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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT Call/Cell Benchmarking Terminology October 1998 4 Network Working Group J. H. Dunn 5 INTERNET-DRAFT Hewlett-Packard 6 Expires in six months C. E. Martin 7 Hewlett-Packard 9 October 1998 11 Terminology for Call/Cell Benchmarking 12 14 Status of this Memo 15 This document is an Internet-Draft. Internet-Drafts are working 16 documents of the Internet Engineering Task Force (IETF), its areas, 17 and its working groups. Note that other groups may also distribute 18 working documents as Internet-Drafts. 20 Internet-Drafts are draft documents valid for a maximum of six months 21 and may be updated, replaced, or obsoleted by other documents at any 22 time. It is inappropriate to use Internet-Drafts as reference material or 23 to cite them other than as ``work in progress.'' 25 To view the entire list of current Internet-Drafts, please check the "1id- 26 abstracts.txt" listing contained in the Internet-Drafts Shadow 27 Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), 28 ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), 29 ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). 31 Abstract 33 This memo discusses and defines terms associated with performance 34 benchmarking tests and the results of these tests in the context of cell- 35 based and call-based switching devices. The terms defined in this 36 memo will be used in addition to terms defined in RFCs 1242, 1944 37 and 2285. This memo is a product of the Benchmarking Methodology 38 Working Group (BMWG) of the Internet Engineering Task Force 39 (IETF). 41 I. Background 43 1. Introduction. This document provides terminology for 44 benchmarking cell-based and call-based switching devices. It extends 45 terminology already defined for benchmarking network interconnect 46 devices in RFCs 1242, 1944 and 2285 . Although some of the 47 definitions in this memo may be applicable to a broader group of 48 network interconnect devices, the primary focus of the terminology in 49 this memo is on cell-based and call-based switches. Specifically, this 50 includes Asynchronous Transfer Mode (ATM) cell relay and signaling 51 and Frame Relay (FR) signaling. 53 This memo contains two major sections: Background and Definitions. 54 Within the definitions section is a formal definitions subsection, 55 provided as a courtesy to the reader, and a measurement definitions 56 sub-section, which contains performance metrics with inherent units. 58 The BMWG produces two major classes of documents: Benchmarking 59 Terminology documents and Benchmarking Methodology documents. 60 The Terminology documents present the benchmarks and other related 61 terms. The Methodology documents define the procedures required to 62 collect the benchmarks cited in the corresponding Terminology 63 documents. 65 2. Existing Definitions 67 RFC 1242 "Benchmarking Terminology for Network Interconnect 68 Devices" should be consulted before attempting to make use of this 69 document. RFC 1944 "Benchmarking Methodology for Network 70 Interconnect Devices" contains discussions of a number of terms 71 relevant to the benchmarking of switching devices and should also be 72 consulted. RFC 2285 "Benchmarking Terminology for LAN 73 Switching Devices" contains a number of terms pertaining to traffic 74 distributions and datagram interarrival. For the sake of clarity and 75 continuity this RFC adopts the template for definitions set out in 76 Section 2 of RFC 1242. Definitions are indexed and grouped together 77 in sections for ease of reference. The key words "MUST", "MUST 78 NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", 79 "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" 80 in this document are to be interpreted as described in RFC 2119. 82 II. Definitions 84 The definitions presented in this section have been divided into two 85 groups. The first group is formal definitions, which are required in the 86 definitions of the performance metrics but are not themselves strictly 87 metrics. These definitions are subsumed from other work done in 88 other working groups both inside and outside the IETF. They are 89 provided as a courtesy to the reader. 91 1. Formal Definitions 93 1.1. Definition Format (from RFC1242) 95 Term to be defined. 97 Definition: The specific definition for the term. 99 Discussion: A brief discussion of the term, its application and any 100 restrictions on measurement procedures. 102 Specification: The working group and document in which the term is 103 specified. Listed in the references. 105 1.2. ATM Related Definitions. 107 1.2.1. Allowed Cell Rate (ACR): 109 Definition: An ABR service parameter, ACR is the current rate 110 (cells/second) at which a source is allowed to send. 112 Discussion: 114 Specification: AF-TM4.0 116 1.2.2. ACR Decrease Time Factor (ADTF): 118 Definition: This is the time permitted between sending RM-cells 119 before the rate is decreased to ICR (Initial Cell Rate). The time units 120 are: 121 .01 to 10.23 seconds 122 with a granularity of 10 ms. 124 Discussion: 126 Specification: AF-TM4.0 128 1.2.3. Additive Increase Rate (AIR): 130 Definition: An ABR service parameter, AIR controls the rate at which 131 the cell transmission rate increases. It is signaled as AIRF, where 132 AIRF = AIR*Nrm/PCR. 134 Discussion: 136 Specification: AF-TM4.0 138 1.2.4. Additive Increase Rate Factor (AIRF): 140 Definition: Refer to AIR. 142 Discussion: 144 Specification: AF-TM4.0 146 1.2.5. ATM Adaptation Layer (AAL): 148 Definition: The layer in the B-ISDN reference model (see B-ISDN) 149 which adapts higher layer PDUs into the ATM layer. 