INTERNET-DRAFT Manjunath Iyer Expires: December 18, 2006 Celstream June 18, 2006 Shifted feedback technique for congestion notification draft-manjunath-ipfix-shifted-feedback-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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 18, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract The [RFC2581] provides a mechanism to indicate the congestion information of the network to the source. In this draft, time shifting of the signal before usage is suggested. The time shifting operation effectively counters the impact of the self similarity of the traffic that originates in a DiffServe network model as a result of the aggregation. Manjunath Expires December18, 2006 [Page 1] Internet-Draft Shifted feedback Architecture June 2006 1. Introduction 1.1 Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 1.2 Overview In a TCP network, a feedback signal indicating the network status is provided from the end user of the information to the source as given in [RFC2581]. Although the signal can be effectively utilized for adjusting the TCP window size and control the traffic effectively, by the time the signal reaches the source, the network characteristics would change [RFC2488]. The draft uses a predicted feedback signal.The formula for computing the TCP window width is given in[WYX01] Logically, it would be correct to synchronize the loss probability and the packet size that exist at any instance of time t. Prediction of the loss rate would be required to be used in the formula. 1.3 Signal processing with the feedback signal The network traffic makes use of DiffServ defined in [RFC2474] for meeting the service quality requirements. The DiffServ involves aggregation of the traffic resulting in self similarity and long range dependency in the traffic. The self similar traffic is found to have adverse effect on the network resources making it tougher to meet the quality of service (QoS). Shaping the feedback signal provides an opportunity to counter the impact of the aggregation and self similarity in the traffic. 1.4. Impact on the resources The shifted feedback signal can foresee the evolving network and control the data transfer rates in such a way that the network does nor get congested and at the same time the resources are used efficiently. Pumping in packets to a choked network results in further delays and retransmissions. The signal processing SHOULD consider both these factors. One of the simplest processing over the feedback signal is to control the shifts. When the prediction is done with a time shift equal to the round trip time (RTT), the value going in to the formula matches and the resource utilization would be maximum. It results in reduced packet loss,reduced delay and jitter that is extremely useful for real time audio or video traffic. For a time shift less thane RTT the advantage would be reduced proportionally. Manjunath Expires December18, 2006 [Page 2] Internet-Draft Shifted feedback Architecture June 2006 The RTT value may be deduced from the feedback signal with the usage of time stamps. The usage of time stamps is given in [RFC3161]. The predicted value of RTT may be used to compute the predicted value of the signal over that time duration. One advantage of the self similarity in the traffic is that the traffic shaper introduced in such a loop would be self similar. All the parameters such as RTT would start becoming self similar and easily predictable. In case where RTT can not be computed, or computationally expensive, a constant value may be assumed. 2. Implementation Various implementation models are possible depending up on the accuracy of the required feedback suitable for the context. In a client server model the predictions may be done at the client end and then embedded in the feedback signal.It would reduce the burden on the server that has to handle multiple streams. In a duplex peer to per model, still the originator of the feedback MAY take the responsibility and compute the feedback signal. For further accuracy, the data source can use the time stamps and check it against the RTT or the time and apply corrections. Some processing over-head is involved if the data source has to get in to the computation and prediction of the loss probability. To reduce the time, shifted predicted signals may be used. The data source receives the feedback signal and easily shift it depending up on the delay with respect to the anticipated time. It reduces the computation time. Manjunath Expires December18, 2006 [Page 3] Internet-Draft Shifted feedback Architecture June 2006 3. Security Considerations The document concerns security of forward as well as feedback path signals 1 The feedback signal MUST reach the source in time. Its absence could be an indication of attack on the network. 2 An abnormal variations in the resource requirement indicated by the feedback signal MAY be interpreted as spam or intrusion on the network 4. IANA Considerations This document has no actions for IANA. Manjunath Expires December18, 2006 [Page 4] Internet-Draft Shifted feedback Architecture June 2006 5. References 5.1 Normative References [RFC2119] Bradner, S. "Key Words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 5.2 Informative References [RFC2581] M.Allman, V. Paxson and W. Stevens, "TCP Congestion Control", RFC 2581, April 1999. [RFC2488] M. Allman., D. Glover, and L. Sanchez, "Enhancing TCP over Satellite Channels using Standard Mechanisms", RFC 2488, January 1999. [RFC2474] K. Nichols, R., S. Blake., F. Baker and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers ", RFC 2474, December 1998. [RFC3161] C. Adams, P. Cain., D. Pinkas and R. Zuccherato, "Internet X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)", RFC 3161, August 2001. [WYX01] Wei Wu, Yong Ren and Xiuming Shan, "Analysis on adjustment-based TCP-friendly congestion control:fairness and stability",Dept. of Electron. Eng., Tsinghua Univ., Beijing ; In LCN 2001 Manjunath Expires December18, 2006 [Page 5] Internet-Draft Shifted feedback Architecture June 2006 6. Author's Address Manjunath.R Celstream. 9,Prestige bluechip Opp.Christ college Bangalore-560029 INDIA Phone: 80-41191919 E-mail: manju_r_99@yahoo.com Manjunath Expires December18, 2006 [Page 6] Internet-Draft Shifted feedback Architecture June 2006 7. Acknowledgements The author acknowledges the creators of the RFCs referred in this draft for the valuable information and the extensions based on which this draft has been created The following individuals directly contributed for encouragement, identifying Issues, suggesting resolutions to the issues found in this document: Srinivas Rao, Rangaraj. This document benefited from all these contributions. The author acknowledges the encouragement and services rendered by his family members and friends during the preparation of the document. Manjunath Expires December18, 2006 [Page 7] Internet-Draft Shifted feedback Architecture June 2006 8. Full Copyright Statement Copyright (C) The Internet Society (2006). 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 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. Manjunath Expires December18, 2006 [Page 8] Internet-Draft Shifted feedback Architecture June 2006 9. 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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. Manjunath Expires December 18, 2006 [Page 9]