INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 Network Working Group J. H. Dunn INTERNET-DRAFT Hewlett-Packard Expires in six months C. E. Martin Hewlett-Packard October 1998 Terminology for Call/Cell Benchmarking <draft-ietf-bmwg-call-03.txt> Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress.'' To view the entire list of current Internet-Drafts, please check the "1id- abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Abstract This memo discusses and defines terms associated with performance benchmarking tests and the results of these tests in the context of cell- based and call-based switching devices. The terms defined in this memo will be used in addition to terms defined in RFCs 1242, 1944 and 2285. This memo is a product of the Benchmarking Methodology Working Group (BMWG) of the Internet Engineering Task Force (IETF). I. Background 1. Introduction. This document provides terminology for benchmarking cell-based and call-based switching devices. It extends terminology already defined for benchmarking network interconnect devices in RFCs 1242, 1944 and 2285 . Although some of the definitions in this memo may be applicable to a broader group of network interconnect devices, the primary focus of the terminology in this memo is on cell-based and call-based switches. Specifically, this includes Asynchronous Transfer Mode (ATM) cell relay and signaling and Frame Relay (FR) signaling. Benchmarking Methodology Working Group Page 1 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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, which contains performance metrics with 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 RFC 1242 "Benchmarking Terminology for Network Interconnect Devices" should be consulted before attempting to make use of this document. RFC 1944 "Benchmarking Methodology for Network Interconnect Devices" contains discussions of a number of terms relevant to the benchmarking of switching devices and should also be consulted. RFC 2285 "Benchmarking Terminology for LAN Switching Devices" contains a number of terms pertaining to traffic distributions and datagram interarrival. For the sake of clarity and continuity this RFC adopts the template for definitions set out in Section 2 of RFC 1242. Definitions are indexed and grouped together in sections for ease of reference. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. II. Definitions The definitions presented in this section have been divided into two groups. The first group is formal definitions, which are required in the definitions of the performance metrics but are not themselves strictly metrics. These definitions are subsumed from other work done in other working groups both inside and outside the IETF. They are provided as a courtesy to the reader. 1. Formal Definitions 1.1. Definition Format (from RFC1242) Term to be defined. Definition: The specific definition for the term. Discussion: A brief discussion of the term, its application and any restrictions on measurement procedures. Benchmarking Methodology Working Group Page 2 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 Specification: The working group and document in which the term is specified. Listed in the references. 1.2. ATM Related Definitions. 1.2.1. Allowed Cell Rate (ACR): Definition: An ABR service parameter, ACR is the current rate (cells/second) at which a source is allowed to send. Discussion: 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): Benchmarking Methodology Working Group Page 3 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 limiting ATM layer transfer characteristics provided by the network may change subsequent to connection establishment. A flow control mechanism is specified which supports several types of feedback to control the source rate in response to changing ATM layer transfer characteristics. Discussion: It is expected that an end-system that adapts its traffic in accordance with the feedback will experience a low cell loss ratio and obtain a fair share of the available bandwidth according to a network specific allocation policy. Cell delay variation is not controlled in this service, although admitted cells are not delayed unnecessarily. Benchmarking Methodology Working Group Page 4 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 Specification: AF-TM4.0 1.2.8. 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. 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. Benchmarking Methodology Working Group Page 5 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 6 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 connections. Discussion: none Specification: AF-UNI3.1 1.2.19. Call-based Definition: An association between two or more users or between a user and a network entity that is established by the use of network capabilities. This association may have zero or more connections. Discussion: none Specification: AF-UNI3.1 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. Benchmarking Methodology Working Group Page 7 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 8 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 9 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 10 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 11 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 12 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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): Benchmarking Methodology Working Group Page 13 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 14 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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): Benchmarking Methodology Working Group Page 15 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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): Benchmarking Methodology Working Group Page 16 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 17 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 18 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 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 Benchmarking Methodology Working Group Page 19 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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. Benchmarking Methodology Working Group Page 20 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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: Benchmarking Methodology Working Group Page 21 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 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 Benchmarking Methodology Working Group Page 22 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 Benchmarking Methodology Working Group Page 23 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 2.1. Definition Format (from RFC1242) Metric to be defined. Definition: The specific definition for the metric. Discussion: A brief discussion of the metric, its application and any restrictions on measurement procedures. Measurement units: Intrinsic units used to quantify this metric. This includes subsidiary units, e.g. microseconds are acceptable if the intrinsic unit is seconds. 2.2 Definitions 2.2.1. Cell Delay Variation (CDV): Definition: The variation in cell transfer delay associated with a given traffic load, orientation and distribution, as well as an integration period. CDV = max(CTD) - min(CTD) where max and min indicate the maximum and minimum over the integration period, respectively. Discussion: CDV is a component of cell transfer delay, induced by buffering and cell scheduling. Peak-to-peak CDV is a QoS delay parameter associated with CBR and VBR services. The peak-to-peak CDV is the ((1-a) quantile of the CTD) minus the fixed CTD that Benchmarking Methodology Working Group Page 24 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 could be experienced by any delivered cell on a connection during the entire connection holding time. The parameter "a" is the probability of a cell arriving late. Measurement Units: seconds 2.2.2. 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: Measurement units: seconds 2.2.3. Cell Error Ratio (CER): Definition: The ratio of errored cells in a transmission in relation to the total cells sent in a transmission associated with a given traffic load, orientation and distribution, as well as an integration period. CER = Errored Cells / Total Cells Transmitted. Discussion: The measurement is taken over a time interval and is desirable to be measured on an in-service circuit. Measurement Units: dimensionless. 2.2.4. Cell Loss Ratio (CLR): Definition: The ratio of lost cells in a transmission in relation to the total cells sent in a transmission associated with a given traffic load, orientation and distribution, as well as an integration period. CLR = Lost Cells / Total Cells Transmitted. Discussion: CLR is a negotiated QoS parameter and acceptable values are network specific. The objective is to minimize CLR provided the end-system adapts the traffic to the changing ATM layer transfer characteristics. The CLR parameter is the value of CLR that the network agrees to offer as an objective over the lifetime of the connection. It is expressed as an order of magnitude, having a range of 10-1 to 10-15 and unspecified. Benchmarking Methodology Working Group Page 25 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 Measurement Units: dimensionless. 2.2.5. Cell Misinsertion Rate (CMR): Definition: The ratio of cells received at an endpoint that were not originally transmitted by the source end in relation to the total number of cells properly transmitted associated with a given traffic load, orientation and distribution, as well as an integration period. CMR = Mis-inserted Cells / Total Cells Transmitted. Discussion: none Measurement Units: dimensionless. 2.2.6. 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: 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 Benchmarking Methodology Working Group Page 26 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 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 4.0, af-tm-0056.00, April 1996. [AF-UNI3.1] ATM Forum, User Network Interface Specification Version 3.1, September 1994. 5. Editor's Addresses Jeffrey Dunn Hewlett-Packard 3701 Koppers St. Baltimore, MD 21227 USA Phone: +1 (410) 362-7612 E-mail: jeff_dunn@hp.com Cynthia Martin Hewlett-Packard 3701 Koppers St. Baltimore, MD 21227 USA Phone +1 (410) 362-7631 E-mail: cynthia_martin@hp.com Benchmarking Methodology Working Group Page 27