151 Discussion: There are 4 types of adaptation layers: 152 - AAL1: used for circuit emulation, voice over ATM 153 - AAL2: used for sub-rated voice over ATM 154 - AAL3/4: used for data over noisy ATM lines 155 - AAL5: used for data over ATM, most widely used AAL type 156 These AAL types are not measurements, but it is possible to measure 157 the time required for Segmentation and Reassembly (SAR). 159 Specification: AF-UNI3.1 161 1.2.6. ATM Adaptation Layer Type 5 (AAL5): 163 Definition: AAL5 functions in support of variable bit rate, delay- 164 tolerant data traffic requiring minimal sequencing or error detection 165 support. 167 Discussion: AAL5 is the adaptation layer for UNI signaling, ILMI, 168 PNNI signaling, and for IP PDU�s. It is the most widely used AAL 169 type to date. 171 Specification: AF-UNI3.1 173 1.2.7. Available Bit Rate (ABR): 175 Definition: ABR is an ATM layer service category for which the 176 limiting ATM layer transfer characteristics provided by the network 177 may change subsequent to connection establishment. A flow control 178 mechanism is specified which supports several types of feedback to 179 control the source rate in response to changing ATM layer transfer 180 characteristics. 182 Discussion: It is expected that an end-system that adapts its traffic in 183 accordance with the feedback will experience a low cell loss ratio and 184 obtain a fair share of the available bandwidth according to a network 185 specific allocation policy. Cell delay variation is not controlled in this 186 service, although admitted cells are not delayed unnecessarily. 188 Specification: AF-TM4.0 190 1.2.8. Asynchronous Transfer Mode (ATM) 192 Definition: A transfer mode in which the information is organized into 193 53 octet PDUs called cells. It is asynchronous in the sense that the 194 recurrence of cells containing information from an individual user is 195 not necessarily periodic. 197 Discussion: ATM is based on the ISDN model. 199 Specification: AF-UNI3.1 201 1.2.9. ATM Link: 203 Definition: A virtual path link (VPL) or a virtual channel link (VCL). 205 Discussion: none. 207 Specification: AF-UNI3.1 209 1.2.10. ATM Peer-to-Peer Connection: 211 Definition: A virtual channel connection (VCC) or a virtual path 212 connection (VPC). 214 Discussion: none. 216 Specification: AF-UNI3.1 218 1.2.11. ATM Traffic Descriptor: 220 Definition: A generic list of traffic parameters, which specify the 221 intrinsic traffic characteristics of a requested ATM connection. See 222 GCRA. 224 Discussion: 226 Specification: AF-UNI3.1 228 1.2.12. ATM User-User Connection: 230 Definition: An association established by the ATM Layer to support 231 communication between two or more ATM service users (i.e., between 232 two or more next higher entities or between two or more ATM- 233 entities). The communications over an ATM Layer connection may be 234 either bi-directional or unidirectional. The same Virtual Channel 235 Identifier (VCI) issued for both directions of a connection at an 236 interface. 238 Discussion: none. 240 Specification: AF-UNI3.1 242 1.2.13. Backward Explicit Congestion Notification (BECN): 244 Definition: A Resource Management (RM) cell type generated by the 245 network or the destination, indicating congestion or approaching 246 congestion for traffic flowing in the direction opposite that of the 247 BECN cell. 249 Discussion: 251 Specification: AF-TM4.0 253 1.2.14. BECN Cell (BN): 255 Definition: A Resource Management (RM) cell type indicator. The 256 network or the destination may generate a Backwards Explicit 257 Congestion Notification (BECN) RM-cell. To do so, BN=1 is set, to 258 indicate the cell is not source-generated, and DIR=1 to indicate the 259 backward flow. Source generated RM-cells are initialized with BN=0. 261 Discussion: 263 Specification: AF-TM4.0 265 1.2.15. Broadband ISDN (B-ISDN) Model: 267 Definition: A layered service model that specifies the mapping of 268 higher layer protocols onto ATM and its underlying physical layer. 269 The model is composed of four layers: Physical, ATM, AAL and 270 Service. 272 Discussion: none. 274 Specification: AF-UNI3.1 276 1.2.16. Burst Tolerance (BT): 278 Definition: A traffic parameter, which, along with the Sustainable 279 Cell Rate (SCR), specifies the maximum number of cells which will be 280 accepted at the Peak Cell Rate (PCR) on an ATM connection. 282 Discussion: BT applies to ATM connections supporting VBR services 283 and is the limit parameter of the GCRA. 285 Specification: AF-TM4.0 286 1.2.17. Connection Admission Control (CAC): 288 Definition: Connection Admission Control is defined as the set of 289 actions taken by the network during the call set- up phase (or during 290 call re-negotiation phase) in order to determine whether a connection 291 request can be accepted or should be rejected (or whether a request for 292 re-allocation can be accommodated). 294 Discussion: none 296 Specification: AF-UNI3.1 298 1.2.18. Call: 300 Definition: A call is an association between two or more users or 301 between a user and a network entity that is established by the use of 302 network capabilities. This association may have zero or more 303 connections. 