draft-ietf-bmwg-call-02.txt   draft-ietf-bmwg-call-03.txt 
Network Working Group J. H. Dunn Network Working Group J. H. Dunn
INTERNET-DRAFT Hewlett-Packard INTERNET-DRAFT Hewlett-Packard
Expires in six months C. E. Martin Expires in six months C. E. Martin
Hewlett-Packard Hewlett-Packard
August 1998 October 1998
Terminology for Call/Cell Benchmarking Terminology for Call/Cell Benchmarking
draft-ietf-bmwg-call-02.txt <draft-ietf-bmwg-call-03.txt>
Status of this Memo Status of this Memo
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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 benchmarking tests and the results of these tests in the context of cell-
of cell-based and call-based switching devices. The terms defined based and call-based switching devices. The terms defined in this
in this memo will be used in addition to terms defined in RFCs memo will be used in addition to terms defined in RFCs 1242, 1944
1242, 1944 and 2285. This memo is a product of the Benchmarking and 2285. This memo is a product of the Benchmarking Methodology
Methodology Working Group (BMWG) of the Internet Engineering Task Working Group (BMWG) of the Internet Engineering Task Force
Force (IETF). (IETF).
I. Background I. Background
1. Introduction 1. Introduction. This document provides terminology for
benchmarking cell-based and call-based switching devices. It extends
This document provides terminology for benchmarking cell-based and terminology already defined for benchmarking network interconnect
call-based switching devices. It extends terminology already devices in RFCs 1242, 1944 and 2285 . Although some of the
defined for benchmarking network interconnect devices in RFCs definitions in this memo may be applicable to a broader group of
1242, 1944 and 2285. Although some of the definitions in this network interconnect devices, the primary focus of the terminology in
this memo is on cell-based and call-based switches. Specifically, this
memo may be applicable to a broader group of network interconnect includes Asynchronous Transfer Mode (ATM) cell relay and signaling
devices, the primary focus of the terminology in this memo is on and Frame Relay (FR) signaling.
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. This memo contains two major sections: Background and Definitions.
Within the definitions section are a formal definitions sub- Within the definitions section is a formal definitions subsection,
section, provided as a courtesy to the reader, and a measurement provided as a courtesy to the reader, and a measurement definitions
definitions sub-section which contains performance metrics with sub-section, which contains performance metrics with inherent units.
inherent units.
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 2. Existing Definitions
RFC 1242 "Benchmarking Terminology for Network Interconnect RFC 1242 "Benchmarking Terminology for Network Interconnect
Devices" should be consulted before attempting to make use of this Devices" should be consulted before attempting to make use of this
document. RFC 1944 "Benchmarking Methodology for Network document. RFC 1944 "Benchmarking Methodology for Network
Interconnect Devices" contains discussions of a number of terms Interconnect Devices" contains discussions of a number of terms
relevant to the benchmarking of switching devices and should also relevant to the benchmarking of switching devices and should also be
be consulted. RFC 2285 "Benchmarking Terminology for LAN consulted. RFC 2285 "Benchmarking Terminology for LAN
Switching Devices" contains a number of terms pertaining to Switching Devices" contains a number of terms pertaining to traffic
traffic distributions and datagram interarrival. distributions and datagram interarrival. For the sake of clarity and
For the sake of clarity and continuity this RFC adopts the continuity this RFC adopts the template for definitions set out in
template for definitions set out in Section 2 of RFC 1242. Section 2 of RFC 1242. Definitions are indexed and grouped together
Definitions are indexed and grouped together in sections for ease in sections for ease of reference. The key words "MUST", "MUST
of reference. NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and in this document are to be interpreted as described in RFC 2119.
"OPTIONAL" in this document are to be interpreted as described in
RFC 2119.
II. Definitions II. Definitions
The definitions presented in this section have been divided into The definitions presented in this section have been divided into two
two groups. The first group is formal definitions, which are groups. The first group is formal definitions, which are required in the
required in the definitions of the performance metrics but are not definitions of the performance metrics but are not themselves strictly
themselves strictly metrics. These definitions are subsumed from metrics. These definitions are subsumed from other work done in
other work done in other working groups both inside and outside other working groups both inside and outside the IETF. They are
the IETF. They are provided as a courtesy to the reader. provided as a courtesy to the reader.
1. Formal Definitions 1. Formal Definitions
1.1. Definition Format (from RFC1242) 1.1. Definition Format (from RFC1242)
Term to be defined. Term to be defined.
Definition: The specific definition for the term. Definition: The specific definition for the term.
Discussion: A brief discussion of the term, its application and Discussion: A brief discussion of the term, its application and any
any restrictions on measurement procedures. restrictions on measurement procedures.
Specification: The working group and document in which the term Specification: The working group and document in which the term is
is specified. Listed in the references. specified. Listed in the references.
