TCP in Asymmetric Environments
|
|
- Todd Dennis
- 6 years ago
- Views:
Transcription
1 TCP in Asymmetric Environments KReSIT, IIT Bombay Vijay T. Raisinghani TCP in Asymmetric Environments 1
2 TCP Overview Four congestion control algorithms Slow start Congestion avoidance Fast retransmit Fast recovery Working based on receipt of ACKs; ACKclocked TCP in Asymmetric Environments 2
3 Asymmetry Overview Throughput achieved also dependent on reverse channel Bandwidth Lower bandwidth up-link (reverse) channel Dial-up line; bandwidth constrained lossy wireless channel Latency / Media access Low power mobile units TCP in Asymmetric Environments 3
4 Asymmetric Network Characteristics High forward bandwidth Low queuing delays on forward path Data packets experience almost no congestion Host A Host B Low reverse bandwidth Large queuing and propagation delays Acks suffer congestion Thus, Throughput achieved is also dependent on reverse channel TCP in Asymmetric Environments 4
5 TCP and Asymmetric Networks Delayed arrival or dropping of Acks Slower growth of congestion window Large RTT variations Cumulative acknowledgment hence sender burstiness No Acks dropped if: Effective Bandwidth in Forward direction Effective Bandwidth in Reverse direction For 2 Mbps 10 Kbps > 1600 bytes 40 bytes Data Packet size Ack size Reverse link saturated before forward link, if more than 1 Ack for 5 packets TCP in Asymmetric Environments 5
6 Typical (Asymmetric) Technologies Cable modem networks Direct broadcast satellite Asymmetric Digital Subscriber Loop TCP in Asymmetric Environments 6
7 Pain in the ACK Reverse channel problems impairs ACK flow ACKs come in slowly ACKs may be dropped due to congestion Packet radio network (half-duplex) Variable latencies ACK flowing opposite to data packets cause interference RTT estimate highly variable TCP in Asymmetric Environments 7
8 Pain in the ACK TCP relies on timely ACKS to utilize bandwidth Slow growth of window if low bandwidth reverse path Burstiness if delayed ACKs Variability in RTT Inflates TCP retransmission timeout Effects loss recovery TCP in Asymmetric Environments 8
9 Typical Topology 10 Mbps wireless 28.8Kbps dial-up TCP in Asymmetric Environments 9
10 Proposed Solutions Path MTU discovery J. Mogul, S. Deering (RFC 1191, 1990) TCP-Large Window (TCP-LW) V. Jacobson, R. Braden, D. Borman (RFC 1323, 1992) TCP for transactions (T/TCP) R. Braden (RFC 1644, 1994) TCP SACK M. Mathis, S. Flyod, A. Romanow (RFC 2018, 1996) Asymmetric TCP (TCP ASYM) H. Balakrishnan, V. Padmanabhan, R. Katz (1997) MONET98 TCP in Asymmetric Environments 10
11 Proposed Solutions Satellite Transport Protocol (STP) T. Henderson, R. Katz (1999) Space Comm. Protocol Spec (SCPS-TP) NASA (1999) Window Prediction Mechanism A. C. Auge, J.L. Magnet, J.P. Aspas Mild Aggression Vijay T. Raisinghani, Abhishek Patil, Sridhar Iyer (2000) TCP in Asymmetric Environments 11
12 Asymmetric TCP [H. Balakrishnan, V.N. Padmanabhan, R.H. Katz] Effect of networks asymmetry on end-toend TCP performance Bandwidth and latency asymmetries Techniques to improve end-to-end performance Decrease rate of ACKs Sender adaptation ACK scheduling at router TCP in Asymmetric Environments 12
13 Experiment Parameters Link bandwidth Latency Packet-radio turn around time TCP in Asymmetric Environments 13
14 Terminology Normalized bandwidth ratio k Bandwidth ratio over packet size ratio E.g.: 10 Mbps forward; 100 Kbps reverse 1000 byte data packet; 40 byte ack k = 100 / 25 i.e. 4 TCP in Asymmetric Environments 14
15 Effect of k High bandwidth forward link Sender k > 1 Receiver Cwnd growth slowed Burstiness Idle periods Low bandwidth reverse link Bottleneck router Could result in ACK (dup- ACK) dropping TCP in Asymmetric Environments 15
16 Experiments and Simulations Wireless cable modem networks Forward channel 10Mbps; 5ms latency Reverse dial-up; 14.4 / 28.8Kbps Packet radio network No explicit bandwidth asymmetry Data traffic affected by ACK traffic TCP in Asymmetric Environments 16
17 Cable Modem Topology 10 Mbps wireless 28.8Kbps dial-up TCP in Asymmetric Environments 17
18 Slide modified by C. Pham Measured Throughput (One way transfers) Assuming - 1K packet - 10Mbps forward - 28Kbps reverse SLIP Ack size:52 bytes K= CSLIP Ack size:18 bytes K=6.25
19 Measured Throughput (Two way transfers) High bandwidth forward link Sender Cwnd growth slowed Burstiness Idle periods Web trf Assume reverse connection is initiated first: ACK for forward delayed at buffer/router Slide modified by C. Pham TCP in Asymmetric Environments 19
20 Measured Throughput (2-way) Web trf Slide modified by C. Pham TCP in Asymmetric Environments 20
21 Issues in Packet Radio Variable delay Radio turnaround time MAC protocol RTS/ CTS Back-off at sender Link layer ACKs TCP in Asymmetric Environments 21