305 Discussion: none 307 Specification: AF-UNI3.1 309 1.2.19. Call-based 311 Definition: An association between two or more users or between a 312 user and a network entity that is established by the use of network 313 capabilities. This association may have zero or more connections. 315 Discussion: none 317 Specification: AF-UNI3.1 319 1.2.20. Constant Bit Rate (CBR): 321 Definition: An ATM service category which supports a constant or 322 guaranteed rate to transport services such as video or voice as well as 323 circuit emulation which requires rigorous timing control and 324 performance parameters. 326 Discussion: 328 Specification: AF-UNI3.1 330 1.2.21. Cell: 332 Definition: A unit of transmission in ATM. A fixed-size frame 333 consisting of a 5-octet header and a 48-octet payload. 335 Discussion: none. 337 Specification: AF-UNI3.1 339 1.2.22. Cell Header: 341 Definition: ATM Layer protocol control information. 343 Discussion: The ATM cell header is a 5-byte header that contains the 344 following fields: 345 - Generic Flow Control (GFC): 4 bits 346 - Virtual Path Identifier (VPI): 8 bits 347 - Virtual Channel Identifier (VCI): 16 bits 348 - Payload Type (PT): 3 bits 349 - Cell Loss Priority (CLP): 1 bit 350 - Header Error Check (HEC): 8 bit CRC computed over the 351 previous 4 octets 352 Each field is discussed in the ATM Specific definition section of this 353 document. 355 Specification: AF-UNI3.1 357 1.2.23. Congestion Indicator (CI): 359 Definition: This is a field in a RM-cell, and is used to cause the source 360 to decrease its ACR. The source sets CI=0 when it sends a RM-cell. 361 Setting CI=1 is typically how destinations indicate that Explicit 362 Forward Congestion Indication (EFCI) has been received on a previous 363 data cell. 365 Discussion: 367 Specification: AF-TM4.0 369 1.2.24. Cell Loss Priority (CLP): 371 Definition: This bit in the ATM cell header indicates two levels of 372 priority for ATM cells. CLP=0 cells are higher priority than CLP=1 373 cells. CLP=1 cells may be discarded during periods of congestion to 374 preserve the CLR of CLP=0 cells. 376 Discussion: The CLP bit is used to determine GCRA contract 377 compliance. 379 Specification: AF-UNI3.1 381 1.2.25. Connection: 383 Definition: An ATM connection consists of concatenation of ATM 384 Layer links in order to provide an end-to-end information transfer 385 capability to access points. 387 Discussion: none. 389 Specification: AF-UNI3.1 391 1.2.26. Cutoff Decrease Factor (CDF): 393 Definition: CDF controls the decrease in ACR (Allowed Cell Rate) 394 associated with CRM. 396 Discussion: 398 Specification: AF-TM4.0 400 1.2.27. Current Cell Rate (CCR): 402 Definition: The Current Cell Rate is an RM-cell field set by the source 403 to its current ACR when it generates a forward RM-cell. This field 404 may be used to facilitate the calculation of ER, and may not be 405 changed by network elements. CCR is formatted as a rate. 407 Discussion: 409 Specification: AF-TM4.0 411 1.2.28. Cyclic Redundancy Check (CRC): 413 Definition: A mathematical algorithm that computes a numerical value 414 based on the bits in a block of data. This number is transmitted with 415 the data and the receiver uses this information and the same algorithm 416 to insure the accurate delivery of data by comparing the results of 417 algorithm and the number received. If a mismatch occurs, an error in 418 transmission is presumed. 420 Discussion: CRC is not a measurement, but it is possible to measure 421 the amount of time to perform a CRC on a string of bits. This 422 measurement will not be addressed in this document. 424 Specification: AF-UNI3.1 426 1.2.29. DIR: 428 Definition: This is a field in a RM-cell, which indicates the direction 429 of the RM-cell with respect to the data flow with which it is associated. 430 The source sets DIR=0 and the destination sets DIR=1. 432 Discussion: none 433 Specification: AF-TM4.0 435 1.2.30. Explicit Forward Congestion Indication (EFCI): 437 Definition: EFCI is an indication in the PTI field of the ATM cell 438 header. A network element in an impending-congested state or a 439 congested state may set EFCI so that this indication may be examined 440 by the destination end-system. For example, the end- system may use 441 this indication to implement a protocol that adaptively lowers the cell 442 rate of the connection during congestion or impending congestion. A 443 network element that is not in a congestion state or an impending 444 congestion state will not modify the value of this indication. 445 Impending congestion is the state when network equipment is 446 operating around its engineered capacity level. 448 Discussion: 450 Specification: AF-TM4.0 452 1.2.31. Explicit Rate (ER): 454 Definition: The Explicit Rate is a RM-cell field used to limit the source 455 ACR to a specific value. It is initially set by the source to a requested 456 rate (such as PCR). It may be subsequently reduced by any network 457 element in the path to a value that the element can sustain. ER is 458 formatted as a rate. 460 Discussion: 462 Specification: AF-TM4.0 464 1.2.32. End System (ES): 466 Definition: A system where an ATM connection is terminated or 467 initiated. An originating end system initiates the ATM connection, and 468 terminating end system terminates the ATM connection. OAM cells 469 may be generated and received. 