Article Directory
- A transport layer Why can not achieve reliable data transmission
- Second, how reliable data transport layer for transmission
- Third, reliable transport protocol - stop - other agreements
- Fourth, reliable data transfer protocol - Protocol Pipeline
- Write it twice, no computer is really flawed, and finally Thank you for reading
A transport layer Why can not achieve reliable data transmission
Two transport layer protocol is a TCP (reliable transport protocol), is a UDP (unreliable transport protocol).
The five model, the transport layer is the network layer receives data, i.e. the data (segment) received by the TCP IP transmission, and the IP service only provides unreliable transport, the transport layer without intervention a case where the received data is not reliable
Second, how reliable data transport layer for transmission
About the confirmation mechanism, the receiver receives the data packet sender, sends ACK packet has been received indicates otherwise transmitting the NCK (generally not used), as FIG.
Third, reliable transport protocol - stop - other agreements
1. About + ACK packet retransmission error detection +
ACK acknowledgment packet data itself, bit transitions can occur, it is necessary to add error detection. If errors are found, according to the wrong inference, the sender will retransmit the data packets
2. For just a bit as the serial number
The characteristics of stop-peer protocol, each sender sends a packet transmission stops, waits to receive confirmation, therefore, the order of 0 and 1 satisfy this demand, so just for a bit number.
3. With regard to repeatedly send ACK + sequence number instead of NCK
As mentioned above, in practice is not to use the NCK, repeatedly transmits ACK + sequence number may be used, as shown
wherein data PKT0 or represents, or represents ACK0 acknowledgment packets
when the PKT1 error detection, the receiver discards this packet, and transmits ACK0, the sender will resend the time PKT1
4. With regard to the retransmission data packet PKT
(1) transmits a data packet loss PKT
packet loss exceeds the time set by the timer, the sender retransmits PKT1
(2) the sender does not receive acknowledgment packets ACK
(3) receive a confirmation packet receiving side after the timeout
time the receiver will receive and discard duplicate packets
Fourth, reliable data transfer protocol - Protocol Pipeline
4.1 pipeline agreement - sliding window protocol
When the sliding window?
Either the sender or receiver window window, are the left-most (based ordinal number) to obtain confirmation or submit a sliding window in the window
4.1.1 Protocol sliding window protocol --GBN
Characterized by the largest number of the receive window to a buffer, it does not receive data packets arrive out of order will be discarded.
4.1.2 Protocol sliding window protocol --SR
SR protocol independent packet acknowledgment, this mechanism has confirmed that avoids retransmission of data packets
Write it twice, no computer is really flawed, and finally Thank you for reading