22 Solutions ACK Congestion Control (ACC) ACK Filtering (AF) Sender Adaptation (SA) ACK reconstruction (AR) Scheduling data and ACKs TCP in Asymmetric Environments 22
23 ACK Congestion Control Buffers have packet(not byte) limits Random Early Detection (RED) algorithm at reverse link gateway Gateway senses incipient congestion Selects packet (in queue) at random for Explicit Congestion Notification (ECN) Notification reflected back to sender of packet(ack) Drop at random, if queue full TCP in Asymmetric Environments 23
24 ACK Congestion Control TCP receiver maintains delay factor d ACK for every d data packets Increase d multiplicatively on receipt of ECN Subsequently decrease d linearly per RTT if NO ECN d min = 1, max = Sender window TCP in Asymmetric Environments 24
25 ACK Filtering TCP ACKs cumulative Mechanism New ACK en-queued Check queue for smaller seq. number ACKs Drop some / all redundant ACKs TCP in Asymmetric Environments 25
26 Sender Adaptation AF and ACC decrease ACK frequency Problems at data sender Sender burstiness Slow window growth Reduced effectiveness of fast retransmission Decrease burst of data send (upper bound) cwnd / srtt data rate TCP in Asymmetric Environments 26
27 Sender Adaptation Byte count to increase window, not ACK count Retransmission solution ACC: After threshold out-of-order packets mark subsequent DUPACKs with fast retransmit bit AF: Similar action at router Sender fast retransmits even if one such ACK TCP in Asymmetric Environments 27
28 ACK Reconstruction To prevent reduced ACK frequency from affecting sender Reconstruct ACK stream after bottleneck link Fill in the gaps to smooth out ACK stream TCP in Asymmetric Environments 28
29 Scheduling Data and ACKs Problem Single FIFO queue in reverse direction ACKs first scheduling Prevents forward channel starving TCP in Asymmetric Environments 29
30 Solutions (Packet Radio) Minimize the effect of turn-around time by Piggybacking Link Layer ACKs. ACK Filtering and ACK Congestion Control. AF is better than ACC because it completely eliminates the redundant ACKs & reduces the amount of interfering traffic. TCP in Asymmetric Environments 30
31 Issues ACC/AF Routers need to be TCP Aware. If the connection uses encryption then the schemes won't work. Modifications required at router Overhead at router Can cause burstiness AF: mobile host - IP Address changes? TCP in Asymmetric Environments 31
32 Issues Lot of modifications required to TCP stack AR Ack Reconstruction topology dependent ECN Problems if high bandwidth not available later Checksum problem TCP in Asymmetric Environments 32
33 Satellite Transport Protocol [T.R. Henderson, R.H. Katz] Optimized for satellite environment TCP in Asymmetric Environments 33
34 STP Design Selective ACKs No retransmission timers No ACK for alternate packets Reduces ACK traffic Transmitter asks for ACKs Negative ACK for losses TCP in Asymmetric Environments 34
35 STP Design 4 basic packet types Sequenced Data, POLL, STAT, USTAT Sequenced Data (SD) User data; has sequence number and cheksum POLL Periodically sent to receiver Contains timestamp and next in-sequence SD number (indicates to receiver what it should have received so far) 2-3 per RTT TCP in Asymmetric Environments 35
36 STP Design STAT(us) message Similar to SACK Reports entire state of receiver buffer Hence robust to loss of POLLs or STATs U(nsolicited)STAT To immediately report gaps TCP in Asymmetric Environments 36
37 STP Example TCP in Asymmetric Environments 37
38 STP Flow Control Congestion Control Slow start (as in TCP); never re-entered since no timeout Window growth based on STAT Send packets over RTT RTT estimated from timestamp on STAT and current time Byte (not ACK) counting to increase window TCP in Asymmetric Environments 38
39 STP Design Reduced handshake similar to T/TCP BEGIN message contains data also Piggyback POLL messages TCP in Asymmetric Environments 39
40 Split STP v/s Split TCP Similar throughput Long RTT STP thruput slightly lower Smoothing Tx over RTT STP bandwidth overhead slightly lower STP reverse channel usage linearly decreases with RTT POLL frequency based on RTT Less sensitive to variations in RTT TCP in Asymmetric Environments 40
41 STP Deployment End host to implement STP Or Satellite interface change STP to TCP Internally in a satellite network TCP in Asymmetric Environments 41
42 Window Prediction Mechanism [A.C. Auge, J.L. Magnet, J.P. Aspas] Implemented at receiver Delayed ACKs with varying delay factor r Adapted dynamically based on expected no. of packets Reconstruct congestion control behavior of sender TCP in Asymmetric Environments 42
43 WPM Design Mimic sender behavior Receiver maintains predicted values pcwnd and pssthresh Helps decide r Initially pssthresh = max. cwnd When no. of packets recv = r, send new delayed ACK Dup ACKs not delayed Max. 6 dupacks in a row; to avoid congestion TCP in Asymmetric Environments 43
