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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Missing reference section? '0' on line 1095 looks like a reference -- Missing reference section? '1' on line 1095 looks like a reference -- Missing reference section? 'AF-TEST-0022' on line 1336 looks like a reference Summary: 8 errors (**), 0 flaws (~~), 8 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. H. Dunn 3 INTERNET-DRAFT C. E. Martin 4 Expires: August, 1999 ANC, Inc. 6 February, 1999 7 Terminology for Call/Cell Benchmarking 8 10 Status of this Memo 12 This document is an Internet-Draft and is in full conformance with all 13 provisions of Section 10 of RFC2026. 15 Internet-Drafts are working documents of the Internet Engineering Task 16 Force (IETF), its areas, and its working groups. Note that other groups 17 may also distribute working documents as Internet-Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet- Drafts as reference material 22 or to cite them other than as "work in progress." 24 The list of current Internet-Drafts can be accessed at 25 http://www.ietf.org/ietf/1id-abstracts.txt 27 The list of Internet-Draft Shadow Directories can be accessed at 28 http://www.ietf.org/shadow.html. 30 Abstract 32 This memo discusses and defines terms associated with performance 33 benchmarking tests and the results of these tests in the context of 34 cell- based and call-based switching devices. The terms defined in this 35 memo will be used in addition to terms defined in RFCs 1242, 1944 and 36 2285. This memo is a product of the Benchmarking Methodology Working 37 Group (BMWG) of the Internet Engineering Task Force (IETF). 39 1. Introduction. 41 This document provides terminology for benchmarking cell-based and call- 42 based switching devices. It extends terminology already defined for 43 benchmarking network interconnect devices in RFC's 1242, 1944 and 2285. 44 Although some of the definitions in this memo may be applicable to a 45 broader group of network interconnect devices, the primary focus of the 46 terminology in this memo is on cell-based and call-based switches. 47 Specifically, this includes Asynchronous Transfer Mode (ATM) cell relay 48 and signaling. 50 This memo contains two major sections: Background and Definitions. 51 Within the definitions section is a formal definitions subsection, 52 provided as a courtesy to the reader, and a measurement definitions sub- 53 section, which contains performance metrics with inherent units. The 54 divisions of the measurement sub-section follow the BISDN model. 56 The BISDN model comprises four layers and two planes. This document 57 addresses the interactions between these layers and how they effect the 58 performance of IP, TCP, etc. A schematic of the model follows: 60 User Plane | Control Plane 61 Services | | ILMI | UNI, PNNI 62 ---------|--------------------------|-----------|--------------------- 63 AAL |AAL1, AAL2, AAL3/4, AAL5 | AAL5 | SAAL 64 ---------|--------------------------|-----------|--------------------- 65 ATM | Cell Relay | OAM, RM 66 ---------|--------------------------|--------------------------------- 67 | Convergence | 68 Physical |--------------------------|--------------------------------- 69 | Media | 70 ---------|--------------------------|--------------------------------- 72 This document assumes that necessary services are available and 73 active. 75 For example, IP connectivity requires SSCOP connectivity between 76 signaling entities. Further, it is assumed that the SUT has the 77 ability to configure ATM addresses (via hard coded addresses, ILMI 78 or PNNI neighbor discovery), has the ability to run SSCOP, and has 79 the ability to perform signaled call setups (via UNI or PNNI 80 signaling). Finally, this document presents only the terminology 81 associated with benchmarking IP performance over ATM; therefore, 82 it does not represent a total compilation of ATM test terminology. 84 The BMWG produces two major classes of documents: Benchmarking 85 Terminology documents and Benchmarking Methodology documents. The 86 Terminology documents present the benchmarks and other related 87 terms. The Methodology documents define the procedures required 88 to collect the benchmarks cited in the corresponding Terminology 89 documents. 