Net. 1: Ch 7 Transport Layer

Question 1

segment

Answer 1

PDU of transport layer

Question 2

responsibilites of transport layer

Answer 2

Track individual communications between apps on source and destination hosts.
Segmenting Data for managability and reassembly.
Indentify proper app for each communication stream.

Question 3

TCP Basic Operations of Reliability

Answer 3

Tracking transmitted data segments.
Acknowledge received data.
Retransmit any unacknowledged data

Question 4

TCP Services

Answer 4

Establishes session connections on both sides before Tx begins.
Same order delivery.
Reliable delivery.
Flow Control: manages data delivery when congested on host.

Question 5

stateful

Answer 5

refers to TCP’s ability to keep track of conversations within a session. tracks the state of the communications session.

Question 6

UDP Features

Answer 6

1. Connectionless.
2. Unreliable delivery - best-effort
3. No ordered data reconstrunction.
4. No flow control.

Question 7

port numbers

Answer 7

values that allow a system to distinguish between multiple apps over a single connection.

Question 8

socket

Answer 8

combination of IP address and port number.

Question 9

socket pair

Answer 9

2 sockets, one for source and one for destination.

Question 10

Port Number Ranges

Answer 10

0 to 1023: Well Known Port: Reserved for specfic applications.
1024 to 49151: Registered Ports: assigned to user processes or applications.
49152 to 65535:Dynamic/Private/Ephemeral:

Question 11

FTP Port

Answer 11

21 TCP

Question 12

Telnet Port

Answer 12

23 TCP

Question 13

SMTP Port

Answer 13

25 TCP

Question 14

HTTP Port

Answer 14

80 TCP

Question 15

IMAP Port

Answer 15

143 TCP

Question 16

IRC Port

Answer 16

194 TCP

Question 17

SHTTP Port

Answer 17

443 TCP

Question 18

TFTP Port

Answer 18

69 UDP

Question 19

RIP Port

Answer 19

520 UDP Routing Information Protocol

Question 20

Doom Port

Answer 20

666 TCP/UDP

Question 21

DNS Port

Answer 21

53 TCP/UDP

Question 22

SNMP Port

Answer 22

161 TCP/UDP

Question 23

AOL Instant Messenger Port

Answer 23

531 TCP/UDP

Question 24

netstat use on transport layer

Answer 24

used to display TCP connections.

Question 25

Three Way Handshake

Answer 25

1. Establish that destination is present on network
2. Verifies that destination has active services and is accepting requests with the port initiating client is using.
3. Inform destination that source intends to establish commnication session on that port.

Question 26

3 Steps in TCP 3 way handshake

Answer 26

1. Source requests source to dest. session with server.(SYN)
2. Dest. acknowledges request and request destination to source session.(ACK,SYN)
3. Source acknowledges dest to source session.(ACK)

Question 27

TCP Process Fields

Answer 27

URG -urgent
PSH - push function
SYN - synchronize sequence numbers
ACK - acknowledge field significant
RST - reset connection
FIN - no more data from sender.

Question 28

FIN Flag Notes

Answer 28

Used to terminate session

Each side must send FIN and acknowledge the other side’s FIN.

Question 29

Termination Handshake

Answer 29

Source: Sends FIN
Dest: responds with ACK , FIN
Source: respongs to Dest FIN with ACK.

Question 30

initial sequence number

Answer 30

initial value for bytes for this session Tx’d to receiving application.
- this sequence # is incremented by # of bytes Tx’d
- provides unique sequence # for reassembling segment.
-SEQ and ACK used to create:
SEQ1 ACK1 : sends 10 bytes: Dest: SEQ1 ACK11(dest tells source it expects next value of 11)

Question 31

window size

Answer 31

the amount of data that can beTx’d by the source before an ACK must be received: 16 bit field in header

Question 32

SACKS

Answer 32

Selective acknowledgement system. system used on both sides of comms. that allow only missing segments to be re Tx’d

Question 33

UDP

Answer 33

User Datagram Protocol

• transaction based: means sends the data when it needs to regardless of connection on other side.
• reassembles in order received: lets applications resequence if necessary.

Question 34

UDP Candidates

Answer 34

1. Can tolerate loss, but little or no delay.
2. Applications with simple request/reply transactions.
3. Unidirectional comm. where reliability is not required or can be handled by application