44 Mild Aggression (MA) [V.T. Raisinghani, A. Patil, Sridhar Iyer] Other approaches focus on reverse channel MA takes cognizance of healthy forward channel MA attempts to minimize impact of reverse channel characteristics by Mild Aggression Factors TCP in Asymmetric Environments 44
45 MA Basics Assumptions High bandwidth forward channel No packet loss on forward channel Network inspected to determine MAFs Large cwnd (= 4) Mild Aggression Factors (q and e) goodrtt(grtt) = q * RTT during slow start e to aid window growth Congestion Avoidance similar to TCP Normal retransmission suppressed during MA Receiver sends NACK for lost packet TCP in Asymmetric Environments 45
46 MA Algorithm ACK received? No start grtt timer grtt = q * RTT Std TCP Congestion Avoid & Slow-start cwnd_last = cwnd Yes Congestion avoid? Std TCP Congestion Avoid grtt timeout? Slow Start? Yes cwnd = min ( min(cwnd + e, cwnd_last*2), receiver_window) No Std TCP timeout behavior cwnd == 2*cwnd_last? TCP in Asymmetric Environments 46
47 MA Simulation N1 10 Mbps, 500ms N3 9.6 Kbps, 10ms 9.6 Kbps, 10ms N5 N Kbps, 10ms 5 Mbps, 5ms N4 1 Mbps, 2ms N6 TCP in Asymmetric Environments 47
48 Simulation Result TCP in Asymmetric Environments 48
49 Mild Aggression Summary Early ramp-up of cwnd Can work even if packets are encrypted Reduced ACK frequency Aggression factor needs to be decided and adapted High k may cause losses in forward direction TCP in Asymmetric Environments 49
50 MA Summary MAFs improve the congestion window growth during Slow Start No modifications required at routers We believe q typically to be around 0.8 in actual environments TCP in Asymmetric Environments 50
51 Further Reading Hari Balakrishnan, Venkata N. Padmanabhan, Randy H. Katz The Effects of Asymmetry on TCP Performance Thomas R. Henderson, Randy H. Katz Transport Protocols for Internet-Compatible Satellite Networks Enhancing TCP Over Satellite Channels (RFC 2488) Ongoing TCP Research Related to Satellites (RFC 2760) TCP Congestion Control (RFC 2581) TCP in Asymmetric Environments 51
Mild Aggression : A new approach for improving TCP Performance in Asymmetric Networks
: A new approach for improving TCP Performance in Asymmetric Networks Abstract Vijay T. Raisinghani Abhishek Patil Sridhar Iyer K.R. School of Information Technology IIT Bombay, Mumbai, INDIA {rvijay,
More informationThe Effects of Asymmetry on TCP Performance
The Effects of Asymmetry on TCP Performance Hari Balakrishnan Venkata N. Padmanabhan Randy H. Katz University of California at Berkeley Daedalus/BARWAN Retreat June 1997 Outline Overview Bandwidth asymmetry
More informationWireless Heterogeneity. EEC173B/ECS152C, Spring 09. Data Transport Over Wireless. Wireless Performance. Reliable Data Transport over Wireless Networks
EEC73B/ECSC, Spring 9 Reliable Data over Wireless s Problems with TCP Snoop Protocol Metricom Ricochet Wireless Heterogeneity Lucent WaveLAN Regional-Area Metro-Area Cellular Digital IBM Infrared Packet
More informationOutline 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 informationTCP over wireless links
CSc 450/550 Computer Communications & Networks TCP over wireless links Jianping Pan (stand-in for Dr. Wu) 1/31/06 CSc 450/550 1 TCP over wireless links TCP a quick review on how TCP works Wireless links
More informationChapter 13 TRANSPORT. Mobile Computing Winter 2005 / Overview. TCP Overview. TCP slow-start. Motivation Simple analysis Various TCP mechanisms
Overview Chapter 13 TRANSPORT Motivation Simple analysis Various TCP mechanisms Distributed Computing Group Mobile Computing Winter 2005 / 2006 Distributed Computing Group MOBILE COMPUTING R. Wattenhofer
More informationUNIT IV -- TRANSPORT LAYER
UNIT IV -- TRANSPORT LAYER TABLE OF CONTENTS 4.1. Transport layer. 02 4.2. Reliable delivery service. 03 4.3. Congestion control. 05 4.4. Connection establishment.. 07 4.5. Flow control 09 4.6. Transmission
More informationOverview. TCP & router queuing Computer Networking. TCP details. Workloads. TCP Performance. TCP Performance. Lecture 10 TCP & Routers
Overview 15-441 Computer Networking TCP & router queuing Lecture 10 TCP & Routers TCP details Workloads Lecture 10: 09-30-2002 2 TCP Performance TCP Performance Can TCP saturate a link? Congestion control
More informationCS 5520/ECE 5590NA: Network Architecture I Spring Lecture 13: UDP and TCP
CS 5520/ECE 5590NA: Network Architecture I Spring 2008 Lecture 13: UDP and TCP Most recent lectures discussed mechanisms to make better use of the IP address space, Internet control messages, and layering
More informationWireless TCP Performance Issues
Wireless TCP Performance Issues Issues, transport layer protocols Set up and maintain end-to-end connections Reliable end-to-end delivery of data Flow control Congestion control Udp? Assume TCP for the