91 2. Existing Definitions 93 RFC 1242 "Benchmarking Terminology for Network Interconnect Devices" 94 should be consulted before attempting to make use of this document. RFC 95 1944 "Benchmarking Methodology for Network Interconnect Devices" contains 96 discussions of a number of terms relevant to the benchmarking of switching 97 devices and should also be consulted. RFC 2285 "Benchmarking Terminology 98 for LAN Switching Devices" contains a number of terms pertaining to 99 traffic distributions and datagram interarrival. For the sake of clarity 100 and continuity this RFC adopts the template for definitions set out in 101 Section 2 of RFC 1242. Definitions are indexed and grouped together in 102 sections for ease of reference. The key words "MUST", "MUST NOT", 103 "REQUIRED", "SHALL, "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", 104 "MAY", and "OPTIONAL" go in this document are to be interpreted as 105 described in RFC 2119. 107 II. Definitions 109 The definitions presented in this section have been divided into two 110 groups. The first group is formal definitions, which are required in the 111 definitions of the performance metrics but are not themselves strictly 112 metrics. These definitions are subsumed from other work done in other 113 working groups both inside and outside the IETF. They are provided as a 114 courtesy to the reader. 116 Formal Definitions 118 1.1. Definition Format (from RFC 1242) 120 Term to be defined. 122 Definition: The specific definition for the term. 124 Discussion: A brief discussion of the term, its application and any 125 restrictions on measurement procedures. 127 Specification: The working group and document in which the term is 128 specified. Listed in the references. 130 1.2. Related Definitions. 132 1.2. 1. Allowed Cell Rate (ACR): 134 Definition: An ABR service parameter, ACR is the current rate 135 (cells/second) at which a source is allowed to send. 137 Discussion: For ABR traffic, ACR constitutes the actual data throughput 138 for a particular VC. The time change of this value effects TCP round trip 139 time calculations, which in turn effects TCP throughput. 141 Specification: AF-TM4.0 143 1.2.2. ACR Decrease Time Factor (ADTF): 145 Definition: This is the time permitted between sending RM-cells before the 146 rate is decreased to ICR (Initial Cell Rate). The time units are 147 .01 to 10.23 seconds 148 with a granularity of 10 ms. 150 Discussion: For ABR traffic, ADTF constitutes the time rate of the ACR. 151 This value effects TCP round trip time calculations, which in turn effects 152 TCP throughput. 154 Specification: AF-TM4.0 156 1.2.3. Additive Increase Rate (AIR): 158 Definition: An ABR service parameter, AIR controls the rate at which the 159 cell transmission rate increases. It is signaled as AIRF, where 160 AIRF = AIR*Nrm/PCR. 162 Discussion: For ABR traffic, AIR effects the time rate of change of the 163 ACR. This value effects TCP round trip time calculations, which in turn 164 effects TCP throughput. 166 Specification: AF-TM4.0 168 1.2.4. Additive Increase Rate Factor (AIRF): 170 Definition: Refer to AIR. 172 Discussion: Refer to AIR. 174 Specification: AF-TM4.0 176 1.2.5. ATM Adaptation Layer (AAL): 178 Definition: The layer in the B-ISDN reference model (see B-ISDN) which 179 adapts higher layer PDU's into the ATM layer. 181 Discussion: There are 4 types of adaptation layers: 182 AAL 1: used for circuit emulation, voice over ATM 183 AAL2: used for sub-rated voice over ATM 184 AAL3/4: used for data over noisy ATM lines 185 AAL5: used for data over ATM, most widely used AAL type 186 These AAL types are not measurements, but it is possible to measure the 187 time required for Segmentation and Reassembly (SAR). 189 Specification: AF-TM3.1 191 1.2.6. ATM Adaptation Layer Type 5 (AAL5): 193 Definition: AAL5 functions in support of variable bit rate, delay-tolerant 194 data traffic requiring minimal sequencing or error detection support. 196 Discussion: AAL5 is the adaptation layer for UNI signaling, ILMI, PNNI 197 signaling, and for IP PDU'S. It is the most widely used AAL type to date. 199 Specification: AF-UNI3.1 201 1.2.7. Available Bit Rate (ABR): 203 Definition: ABR is an ATM layer service category for which the limiting 204 ATM layer transfer characteristics provided by the network may change 205 subsequent to connection establishment. A flow control mechanism is 206 specified which supports several types of feedback to control the source 207 rate in response to changing ATM layer transfer characteristics. 209 Discussion: It is expected that an end-system that adapts its traffic in 210 accordance with the feedback will experience a low cell loss ratio and 211 obtain a fair share of the available bandwidth according to a network 212 specific allocation policy. Cell delay variation is not controlled in this 213 service, although admitted cells are not delayed unnecessarily. 