471 Discussion: An ES can be the user side of a UNI signaling interface. 473 Specification: AF-TEST 475 1.2.33. Generic Cell Rate Algorithm (GCRA): 477 Definition: The GCRA is used to define conformance with respect to 478 the traffic contract of the connection. For each cell arrival the GCRA 479 determines whether the cell conforms to the traffic contract. The UPC 480 function may implement the GCRA, or one or more equivalent 481 algorithms to enforce conformance. The GCRA is defined with two 482 parameters: the Increment (I) and the Limit (L). 484 Discussion: GCRA is not a measurement, but there are a number of 485 measurements that can be obtained using the GCRA and other 486 parameters. 488 Specification: AF-TM4.0 490 1.2.34. Generic Flow Control (GFC): 492 Definition: GFC is a field in the ATM header, which can be used to 493 provide local functions (e.g., flow control). It has local significance 494 only and the value encoded in the field is not carried end-to-end. 496 Discussion: none 498 Specification: AF-UNI3.1 500 1.2.35. Header Error Control (HEC): 502 Definition: A check character calculated using an 8 bit CRC computed 503 over the first 4 octets of the ATM cell header. This allows for single 504 bit error correction or multiple bit error detection. 506 Discussion: none 508 Specification: AF-UNI3.1 510 1.2.36. Initial Cell Rate (ICR): 512 Definition: An ABR service parameter, in cells/sec, that is the rate at 513 which a source should send initially and after an idle period. 515 Discussion: none 517 Specification: AF-TM4.0 519 1.2.37. Integrated Local Management Interface 521 Definition: A management protocol which uses SNMP carried on 522 AAL5 to provide ATM network devices with status and configuration 523 information concerning VPCs, VCCs, registered ATM addresses and 524 the capabilities of ATM interfaces. 526 Discussion: ILMI is a conditionally required portion of UNI3.1; 527 however, ILMI 4.0 has been issued as a separate specification. This 528 document will refer to ILMI 4.0. 530 Specification: ILMI4.0 531 1.2.38. Intermediate System (IS): 533 Definition: A system that provides forwarding functions or relaying 534 functions or both for a specific ATM connection. OAM cells may be 535 generated and received. 537 Discussion: An IS can be either the user or network side of a UNI 538 signaling interface, or the network side of a PNNI signaling interface. 540 Specification: AF-TEST 542 1.2.39. Leaky Bucket (LB): 544 Definition: Leaky Bucket is the term used as an analogous description 545 of the algorithm used for conformance checking of cell flows from a 546 user or network. See GCRA, UPC and NPC. The "leaking hole in the 547 bucket" applies to the sustained rate at which cells can be 548 accommodated, while the "bucket depth" applies to the tolerance to 549 cell bursting over a given time period. 551 Discussion: There are two types of LB algorithms- single and dual. 552 Single LB defines a PCR, dual LB defines a PCR and SCR. 554 Specification: AF-TM4.0 556 1.2.40. Maximum Cell Rate (MCR): 558 Definition: This is the maximum capacity usable by connections 559 belonging to the specified service category. 561 Discussion: none 563 Specification: AF-TM4.0 565 1.2.41. Maximum Burst Size (MBS): 567 Definition: In the signaling message, the Burst Tolerance (BT) is 568 conveyed through the MBS that is coded as a number of cells. The BT 569 together with the SCR and the GCRA determine the MBS that may be 570 transmitted at the peak rate and still is in conformance with the GCRA. 572 Discussion: none 574 Specification: AF-TM4.0 576 1.2.42. Minimum Cell Rate (MCR): 578 Definition: An ABR service traffic descriptor, in cells/sec, that is the 579 rate at which the source is always allowed to send. 581 Discussion: none 583 Specification: AF-TM4.0 585 1.2.43. Missing RM-Cell Count (CRM): 587 Definition: CRM limits the number of forward RM-cells that may be 588 sent in the absence of received backward RM-cells. 590 Discussion: 592 Specification: AF-TM4.0 594 1.2.44. Mrm: 596 Definition: An ABR service parameter that controls allocation of 597 bandwidth between forward RM-cells, backward RM-cells, and data 598 cells. 600 Discussion: none 602 Specification: AF-TM4.0 604 1.2.45. Nrm: 606 Definition: An ABR service parameter, Nrm is the maximum number 607 of cells a source may send for each forward RM-cell. 609 Discussion: none. 611 Specification: AF-TM4.0 613 1.2.46. Operations Administration and Maintenance (OAM): 615 Definition: A group of network management functions that provide 616 network fault indication, performance information, and data and 617 diagnosis functions. 619 Discussion: There are four types of ATM OAM flows: segment or 620 end-to-end VP termination management (i.e. F4 segment, F4 E2E) and 621 segment or end-to-end VC termination management (i.e. F5 segment, 622 F5 E2E). These OAM cells can be used to identify fault management, 623 connection verification, and loopback measurements. 625 Specification: AF-UNI3.1 627 1.2.47. Protocol Data Unit (PDU): 629 Definition: A PDU is a message of a given protocol comprising 630 payload and protocol-specific control information, typically contained 631 in a header. PDUs pass over the protocol interfaces that exist between 632 the layers of protocols (per OSI model). 