Network Working Group I. Rhee Internet-Draft NCSU Intended status: Experimental L. Xu Expires: March 1, 2008 UNL S. Ha NCSU August 29, 2007 CUBIC for Fast Long-Distance Networks draft-rhee-tcpm-cubic-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 1, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Rhee, et al. Expires March 1, 2008 [Page 1] Internet-Draft CUBIC August 2007 Abstract CUBIC is an extension to the current TCP standards. The protocol differs from the current TCP standards only in the congestion window adjustment function in the sender side. In particular, it uses a cubic function instead of a linear window increase of the current TCP standards to improve scalability and stability under fast and long distance networks. BIC-TCP, a predecessor of CUBIC, has been a default TCP adopted by Linux since year 2005 and has already been deployed globally and in use for several years by the Internet community at large. CUBIC is using a similar window growth function as BIC-TCP and is designed to be less aggressive and fairer to TCP in bandwidth usage than BIC-TCP while maintaining the strengths of BIC- TCP such as stability, window scalability and RTT fairness. Through extensive testing in various Internet scenarios, we believe that CUBIC is safe for deployment and testing in the global Internet. The intent of this document is to provide the protocol specification of CUBIC for a third party implementation and solicit the community feedback through experimentation on the performance of CUBIC. We expect this document to be eventually published as an experimental RFC. Rhee, et al. Expires March 1, 2008 [Page 2] Internet-Draft CUBIC August 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. CUBIC Congestion Control . . . . . . . . . . . . . . . . . . . 7 2.1. Window growth function . . . . . . . . . . . . . . . . . . 7 2.2. TCP-friendly region . . . . . . . . . . . . . . . . . . . 7 2.3. Concave region . . . . . . . . . . . . . . . . . . . . . . 8 2.4. Convex region . . . . . . . . . . . . . . . . . . . . . . 8 2.5. Multiplicative decrease . . . . . . . . . . . . . . . . . 9 2.6. Fast convergence . . . . . . . . . . . . . . . . . . . . . 9 3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1. Fairness to standard TCP . . . . . . . . . . . . . . . . . 11 3.2. Using Spare Capacity . . . . . . . . . . . . . . . . . . . 13 3.3. Difficult Environments . . . . . . . . . . . . . . . . . . 13 3.4. Investigating a Range of Environments . . . . . . . . . . 14 3.5. Protection against Congestion Collapse . . . . . . . . . . 14 3.6. Fairness within the Alternative Congestion Control Algorithm. . . . . . . . . . . . . . . . . . . . . . . . . 14 3.7. Performance with Misbehaving Nodes and Outside Attackers . . . . . . . . . . . . . . . . . . . . . . . . 14 3.8. Responses to Sudden or Transient Events . . . . . . . . . 14 3.9. Incremental Deployment . . . . . . . . . . . . . . . . . . 14 4. Security Considerations . . . . . . . . . . . . . . . . . . . 15 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.1. Normative References . . . . . . . . . . . . . . . . . . . 17 6.2. Informative References . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Intellectual Property and Copyright Statements . . . . . . . . . . 20 Rhee, et al. Expires March 1, 2008 [Page 3] Internet-Draft CUBIC August 2007 1. Introduction The low utilization problem of TCP in fast long-distance networks is well documented in [K03][RFC3649]. This problem arises from a slow increase of congestion window following a congestion event in a network with a large bandwidth delay product (BDP). Our experience [H+06] indicates that this problem is frequently observed even in the range of congestion window sizes over several hundreds of packets (each packet is sized around 1000 bytes) especially under a network path with over 100ms round-trip times (RTTs). This problem is equally applicable to all Reno style TCP standards and their variants, including TCP-RENO [RFC2581], TCP-NewReno [RFC3782], TCP- SACK [RFC2018], SCTP [RFC2960], TFRC [RFC3448] that use the same linear increase function for window growth, which we refer to collectively as Standard TCP below. CUBIC is a modification to the congestion control mechanism of Standard TCP, in particular, to the window increase function of Standard TCP senders, to remedy this problem. It uses a cubic increase function in terms of the elapsed time from the last congestion event. While most alternative algorithms