draft-ietf-bmwg-atm-term-abr-00.txt   draft-ietf-bmwg-atm-term-abr-01.txt 
Network Working Group J. H. Dunn Network Working Group J. H. Dunn
INTERNET-DRAFT C. E. Martin INTERNET-DRAFT C. E. Martin
Expires: May, 2000 ANC, Inc. Expires: September, 2000 ANC, Inc.
November, 1999 March, 2000
Terminology for ATM ABR Benchmarking Terminology for ATM ABR Benchmarking
<draft-ietf-bmwg-atm-term-abr-00.txt> <draft-ietf-bmwg-atm-term-abr-01.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
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, and documents of the Internet Engineering Task Force (IETF), its areas, and
its working groups. Note that other groups may also distribute working its working groups. Note that other groups may also distribute working
documents as Internet-Drafts. documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as work in progress. or to cite them other than as work in progress.
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved. Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract Abstract
This memo discusses and defines terms associated with performance This memo discusses and defines terms associated with performance
benchmarking tests and the results of these tests in the context of benchmarking tests and the results of these tests in the context of
Asynchronous Transfer Mode (ATM) based switching devices supporting ABR. Asynchronous Transfer Mode (ATM) based switching devices supporting ABR.
The terms defined in this memo will be used in addition to terms defined The terms defined in this memo will be used in addition to terms defined
in RFCs 1242, 2285, and 2544 and in ID Terminology for ATM Benchmarking. in RFCs 1242, 2285, and 2544 and 2761. This memo is a product of the
This memo is a product of the Benchmarking Methodology Working Group Benchmarking Methodology Working Group (BMWG) of the Internet
(BMWG) of the Internet Engineering Task Force (IETF). Engineering Task Force (IETF).
1. Introduction. 1. Introduction.
This document provides terminology for benchmarking ATM based switching This document provides terminology for benchmarking ATM based switching
devices supporting ABR. It extends terminology already defined for devices supporting ABR. It extends terminology already defined for
benchmarking network interconnect devices in RFC's 1242, 2285, and 2544 benchmarking network interconnect devices in RFC's 1242, 2285, and 2544
and in ID Terminology for ATM Benchmarking. Although some of the and 2761. Although some of the definitions in this memo may be
definitions in this memo may be applicable to a broader group of network applicable to a broader group of network interconnect devices, the
interconnect devices, the primary focus of the terminology in this memo primary focus of the terminology in this memo is on ATM ABR.
is on ATM ABR.
This memo contains two major sections: Background and Definitions. The This memo contains two major sections: Background and Definitions. The
background section provides the reader with an overview of the background section provides the reader with an overview of the
technology and IETF formalisms. The definitions section is split into technology and IETF formalisms. The definitions section is split into
two sub- sections. The formal definitions sub-section is provided as a two sub- sections. The formal definitions sub-section is provided as a
courtesy to the reader. The measurement definitions sub-section courtesy to the reader. The measurement definitions sub-section
contains performance metrics with inherent units. contains performance metrics with inherent units.
This document assumes that necessary services are available and active. This document assumes that necessary services are available and active.
For example, IP connectivity requires SSCOP connectivity between For example, IP connectivity requires SSCOP connectivity between
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benchmarks cited in the corresponding Terminology documents. benchmarks cited in the corresponding Terminology documents.
