CSC 401 Data and Computer Communications Networks

Size: px
Start display at page:

Download "CSC 401 Data and Computer Communications Networks"

Transcription

1 CSC 401 Data and Computer Communications Networks Transport Layer TCP Connection Management & Congestion Control Sec 3.6 and 3.7 Prof. Lina Battestilli Fall 2017

2 Transport Layer Chapter 3 Outline 3.1 Transport-layer Services 3.2 Multiplexing and Demultiplexing 3.3 Connectionless Transport: UDP 3.4 Principles of Reliable Data Transfer 3.5 Connection-oriented Transport: TCP segment structure, reliable data transfer, flow control, connection management 3.6 Principles of Congestion Control 3.7 TCP Congestion Control

3 Connection Management before exchanging data, sender/receiver handshake : agree to establish connection (each knowing the other willing to establish connection) agree on connection parameters application connection state: ESTAB connection variables: seq # client-to-server server-to-client rcvbuffer size at server,client network application connection state: ESTAB connection Variables: seq # client-to-server server-to-client rcvbuffer size at server,client network Socket clientsocket = newsocket("hostname","port number"); Socket connectionsocket = welcomesocket.accept(); 7

4 Agreeing to establish a connection 2-way handshake: Q: Will 2-way handshake always work in network? ESTAB choose x ESTAB Let s talk OK req_conn(x) ack_conn(x) ESTAB ESTAB variable delays retransmitted messages (e.g. req_conn(x)) due to message loss message reordering can t see other side 8

5 Agreeing to establish a connection 2-way handshake failure scenarios: choose x retransmit req_conn(x) req_conn(x) ack_conn(x) ESTAB choose x retransmit req_conn(x) req_conn(x) ack_conn(x) ESTAB ESTAB client terminates req_conn(x) connection x completes server forgets x ESTAB retransmit data(x+1) client terminates data(x+1) connection x completes req_conn(x) accept data(x+1) server forgets x half open connection! (no client!) ESTAB data(x+1) ESTAB accept data(x+1) 9

6 TCP 3-way handshake client state LISTEN SYNSENT ESTAB choose init seq num, x send TCP SYN msg received SYNACK(x) indicates server is live; send ACK for SYNACK; this segment may contain client-to-server data SYNbit=1, Seq=x SYNbit=1, Seq=y ACKbit=1; ACKnum=x+1 ACKbit=1, ACKnum=y+1 choose init seq num, y send TCP SYNACK msg, acking SYN received ACK(y) indicates client is live server state LISTEN SYN RCVD ESTAB 10

7 TCP 3-way handshake: FSM closed Socket connectionsocket = welcomesocket.accept(); SYN(x) SYNACK(seq=y,ACKnum=x+1) create new socket for communication back to client L listen Socket clientsocket = newsocket("hostname","port number"); SYN(seq=x) SYN rcvd SYN sent ACK(ACKnum=y+1) L ESTAB SYNACK(seq=y,ACKnum=x+1) ACK(ACKnum=y+1) 11

8 TCP: closing a connection client state server state ESTAB ESTAB clientsocket.close() FIN_WAIT_1 FIN_WAIT_2 can no longer send but can receive data wait for server close FINbit=1, seq=x ACKbit=1; ACKnum=x+1 can still send data CLOSE_WAIT TIMED_WAIT timed wait for 2*max segment lifetime FINbit=1, seq=y ACKbit=1; ACKnum=y+1 can no longer send data LAST_ACK CLOSED CLOSED client, server each close their side of connection, send TCP segment with FIN bit = 1 respond to received FIN with ACK, on receiving FIN, ACK can be combined with own FIN 12

9 TCP State Diagram Opening a connection Sending & Receiving Closing a connection 13

10 Transport Layer Chapter 3 Outline 3.1 Transport-layer Services 3.2 Multiplexing and Demultiplexing 3.3 Connectionless Transport: UDP 3.4 Principles of Reliable Data Transfer 3.5 Connection-oriented Transport: TCP segment structure, reliable data transfer, flow control, connection management 3.6 Principles of Congestion Control 3.7 TCP Congestion Control

11 Principles of congestion control congestion: informally: too many sources sending too much data too fast for network to handle different from flow control! manifestations: lost packets (buffer overflow at routers) long delays (queueing in router buffers) top-10 list of important networking topics! 16

12 Time Scales of Congestion 17

13 What causes congestion? A D(t) 12Mbps C B Cumulative Bits Q(t) A 1 (t) + A 2 (t) D(t) What would be a fair way to share the capacity? What if the buffer is finite? t 18

14 Another example A Mbps 12Mbps D B C Packets will be dropped How to prevent sending traffic, which will be dropped at a downstream router Not obvious how to split the links between the senders 19

15 Observations about Congestion 1. Congestion is inevitable, and arguably desirable. 2. Congestion happens at different time scales 3. If packets are dropped then retransmissions can make congestion even worse. resources are wasted upstream before the actual node where they were dropped 4. We need a definition of fairness, to decide how we want flows to share a bottleneck link. 20

16 Approaches towards Congestion Control end-end congestion control: no explicit feedback from network congestion inferred from end-system observed loss, delay approach taken by TCP network-assisted congestion control: routers provide feedback to end systems single bit indicating congestion (SNA, DECbit, TCP/IP ECN, ATM) explicit rate for sender to send at 21

