draft-ietf-ippm-loss-pattern-02.txt   draft-ietf-ippm-loss-pattern-03.txt 
Internet-Draft Internet-Draft
Expiration Date: April, 2000 R. Koodli Expiration Date: December, 2000 R. Koodli
R. Ravikanth R. Ravikanth
Nokia Research Center Nokia Research Center
October, 1999 July 2000
One-way Loss Pattern Sample Metrics One-way Loss Pattern Sample Metrics
<draft-ietf-ippm-loss-pattern-02.txt> <draft-ietf-ippm-loss-pattern-03.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.
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3.2. Loss Distance: 3.2. Loss Distance:
The difference in sequence numbers of two successively lost The difference in sequence numbers of two successively lost
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.
{Comment: 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. For example, assign consecutive integers to each packet in numbers. However, these sequence numbers must be consecutive
the time series.} integers.
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.
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one. The loss distance associated with the very first packet loss is one. The loss distance associated with the very first packet loss is
considered to be zero. considered to be zero.
The sequence number of a test packet can be derived from the timeseries The sequence number of a test packet can be derived from the timeseries
sample collected by performing the loss measurement according to the sample collected by performing the loss measurement according to the
methodology in [AKZ]. For example, if a loss sample consists of methodology in [AKZ]. For example, if a loss sample consists of
{<T0,0>, <T1,0>, <T2,1>, <T3,0>, <T4,0>}, the sequence numbers of the {<T0,0>, <T1,0>, <T2,1>, <T3,0>, <T4,0>}, the sequence numbers of the
five test packets sent at T0, T1, T2, T3, and T4 can be 0, 1, 2, 3 and 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. 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 4.4.2 Type-P-One-Way-Loss-Period-Stream
We start a counter 'n' at an initial value of zero. This counter is 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. incremented by one each time a lost packet satisfies the Definition 3.3.
The metric is defined as <loss period, loss> where The metric is defined as <loss period, loss> where
"loss" is derived from the sequence of <time, loss> in "loss" is derived from the sequence of <time, loss> in
Type-P-One-Way-Loss-Stream [AKZ], and Type-P-One-Way-Loss-Stream [AKZ], and
loss period is set to zero when "loss" is zero in loss period is set to zero when "loss" is zero in
Type-P-One-Way-Loss-Stream, and loss period is set to 'n' (above) Type-P-One-Way-Loss-Stream, and loss period is set to 'n' (above)
when "loss" is one in Type-P-One-Way-Loss-Stream. when "loss" is one in Type-P-One-Way-Loss-Stream.
{Note: When a packet is lost, the current value of "n" indicates the Essentially, when a packet is lost, the current value of "n" indicates
loss period to which this packet belongs. For a packet that is the loss period to which this packet belongs. For a packet that is
received successfully, the loss period is defined to be zero.} received successfully, the loss period is defined to be zero.
4.4.3 Example: 4.4.3 Example:
Let the following set of pairs represent a Type-P-One-Way-Loss-Stream. Let the following set of pairs represent a Type-P-One-Way-Loss-Stream.
{<T1,0>,<T2,1>,<T3,0>,<T4,0>,<T5,1>,<T6,0>,<T7,1>,<T8,0>,<T9,1>, {<T1,0>,<T2,1>,<T3,0>,<T4,0>,<T5,1>,<T6,0>,<T7,1>,<T8,0>,<T9,1>,
<T10,1>} <T10,1>}
where T1, T2,..,T10 are in increasing order. where T1, T2,..,T10 are in increasing order.
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4.5. Methodologies: 4.5. Methodologies:
The same methodology outlined in [AKZ] can be used to conduct the The same methodology outlined in [AKZ] can be used to conduct the
sample experiments. sample experiments.