1.2 Definitions 1.2. ATM Related Definitions.
1.2.1 Available Bit Rate (ABR): 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:
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:
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:
Specification: AF-TM4.0
1.2.4. Additive Increase Rate Factor (AIRF):
Definition: Refer to AIR.
Discussion:
Specification: AF-TM4.0
1.2.5. ATM Adaptation Layer (AAL):
Definition: The layer in the B-ISDN reference model (see B-ISDN)
which adapts higher layer PDUs into the ATM layer.
Discussion: There are 4 types of adaptation layers:
- AAL1: used for circuit emulation, voice over ATM
- AAL2: used for sub-rated voice over ATM
- AAL3/4: used for data over noisy ATM lines
- AAL5: used for data over ATM, most widely used AAL type
These AAL types are not measurements, but it is possible to measure
the time required for Segmentation and Reassembly (SAR).
Specification: AF-UNI3.1
1.2.6. ATM Adaptation Layer Type 5 (AAL5):
Definition: AAL5 functions in support of variable bit rate, delay-
tolerant data traffic requiring minimal sequencing or error detection
support.
Discussion: AAL5 is the adaptation layer for UNI signaling, ILMI,
PNNI signaling, and for IP PDUËs. It is the most widely used AAL
type to date.
Specification: AF-UNI3.1
1.2.7. Available Bit Rate (ABR):
Definition: ABR is an ATM layer service category for which the Definition: ABR is an ATM layer service category for which the
limiting ATM layer transfer characteristics provided by the limiting ATM layer transfer characteristics provided by the network
network may change subsequent to connection establishment. A flow may change subsequent to connection establishment. A flow control
control mechanism is specified which supports several types of mechanism is specified which supports several types of feedback to
feedback to control the source rate in response to changing ATM control the source rate in response to changing ATM layer transfer
layer transfer characteristics. characteristics.
Discussion: It is expected that an end-system that adapts its Discussion: It is expected that an end-system that adapts its traffic in
traffic in accordance with the feedback will experience a low cell accordance with the feedback will experience a low cell loss ratio and
loss ratio and obtain a fair share of the available bandwidth obtain a fair share of the available bandwidth according to a network
according to a network specific allocation policy. Cell delay specific allocation policy. Cell delay variation is not controlled in this
variation is not controlled in this service, although admitted service, although admitted cells are not delayed unnecessarily.
cells are not delayed unnecessarily.
Specification: AF-TM4.0 Specification: AF-TM4.0
1.2.2 Call-based 1.2.8. Asynchronous Transfer Mode (ATM)
Definition: An association between two or more users or between a Definition: A transfer mode in which the information is organized into
user and a network entity that is established by the use of 53 octet PDUs called cells. It is asynchronous in the sense that the
recurrence of cells containing information from an individual user is
not necessarily periodic.
Discussion: ATM is based on the ISDN model.
Specification: AF-UNI3.1
1.2.9. ATM Link:
Definition: A virtual path link (VPL) or a virtual channel link (VCL).
Discussion: none.
Specification: AF-UNI3.1
1.2.10. ATM Peer-to-Peer Connection:
Definition: A virtual channel connection (VCC) or a virtual path
connection (VPC).
Discussion: none.
Specification: AF-UNI3.1
1.2.11. ATM Traffic Descriptor:
Definition: A generic list of traffic parameters, which specify the
intrinsic traffic characteristics of a requested ATM connection. See
GCRA.
Discussion:
Specification: AF-UNI3.1
1.2.12. ATM User-User Connection:
Definition: An association established by the ATM Layer to support
communication between two or more ATM service users (i.e., between
two or more next higher entities or between two or more ATM-
entities). The communications over an ATM Layer connection may be
either bi-directional or unidirectional. The same Virtual Channel
Identifier (VCI) issued for both directions of a connection at an
interface.
Discussion: none.
Specification: AF-UNI3.1
1.2.13. Backward Explicit Congestion Notification (BECN):
Definition: A Resource Management (RM) cell type generated by the
network or the destination, indicating congestion or approaching
congestion for traffic flowing in the direction opposite that of the
BECN cell.
Discussion:
Specification: AF-TM4.0
1.2.14. BECN Cell (BN):
Definition: A Resource Management (RM) cell type indicator. The
network or the destination may generate a Backwards Explicit
Congestion Notification (BECN) RM-cell. To do so, BN=1 is set, to
indicate the cell is not source-generated, and DIR=1 to indicate the
backward flow. Source generated RM-cells are initialized with BN=0.
Discussion:
Specification: AF-TM4.0
1.2.15. Broadband ISDN (B-ISDN) Model:
Definition: A layered service model that specifies the mapping of
higher layer protocols onto ATM and its underlying physical layer.
