Question
Which transport protocol is typically used for web browsing?
Page 5
Answer
HTTP uses TCP.
9
Question
What transport protocols are used for remote file access?
Page 5
Answer
NFS (Network File System) uses UDP or TCP.
10
Question
What is a port number?
Page 6
Answer
A port number is a number that identifies a network application running on a host.
11
Question
What are well-known server-side port numbers for HTTP?
Page 6
Answer
HTTP uses port 80.
12
Question
Why should unused ports be closed?
Page 6
Answer
To reduce attack surface, as a packet to an unused port will be received and processed by the network stack.
13
Question
What type of protocol is TCP?
Page 7
Answer
TCP is a connection-oriented protocol.
14
Question
Describe the three-way handshake in TCP connection establishment.
Page 7
Answer
The client sends a SYN segment; the server responds with a SYN-ACK segment; the client sends an ACK segment.
15
Question
What does the server send with the second segment in TCP handshake?
Page 7
Answer
The server sends a SYN-ACK segment with a special TCP segment.
16
Question
Why is the three-way handshake used in TCP?
Page 7
Answer
To establish a connection before data transfer and to offer reliable data transfer and congestion control services.
17
Question
What is the purpose of source and destination port numbers in a TCP segment?
Page 10
Answer
They are used for process-to-process delivery.
18
Question
What do the 32-bit sequence number and acknowledgment number fields in TCP do?
Page 10
Answer
They are used for error detection.
19
Question
What does the 4-bit header length field in a TCP segment specify?
Page 10
Answer
It specifies the length of the TCP header in 32-bit words.
20
Question
What is the purpose of the 16-bit receive window field in TCP?
Page 10
Answer
It indicates the number of bytes that the receiver will accept (used for flow control).
21
Question
What does the checksum field in a TCP segment do?
Page 10
Answer
It is used for error detection.
22
Question
How many bits does the flags field in TCP contain?
Page 11
Answer
The flags field contains 6 bits.
23
Question
What are URG and ACK flags used for in TCP?
Page 11
Answer
Used for connection setup and teardown.
24
Question
What does the PSH flag indicate in TCP?
Page 11
Answer
It indicates that the receiver should pass the data to the upper layer immediately.
25
Question
What is the purpose of the urgent pointer field in TCP?
Page 11
Answer
It indicates the end of the urgent data in this segment.
26
Question
What is HTTP?
Page 12
Answer
HTTP is a transfer protocol initially developed for the Web.
27
Question
What version of HTTP is discussed, and what RFC defines it?
Page 12
Answer
HTTP/1.1, defined in RFC 2616.
28
Question
Besides web, what other applications use HTTP?
Page 12
Answer
Instant messaging to transfer XML files and audio/video streaming.
29
Question
What are the only ports open for outbound communication in firewall configuration for HTTP?
Page 12
Answer
Ports 80 and 443.
30
Question
What does a web page consist of?
Page 14
Answer
A web page consists of a base HTML file with several referenced objects like JPEG images.