17 Network-Assisted Congestion Control Example ATM ABR: available bit rate: elastic service if sender s path underloaded : sender should use available bandwidth if sender s path congested: sender throttled to minimum guaranteed rate RM (resource management) cells: sent by sender, interspersed with data cells bits in RM cell set by switches ( networkassisted ) NI bit: no increase in rate (mild congestion) CI bit: congestion indication Sec in textbook RM cells returned to sender by receiver, with bits intact RM cell data cell 22

18 Transport Layer Chapter 3 Outline 3.1 Transport-layer Services 3.2 Multiplexing and Demultiplexing 3.3 Connectionless Transport: UDP 3.4 Principles of Reliable Data Transfer 3.5 Connection-oriented Transport: TCP segment structure, reliable data transfer, flow control, connection management 3.6 Principles of Congestion Control 3.7 TCP Congestion Control

19 TCP Congestion Control TCP implements congestion control at the end-host. Reacts to events observable at the end host (e.g. packet loss). Exploits TCP s sliding window used for flow control. Tries to figure out how many packets it can safely have outstanding in the network at a time. 24

20 TCP Sliding Window LastByteAcked LastByteSent 25

21 TCP Sending Rate TCP sending rate (roughly): send window bytes, wait RTT for ACKS, then send more bytes Window Size rate ~ RTT bytes/sec 26

22 TCP History Timeline ARPAnet starts using TCP/IP 3-way handshake 1978 Van Jacobson & Karels, publish seminal TCP Congestion Control paper (Tahoe) BBR (Bottleneck and RTT) Congestion Control - by Google 1974 TCP and IP split 1983 into TCP/IP 1988 Fast recovery added (Reno) 2016 Internet begins to suffer congestion collapse C/2 l out l in C/2

23 Original TCP (before Tahoe) Original Implementation: Sender knows the flow control window size of the receiver On connection establishment, send a full window of packets Start a retransmit timer for each packet Problem: what if window is much larger than what network can support? 20Kbps Tahoe Improvements: Congestion window Timeout estimation Self-clocking Figure from Congestion Avoidance and Control, Van Jacobson and Michael Karels,

24 TCP Tahoe Congestion Window TCP varies the number of outstanding packets in the network by varying the window size: Window size = min{advertised window, Congestion Window} LastByteSent LastByteAcked the window is dynamic, function of perceived network congestion rwind based on the receiver buffer cwnd based on network congestion Q: How does the sender figure out the value for cwnd? 29

25 TCP is Self-Clocking Suppose congestion free, i.e., no loss occurring If ACK arrive then TCP will take that as indication that all is well along the path ACKs arrival rate used to clock the increase/decrease the size of the congestion window if ACKs arrive slowly then congestion window will be increased slowly if ACKs arrive fast then congestion window will be increased fast 30

26 TCP Congestion Control 1.Slow Start upon startup/timeout 2.Congestion Avoidance using AIMD in steady state Tahoe 3.Fast recovery to patch occasional loss Reno 31

27 RTT TCP Slow Start When connection begins, increase rate exponentially until first loss event: initially cwnd = 1 MSS double cwnd every RTT done by incrementing cwnd for every ACK received Host A Host B Summary: initial rate is slow but ramps up exponentially fast slow compared to prior approach time 32

28 Transition from Slow Start When should the exponential growth of the window end? Loss determined via Timeout cwnd = 1 ssthresh = cwnd/2 Slow Start begins again Reaching sshthresh Transition to Congestion Avoidance Loss determined via 3 Duplicate ACKs Fast retransmit Transition to Fast Recovery 33

29 TCP Congestion Control 1.Slow Start upon startup/timeout 2.Congestion Avoidance using AIMD in steady state Tahoe 3.Fast recovery to patch occasional loss Reno 34

30 TCP: Slow Start to Congestion Avoidance on Loss/Timeout event Ssthresh = 1/2 of cwnd just before loss event occured Sender has two parameters for congestion control ssthresh;initial value is bytes cwnd; initial value is MSS bytes (default is 536 bytes ) Tahoe: cwnd = 1 MSS Reno: cwnd = cwnd/2 35

31 cwnd: TCP sender congestion window size TCP Congestion Avoidance - AIMD Additive Increase, Multiplicative Decrease (AIMD) additive increase: multiplicative decrease: Until packet loss: increase cwnd by 1 MSS every RTT After packet loss: cwnd set to cwnd/2 additively increase window size. until loss occurs (then cut window in half) AIMD saw tooth behavior: probing for bandwidth 36

32 Transition from Congestion Avoidance When should linear increase of the window end? Loss/Timeout cwnd = 1 ssthresh = cwnd/2 Transition to Slow Start Loss/3 Duplicate ACKs Transition to Fast Recovery 38

33 TCP Congestion Control 1.Slow Start upon startup/timeout 2.Congestion Avoidance using AIMD in steady state Tahoe 3.Fast recovery to patch occasional loss Reno 39

34 TCP Fast recovery (Reno) When loss detected due to 3 duplicate ACKs, network still capable of delivering some segments cwnd = cwnd/2 set to half window then grows linearly Recommended but not required RFC

35 Transition from Fast Recovery Loss/Timeout cwnd = 1 ssthresh = cwnd/2 transition to Slow Start NEW ACK received cwnd = sstresh Transition to Congestion Avoidance 41

