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+Network Working Group                                           J. Dunn
+Request for Comments: 2761                                    C. Martin
+Category: Informational                                       ANC, Inc.
+                                                          February 2000
+
+
+                    Terminology for ATM Benchmarking
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2000).  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. The terms
+   defined in this memo will be used in addition to terms defined in
+   RFCs 1242, 2285, and 2544. This memo is a product of the Benchmarking
+   Methodology Working Group (BMWG) of the Internet Engineering Task
+   Force (IETF).
+
+Introduction
+
+   This document provides terminology for benchmarking ATM based
+   switching devices. It extends terminology already defined for
+   benchmarking network interconnect devices in RFCs 1242, 2285, and
+   2544. 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 is on ATM cell relay and signaling.
+
+   This memo contains two major sections: Background and Definitions.
+   Within the definitions section is a formal definitions subsection,
+   provided as a courtesy to the reader, and a measurement definitions
+   sub-section, that contains performance metrics with inherent units.
+   The divisions of the measurement sub-section follow the BISDN model.
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                      [Page 1]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   The BISDN model comprises four layers and two planes. This document
+   addresses the interactions between these layers and how they effect
+   IP and TCP throughput. A schematic of the B-ISDN model follows:
+
+   ---------|--------------------------|-------------------------------
+            |     User Plane           |       Control Plane
+   ---------|--------------------------|--------------------------------
+   Services |          IP              |   ILMI   |       UNI, PNNI
+   ---------|--------------------------|----------|---------------------
+   AAL      | AAL1, AAL2, AAL3/4, AAL5 |   AAL5   |        SAAL
+   ---------|--------------------------|----------|---------------------
+   ATM      |      Cell Relay          |        OAM, RM
+   ---------|--------------------------|--------------------------------
+            |       Convergence        |
+   Physical |--------------------------|--------------------------------
+            |         Media            |
+   ---------|--------------------------|--------------------------------
+
+   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).  This document covers only CBR, VBR and UBR traffic
+   types.  ABR will be handled in a separate document.  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.
+
+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.
+   Definitions are indexed and grouped together in sections for ease of
+
+
+
+Dunn & Martin                Informational                      [Page 2]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   reference.  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
+   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
+   "OPTIONAL" go in this document are to be interpreted as described in
+   RFC 2119.
+
+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.  These discussions pertain
+   solely to the impact of a particular ATM parameter on IP or TCP;
+   therefore, definitions which contain no configurable components or
+   whose components will have the discussion: None.
+
+   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. 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 four types of adaptation layers: AAL 1: used
+   for circuit qemulation, 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
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                      [Page 3]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   These AAL types are not measurements, but it is possible to measure
+   the time required for Segmentation and Reassembly (SAR).
+
+   Specification: I.363
+
+1.2.2. ATM Adaptation Layer Type 5 (AAL5)
+
+   Definition: AAL5 adapts multi-cell higher layer PDUs into ATM with
+   minimal error checking and no error detection.  The AAL5 CPCS (Common
+   Paer Convergence Sub-layer) PDU is defined as follows:
+
+|---------------------------|---------------------------|--------------|
+|    Higher Layer PDU       |   Padding (If needed)     |    Trailer   |
+|---------------------------|---------------------------|--------------|
+
+   Where the padding is used to ensure that the trailer occupies the
+   final 8 octets of the last cell.
+
+   The trailer is defined as follows:
+
+   |--------------|--------------|--------------|--------------|
+   |   CPCS-UU    |     CPI      |    Length    |   CRC-32     |
+   |--------------|--------------|--------------|--------------|
+
+   where:
+
+   CPCS-UU is the 1 octet Common Part Convergence Sub-layer User to User
+   Indication and may be used to communicate between two AAL5 entities.
+
+   CPI is the 1 octet Common Part Indicator and must be set to 0.
+
+   Length is the 2 octet length of the higher layer PDU.
+
+   CRC-32 is a 32 bit (4 octet) cyclic redundancy check over the entire
+   PDU.