The model is composed of four layers: Physical, ATM, AAL and
Service.
Discussion: none.
Specification: AF-UNI3.1
1.2.16. Burst Tolerance (BT):
Definition: A traffic parameter, which, along with the Sustainable
Cell Rate (SCR), specifies the maximum number of cells which will be
accepted at the Peak Cell Rate (PCR) on an ATM connection.
Discussion: BT applies to ATM connections supporting VBR services
and is the limit parameter of the GCRA.
Specification: AF-TM4.0
1.2.17. Connection Admission Control (CAC):
Definition: Connection Admission Control is defined as the set of
actions taken by the network during the call set- up phase (or during
call re-negotiation phase) in order to determine whether a connection
request can be accepted or should be rejected (or whether a request for
re-allocation can be accommodated).
Discussion: none
Specification: AF-UNI3.1
1.2.18. Call:
Definition: A call is 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 network capabilities. This association may have zero or more
connections. connections.
Discussion: none Discussion: none
Specification: AF-UNI3.1 Specification: AF-UNI3.1
1.2.3 Cell 1.2.19. Call-based
Definition: A unit of transmission in ATM. A fixed size frame Definition: An association between two or more users or between a
consisting of a 5 octet header and a 48 octet payload. 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
1.2.20. Constant Bit Rate (CBR):
Definition: An ATM service category which supports a constant or
guaranteed rate to transport services such as video or voice as well as
circuit emulation which requires rigorous timing control and
performance parameters.
Discussion:
Specification: AF-UNI3.1
1.2.21. 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
1.2.22. Cell Header:
Definition: ATM Layer protocol control information.
Discussion: The ATM cell header is a 5-byte header that contains the
following fields:
- Generic Flow Control (GFC): 4 bits
- Virtual Path Identifier (VPI): 8 bits
- Virtual Channel Identifier (VCI): 16 bits
- Payload Type (PT): 3 bits
- Cell Loss Priority (CLP): 1 bit
- Header Error Check (HEC): 8 bit CRC computed over the
previous 4 octets
Each field is discussed in the ATM Specific definition section of this
document.
Specification: AF-UNI3.1
1.2.23. Congestion Indicator (CI):
Definition: This is a field in a RM-cell, and is used to cause the source
to decrease its ACR. The source sets CI=0 when it sends a RM-cell.
Setting CI=1 is typically how destinations indicate that Explicit
Forward Congestion Indication (EFCI) has been received on a previous
data cell.
Discussion:
Specification: AF-TM4.0
1.2.24. Cell Loss Priority (CLP):
Definition: This bit in the ATM cell header indicates two levels of
priority for ATM cells. CLP=0 cells are higher priority than CLP=1
cells. CLP=1 cells may be discarded during periods of congestion to
preserve the CLR of CLP=0 cells.
Discussion: The CLP bit is used to determine GCRA contract
compliance.
Specification: AF-UNI3.1
1.2.25. Connection:
Definition: An ATM connection consists of concatenation of ATM
Layer links in order to provide an end-to-end information transfer
capability to access points.
Discussion: none.
Specification: AF-UNI3.1
1.2.26. Cutoff Decrease Factor (CDF):
Definition: CDF controls the decrease in ACR (Allowed Cell Rate)
associated with CRM.
Discussion:
Specification: AF-TM4.0
1.2.27. Current Cell Rate (CCR):
Definition: The Current Cell Rate is an RM-cell field set by the source
to its current ACR when it generates a forward RM-cell. This field
may be used to facilitate the calculation of ER, and may not be
changed by network elements. CCR is formatted as a rate.
Discussion:
Specification: AF-TM4.0
1.2.28. Cyclic Redundancy Check (CRC):
Definition: A mathematical algorithm that computes a numerical value
based on the bits in a block of data. This number is transmitted with
the data and the receiver uses this information and the same algorithm
to insure the accurate delivery of data by comparing the results of
algorithm and the number received. If a mismatch occurs, an error in
transmission is presumed.
Discussion: CRC is not a measurement, but it is possible to measure
the amount of time to perform a CRC on a string of bits. This
measurement will not be addressed in this document.
Specification: AF-UNI3.1
1.2.29. DIR:
Definition: This is a field in a RM-cell, which indicates the direction
of the RM-cell with respect to the data flow with which it is associated.
The source sets DIR=0 and the destination sets DIR=1.
Discussion: none
Specification: AF-TM4.0
1.2.30. Explicit Forward Congestion Indication (EFCI):
Definition: EFCI is an indication in the PTI field of the ATM cell
header. A network element in an impending-congested state or a
congested state may set EFCI so that this indication may be examined
by the destination end-system. For example, the end- system may use
this indication to implement a protocol that adaptively lowers the cell
rate of the connection during congestion or impending congestion. A
network element that is not in a congestion state or an impending
congestion state will not modify the value of this indication.