to Standard TCP uses a convex increase function where after a loss event, the window increment is always increasing, CUBIC uses both the concave and convex profiles of a cubic function for window increase. After a window reduction following a loss event, it registers the window size where it got the loss event as W_max and performs a multiplicative decrease of congestion window and the regular fast recovery and retransmit of Standard TCP. After it enters into congestion avoidance from fast recovery, it starts to increase the window using the concave profile of the cubic function. The cubic function is set to have its plateau at W_max so the concave growth continues until the window size becomes W_max. After that, the cubic function turns into a convex profile and the convex window growth begins. This style of window adjustment (concave and then convex) improves protocol and network stability while maintaining high network utilization [C+07]. This is because the window size remains almost constant, forming a plateau around W_max where network utilization is deemed highest and under steady state, most window size samples of CUBIC are close to W_max, thus promoting high network utilization and protocol stability. Note that protocols with convex increase functions have the maximum increments around W_max and introduces a large number of packet bursts around the saturation point of the network, likely causing frequent loss synchronizations among competing flows. Another notable feature of CUBIC is that its window increase rate is mostly independent of RTT, and follows a (cubic) function of the elapsed time since the last loss event. This feature promotes per- Rhee, et al. Expires March 1, 2008 [Page 4] Internet-Draft CUBIC August 2007 flow fairness to Standard TCP as well as RTT-fairness. Note that Standard TCP performs well under short RTT and small bandwidth (or small BDP) networks. Only in a large long RTT and large bandwidth (or large BDP) networks, it has the scalability problem. An alternative protocol to Standard TCP designed to be friendly to Standard TCP at a per-flow basis must operate must increase its window much less aggressively in small BDP networks than in large BDP networks. In CUBIC, its window growth rate is slowest around the inflection point of the cubic function and this function does not depend on RTT. In a smaller BDP network where Standard TCP flows are working well, the absolute amount of the window decrease at a loss event is always smaller because of the multiplicative decrease. Therefore, in CUBIC, the starting window size after a loss event from which the window starts to increase, is smaller in a smaller BDP network, thus falling nearer to the plateau of the cubic function where the growth rate is slowest. By setting appropriate values of the cubic function parameters, CUBIC sets its growth rate always no faster than Standard TCP around its inflection point. When the cubic function grows slower than the window of Standard TCP, CUBIC simply follows the window size of Standard TCP to ensure fairness to Standard TCP in a small BDP network. We call this region where CUBIC behaves like Standard TCP, the TCP-friendly region. CUBIC maintains the same window growth rate independent of RTTs outside of the TCP-friendly region, and flows with different RTTs have the similar window sizes under steady state when they operate outside the TCP-friendly region. This ensures CUBIC flows with different RTTs to have their bandwidth shares linearly proportional to the inverse of their RTT ratio (the longer RTT, the smaller the share). This behavior is the same as that of Standard TCP under high statistical multiplexing environments where packet losses are independent of individual flow rates. However, under low statistical multiplexing environments, the bandwidth share ratio of Standard TCP flows with different RTTs is squarely proportional to the inverse of their RTT ratio [XHR04]. CUBIC always ensures the linear ratio independent of the levels of statistical multiplexing. This is an improvement over Standard TCP. While there is no consensus on a particular bandwidth share ratios of different RTT flows, we believe that under wired Internet, use of the linear share notion seems more reasonable than equal share or a higher order shares. HTCP [LS05] currently uses the equal share. CUBIC sets the multiplicative window decrease factor to 0.2 while Standard TCP uses 0.5. While this improves the scalability of the