More informationCMPE 257: Wireless and Mobile Networking
CMPE 257: Wireless and Mobile Networking Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 10 CMPE 257 Spring'15 1 Student Presentations Schedule May 21: Sam and Anuj May 26: Larissa
More informationCS519: Computer Networks. Lecture 5, Part 4: Mar 29, 2004 Transport: TCP congestion control
: Computer Networks Lecture 5, Part 4: Mar 29, 2004 Transport: TCP congestion control TCP performance We ve seen how TCP the protocol works Sequencing, receive window, connection setup and teardown And
More informationTransport layer issues
Transport layer issues Dmitrij Lagutin, dlagutin@cc.hut.fi T-79.5401 Special Course in Mobility Management: Ad hoc networks, 28.3.2007 Contents Issues in designing a transport layer protocol for ad hoc
More informationCongestion / Flow Control in TCP
Congestion and Flow Control in 1 Flow Control and Congestion Control Flow control Sender avoids overflow of receiver buffer Congestion control All senders avoid overflow of intermediate network buffers
More informationCS Transport. Outline. Window Flow Control. Window Flow Control
CS 54 Outline indow Flow Control (Very brief) Review of TCP TCP throughput modeling TCP variants/enhancements Transport Dr. Chan Mun Choon School of Computing, National University of Singapore Oct 6, 005
More informationCMSC 417. Computer Networks Prof. Ashok K Agrawala Ashok Agrawala. October 30, 2018
CMSC 417 Computer Networks Prof. Ashok K Agrawala 2018 Ashok Agrawala October 30, 2018 Message, Segment, Packet, and Frame host host HTTP HTTP message HTTP TCP TCP segment TCP router router IP IP packet
More informationPerformance Analysis of TCP Variants
102 Performance Analysis of TCP Variants Abhishek Sawarkar Northeastern University, MA 02115 Himanshu Saraswat PES MCOE,Pune-411005 Abstract The widely used TCP protocol was developed to provide reliable
More informationCongestion Control in TCP
Congestion Control in TCP Antonio Carzaniga Faculty of Informatics University of Lugano May 6, 2005 Outline Intro to congestion control Input rate vs. output throughput Congestion window Congestion avoidance
More informationEffect of SCTP Multistreaming over Satellite Links
Effect of SCTP Multistreaming over Satellite Links Mohammed Atiquzzaman (Co-author: William Ivancic (NASA)) School of Computer Science University of Oklahoma. Email: atiq@ieee.org Web: www.cs.ou.edu/~atiq
More informationCSE 4215/5431: Mobile Communications Winter Suprakash Datta
CSE 4215/5431: Mobile Communications Winter 2013 Suprakash Datta datta@cse.yorku.ca Office: CSEB 3043 Phone: 416-736-2100 ext 77875 Course page: http://www.cse.yorku.ca/course/4215 Some slides are adapted
More informationOutline 9.2. TCP for 2.5G/3G wireless
Transport layer 9.1 Outline Motivation, TCP-mechanisms Classical approaches (Indirect TCP, Snooping TCP, Mobile TCP) PEPs in general Additional optimizations (Fast retransmit/recovery, Transmission freezing,
More informationTCP so far Computer Networking Outline. How Was TCP Able to Evolve
TCP so far 15-441 15-441 Computer Networking 15-641 Lecture 14: TCP Performance & Future Peter Steenkiste Fall 2016 www.cs.cmu.edu/~prs/15-441-f16 Reliable byte stream protocol Connection establishments
More informationMobile Transport Layer
Mobile Transport Layer 1 Transport Layer HTTP (used by web services) typically uses TCP Reliable transport between TCP client and server required - Stream oriented, not transaction oriented - Network friendly:
More informationTransmission 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 informationMobile Communications Chapter 9: Mobile Transport Layer
Prof. Dr.-Ing Jochen H. Schiller Inst. of Computer Science Freie Universität Berlin Germany Mobile Communications Chapter 9: Mobile Transport Layer Motivation, TCP-mechanisms Classical approaches (Indirect
More informationImpact of transmission errors on TCP performance. Outline. Random Errors
Impact of transmission errors on TCP performance 1 Outline Impact of transmission errors on TCP performance Approaches to improve TCP performance Classification Discussion of selected approaches 2 Random
More informationMobile Communications Chapter 9: Mobile Transport Layer
Prof. Dr.-Ing Jochen H. Schiller Inst. of Computer Science Freie Universität Berlin Germany Mobile Communications Chapter 9: Mobile Transport Layer Motivation, TCP-mechanisms Classical approaches (Indirect
More informationECS-087: Mobile Computing
ECS-087: Mobile Computing TCP over wireless TCP and mobility Most of the Slides borrowed from Prof. Sridhar Iyer s lecture IIT Bombay Diwakar Yagyasen 1 Effect of Mobility on Protocol Stack Application:
More informationCommunication Networks