Impending congestion is the state when network equipment is
operating around its engineered capacity level.
Discussion:
Specification: AF-TM4.0
1.2.31. Explicit Rate (ER):
Definition: The Explicit Rate is a RM-cell field used to limit the source
ACR to a specific value. It is initially set by the source to a requested
rate (such as PCR). It may be subsequently reduced by any network
element in the path to a value that the element can sustain. ER is
formatted as a rate.
Discussion:
Specification: AF-TM4.0
1.2.32. End System (ES):
Definition: A system where an ATM connection is terminated or
initiated. An originating end system initiates the ATM connection, and
terminating end system terminates the ATM connection. OAM cells
may be generated and received.
Discussion: An ES can be the user side of a UNI signaling interface.
Specification: AF-TEST
1.2.33. Generic Cell Rate Algorithm (GCRA):
Definition: The GCRA is used to define conformance with respect to
the traffic contract of the connection. For each cell arrival the GCRA
determines whether the cell conforms to the traffic contract. The UPC
function may implement the GCRA, or one or more equivalent
algorithms to enforce conformance. The GCRA is defined with two
parameters: the Increment (I) and the Limit (L).
Discussion: GCRA is not a measurement, but there are a number of
measurements that can be obtained using the GCRA and other
parameters.
Specification: AF-TM4.0
1.2.34. Generic Flow Control (GFC):
Definition: GFC is a field in the ATM header, which can be used to
provide local functions (e.g., flow control). It has local significance
only and the value encoded in the field is not carried end-to-end.
Discussion: none
Specification: AF-UNI3.1
1.2.35. Header Error Control (HEC):
Definition: A check character calculated using an 8 bit CRC computed
over the first 4 octets of the ATM cell header. This allows for single
bit error correction or multiple bit error detection.
Discussion: none
Specification: AF-UNI3.1
1.2.36. 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
1.2.37. Integrated Local Management Interface
Definition: A management protocol which uses SNMP carried on
AAL5 to provide ATM network devices with status and configuration
information concerning VPCs, VCCs, registered ATM addresses and
the capabilities of ATM interfaces.
Discussion: ILMI is a conditionally required portion of UNI3.1;
however, ILMI 4.0 has been issued as a separate specification. This
document will refer to ILMI 4.0.
Specification: ILMI4.0
1.2.38. Intermediate System (IS):
Definition: A system that provides forwarding functions or relaying
functions or both for a specific ATM connection. OAM cells may be
generated and received.
Discussion: An IS can be either the user or network side of a UNI
signaling interface, or the network side of a PNNI signaling interface.
Specification: AF-TEST
1.2.39. Leaky Bucket (LB):
Definition: Leaky Bucket is the term used as an analogous description
of the algorithm used for conformance checking of cell flows from a
user or network. See GCRA, UPC and NPC. The "leaking hole in the
bucket" applies to the sustained rate at which cells can be
accommodated, while the "bucket depth" applies to the tolerance to
cell bursting over a given time period.
Discussion: There are two types of LB algorithms- single and dual.
Single LB defines a PCR, dual LB defines a PCR and SCR.
Specification: AF-TM4.0
1.2.40. Maximum Cell Rate (MCR):
Definition: This is the maximum capacity usable by connections
belonging to the specified service category.
Discussion: none
Specification: AF-TM4.0
1.2.41. Maximum Burst Size (MBS):
Definition: In the signaling message, the Burst Tolerance (BT) is
conveyed through the MBS that is coded as a number of cells. The BT
together with the SCR and the GCRA determine the MBS that may be
transmitted at the peak rate and still is in conformance with the GCRA.
Discussion: none
Specification: AF-TM4.0
1.2.42. 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
1.2.43. Missing RM-Cell Count (CRM):
Definition: CRM limits the number of forward RM-cells that may be
sent in the absence of received backward RM-cells.
Discussion:
Specification: AF-TM4.0
1.2.44. Mrm:
Definition: An ABR service parameter that controls allocation of
bandwidth between forward RM-cells, backward RM-cells, and data
cells.
Discussion: none
Specification: AF-TM4.0
1.2.45. Nrm:
Definition: An ABR service parameter, Nrm is the maximum number
of cells a source may send for each forward RM-cell.
Discussion: none.
Specification: AF-TM4.0
1.2.46. Operations Administration and Maintenance (OAM):
Definition: A group of network management functions that provide
network fault indication, performance information, and data and
diagnosis functions.
Discussion: There are four types of ATM OAM flows: segment or
end-to-end VP termination management (i.e. F4 segment, F4 E2E) and
segment or end-to-end VC termination management (i.e. F5 segment,
F5 E2E). These OAM cells can be used to identify fault management,
connection verification, and loopback measurements.