2. Existing Definitions. 2. Existing Definitions.
RFC 1242 "Benchmarking Terminology for Network Interconnect Devices" RFC 1242 "Benchmarking Terminology for Network Interconnect Devices"
should be consulted before attempting to make use of this document. RFC should be consulted before attempting to make use of this document. RFC
2544 "Benchmarking Methodology for Network Interconnect Devices" 2544 "Benchmarking Methodology for Network Interconnect Devices"
contains discussions of a number of terms relevant to the benchmarking contains discussions of a number of terms relevant to the benchmarking
of switching devices and should be consulted. RFC 2285 "Benchmarking of switching devices and should be consulted. RFC 2285 "Benchmarking
Terminology for LAN Switching Devices" contains a number of terms Terminology for LAN Switching Devices" contains a number of terms
pertaining to traffic distributions and datagram interarrival. For the pertaining to traffic distributions and datagram interarrival. RFC 2761
sake of clarity and continuity, this RFC adopts the template for " Terminology for ATM Benchmarking" contains a number terms pertaining
definitions set out in Section 2 of RFC 1242. to traffic management [TM4.0, TM4.1]. Many of the metrics defined in
RFC 2761 (e.g. CDV, CER, CLR, CMR, and CTD) also apply to ABR
performance benchmarking. These metrics will not be redefined in this
document. For the sake of clarity and continuity, this RFC adopts the
template for definitions set out in Section 2 of RFC 1242.
3. Requirements 3. Requirements
In this document, the words that are used to define the significance of In this document, the words that are used to define the significance of
each particular requirement are capitalized. These words are: each particular requirement are capitalized. These words are:
* "MUST" This word, or the words "REQUIRED" and "SHALL" mean that the * "MUST" This word, or the words "REQUIRED" and "SHALL" mean that the
item is an absolute requirement of the specification. item is an absolute requirement of the specification.
* "SHOULD" This word or the adjective "RECOMMENDED" means that there may * "SHOULD" This word or the adjective "RECOMMENDED" means that there may
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specified and are listed in the references section. specified and are listed in the references section.
1.2. Related Definitions. 1.2. Related Definitions.
1.2.1. Allowed Cell Rate (ACR) 1.2.1. Allowed Cell Rate (ACR)
Definition: An ABR service parameter, ACR is the current rate Definition: An ABR service parameter, ACR is the current rate
(cells/second) at which a source is allowed to send. (cells/second) at which a source is allowed to send.
Discussion: For ABR traffic, ACR constitutes the actual data throughput Discussion: For ABR traffic, ACR constitutes the actual data throughput
for a particular VC. The time change of this value effects TCP round for a particular VC. The time change of this value effects TCP round trip
trip time calculations, which in turn effects TCP throughput. time calculations, which in turn effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.2. ACR Decrease Time Factor (ADTF) 1.2.2. ACR Decrease Time Factor (ADTF)
Definition: This is the time permitted between sending RM-cells before Definition: This is the time permitted between sending RM-cells before the
the rate is decreased to ICR (Initial Cell Rate). The time units are rate is decreased to ICR (Initial Cell Rate). The time units are
.01 to 10.23 seconds .01 to 10.23 seconds
with a granularity of 10 ms. with a granularity of 10 ms.
Discussion: For ABR traffic, ADTF constitutes the time rate of the ACR. Discussion: For ABR traffic, ADTF constitutes the time rate of the ACR.
This value effects TCP round trip time calculations, which in turn This value effects TCP round trip time calculations, which in turn effects
effects TCP throughput. TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.3. Additive Increase Rate (AIR) 1.2.3. Additive Increase Rate (AIR)
Definition: An ABR service parameter, AIR controls the rate at which the Definition: An ABR service parameter, AIR controls the rate at which the
cell transmission rate increases. It is signaled as AIRF, where cell transmission rate increases. It is signaled as AIRF, where
AIRF = AIR*Nrm/PCR. AIRF = AIR*Nrm/PCR.
Discussion: For ABR traffic, AIR effects the time rate of change of the Discussion: For ABR traffic, AIR effects the time rate of change of the
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1.2.4. Additive Increase Rate Factor (AIRF) 1.2.4. Additive Increase Rate Factor (AIRF)
Definition: Refer to AIR. Definition: Refer to AIR.
Discussion: Refer to AIR. Discussion: Refer to AIR.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.5. Available Bit Rate (ABR) 1.2.5. Available Bit Rate (ABR)
Definition: ABR is an ATM layer service category for which the limiting Definition: ABR is an ATM layer service category for which the limiting ATM
ATM layer transfer characteristics provided by the network may change layer transfer characteristics provided by the network may change
subsequent to connection establishment. A flow control mechanism is subsequent to connection establishment. A flow control mechanism is
specified which supports several types of feedback to control the source specified which supports several types of feedback to control the source
rate in response to changing ATM layer transfer characteristics. rate in response to changing ATM layer transfer characteristics.