Communication Networks Spring 2018 Laurent Vanbever nsg.ee.ethz.ch ETH Zürich (D-ITET) April 30 2018 Materials inspired from Scott Shenker & Jennifer Rexford Last week on Communication Networks We started
More informationEnhancing TCP Throughput over Lossy Links Using ECN-Capable Capable RED Gateways
Enhancing TCP Throughput over Lossy Links Using ECN-Capable Capable RED Gateways Haowei Bai Honeywell Aerospace Mohammed Atiquzzaman School of Computer Science University of Oklahoma 1 Outline Introduction
More informationCMSC 417. Computer Networks Prof. Ashok K Agrawala Ashok Agrawala. October 25, 2018
CMSC 417 Computer Networks Prof. Ashok K Agrawala 2018 Ashok Agrawala Message, Segment, Packet, and Frame host host HTTP HTTP message HTTP TCP TCP segment TCP router router IP IP packet IP IP packet IP
More informationExercises TCP/IP Networking With Solutions
Exercises TCP/IP Networking With Solutions Jean-Yves Le Boudec Fall 2009 3 Module 3: Congestion Control Exercise 3.2 1. Assume that a TCP sender, called S, does not implement fast retransmit, but does
More informationPage 1. Review: Internet Protocol Stack. Transport Layer Services. Design Issue EEC173B/ECS152C. Review: TCP
EEC7B/ECS5C Review: Internet Protocol Stack Review: TCP Application Telnet FTP HTTP Transport Network Link Physical bits on wire TCP LAN IP UDP Packet radio Transport Layer Services Design Issue Underlying
More informationTCP Congestion Control 65KB W
TCP Congestion Control 65KB W TO 3DA 3DA TO 0.5 0.5 0.5 0.5 3 3 1 SS SS CA SS CA TCP s Congestion Window Maintenance TCP maintains a congestion window (cwnd), based on packets Sender s window is limited
More informationRED behavior with different packet sizes
RED behavior with different packet sizes Stefaan De Cnodder, Omar Elloumi *, Kenny Pauwels Traffic and Routing Technologies project Alcatel Corporate Research Center, Francis Wellesplein, 1-18 Antwerp,
More informationDoes current Internet Transport work over Wireless? Reviewing the status of IETF work in this area
Does current Internet Transport work over Wireless? Reviewing the status of IETF work in this area Sally Floyd March 2, 2000 IAB Workshop on Wireless Internetworking 1 Observations: Transport protocols
More informationChapter 3. Wireless Access of Internet Using TCP/IP A Survey of Issues and Recommendations 3.1 INTRODUCTION
Chapter 3 Wireless Access of Internet Using TCP/IP A Survey of Issues and Recommendations Sridhar Komandur, Spencer Dawkins and Jogen Pathak Cynela Networks, Inc 3.1 INTRODUCTION The Internet has many
More informationAnalytic End-to-End Estimation for the One-Way Delay and Its Variation
Analytic End-to-End Estimation for the One-Way Delay and Its Variation Jin-Hee Choi and Chuck Yoo Department of Computer Science and Engineering Korea University Email: {jhchoi, hxy}@os.korea.ac.kr Telephone:
More informationSWAP and TCP performance
SWAP and TCP performance Jean Tourrilhes, HPLB 23 March 98 1 Introduction The SWAP protocol that we have proposed [4] the HRFWG is designed to carry TCP/IP traffic. Of course, we would never had proposed
More informationPage 1. Review: Internet Protocol Stack. Transport Layer Services EEC173B/ECS152C. Review: TCP. Transport Layer: Connectionless Service
EEC7B/ECS5C Review: Internet Protocol Stack Review: TCP Application Telnet FTP HTTP Transport Network Link Physical bits on wire TCP LAN IP UDP Packet radio Do you remember the various mechanisms we have
More information8. TCP Congestion Control
8. TCP Congestion Control 1 TCP Congestion Control Slow-start increase Multiplicative decrease Congestion avoidance Measurement of variation Exponential timer backoff 2002 Yanghee Choi 2 Congestion Control
More informationTCP over Wireless. Protocols and Networks Hadassah College Spring 2018 Wireless Dr. Martin Land 1
TCP over Wireless Protocols and Networks Hadassah College Spring 218 Wireless Dr. Martin Land 1 Classic TCP-Reno Ideal operation in-flight segments = cwnd (send cwnd without stopping) Cumulative ACK for
More informationCS 268: Wireless Transport Protocols. Kevin Lai Feb 13, 2002
CS 268: Wireless Transport Protocols Kevin Lai Feb 13, 2002 Motivation! Wireless connectivity proliferating - Satellite, line-of-sight microwave, line-of-sight laser, cellular data (CDMA, GPRS, 3G), wireless
More informationTCP Performance. EE 122: Intro to Communication Networks. Fall 2006 (MW 4-5:30 in Donner 155) Vern Paxson TAs: Dilip Antony Joseph and Sukun Kim
TCP Performance EE 122: Intro to Communication Networks Fall 2006 (MW 4-5:30 in Donner 155) Vern Paxson TAs: Dilip Antony Joseph and Sukun Kim http://inst.eecs.berkeley.edu/~ee122/ Materials with thanks
More informationTCP 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 informationCongestion Control End Hosts. CSE 561 Lecture 7, Spring David Wetherall. How fast should the sender transmit data?