Specification: AF-UNI3.1
1.2.47. Protocol Data Unit (PDU):
Definition: A PDU is a message of a given protocol comprising
payload and protocol-specific control information, typically contained
in a header. PDUs pass over the protocol interfaces that exist between
the layers of protocols (per OSI model).
Discussion: In ATM networks, a PDU can refer to an ATM cell,
multiple ATM cells, an AAL segment, an IP datagram and others.
Specification:
1.2.48. Private Network-Network Interface (PNNI):
Definition: A routing information protocol that enables extremely
scalable, full function, dynamic multi-vendor ATM switches to be
integrated in the same network.
Discussion: PNNI consists of signaling and routing between ATM
network devices. PNNI signaling is based on UNI 4.0 signaling
between two network side interfaces, while PNNI routing provides a
mechanism to route ATM cells between two separate, autonomous
ATM networks.
Specification: AF-PNNI1.0
1.2.49. Payload Type Indicator (PTI):
Definition: Payload Type Indicator is the Payload Type field value
distinguishing the various management cells and user cells. Example:
Resource Management cell has PTI=110, end-to-end OAM F5 Flow
cell has PTI=101.
Discussion: none.
Specification: AF-UNI3.1
1.2.50. Peak Cell Rate (PCR):
Definition: A traffic parameter, which specifies the upper bound on
the rate at which ATM cells can be submitted to an ATM connection.
This parameter is used by the GCRA.
Discussion:
Specification: AF-TM4.0
1.2.51. Permanent Virtual Circuit (PVC):
Definition: This is a link with static route defined in advance, usually
by manual setup.
Discussion: PVCËs are widely deployed in WAN ATM networks€
Specification: AF-UNI3.1
1.2.52. Permanent Virtual Channel Connection (PVCC):
Definition: A Virtual Channel Connection (VCC) is an ATM
connection where switching is performed on the VPI/VCI fields of
each cell. A Permanent VCC is one that is provisioned through some
network management function and left up indefinitely.
Discussion: none.
Specification: AF-UNI3.1
1.2.53. Permanent Virtual Path Connection: (PVPC):
Definition: A Virtual Path Connection (VPC) is an ATM connection
where switching is performed on the VPI field only of each cell. A
Permanent VPC is one that is provisioned through some network
management function and left up indefinitely.
Discussion: none.
Specification: AF-UNI3.1
1.2.54. 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:
Specification: AF-TM4.0
1.2.55. 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 1/32768 to 1.
Discussion:
Specification: AF-TM4.0
1.2.56. Resource Management (RM):
Definition: Resource Management is the management of critical
resources in an ATM network. Two critical resources are buffer space
and trunk bandwidth. Provisioning may be used to allocate network
resources in order to separate traffic flows according to service
characteristics. VPCs play a key role in resource management. By
reserving capacity on VPCs, the processing required to establish
individual VCCs is reduced. Refer to RM-cell.
Discussion:
Specification: AF-TM4.0
1.2.57. Resource Management Cell (RM-Cell):
Definition: Information about the state of the network like bandwidth
availability, state of congestion, and impending congestion, is
conveyed to the source through special control cells called Resource
Management Cells (RM-cells).
Discussion:
Specification: AF-TM4.0
1.2.58. Segmentation and Reassembly (SAR):
Definition: The process used by the AAL in the B-ISDN reference
model (see B-ISDN) which fragments higher layer PDUs into ATM
cells.
Discussion: SAR is not a measurement, but the speed in which SAR
can be completed on a bit stream can be measured. This measurement
will not be discussed in this document.
Specification:
1.2.59. Sustainable Cell Rate (SCR):
Definition: The SCR is an upper bound on the conforming average rate
of an ATM connection over time scales which are long relative to
those for which the PCR is defined. Enforcement of this bound by the
UPC could allow the network to allocate sufficient resources, but less
than those based on the PCR, and still ensure that the performance
objectives (e.g., for Cell Loss Ratio) can be achieved.
Discussion:
Specification: AF-TM4.0
1.2.60. Switched Virtual Circuit (SVC):
Definition: A connection established via signaling. The user defines
the endpoints when the call is initiated.
Discussion: SVCËs are established using either UNI signaling or PNNI
signaling. The signaling mechanism follows a specific state
machine€
Specification: AF-UNI3.1
1.2.61. Switched Virtual Channel Connection (SVCC):
Definition: A Switched VCC is one that is established and taken down
dynamically through control signaling. A Virtual Channel Connection
(VCC) is an ATM connection where switching is performed on the
VPI/VCI fields of each cell.
Discussion: none.
Specification: AF-UNI3.1
1.2.62. Switched Virtual Path Connection (SVPC):
Definition: A Switched Virtual Path Connection is one that is
established and taken down dynamically through control signaling. A
Virtual Path Connection (VPC) is an ATM connection where
switching is performed on the VPI field only of each cell.
