The Bits and Bytes of Computer Networking: Week 3

Question 1

What is the Transport Layer?

Answer 1

Allows traffic to be directed to specific network applications

Question 2

what is the Application Layer?

Answer 2

Allows these applications to communicate in a way they understand

Question 3

What is multiplexing (transport layer)?

Answer 3

Nodes on the network have the ability to direct traffic toward many different receving services

Question 4

What is de-multiplexing?

Answer 4

Same concept as multiplexing, just at the receiving end. It’s taking traffic that’s all aimed at the same node and delivering it to the proper receiving service

Question 5

What is a port?

Answer 5

A 16-bit number that’s used to direct traffic to specific servic es running on a networked computer. Ex. port 80 used as the traditional port for HTTP?unencrypted web traffic. 10.1.1.100:80 (Socket address/socket port)

Port 21 is commonly used for FTP servers

Question 6

What is a TCP segment?

Answer 6

Made up of a TCP header and a data section

Question 7

What is a destination port?

Answer 7

The port of the service the traffic is intending for

Question 8

What is a source port?

Answer 8

A high numbered port chosen from a special section of ports know as ephemeral ports

Question 9

What is a sequence number?

Answer 9

A 32-bit number that’s used to keep track of where in a sequence of TCP segments this one is expected to be. In a TCP heather, the sequence number is used to keep track of which segment out of many this particular segment may be.

Question 10

What is a acknowledgement number?

Answer 10

The number of the next expected segment

Question 11

What is the data offset field?

Answer 11

A four-bit number that communicates how long the TCP header this segment is

Question 12

What is the TCP Window?

Answer 12

Specifies the range of sequence numbers that might be sent before an acknowledgement is required

Question 13

What is a checksum?

Answer 13

Operates just like the checksumn fields at the IP and ethernet level

Question 14

What is the urgent pointer field?

Answer 14

Used in conjunction with one of the TCP control flags to point out particular segments that might be more important than others

Question 15

What are Options?

Answer 15

Rarely used but sometimes used for more complicated flow control protocols

Question 16

What is padding?

Answer 16

Just a sequence of zeros to ensure the data payload section begins at the expected location

Question 17

What are the TCP control flags?

Answer 17

URG (Urgent): A value of one here indicates that the segment is considered urgent and that the urgent pointer field has more data about this

ACK (Acknowledged): A value of one in this field means that the acknoledgement number field should be excamined

PSH (Push): The transmitting device wants the receiving device to push currently-buffered data to the application on the receiving end as soon as possible

RST (reset): One of the sides in a TCP connection haven;t been able to properly recover from a series of missing or malformed segments

Question 18

What is a buffer?

Answer 18

A computing technique where a certain amount of data is held somewhere before being sent somewhere else. IN terms of TCP it’s used to send large chunks of data more efficiently. By keeping some amount of data in a buffer TCP can deliver more meaningful chunks of data to the program waiting for it. The push flag would be the listening program to respond to the data/info immediately