--- 1/draft-ietf-ippm-loss-pattern-01.txt 2006-02-04 23:45:33.000000000 +0100 +++ 2/draft-ietf-ippm-loss-pattern-02.txt 2006-02-04 23:45:33.000000000 +0100 @@ -1,18 +1,18 @@ Internet-Draft -Expiration Date: December, 1999 R. Koodli +Expiration Date: April, 2000 R. Koodli R. Ravikanth Nokia Research Center - June, 1999 + October, 1999 One-way Loss Pattern Sample Metrics - + STATUS OF THIS MEMO This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. @@ -128,24 +128,24 @@ and received (denoted by r) packets. r r r x r r x x x r x r r x x x Then, with i assigned as follows 1 1 1 1 1 1 i: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 f(P_i) is, - f(P_i): 0 0 0 1 0 1 0 0 0 1 0 1 1 0 0 0 + f(P_i): 0 0 0 1 0 0 1 1 1 0 1 0 0 1 1 1 and there are four loss periods in the above sequence - begining at P_3, P_6, P_10, and P_13. + beginning at P_3, P_6, P_10, and P_13. 4. Definitions for Samples of One-way Loss Distance, and One-way Loss Period. 4.1 Metric Name: 4.1.1 Type-P-One-Way-Loss-Distance-Stream 4.1.2 Type-P-One-Way-Loss-Period-Stream 4.2 Metric Parameters @@ -181,22 +181,22 @@ the lost packet and the previously lost packet. The sample would consist of pairs. This definition assumes that sequence numbers of successive test packets increase monotonically by one. The loss distance associated with the very first packet loss is considered to be zero. The sequence number of a test packet can be derived from the timeseries sample collected by performing the loss measurement according to the methodology in [AKZ]. For example, if a loss sample consists of {, , , , }, the sequence numbers of the -five test packets sent at T0, T1, T2, T3, and T4 can be 0, 1, 2, 3 and 4 -respectively, or 100, 101, 102, 103 and 104 respectively, etc. +five test packets sent at T0, T1, T2, T3, and T4 can be 0, 1, 2, 3 and +4 respectively, or 100, 101, 102, 103 and 104 respectively, etc. {Packet loss may also be considered as a result of exceeding some delay threshold. This is particularly applicable to delay-sensitive audio (or video) applications. } 4.4.2 Type-P-One-Way-Loss-Period-Stream We start a counter 'n' at an initial value of zero. This counter is incremented by one each time a lost packet satisfies the Definition 3.3. @@ -250,21 +250,23 @@ 4.6 Discussion: The Loss-Distance-Stream metric allows one to study the separation between packet losses. This could be useful in determining a "spread factor" associated with the packet loss rate. For example, for a given packet loss rate, the proposed metric indicates how the losses are spread. On the other hand, the Loss-Period-Stream metric allows the study of loss burstiness for each occurrence of loss. Note that a single loss period of length 'n' can account for a significant portion of the overall -loss rate. +loss rate. Note also that it is possible to measure distance between +loss bursts seprated by one or more successfully received packets: See +Section 5.4, and 5.5 4.7 Sampling Considerations: The proposed metrics can be used independent of the particular sampling method used. We note that Poisson sampling may not yield appropriate values for these metrics for certain real-time applications such as voice over IP, as well as to TCP-based applications. For real-time applications, it may be more appropriate to use the ON-OFF [Sriram] model, in which an ON period starts with certain probability 'p', during which certain number of @@ -311,21 +313,37 @@ "loss period" entry ranging from 1 - Type-P-One-Way-Loss-Period-Total. Thus the total number of pairs in this statistic equals Type-P-One-Way-Loss-Period-Total. In each pair, the "length" is obtained by counting the number of pairs, , in the metric Type-P-One-Way-Loss-Period-Stream which have first entry equal to "loss period." {Note: This statistic represents the number of packets lost in each loss period.