36 Summary: TCP Congestion Control L cwnd = 1 MSS ssthresh = 64 KB dupackcount = 0 timeout ssthresh = cwnd/2 cwnd = 1 MSS dupackcount = 0 retransmit missing segment dupackcount == 3 ssthresh= cwnd/2 cwnd = ssthresh + 3 retransmit missing segment duplicate ACK dupackcount++ slow start New ACK! new ACK cwnd = cwnd+mss dupackcount = 0 transmit new segment(s), as allowed cwnd > ssthresh L timeout ssthresh = cwnd/2 cwnd = 1 MSS dupackcount = 0 retransmit missing segment timeout ssthresh = cwnd/2 cwnd = 1 dupackcount = 0 retransmit missing segment fast recovery duplicate ACK new ACK cwnd = cwnd + MSS (MSS/cwnd) dupackcount = 0 transmit new segment(s), as allowed cwnd = ssthresh dupackcount = 0 congestion avoidance New ACK! New ACK cwnd = cwnd + MSS transmit new segment(s), as allowed. New ACK! duplicate ACK dupackcount++ dupackcount == 3 ssthresh= cwnd/2 cwnd = ssthresh + 3 retransmit missing segment 43

37 TCP Congestion Animation 44

38 TCP throughput macroscopic model Avg. TCP throughput is a function of window size and RTT? ignore Slow Start, assume always data to send W: window size (measured in bytes) where loss occurs avg. window size (# in-flight bytes) is ¾ W avg. throughput is 3/4W per RTT avg TCP thruput = 3 4 W RTT bytes/sec W W/2 45

39 TCP throughput more practical model Throughput in terms of segment loss probability, L, round-trip time RTT and maximum segment size MSS TCP throughput = MSS RTT L Note Inversely proportional to RTT if long RTT then low throughput Inversely proportional to loss rate if loss rate is high then low throughput The Macroscopic Behavior of the TCP Congestion Avoidance Algorithm, Mathis et al

40 TCP Futures: TCP over long, fat pipes Example: 1500 byte MSS, 100ms RTT, want 10 Gbps throughput requires W = 83,333 in-flight segments throughput in terms of segment loss probability, L TCP throughput = MSS RTT L to achieve 10 Gbps throughput, need a loss rate of L = (loss ever segments) a very small loss rate! new versions of TCP are needed for high-speed links! 47

41 TCP Innovation Many variants proposed summary in [Afanasyev 2010] TCP Vegas (RFC 2018, yr 1995) attempts to avoid congestion while maintaining good throughput, selective acknowledgments Others: TCP Hybla, TCP BIC, TCP CUBIC, Agile-SD TCP, TCP Westwood+, Compound TCP, etc. TCP Proportional Rate Reduction (RFC 6937, yr 2013) - window size after recovery is as close as possible to the slow start threshold. used as default in Linux kernels since ver 3.2 TCP Splitting (Performance Enhancing Proxy) summary in [Chen 2011] Used to solve TCP problems with large RTTs Breaks the end-to-end connection into multiple connections and using different parameters to transfer data across the different legs. end systems use standard TCP with no modifications 48

42 TCP Fairness fairness goal: if K TCP sessions share same bottleneck link of bandwidth R, each should have average rate of R/K TCP connection 1 TCP connection 2 bottleneck router capacity R 49

43 two competing sessions: Why is TCP fair? additive increase gives slope of 1, as throughout increases multiplicative decrease decreases throughput proportionally R equal bandwidth share loss: decrease window by factor of 2 congestion avoidance: additive increase loss: decrease window by factor of 2 congestion avoidance: additive increase Connection 1 throughput R In practice, smaller RTT connections can grab bandwidth more quickly have higher throughput 50

44 Fairness (more) Fairness and UDP multimedia apps often do not use TCP do not want rate throttled by congestion control instead use UDP: send audio/video at constant rate, tolerate packet loss Fairness, parallel TCP connections application can open multiple parallel connections between two hosts web browsers do this e.g., link of rate R with 9 existing connections: new app asks for 1 TCP, gets rate R/10 new app asks for 11 TCPs, gets R/2 51

45 Chapter 3: summary principles behind transport layer services: multiplexing, demultiplexing reliable data transfer flow control congestion control instantiation, implementation in the Internet UDP TCP next: leaving the network edge (application, transport layers) into the network core 52

46 References Some of the slides are identical or derived from 1. Slides for the 7 th edition of the book Kurose & Ross, Computer Networking: A Top-Down Approach, 2. Computer Networking, Nick McKeown and Philip Levis, 2014 Stanford University

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 10

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 10 CMPE 150/L : Introduction to Computer Networks Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 10 1 Midterm exam Midterm next Thursday Close book but one-side 8.5"x11" note is allowed (must

More information

TCP reliable data transfer. Chapter 3 outline. TCP sender events: TCP sender (simplified) TCP: retransmission scenarios. TCP: retransmission scenarios

TCP reliable data transfer. Chapter 3 outline. TCP sender events: TCP sender (simplified) TCP: retransmission scenarios. TCP: retransmission scenarios Chapter 3 outline TCP reliable 3.2 principles of reliable 3.3 connection-oriented flow 3.4 principles of congestion 3.5 TCP congestion TCP creates rdt service on top of IP s unreliable service pipelined

More information

TCP: Overview RFCs: 793,1122,1323, 2018, 2581

TCP: Overview RFCs: 793,1122,1323, 2018, 2581 TCP: Overview RFCs: 793,1122,1323, 2018, 2581 point-to-point: one sender, one receiver reliable, in-order byte steam: no message boundaries pipelined: TCP congestion and flow control set window size full

More information

Chapter 3- parte B outline

Chapter 3- parte B outline Chapter 3- parte B outline 3.1 transport-layer services 3.2 multiplexing and demultiplexing 3.3 connectionless transport: UDP 3.4 principles of reliable data transfer 3.5 connection-oriented transport:

