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1 TCP Yoshifumi Nishida

2 Contents Part1: TCP Part2: TCP Part3: TCP Part4: Part5: TCP Part6:

3 TCP TCP TCP

4 Transmission Control Protocol IP TCP application TCP UDP IP DataLink header IP header TCP header TCP Data

5 TCP 16-bit source port number 4bit header length 32-bit sequence number 32-bit acknowledgement number reserved (6 bits) URG ACK PSH RST SYN FIN 16-bit TCP checksum options (if any) data (if any) 16-bit destination port number 16-bit window size 16-bit urgent pointer TCP : RFC793.. RFC2581..

6 TCP TCP UNIX Application TCP

7 Piggyback A feedback information B shutdown

8 (1) negotiate MTU (Max Segment Size) A B

9 (2) IP : ( , 21) - ( , 20) ( , 21) - ( , 21) TCP

10 (3) 3way handshake (SYN) (ACK) 3 client server SYN SYN, ACK ACK

11 (4) active close ACK (2MSL) ACK passive close ACK FIN active close client FIN server Active Close ACK FIN Passive Close ACK

12 TCP CLOSE (send FIN) (5) SYN RECEIVED FIN WAIT 1 FIN WAIT 2 passive OPEN (create TCB) receive SYN (send SYN, ACK) receive ACK of SYN (no action) receive ACK of FIN (no action) CLOSED LISTEN ESTABLISHED CLOSE (delete TCB) SEND (send SYN) receive SYN (send ACK) CLOSE (send FIN) receive FIN (send ACK) receive FIN (send ACK) CLOSING active OPEN (create TCB, send SYN) SYN SENT receive SYN, ACK (send ACK) CLOSE WAIT CLOSE (send FIN) LAST ACK receive FIN (send ACK) TIME WAIT receive ACK of FIN (no action) timeout at 2MSL (delete TCB) receive ACK of FIN (no action) CLOSED

13 (6) client SYN SENT ESTABLISHED SYN SYN,ACK ACK server SYN_RCVD ESTABLISHED FIN_WAIT_1 FIN_WAIT_2 TIME_WAIT FIN ACK FIN ACK CLOSE_WAIT LAST_ACK CLOSED

14 (1) + Application (2500 byte) TCP (Initialseqno 10000)

15 (ACK) (1) seqno Data Data Data Data Data 2000 ACK 2000 Data ACK 1000

16 (2) IPv4 IPv6 IP 32bit sender IP address 32bit receiver IP address 0 proto number TCP segment length

17 (3)

18 (3) ACK Sender Reciever Sender Reciever data data ack ack window size = 1 window size = 4

19 TCP Nagle TCP TCP

20 TCP (berkley 500msec) 2MSL (berkley 200msec) Nagle

21 expire expire RTT(Round Trip Time) RTT Data ACK

22 RTT Timer RTT Data ACK RTT : rtt : srtt srtt = srtt + (1 - ) * rtt 0.9

23 rto = 2 srtt rto = rtt

24 ( ) 0 ACK expire Sender Receiver ACK, window = 0 ACK, window = byte Data

25 probe Web

26 2MSL MSL(Max Segment Lifetime): ACK 2MSL RFC

27 ACK ACK PiggyBack ACK ACK Timer Timer Data Data RTT RTT

28 Nagle (1) telnet rlogin ACK

29 Nagle (2) application Sender Data kernel Reciever Data Data ACK Data Sender application kernel Data Data Data ACK Reciever

30 (RFC813) 1/2 1/2

31 TCP TCP SYN : ACK : ACK FIN : Push RST

32 Push Sender Reciever application kernel kernel application Without Push With Push

33 RST TCP listen port RST RST Close RST Close Listen

34 (1)

35 (2) TCP header TCP Data

36 TCP TCP

37 : 1980 : 1980 : 1990 :

38 (1) IP

39 (2)

40 (3)

41 TCP

42 1988 TCP Tahoe Fast Retransmit 1990 Reno Fast Recovery 1996 NewReno Fast Recovery

43 TCP (1) TCP

44 TCP (2) (cwnd) min( ) ACK ACK

45 TCP (3) 1/2 ssthresh ( ) cwnd 1/2 cwnd ( ) cwnd < ssthresh cwnd > ssthresh

46 Fast Retransmit Tahoe Reno Fast Recovery Data 1000 Data 1500 Data 2000 Data 2500 Data 3000 ACK 1500 ACK 1500 ACK 1500 Data 1500