} -5.4 Example +5.4 Type-P-One-Way-Inter-Loss-Period-Lengths + +This statistic measures distance between successive loss periods. It +takes the form of a set of pairs +, with the +"loss period" entry ranging from 1 - Type-P-One-Way-Loss-Period-Total, +and "inter-loss-period-length" is the loss distance between the last +packet considered lost in "loss period" 'i-1', and the first packet +considered lost in "loss period" 'i', where 'i' ranges from 2 to +Type-P-One-Way-Loss-Period-Total. The "inter-loss-period-length" +associated with the first "loss period" is defined to be zero. This +statistic allows one to consider, for example, two loss periods each +of length greater than one (implying loss burst), but separated by a +distance of 2 to belong to the same loss burst if such a consideration +is deemed useful. + +5.5 Example We continue with the same example as in Section 4.4.3. The three statistics defined above will have the following values. + Let delta = 2. In Type-P-One-Way-Loss-Distance-Stream {<0,0>,<0,1>,<0,0>,<0,0>,<3,1>,<0,0>,<2,1>,<0,0>,<2,1>,<1,1>}, there are 3 loss distances that violate the delta of 2. Thus, Type-P-One-Way-Loss-Noticeable-Rate = 3/5 @@ -338,38 +356,44 @@ Type-P-One-Way-Loss-Period-Total = 4 + In Type-P-One-Way-Loss-Period-Stream {<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>}, the lengths of individual loss periods are 1, 1, 1 and 2 respectively. Thus, Type-P-One-Way-Loss-Period-Lengths = {<1,1>,<2,1>,<3,1>,<4,2>} ++ In Type-P-One-Way-Loss-Period-Stream + {<0,0>,<1,1>,<0,0>,<0,0>,<2,1>,<0,0>,<3,1>,<0,0>,<4,1>,<4,1>}, the + loss periods 1 and 2 are separated by 3 (5-2), loss periods 2 and 3 + are separated by 2 (7-5), and 3 and 4 are separated by 2 (9-7). + Thus, + Type-P-One-Way-Inter-Loss-Period-Lengths = {<1,0>,<2,3>,<3,2>,<4,2>} + 6. Security Considerations Since this draft proposes sample metrics based on the base loss metric - defined in [AKZ], it inherits the security considerations mentioned in [AKZ]. 7. Acknowledgements Many thanks to Matt Zekauskas for the constructive feedback on the draft. -Thanks to Guy Almes for encouraging the work, and Vern Paxson for all the -comments during the IETF meetings. +Thanks to Guy Almes for encouraging the work, and Vern Paxson for the +comments during the IETF meetings. Thanks to Steve Glass for making the +presentation at the Oslo meeting. 8. References [AKZ] G. Almes and S. Kalindindi and M. Zekauskas, "A One-way Packet - Loss Metric for IPPM", Internet Draft , - May 1999 + Loss Metric for IPPM", RFC 2680, September 1999 [Bolot] J.-C. Bolot and A. vega Garcia, "The case for FEC-based error control for Packet Audio in the Internet", ACM Multimedia Systems, 1997. [Borella] M. S. Borella, D. Swider, S. Uludag, and G. B. Brewster, "Internet Packet Loss: Measurement and Implications for End-to-End QoS," Proceedings, International Conference on Parallel Processing, August 1998. @@ -390,21 +413,21 @@ TCP-friendly rate adjustment protocol for continuous media flows over best-effort networks", short paper presentation in ACM SIGMETRICS'99. Available as Umass Computer Science tech report from ftp://gaia.cs.umass.edu/pub/Padhye98-tcp-friendly-TR.ps.gz [Paxson] V. Paxson, "End-to-end Internet packet dynamics", Computer Communication review, Proceedings of ACM SIGCOMM'97 Conference, Cannes, France, September 1997, 27(4), pages 139-152, October 1997 [frame-work] V. Paxson, G. Almes, J. Mahdavi, and M. Mathis, - "Framework for IP Performance Metrics", RFC 2330. + "Framework for IP Performance Metrics", RFC 2330, May 1998. [Sriram] K. Sriram and W. Whitt, "Characterizing superposition arrival processes in packet multiplexers for voice and data", IEEE Journal on Selected Areas of Communication, September 1986, pages 833-846 [Yajnik] M. Yajnik, J. Kurose and D. Towsley, "Packet loss correlation in the MBONE multicast network", Proceedings of IEEE Global Internet, London, UK, November 1996.