Discussion: none.
Specification: AF-UNI3.1
1.2.63. Switched Connection:
Definition: A connection established via signaling.
Discussion: none.
Specification: AF-UNI3.1
1.2.64. 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:
Specification: AF-TM4.0
1.2.65. Traffic Contract
Definition: A specification of the negotiated traffic characteristics of
an ATM connection.
Discussion:
Specification: AF-TM4.0
1.2.66. Transmission Convergence (TC):
Definition: A sub-layer of the physical layer of the B-ISDN model
transforms the flow of cells into a steady flow of bits and bytes for
transmission over the physical medium. On transmit, the TC sublayer
maps the cells to the frame format, generates the Header Error Check
(HEC), and sends idle cells when the ATM layer has none to send. On
reception, the TC sublayer delineates individual cells in the received
bit stream, and uses the HEC to detect and correct received errors.
Discussion: TC is not a measurement, but the speed in which TC can
occur on a bit stream can be measured. This measurement will not be
discussed in this document.
Specification: AF-UNI3.1
1.2.67. 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:
Specification: AF-TM4.0
1.2.68. 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:
Specification: AF-TM4.0
1.2.69. Traffic Management (TM):
Definition: Traffic Management is the aspect of the traffic control
and congestion control procedures for ATM. ATM layer traffic
control refers to the set of actions taken by the network to avoid
congestion conditions. ATM layer congestion control refers to the set
of actions taken by the network to minimize the intensity, spread and
duration of congestion. The following functions form a framework for
managing and controlling traffic and congestion in ATM networks and
may be used in appropriate combinations.
o Connection Admission Control
o Feedback Control
o Usage Parameter Control
o Priority Control
o Traffic Shaping
o Network Resource Management
o Frame Discard
o ABR Flow Control
Discussion:
Specification: AF-TM4.0
1.2.70. 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:
Specification: AF-TM4.0
1.2.71. Time Out Factor (TOFF):
Definition: Refer to TOF.
Discussion: none Discussion: none
Specification: AF-TM4.0
1.2.72. 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:
Specification: AF-TM4.0
1.2.73. Traffic Shaping (TS):
Definition: Traffic Shaping is a mechanism that alters the traffic
characteristics of a stream of cells on a connection to achieve better
network efficiency, while meeting the QoS objectives, or to ensure
conformance at a subsequent interface. Traffic shaping must maintain
cell sequence integrity on a connection. Shaping modifies traffic
characteristics of a cell flow with the consequence of increasing the
mean Cell Transfer Delay.
Discussion:
Specification: AF-UNI3.1
1.2.74. Unspecified Bit Rate (UBR):
Definition: UBR is an ATM service category, which does not specify
traffic related service guarantees. Specifically, UBR does not include
the notion of a per-connection negotiated bandwidth. No numerical
commitments are made with respect to the cell loss ratio experienced
by a UBR connection, or as to the cell transfer delay experienced by
cells on the connection.
Discussion: UBR is used with € traffic type€
Specification: AF-TM4.0
1.2.75. User-Network Interface (UNI):
Definition: An interface point between ATM end users and a private
ATM switch, or between a private ATM switch and the public carrier
ATM network; defined by physical and protocol specifications per
ATM Forum UNI documents. The standard adopted by the ATM
Forum to define connections between users or end stations and a local
switch.
Discussion:
Specification: AF-UNI3.1
1.2.76. Usage Parameter Control (UPC):
Definition: Usage Parameter Control is defined as the set of actions
taken by the network to monitor and control traffic, in terms of traffic
offered and validity of the ATM connection, at the end-system access.
Its main purpose is to protect network resources from malicious as well
as unintentional misbehavior, which can affect the QoS of other
already established connections, by detecting violations of negotiated
parameters and taking appropriate actions.
Discussion:
Specification: AF-TM4.0
1.2.77. Variable Bit Rate (VBR):
Definition: An ATM Forum defined service category which supports
variable bit rate data traffic with average and peak traffic parameters.
Discussion:
Specification: AF-TM4.0
1.2.78. VC:
Definition: A communications channel that provides for the sequential
unidirectional transport of ATM cells.
Discussion:
Specification: AF-UNI3.1
1.2.79. Virtual Channel Connection (VCC):
Definition: A concatenation of VCIs that extends between the points
where the ATM service users access the ATM layer. The points at
which the ATM cell payload is passed to, or received from, the users
of the ATM Layer (i.e., a higher layer or ATM-entity) for processing
signify the endpoints of a VCC. VCCs are unidirectional.
Discussion:
Specification: AF-UNI3.1
1.2.80. Virtual Channel Identifier (VCI):
Definition: A unique numerical tag as defined by a 16 bit field in the
ATM cell header that identifies a virtual channel, over which the cell is
to travel.
