Network Working Group J. H. Dunn
INTERNET-DRAFT C. E. Martin
Expires: May, 2000 ANC, Inc.
November, 1999
Terminology for ATM ABR Benchmarking
<draft-ietf-bmwg-atm-term-abr-00.txt>
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
This memo discusses and defines terms associated with performance
benchmarking tests and the results of these tests in the context of
Asynchronous Transfer Mode (ATM) based switching devices supporting ABR.
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.
This memo is a product of the Benchmarking Methodology Working Group
(BMWG) of the Internet Engineering Task Force (IETF).
1. Introduction.
This document provides terminology for benchmarking ATM based switching
devices supporting ABR. It extends terminology already defined for
benchmarking network interconnect devices in RFC's 1242, 2285, and 2544
and in ID Terminology for ATM Benchmarking. Although some of the
definitions in this memo may be applicable to a broader group of network
interconnect devices, the primary focus of the terminology in this memo
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is on ATM ABR.
This memo contains two major sections: Background and Definitions. The
background section provides the reader with an overview of the
technology and IETF formalisms. The definitions section is split into
two sub- sections. The formal definitions sub-section is provided as a
courtesy to the reader. The measurement definitions sub-section
contains performance metrics with inherent units.
This document assumes that necessary services are available and active.
For example, IP connectivity requires SSCOP connectivity between
signaling entities. Further, it is assumed that the SUT has the ability
to configure ATM addresses (via hard coded addresses, ILMI or PNNI
neighbor discovery), has the ability to run SSCOP, and has the ability
to perform signaled call setups (via UNI or PNNI signaling). Finally,
this document presents only the terminology associated with benchmarking
IP performance over ATM; therefore, it does not represent a total
compilation of ATM test terminology.
The BMWG produces two major classes of documents: Benchmarking
Terminology documents and Benchmarking Methodology documents. The
Terminology documents present the benchmarks and other related terms.
The Methodology documents define the procedures required to collect the
benchmarks cited in the corresponding Terminology documents.
2. Existing Definitions.
RFC 1242 "Benchmarking Terminology for Network Interconnect Devices"
should be consulted before attempting to make use of this document. RFC
2544 "Benchmarking Methodology for Network Interconnect Devices"
contains discussions of a number of terms relevant to the benchmarking
of switching devices and should be consulted. RFC 2285 "Benchmarking
Terminology for LAN Switching Devices" contains a number of terms
pertaining to traffic distributions and datagram interarrival. For the
sake of clarity and continuity, this RFC adopts the template for
definitions set out in Section 2 of RFC 1242.
3. Requirements
In this document, the words that are used to define the significance of
each particular requirement are capitalized. These words are:
* "MUST" This word, or the words "REQUIRED" and "SHALL" mean that the
item is an absolute requirement of the specification.
* "SHOULD" This word or the adjective "RECOMMENDED" means that there may
exist valid reasons in particular circumstances to ignore this item, but
the full implications should be understood and the case carefully
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weighed before choosing a different course.
* "MAY" This word or the adjective "OPTIONAL" means that this item is
truly optional. One vendor may choose to include the item because a
particular marketplace requires it or because it enhances the product,
for example; another vendor may omit the same item.
An implementation is not compliant if it fails to satisfy one or more of
the MUST requirements for the protocols it implements. An
implementation that satisfies all the MUST and all the SHOULD
requirements for its protocols is said to be "unconditionally
compliant"; one that satisfies all the MUST requirements but not all the
SHOULD requirements for its protocols is said to be "conditionally
compliant".
II. Definitions
The definitions presented in this section have been divided into two
groups. The first group is formal definitions, which are required in
the definitions of the performance metrics but are not themselves
strictly metrics. These definitions are subsumed from other work done
in other working groups both inside and outside the IETF. They are
provided as a courtesy to the reader.
1. Formal Definitions
1.1. Definition Format (from RFC 1242)
Term to be defined.
Definition: The specific definition for the term.
Discussion: A brief discussion of the term, its application and any
restrictions on measurement procedures.
Specification: The working group and document in which the terms are
specified and are listed in the references section.
1.2. Related Definitions.
1.2.1. Allowed Cell Rate (ACR)
Definition: An ABR service parameter, ACR is the current rate
(cells/second) at which a source is allowed to send.