Congestion Control End Hosts CSE 51 Lecture 7, Spring. David Wetherall Today s question How fast should the sender transmit data? Not tooslow Not toofast Just right Should not be faster than the receiver
More informationTransport Layer (Congestion Control)
Transport Layer (Congestion Control) Where we are in the Course Moving on up to the Transport Layer! Application Transport Network Link Physical CSE 461 University of Washington 2 Congestion Collapse Congestion
More informationTCP over Wireless PROF. MICHAEL TSAI 2016/6/3
TCP over Wireless PROF. MICHAEL TSAI 2016/6/3 2 TCP Congestion Control (TCP Tahoe) Only ACK correctly received packets Congestion Window Size: Maximum number of bytes that can be sent without receiving
More informationRecap. TCP connection setup/teardown Sliding window, flow control Retransmission timeouts Fairness, max-min fairness AIMD achieves max-min fairness
Recap TCP connection setup/teardown Sliding window, flow control Retransmission timeouts Fairness, max-min fairness AIMD achieves max-min fairness 81 Feedback Signals Several possible signals, with different
More informationChapter 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 informationRecap. More TCP. Congestion avoidance. TCP timers. TCP lifeline. Application Presentation Session Transport Network Data Link Physical
Recap ½ congestion window ½ congestion window More TCP Congestion avoidance TCP timers TCP lifeline Application Presentation Session Transport Network Data Link Physical 1 Congestion Control vs Avoidance
More informationAdvanced Computer Networks. Wireless TCP
Advanced Computer Networks 263 3501 00 Wireless TCP Patrick Stuedi Spring Semester 2014 1 Oriana Riva, Department of Computer Science ETH Zürich Outline Last week: Today: Cellular Networks Mobile IP Wireless
More informationTECHNICAL RESEARCH REPORT
TECHNICAL RESEARCH REPORT TCP over Satellite Hybrid Networks: A Survey by Xiaoming Zhou, John S. Baras CSHCN TR 2002-15 (ISR TR 2002-27) The Center for Satellite and Hybrid Communication Networks is a
More informationPlacement of Function in a Best Effort World. Course Logistics Update
Placement of Function in a Best Effort World Course Logistics Update 45 total in class. Still off target. Prioritized waitlist now available. See me after class. 1 Internet Architecture Redux The network
More informationLecture 21: Congestion Control" CSE 123: Computer Networks Alex C. Snoeren
Lecture 21: Congestion Control" CSE 123: Computer Networks Alex C. Snoeren Lecture 21 Overview" How fast should a sending host transmit data? Not to fast, not to slow, just right Should not be faster than
More informationDualRTT: Enhancing TCP Performance During Delay Spikes
DualRTT: Enhancing TCP Performance During Delay Spikes Ph.D. School of Computer Science University of Oklahoma. Email: atiq@ieee.org Web: www.cs.ou.edu/~atiq Presentation at Tohoku University, Sendai,
More informationTCP Congestion Control : Computer Networking. Introduction to TCP. Key Things You Should Know Already. Congestion Control RED
TCP Congestion Control 15-744: Computer Networking L-4 TCP Congestion Control RED Assigned Reading [FJ93] Random Early Detection Gateways for Congestion Avoidance [TFRC] Equation-Based Congestion Control
More informationLecture 14: Congestion Control"
Lecture 14: Congestion Control" CSE 222A: Computer Communication Networks George Porter Thanks: Amin Vahdat, Dina Katabi and Alex C. Snoeren Lecture 14 Overview" TCP congestion control review Dukkipati
More informationCongestion Collapse in the 1980s
Congestion Collapse Congestion Collapse in the 1980s Early TCP used fixed size window (e.g., 8 packets) Initially fine for reliability But something happened as the ARPANET grew Links stayed busy but transfer
More informationTCP based Receiver Assistant Congestion Control
International Conference on Multidisciplinary Research & Practice P a g e 219 TCP based Receiver Assistant Congestion Control Hardik K. Molia Master of Computer Engineering, Department of Computer Engineering
More informationCongestion 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 informationPerformance Consequences of Partial RED Deployment
Performance Consequences of Partial RED Deployment Brian Bowers and Nathan C. Burnett CS740 - Advanced Networks University of Wisconsin - Madison ABSTRACT The Internet is slowly adopting routers utilizing
More informationTRANSMISSION CONTROL PROTOCOL
COMP 635: WIRELESS & MOBILE COMMUNICATIONS TRANSMISSION CONTROL PROTOCOL Jasleen Kaur Fall 2017 1 Impact of Wireless on Protocol Layers Application layer Transport layer Network layer Data link layer Physical
More informationimage 3.8 KB Figure 1.6: Example Web Page
image. KB image 1 KB Figure 1.: Example Web Page and is buffered at a router, it must wait for all previously queued packets to be transmitted first. The longer the queue (i.e., the more packets in the
More informationIIP Wireless. Presentation Outline
IIP Wireless Improving Internet Protocols for Wireless Links Markku Kojo Department of Computer Science www.cs cs.helsinki.fi/research/.fi/research/iwtcp/ 1 Presentation Outline Project Project Summary
More informationWireless TCP. TCP mechanism. Wireless Internet: TCP in Wireless. Wireless TCP: transport layer
Wireless TCP W.int.2-2 Wireless Internet: TCP in Wireless Module W.int.2 Mobile IP: layer, module W.int.1 Wireless TCP: layer Dr.M.Y.Wu@CSE Shanghai Jiaotong University Shanghai, China Dr.W.Shu@ECE University