Discussion: It is expected that an end-system that adapts its traffic in Discussion: It is expected that an end-system that adapts its traffic in
accordance with the feedback will experience a low cell loss ratio and accordance with the feedback will experience a low cell loss ratio and
obtain a fair share of the available bandwidth according to a network obtain a fair share of the available bandwidth according to a network
specific allocation policy. Cell delay variation is not controlled in specific allocation policy. Cell delay variation is not controlled in this
this service, although admitted cells are not delayed unnecessarily. service, although admitted cells are not delayed unnecessarily.
Specification: AF-TM4.0 Specification: AF-TM4.1
1.2.6. Cutoff Decrease Factor (CDF) 1.2.6. Available Bit Rate (ABR) Compliance (Conformance)
Definition: CDF controls the decrease in ACR (Allowed Cell Rate) Definition: ABR connection conformance refers to the behavior specified for
associated with CRM (missing RM cell count). ABR destination and switches, but allows for delays between the source and
the UNI [UNI3.1, UNI4.0], which may perturb the traffic flow.
Discussion: The cells on an ABR connection applies to CLP=0 cells, which
are tested upon arrival. At the arrival point, each cell is identified as
conforming or non-conforming. The minimal conformance definition for ABR
is GCRA((1/PCR),t1), where PCR is defined for CLP=0 flow.
Specification: AF-TM4.1
1.2.7. BN
Definition: The BN bit in the RM-cell indicated wheather the RM-cell is a
BECN cell or not.
Discussion: If BN=0, the RM cells were generated by the source. If BN=1,
the RM cells were generated by the destination or a switch.
Specification: AF-TM4.1
1.2.8. CCR
Definition: The CCR field in the RM-cell is set by the source to its
current ACR. CCR is formatted as a rate.
Discussion: For BECN cells, CCR=0.
Specification: AF-TM4.1
1.2.9. Cell Blocks (CB)
Definition: Cell blocks are a sequence of N cells transmitted consecutively
on a given connection.
Discussion: A cell block will normally correspond to the number of
information cells transmitted between successive OAM cells.
Specification: AF-TM4.1
1.2.10. Congestion Indication (CI)
Definition: The CI bit in the RM-cell allows a network element to indicate
that there is congestion in the network.
Discussion: When the source receives a backward RM-cell with CI=1, ACR is
decreased. When the destination turns around a forward RM-cell, the CI is
set to 1 to indicate that the previously received data cell had the EFCI
state set.
Specification: AF-TM4.1
1.2.11. Cutoff Decrease Factor (CDF)
Definition: CDF controls the decrease in ACR (Allowed Cell Rate) associated
with CRM (missing RM cell count).
Discussion: For ABR traffic, CDF effects the time rate of change of the Discussion: For ABR traffic, CDF effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.7. Initial Cell Rate (ICR) 1.2.12. DIR
Definition: The DIR bit in the RM-cell indicates which direction of data
flow is associated with the RM-cell. DIR is changed from 0 to 1 when an
RM-cell is turned around at the destination.
Discussion: A forward RM-cell is indicated by DIR=0 and is associated with
data cells flowing in the same direction. A backward RM-cell is indicated
by DIR=1 and is associated with data cells flowing in the opposite
direction.
Specification: AF-TM4.1
1.2.13. Explicit Rate (ER)
Definition: The ER field in the RM-cell is used to limit the source ACR to
a specific value. For each RM-cell, ER is set by the source to a requested
rate (e.g. PCR). It may be reduced by any network element in the path to a
value that the element can sustain. ER is formatted as a rate.
Discussion: None.
Specification: AF-TM4.1
1.2.14. Feedback
Definition: Information carried in the backward RM-cells provided by the
network elements and/or the destination back to the source.
Discussion: Feedback may include information in the ER field, or the CI or
NI bits of each backward RM-cell.