634 Discussion: In ATM networks, a PDU can refer to an ATM cell, 635 multiple ATM cells, an AAL segment, an IP datagram and others. 637 Specification: 639 1.2.48. Private Network-Network Interface (PNNI): 641 Definition: A routing information protocol that enables extremely 642 scalable, full function, dynamic multi-vendor ATM switches to be 643 integrated in the same network. 645 Discussion: PNNI consists of signaling and routing between ATM 646 network devices. PNNI signaling is based on UNI 4.0 signaling 647 between two network side interfaces, while PNNI routing provides a 648 mechanism to route ATM cells between two separate, autonomous 649 ATM networks. 651 Specification: AF-PNNI1.0 653 1.2.49. Payload Type Indicator (PTI): 655 Definition: Payload Type Indicator is the Payload Type field value 656 distinguishing the various management cells and user cells. Example: 657 Resource Management cell has PTI=110, end-to-end OAM F5 Flow 658 cell has PTI=101. 660 Discussion: none. 662 Specification: AF-UNI3.1 664 1.2.50. Peak Cell Rate (PCR): 666 Definition: A traffic parameter, which specifies the upper bound on 667 the rate at which ATM cells can be submitted to an ATM connection. 668 This parameter is used by the GCRA. 670 Discussion: 672 Specification: AF-TM4.0 674 1.2.51. Permanent Virtual Circuit (PVC): 676 Definition: This is a link with static route defined in advance, usually 677 by manual setup. 679 Discussion: PVC�s are widely deployed in WAN ATM networks� 681 Specification: AF-UNI3.1 683 1.2.52. Permanent Virtual Channel Connection (PVCC): 685 Definition: A Virtual Channel Connection (VCC) is an ATM 686 connection where switching is performed on the VPI/VCI fields of 687 each cell. A Permanent VCC is one that is provisioned through some 688 network management function and left up indefinitely. 690 Discussion: none. 692 Specification: AF-UNI3.1 694 1.2.53. Permanent Virtual Path Connection: (PVPC): 696 Definition: A Virtual Path Connection (VPC) is an ATM connection 697 where switching is performed on the VPI field only of each cell. A 698 Permanent VPC is one that is provisioned through some network 699 management function and left up indefinitely. 701 Discussion: none. 703 Specification: AF-UNI3.1 705 1.2.54. Rate Decrease Factor (RDF): 707 Definition: An ABR service parameter, RDF controls the decrease in 708 the cell transmission rate. RDF is a power of 2 from 1/32,768 to 1. 710 Discussion: 712 Specification: AF-TM4.0 714 1.2.55. Rate Increase Factor (RIF): 716 Definition: This controls the amount by which the cell transmission 717 rate may increase upon receipt of a RM-cell. The additive increase 718 rate AIR=PCR*RIF. RIF is a power of 2, ranging from 1/32768 to 1. 720 Discussion: 722 Specification: AF-TM4.0 724 1.2.56. Resource Management (RM): 726 Definition: Resource Management is the management of critical 727 resources in an ATM network. Two critical resources are buffer space 728 and trunk bandwidth. Provisioning may be used to allocate network 729 resources in order to separate traffic flows according to service 730 characteristics. VPCs play a key role in resource management. By 731 reserving capacity on VPCs, the processing required to establish 732 individual VCCs is reduced. Refer to RM-cell. 734 Discussion: 736 Specification: AF-TM4.0 738 1.2.57. Resource Management Cell (RM-Cell): 740 Definition: Information about the state of the network like bandwidth 741 availability, state of congestion, and impending congestion, is 742 conveyed to the source through special control cells called Resource 743 Management Cells (RM-cells). 745 Discussion: 747 Specification: AF-TM4.0 749 1.2.58. Segmentation and Reassembly (SAR): 751 Definition: The process used by the AAL in the B-ISDN reference 752 model (see B-ISDN) which fragments higher layer PDUs into ATM 753 cells. 755 Discussion: SAR is not a measurement, but the speed in which SAR 756 can be completed on a bit stream can be measured. This measurement 757 will not be discussed in this document. 759 Specification: 761 1.2.59. Sustainable Cell Rate (SCR): 763 Definition: The SCR is an upper bound on the conforming average rate 764 of an ATM connection over time scales which are long relative to 765 those for which the PCR is defined. Enforcement of this bound by the 766 UPC could allow the network to allocate sufficient resources, but less 767 than those based on the PCR, and still ensure that the performance 768 objectives (e.g., for Cell Loss Ratio) can be achieved. 770 Discussion: 772 Specification: AF-TM4.0 774 1.2.60. Switched Virtual Circuit (SVC): 776 Definition: A connection established via signaling. The user defines 777 the endpoints when the call is initiated. 779 Discussion: SVC�s are established using either UNI signaling or PNNI 780 signaling. The signaling mechanism follows a specific state 781 machine� 783 Specification: AF-UNI3.1 785 1.2.61. Switched Virtual Channel Connection (SVCC): 787 Definition: A Switched VCC is one that is established and taken down 788 dynamically through control signaling. A Virtual Channel Connection 789 (VCC) is an ATM connection where switching is performed on the 790 VPI/VCI fields of each cell. 792 Discussion: none. 794 Specification: AF-UNI3.1 796 1.2.62. Switched Virtual Path Connection (SVPC): 798 Definition: A Switched Virtual Path Connection is one that is 799 established and taken down dynamically through control signaling. A 800 Virtual Path Connection (VPC) is an ATM connection where 801 switching is performed on the VPI field only of each cell. 803 Discussion: none. 805 Specification: AF-UNI3.1 807 1.2.63. Switched Connection: 809 Definition: A connection established via signaling. 