INTERNET-DRAFT Call/Cell Benchmarking Terminology August 1998
Network Working Group J. H. Dunn
INTERNET-DRAFT Hewlett-Packard
Expires in six months C. E. Martin
Hewlett-Packard
August 1998
Terminology for Call/Cell Benchmarking
draft-ietf-bmwg-call-02.txt
Status of this Memo
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Abstract
This memo discusses and defines terms associated with performance
benchmarking tests and the results of these tests in the context
of cell-based and call-based switching devices. The terms defined
in this memo will be used in addition to terms defined in RFCs
1242, 1944 and 2285. This memo is a product of the Benchmarking
Methodology Working Group (BMWG) of the Internet Engineering Task
Force (IETF).
I. Background
1. Introduction
This document provides terminology for benchmarking cell-based and
call-based switching devices. It extends terminology already
defined for benchmarking network interconnect devices in RFCs
1242, 1944 and 2285. Although some of the definitions in this
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memo may be applicable to a broader group of network interconnect
devices, the primary focus of the terminology in this memo is on
cell-based and call-based switches. Specifically, this includes
Asynchronous Transfer Mode (ATM) cell relay and signaling and
Frame Relay (FR) signaling.
This memo contains two major sections: Background and Definitions.
Within the definitions section are a formal definitions sub-
section, provided as a courtesy to the reader, and a measurement
definitions sub-section which contains performance metrics with
inherent units.
2. Existing Definitions
RFC 1242 "Benchmarking Terminology for Network Interconnect
Devices" should be consulted before attempting to make use of this
document. RFC 1944 "Benchmarking Methodology for Network
Interconnect Devices" contains discussions of a number of terms
relevant to the benchmarking of switching devices and should also
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.
Definitions are indexed and grouped together in sections for ease
of reference.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
RFC 2119.
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.
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1. Formal Definitions
1.1. Definition Format (from RFC1242)
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 term
is specified. Listed in the references.
1.2 Definitions
1.2.1 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 this service, although admitted
cells are not delayed unnecessarily.
Specification: AF-TM4.0
1.2.2 Call-based
Definition: An association between two or more users or between a
user and a network entity that is established by the use of
network capabilities. This association may have zero or more
connections.
Discussion: none
Specification: AF-UNI3.1
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1.2.3 Cell
Definition: A unit of transmission in ATM. A fixed size frame
consisting of a 5 octet header and a 48 octet payload.
Discussion: none
Specification: AF-UNI3.1
2. Performance Metrics
2.1. Definition Format (from RFC1242)
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 Cell Transfer Delay (CTD)
Definition: The elapsed time between a cell exit event at the
measurement point 1 (e.g., at the source UNI) and the
corresponding cell entry event at a measurement point 2 (e.g., the
destination UNI) for a particular connection.
Discussion: The 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.
Measurement units: seconds
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2.2.2 Cell Delay Variation (CDV)
Definition: The variation in cell transfer delay associated with
a given traffic load, orientation and distribution, as well as an
integration period. CDV = max(CTD) - min(CTD) where max and min
indicate the maximum and minimum over the integration period,
respectively.
Discussion: CDV is a component of cell transfer delay, induced by
buffering and cell scheduling. Peak-to-peak CDV is a QoS delay
parameter associated with CBR and VBR services. The peak-to-peak
CDV is the ((1-a) quantile of the CTD) minus the fixed CTD that
could be experienced by any delivered cell on a connection during
the entire connection holding time. The parameter "a" is the
probability of a cell arriving late.
Measurement Units: seconds.
2.2.3 Cell Error Ratio (CER)
Definition: The ratio of errored cells in a transmission in
relation to the total cells sent in a transmission associated with
a given traffic load, orientation and distribution, as well as an
integration period. CER = Errored Cells / Total Cells
Transmitted.
Discussion: The measurement is taken over a time interval and is
desirable to be measured on an in-service circuit.
Measurement Units: dimensionless.
2.2.4 Cell Loss Ratio (CLR)
Definition: The ratio of lost cells in a transmission in relation
to the total cells sent in a transmission associated with a given
traffic load, orientation and distribution, as well as an
integration period. CLR = Lost Cells / Total Cells Transmitted.
Discussion: CLR is a negotiated QoS parameter and acceptable
values are network specific. The objective is to minimize CLR
provided the end-system adapts the traffic to the changing ATM
layer transfer characteristics. The CLR parameter is the value of
CLR that the network agrees to offer as an objective over the
lifetime of the connection. It is expressed as an order of
magnitude, having a range of 10-1 to 10-15 and unspecified.
Measurement Units: dimensionless.
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2.2.5 Cell Misinsertion Rate (CMR)
Definition: The ratio of cells received at an endpoint that were
not originally transmitted by the source end in relation to the
total number of cells properly transmitted associated with a given
traffic load, orientation and distribution, as well as an
integration period. CMR = Mis-inserted Cells / Total Cells
Transmitted.
Discussion: none
Measurement Units: dimensionless.
3. Security Considerations
Security issues are not addressed in this memo.
4. References
[AF-TM4.0] ATM Forum, Traffic Management Specification Version
4.0, af-tm-0056.00, April 1996.
[AF-UNI3.1] ATM Forum, User Network Interface Specification
Version 3.1, September 1994.
5. Editor's Addresses
Jeffrey Dunn
Hewlett-Packard
3701 Koppers St.
Baltimore, MD 21227 USA
Phone: +1 (410) 362-7612
E-mail: jeff_dunn@hp.com
Cynthia Martin
Hewlett-Packard
3701 Koppers St.
Baltimore, MD 21227
Phone +1 (410) 362-7631
E-mail: cynthia_martin@hp.com
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