Specification: AF-TM4.1
1.2.15. Ideal Transmission Time (ITT)
Definition: The transmission time for ABR CLP=0 cells, if the difference
between itself and the transmission time for the previous CLP=0 cell on the
connection is greater than or equal to the minimum: a) the inverse of the
ACR in effect immediately after the transmission time of the first of the
two cells b) the inverse of the ACR in effect immediately before the
transmission time of the second of the two cells.
Discussion: The transmission time for the first cell on the connection is
automatically an ITT.
Specification: AF-TM4.1
1.2.16. Initial Cell Rate (ICR)
Definition: An ABR service parameter, in cells/sec, that is the rate at Definition: An ABR service parameter, in cells/sec, that is the rate at
which a source should send initially and after an idle period. which a source should send initially and after an idle period.
Discussion: none. Discussion: none.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.8. Minimum Cell Rate (MCR) 1.2.17. In-Rate Cells
Definition: In-Rate ABR cells are sent with CLP=0.
Discussion: ABR RM-cells shall be sent with CLP=0 except in certain
circumstances, See Out-of-Rate Cells. All other ABR cells shall be sent
with CLP=0.
Specification: AF-TM4.1
1.2.18. Minimum Cell Rate (MCR)
Definition: An ABR service traffic descriptor, in cells/sec, that is the Definition: An ABR service traffic descriptor, in cells/sec, that is the
rate at which the source is always allowed to send. rate at which the source is always allowed to send.
Discussion: MCR may be set to zero. The bandwidth available from the
network may vary, but shall not become less than MCR.
Specification: AF-TM4.1
1.2.19. Mrm
Definition: An ABR service parameter that controls allocation of bandwidth
between forward W-cells, backward RM-cells, and data cells.
Discussion: none. Discussion: none.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.9. Mrm 1.2.20. No Increase (NI)
Definition: An ABR service parameter that controls allocation of Definition: The NI bit in the RM-cell is used to prevent a source from
bandwidth between forward W-cells, backward RM-cells, and data cells. increasing its ACR. NI does not require any decrease in value.
Discussion: none. Discussion: None.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.10. Nrm 1.2.21. Nrm
Definition: An ABR service parameter, Nrm is the maximum number of cells Definition: An ABR service parameter, Nrm is the maximum number of cells a
a source may send for each forward RM-cell. source may send for each forward RM-cell.
Discussion: none. Discussion: none.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.11. Rate Decrease Factor (RDF) 1.2.22. Out-of-Rate Cells
Definition: An ABR service parameter, RDF controls the decrease in the Definition: Out-of-Rate ABR cells are sent with CLP=1.
cell transmission rate. RDF is a power of 2 from 1/32,768 to 1.
Discussion: This may be used to enable a rate increate for a connection
that has an ACR=0. The source would generate out-of-rate cells to probe
the network to learn when it may increase its rate.
Specification: AF-TM4.1
1.2.23. Rate Decrease Factor (RDF)
Definition: An ABR service parameter, RDF controls the decrease in the cell
transmission rate. RDF is a power of 2 from 1/32,768 to 1.
Discussion: For ABR traffic, RDF effects the time rate of change of the Discussion: For ABR traffic, RDF effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.12. Rate Increase Factor (RIF) 1.2.24. Rate Increase Factor (RIF)
Definition: This controls the amount by which the cell transmission rate Definition: This controls the amount by which the cell transmission rate
may increase upon receipt of a RM-cell. The additive increase rate may increase upon receipt of a RM-cell. The additive increase rate
AIR=PCR*RIF. RIF is a power of 2, ranging from 1/32,768 to 1. AIR=PCR*RIF. RIF is a power of 2, ranging from 1/32,768 to 1.