Discussion: For ABR traffic, ACR constitutes the actual data throughput
for a particular VC. The time change of this value effects TCP round
trip time calculations, which in turn effects TCP throughput.
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Specification: AF-TM4.0
1.2.2. ACR Decrease Time Factor (ADTF)
Definition: This is the time permitted between sending RM-cells before
the rate is decreased to ICR (Initial Cell Rate). The time units are
.01 to 10.23 seconds
with a granularity of 10 ms.
Discussion: For ABR traffic, ADTF constitutes the time rate of the ACR.
This value effects TCP round trip time calculations, which in turn
effects TCP throughput.
Specification: AF-TM4.0
1.2.3. Additive Increase Rate (AIR)
Definition: An ABR service parameter, AIR controls the rate at which the
cell transmission rate increases. It is signaled as AIRF, where
AIRF = AIR*Nrm/PCR.
Discussion: For ABR traffic, AIR effects the time rate of change of the
ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput.
Specification: AF-TM4.0
1.2.4. Additive Increase Rate Factor (AIRF)
Definition: Refer to AIR.
Discussion: Refer to AIR.
Specification: AF-TM4.0
1.2.5. Available Bit Rate (ABR)
Definition: ABR is an ATM layer service category for which the limiting
ATM layer transfer characteristics provided by the network may change
subsequent to connection establishment. A flow control mechanism is
specified which supports several types of feedback to control the source
rate in response to changing ATM layer transfer characteristics.
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
obtain a fair share of the available bandwidth according to a network
specific allocation policy. Cell delay variation is not controlled in
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this service, although admitted cells are not delayed unnecessarily.
Specification: AF-TM4.0
1.2.6. 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
ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput.
Specification: AF-TM4.0
1.2.7. Initial Cell Rate (ICR)
Definition: An ABR service parameter, in cells/sec, that is the rate at
which a source should send initially and after an idle period.
Discussion: none.
Specification: AF-TM4.0
1.2.8. Minimum Cell Rate (MCR)
Definition: An ABR service traffic descriptor, in cells/sec, that is the
rate at which the source is always allowed to send.
Discussion: none.
Specification: AF-TM4.0
1.2.9. Mrm
Definition: An ABR service parameter that controls allocation of
bandwidth between forward W-cells, backward RM-cells, and data cells.
Discussion: none.
Specification: AF-TM4.0
1.2.10. Nrm
Definition: An ABR service parameter, Nrm is the maximum number of cells
a source may send for each forward RM-cell.
Discussion: none.
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Specification: AF-TM4.0
1.2.11. 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
ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput.
Specification: AF-TM4.0
1.2.12. Rate Increase Factor (RIF)
Definition: This controls the amount by which the cell transmission 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.
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
effects TCP throughput.
Specification: AF-TM4.0
1.2.13. Resource Management (RM) Cells
Definition: RM cells are used to convey network status (available
bandwidth, congestion levels) and request peak cell rates for ATM
blocks. The RM cell has the following format:
Header: 5 bytes, same as the ATM cell header
Protocol ID: 3 bytes, value is ID1
Function specific field: 45 bytes, data required for the specific protocol
Rsvd: 6 bytes, reserved for future specification
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
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
identified with a PT of 6.
Specification: AF-TM4.0
1.2.14. 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
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10 cells/second.
Discussion: none.
Specification: AF-TM4.0
1.2.15. TDF
Definition: An ABR service parameter, TDF controls the decrease in ACR
associated with TOF. TDF is signaled as TDFF, where TDF=TDFF/RDF times
the smallest power of 2 greater or equal to PCR. TDF is in units of
1/seconds.
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
effects TCP throughput.
Specification: AF-TM4.0
1.2.16. TDFF
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.
Discussion: Refer to TDF.
Specification: AF-TM4.0
1.2.17. Time Out Factor (TOF)
Definition: An ABR service parameter, TOF controls the maximum time
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.
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
effects TCP throughput.
Specification: AF-TM4.0
1.2.18. Time Out Factor (TOFF)
Definition: Refer to TOF.
Discussion: none.
Specification: AF-TM4.0
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1.2.19. Trm
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
power 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
ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput.