47 Fast Recovery (1) Tahoe Fast Retransmit =1 Fast Recovery Fast Retransmit 50%

48 Fast Recovery (2) cwnd ACK cwnd ssthresh ( 1/2)

49 Tahoe Window Size Limit Optimal ssthresh Time Reno,NewReno Window Size Limit Optimal ssthresh Time

50 TCP ssthresh < windowsize < limit

51 sender receiver data path sender receiver ack path

52 Path MTU discovery SACK( )

53 TCP TCP / RTT RFC Mbps, RTT % RTT

54 = X TCP X bit X 14 : ^14 = 1,073,725,440 3way handshake client SYN scale=x server SYN, ACK scale=y scale=x scale=y ACK

55 RTT RTT

56 Path MTU discovery DF(Don t Fragment) ICMP DF MSS MSS 10 (RFC1191) MSS MTU

57 SACK(Selective Acknowledgement) RFC2018 TCP SACK Permitted Option SACK option 3way handshake negotiate SYN SACK Option

58 4 SACK option format KIND LEN Left Edge of First Block Right Edge of First Block Left Edge of n th Block Right Edge of n th Block

59 SACK : MSS ,6500,7500 lost Trigger Segemnt 5000 ACK st block Left Right 2nd block Left Right 3rd block Left Right 5500 (lost) (lost) (lost)

60 Pittuburgh Supercomuting center OS Win95 Win98 WinNT3.5/4.0 FreeBSD3.3 SunOS4.1 PMTU RFC1323 SACK YES NO NO YES YES YES YES NO NO YES YES NO NO NO NO Solaris2.6 YES YES YES Solaris7 YES YES YES

61 TCP Sequence number attack SYN flood Attack TCP IPsec filtering

62 Sequence number attack (1) TCP Sequence TCP X SYN A 1 A ACK B 3 SYN B,ACK A 2 B

63 Sequence number attack (2) Sequence Sequence 1 1 Sequence 4 src adr, src port, dst adr, dst port

64 (DoS) target SYN SYN flood attack (1) half open TCP connection cracker target SYN SYN, ACK Half open

65 SYN flood attack (2) 3way handshake timeout queue half open connection SYN

66 Explicit Congestion Notification Initial Large Window TCPVegas NewReno Rate-Halving TCPfriendly

67 ECN (Explicit Congestion Notification) ECN congestion IP TOS field 2bit RFC2481 ECT(ECN Capable Transport) Transport ECN CE(Congestion Experience) Sender Router Receiver CE bit

68 ECN TCP (1) TCP header 2 bit RFC2481 Reserved field 2bit ECN echo Congestion Window Reduce ECN echo Sender CWR Router CE bit Receiver ECN echo

69 ECN TCP (2) Handshake ECN Sender: ECN echo CWR SYN Receiver: ECN echo SYN + ACK TCP sender reserved field echo back client SYN ECN echo, CWR server SYN, ACK ECN echo ACK

70 ECN TCP (3) Receiver: CE ACK ECN echo Sender: Packet Loss CWR Receiver: CWR CE ACK ECN echo Sender CWR Router CE bit Receiver

71 Large Initial Window (1) RFC MSS 1 RTT HTTP

72 Large Initial Window (2) min(4 * MSS, max(2 * MSS, 4380) MSS 1095 : 4 * MSS MSS : 4380 MSS 2190 : 2 * MSS

73 TCPVegas TCPVegas (1) Brakmo TCP TCPVegas

74 TCPVegas (2) TCPVegas Actual Throughput Expected Throughput Actual < expected Actual > expected Actual = expected

75 NewReno RFC2582 MIT Hoe TCP Fast Retransmit,Fast Recovery 1RTT Reno Fast Retransmit NewReno Fast Retransmit Reno aggressive

76 Rate Halving MIT Hoe, PSC Mathis Fast recovery 1/2 Rate halving adjust 2ACK 1 self-clocking 50% burst

77 TCPfriendly ACIRI S.Floyd TCP UDP UDP UDP TCP TCP bandwidth = 1. 3MTU RTT Loss UDP flow flow

78 TCP SACK, ECN, (NewReno) Rate halving, Vegas CBQ, Diffserv TCP friendly Congestion Manager TCP

79 TCP RFC For More Information RFC793.. RFC813.. Silly Window Syndrome RFC Host Requirement RFC Extention for high performance RFC Large Initial Window RFC ECN RFC Congestion Control RFC NewReno algorithm IETF WG TCP Implementation (tcpimpl) TCP Over Satellite (tcpsat) Performance Implications of Link Characteristics (pilc)

橡c03tcp詳説（３／２４修正版）.PDF

橡c03tcp詳説（３／２４修正版）.PDF 1 1 2 TCP 1 3 TCP 9 4 TCP 15 5 21 6 TCP 25 7 27 TCP 1 TCP Windows98 Linux Solaris TCP(Transmission Control Protocol) IP TCP UDP UDP TCP UDP TCP 1 TCP RFC793 RFC2581 TCP 4-1 - DataLink header IP header