Discussion: For ABR traffic, RIF effects the time rate of change of the Discussion: For ABR traffic, RIF effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.13. Resource Management (RM) Cells 1.2.25. Resource Management (RM) Cells
Definition: RM cells are used to convey network status (available Definition: RM cells are used to convey network status (available
bandwidth, congestion levels) and request peak cell rates for ATM bandwidth, congestion levels) and request peak cell rates for ATM blocks.
blocks. The RM cell has the following format: The RM cell has the following format:
Header: 5 bytes, same as the ATM cell header Header: 5 bytes, same as the ATM cell header
Protocol ID: 3 bytes, value is ID1 Protocol ID: 3 bytes, protocol ID value is 1 for ABR service
Function specific field: 45 bytes, data required for the specific protocol Function specific field: 45 bytes, data required for the specific protocol
(See DIR, BN, CI, NI, ER, CCR, and MCR for field information.)
Rsvd: 6 bytes, reserved for future specification Rsvd: 6 bytes, reserved for future specification
EDC: 10 bytes, CRC-10 error detection code computed over the cell payload EDC: 10 bytes, CRC-10 error detection code computed over the cell payload
(except the CRC-10 field) and used to check for data corruption (except the CRC-10 field) and used to check for data corruption
Discussion: RM information can exist at the VP and/or VC level. VP level Discussion: RM information can exist at the VP and/or VC level. VP level
cells are identified with a VCI value of 6. VC level cells are cells are identified with a VCI value of 6. VC level cells are identified
identified with a PT of 6. with a PT of 6. See DIR, BN, CI, NI, ER, CCR, and MCR for additional
protocol field information.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.14. Tagged Cell Rate (TCR) 1.2.26. Severely Errored Cell Block (SECB)
Definition: An ABR service parameter, TCR limits the rate at which a Definition: A severely cell block outcome occurs when more than M errored
source may send out-of-rate forward RM-cells. TCR is a constant fixed at
10 cells/second. cells, lost cells, or misinserted cell outcomes are observed in a received
cell block.
Discussion: none.
Specification: AF-TM4.1
1.2.27. Tagged Cell Rate (TCR)
Definition: An ABR service parameter, TCR limits the rate at which a source
may send out-of-rate forward RM-cells. TCR is a constant fixed at 10
cells/second.
Discussion: none. Discussion: none.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.15. TDF 1.2.28. TDF
Definition: An ABR service parameter, TDF controls the decrease in ACR Definition: An ABR service parameter, TDF controls the decrease in ACR
associated with TOF. TDF is signaled as TDFF, where TDF=TDFF/RDF times associated with TOF. TDF is signaled as TDFF, where TDF=TDFF/RDF times the
the smallest power of 2 greater or equal to PCR. TDF is in units of smallest power of 2 greater or equal to PCR. TDF is in units of 1/seconds.
1/seconds.
Discussion: For ABR traffic, TDF effects the time rate of change of the Discussion: For ABR traffic, TDF effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.16. TDFF 1.2.29. TDFF
Definition: Refer to TDF. TDFF is either zero or a power of two in the Definition: Refer to TDF. TDFF is either zero or a power of two in the
range 1/64 to 1 in units of 1 /cells. range 1/64 to 1 in units of 1 /cells.
Discussion: Refer to TDF. Discussion: Refer to TDF.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.17. Time Out Factor (TOF) 1.2.30. Time Out Factor (TOF)
Definition: An ABR service parameter, TOF controls the maximum time Definition: An ABR service parameter, TOF controls the maximum time
permitted between sending forward RM-cells before a rate decrease is permitted between sending forward RM-cells before a rate decrease is
required. It is signaled as TOFF where TOF=TOFF+1. TOFF is a power of 2
in the range: 1/8 to 4,096. required. It is signaled as TOFF where TOF=TOFF+1. TOFF is a power of 2 in
the range: 1/8 to 4,096.
Discussion: For ABR traffic, TOF effects the time rate of change of the Discussion: For ABR traffic, TOF effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.18. Time Out Factor (TOFF) 1.2.31. Time Out Factor (TOFF)
Definition: Refer to TOF. Definition: Refer to TOF.