Specification: AF-TM4.0
1.2.20. Virtual Source/Virtual Destination (VSND)
Definition: An ABR connection may be divided into two or more separately
controlled ABR segments. Each ABR control segment, except the first, is
sourced by a virtual source. A virtual source implements the behavior of
an ABR source endpoint. Backward RM-cells received by a virtual source
are removed from the connection. Each ABR control segment, except the
last, is terminated by a virtual destination. A virtual destination
assumes the behavior of an ABR destination endpoint. Forward RM-cells
received by a virtual destination are turned around and not forwarded to
the next segment of the connection.
Discussion: none.
Specification: AF-TM4.0
1.2.21. Xrm Decrease Factor (XDM)
Definition: An ABR service parameter, XDF controls the decrease in ACR
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
ACR. This value effects TCP round trip time calculations, which in turn
effects TCP throughput.
Specification: AF-TM4.0
1.2.22. Xrm
Definition: An ABR service parameter, Xrm limits the number of forward
RM- cells which may be sent in the absence of received backward PM-
cells. The range is 0-255.
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
effects TCP throughput.
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Specification: AF-TM4.0
2. Performance Metrics
2. 1. Definition Format (from RFC 1242)
Metric to be defined.
Definition: The specific definition for the metric.
Discussion: A brief discussion of the metric, its application and any
restrictions on measurement procedures.
Measurement units: Intrinsic units used to quantify this metric. This
includes subsidiary units; e.g., microseconds are acceptable if the
intrinsic unit is seconds.
2.2. Definitions
2.2.1. ABR Rate Decrease Response Time (ARDRT)
Definition: The amount of time required by the SUT to adjust its
transmission rate based on an ABR rate decrease request.
Discussion: During the ARDRT, cells transmitted by the SUT 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.
Measurement Units: seconds
2.2.2. ABR Rate Increase Response Time (ARIRT)
Definition: The amount of time required by the SUT to adjust its
transmission rate based on an ABR rate increase request.
Discussion: During the ARIRT, the SUT will not fully utilize the
available bandwidth. This will negatively impact IP and TCP throughput.
Measurement Units: seconds
2.2.3. 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.
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RM-CLR = Lost RM Cells / Total RM Cells Transmitted.
Discussion: RM-CLR may cause the SUT to transmit data cells at a rate
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.
It is expressed as an order of magnitude, having a range of 10^-1 to
10^- 15 and unspecified.
Measurement Units: dimensionless.
3. Security Considerations.
As this document is solely for providing terminology and describes
neither a protocol nor an implementation, there are no security
considerations associated with this document.
4. Notices
Internet Engineering Task Force
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to pertain
to the implementation or use of the technology described in this
document or the extent to which any license under such rights might or
might not be available; neither does it represent that it has made any
effort to identify any such rights. Information on the IETFs procedures
with respect to rights in standards-track and standards-related
documentation can be found in BCP-11. Copies of claims of rights made
available for publication and any assurances of licenses to be made
available, or the result of an attempt made to obtain a general license
or permission for the use of such proprietary rights by implementors or
users of this specification can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary rights,
which may cover technology that may be required to practice this
standard. Please address the information to the IETF Executive
Director.
5. Disclaimer
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and
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distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are included
on all such copies and derivative works. However, this document itself
may not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet
Standards process must be followed, or as required to translate it into
languages other than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. This
document and the information contained herein is provided on an "AS IS"
basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE
DISCLAIMS 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.
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-
tm- 0056.00, April 1996.
[AF-TM4.1] ATM Forum, Traffic Management Specification Version 4.1
(final ballot), btd-tm-01.02, July 1998.
[AF-UNI3.1] ATM Forum, User Network Interface Specification Version 3.1,
September 1994.
[AF-UNI4.0] ATM Forum, User Network Interface Specification Version 4.0,
July 1996.
7. Editors Addresses
Jeffrey Dunn
Advanced Network Consultants, Inc.
4214 Crest Place, Ellicott City, MD 21043 USA
Phone: +1 (410) 750-1700, E-mail: Jeffrey.Dunn@worldnet.att.net
Cynthia Martin
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Advanced Network Consultants, Inc.
4214 Crest Place, Ellicott City, MD 21043 USA
Phone: +1 (410) 750-1700, E-mail: Cynthia.E.Martin@worldnet.att.net
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