protocol, a side effect of this decision is slower convergence especially under low statistical multiplexing environments. This design choice is following the observation that the author of HSTCP [RFC3649] has made along with other researchers (e.g., [GV02]): the Rhee, et al. Expires March 1, 2008 [Page 5] Internet-Draft CUBIC August 2007 current Internet becomes more asynchronous with less frequent loss synchronizations with high statistical multiplexing. Under this environment, even strict MIMD can converge. CUBIC flows with the same RTT always converge to the same share of bandwidth independent of statistical multiplexing, thus achieving intra-protocol fairness. We also find that under the environments with sufficient statistical multiplexing, the convergence speed of CUBIC flows is reasonable. In the ensuing sections, we provide the exact specification of CUBIC and discuss the safety features of CUBIC following the guidelines specified in [FA06]. Rhee, et al. Expires March 1, 2008 [Page 6] Internet-Draft CUBIC August 2007 2. CUBIC Congestion Control 2.1. Window growth function CUBIC maintains the acknowledgment (ACK) clocking of Standard TCP by increasing congestion window only at the reception of ACK. The protocol does not make any change to the fast recovery and retransmit of TCP- NewReno [RFC3782] and TCP-SACK [RFC2018]. During congestion avoidance after fast recovery, CUBIC changes the window update algorithm of Standard TCP. Suppose that W_max is the window size before the window is reduced in the last fast retransmit and recovery. The window growth function of CUBIC uses the following function: W(t) = C*(t-K)^3 + W_max (Eq. 1) where C is a CUBIC parameter, t is the elapsed time from the last window reduction,and K is the time period that the above function takes to increase W to W_max when there is no further loss event and is calculated by using the following equation: K = cubic_root(W_max*beta/C) (Eq. 2) where beta is the multiplication decrease factor. Upon receiving an ACK during congestion avoidance, CUBIC computes the window growth rate during the next RTT period using Eq. 1. It sets W(t+RTT) as the candidate target value of congestion window. Suppose that the current window size is cwnd. Depending on the value of cwnd, CUBIC runs in three different modes. First, if cwnd is less than the window size that Standard TCP would reach at time t after the last loss event, then CUBIC is in the TCP friendly region (we describe below how to determine this window size of Standard TCP in term of time t). Otherwise, if cwnd is less than W_max, then CUBIC is the concave region, and if cwnd is larger than W_max, CUBIC is in the convex region. Below, we describe the exact actions taken by CUBIC in each region. 2.2. TCP-friendly region When receiving an ACK in congestion avoidance, we first check whether the protocol is in the TCP region or not. This is done as follows. We can analyze the window size of Standard TCP in terms of the elapsed time t. Using a simple analysis in [FHP00], we can analyze the average window size of additive increase and multiplicative decrease (AIMD) with an additive factor alpha and a multiplicative factor beta to be the following function: Rhee, et al. Expires March 1, 2008 [Page 7] Internet-Draft CUBIC August 2007 1/RTT (alpha/2 * (2-beta)/beta * 1/p)^0.5 (Eq. 3) By the same analysis, the average window size of Standard TCP with alpha 1 and beta 0.5 is 1/RTT (3/2 *1/p)^0.5. Thus, for Eq. 3 to be the same as that of Standard TCP, alpha must be equal to 3*beta/ (2-beta). As Standard TCP increases its window by alpha per RTT, we can get the window size of Standard TCP in terms of the elapsed time t as follows: W_tcp(t) = W_max*(1-beta) + 3*beta/(2-beta)* t/RTT (Eq. 4) If cwnd is less than W_tcp(t), then the protocol is in the TCP friendly region and cwnd is set to W_tcp(t) at each reception of ACK. 2.3. Concave region When receiving an ACK in congestion avoidance, if the protocol is not in the TCP-friendly region and cwnd is less than W_max, then the protocol is in the concave region. In this region, cwnd is incremented by (W(t+RTT) - cwnd)/cwnd. 2.4. Convex region When the window size of CUBIC is larger than W_max, it passes the plateau of the cubic function after which CUBIC follows the convex profile of the cubic function. Since cwnd is larger than the previous saturation point W_max, this indicates that the network conditions might have been perturbed since the last loss event, possibly