Discussion: none. Discussion: none.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.19. Trm
1.2.32. Trm
Definition: An ABR service parameter that provides an upper bound on the Definition: An ABR service parameter that provides an upper bound on the
time between forward RM-cells for an active source. It is 100 times a time between forward RM-cells for an active source. It is 100 times a power
power of two with a range of 100*2-7 to 100*20 of two with a range of 100*2-7 to 100*20
Discussion: For ABR traffic, Trm effects the time rate of change of the Discussion: For ABR traffic, Trm effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.20. Virtual Source/Virtual Destination (VSND) 1.2.33. Virtual Source/Virtual Destination (VSND)
Definition: An ABR connection may be divided into two or more separately Definition: An ABR connection may be divided into two or more separately
controlled ABR segments. Each ABR control segment, except the first, is controlled ABR segments. Each ABR control segment, except the first, is
sourced by a virtual source. A virtual source implements the behavior of sourced by a virtual source. A virtual source implements the behavior of an
an ABR source endpoint. Backward RM-cells received by a virtual source ABR source endpoint. Backward RM-cells received by a virtual source are
are removed from the connection. Each ABR control segment, except the removed from the connection. Each ABR control segment, except the last, is
last, is terminated by a virtual destination. A virtual destination terminated by a virtual destination. A virtual destination assumes the
assumes the behavior of an ABR destination endpoint. Forward RM-cells behavior of an ABR destination endpoint. Forward RM-cells received by a
received by a virtual destination are turned around and not forwarded to virtual destination are turned around and not forwarded to the next segment
the next segment of the connection. of the connection.
Discussion: none. Discussion: none.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.21. Xrm Decrease Factor (XDM) 1.2.34. Xrm Decrease Factor (XDM)
Definition: An ABR service parameter, XDF controls the decrease in ACR Definition: An ABR service parameter, XDF controls the decrease in ACR
associated with Xrm. It is a power of two in range: [0, 1]. associated with Xrm. It is a power of two in range: [0, 1].
Discussion: For ABR traffic, XDM effects the time rate of change of the Discussion: For ABR traffic, XDM effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.22. Xrm 1.2.35. Xrm
Definition: An ABR service parameter, Xrm limits the number of forward Definition: An ABR service parameter, Xrm limits the number of forward RM-
RM- cells which may be sent in the absence of received backward PM- cells which may be sent in the absence of received backward PM-cells. The
cells. The range is 0-255. range is 0-255.
Discussion: For ABR traffic, Xrm effects the time rate of change of the Discussion: For ABR traffic, Xrm effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput. effects TCP throughput.
Specification: AF-TM4.0 Specification: AF-TM4.0
2. Performance Metrics 2. Performance Metrics
2. 1. Definition Format (from RFC 1242) 2. 1. Definition Format (from RFC 1242)
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includes subsidiary units; e.g., microseconds are acceptable if the includes subsidiary units; e.g., microseconds are acceptable if the
intrinsic unit is seconds. intrinsic unit is seconds.
2.2. Definitions 2.2. Definitions
2.2.1. ABR Rate Decrease Response Time (ARDRT) 2.2.1. ABR Rate Decrease Response Time (ARDRT)
Definition: The amount of time required by the SUT to adjust its Definition: The amount of time required by the SUT to adjust its
transmission rate based on an ABR rate decrease request. transmission rate based on an ABR rate decrease request.
Discussion: During the ARDRT, cells transmitted by the SUT may be Discussion: During the ARDRT, cells transmitted by the SUT may be dropped
dropped by the network due to traffic policing. These dropped cells may by the network due to traffic policing. These dropped cells may contain a
contain a portion of an IP datagram. This may cause IP and TCP packet portion of an IP datagram. This may cause IP and TCP packet loss.
loss.
Measurement Units: seconds Measurement Units: seconds
2.2.2. ABR Rate Increase Response Time (ARIRT) 2.2.2. ABR Rate Increase Response Time (ARIRT)
Definition: The amount of time required by the SUT to adjust its Definition: The amount of time required by the SUT to adjust its
transmission rate based on an ABR rate increase request. transmission rate based on an ABR rate increase request.
Discussion: During the ARIRT, the SUT will not fully utilize the Discussion: During the ARIRT, the SUT will not fully utilize the available
available bandwidth. This will negatively impact IP and TCP throughput. bandwidth. This will negatively impact IP and TCP throughput.