More informationImproving the Robustness of TCP to Non-Congestion Events
Improving the Robustness of TCP to Non-Congestion Events Presented by : Sally Floyd floyd@acm.org For the Authors: Sumitha Bhandarkar A. L. Narasimha Reddy {sumitha,reddy}@ee.tamu.edu Problem Statement
More informationCS321: 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 informationLecture 15: TCP over wireless networks. Mythili Vutukuru CS 653 Spring 2014 March 13, Thursday
Lecture 15: TCP over wireless networks Mythili Vutukuru CS 653 Spring 2014 March 13, Thursday TCP - recap Transport layer TCP is the dominant protocol TCP provides in-order reliable byte stream abstraction
More informationInvestigating the Use of Synchronized Clocks in TCP Congestion Control
Investigating the Use of Synchronized Clocks in TCP Congestion Control Michele Weigle Dissertation Defense May 14, 2003 Advisor: Kevin Jeffay Research Question Can the use of exact timing information improve
More informationTCP Congestion Control
6.033, Spring 2014 TCP Congestion Control Dina Katabi & Sam Madden nms.csail.mit.edu/~dina Sharing the Internet How do you manage resources in a huge system like the Internet, where users with different
More informationCongestion Control in Communication Networks
Congestion Control in Communication Networks Introduction Congestion occurs when number of packets transmitted approaches network capacity Objective of congestion control: keep number of packets below
More informationIntro to LAN/WAN. Transport Layer
Intro to LAN/WAN Transport Layer Transport Layer Topics Introduction (6.1) Elements of Transport Protocols (6.2) Internet Transport Protocols: TDP (6.5) Internet Transport Protocols: UDP (6.4) socket interface
More informationCongestion Control in TCP
Congestion Control in TCP Antonio Carzaniga Faculty of Informatics University of Lugano November 11, 2014 Outline Intro to congestion control Input rate vs. output throughput Congestion window Congestion
More informationOutline. CS5984 Mobile Computing
CS5984 Mobile Computing Dr. Ayman Abdel-Hamid Computer Science Department Virginia Tech Outline Review Transmission Control Protocol (TCP) Based on Behrouz Forouzan, Data Communications and Networking,
More informationImproving TCP Congestion Control over Internets with Heterogeneous Transmission Media
Improving TCP Congestion Control over Internets with Heterogeneous Transmission Media We present a new implementation of TCP that is better suited to today s Internet than TCP Reno or Tahoe. Our implementation
More informationAnnouncements Computer Networking. Outline. Transport Protocols. Transport introduction. Error recovery & flow control. Mid-semester grades
Announcements 15-441 Computer Networking Lecture 16 Transport Protocols Mid-semester grades Based on project1 + midterm + HW1 + HW2 42.5% of class If you got a D+,D, D- or F! must meet with Dave or me
More informationComputer 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 informationTECHNICAL RESEARCH REPORT
TECHNICAL RESEARCH REPORT Flow Control at Satellite Gateways by Xiaoming Zhou, Xicheng Liu, John S. Baras CSHCN TR 2002-19 (ISR TR 2002-37) The Center for Satellite and Hybrid Communication Networks is
More informationLecture 7: Sliding Windows. CSE 123: Computer Networks Geoff Voelker (guest lecture)
Lecture 7: Sliding Windows CSE 123: Computer Networks Geoff Voelker (guest lecture) Please turn in HW #1 Thank you From last class: Sequence Numbers Sender Receiver Sender Receiver Timeout Timeout Timeout
More informationCHAPTER 3 EFFECTIVE ADMISSION CONTROL MECHANISM IN WIRELESS MESH NETWORKS
28 CHAPTER 3 EFFECTIVE ADMISSION CONTROL MECHANISM IN WIRELESS MESH NETWORKS Introduction Measurement-based scheme, that constantly monitors the network, will incorporate the current network state in the
More informationECE 435 Network Engineering Lecture 10
ECE 435 Network Engineering Lecture 10 Vince Weaver http://web.eece.maine.edu/~vweaver vincent.weaver@maine.edu 28 September 2017 Announcements HW#4 was due HW#5 will be posted. midterm/fall break You
More informationRD-TCP: Reorder Detecting TCP
RD-TCP: Reorder Detecting TCP Arjuna Sathiaseelan and Tomasz Radzik Department of Computer Science, King s College London, Strand, London WC2R 2LS {arjuna,radzik}@dcs.kcl.ac.uk Abstract. Numerous studies
More informationWireless Challenges : Computer Networking. Overview. Routing to Mobile Nodes. Lecture 25: Wireless Networking
Wireless Challenges 15-441: Computer Networking Lecture 25: Wireless Networking Force us to rethink many assumptions Need to share airwaves rather than wire Don t know what hosts are involved Host may
More informationCS268: Beyond TCP Congestion Control
TCP Problems CS68: Beyond TCP Congestion Control Ion Stoica February 9, 004 When TCP congestion control was originally designed in 1988: - Key applications: FTP, E-mail - Maximum link bandwidth: 10Mb/s
More informationTCP Congestion Control
TCP Congestion Control What is Congestion The number of packets transmitted on the network is greater than the capacity of the network Causes router buffers (finite size) to fill up packets start getting
More informationTCP Congestion Control
What is Congestion TCP Congestion Control The number of packets transmitted on the network is greater than the capacity of the network Causes router buffers (finite size) to fill up packets start getting
More informationDirect Link Communication I: Basic Techniques. Data Transmission. ignore carrier frequency, coding etc.