215 Specification: AF-TM4.0 217 1.2.8. Asynchronous Transfer Mode (ATM) 219 Definition: A transfer mode in which the information is organized into 53 220 octet PDUs called cells. It is asynchronous in the sense that the 221 recurrence of cells containing information from an individual user is not 222 necessarily periodic. 224 Discussion: ATM is based on the ISDN model. 226 Specification: AF-UM3.1 228 1.2.9. ATM Link: 230 Definition: A virtual path link (VPL) or a virtual channel link (VCL). 232 Discussion: none. 234 Specification: AF-UNI3.1 236 1.2.10. ATM Peer-to-Peer Connection: 238 Definition: A virtual channel connection (VCC) or a virtual path 239 connection (VPC). 241 Discussion: none. 243 Specification: AF-UNI3.1 245 1.2.11. ATM Traffic Descriptor: 247 Definition: A generic list of traffic parameters, which specify the 248 intrinsic traffic characteristics of a requested ATM connection. See GCRA 249 and ABR. 251 Discussion: none. 253 Specification: AF-UNI3.1 255 1.2.12. ATM User-User Connection: 257 Definition: An association established by the ATM Layer to support 258 communication between two or more ATM service users (i.e., between two or 259 more next higher entities or between two or more ATM-entities). The 260 communications over an ATM Layer connection may be either bi-directional 261 or unidirectional. The same Virtual Channel Identifier (VCI) issued for 262 both directions of a connection at an interface. 264 Discussion: none. 266 Specification: AF-UNI3.1 268 1.2.13. Backward Explicit Congestion Notification (BECN): 270 Definition: A Resource Management (RM) cell type generated by the network 271 or the destination, indicating congestion or approaching congestion for 272 traffic flowing in the direction opposite that of the BECN cell. 274 Discussion: none. 276 Specification: AF-TM4.0 278 1.2.14. BECN Cell (BN): 280 Definition: A Resource Management (RM) cell type indicator. The network or 281 the destination may generate a Backwards Explicit Congestion Notification 282 (BECN) RM-cell. To do so, BN=l is set, to indicate the cell is not source- 283 generated, and DIR=1 to indicate the backward flow. Source generated RM- 284 cells are initialized with BN=O. 286 Discussion: none. 288 Specification: AF-TM4.0 290 1.2.15. Broadband ISDN (B-ISDN) Model: 292 Definition: A layered service model that specifies the mapping of higher 293 layer protocols onto ATM and its underlying physical layer. The model is 294 composed of four layers: Physical, ATM, AAL and Service. 296 Discussion: none. 298 Specification: AF-UNI3.1 300 1.2.16. Burst Tolerance (BT): 302 Definition: A traffic parameter, which, along with the Sustainable Cell 303 Rate (SCR), specifies the maximum number of cells which will be accepted 304 at the Peak Cell Rate (PCR) on an ATM connection. 306 Discussion: BT applies to ATM connections supporting VBR services and is 307 the limit parameter of the GCRA. 309 Specification: AF-TM4.0 311 1.2.17. Connection Admission Control (CAC): 313 Definition: Connection Admission Control is defined as the set of actions 314 taken by the network during the call set-up phase (or during call re- 315 negotiation phase) in order to determine whether a connection request can 316 be accepted or should be rejected (or whether a request for re-allocation 318 can be accommodated). 320 Discussion: none 322 Specification: AF-UNI3.1 324 1.2.18. Call: 326 Definition: A call is an association between two or more users or between 327 a user and a network entity that is established by the use of network 328 capabilities. This association may have zero or more connections. 330 Discussion: none 332 Specification: AF-UNI3.1 333 1.2.19. Call-based: 335 Definition: A transport requiring call setups- see CALL definition. 337 Discussion: none 339 Specification: AF-UNI3.1 341 1.2.20. Constant Bit Rate (CBR): 343 Definition: An ATM service category which supports a constant or 344 guaranteed rate to transport services such as video or voice as well as 345 circuit emulation which requires rigorous timing control and performance 346 parameters. 348 Discussion: CBR reduces problems associated with TCP performance and 349 throughput. ** 351 Specification: AF-UNI3.1 353 1.2.21. Cell: 355 Definition: A unit of transmission in ATM. A fixed-size frame consisting 356 of a 5-octet header and a 48-octet payload. 358 Discussion: none. 360 Specification: AF-UNI3.1 362 1.2.22. Cell Header: 364 Definition: ATM Layer protocol control information. 366 Discussion: The ATM cell header is a 5-byte header that contains the 367 following fields: 368 Generic Flow Control (GFC): 4 bits 369 Virtual Path Identifier (VPI): 8 bits 370 Virtual Channel Identifier (VCI): 16 bits 371 Payload Type (PT): 3 bits 372 Cell Loss Priority (CLP): 1 bit 373 Header Error Check (HEC): 8 bit CRC computed over the previous 4 octets 375 Each field is discussed in this document. 