Measurement Units: seconds Measurement Units: seconds
2.2.3. RM Cell Loss Ratio (RM-CLR) 2.2.3. RM-Cell Delay Variation (RM-CDV)
Definition: The ratio of lost RM cells in a transmission in relation to Definition: The variation in RM-cell transfer delay (RM-CTD) of RM-cells
the total RM cells sent in a transmission associated with a given associated with a given traffic load, orientation and distribution, as well
traffic load, orientation and distribution, as well as an integration as an integration period. RM-CDV = max (RM-CTD) - min (RM-CTD) where max
and min indicate the maximum and minimum over the integration period,
respectively.
Discussion: RM-CDV is a component of RM-cell transfer delay, induced by
buffering and RM-cell scheduling.
RM-CDV effects the time required to notify the source of a change in the
condition of the network. This in turn effects TCP round trip time
calculations. Large values of RM-CDV will adversely effect TCP throughput
and cause SAR timeout.
Measurement Units: seconds
2.2.4. RM-Cell Error Ratio (RM-CER)
Definition: The ratio of RM-cells with payload errors in a transmission in
relation to the total number of RM-cells sent in a transmission associated
with a given traffic load, orientation and distribution, as well as an
integration period. Note that errors occurring in the RM-cell header will
cause RM-cell loss at the ATM layer. Note further that multiple errors in
a payload will only be counted as one cell payload error.
RM-CER = RM-Cells with payload errors / Total RM-Cells Transmitted.
Discussion: The measurement is taken over a time interval and is desirable
to be measured on an in-service circuit. RM-CER effects the time required
to notify the source of a change in the condition of the network. This in
turn effects TCP round trip time calculations. Large values of RM-CER will
adversely effect TCP throughput and cause SAR timeout.
Measurement Units: dimensionless.
2.2.5. RM-Cell Loss Ratio (RM-CLR)
Definition: The ratio of lost RM-cells in a transmission in relation to the
total RM-cells sent in a transmission associated with a given traffic load,
orientation and distribution, as well as an integration period.
RM-CLR = Lost RM-Cells / Total RM-Cells Transmitted.
Discussion: The objective is to minimize RM-CLR. It is expressed as an
order of magnitude, having a range of 10^-1 to 10^-15 and unspecified.
RM-CLR effects the time required to notify the source of a change in the
condition of the network. This in turn effects TCP round trip time
calculations. Large values of RM-CLR will adversely effect TCP throughput
and cause SAR timeout.
Measurement Units: dimensionless.
2.2.6. RM-Cell Misinsertion Ratio (RM-CMR)
Definition: The ratio of RM-cells received at an endpoint that were not
originally transmitted by the source end in relation to the total number of
RM-cells properly transmitted associated with a given traffic load,
orientation and distribution, as well as an integration period.
RM-CMR = Misinserted RM-Cells / Total RM-Cells Transmitted.
Discussion: The measurement is taken over a time interval and is desirable
to be measured on an in-service circuit.
RM-CMR effects the time required to notify the source of a change in the
condition of the network. This in turn effects TCP round trip time
calculations. Large values of RM-CMR will adversely effect TCP throughput
and cause SAR timeout.
Measurement Units: dimensionless.
2.2.7. RM-CRC Error Ratio
Definition: The ratio of RM-cells received at an endpoint which contain an
invalid CRC in relation to the total number of RM-cells properly
transmitted associated with a given traffic load, orientation and
distribution, as well as an integration period.
Discussion: RM-CRC errors cause ATM RM-cells to be lost.
RM-CRC effects the time required to notify the source of a change in the
condition of the network. This in turn effects TCP round trip time
calculations. Large values of RM-CRC will adversely effect TCP throughput
and cause SAR timeout.
Measurement Units: dimensionless
2.2.8. RM-Cell Transfer Delay (RM-CTD)
Definition: The elapsed time between a RM-cell exit event at the
measurement point 1 (e.g., at the source UNI) and the corresponding RM-
cell entry event at a measurement point 2 (e.g., the destination UNI) for a
particular connection.