Discussion:
Specification: AF-UNI3.1
1.2.81. Virtual Path (VP):
Definition: A unidirectional logical association or bundle of VCs.
Discussion:
Specification: AF-UNI3.1
1.2.82. Virtual Path Connection (VPC):
Definition: A concatenation of VPIs between Virtual Path Terminators
(VPTs). VPCs are unidirectional
Discussion:
Specification: AF-UNI3.1
1.2.83. Virtual Path Identifier (VPI):
Definition: An eight-bit field in the ATM cell header that indicates the
virtual path over which the cell should be routed.
Discussion:
Specification: AF-UNI3.1 Specification: AF-UNI3.1
1.2.84. Virtual Source/Virtual Destination (VS/VD):
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:
Specification: AF-TM4.0
1.2.85. 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:
Specification: AF-TM4.0
1.2.86. Xrm:
Definition: An ABR service parameter, Xrm limits the number of
forward RM-cells which may be sent in the absence of received
backward RM-cells. The range is 0-255.
Discussion:
Specification: AF-TM4.0
1.3. Frame Relay Related Definitions
1.3.1. Backward Explicit Congestion Notification (BECN):
Definition: BECN is a bit in the frame relay header. The bit is set by a
congested network node in any frame that is traveling in the reverse
direction of the congestion.
Discussion:
Specification: FRF
1.3.2. Committed Information Rate (CIR):
Definition: CIR is the transport speed the frame relay network will
maintain between service locations when data is presented.
Discussion:
Specification: FRF
1.3.3. Discard Eligible:
Definition: This is a 1-bit field in a frame relay header that provides a
two level priority indicator, used to bias discard frames in the event of
congestion toward lower priority frames. Similar to the CLP bit in
ATM.
Discussion:
Specification: FRF
1.3.4. Forward Explicit Congestion Notification (FECN):
Definition: FECN is a bit in the frame relay header. The bit is set by a
congested network node in any frame that is traveling in the same
direction of the congestion.
Discussion:
Specification: FRF
1.3.5. Frame:
Definition: A logical grouping of information sent as a link-layer unit
over a transmission medium.
Discussion:
Specification: FRF
1.3.6. Frame Relay:
Definition: A high-performance interface for packet-switching
networks; considered more efficient that X.25. Frame relay
technology can handle "bursty" communications that have rapidly
changing bandwidth requirements.
Discussion:
Specification: FRF
2. Performance Metrics 2. Performance Metrics
2.1. Definition Format (from RFC1242) 2.1. Definition Format (from RFC1242)
Metric to be defined. Metric to be defined.
Definition: The specific definition for the metric. Definition: The specific definition for the metric.
Discussion: A brief discussion of the metric, its application and Discussion: A brief discussion of the metric, its application and any
any restrictions on measurement procedures. restrictions on measurement procedures.
Measurement units: Intrinsic units used to quantify this metric. Measurement units: Intrinsic units used to quantify this metric. This
This includes subsidiary units, e.g. microseconds are acceptable includes subsidiary units, e.g. microseconds are acceptable if the
if the intrinsic unit is seconds. intrinsic unit is seconds.
2.2 Definitions 2.2 Definitions
2.2.1 Cell Transfer Delay (CTD) 2.2.1. Cell Delay Variation (CDV):
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
2.2.2 Cell Delay Variation (CDV)
Definition: The variation in cell transfer delay associated with Definition: The variation in cell transfer delay associated with a given
a given traffic load, orientation and distribution, as well as an traffic load, orientation and distribution, as well as an integration
integration period. CDV = max(CTD) - min(CTD) where max and min period. CDV = max(CTD) - min(CTD) where max and min indicate
indicate the maximum and minimum over the integration period, the maximum and minimum over the integration period, respectively.
respectively.
Discussion: CDV is a component of cell transfer delay, induced by Discussion: CDV is a component of cell transfer delay, induced by
buffering and cell scheduling. Peak-to-peak CDV is a QoS delay buffering and cell scheduling. Peak-to-peak CDV is a QoS delay
parameter associated with CBR and VBR services. The peak-to-peak 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 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. 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.
2.2.3 Cell Error Ratio (CER) Measurement Units: seconds
Definition: The ratio of errored cells in a transmission in 2.2.2. Cell Delay Variation Tolerance (CDVT):
relation to the total cells sent in a transmission associated with
a given traffic load, orientation and distribution, as well as an Definition: ATM layer functions may alter the traffic characteristics of
integration period. CER = Errored Cells / Total Cells ATM connections by introducing Cell Delay Variation. When cells
Transmitted. from two or more ATM connections are multiplexed, cells of a given
ATM connection may be delayed while cells of another ATM
connection are being inserted at the output of the multiplexer.