+
+   Discussion: AAL5 is the adaptation layer for UNI signaling, ILMI,
+   PNNI signaling, and for IP PDUs. It is the most widely used AAL type
+   to date.  AAL5 requires two distinct processes.  The first is the
+   encapsulation, on the transmit side, and de-encapsulation, on the
+   receive side, of the higher layer PDU into the AAL5 CPCS PDU which
+   requires the computation of the length and the CRC-32.  The time
+   required for this process depends on whether the CRC-32 computation
+   is done on the interface (on-board) or in machine central memory (in
+   core).  On-board computation should produce only a small, constant
+   delay; however, in core computation will produce variable delay,
+   which will negatively effect TCP RTT computations. The second process
+   is segmentation and re-assembly (SAR) which is defined below (see
+
+
+
+Dunn & Martin                Informational                      [Page 4]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   SAR).
+
+   Specification: I.363.5
+
+1.2.3. Asynchronous Transfer Mode (ATM)
+
+   Definition: A transfer mode in which the information is organized
+   into 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; however, unlike ISDN, ATM
+   uses fixed length (53 octet) cells. Because of the fixed length of
+   ATM PDUs, higher layer PDUs must be adapted into ATM using one of the
+   four ATM adaptation layers (see AAL).
+
+   Specification: AF-UNI3.1
+
+1.2.4. ATM Link
+
+   Definition: A virtual path link (VPL) or a virtual channel link
+   (VCL).
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.5. ATM Peer-to-Peer Connection
+
+   Definition: A virtual channel connection (VCC) or a virtual path
+   connection (VPC).
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.6. ATM Traffic Descriptor
+
+   Definition: A generic list of traffic parameters, which specify the
+   intrinsic traffic characteristics of a requested ATM connection (see
+   GCRA), which must include PCR and QoS and may include BT, SCR and
+   best effort (UBR) indicator.
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                      [Page 5]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   Discussion: The effects of each traffic parameter will be discussed
+   individually.
+
+   Specification: AF-UNI3.1
+
+1.2.7. 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) is issued for both directions of a connection at an
+   interface.
+
+   Discussion: Because ATM is connection oriented, certain features of
+   IP (i.e. those which require multicast) are not available.
+
+   Specification: AF-UNI3.1
+
+1.2.8. 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: See discussion above.
+
+   Specification: I.321
+
+1.2.9. 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. BT will effect TCP and IP PDU
+   loss in that cells presented to an interface which violate the BT may
+   be dropped, which will cause AAL5 PDU corruption. BT will also effect
+   TCP RTT calculation.  BT=(MBS-1)*(1/SCR 1/PCR) (see MBS, PCR, SCR).
+
+   Specification: AF-TM4.0
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                      [Page 6]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.10. 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
+   connections.
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.11. 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
+
+1.2.12. Call-based
+
+   Definition: A transport requiring call setups - see CALL definition.
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.13. Cell Delay Variation Tolerance (CDVT)
+
+   Definition: ATM layer functions may alter the traffic characteristics
+   of ATM connections by introducing Cell Delay Variation. When cells
+   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: CDVT effects TCP round trip time calculations.  Large
+   values of CDVT will adversely effect TCP throughput and cause SAR
+   timeout.  See discussion under SAR.
+
+   Specification: AF-TM4.0
+
+
+
+
+
+
+Dunn & Martin                Informational                      [Page 7]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.14. 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 four octets
+
+   Each field is discussed in this document.
+
+   Specification: AF-UNI3.1
+
+1.2.15. 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.  Specifically, two traffic contracts may apply to a
+   single connection:  CLP=0, meaning only cells with CLP=0, and
+   CLP=0+1, meaning cells with CLP=0 or CLP=1.
+
+   Specification: AF-UNI3.1
+
+1.2.16. 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
+
+1.2.17. 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).
+
+
+
+
+
+
+Dunn & Martin                Informational                      [Page 8]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   Discussion: CAC is based on the ATM traffic descriptor (see ATM
+   traffic descriptor) associated with the call as well as the presented
+   and existing load.  It may also be based on administrative policies
+   such as calling party number required or access limitations. The
+   effect on performance of these policies is beyond the scope of this
+   document and will be handled in the BMWG document: Benchmarking
+   Terminology for Firewall Performance.
