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TCP and FTP Internet Engineering. 1 Protocol of transport layer Reliability ( guarantee packet arrives to destination ) –Retransmission control Use for.

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Presentation on theme: "TCP and FTP Internet Engineering. 1 Protocol of transport layer Reliability ( guarantee packet arrives to destination ) –Retransmission control Use for."— Presentation transcript:

1 TCP and FTP Internet Engineering

2 1 Protocol of transport layer Reliability ( guarantee packet arrives to destination ) –Retransmission control Use for File ・ Mail ・ Web Transfer Application layer FTP, CBR HTTP, SMTP Transport layer TCPUDP Network layer IP Physic, data-link layer Ethernet TCP (Transport Control Protocol) FTP (File Transfer Protocol) POP (Post Office Protocol) SMTP (Simple Mail Transfer Protocol) IMAP (Internet Message Access Protocol) HTTP (Hyper Text Transfer Protocol) FTP POP SMTP IMAP HTTP

3 Internet Engineering 2 Hierarchy Architecture senderreceiver data TCP header IP header Ethernet Frame header IP header TCP header addition analysis Communication medium ( LAN cable ・ Optical cable ・ wireless ) Send outrevceiv Application layer Transport layer Network layer Physic, data-link layer

4 Internet Engineering 3 TCP Packet, TCP Header DataIP Header Ethernet Header TCP Header

5 Internet Engineering 4 TCP Header Sequence number –Indicate the position of sent data –Increased by the number of bytes whenever data sent ( ※ In ns-2, it is increased 1 when a data is sent ) Acknowledge (ACK) number –Sequence number of data should be received next This means that the receiver received all packets whose sequence numbers are less than the ACK If the sequence number of next data equals the replied ACK number, normal communication is done ( ※ In ns-2, the ACK number is the maximum sequence number of data received cumulatively. It means that, if the sequence number of sent data equals ACK number, the communication has no fault)

6 Internet Engineering 5 Reliability Insurance by ACK Data Packet Sender Receiver 1 2 Next is 2 Next is 3 3 Next is 4 Sequence number ACK Number ACK It is inefficient to acknowledge individually each segment received.  Send a number of segments at once ?

7 Internet Engineering 6 Implement Window Control No waiting ACK for sent segment but send a number of segment Data packet Sender Receiver Next is Sequence number ACK number ACK Window ※ Window size : size of segments can be sent without waiting for ACK

8 Internet Engineering 7 Improvement speed by Window Control Adjust transmission rate by changing window size Data Packet Sender Receiver 1 23 Sequence number ACK number ACK Sender Receiver Sequence number ACK Data Packet Window Size = 1 segment Window Size = 4 segments Next is 2 34 ACK number Next is

9 Internet Engineering 8 Data Packet Maximum Window Size Window Size = 4 segments Sender Receiver Sequence Number ACK number ACK Window Maximum Window Size Buffer Size of Receiver (rwnd: Receiver’s Window) Next is

10 Internet Engineering 9 Retransmission Control (Time Out) Sender Receiver Packet loss period RTO ( Retransmission Time Out) 1 1 Next is 2 2 If the ACK for a packet isn’t responded within RTO, that packet is considered loss  Retransmission

11 Internet Engineering 10 Retransmission Control (duplicate ACK) 送信側 受信側 1 7 If receive three same ACKs then corresponding packet is considered loss  retransmission Three duplicate ACKs If receive third duplicate ACKs  Retransmission Next is

12 Internet Engineering 11 Experiment FTP/TCP (Bottleneck link) Bandwidth: Bw 40Mbps FTP TCP Agent NetworkRouter Download TCPSink Agent Network


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