3.4 Flashcards
1
Q
What is the USP protocol? (Protocol A)
A
Unrestricted Simple Protocol
Sender (Repeats forever all steps)
- Get App Layer data from socket
- Construct Transport Layer segment with header
- Give segment to Network Layer to transmit
Receiver (Repeats forever all steps)
- Wait for segment from Network Layer
- Process segment, remove Transport Layer header
- Direct message to appropriate AL socket
2
Q
What is the SAW protocol? (Protocol B)
A
Stop and Wait Protocol
Sender (Repeats forever all steps)
- Get App Layer data from socket
- Construct Transport Layer segment with header
- Give segment to Network Layer to transmit
- Wait for Ack from other end (via NL)
Receiver (Repeats forever all steps)
- Wait for segment from Network Layer
- Process segment, remove Transport Layer header
- Direct message to appropriate AL socket
- Construct Ack segment
- Give Ack to NL to transmit
3
Q
What is the PNA protocol? (Protocol C)
A
Positive Negative ACKS
(handles corrupted data, but not acks)
Sender (Repeats forever all steps)
- Get App Layer data from socket
- Construct Transport Layer segment with header
- Give segment to Network Layer to transmit
Receiver (Repeat all steps for ever) -Wait for segment from NL -Process segment, compute checksum -If valid checksum Then remove TL header Deliver data to AL_Socket Construct Ack Give Ack to NL to transmit
Else Discard Segment
Construct Nak
Give Nak to NL to transmit
4
Q
What is the PAR protocol? (Protocol D)
A
Positive Ack with retransmission
(handles both corrupted data and acks)
Sender (Repeat forever) Construct TL segment with header (including seqnum) give segment to NL to transmit set timer wait for event If valid ack cancel timer Get next Al from socket update seqnum
Receiver -Wait for segment from NL -Process segment, compute checksum -If valid checksum Then If seqnum = expected Then remove TL header Deliver data to AL_Socket Construct Ack Give Ack to NL to transmit update expected seqnum Else Discard Segment Construct Nak Give Nak to NL to transmit Else discard segment