377 Specification: AF-UNI3.1 379 1.2.23. Congestion Indicator (CI): 381 Definition: This is a field in a RM-cell, and is used to cause the source 382 to decrease its ACR. The source sets CI=O when it sends a RM-cell. 383 Setting CI=1 is typically how destinations indicate that Explicit Forward 384 Congestion Indication (EFCI) has been received on a previous data cell. 386 Discussion: none. 388 Specification: AF-TM4.0 390 1.2.24. Cell Loss Priority (CLP): 392 Definition: This bit in the ATM cell header indicates two levels of 393 priority for ATM cells. CLP=0 cells are higher priority than CLP=1 cells. 394 CLP=1 cells may be discarded during periods of congestion to preserve the 395 CLR of CLP=0 cells. 397 Discussion: The CLP bit is used to determine GCRA contract compliance. 399 Specification: AF-UNI3.1 401 1.2.25. Connection: 403 Definition: An ATM connection consists of concatenation of ATM Layer links 404 in order to provide an end-to-end information transfer capability to 405 access points. 407 Discussion: none. 409 Specification: AF-UNI3.1 411 1.2.26. Cutoff Decrease Factor (CDF): 413 Definition: CDF controls the decrease in ACR (Allowed Cell Rate) 414 associated with CRM (missing RM cell count). 416 Discussion: For ABR traffic, CDF effects the time rate of change of the 417 ACR. This value effects TCP round trip time calculations, which in turn 418 effects TCP throughput. 420 Specification: AF-TM4.0 422 1.2.27. Current Cell Rate (CCR): 424 Definition: The Current Cell Rate is an RM-cell field set by the source to 425 its current ACR when it generates a forward RM-cell. This field may be 426 used to facilitate the calculation of ER, and may not be changed by 427 network elements. CCR is formatted as a rate. 429 Discussion: See actual cell rate. 431 Specification: AF-TM4.0 433 1.2.28. Cyclic Redundancy Check (CRC): 435 Definition: A mathematical algorithm that computes a numerical value based 436 on the bits in a block of data. This number is transmitted with the data 437 and the receiver uses this information and the same algorithm to insure 438 the accurate delivery of data by comparing the results of algorithm and 439 the number received. If a mismatch occurs, an error in transmission is 440 presumed. 442 Discussion: CRC is not a measurement, but it is possible to measure the 443 amount of time to perform a CRC on a string of bits. This measurement will 444 not be addressed in this document. 446 Specification: AF-UNI3.1 448 1.2.29. DIR: 450 Definition: This is a field in a RM-cell, which indicates the direction of 451 the RM-cell with respect to the data flow with which it is associated. 452 The source sets DIR=O and the destination sets DIR=1. 454 Discussion: none 456 Specification: AF-TM4.0 458 1.2.30. Explicit Forward Congestion Indication (EFCI): 460 Definition: EFCI is an indication in the PTI field of the ATM cell header. 461 A network element in an impending-congested state or a congested state may 462 set EFCI so that this indication may be examined by the destination end- 463 system. For example, the end-system may use this indication to implement a 464 protocol that adoptively lowers the cell rate of the connection during 465 congestion or impending congestion. A network element that is not in a 466 congestion state or an impending congestion state will not modify the 467 value of this indication. Impending congestion is the state when network 468 equipment is operating around its engineered capacity level. 470 Discussion: none. 472 Specification: AF-TM4.0 474 1.2.3 1. Explicit Rate (ER): 476 Definition: The Explicit Rate is a RM-cell field used to limit the source 477 ACR to a specific value. It is initially set by the source to a requested 478 rate (such as PCR). It may be subsequently reduced by any network element 479 in the path to a value that the element can sustain. ER is formatted as a 480 rate. 482 Discussion: For ABR traffic, ER effects the ACR. This value effects TCP 483 round trip time calculations, which in turn effects TCP throughput. 485 Specification: AF-TM4.0 487 1.2.32. End System (ES): 489 Definition: A system where an ATM connection is terminated or initiated. 490 An originating end system initiates the ATM connection, and terminating 491 end system terminates the ATM connection. OAM cells may be generated and 492 received. 494 Discussion: An ES can be the user side of a UNI signaling interface. 