Direct Link Communication I: Basic Techniques Link speed unit: bps abstraction Data Transmission ignore carrier frequency, coding etc. Point-to-point link: wired or wireless includes broadcast case Interested
More informationFall 2012: FCM 708 Bridge Foundation I
Fall 2012: FCM 708 Bridge Foundation I Prof. Shamik Sengupta Instructor s Website: http://jjcweb.jjay.cuny.edu/ssengupta/ Blackboard Website: https://bbhosted.cuny.edu/ Intro to Computer Networking Transport
More informationTransport Layer TCP / UDP
Transport Layer TCP / UDP Chapter 6 section 6.5 is TCP 12 Mar 2012 Layers Application Transport Why do we need the Transport Layer? Network Host-to-Network/Physical/DataLink High Level Overview TCP (RFC
More informationEECS 122, Lecture 19. Reliable Delivery. An Example. Improving over Stop & Wait. Picture of Go-back-n/Sliding Window. Send Window Maintenance
EECS 122, Lecture 19 Today s Topics: More on Reliable Delivery Round-Trip Timing Flow Control Intro to Congestion Control Kevin Fall, kfall@cs cs.berkeley.eduedu Reliable Delivery Stop and Wait simple
More informationReliable Transport II: TCP and Congestion Control
Reliable Transport II: TCP and Congestion Control Stefano Vissicchio UCL Computer Science COMP0023 Recap: Last Lecture Transport Concepts Layering context Transport goals Transport mechanisms and design
More informationSatellite Transport Protocol
7 Chapter 5 Satellite Transport Protocol In the previous chapter, we illustrated the performance advantage gained by splitting a TCP connection at a gateway within an access satellite network. Given such
More informationEnhancing TCP Throughput over Lossy Links Using ECN-capable RED Gateways
Enhancing TCP Throughput over Lossy Links Using ECN-capable RED Gateways Haowei Bai AES Technology Centers of Excellence Honeywell Aerospace 3660 Technology Drive, Minneapolis, MN 5548 E-mail: haowei.bai@honeywell.com
More informationImproving Ensemble-TCP Performance on Asymmetric Networks
Improving Ensemble-TCP Performance on Asymmetric Networks Qian Wu Carey Williamson Department of Computer Science University of Saskatchewan Email: carey@cs.usask.ca Abstract For the World Wide Web, the
More informationCRC. Implementation. Error control. Software schemes. Packet errors. Types of packet errors
CRC Implementation Error control An Engineering Approach to Computer Networking Detects all single bit errors almost all 2-bit errors any odd number of errors all bursts up to M, where generator length
More informationTCP Basics : Computer Networking. Overview. What s Different From Link Layers? Introduction to TCP. TCP reliability Assigned reading
TCP Basics 15-744: Computer Networking TCP reliability Assigned reading [FF96] Simulation-based Comparisons of Tahoe, Reno, and SACK TCP L-9 TCP Basics 2 Key Things You Should Know Already Port numbers
More informationInvestigating the Use of Synchronized Clocks in TCP Congestion Control
Investigating the Use of Synchronized Clocks in TCP Congestion Control Michele Weigle (UNC-CH) November 16-17, 2001 Univ. of Maryland Symposium The Problem TCP Reno congestion control reacts only to packet
More informationAn Extension to the Selective Acknowledgement (SACK) Option for TCP
Network Working Group Request for Comments: 2883 Category: Standards Track S. Floyd ACIRI J. Mahdavi Novell M. Mathis Pittsburgh Supercomputing Center M. Podolsky UC Berkeley July 2000 An Extension to
More informationHomework #4. Due: December 2, 4PM. CWND (#pkts)
Homework #4 Due: December 2, 2009 @ 4PM EE122: Introduction to Communication Networks (Fall 2009) Department of Electrical Engineering and Computer Sciences College of Engineering University of California,
More information