Chapter 5 (152-157, 174-183) Test 2

Question 1

What is the size of a ethernet message field?

Answer 1

-Ethernet has max packet size of 1492
-need to subtract size of the TCP header(24 bytes)
-subtract size of IPv4 header(24 bytes
-therefore the max packet size is 1444
-

Question 2

Describe the transport layer.

Answer 2

• links the application layer software in the application layer with the network
• segments large messages into smaller ones for transmission
• manages the session(end-to-end delivery of message.

Question 3

What does NAT do?

Answer 3

• network address translation

- translates private non-routable addresses to a routable IPv4 address.

Question 4

What are the three major functions performed by the transport layer?

Answer 4

• linkin the application layer to the network layer
• segmenting
• session management(end-to-end)

Question 5

Describe port addresses.

Answer 5

• each application layer software package has a unique port address.
• applications must tell TCP the application layer port address that is to receive the message.
• sending computer tells TCP the source and destination port address.

Question 6

What fields are the port addressed placed in the TCP segment?

Answer 6

-the first two fields.

Question 7

How many bits are port addresses?

Answer 7

-at bits.

Question 8

What are common well known ports?

Answer 8

http: port 80
FTP: port 21
Telnet: port 23
SMTP: port 25

Question 9

Describe segmenting.

Answer 9

• takes one outgoing message from the application layer and break it into a set of smaller segments for transmission through the network.
• also means to take incoming set of smaller segments from the network layer and reassemble them into one message for the application layer.

Question 10

Describe how TCP ensures all segments are received?

Answer 10

-Continues ARQ(chapter 4).

Question 11

What is the default segment size for transport layer?

Answer 11

• 356
• Transport layer at the sender negotiates with the transport layer at the receiver to settle on the best segment sizes to use.
• done by establishing a TCP connection between the sender and receiver.

Question 12

Describe a session.

Answer 12

-conversation between two computers.

Question 13

What are the two types of messaging?

Answer 13

• connection-oriented

- connectionless.

Question 14

Describe connection-oriented messaging

Question 15

Describe the three way hand shake.

Answer 15

• sender sends a SYN segment.
• server responds with an ACK and sends its own SYN
• client seands an ACK for server’s SYN

Question 16

Describe a SYN.

Answer 16

-usually a randomly generated number that identifies a packet.

Question 17

What does TCP use to ensure arrival of segments?

Answer 17

-continuous ARQ (sliding window).

Question 18

Describe the TCP four-way handshake.

Answer 18

• sender willl send FIN to inform the receiver that it is finished sending data
• server acknowledges with an ACK
• server then sends a FIN
• Sender sends an ACK.

Question 19

Describe conectionless messaging.

Answer 19

• each packet is treated separately and makes its own way through the network.
• no connection is established.
• sender sends packets as separate unrelated entitites.
• may arrive out of sequence so network layer will put sequence number on each packet..

Question 20

How big is the UDP packet?

Answer 20

-8 bytes.

Question 21

When is connectionless messaging used?

Answer 21

-when application data or message can fit into one single message.

Question 22

Give examples of application layer software that uses TCP?

Answer 22

-HTTP, SMTP, FTP, Telnet.

Question 23

What applications use UDP?

Answer 23

-DHCP, routing control messages(RIP), network management(SNMP).

Question 24

Describe QOS.

Answer 24

• quality of service.
• connection oriented messaging in which different connections are assigned different priorities.
• different classes of service are defined with different priorities.

Question 25

What happens when transport layer software attempts to establish a connection?

Answer 25

• specifies the class of service that the connection requires.
• when a connection is established, network ensures that no connections are established that exceed the maximum number of that class on a given circuit.

Question 26

Describe Resource Reservation Protocol(RSVP) and Real-Time Streaming Protocol(RTSP).

Answer 26

• permit application layer software to request connections that have certain minimum data transfer capabilities.
• used to create a connection and request a certain minimum guaranteed data rate.
• use Real-Time Transport Protocol(RTP) to send packets across the connection.

Question 27

What does RTP contain?

Answer 27

• info about sending app
• packet sequence number
• time stamp so that the data in the RTP packet can be synchronized with other RP packets.

Question 28

Does RTP replace TCP or UDP?

Answer 28

• no, combined with UDP.

- each relat time packet first created with RTP and then surrounded by a UDP datagram.

Question 29

What does a router do when it receives a frame?

Answer 29

-peforms error checking and sends an acknowledgement.

Question 30

What transport layer protocol does DNS use?

Answer 30

-UDP.

Question 31

What does the network layer provide?

Answer 31

-addressing and routing.