811 Discussion: none. 813 Specification: AF-UNI3.1 815 1.2.64. Tagged Cell Rate (TCR): 817 Definition: An ABR service parameter, TCR limits the rate at which a 818 source may send out-of-rate forward RM-cells. TCR is a constant 819 fixed at 10 cells/second. 821 Discussion: 823 Specification: AF-TM4.0 824 1.2.65. Traffic Contract 826 Definition: A specification of the negotiated traffic characteristics of 827 an ATM connection. 829 Discussion: 831 Specification: AF-TM4.0 833 1.2.66. Transmission Convergence (TC): 835 Definition: A sub-layer of the physical layer of the B-ISDN model 836 transforms the flow of cells into a steady flow of bits and bytes for 837 transmission over the physical medium. On transmit, the TC sublayer 838 maps the cells to the frame format, generates the Header Error Check 839 (HEC), and sends idle cells when the ATM layer has none to send. On 840 reception, the TC sublayer delineates individual cells in the received 841 bit stream, and uses the HEC to detect and correct received errors. 843 Discussion: TC is not a measurement, but the speed in which TC can 844 occur on a bit stream can be measured. This measurement will not be 845 discussed in this document. 847 Specification: AF-UNI3.1 849 1.2.67. TDF: 851 Definition: An ABR service parameter, TDF controls the decrease in 852 ACR associated with TOF. TDF is signaled as TDFF, where TDF = 853 TDFF/RDF times the smallest power of 2 greater or equal to PCR. 854 TDF is in units of 1/seconds. 856 Discussion: 858 Specification: AF-TM4.0 860 1.2.68. TDFF. 862 Definition: Refer to TDF. TDFF is either zero or a power of two in 863 the range 1/64 to 1 in units of 1/cells. 865 Discussion: 867 Specification: AF-TM4.0 869 1.2.69. Traffic Management (TM): 871 Definition: Traffic Management is the aspect of the traffic control 872 and congestion control procedures for ATM. ATM layer traffic 873 control refers to the set of actions taken by the network to avoid 874 congestion conditions. ATM layer congestion control refers to the set 875 of actions taken by the network to minimize the intensity, spread and 876 duration of congestion. The following functions form a framework for 877 managing and controlling traffic and congestion in ATM networks and 878 may be used in appropriate combinations. 879 o Connection Admission Control 880 o Feedback Control 881 o Usage Parameter Control 882 o Priority Control 883 o Traffic Shaping 884 o Network Resource Management 885 o Frame Discard 886 o ABR Flow Control 888 Discussion: 890 Specification: AF-TM4.0 892 1.2.70. Time Out Factor (TOF): 894 Definition: An ABR service parameter, TOF controls the maximum 895 time permitted between sending forward RM-cells before a rate 896 decrease is required. It is signaled as TOFF where TOF=TOFF+1. 897 TOFF is a power of 2 in the range: 1/8 to 4,096. 899 Discussion: 901 Specification: AF-TM4.0 903 1.2.71. Time Out Factor (TOFF): 905 Definition: Refer to TOF. 907 Discussion: none 909 Specification: AF-TM4.0 911 1.2.72. Trm. 913 Definition: An ABR service parameter that provides an upper bound 914 on the time between forward RM-cells for an active source. It is 100 915 times a power of two with a range of 100*2-7 to 100*20 917 Discussion: 919 Specification: AF-TM4.0 920 1.2.73. Traffic Shaping (TS): 922 Definition: Traffic Shaping is a mechanism that alters the traffic 923 characteristics of a stream of cells on a connection to achieve better 924 network efficiency, while meeting the QoS objectives, or to ensure 925 conformance at a subsequent interface. Traffic shaping must maintain 926 cell sequence integrity on a connection. Shaping modifies traffic 927 characteristics of a cell flow with the consequence of increasing the 928 mean Cell Transfer Delay. 930 Discussion: 932 Specification: AF-UNI3.1 934 1.2.74. Unspecified Bit Rate (UBR): 936 Definition: UBR is an ATM service category, which does not specify 937 traffic related service guarantees. Specifically, UBR does not include 938 the notion of a per-connection negotiated bandwidth. No numerical 939 commitments are made with respect to the cell loss ratio experienced 940 by a UBR connection, or as to the cell transfer delay experienced by 941 cells on the connection. 943 Discussion: UBR is used with � traffic type� 945 Specification: AF-TM4.0 947 1.2.75. User-Network Interface (UNI): 949 Definition: An interface point between ATM end users and a private 950 ATM switch, or between a private ATM switch and the public carrier 951 ATM network; defined by physical and protocol specifications per 952 ATM Forum UNI documents. The standard adopted by the ATM 953 Forum to define connections between users or end stations and a local 954 switch. 956 Discussion: 958 Specification: AF-UNI3.1 960 1.2.76. Usage Parameter Control (UPC): 962 Definition: Usage Parameter Control is defined as the set of actions 963 taken by the network to monitor and control traffic, in terms of traffic 964 offered and validity of the ATM connection, at the end-system access. 