496 Specification: AF-TEST-0022 498 1.2.33. Generic Cell Rate Algorithm (GCRA): 500 Definition: The GCRA is used to define conformance with respect to the 501 traffic contract of the connection. For each cell arrival the GCRA 502 determines whether the cell conforms to the traffic contract. The UPC 503 function may implement the GCRA, or one or more equivalent algorithms to 504 enforce conformance. The GCRA is defined with two parameters: the 505 Increment (1) and the Limit (L). 507 Discussion: GCRA is not a measurement, but there are a number of 508 measurements that can be obtained using the GCRA and other parameters. 510 Specification: AF-TM4.0 512 1.2.34. Generic Flow Control (GFC): 514 Definition: GFC is a field in the ATM header, which can be used to provide 515 local functions (e.g., flow control). It has local significance only and 516 the value encoded in the field is not carried end-to-end. 518 Discussion: none 520 Specification: AF-UNI3.1 522 1.2.35. Header Error Control (HEC): 524 Definition: A check character calculated using an 8 bit CRC computed over 525 the first 4 octets of the ATM cell header. This allows for single bit 526 error correction or multiple bit error detection. 528 Discussion: none 530 Specification: AF-UNI3.1 532 1.2.36. Initial Cell Rate (ICR): 534 Definition: An ABR service parameter, in cells/sec, that is the rate at 535 which a source should send initially and after an idle period. 537 Discussion: none 539 Specification: AF-TM4.0 541 1.2.37. Integrated Local Management Interface 543 Definition: A management protocol which uses SNMPv1 carried on AAL5 to 544 provide ATM network devices with status and configuration information 545 concerning VPC's, VCC's, registered ATM addresses and the capabilities of 546 ATM interfaces. 548 Discussion: ILMI is a conditionally required portion of UNI3.1; however, 549 ILMI 4.0 has been issued as a separate specification. This document will 550 refer to ILMI 4.0. 552 Specification: AF-ILMI4.0 554 1.2.38. Intermediate System (IS): 556 Definition: A system that provides forwarding functions or relaying 557 functions or both for a specific ATM connection. OAM cells may be 558 generated and received. 560 Discussion: An IS can be either the user or network side of a UNI 561 signaling interface, or the network side of a PNNI signaling interface. 563 Specification: AF-TEST-0022 565 1.2.39. Leaky Bucket (LB): 567 Definition: Leaky Bucket is the term used as an analogous description of 568 the algorithm used for conformance checking of cell flows from a user or 569 network. See GCRA and UPC. The "leaking hole in the bucket" applies to 570 the sustained rate at which cells can be accommodated, while the "bucket 571 depth" applies to the tolerance to cell bursting over a given time period. 573 Discussion: There are two types of LB algorithms- single and dual. Single 574 LB defines a PCR; dual LB defines a PCR and SCR. 576 Specification: AF-TM4.0 578 1.2-40. Maximum Cell Rate (MCR): 580 Definition: This is the maximum capacity usable by connections belonging 581 to the specified service category. 583 Discussion: none 585 Specification: AF-TM4.0 587 1.2.41. Maximum Burst Size (MBS): 589 Definition: In the signaling message, the Burst Tolerance (BT) is conveyed 590 through the MBS that is coded as a number of cells. The BT together with 591 the SCR and the GCRA determine the MBS that may be transmitted at the peak 592 rate and still is in conformance with the GCRA. 594 Discussion: none 596 Specification: AF-TM4.0 598 1.2.42. Minimum Cell Rate (MCR): 600 Definition: An ABR service traffic descriptor, in cells/sec, that is the 601 rate at which the source is always allowed to send. 603 Discussion: none 605 Specification: AF-TM4.0 607 1.2.43. Missing RM-Cell Count (CRM): 609 Definition: CRM limits the number of forward RM-cells that may be sent in 610 the absence of received backward RM-cells. 612 Discussion: none. 614 Specification: AF-TM4.0 616 1.2.44. Mrm: 618 Definition: An ABR service parameter that controls allocation of bandwidth 619 between forward W-cells, backward RM-cells, and data cells. 621 Discussion: none 623 Specification: AF-TM4.0 625 1.2.45. Nrm: 627 Definition: An ABR service parameter, Nrm is the maximum number of cells a 628 source may send for each forward RM-cell. 630 Discussion: none. 632 Specification: AF-TM4.0 634 1.2.46. Operations, Administration, and Maintenance (OAM): 636 Definition: A group of network management functions that provide network 637 fault indication, performance information, and data and diagnosis 638 functions. 