implying more available bandwidth after some flow departures. Since the Internet is highly asynchronous, some amount of perturbation is always possible without causing a major change in available bandwidth. In this phase, CUBIC is being very careful by very slowly increasing its window size. The convex profile ensures that the window increases very slowly at the beginning and gradually increases its growth rate. We also call this phase as the maximum probing phase since CUBIC is searching for a new W_max. During the convex region, the window growth rate of CUBIC can be very high at some time. While the convex window growth in this phase seems appropriate (as most loss-based TCP alternative protocols use a convex function), there is no consensus on what increase rate is appropriate. For the time being, we clamp the growth rate to a constant maximum rate, called max_increment_rate, not to cause too much burst into the network. We set max_increment_rate to 160 packets per second. To be exact, if the protocol is the convex region outside the TCP-friendly region, when receiving an ACK, we uses the following code. Rhee, et al. Expires March 1, 2008 [Page 8] Internet-Draft CUBIC August 2007 W_inc = W(t+RTT) - cwnd; if (W_inc > max_increment_rate * RTT) // max clamping W_inc = max_increment_rate * RTT; cwnd = cwnd + W_inc/cwnd; Figure 1 We found this maximum increment rate is safe for the deployment of the current Internet which is equivalent to 16 packets per RTT in a 100 ms RTT network, to 1.6 packets per RTT in a 10 ms RTT network (since in this network, CUBIC is running in the TCP friendly region, its increasing rate follows that of Standard TCP). Alternative to this clamping, the increasing function of HSTCP can be considered whose increase rate is a function of its current window size. Since the scalability of CUBIC under steady state is mostly determined by the concave profile of the cubic function where no clamping is applied, the clamping does not affect the scalability of the protocol under steady state. 2.5. Multiplicative decrease When a packet loss occurs, CUBIC reduces its window size by a factor of beta. We set beta to 0.2. W_max = cwnd; // remember the window size before reduction cwnd = cwnd * (1-beta); // window reduction Figure 2 A side effect of setting beta to a smaller value than 0.5 is slower convergence. We believe that while a more adaptive setting of beta could result in faster convergence, it will make the analysis of the protocol much harder. This adaptive adjustment of beta is an item for the next version of CUBIC. 2.6. Fast convergence To improve the convergence speed of CUBIC, we add a heuristic in the protocol. When a new flow joins the network, existing flows in the network need to give up their bandwidth shares to allow the flow some room for growth if the existing flows have been using all the bandwidth of the network. To increase this release of bandwidth by existing flows, we add the following mechanism called fast convergence. With fast convergence, when a loss event occurs, before a window reduction of congestion window, a flow remembers the last value of W_max before it updates W_max for the current loss event. Let us Rhee, et al. Expires March 1, 2008 [Page 9] Internet-Draft CUBIC August 2007 call the last value of W_max to be W_last_max. if (W_max < W_last_max){ // check downward trend, W_last_max = W_max; // remember the last W_max. W_max = W_max*(2-beta)/2; // further reduce W_max. } else // check upward trend. W_last_max = W_max // remember the last W_max. Figure 3 This allows W_max to be slightly less than the original W_max. Since flows spend most of time around their W_max, flows with larger bandwidth shares tend to spend more time around the plateau allowing more time for flows with smaller shares to increase their windows. Rhee, et al. Expires March 1, 2008 [Page 10] Internet-Draft CUBIC August 2007 3. Discussion With a deterministic loss model where the number of packets between two successive lost events is always 1/p, CUBIC always operates with the concave window profile which greatly simplifies the performance analysis of CUBIC. The average window size of CUBIC can be obtained by the following function: (C*(4-beta)/4/beta)^0.25 * RTT^0.75 / p^0.75 (Eq. 5) To ensure fairness to Standard TCP based on our argument in the introduction, we set C to 0.4. We find that this value of C allows the size of the TCP friendly region to be large enough to encompass most of the environments where Standard TCP performs well while preserving the scalability of the window growth function. With beta set to 0.2, the above formula is reduced to: 1.17 * RTT^0.75 / p^0.75 (Eq. 6) Eq. 6 is used to argue the fairness of CUBIC to Standard TCP and its safety for deployment below. 