965 Its main purpose is to protect network resources from malicious as well 966 as unintentional misbehavior, which can affect the QoS of other 967 already established connections, by detecting violations of negotiated 968 parameters and taking appropriate actions. 970 Discussion: 972 Specification: AF-TM4.0 974 1.2.77. Variable Bit Rate (VBR): 976 Definition: An ATM Forum defined service category which supports 977 variable bit rate data traffic with average and peak traffic parameters. 979 Discussion: 981 Specification: AF-TM4.0 983 1.2.78. VC: 985 Definition: A communications channel that provides for the sequential 986 unidirectional transport of ATM cells. 988 Discussion: 990 Specification: AF-UNI3.1 992 1.2.79. Virtual Channel Connection (VCC): 994 Definition: A concatenation of VCIs that extends between the points 995 where the ATM service users access the ATM layer. The points at 996 which the ATM cell payload is passed to, or received from, the users 997 of the ATM Layer (i.e., a higher layer or ATM-entity) for processing 998 signify the endpoints of a VCC. VCCs are unidirectional. 1000 Discussion: 1002 Specification: AF-UNI3.1 1004 1.2.80. Virtual Channel Identifier (VCI): 1006 Definition: A unique numerical tag as defined by a 16 bit field in the 1007 ATM cell header that identifies a virtual channel, over which the cell is 1008 to travel. 1010 Discussion: 1012 Specification: AF-UNI3.1 1014 1.2.81. Virtual Path (VP): 1016 Definition: A unidirectional logical association or bundle of VCs. 1018 Discussion: 1020 Specification: AF-UNI3.1 1022 1.2.82. Virtual Path Connection (VPC): 1024 Definition: A concatenation of VPIs between Virtual Path Terminators 1025 (VPTs). VPCs are unidirectional 1027 Discussion: 1029 Specification: AF-UNI3.1 1031 1.2.83. Virtual Path Identifier (VPI): 1033 Definition: An eight-bit field in the ATM cell header that indicates the 1034 virtual path over which the cell should be routed. 1036 Discussion: 1038 Specification: AF-UNI3.1 1040 1.2.84. Virtual Source/Virtual Destination (VS/VD): 1042 Definition: An ABR connection may be divided into two or more 1043 separately controlled ABR segments. Each ABR control segment, 1044 except the first, is sourced by a virtual source. A virtual source 1045 implements the behavior of an ABR source endpoint. Backward RM- 1046 cells received by a virtual source are removed from the connection. 1047 Each ABR control segment, except the last, is terminated by a virtual 1048 destination. A virtual destination assumes the behavior of an ABR 1049 destination endpoint. Forward RM-cells received by a virtual 1050 destination are turned around and not forwarded to the next segment of 1051 the connection. 1053 Discussion: 1055 Specification: AF-TM4.0 1057 1.2.85. Xrm Decrease Factor (XDM): 1059 Definition: An ABR service parameter, XDF controls the decrease in 1060 ACR associated with Xrm. It is a power of two in range: [0, 1]. 1062 Discussion: 1064 Specification: AF-TM4.0 1066 1.2.86. Xrm: 1068 Definition: An ABR service parameter, Xrm limits the number of 1069 forward RM-cells which may be sent in the absence of received 1070 backward RM-cells. The range is 0-255. 1072 Discussion: 1074 Specification: AF-TM4.0 1076 1.3. Frame Relay Related Definitions 1078 1.3.1. Backward Explicit Congestion Notification (BECN): 1080 Definition: BECN is a bit in the frame relay header. The bit is set by a 1081 congested network node in any frame that is traveling in the reverse 1082 direction of the congestion. 1084 Discussion: 1086 Specification: FRF 1088 1.3.2. Committed Information Rate (CIR): 1090 Definition: CIR is the transport speed the frame relay network will 1091 maintain between service locations when data is presented. 1093 Discussion: 1095 Specification: FRF 1097 1.3.3. Discard Eligible: 1099 Definition: This is a 1-bit field in a frame relay header that provides a 1100 two level priority indicator, used to bias discard frames in the event of 1101 congestion toward lower priority frames. Similar to the CLP bit in 1102 ATM. 1104 Discussion: 1106 Specification: FRF 1108 1.3.4. Forward Explicit Congestion Notification (FECN): 1110 Definition: FECN is a bit in the frame relay header. The bit is set by a 1111 congested network node in any frame that is traveling in the same 1112 direction of the congestion. 1114 Discussion: 1116 Specification: FRF 1117 1.3.5. Frame: 1119 Definition: A logical grouping of information sent as a link-layer unit 1120 over a transmission medium. 1122 Discussion: 1124 Specification: FRF 1126 1.3.6. Frame Relay: 1128 Definition: A high-performance interface for packet-switching 1129 networks; considered more efficient that X.25. Frame relay 1130 technology can handle "bursty" communications that have rapidly 1131 changing bandwidth requirements. 1133 Discussion: 1135 Specification: FRF 1137 2. Performance Metrics 1139 2.1. Definition Format (from RFC1242) 1141 Metric to be defined. 1143 Definition: The specific definition for the metric. 1145 Discussion: A brief discussion of the metric, its application and any 1146 restrictions on measurement procedures. 1148 Measurement units: Intrinsic units used to quantify this metric. This 1149 includes subsidiary units, e.g. microseconds are acceptable if the 1150 intrinsic unit is seconds. 