+
+   Specification: AF-UNI3.1
+
+1.2.18. Constant Bit Rate (CBR)
+
+   Definition: An ATM service category which supports a constant and
+   guaranteed rate to transport services such as video or voice as well
+   as circuit emulation which requires rigorous timing control and
+   performance parameters.  CBR requires the specification of PCR and
+   QoS (see PCR and QoS).
+
+   Discussion: Because CBR provides minimal cell delay variation (see
+   CDV), it should improve TCP throughput by stabilizing the RTT
+   calculation.  Further, as CBR generally provides a high priority
+   service, meaning that cells with a CBR traffic contract usually take
+   priority over other cells during congestion, TCP segment and IP
+   packet loss should be minimized.  The cost associated with using CBR
+   is the loss of statistical multiplexing.  Since CBR guarantees both
+   throughput and CDV control, the connections must be subscribed at
+   PCR.  This is extremely wasteful as most protocols, e.g., TCP, only
+   utilize full bandwidth on one half of a bi-directional connection.
+
+   Specification: AF-UNI3.1
+
+1.2.19. 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, 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. See discussion
+   under AAL5.
+
+   Specification: AF-UNI3.1
+
+
+
+
+
+Dunn & Martin                Informational                      [Page 9]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.20. 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-0022
+
+1.2.21. 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: EFCI may be used to prevent congestion by alerting a
+   positive acknowledgement protocol and causing action to be taken.  In
+   the case of TCP, when EFCI cells are received the driver software
+   could alert the TCP software of impending congestion.  The TCP
+   receiver would then acknowledge the current segment and set the
+   window size to some very small number.
+
+   Specification: AF-TM4.0
+
+1.2.22. 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: The GCRA increment and limit parameters are mapped to CBR
+   and VBR in the following fashion.  For CBR, I=1/PCR and L=CDVT (CDV
+   tolerance).  For VBR, there are two GCRA algorithms running (dual
+   leaky bucket).  The first functions in the same fashion .bp as CBR,
+   I=1/PCR and L=CDVT.  The second, which polices cells which are in
+   conformance with the first GCRA uses I=1/SCR and L=BT (see BT, CDV,
+
+
+
+Dunn & Martin                Informational                     [Page 10]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   MBS, PCR and SCR).
+
+   Specification: AF-TM4.0
+
+1.2.23. 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
+
+1.2.24. Guaranteed Frame Rate (GFR)
+
+   Definition: The GFR service provides the user with a Minimum Cell
+   Rate (MCR) guarantee under the assumption of a given maximum frame
+   size (MFS) and a given Maximum Burst Size (MBS).  The MFS and MBS are
+   both expressed in units of cells.  GFR only applies to virtual
+   channel connections (VCCs).
+
+   Discussion: GFR is intended for users who are either not able to
+   specify the range of traffic parameters needed to request most ATM
+   services, or are not equipped to comply with the (source) behavior
+   rules required by existing ATM services.  Specifically, GFR provides
+   the user with the following minimum service guarantee: When the
+   network is congested, all frames whose length is less than MFS and
+   presented to the ATM interface in bursts less than MBS and at a rate
+   less than PCR will be handled with minimum frame loss.  When the
+   network is not congested, the user can burst at higher rates.
+
+   The effect of GFR on performance is somewhat problematic as the
+   policing algorithm associated with GFR depends on the network load;
+   however, under congested condition and assuming a user who is
+   following the GFR service agreement, it should improve performance.
+
+   Specification: AF-TM4.1
+
+
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 11]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.25. 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
+
+1.2.26. Integrated Local Management Interface
+
+   Definition: A management protocol which uses SNMPv1 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: AF-ILMI4.0
+
+1.2.27. 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-0022
+
+1.2.28. 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 and UPC.  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 is used in CBR; dual LB is used in VBR (see CBR and VBR).