4.6 Discussion: 4.6 Discussion:
The Loss-Distance-Stream metric allows one to study the separation The Loss-Distance-Stream metric allows one to study the separation
between packet losses. This could be useful in determining a between packet losses. This could be useful in determining a
"spread factor" associated with the packet loss rate. For "spread factor" associated with the packet loss rate. For
example, for a given packet loss rate, the proposed metric example, for a given packet loss rate, this metric
indicates how the losses are spread. On the other hand, indicates how the losses are spread. On the other hand,
the Loss-Period-Stream metric allows the study of loss burstiness the Loss-Period-Stream metric allows the study of loss burstiness
for each occurrence of loss. Note that a single loss period of for each occurrence of loss. Note that a single loss period of
length 'n' can account for a significant portion of the overall length 'n' can account for a significant portion of the overall
loss rate. Note also that it is possible to measure distance between loss rate. Note also that it is possible to measure distance between
loss bursts seprated by one or more successfully received packets: See loss bursts seprated by one or more successfully received packets: See
Section 5.4, and 5.5 Section 5.4, and 5.5
4.7 Sampling Considerations: 4.7 Sampling Considerations:
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5. Statistics: 5. Statistics:
5.1 Type-P-One-Way-Loss-Noticeable-Rate 5.1 Type-P-One-Way-Loss-Noticeable-Rate
Define loss of a packet to be "noticeable" [RK97] if the distance Define loss of a packet to be "noticeable" [RK97] if the distance
between the lost packet and the previously lost packet is no between the lost packet and the previously lost packet is no
greater than delta, a positive integer, where delta is the greater than delta, a positive integer, where delta is the
"loss constraint". "loss constraint".
Example. Let delta = 100. 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). 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
history information. Their ability to do so degrades with poor
history resulting from losses separated by close distances. By chosing
delta based on this sensitivity, one can measure how "noticeable" a
loss might be for quality purposes. The noticeable loss requires
a certain "spread factor" for losses in the timeseries. In the above
example where loss constraint is equal to 99, a loss rate of one
percent with a spread of 100 between losses (e.g., 100, 200, 300,
400, 500 out of 500 packets) may be more 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.
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."
{Note: This statistic represents the number of packets lost in each Thus, this statistic represents the number of packets lost in each
loss period.} loss period.
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
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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, January 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.
ftp://aurelius.ecs.umass.edu/pub/koodli/thesis.ps.Z
[Padhye1] J. Padhye, V. Firoiu, J. Kurose and D. Towsley, "Modeling [Padhye1] J. Padhye, V. Firoiu, J. Kurose and D. Towsley, "Modeling
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[Padhye2] J. Padhye, J. Kurose, D. Towsley and R. Koodli, "A [Padhye2] J. Padhye, J. Kurose, D. Towsley and R. Koodli, "A
TCP-friendly rate adjustment protocol for continuous media flows TCP-friendly rate adjustment protocol for continuous media flows
over best-effort networks", short paper presentation in over best-effort networks", short paper presentation in
ACM SIGMETRICS'99. Available as Umass Computer Science tech report ACM SIGMETRICS'99. Available as Umass Computer Science tech report
from ftp://gaia.cs.umass.edu/pub/Padhye98-tcp-friendly-TR.ps.gz from ftp://gaia.cs.umass.edu/pub/Padhye98-tcp-friendly-TR.ps.gz
skipping to change at page 9, line 40 skipping to change at line 451
833-846 833-846
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Author's Addresses Author's Addresses
Rajeev Koodli Rajeev Koodli
Nokia Research Center Nokia Research Center
3, Burlington Woods Drive, #250 313, Fairchild Drive
Burlington, MA 01803 Mountain View, CA 94043
Phone: +1 781-359-5136 Phone: +1 650-625-2359
Email: rajeev.koodli@nokia.com Email: rajeev.koodli@nokia.com
Rayadurgam Ravikanth Rayadurgam Ravikanth
Nokia Research Center Nokia Research Center
3, Burlington Woods Drive, #250 5, Wayside Road
Burlington, MA 01803 Burlington, MA 01803
Phone: +1 781-238-4905 Phone: +1 781-993-4606
Email: rayadurgam.ravikanth@nokia.com Email: rayadurgam.ravikanth@nokia.com
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