3.1. Fairness to standard TCP In environments where standard TCP is able to make reasonable use of the available bandwidth, CUBIC does not significantly change this state. Standard TCP performs well in the following two types of networks: 1. networks with a small bandwidth-delay product (BDP). 2. networks with a short RTT, but not necessarily a small BDP CUBIC is designed to behave very similarly to standard TCP in the above two types of networks. The following two tables show the average window size of standard TCP, HSTCP, and CUBIC. The average window size of standard TCP and HSTCP is from [RFC3649]. The average window size of CUBIC is calculated by using Eq. 6 and CUBIC TCP friendly mode. Rhee, et al. Expires March 1, 2008 [Page 11] Internet-Draft CUBIC August 2007 +-------------+---------------+-----------------+-----------------+ | Loss Rate P | Average TCP W | Average HSTCP W | Average CUBIC W | +-------------+---------------+-----------------+-----------------+ | 10^-2 | 12 | 12 | 12 | | | | | | | 10^-3 | 38 | 38 | 38 | | | | | | | 10^-4 | 120 | 263 | 209 | | | | | | | 10^-5 | 379 | 1795 | 1175 | | | | | | | 10^-6 | 1200 | 12279 | 6609 | | | | | | | 10^-7 | 3795 | 83981 | 37165 | | | | | | | 10^-8 | 12000 | 574356 | 208058 | +-------------+---------------+-----------------+-----------------+ Response function of standard TCP, HSTCP, and CUBIC in networks with RTT = 100ms. The average window size W is in MSS-sized segments. Table 1 +-------------+---------------+-----------------+-----------------+ | Loss Rate P | Average TCP W | Average HSTCP W | Average CUBIC W | +-------------+---------------+-----------------+-----------------+ | 10^-2 | 12 | 12 | 12 | | | | | | | 10^-3 | 38 | 38 | 38 | | | | | | | 10^-4 | 120 | 263 | 120 | | | | | | | 10^-5 | 379 | 1795 | 379 | | | | | | | 10^-6 | 1200 | 12279 | 1200 | | | | | | | 10^-7 | 3795 | 83981 | 6588 | | | | | | | 10^-8 | 12000 | 574356 | 36996 | +-------------+---------------+-----------------+-----------------+ Response function of standard TCP, HSTCP, and CUBIC in networks with RTT = 10ms. The average window size W is in MSS-sized segments. Table 2 Both tables show that CUBIC is more friendly to TCP than HSTCP, especially in networks with a short RTT where TCP performs reasonably Rhee, et al. Expires March 1, 2008 [Page 12] Internet-Draft CUBIC August 2007 well. For example, in a network with RTT = 10ms and p=10^-6, TCP has an average window of 1200 packets. If the packet size is 1500 bytes, then TCP can achieve an average rate of 1.44 Gbps. In this case, CUBIC achieves exactly the same rate as Standard TCP, whereas HSTCP is about ten times more aggressive than Standard TCP. 3.2. Using Spare Capacity CUBIC uses a more aggressive window growth function than Standard TCP under long RTT and high bandwidth networks. The following table shows that to achieve 10Gbps rate, standard TCP requires a packet loss rate of 2.0e-10, while CUBIC requires a packet loss rate of 3.4e-8. +------------------+-----------+---------+---------+---------+ | Throughput(Mbps) | Average W | TCP P | HSTCP P | CUBIC P | +------------------+-----------+---------+---------+---------+ | 1 | 8.3 | 2.0e-2 | 2.0e-2 | 2.0e-2 | | | | | | | | 10 | 83.3 | 2.0e-4 | 3.9e-4 | 3.3e-4 | | | | | | | | 100 | 833.3 | 2.0e-6 | 2.5e-5 | 1.6e-5 | | | | | | | | 1000 | 8333.3 | 2.0e-8 | 1.5e-6 | 7.3e-7 | | | | | | | | 10000 | 83333.3 | 2.0e-10 | 1.0e-7 | 3.4e-8 | +------------------+-----------+---------+---------+---------+ Required packet loss rate for Standard TCP, HSTCP, and CUBIC to achieve a certain throughput. We use 1500-Byte Packets and a Round- Trip Time of 0.1 Seconds. Table 3 Our test results in [H+06] indicate that CUBIC uses the spare bandwidth left unused by existing Standard TCP flows in the same bottleneck link without taking away much bandwidth from the existing flows. 3.3. Difficult Environments CUBIC is designed to remedy the poor performance of TCP in fast long- distance networks. It is not designed to improve TCP performance for wireless networks. Thus, its performance is no worse than that of regualar TCP. Rhee, et al. Expires March 1, 2008 [Page 13] Internet-Draft CUBIC August 2007 3.4. Investigating a Range of Environments CUBIC has been extensively studied by using both NS-2 simulation and test-bed experiments covering a wide range of network environments. More information can be found in [H+06]. 