+
+   Specification: AF-TM4.0
+
+
+
+Dunn & Martin                Informational                     [Page 12]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.29. 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 PCR determine the MBS that may be
+   transmitted at the peak rate and still is in conformance with the
+   GCRA.
+
+   Discussion: See the discussion under BT.
+
+   Specification: AF-TM4.0
+
+1.2.30. Maximum Frame Size (MFS)
+
+   Definition: The MFS is the maximum length of a frame, expressed in
+   units of cells, which in interface implementing GFR will accept
+   during congested conditions (see GFR).
+
+   Discussion: During congestion, frames whose size is in excess of the
+   MFS may be dropped or tagged.  Assuming that the user is adhering to
+   the MFS limit, this behavior should improve performance by improving
+   congestion.
+
+   Specification: AF-TM4.1
+
+1.2.31. 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 loop back measurements.
+
+   Specification: AF-UNI3.1
+
+
+
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 13]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.32. Payload Type Indicator (PTI)
+
+   Definition: Payload Type Indicator is the Payload Type field value
+   distinguishing the various management cells and user cells as well as
+   conveying explicit forward congestion indication (see EFCI).
+   Example:  Resource Management cell is indicated as PTI=110, End-to-
+   end OAM F5 Flow cell is indicated as PTI=101.
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.33. 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: PCR directly limits the maximum data rate on an ATM
+   connection.  If a user violates the PCR, cells may be dropped
+   resulting in Cell Loss.  This in turn will negatively impact AAL5
+   PDUs, which may be carrying IP datagrams.  See the discussion under
+   SAR.
+
+   Specification: AF-TM4.0
+
+1.2.34. Permanent Virtual Circuit (PVC)
+
+   Definition: This is a link with static route(s) defined in advance,
+   usually by manual setup.
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.35. 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
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 14]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.36. 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
+
+1.2.37. 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
+
+1.2.38. 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: Common Usage
+
+1.2.39. 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. Although this
+   measurement is not included in this document, it should be noted that
+   the manner in which SAR is performed will greatly effect performance.
+   SAR can be performed either on the interface card (on board) or in
+   machine central memory (in core).  On-board computation should
+
+
+
+Dunn & Martin                Informational                     [Page 15]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   produce only a small, constant delay; however, in core computation
+   will produce variable delay, which will negatively effect TCP RTT
+   computations.  This situation is further complicated by the location
+   of the CRC-32 calculation.  Given an in core CRC-32 calculation, bus
+   contention may cause on board SAR to be slower than in core SAR.
+   Clearly, on board CRC-32 calculation and SAR will produce the most
+   favorable performance results.
+
+   SAR performance will also be effected by ATM layer impairments.  Cell
+   error (CE), cell loss(CL), cell mis-insertion (CM) and cell delay
+   variation (CDV) will all negatively effect SAR.  CE will cause an
+   AAL5 PDU to fail the CRC-32 check and be discarded, thus discarding
+   the packet which the PDU contained.  CL and CM will both cause an
+   AAL5 PDU to fail the length check and be discarded.  CL can have
+   other effects depending on whether the cell which was lost is the
+   final cell (PTI=1) of the AAL5 PDU.  The following discussion
+   enumerates the possibilities.
+
+   1. PTI=0 cell is lost.  In this case, re-assembly registers a length
+   discrepancy and discards the PDU.
+
+   2. PTI=1 cell is lost.
+
+   2.  A.  The AAL5 re-assembly timer expires before the first cell,
+   PTI=0, of the next AAL5 PDU arrives.  The AAL5 PDU with the missing
+   PTI=1 cell is discarded due to re-assembly timeout and one packet is
+   lost.
+
+   2.  B.  The first cell of the next AAL5 PDU arrives before the re-
+   assembly timer expires.  The AAL5 with the missing PTI=1 cell is
+   prepended to the next AAL5 PDU in the SAR engine.  This yields two
+   possibilities:
+
+   2. B. i. The AAL5 re-assembly timer expires before the last cell,
+   PTI=1, of the next AAL5 PDU arrives.  The AAL5 PDU with the missing
+   PTI=1 cell and the next AAL5 PDU are discarded due to re-assembly
+   timeout and two packets are lost.
