Transport Layer - Freie Universität Berlin

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Timer Management with TCP ● How to set TCP timeout value? ● Longer than RTT ● But RTT varies ● Too short: premature timeout ● Unnecessary retransmissions ● Too long: slow reaction to segment loss ● How to estimate RTT? ● SampleRTT: measured time from segment transmission until ACK receipt ● Ignore retransmissions ● SampleRTT will vary, want estimated RTT “smoother” ● Average several recent measurements, not just current SampleRTT Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 8: Transport Layer 8.64
Timer Management with TCP: Retransmission Timer ● Solution: dynamic algorithm, which adapts the timer by current measurements of the network performance. ● Algorithm of Jacobson (1988) ● TCP manages a variable RTT (Round Trip Time) for each connection ● RTT is momentarily the best estimation of the round trip time ● When sending a segment, a timer is started which measures the time the acknowledgement needs and initiates a retransmission if necessary. ● If the acknowledgement arrives before expiration of the timer (after a time unit sampleRTT), RTT is updated: ● a is a smoothing factor, typically 0.875 RTT = a × RTT + (1 – a) × sampleRTT ● The choice of the timeout is based on RTT Timeout = b × RTT ● At the beginning, b was chosen as 2, but this was too inflexible Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ Telematics ▪ Chapter 8: Transport Layer 8.65
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Telematics Chapter 8: Transport Lay
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Design Issues Univ.-Prof. Dr.-Ing.
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Services Provided to the Upper Laye
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Transport Service Primitives ● Pr
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Transport Service Primitives ● A
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Transport Protocol: Addressing ●
Page 13 and 14: Transport Protocol: Addressing ●
Page 15 and 16: Transport Protocol: Connection Esta
Page 17 and 18: Transport Protocol: Connection Rele
Page 19 and 20: Transport Protocol: Connection Rele
Page 21 and 22: Transport Protocol: Multiplexing
Page 23 and 24: Transport Protocol: Crash Recovery
Page 25 and 26: Transport Protocols in the TCP/IP R
Page 27 and 28: User Datagram Protocol (UDP) Univ.-
Page 29 and 30: UDP Header ● Source Port, Destina
Page 31 and 32: User Datagram Protocol (UDP) Socket
Page 33 and 34: Example: Java Client (UDP) import j
Page 35 and 36: Transmission Control Protocol (TCP)
Page 37 and 38: TCP as a Reliable Connection If the
Page 39 and 40: TCP: Overview RFCs: 793, 1122, 1323
Page 41 and 42: Socket Programming in TCP Server si
Page 43 and 44: Socket programming in TCP Server (o
Page 45 and 46: Example: Java Server (TCP) import j
Page 47 and 48: TCP-based Applications File transfe
Page 49 and 50: The TCP Header ● Source and Desti
Page 51 and 52: TCP Pseudo Header ● Checksum: ser
Page 53 and 54: TCP Connection Management: 1. Conne
Page 55 and 56: TCP Connection Management: 2. Data
Page 57 and 58: TCP Connection Management TCP clien
Page 59 and 60: States during a TCP Session State D
Page 61 and 62: Timer Management with TCP ● TCP u
Page 63: Timer Management with TCP: Example
Page 67 and 68: Timer Management with TCP: Retransm
Page 69 and 70: Timer Management with TCP: Retransm
Page 73 and 74: TCP Sender Events ● Data received
Page 75 and 76: TCP Retransmission Scenarios SendBa
Page 77 and 78: TCP ACK generation [RFC 1122, RFC 2
Page 79 and 80: TCP Flow Control: Sliding Window
Page 81 and 82: “Silly Window” Syndrome Header
Page 83 and 84: Flow Control: Network Bottlenecks C
Page 85 and 86: Principles of Congestion Control
Page 87 and 88: Causes/costs of congestion: Scenari
Page 89 and 90: Causes/costs of congestion: Scenari
Page 91 and 92: Approaches towards congestion contr
Page 93 and 94: Case study: ATM ABR congestion cont
Page 95 and 96: TCP congestion control: additive in
Page 97 and 98: TCP Slow Start ● When connection
Page 99 and 100: TCP Slow Start ● When connection
Page 101 and 102: Refinement: Inferring loss ● Afte
Page 103 and 104: Fast Retransmit Timeout Host A Time
Page 105 and 106: Fast Retransmit and Fast Recovery
Page 107 and 108: Summary: TCP Congestion Control ●
Page 111 and 112: TCP Futures: TCP over “long, fat
Page 113 and 114: TCP Fairness ● Fairness goal: if
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Fairness (more) ● Fairness and UD
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TCP in Wireless Networks ● Theore
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TCP and Security: SYN-Flood ● Dur
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Some Tools Univ.-Prof. Dr.-Ing. Joc
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Some Tools ● TTCP - Test TCP ●
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Stream Control Transmission Protoco
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SCTP Multi-Homing ● Ability for a
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SCTP Packet Format ● Common Heade
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SCTP Chunks ● Type (Examples) ●
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SCTP DATA Chunk ● Transmission Se
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Datagram Congestion Control Protoco
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DCCP vs. TCP/UDP ● Choice of cong
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DCCP Generic Header ● Ports ● 1
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DCCP State Diagram a la RFC +------
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Transport Layer - Freie Universität Berlin

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