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Slides adopted from original ones provided by the textbook authors. Transport

More information

Chapter III: Transport Layer

Chapter III: Transport Layer Chapter III: Transport Layer UG3 Computer Communications & Networks (COMN) Myungjin Lee myungjin.lee@ed.ac.uk Slides copyright of Kurose and Ross TCP: Overview RFCs: 793,1122,1323, 2018, 2581 point-to-point:

More information

CSC 4900 Computer Networks: TCP

CSC 4900 Computer Networks: TCP CSC 4900 Computer Networks: TCP Professor Henry Carter Fall 2017 Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles of reliable

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer Part c Congestion Control Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley Transport Layer 3-1 Chapter 3 outline 3.1 transport-layer

More information

CSC 401 Data and Computer Communications Networks

CSC 401 Data and Computer Communications Networks CSC 401 Data and Computer Communications Networks Transport Layer Connection Oriented Transport: TCP Sec 3.5 Prof. Lina Battestilli Fall 2017 Transport Layer Chapter 3 Outline 3.1 Transport-layer Services

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you can add, modify, and delete

More information

CSC 8560 Computer Networks: TCP

CSC 8560 Computer Networks: TCP CSC 8560 Computer Networks: TCP Professor Henry Carter Fall 2017 Project 2: mymusic You will be building an application that allows you to synchronize your music across machines. The details of which are

More information

Chapter III: Transport Layer

Chapter III: Transport Layer Chapter III: Transport Layer UG3 Computer Communications & Networks (COMN) Mahesh Marina mahesh@ed.ac.uk Slides thanks to Myungjin Lee and copyright of Kurose and Ross Principles of congestion control

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer 1 Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles of reliable data transfer 3.5 Connection-oriented

More information

rdt3.0: channels with errors and loss

rdt3.0: channels with errors and loss rdt3.0: channels with errors and loss new assumption: underlying channel can also lose packets (data, ACKs) checksum, seq. #, ACKs, retransmissions will be of help but not enough approach: sender waits

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these Powerpoint slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations;

More information

Chapter 3 outline. 3.5 Connection-oriented transport: TCP. 3.6 Principles of congestion control 3.7 TCP congestion control

Chapter 3 outline. 3.5 Connection-oriented transport: TCP. 3.6 Principles of congestion control 3.7 TCP congestion control Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles of reliable data transfer 3.5 Connection-oriented transport: TCP segment

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer Part b Connection-Oriented Transport Transport Layer 3-1 Chapter 3 outline 3.1 transport-layer services 3.2 multiplexing and demultiplexing 3.3 connectionless transport: UDP 3.4

More information

Computer Networking Introduction

Computer Networking Introduction Computer Networking Introduction Halgurd S. Maghdid Software Engineering Department Koya University-Koya, Kurdistan-Iraq Lecture No.10 Chapter 3 outline 3.1 transport-layer services 3.2 multiplexing and

More information

Chapter 3 outline. 3.5 Connection-oriented transport: TCP. 3.6 Principles of congestion control 3.7 TCP congestion control

Chapter 3 outline. 3.5 Connection-oriented transport: TCP. 3.6 Principles of congestion control 3.7 TCP congestion control Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles of reliable data transfer 3.5 Connection-oriented transport: TCP segment

More information

Chapter 3 outline. 3.5 connection-oriented transport: TCP segment structure reliable data transfer flow control connection management

Chapter 3 outline. 3.5 connection-oriented transport: TCP segment structure reliable data transfer flow control connection management Chapter 3 outline 3.1 transport-layer services 3.2 multiplexing and demultiplexing 3.3 connectionless transport: UDP 3.4 principles of reliable data transfer 3.5 connection-oriented transport: TCP segment

More information

CSC358 Week 5. Adapted from slides by J.F. Kurose and K. W. Ross. All material copyright J.F Kurose and K.W. Ross, All Rights Reserved

CSC358 Week 5. Adapted from slides by J.F. Kurose and K. W. Ross. All material copyright J.F Kurose and K.W. Ross, All Rights Reserved CSC358 Week 5 Adapted from slides by J.F. Kurose and K. W. Ross. All material copyright 1996-2016 J.F Kurose and K.W. Ross, All Rights Reserved Recap: Reliable Data Transfer rdt3.0 stop-and-wait checksum

More information

Mid Term Exam Results

Mid Term Exam Results Mid Term Exam Results v Grade Count Percentage v 20-29 1 2.38% v 40-49 2 4.76% v 50-59 5 11.90% v 60-69 18 42.86% v 70-80 16 38.10% Please hand the paper back to me after this class since we have to update

More information

CS 4390 Computer Networks. Pointers to Corresponding Section of Textbook

CS 4390 Computer Networks. Pointers to Corresponding Section of Textbook CS 4390 Computer Networks UT D application transport network data link physical Session 10 Transmission Control Protocol (TCP) An Overview Adapted from Computer Networking a Top-Down Approach 1996-2012

More information

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 9

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 9 CMPE 150/L : Introduction to Computer Networks Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 9 1 Chapter 3 outline 3.1 transport-layer services 3.2 multiplexing and demultiplexing 3.3

More information

Chapter III: Transport Layer

Chapter III: Transport Layer Chapter III: Transport Layer UG3 Computer Communications & Networks (COMN) Mahesh Marina mahesh@ed.ac.uk Slides thanks to Myungjin Lee and copyright of Kurose and Ross TCP: Overview RFCs: 793,1122,1323,

