draft-ietf-ippm-loss-pattern-04.txt | draft-ietf-ippm-loss-pattern-05.txt | |||
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IP Performance Metrics (IPPM) WG Rajeev Koodli | IP Performance Metrics (IPPM) WG Rajeev Koodli | |||

INTERNET DRAFT Nokia Research Center | INTERNET DRAFT Nokia Research Center | |||

21 November 2000 R. Ravikanth | 20 July 2001 R. Ravikanth | |||

Axiowave | Axiowave | |||

One-way Loss Pattern Sample Metrics | One-way Loss Pattern Sample Metrics | |||

<draft-ietf-ippm-loss-pattern-04.txt> | <draft-ietf-ippm-loss-pattern-05.txt> | |||

STATUS OF THIS MEMO | STATUS OF THIS MEMO | |||

This document is an Internet-Draft and is in full conformance with all | This document is an Internet-Draft and is in full conformance with all | |||

provisions of Section 10 of RFC2026. | provisions of Section 10 of RFC2026. | |||

Internet-Drafts are working documents of the Internet Engineering Task | Internet-Drafts are working documents of the Internet Engineering Task | |||

Force (IETF), its areas, and its working groups. Note that other groups | Force (IETF), its areas, and its working groups. Note that other groups | |||

may also distribute working documents as Internet- Drafts. | may also distribute working documents as Internet- Drafts. | |||

skipping to change at page 2, line 47 | skipping to change at page 2, line 47 | |||

- it provides consistent usage of singleton metric definition for | - it provides consistent usage of singleton metric definition for | |||

different behaviors (e.g., a single definition of packet loss | different behaviors (e.g., a single definition of packet loss | |||

is needed for capturing burst of losses, 'm out of n' losses | is needed for capturing burst of losses, 'm out of n' losses | |||

etc. Otherwise, the metrics would have to be fundamentally | etc. Otherwise, the metrics would have to be fundamentally | |||

different) | different) | |||

- it allows re-use of the methodologies specified for the singleton | - it allows re-use of the methodologies specified for the singleton | |||

metric with modifications whenever necessary | metric with modifications whenever necessary | |||

- it clearly separates few base metrics from many Internet behaviors | - it clearly separates few base metrics from many Internet behaviors | |||

Following the guidelines in [frame-work], this | Following the guidelines in [frame-work], this | |||

translates to deriving *sample* metrics from the respective | translates to deriving sample metrics from the respective | |||

singletons. The process of deriving sample metrics from the singletons | singletons. The process of deriving sample metrics from the singletons | |||

is specified in [frame-work], [AKZ], and others. | is specified in [frame-work], [AKZ], and others. | |||

In the following sections, we apply this approach to a particular | In the following sections, we apply this approach to a particular | |||

Internet behavior, namely the packet loss process. | Internet behavior, namely the packet loss process. | |||

3. Basic Definitions: | 3. Basic Definitions: | |||

3.1. Bursty loss: | 3.1. Bursty loss: | |||

skipping to change at page 3, line 24 | skipping to change at page 3, line 24 | |||

packets which may or may not be separated by successfully | packets which may or may not be separated by successfully | |||

received packets. | received packets. | |||

Example. Let packet with sequence number 50 be considered lost | Example. Let packet with sequence number 50 be considered lost | |||

immediately after packet with sequence number 20 was | immediately after packet with sequence number 20 was | |||

considered lost. The loss distance is 30. | considered lost. The loss distance is 30. | |||

Note that this definition does not specify exactly how to | Note that this definition does not specify exactly how to | |||

associate sequence numbers with test packets. In other words, from | associate sequence numbers with test packets. In other words, from | |||

a timeseries sample of test packets, one may derive the sequence | a timeseries sample of test packets, one may derive the sequence | |||

numbers. However, these sequence numbers must to be consecutive | numbers. However, these sequence numbers must be consecutive | |||

integers. | integers. | |||

Typo in last sentence. | ||||

3.3. Loss period: | 3.3. Loss period: | |||

Let P_i be the i'th packet. | Let P_i be the i'th packet. | |||

Define f(P_i) = 1 if P_i is lost, 0 otherwise. | Define f(P_i) = 1 if P_i is lost, 0 otherwise. | |||

Then, a loss period begins if f(P_i) = 1 and f(P_(i-1)) = 0 | Then, a loss period begins if f(P_i) = 1 and f(P_(i-1)) = 0 | |||

Example. Consider the following sequence of lost (denoted by x) | Example. Consider the following sequence of lost (denoted by x) | |||

and received (denoted by r) packets. | and received (denoted by r) packets. | |||

r r r x r r x x x r x r r x x x | r r r x r r x x x r x r r x x x | |||

skipping to change at page 6, line 54 | skipping to change at page 7, line 4 | |||