+
+   2. B. ii. The last cell of the next AAL5 PDU arrives before the re-
+   assembly timer expires.  In this case, AAL5 registers a length
+   discrepancy and discards the PDU; therefore, the AAL5 PDU with the
+   missing PTI=1 cell and the next AAL5 PDU are discarded due to their
+   concatenation and two packets are lost.
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 16]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   2. C. Coupled with re-assembly, there exists some mechanism for
+   identifying the start of a higher layer PDU, e.g., IP, and the cells
+   associated with the first incomplete AAL5 PDU are discarded,
+   resulting in the loss of one packet.
+
+   Specification: AF-UNI3.1
+
+1.2.40. 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: SCR limits the average data rate on an ATM connection.
+   If a user violates the SCR, cells may be dropped resulting in Cell
+   Loss.  This in turn will negatively impact AAL5 PDUs, which may be
+   carrying IP datagrams.  See the discussion under SAR.
+
+   Specification: AF-TM4.0
+
+1.2.41. Switched Connection
+
+   Definition: A connection established via signaling.
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.42. 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
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 17]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.43. Switched Virtual Circuit (SVC)
+
+   Definition: A connection established via signaling. The user defines
+   the endpoints when the call is initiated.
+
+   Discussion: SVCs are established using either UNI signaling or PNNI
+   signaling.  The signaling state machine implements several timers,
+   which can effect the time required for call establishment.  This will
+   effect TCP round trip time calculation, effecting TCP throughput.
+   Specifically, there are two possibilities.  In the case where Call
+   Proceeding is not implemented, there is only one timer, T310, with a
+   value of 10 seconds.  In the case where Call Proceeding is
+   implemented, there are two timers, T303 and T310, with the values 4
+   and 10 seconds, respectively.  In either case, if a timer, either
+   T303 or T310, expires after a Setup message is send, the calling
+   party has the option of re-transmitting the Setup.  In the T303 case,
+   this yields a maximum setup time of 18 seconds and, In the T310 case,
+   a maximum setup time of 20 seconds.  Thus, the initial TCP RTT
+   calculation will be on he order of 20 seconds.
+
+   Specification: AF-UNI3.1, AF-UNI4.0, AF-PNNI1.0
+
+1.2.44. 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
+
+1.2.45. Traffic Contract
+
+   Definition: A specification of the negotiated traffic characteristics
+   of an ATM connection.
+
+   Discussion: See discussions under BT, CAC, CDV, GCRA, PCR and SCR.
+
+   Specification: AF-TM4.0
+
+1.2.46. 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
+
+
+
+Dunn & Martin                Informational                     [Page 18]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   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.
+
+      Connection Admission Control
+      Feedback Control
+      Usage Parameter Control
+      Priority Control
+      Traffic Shaping
+      Network Resource Management
+      Frame Discard
+      ABR Flow Control
+
+   Discussion: See CAC and traffic shaping.
+
+   Specification: AF-TM4.0
+
+1.2.47. 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: TS should improve TCP throughput by reducing RTT
+   variations.  As a result, TCP RTT calculations should be more stable.
+
+   Specification: AF-UNI3.1
+
+1.2.48. 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.
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 19]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   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; however, its value should be constant and
+   small with respect to cell inter-arrival at the maximum data rate.
+
+   Specification: AF-UNI3.1
+
+1.2.49. 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
+   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: RFC 2331 specifies UBR service class for IP over ATM.
+   UBR service models the "best effort" service type specified in RFC
+   791; however, UBR has specific drawbacks with respect to TCP service.
+   Since UBR makes no guarantee with respect to cell loss (CL), cell
+   delay variation (CDV) or cell mis-insertion(CM), TCP RTT estimates
+   will be highly variable.  Further, all negatively impact AAL5 re-
+   assembly, which in turn may cause packet loss.  See discussions under
+   CDV and SAR.
+
+   Specification: AF-TM4.0
+
+1.2.50. 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 established connections, by detecting violations of negotiated
+   parameters and taking appropriate actions.