More information

10 minutes survey (anonymous)

10 minutes survey (anonymous) 10 minutes survey (anonymous) v Comments/Suggestions to my lecture/lab/ homework/exam v If you like this course, which part do you like? v If you don t like it, which part do you not like? Thanks! Transport

More information

CNT 6885 Network Review on Transport Layer

CNT 6885 Network Review on Transport Layer CNT 6885 Network Review on Transport Layer Jonathan Kavalan, Ph.D. Department of Computer, Information Science and Engineering (CISE), University of Florida User Datagram Protocol [RFC 768] no frills,

More information

TCP (Part 2) Session 10 INST 346 Technologies, Infrastructure and Architecture

TCP (Part 2) Session 10 INST 346 Technologies, Infrastructure and Architecture TCP (Part 2) Session 10 INST 346 Technologies, Infrastructure and Architecture Muddiest Points Reading pseudocode Reading finite state diagrams What parts of rdt are in TCP? Goals for Today Finish up TCP

More information

Chapter 3 outline. 3.5 Connection-oriented transport: TCP. 3.6 Principles of congestion control 3.7 TCP congestion control

Chapter 3 outline. 3.5 Connection-oriented transport: TCP. 3.6 Principles of congestion control 3.7 TCP congestion control Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles of reliable data transfer 3.5 Connection-oriented transport: TCP segment

More information

CS 43: Computer Networks. 19: TCP Flow and Congestion Control October 31, Nov 2, 2018

CS 43: Computer Networks. 19: TCP Flow and Congestion Control October 31, Nov 2, 2018 CS 43: Computer Networks 19: TCP Flow and Congestion Control October 31, Nov 2, 2018 Five-layer Internet Model Application: the application (e.g., the Web, Email) Transport: end-to-end connections, reliability

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer All material copyright 1996-2016 J.F Kurose and K.W. Ross, All Rights Reserved Computer Networking: A Top Down Approach 7 th edition Jim Kurose, Keith Ross Pearson/Addison Wesley

More information

CC451 Computer Networks

CC451 Computer Networks CC451 Computer Networks Lecture 6 Transport Layer (cont d) Transport Layer 3-1 Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty,

More information

Computer Networking Introduction

Computer Networking Introduction Computer Networking Introduction Halgurd S. Maghdid Software Engineering Department Koya University-Koya, Kurdistan-Iraq Lecture No.11 Chapter 3 outline 3.1 transport-layer services 3.2 multiplexing and

More information

Lecture 11. Transport Layer (cont d) Transport Layer 1

Lecture 11. Transport Layer (cont d) Transport Layer 1 Lecture 11 Transport Layer (cont d) Transport Layer 1 Agenda The Transport Layer (continue) Connection-oriented Transport (TCP) Flow Control Connection Management Congestion Control Introduction to the

More information

Lecture 12: Transport Layer TCP again

Lecture 12: Transport Layer TCP again Lecture 12: Transport Layer TCP again COMP 332, Spring 2018 Victoria Manfredi Acknowledgements: materials adapted from Computer Networking: A Top Down Approach 7 th edition: 1996-2016, J.F Kurose and K.W.

More information

TCP: Overview RFCs: 793, 1122, 1323, 2018, 2581

TCP: Overview RFCs: 793, 1122, 1323, 2018, 2581 TCP: Overview RFCs: 793, 1122, 1323, 2018, 2581 ocket door point-to-point: one sender, one receiver reliable, in-order byte steam: no message boundaries pipelined: TCP congestion and flow control set window

More information

Outline. TCP: Overview RFCs: 793, 1122, 1323, 2018, Development of reliable protocol Sliding window protocols

Outline. TCP: Overview RFCs: 793, 1122, 1323, 2018, Development of reliable protocol Sliding window protocols Outline Development of reliable protocol Sliding window protocols Go-Back-N, Selective Repeat Protocol performance Sockets, UDP, TCP, and IP UDP operation TCP operation connection management flow control

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer All material copyright 1996-2013 J.F Kurose and K.W. Ross, All Rights Reserved Transport Layer 3-1 Chapter 3: Transport Layer our goals: understand principles behind transport

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you can add, modify, and delete

More information

Outline. TCP: Overview RFCs: 793, 1122, 1323, 2018, steam: r Development of reliable protocol r Sliding window protocols

Outline. TCP: Overview RFCs: 793, 1122, 1323, 2018, steam: r Development of reliable protocol r Sliding window protocols Outline r Development of reliable protocol r Sliding window protocols m Go-Back-N, Selective Repeat r Protocol performance r Sockets, UDP, TCP, and IP r UDP operation r TCP operation m connection management

More information

CSCD 330 Network Programming Winter 2015

CSCD 330 Network Programming Winter 2015 CSCD 330 Network Programming Winter 2015 Lecture 11a Transport Layer Reading: Chapter 3 Some Material in these slides from J.F Kurose and K.W. Ross All material copyright 1996-2007 1 Chapter 3 Sections

More information

Course on Computer Communication and Networks. Lecture 5 Chapter 3; Transport Layer, Part B

Course on Computer Communication and Networks. Lecture 5 Chapter 3; Transport Layer, Part B Course on Computer Communication and Networks Lecture 5 Chapter 3; Transport Layer, Part B EDA344/DIT 423, CTH/GU Based on the book Computer Networking: A Top Down Approach, Jim Kurose, Keith Ross, Addison-Wesley.