3.5. Protection against Congestion Collapse In case that there is congestion collapse, CUBIC behaves likely standard TCP since CUBIC modifies only the window adjustment algorithm of TCP. Thus, it does not modify the ACK clocking and Timeout behaviors of Standard TCP. 3.6. Fairness within the Alternative Congestion Control Algorithm. CUBIC ensures convergence of competing CUBIC flows in the same bottleneck links to an equal bandwidth share. When competing flows have different RTTs, their bandwidth shares are linearly proportional to the inverse of their RTT ratios. This is true independent of the level of statistical multiplexing in the link. 3.7. Performance with Misbehaving Nodes and Outside Attackers This is not considered in the current CUBIC. 3.8. Responses to Sudden or Transient Events In case that there is a sudden congestion, a routing change, or a mobility event, CUBIC behaves the same as Standard TCP. 3.9. Incremental Deployment CUBIC requires only the change of TCP senders, and does not require any assistant of routers. Rhee, et al. Expires March 1, 2008 [Page 14] Internet-Draft CUBIC August 2007 4. Security Considerations This proposal makes no changes to the underlying security of TCP. Rhee, et al. Expires March 1, 2008 [Page 15] Internet-Draft CUBIC August 2007 5. IANA Considerations There are no IANA considerations regarding this document. Rhee, et al. Expires March 1, 2008 [Page 16] Internet-Draft CUBIC August 2007 6. References 6.1. Normative References [RFC2018] Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP Selective Acknowledgment Options", RFC 2018, October 1996. [RFC2581] Allman, M., Paxson, V., and W. Stevens, "TCP Congestion Control", RFC 2581, April 1999. [RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M., Zhang, L., and V. Paxson, "Stream Control Transmission Protocol", RFC 2960, October 2000. [RFC3448] Handley, M., Floyd, S., Padhye, J., and J. Widmer, "TCP Friendly Rate Control (TFRC): Protocol Specification", RFC 3448, January 2003. [RFC3782] Floyd, S., Henderson, T., and A. Gurtov, "The NewReno Modification to TCP's Fast Recovery Algorithm", RFC 3782, April 2004. 6.2. Informative References [C+07] Cai, H., Eun, D., Ha, S., Rhee, I., and L. Xu, "Stochastic Ordering for Internet Congestion Control and its Applications", In Proceedings of IEEE INFOCOM , May 2007. [FA06] Floyd, S. and M. Allman, "Specifying New Congestion Control Algorithms", Internet-draft draft-floyd-tsvwg-cc-alt-00.txt , December 2006. [FHP00] Floyd, S., Handley, M., and J. Padhye, "A Comparison of Equation-Based and AIMD Congestion Control", May 2000. [GV02] Gorinsky, S. and H. Vin, "Extended Analysis of Binary Adjustment Algorithms", Technical Report TR2002-29, Department of Computer Sciences , The University of Texas at Austin , August 2002. [H+06] Ha, S., Kim, Y., Le, L., Rhee, I., and L. Xu, "A Step toward Realistic Performance Evaluation of High-Speed TCP Variants", International Workshop on Protocols for Fast Long-Distance Networks , February 2006. [K03] Kelly, T., "Scalable TCP: Improving Performance in HighSpeed Wide Area Networks", ACM SIGCOMM Computer Rhee, et al. Expires March 1, 2008 [Page 17] Internet-Draft CUBIC August 2007 Communication Review , April 2003. [LS05] Leith, D. and R. Shorten, "H-TCP: TCP Congestion Control for High Bandwidth-Delay Product Paths", Internet-draft draft-leith-tcp-htcp-00 , June 2005. [RFC3649] Floyd, S., "HighSpeed TCP for Large Congestion Windows", RFC 3649, December 2003. [XHR04] Xu, L., Harfoush, K., and I. Rhee, "Binary Increase Congestion Control for Fast, Long Distance Networks", In Proceedings of IEEE INFOCOM , March 2004. Rhee, et al. Expires March 1, 2008 [Page 18] Internet-Draft CUBIC August 2007 Authors' Addresses Injong Rhee North Carolina State University Department of Computer Science Raleigh, NC 27695-7534 US Email: rhee@ncsu.edu Lisong Xu University of Nebraska-Lincoln Department of Computer Science and Engineering Lincoln, NE 68588-0115 US Email: xu@cse.unl.edu Sangtae Ha North Carolina State University Department of Computer Science Raleigh, NC 27695-7534 US Email: sha2@ncsu.edu Rhee, et al. Expires March 1, 2008 [Page 19] Internet-Draft CUBIC August 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Rhee, et al. Expires March 1, 2008 [Page 20]