Example. Let delta = 99. Let us assume that packet 50 is lost | Example. Let delta = 99. Let us assume that packet 50 is lost | |||

followed by a bursty loss of length 3 starting from | followed by a bursty loss of length 3 starting from | |||

packet 125. | packet 125. | |||

All the *four* losses are noticeable. | All the *four* losses are noticeable. | |||

Given a Type-P-One-Way-Loss-Distance-Stream, this statistic | Given a Type-P-One-Way-Loss-Distance-Stream, this statistic | |||

can be computed simply as the number of losses that violate some | can be computed simply as the number of losses that violate some | |||

constraint delta, divided by the number of losses. (Alternately, it | constraint delta, divided by the number of losses. (Alternately, it | |||

can also be defined as the number of "noticeable losses" to the number | can also be defined as the number of "noticeable losses" to the number | |||

of successfully received packets). | ||||

This statistic is useful when the actual distance between successive | ||||

losses is important. For example, many multimedia codecs can sustain | ||||

losses by "concealing" the effect of loss by making use of past | of successfully received packets). This statistic is useful when the | |||

history information. Their ability to do so degrades with poor | actual distance between successive losses is important. For example, | |||

history resulting from losses separated by close distances. By chosing | many multimedia codecs can sustain losses by "concealing" the effect | |||

delta based on this sensitivity, one can measure how "noticeable" a | of loss by making use of past history information. Their ability to | |||

loss might be for quality purposes. The noticeable loss requires | do so degrades with poor history resulting from losses separated by | |||

a certain "spread factor" for losses in the timeseries. In the above | close distances. By chosing delta based on this sensitivity, one can | |||

example where loss constraint is equal to 99, a loss rate of one | measure how "noticeable" a loss might be for quality purposes. | |||

percent with a spread of 100 between losses (e.g., 100, 200, 300, | The noticeable loss requires a certain "spread factor" for losses | |||

400, 500 out of 500 packets) may be more desirable for some | in the timeseries. In the above example where loss constraint is equal | |||

applications compared to the same loss rate with a spread that | to 99, a loss rate of one percent with a spread of 100 between | |||

violates the loss constraint (e.g., 100, 175, 275, 290, 400: losses | losses (e.g., 100, 200, 300, 400, 500 out of 500 packets) may be more | |||

occuring at 175 and 290 violate delta = 99). | desirable for some applications compared to the same loss rate with a | |||

spread that violates the loss constraint | ||||

(e.g., 100, 175, 275, 290, 400: losses occuring at 175 and 290 | ||||

violate delta = 99). | ||||

5.2 Type-P-One-Way-Loss-Period-Total | 5.2 Type-P-One-Way-Loss-Period-Total | |||

This represents the total number of loss periods, and can be derived | This represents the total number of loss periods, and can be derived | |||

from the loss period metric Type-P-One-Way-Loss-Period-Stream as | from the loss period metric Type-P-One-Way-Loss-Period-Stream as | |||

follows: | follows: | |||

Type-P-One-Way-Loss-Period-Total = maximum value of the first entry | Type-P-One-Way-Loss-Period-Total = maximum value of the first entry | |||

of the set of pairs, <loss period, loss>, representing the loss metric | of the set of pairs, <loss period, loss>, representing the loss metric | |||

Type-P-One-Way-Loss-Period-Stream. | Type-P-One-Way-Loss-Period-Stream. | |||

Note that this statistic does not describe the duration of each loss | ||||

period itself. If this statistic is large, it does not mean that the | ||||

losses are more spread out than they are otherwise; one or more | ||||

loss periods may include bursty losses. This statistic is generally | ||||

useful in gathering first order of approximation of loss spread. | ||||

5.3 Type-P-One-Way-Loss-Period-Lengths | 5.3 Type-P-One-Way-Loss-Period-Lengths | |||

This statistic is a sequence of pairs <loss period, length>, with the | This statistic is a sequence of pairs <loss period, length>, with the | |||

"loss period" entry ranging from 1 - Type-P-One-Way-Loss-Period-Total. | "loss period" entry ranging from 1 - Type-P-One-Way-Loss-Period-Total. | |||

Thus the total number of pairs in this statistic equals | Thus the total number of pairs in this statistic equals | |||