+
+   Discussion: See discussions under BT, CAC, CDV, GCRA, PCR and SCR.
+
+   Specification: AF-TM4.0
+
+1.2.51. 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.
+
+
+
+Dunn & Martin                Informational                     [Page 20]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.52. 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: VBR may potentially adversely effect TCP throughput due
+   to large RTT variations.  This in turn will cause the TCP RTT
+   estimates to be unstable.
+
+   Specification: AF-TM4.0
+
+1.2.53.  Virtual  Channel  (VC)
+
+   Definition: A communications channel that provides for the sequential
+   unidirectional transport of ATM cells.
+
+   Discussion: none.
+
+   Specification: AF-TM3.1
+
+1.2.54. 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: none.
+
+   Specification: AF-TM3.1
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 21]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+1.2.55. 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: none.
+
+   Specification: AF-UNI3.1
+
+1.2.56. Virtual Path (VP)
+
+   Definition: A unidirectional logical association or bundle of VCs.
+
+   Discussion: none.
+
+   Specification: AF-UNI3.1
+
+1.2.57. Virtual Path Connection (VPC)
+
+   Definition: A concatenation of VPIs between Virtual Path Terminators
+   (VPTs). VPCs are unidirectional
+
+   Discussion: none.
+
+   Specification: AF-TM3.1
+
+1.2.58. 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: none.
+
+   Specification: AF-UNI3.1
+
+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.
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 22]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   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. Physical Layer - SONET
+
+2.2.1.1. Pointer Movements
+
+   Definition: Pointer Movements is the number of changes in a SONET
+   pointer due to clock synchronization slips.
+
+   Discussion: SONET Pointer Movements can cause loss of information in
+   the SONET payload envelop (SPE) which contains IP datagrams, either
+   in the form of ATM cells or as PPP delimited PDUs.
+
+   Measurement Units: Per second.
+
+2.2.1.2. Transport Overhead Error Count
+
+   Definition: SONET Transport Overhead Error Count is the number of
+   SONET transport overhead errors detected.
+
+   Discussion: SONET Transport Overhead Errors SONET Transport Overhead
+   Errors cause SONET frames to be lost.  These frames may contain IP
+   datagrams; either in the form of cells or as PPP delimited PDUs.
+
+   Measurement Units: Positive integer
+
+2.2.1.3. Path Overhead Error Count
+
+   Definition: SONET Path Overhead Error Count is the number of SONET
+   path overhead errors detected.
+
+   Discussion: SONET Path Overhead Errors cause SONET frames to be lost.
+   These frames may contain IP datagrams; either in the form of cells or
+   as PPP delimited PDUs.
+
+   Measurement Units: Positive integer
+
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 23]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+2.2.2. ATM Layer
+
+2.2.2.1. Cell Delay Variation (CDV)
+
+   Definition: The variation in cell transfer delay (CTD) 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.
+
+   CDV effects TCP round trip time calculations.  Large values of CDV
+   will adversely effect TCP throughput and cause SAR timeout.  See
+   discussion under SAR.
+
+   Measurement Units: seconds
+
+2.2.2.2. Cell Error Ratio (CER)
+
+   Definition: The ratio of cells with payload errors in a transmission
+   in relation to the total number of 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
+   cell header will cause cell loss at the ATM layer.  Note further that
+   multiple errors in a payload will only be counted as one cell payload
+   error.
+
+        CER = Cells with payload errors / Total Cells Transmitted.
+
+   Discussion: The measurement is taken over a time interval and is
+   desirable to be measured on an in-service circuit.  CER is closely
+   related to the number of corrupted AAL5 PDUs; however, there is not a
+   direct numerical correlation between the number of errored cells and
+   the number of corrupted AAL5 PDUs.  There are two cases described
+   below.
+
+   1. Only one cell in an AAL5 PDU contains payload errors.  In this
+   case, there is a one-to-one correspondence between cell payload
+   errors and the number of corrupted AAL5 PDUs.
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 24]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   2. Multiple cells in the AAL5 PDU contain payload errors. In this
+   case, there is not a one-to-one correspondence between cell payload
+   errors and the number of corrupted AAL5 PDUs.