Similarly, some cells may be delayed while physical layer overhead or
OAM cells are inserted. Consequently, some randomness may affect
the inter-arrival time between consecutive cells of a connection as
monitored at the UNI. The upper bound on the "clumping" measure is
the CDVT.
Discussion:
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 Discussion: The measurement is taken over a time interval and is
desirable to be measured on an in-service circuit. desirable to be measured on an in-service circuit.
Measurement Units: dimensionless. Measurement Units: dimensionless.
2.2.4 Cell Loss Ratio (CLR) 2.2.4. Cell Loss Ratio (CLR):
Definition: The ratio of lost cells in a transmission in relation Definition: The ratio of lost cells in a transmission in relation to the
to the total cells sent in a transmission associated with a given total cells sent in a transmission associated with a given traffic load,
traffic load, orientation and distribution, as well as an orientation and distribution, as well as an integration period. CLR =
integration period. CLR = Lost Cells / Total Cells Transmitted. Lost Cells / Total Cells Transmitted.
Discussion: CLR is a negotiated QoS parameter and acceptable Discussion: CLR is a negotiated QoS parameter and acceptable values
values are network specific. The objective is to minimize CLR are network specific. The objective is to minimize CLR provided the
provided the end-system adapts the traffic to the changing ATM end-system adapts the traffic to the changing ATM layer transfer
layer transfer characteristics. The CLR parameter is the value of characteristics. The CLR parameter is the value of CLR that the
CLR that the network agrees to offer as an objective over the network agrees to offer as an objective over the lifetime of the
lifetime of the connection. It is expressed as an order of connection. It is expressed as an order of magnitude, having a range of
magnitude, having a range of 10-1 to 10-15 and unspecified. 10-1 to 10-15 and unspecified.
Measurement Units: dimensionless. Measurement Units: dimensionless.
2.2.5 Cell Misinsertion Rate (CMR) 2.2.5. Cell Misinsertion Rate (CMR):
Definition: The ratio of cells received at an endpoint that were Definition: The ratio of cells received at an endpoint that were not
not originally transmitted by the source end in relation to the originally transmitted by the source end in relation to the total number
total number of cells properly transmitted associated with a given of cells properly transmitted associated with a given traffic load,
traffic load, orientation and distribution, as well as an orientation and distribution, as well as an integration period. CMR =
integration period. CMR = Mis-inserted Cells / Total Cells Mis-inserted Cells / Total Cells Transmitted.
Transmitted.
Discussion: none Discussion: none
Measurement Units: dimensionless. Measurement Units: dimensionless.
3. Security Considerations 2.2.6. Cell Rate Margin (CRM):
Security issues are not addressed in this memo.
4. References Definition: This is a measure of the difference between the effective
bandwidth allocation and the allocation for sustainable rate in cells per
second.
Discussion:
Measurement units: Cells per second
2.2.7. CRC Error Ratio:
Definition: The ratio of PDUs received at an endpoint that which
contain an invalid CRC 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.
Discussion
Measurement Units: dimensionless
2.2.8. 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
3. Security Considerations.
As this document is solely for the purpose of providing terminology
and describes neither a protocol nor an implementation, there are no
security considerations associated with this document.
4. References
[ILMI4.0] ATM Forum Integrated Local Management Interface
Version 4.0, af-ilmi-0065.000, September 1996.
[AF-TEST] Introduction to ATM Forum Test Specifications, af-test-
0022.00, December 1994.
[AF-TM4.0] ATM Forum, Traffic Management Specification Version [AF-TM4.0] ATM Forum, Traffic Management Specification Version
4.0, af-tm-0056.00, April 1996. 4.0, af-tm-0056.00, April 1996.
[AF-UNI3.1] ATM Forum, User Network Interface Specification [AF-UNI3.1] ATM Forum, User Network Interface Specification
Version 3.1, September 1994. Version 3.1, September 1994.
5. Editor's Addresses 5. Editor's Addresses
Jeffrey Dunn Jeffrey Dunn
Hewlett-Packard Hewlett-Packard 3701 Koppers St. Baltimore, MD 21227 USA
3701 Koppers St. Phone: +1 (410) 362-7612 E-mail: jeff_dunn@hp.com
Baltimore, MD 21227 USA
Phone: +1 (410) 362-7612
E-mail: jeff_dunn@hp.com
Cynthia Martin Cynthia Martin
Hewlett-Packard Hewlett-Packard 3701 Koppers St. Baltimore, MD 21227 USA
3701 Koppers St. Phone +1 (410) 362-7631 E-mail: cynthia_martin@hp.com
Baltimore, MD 21227
Phone +1 (410) 362-7631
E-mail: cynthia_martin@hp.com
 End of changes. 

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