Type-P-One-Way-Loss-Period-Total. In each pair, the "length" is | Type-P-One-Way-Loss-Period-Total. In each pair, the "length" is | |||

obtained by counting the number of pairs, <loss period, loss>, in the | obtained by counting the number of pairs, <loss period, loss>, in the | |||

metric Type-P-One-Way-Loss-Period-Stream which have first entry equal | metric Type-P-One-Way-Loss-Period-Stream which have first entry equal | |||

to "loss period." | to "loss period." | |||

Thus, this statistic represents the number of packets lost in each | Since this statistic represents the number of packets lost in each | |||

loss period. | loss period, it is an indicator of burstiness of each loss period. In | |||

conjunction with loss-period-total statistic, this statistic is generally | ||||

useful in observing which loss periods are potentially more influential | ||||

than others from a quality perspective. | ||||

5.4 Type-P-One-Way-Inter-Loss-Period-Lengths | 5.4 Type-P-One-Way-Inter-Loss-Period-Lengths | |||

This statistic measures distance between successive loss periods. It | This statistic measures distance between successive loss periods. It | |||

takes the form of a set of pairs | takes the form of a set of pairs | |||

<loss period, inter-loss-period-length>, with the | <loss period, inter-loss-period-length>, with the | |||

"loss period" entry ranging from 1 - Type-P-One-Way-Loss-Period-Total, | "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 | and "inter-loss-period-length" is the loss distance between the last | |||

packet considered lost in "loss period" 'i-1', and the first packet | packet considered lost in "loss period" 'i-1', and the first packet | |||

considered lost in "loss period" 'i', where 'i' ranges from 2 to | considered lost in "loss period" 'i', where 'i' ranges from 2 to | |||

Type-P-One-Way-Loss-Period-Total. The "inter-loss-period-length" | Type-P-One-Way-Loss-Period-Total. The "inter-loss-period-length" | |||

associated with the first "loss period" is defined to be zero. This | associated with the first "loss period" is defined to be zero. | |||

statistic allows one to consider, for example, two loss periods each | ||||

This statistic allows one to consider, for example, two loss periods each | ||||

of length greater than one (implying loss burst), but separated by a | 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 | distance of 2 to belong to the same loss burst if such a consideration | |||

is deemed useful. When the Inter-Loss-Period-Length between two bursty | ||||

is deemed useful. | loss periods is smaller, it could affect the loss concealing ability of | |||

multimedia codecs since there is relatively smaller history. When it is | ||||

larger, an application may be able to rebuild its history which could | ||||

dampen the effect of an impending loss (period). | ||||

5.5 Example | 5.5 Example | |||

We continue with the same example as in Section 4.4.3. The three | We continue with the same example as in Section 4.4.3. The three | |||

statistics defined above will have the following values. | statistics defined above will have the following values. | |||

+ Let delta = 2. | + Let delta = 2. | |||

In Type-P-One-Way-Loss-Distance-Stream | 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 | {<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, | are 3 loss distances that violate the delta of 2. Thus, | |||

skipping to change at page 9, line 17 | skipping to change at page 9, line 40 | |||

[Bolot] J.-C. Bolot and A. vega Garcia, "The case for FEC-based | [Bolot] J.-C. Bolot and A. vega Garcia, "The case for FEC-based | |||

error control for Packet Audio in the Internet", ACM Multimedia | error control for Packet Audio in the Internet", ACM Multimedia | |||

Systems, 1997. | Systems, 1997. | |||

[Borella] M. S. Borella, D. Swider, S. Uludag, and G. B. Brewster, | [Borella] M. S. Borella, D. Swider, S. Uludag, and G. B. Brewster, | |||

"Internet Packet Loss: Measurement and Implications for End-to-End | "Internet Packet Loss: Measurement and Implications for End-to-End | |||

QoS," Proceedings, International Conference on Parallel Processing, | QoS," Proceedings, International Conference on Parallel Processing, | |||

August 1998. | August 1998. | |||

[Handley] M. Handley, "An examination of MBONE performance", | [Handley] M. Handley, "An examination of MBONE performance", | |||

Technical Report, USC/ISI, ISI/RR-97-450, January 1997 | Technical Report, USC/ISI, ISI/RR-97-450, July 1997 | |||

[RK97] R. Koodli, "Scheduling Support for Multi-tier Quality of | [RK97] R. Koodli, "Scheduling Support for Multi-tier Quality of | |||

Service in Continuous Media Applications", PhD dissertation, | Service in Continuous Media Applications", PhD dissertation, | |||

Electrical and Computer Engineering Department, University of | Electrical and Computer Engineering Department, University of | |||

Massachusetts, Amherst, MA 01003. | Massachusetts, Amherst, MA 01003. | |||

[Padhye1] J. Padhye, V. Firoiu, J. Kurose and D. Towsley, "Modeling | [Padhye1] J. Padhye, V. Firoiu, J. Kurose and D. Towsley, "Modeling | |||

TCP throughput: a simple model and its empirical validation", in | TCP throughput: a simple model and its empirical validation", in | |||

Proceedings of SIGCOMM'98, 1998. | Proceedings of SIGCOMM'98, 1998. | |||

End of changes. | ||||

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