+
+   Measurement Units: dimensionless.
+
+2.2.2.3. 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.
+
+   CLR indicates the number of ATM cells lost in relation to the total
+   number of cells sent. CLR is closely related to the number of
+   corrupted AAL5 PDUs; however, there is not a direct numerical
+   correlation between the number of cells lost and the number of
+   corrupted AAL5 PDUs.  See the discussion under SAR.
+
+   Measurement Units: dimensionless.
+
+2.2.2.4. Cell Misinsertion Ratio (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 = Misinserted Cells / Total Cells Transmitted.
+
+   Discussion: The measurement is taken over a time interval and is
+   desirable to be measured on an in-service circuit.  CMR is closely
+   related to the number of corrupted AAL5 PDUs; however, there is not a
+   direct numerical correlation between the number of mis-inserted cells
+   and the number of corrupted AAL5 PDUs.  There are two cases described
+   below.
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 25]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   1.  Only one cell is mis-inserted into an AAL5 PDU.  In this case,
+   there is a one-to-one correspondence between cell mis-insertion and
+   the number of corrupted AAL5 PDUs.
+
+   2.  Multiple cells are mis-inserted into an AAL5. In this case, there
+   is not a one-to-one correspondence between cell mis-insertion and the
+   number of corrupted AAL5 PDUs.
+
+   Measurement Units: dimensionless.
+
+2.2.2.5. Cell Rate Margin (CRM)
+
+   Definition: This is a measure of the difference between the effective
+   bandwidth allocation and the allocation for sustainable rate in cells
+   per second.
+
+   Discussion: This measures the amount of provisioned bandwidth which
+   is not utilized.  This lack of utilization may be caused by
+   encapsulation overhead, e.g., AAL5 trailer and padding, or by the
+   protocol itself, e.g., TCP usually transmits in only one direction.
+
+   Measurement units: Cells per second
+
+2.2.2.6. 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: CRC errors cause ATM cells to be lost.  Although this
+   will appear as cell loss at the ATM layer, this measurement can be
+   made in-service using a test probe which measures CRC errors at the
+   TC layer.
+
+   Measurement Units: dimensionless
+
+2.2.2.7. 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.
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 26]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   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.  While this number is a constant and
+   should not adversely effect performance, it is a component in RTT.
+
+   Measurement units: seconds
+
+2.2.3. ATM Adaptation Layer (AAL) Type 5 (AAL5)
+
+2.2.3.1. AAL5 Re-assembly Errors
+
+   Definition: AAL5 Re-assembly Errors constitute any error, which
+   causes the AAL5 PDU to be corrupted.
+
+   Discussion: AAL5 Re-assembly errors cause AAL5 PDUs to be lost.
+   These PDUs may contain IP datagrams.
+
+   Measurement Units: Positive Integer
+
+2.2.3.2. AAL5 Reassembly Time
+
+   Definition: AAL5 Reassembly Time constitutes the time between the
+   arrival of the final cell in the AAL5 PDU and the AAL5 PDUs payload
+   being made available to the service layer.
+
+   Discussion: AAL5 Reassembly time directly effects TCP round trip time
+   calculations.
+
+   Measurement Units: seconds
+
+2.2.3.3. AAL5 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: AAL5 CRC errors cause AAL5 re-assembly errors.  See
+   discussion under AAL5 re-assembly errors.
+
+   Measurement Units: dimensionless
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 27]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+2.2.4. ATM Service: Signaling
+
+2.2.4.1. CAC Denial Time
+
+   Definition: The amount of time required for CAC to determine that a
+   call must be rejected.
+
+   Discussion: In the case where Call Proceeding is implemented, this
+   number will be less than 4 seconds. Otherwise, it will be less than
+   10 seconds.  Large values of this measurement will adversely effect
+   performance on systems where an alternate, non-NBMA, service is
+   available.
+
+   Measurement Units: seconds
+
+2.2.4.2. Connection Establishment Time
+
+   Definition: The amount of time between the first Setup message from
+   the calling party and the Connect message to the calling party.