Discussion: The RM-cell transfer delay between two measurement points is
the sum of the total inter-ATM node transmission delay and the total ATM
node processing delay. This number is a constant and should not adversely
effect performance.
Measurement units: seconds
2.2.9. Severely Errored Cell Block Ratio (SECBR)
Definition: The ratio of severely errored cell blocks in a transmission in
relation to the total cell blocks sent in a transmission associated with a
given traffic load, orientation and distribution, as well as an integration
period. period.
RM-CLR = Lost RM Cells / Total RM Cells Transmitted. SECBR = Severely Errored Cell Blocks/Total Transmitted Cell Blocks
Discussion: RM-CLR may cause the SUT to transmit data cells at a rate Discussion: SECBR may cause the SUT to drop cells that may contain a
larger than the available bandwidth. These data cells may be dropped by
the network due to traffic policing. These dropped cells may contain a
portion of an IP datagram. This may cause IP and TCP packet loss. portion of an IP datagram. This may cause IP and TCP packet loss.
It is expressed as an order of magnitude, having a range of 10^-1 to
10^- 15 and unspecified.
Measurement Units: dimensionless. Measurement Units: dimensionless.
3. Security Considerations. 3. Security Considerations.
As this document is solely for providing terminology and describes As this document is solely for providing terminology and describes
neither a protocol nor an implementation, there are no security neither a protocol nor an implementation, there are no security
considerations associated with this document. considerations associated with this document.
4. Notices 4. Notices
skipping to change at page 11, line 25 skipping to change at page 18, line 33
revoked by the Internet Society or its successors or assigns. This revoked by the Internet Society or its successors or assigns. This
document and the information contained herein is provided on an "AS IS" document and the information contained herein is provided on an "AS IS"
basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE
DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE 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 ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. PARTICULAR PURPOSE.
6. References 6. References
[AF-ILMI4.0] ATM Forum Integrated Local Management Interface Version
4.0, af-ilmi-0065.000, September 1996.
[AF-TEST-0022] Introduction to ATM Forum Test Specifications, af-test-
0022.00, December 1994.
[AF-TM4.0] ATM Forum, Traffic Management Specification Version 4.0, af- [AF-TM4.0] ATM Forum, Traffic Management Specification Version 4.0, af-
tm- 0056.00, April 1996. tm- 0056.00, April 1996.
[AF-TM4.1] ATM Forum, Traffic Management Specification Version 4.1 [AF-TM4.1] ATM Forum, Traffic Management Specification Version 4.1, af-
(final ballot), btd-tm-01.02, July 1998. tm- 0121.000, March 1999.
[AF-UNI3.1] ATM Forum, User Network Interface Specification Version 3.1, [AF-UNI3.1] ATM Forum, User Network Interface Specification Version 3.1,
September 1994. September 1994.
[AF-UNI4.0] ATM Forum, User Network Interface Specification Version 4.0, [AF-UNI4.0] ATM Forum, User Network Interface Specification Version 4.0,
July 1996. July 1996.
7. Editors Addresses 7. Editors Addresses
Jeffrey Dunn Jeffrey Dunn
Advanced Network Consultants, Inc. Advanced Network Consultants, Inc.
4214 Crest Place, Ellicott City, MD 21043 USA 4214 Crest Place, Ellicott City, MD 21043 USA
Phone: +1 (410) 750-1700, E-mail: Jeffrey.Dunn@worldnet.att.net Phone: +1 (410) 750-1700, E-mail: Jeffrey.Dunn@worldnet.att.net
Cynthia Martin Cynthia Martin
Advanced Network Consultants, Inc. Advanced Network Consultants, Inc.
4214 Crest Place, Ellicott City, MD 21043 USA 4214 Crest Place, Ellicott City, MD 21043 USA
Phone: +1 (410) 750-1700, E-mail: Cynthia.E.Martin@worldnet.att.net Phone: +1 (410) 750-1700, E-mail: Cynthia.E.Martin@worldnet.att.net
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