More information

Lecture 8. TCP/IP Transport Layer (2)

Lecture 8. TCP/IP Transport Layer (2) Lecture 8 TCP/IP Transport Layer (2) Outline (Transport Layer) Principles behind transport layer services: multiplexing/demultiplexing principles of reliable data transfer learn about transport layer protocols

More information

Congestion Control. Principles of Congestion Control. Network-assisted Congestion Control: ATM. Congestion Control. Computer Networks 10/21/2009

Congestion Control. Principles of Congestion Control. Network-assisted Congestion Control: ATM. Congestion Control. Computer Networks 10/21/2009 Congestion Control Kai Shen Principles of Congestion Control Congestion: informally: too many sources sending too much data too fast for the network to handle results of congestion: long delays (e.g. queueing

More information

internet technologies and standards

internet technologies and standards Institute of Telecommunications Warsaw University of Technology 2017 internet technologies and standards Piotr Gajowniczek Andrzej Bąk Michał Jarociński Transport Layer The majority of slides presented

More information

Congestion Control. Daniel Zappala. CS 460 Computer Networking Brigham Young University

Congestion Control. Daniel Zappala. CS 460 Computer Networking Brigham Young University Congestion Control Daniel Zappala CS 460 Computer Networking Brigham Young University 2/25 Congestion Control how do you send as fast as possible, without overwhelming the network? challenges the fastest

More information

Congestion Control. Principles of Congestion Control. Network assisted congestion. Asynchronous Transfer Mode. Computer Networks 10/23/2013

Congestion Control. Principles of Congestion Control. Network assisted congestion. Asynchronous Transfer Mode. Computer Networks 10/23/2013 Congestion Control Kai Shen Principles of Congestion Control Congestion: Informally: too many sources sending too much data too fast for the network to handle Results of congestion: long delays (e.g. queueing

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer Chapter 3: Transport Layer our goals: understand principles behind transport layer services: multiplexing, demultiplexing reliable data transfer flow control congestion control

More information

internet technologies and standards

internet technologies and standards Institute of Telecommunications Warsaw University of Technology 2017 internet technologies and standards Piotr Gajowniczek Andrzej Bąk Michał Jarociński Transport Layer The majority of slides presented

More information

Transport layer. UDP: User Datagram Protocol [RFC 768] Review principles: Instantiation in the Internet UDP TCP

Transport layer. UDP: User Datagram Protocol [RFC 768] Review principles: Instantiation in the Internet UDP TCP Transport layer Review principles: Reliable data transfer Flow control Congestion control Instantiation in the Internet UDP TCP 1 UDP: User Datagram Protocol [RFC 768] No frills, bare bones Internet transport

More information

CSCI Topics: Internet Programming Fall 2008

CSCI Topics: Internet Programming Fall 2008 CSCI 491-01 Topics: Internet Programming Fall 2008 Transport Layer Derek Leonard Hendrix College October 20, 2008 Original slides copyright 1996-2007 J.F Kurose and K.W. Ross 1 Chapter 3: Roadmap 3.1 Transport-layer

More information

Transport layer. Review principles: Instantiation in the Internet UDP TCP. Reliable data transfer Flow control Congestion control

Transport layer. Review principles: Instantiation in the Internet UDP TCP. Reliable data transfer Flow control Congestion control Transport layer Review principles: Reliable data transfer Flow control Congestion control Instantiation in the Internet UDP TCP 1 UDP: User Datagram Protocol [RFC 768] No frills, bare bones Internet transport

More information

Chapter 3: Transport Layer

Chapter 3: Transport Layer Chapter 3: Transport Layer our goals: understand principles behind transport layer services: multiplexing, demultiplexing reliable data transfer flow control congestion control learn about Internet transport

More information

Chapter 3: Transport Layer

Chapter 3: Transport Layer Chapter 3: Transport Layer our goals: understand principles behind transport layer services: multiplexing, demultiplexing reliable data transfer flow control congestion control learn about Internet transport

More information

Lecture 15: Transport Layer Congestion Control

Lecture 15: Transport Layer Congestion Control Lecture 15: Transport Layer Congestion Control COMP 332, Spring 2018 Victoria Manfredi Acknowledgements: materials adapted from Computer Networking: A Top Down Approach 7 th edition: 1996-2016, J.F Kurose

More information

Chapter 3: Transport Layer

Chapter 3: Transport Layer Chapter 3: Transport Layer our goals: understand principles behind transport layer services: multiplexing, demultiplexing reliable data transfer flow control congestion control learn about Internet transport

More information

Principles of congestion control

Principles of congestion control Principles of congestion control Congestion: Informally: too many sources sending too much data too fast for network to handle Different from flow control! Manifestations: Lost packets (buffer overflow

More information

Application. Transport. Network. Link. Physical

Application. Transport. Network. Link. Physical Transport Layer ELEC1200 Principles behind transport layer services Multiplexing and demultiplexing UDP TCP Reliable Data Transfer TCP Congestion Control TCP Fairness *The slides are adapted from ppt slides

More information

Detecting half-open connections. Observed TCP problems

Detecting half-open connections. Observed TCP problems Detecting half-open connections TCP A TCP B 1. (CRASH) 2. CLOSED 3. SYN-SENT 4. (!!) 5. SYN-SENT 6. SYN-SENT 7. SYN-SENT

More information

Chapter 3: Transport Layer

Chapter 3: Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and

More information

CSE 4/589 Midterm Review. Hengtong Zhang SUNY Buffalo 10/30/2018

CSE 4/589 Midterm Review. Hengtong Zhang SUNY Buffalo 10/30/2018 CSE 4/589 Midterm Review Hengtong Zhang SUNY Buffalo 10/30/2018 Chapter 1 overview: what s the Internet? what s a protocol? network edge; hosts, access net, physical media network core: packet/circuit