+
+   Discussion:  See discussion under SVC.
+
+   Measurement Units: seconds
+
+2.2.4.3. Connection Teardown Time
+
+   Definition: The amount of between the Release message being sent and
+   the Release Complete message being received.
+
+   Discussion: Large values of this measurement will adversely effect
+   performance in systems where the total number of open calls or VCs is
+   limited.  Specifically, a new VC cannot be instantiated with the same
+   VPI/VCI before the old one is released.
+
+   Measurement Units: seconds
+
+2.2.4.4. Crankback Time
+
+   Definition: The amount of time between the issuance of the first
+   release or release complete message by the switch where the current
+   Designated Transit List (DTL) is blocked and the receipt of the SETUP
+   with the updated DTLs by the target switch.
+
+   Discussion: This measurement does not take into account the amount of
+   time associated with either the successful portion of the call setup
+   transit or the time required for the calling party to receive .bp a
+   response from the called party.  As a result, the call may still fail
+   to complete if the call setup timer on the calling party expires.
+
+
+
+Dunn & Martin                Informational                     [Page 28]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   See discussion under SVC.
+
+   Measurement Units: seconds
+
+2.2.4.5. Route Update Response Time
+
+   Definition: The amount of time between the receipt of a PNNI Topology
+   State Element (PTSE), which is the PNNI routing PDU, containing a
+   topology different from the current topology and the point at which
+   the switch begins to generate DTLs reflecting the routing change.
+
+   Discussion: This measurement provides a lower bound on the amount of
+   time during which SETUP messages will be forwarded along a sub-
+   optimal or blocked path.
+
+   Measurement Units: seconds
+
+2.2.5. ATM Service: ILMI
+
+2.2.5.1. MIB Alignment Time
+
+   Definition: The amount of time between the issuance of the final cold
+   start message and the final get response associated with the exchange
+   of static MIB information.
+
+   Discussion: This measurement reflects the amount of time required by
+   the switch and end system to exchange all information required to
+   characterize and align the capabilities of both systems.  It does not
+   include address registration.  It should also be noted that this
+   measurement will depend on the number of MIB elements implemented by
+   both systems.
+
+   Measurement Units: seconds
+
+2.2.5.2. Address Registration Time
+
+   Definition: The amount of time between the initial set request issued
+   by the switch and the final get response issued by the switch.
+
+   Discussion: This measurement assumes that the switch has checked the
+   network prefix status object and the end system has checked the ATM
+   address status object.  In the case where the end system checks the
+   ATM address status object only after the switch has issued a set
+   request of the network prefix status object, this measurement will
+   not reflect the actual time required to complete the address
+   registration.
+
+   Measurement Units: seconds
+
+
+
+Dunn & Martin                Informational                     [Page 29]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+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
+
+   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. 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.
+
+
+
+
+Dunn & Martin                Informational                     [Page 30]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+   [I.321]        ITU-T, B-ISDN protocol reference model and its
+                  application, April 1991.
+
+   [I.363]        ITU-T, B-ISDN ATM Adaptation Layer Specification
+                  series, 1996-1997.
+
+   [I.363.5]      ITU-T, B-ISDN ATM Adaptation Layer Specification: Type
+                  5 AAL, August 1996.
+
+6. Editors' Addresses
+
+   Jeffrey Dunn
+   Advanced Network Consultants, Inc.
+   4214 Crest Place
+   Ellicott City, MD 21043 USA
+
+   Phone: +1 (410) 750-1700
+   EMail: Jeffrey.Dunn@worldnet.att.net
+
+
+   Cynthia Martin
+   Advanced Network Consultants, Inc.
+   11241-B Skilift Court
+   Columbia, MD 21044 USA
+
+   Phone: +1 (410) 730-6300
+   EMail: Cynthia.E.Martin@worldnet.att.net
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 31]
+
+RFC 2761            Terminology for ATM Benchmarking       February 2000
+
+
+7.  Full Copyright Statement
+
+   Copyright (C) The Internet Society (2000).  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 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.
+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Dunn & Martin                Informational                     [Page 32]
+