1152 2.2 Definitions 1154 2.2.1. Cell Delay Variation (CDV): 1156 Definition: The variation in cell transfer delay associated with a given 1157 traffic load, orientation and distribution, as well as an integration 1158 period. CDV = max(CTD) - min(CTD) where max and min indicate 1159 the maximum and minimum over the integration period, respectively. 1161 Discussion: CDV is a component of cell transfer delay, induced by 1162 buffering and cell scheduling. Peak-to-peak CDV is a QoS delay 1163 parameter associated with CBR and VBR services. The peak-to-peak 1164 CDV is the ((1-a) quantile of the CTD) minus the fixed CTD that 1165 could be experienced by any delivered cell on a connection during the 1166 entire connection holding time. The parameter "a" is the probability of 1167 a cell arriving late. 1169 Measurement Units: seconds 1171 2.2.2. Cell Delay Variation Tolerance (CDVT): 1173 Definition: ATM layer functions may alter the traffic characteristics of 1174 ATM connections by introducing Cell Delay Variation. When cells 1175 from two or more ATM connections are multiplexed, cells of a given 1176 ATM connection may be delayed while cells of another ATM 1177 connection are being inserted at the output of the multiplexer. 1178 Similarly, some cells may be delayed while physical layer overhead or 1179 OAM cells are inserted. Consequently, some randomness may affect 1180 the inter-arrival time between consecutive cells of a connection as 1181 monitored at the UNI. The upper bound on the "clumping" measure is 1182 the CDVT. 1184 Discussion: 1186 Measurement units: seconds 1188 2.2.3. Cell Error Ratio (CER): 1190 Definition: The ratio of errored cells in a transmission in relation to 1191 the total cells sent in a transmission associated with a given traffic 1192 load, orientation and distribution, as well as an integration period. 1193 CER = Errored Cells / Total Cells Transmitted. 1195 Discussion: The measurement is taken over a time interval and is 1196 desirable to be measured on an in-service circuit. 1198 Measurement Units: dimensionless. 1200 2.2.4. Cell Loss Ratio (CLR): 1202 Definition: The ratio of lost cells in a transmission in relation to the 1203 total cells sent in a transmission associated with a given traffic load, 1204 orientation and distribution, as well as an integration period. CLR = 1205 Lost Cells / Total Cells Transmitted. 1207 Discussion: CLR is a negotiated QoS parameter and acceptable values 1208 are network specific. The objective is to minimize CLR provided the 1209 end-system adapts the traffic to the changing ATM layer transfer 1210 characteristics. The CLR parameter is the value of CLR that the 1211 network agrees to offer as an objective over the lifetime of the 1212 connection. It is expressed as an order of magnitude, having a range of 1213 10-1 to 10-15 and unspecified. 1215 Measurement Units: dimensionless. 1217 2.2.5. Cell Misinsertion Rate (CMR): 1219 Definition: The ratio of cells received at an endpoint that were not 1220 originally transmitted by the source end in relation to the total number 1221 of cells properly transmitted associated with a given traffic load, 1222 orientation and distribution, as well as an integration period. CMR = 1223 Mis-inserted Cells / Total Cells Transmitted. 1225 Discussion: none 1227 Measurement Units: dimensionless. 1229 2.2.6. Cell Rate Margin (CRM): 1231 Definition: This is a measure of the difference between the effective 1232 bandwidth allocation and the allocation for sustainable rate in cells per 1233 second. 1235 Discussion: 1237 Measurement units: Cells per second 1239 2.2.7. CRC Error Ratio: 1241 Definition: The ratio of PDUs received at an endpoint that which 1242 contain an invalid CRC in relation to the total number of cells properly 1243 transmitted associated with a given traffic load, orientation and 1244 distribution, as well as an integration period. 1246 Discussion 1248 Measurement Units: dimensionless 1250 2.2.8. Cell Transfer Delay (CTD): 1252 Definition: The elapsed time between a cell exit event at the 1253 measurement point 1 (e.g., at the source UNI) and the corresponding 1254 cell entry event at a measurement point 2 (e.g., the destination UNI) 1255 for a particular connection. 1257 Discussion: The cell transfer delay between two measurement points is 1258 the sum of the total inter-ATM node transmission delay and the total 1259 ATM node processing delay. 1261 Measurement units: seconds 1262 3. Security Considerations. 1263 As this document is solely for the purpose of providing terminology 1264 and describes neither a protocol nor an implementation, there are no 1265 security considerations associated with this document. 1267 4. References 1268 [ILMI4.0] ATM Forum Integrated Local Management Interface 1269 Version 4.0, af-ilmi-0065.000, September 1996. 1270 [AF-TEST] Introduction to ATM Forum Test Specifications, af-test- 1271 0022.00, December 1994. 1272 [AF-TM4.0] ATM Forum, Traffic Management Specification Version 1273 4.0, af-tm-0056.00, April 1996. 1274 [AF-UNI3.1] ATM Forum, User Network Interface Specification 1275 Version 3.1, September 1994. 1277 5. Editor's Addresses 1278 Jeffrey Dunn 1279 Hewlett-Packard 3701 Koppers St. Baltimore, MD 21227 USA 1280 Phone: +1 (410) 362-7612 E-mail: jeff_dunn@hp.com 1282 Cynthia Martin 1283 Hewlett-Packard 3701 Koppers St. Baltimore, MD 21227 USA 1284 Phone +1 (410) 362-7631 E-mail: cynthia_martin@hp.com