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Modified form the following All material copyright 1996-2012 J.F Kurose

More information

Pipelined protocols: overview

Pipelined protocols: overview Pipelined protocols: overview Go-back-N: sender can have up to N unacked packets in pipeline receiver only sends cumulative ack doesn t ack packet if there s a gap sender has timer for oldest unacked packet

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely aailable to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and

More information

LECTURE 3 - TRANSPORT LAYER

LECTURE 3 - TRANSPORT LAYER LECTURE 3 - TRANSPORT LAYER 1 GOALS (1) Understand principles behind transport layer services: multiplexing, demultiplexing reliable data transfer ow control congestion control GOALS (2) Learn about Internet

More information

Transport Layer. Chapter 3. Computer Networking: A Top Down Approach

Transport Layer. Chapter 3. Computer Networking: A Top Down Approach Chapter 3 Transport Layer A note on the use of these Powerpoint slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations;

More information

CSCI Topics: Internet Programming Fall 2008

CSCI Topics: Internet Programming Fall 2008 CSCI 491-01 Topics: Internet Programming Fall 2008 Transport Layer Derek Leonard Hendrix College October 22, 2008 Original slides copyright 1996-2007 J.F Kurose and K.W. Ross 1 Chapter 3: Roadmap 3.1 Transport-layer

More information

Transport Layer. CMPS 4750/6750: Computer Networks

Transport Layer. CMPS 4750/6750: Computer Networks Transport Layer CMPS 4750/6750: Computer Networks 1 Outline Overview of transport-layer services Connectionless Transport: UDP Principles of reliable data transfer Connection-Oriented Transport: TCP TCP

More information

EC441 Fall 2018 Introduction to Computer Networking Chapter 3: Transport Layer

EC441 Fall 2018 Introduction to Computer Networking Chapter 3: Transport Layer EC441 Fall 2018 Introduction to Computer Networking Chapter 3: Transport Layer This presentation is adapted from slides produced by Jim Kurose and Keith Ross for their book, Computer Networking: A Top

More information

Computer Networking: A Top Down Approach

Computer Networking: A Top Down Approach Computer Networking: A Top Down Approach Seventh Edition Chapter 3 Transport Layer Slides in this presentation contain hyperlinks. JAWS users should be able to get a list of links by using INSERT+F7 Transport

More information

CS321: Computer Networks Congestion Control in TCP

CS321: Computer Networks Congestion Control in TCP CS321: Computer Networks Congestion Control in TCP Dr. Manas Khatua Assistant Professor Dept. of CSE IIT Jodhpur E-mail: manaskhatua@iitj.ac.in Causes and Cost of Congestion Scenario-1: Two Senders, a

More information

Correcting mistakes. TCP: Overview RFCs: 793, 1122, 1323, 2018, TCP seq. # s and ACKs. GBN in action. TCP segment structure

Correcting mistakes. TCP: Overview RFCs: 793, 1122, 1323, 2018, TCP seq. # s and ACKs. GBN in action. TCP segment structure Correcting mistakes Go-back-N: big picture: sender can have up to N unacked packets in pipeline rcvr only sends cumulative acks doesn t ack packet if there s a gap sender has r for oldest unacked packet

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these Powerpoint slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations;

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these Powerpoint slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations;

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these Powerpoint slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations;

More information

Transmission Control Protocol. ITS 413 Internet Technologies and Applications

Transmission Control Protocol. ITS 413 Internet Technologies and Applications Transmission Control Protocol ITS 413 Internet Technologies and Applications Contents Overview of TCP (Review) TCP and Congestion Control The Causes of Congestion Approaches to Congestion Control TCP Congestion

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these Powerpoint slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations;

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and

More information

TCP conges+on control

TCP conges+on control TCP conges+on control Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley Some materials copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved Chapter

More information

NT1210 Introduction to Networking. Unit 10

NT1210 Introduction to Networking. Unit 10 NT1210 Introduction to Networking Unit 10 Chapter 10, TCP/IP Transport Objectives Identify the major needs and stakeholders for computer networks and network applications. Compare and contrast the OSI

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer Chapter 3 Transport Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and

More information

CSCD 330 Network Programming Spring 2018 Lecture 11a Transport Layer

CSCD 330 Network Programming Spring 2018 Lecture 11a Transport Layer CSCD 330 Network Programming Spring 2018 Lecture 11a Transport Layer Reading: Chapter 3 Who is this? Some Material in these slides from J.F Kurose and K.W. Ross All material copyright 1996-2007 1 Bill

More information

TCP congestion control:

TCP congestion control: TCP congestion control: Probing for usable bandwidth: Ideally: transmit as fast as possible (cwnd as large as possible) without loss Increase cwnd until loss (congestion) Loss: decrease cwnd, then begin

More information

Architettura di Reti

Architettura di Reti Università di Ferrara Architettura di Reti Chapter 3: Transport Layer Carlo Giannelli carlo.giannelli@unife.it http://www.unife.it/scienze/informatica/insegnamenti/architettura-reti/ http://docente.unife.it/carlo.giannelli

More information

Data Communications & Networks. Session 9 Main Theme Network Congestion Causes, Effects, Controls, and TCP Applications. Dr. Jean-Claude Franchitti

Data Communications & Networks. Session 9 Main Theme Network Congestion Causes, Effects, Controls, and TCP Applications. Dr. Jean-Claude Franchitti Data Communications & Networks Session 9 Main Theme Network Congestion Causes, Effects, Controls, and TCP Applications Dr. Jean-Claude Franchitti New York University Computer Science Department Courant

More information

COMP/ELEC 429/556 Introduction to Computer Networks

COMP/ELEC 429/556 Introduction to Computer Networks COMP/ELEC 429/556 Introduction to Computer Networks The TCP Protocol Some slides used with permissions from Edward W. Knightly, T. S. Eugene Ng, Ion Stoica, Hui Zhang T. S. Eugene Ng eugeneng at cs.rice.edu

More information

CS3600 SYSTEMS AND NETWORKS

CS3600 SYSTEMS AND NETWORKS CS3600 SYSTEMS AND NETWORKS NORTHEASTERN UNIVERSITY Lecture 24: Congestion Control Prof. Alan Mislove (amislove@ccs.neu.edu) Slides used with permissions from Edward W. Knightly, T. S. Eugene Ng, Ion Stoica,

More information

Chapter 3 outline. Chapter 3: Transport Layer. Transport vs. network layer. Transport services and protocols. Internet transport-layer protocols

Chapter 3 outline. Chapter 3: Transport Layer. Transport vs. network layer. Transport services and protocols. Internet transport-layer protocols Chapter 3: Transport Layer our goals: understand principles behind transport layer : multiplexing, demultiplexing congestion control learn about Internet transport layer protocols: UDP: connectionless

More information

Discussions. Chapter 3. Ch03 Transport Layer. Outline. Transport services and protocols. Transport vs. network layer. Message, Segment, Datagram

Discussions. Chapter 3. Ch03 Transport Layer. Outline. Transport services and protocols. Transport vs. network layer. Message, Segment, Datagram Chapter 3 Transport Layer Yanmin Zhu Department of Computer Science and Engineering Mobile Global ISP Home Regional ISP Institutional Discussions What services are provided by layer? What services do UDP

More information

Chapter 3 Transport Layer

Chapter 3 Transport Layer CSB051 Computer Networks 電腦網路 Chapter 3 Transport Layer 吳俊興國立高雄大學資訊工程學系 Reference: Computer Networking: A Top Down Approach, 7th Global Edition, Jim Kurose, Keith Ross, Pearson Chapter 3 outline 3.1 transport-layer

More information

CS4700/CS5700 Fundamentals of Computer Networks

CS4700/CS5700 Fundamentals of Computer Networks CS4700/CS5700 Fundamentals of Computer Networks Lecture 15: Congestion Control Slides used with permissions from Edward W. Knightly, T. S. Eugene Ng, Ion Stoica, Hui Zhang Alan Mislove amislove at ccs.neu.edu

More information

Outline Computer Networking. TCP slow start. TCP modeling. TCP details AIMD. Congestion Avoidance. Lecture 18 TCP Performance Peter Steenkiste

Outline Computer Networking. TCP slow start. TCP modeling. TCP details AIMD. Congestion Avoidance. Lecture 18 TCP Performance Peter Steenkiste Outline 15-441 Computer Networking Lecture 18 TCP Performance Peter Steenkiste Fall 2010 www.cs.cmu.edu/~prs/15-441-f10 TCP congestion avoidance TCP slow start TCP modeling TCP details 2 AIMD Distributed,

More information

Internetworking With TCP/IP

Internetworking With TCP/IP Internetworking With TCP/IP Application Layer Telnet Gopher NFS FTP X Win TFTP SMTP SNMP REXEC DNS RPC Transport Layer TCP UDP Network Layer ICMP IP IGMP ARP RARP Link Interface Ethernet, IEEE 802.3, Token

More information

Transmission Control Protocol

Transmission Control Protocol TDTS06: Computer Networks Instructor: Niklas Carlsson Email: niklas.carlsson@liu.se Transmission Control Protocol Notes derived from Computer Networking: A Top Down Approach, by Jim Kurose and Keith Ross,

More information

15-744: Computer Networking TCP

15-744: Computer Networking TCP 15-744: Computer Networking TCP Congestion Control Congestion Control Assigned Reading [Jacobson and Karels] Congestion Avoidance and Control [TFRC] Equation-Based Congestion Control for Unicast Applications

More information

Go-Back-N. Pipelining: increased utilization. Pipelined protocols. GBN: sender extended FSM

Go-Back-N. Pipelining: increased utilization. Pipelined protocols. GBN: sender extended FSM Pipelined protocols Pipelining: sender allows multiple, in-flight, yet-to-be-acknowledged pkts range of sequence numbers must be increased buffering at sender and/or receiver Pipelining: increased utilization

More information

CSCI-1680 Transport Layer II Data over TCP Rodrigo Fonseca

CSCI-1680 Transport Layer II Data over TCP Rodrigo Fonseca CSCI-1680 Transport Layer II Data over TCP Rodrigo Fonseca Based partly on lecture notes by David Mazières, Phil Levis, John Janno< Last Class CLOSED Passive open Close Close LISTEN Introduction to TCP

More information

COMP211 Chapter 3 Transport Layer

COMP211 Chapter 3 Transport Layer COMP211 Chapter 3 Transport Layer All material copyright 1996-2016 J.F Kurose and K.W. Ross, All Rights Reserved Computer Networking: A Top Down Approach 7 th edition Jim Kurose, Keith Ross Pearson/Addison

More information