640 Discussion: There are four types of ATM OAM flows: segment or end-to-end 641 VP termination management (i.e. F4 segment, F4 E2E) and segment or end-to- 642 end VC termination management (i.e. F5 segment, F5 E2E). These OAM cells 643 can be used to identify fault management, connection verification, and 644 loopback measurements. 646 Specification: AF-UNI3.1 648 1.2.47. Protocol Data Unit (PDU): 650 Definition: A PDU is a message of a given protocol comprising payload and 651 protocol-specific control information, typically contained in a header. 652 PDU's pass over the protocol interfaces that exist between the layers of 653 protocols (per OSI model). 655 Discussion: In ATM networks, a PDU can refer to an ATM cell, multiple ATM 656 cells, an AAL segment, an IP datagram and others. 658 Specification: - 660 1.2.48. Private Network-Network Interface (PNNI): 662 Definition: A routing information protocol that enables extremely, 663 scalable, full function, dynamic multi-vendor ATM switches to be 664 integrated in the same network. 666 Discussion: PNNI consists of signaling and routing between ATM network 667 devices. PNNI signaling is based on UNI 4.0 signaling between two network 668 side interfaces, while PNNI routing provides a mechanism to route ATM 669 cells between two separate, autonomous ATM networks. 671 Specification: AF-PNNI1.0 673 1.2.49. Payload Type Indicator (PTI): 675 Definition: Payload Type Indicator is the Payload Type field value 676 distinguishing the various management cells and user cells. 677 Example: 678 Resource Management cell is indicated as PTI=110, 679 end-to-end OAM F5 Flow cell is indicated as PTI=101. 681 Discussion: none. 683 Specification: AF-UNI3.1 685 1.2-50. Peak Cell Rate (PCR): 687 Definition: A traffic parameter, which specifies the upper bound on the 688 rate at which ATM cells can be submitted to an ATM connection. This 689 parameter is used by the GCRA. 691 Discussion: none. 693 Specification: AF-TM4.0 695 1.2.5 1. Permanent Virtual Circuit (PVC): 697 Definition: This is a link with static route(s) defined in advance, 698 usually by manual setup. 700 Discussion: none. 702 Specification: AF-UNI3.1 704 1.2.52. Permanent Virtual Channel Connection (PVCC): 706 Definition: A Virtual Channel Connection (VCC) is an ATM connection where 707 switching is performed on the VPI/VCI fields of each cell. A permanent VCC 708 is one that is provisioned through some network management function and 709 left up indefinitely. 711 Discussion: none. 713 Specification: AF-UNI3.1 715 1.2.53. Permanent Virtual Path Connection: (PVPC): 717 Definition: A Virtual Path Connection (VPC) is an ATM connection where 718 switching is performed on the VPI field only of each cell. A permanent VPC 719 is one that is provisioned through some network management function and 720 left up indefinitely. 722 Discussion: none. 724 Specification: AF-UNI3.1 726 1.2.54. Rate Decrease Factor (RDF): 728 Definition: An ABR service parameter, RDF controls the decrease in the 729 cell transmission rate. RDF is a power of 2 from 1/32,768 to 1. 731 Discussion: For ABR traffic, RDF effects the time rate of change of the 732 ACR. This value effects TCP round trip time calculations, which in turn 733 effects TCP throughput. 735 Specification: AF-TM4.0 737 1.2.55. Rate Increase Factor (RIF): 739 Definition: This controls the amount by which the cell transmission rate 740 may increase upon receipt of a RM-cell. The additive increase rate 741 AIR=PCR*RIF. RIF is a power of 2, ranging from 1/32,768 to 1. 743 Discussion: For ABR traffic, RIF effects the time rate of change of the 744 ACR. This value effects TCP round trip time calculations, which in turn 745 effects TCP throughput. 747 Specification: AF-TM4.0 749 1.2.56. Resource Management (RM): 751 Definition: Resource Management is the management of critical resources in 752 an ATM network. Two critical resources are buffer space and trunk 753 bandwidth. Provisioning may be used to allocate network resources in order 754 to separate traffic flows according to service characteristics. VPC's play 755 a key role in resource management. By reserving capacity on VPCs, the 756 processing required to establish individual VCC's is reduced. Refer to RM- 757 cell. 759 Discussion: none. 761 Specification: AF-TM4.0 763 1.2.57. Resource Management Cell (RM-Cell): 765 Definition: Information about the state of the network like bandwidth 766 availability, state of congestion, and impending congestion, is conveyed 767 to the source through special control cells called Resource Management 768 Cells (RM-cells). 770 Discussion: none. 772 Specification: AF-TM4.0 774 1.2-58. Segmentation and Reassembly (SAR): 776 Definition: The process used by the AAL in the B-ISDN reference model (see 777 B-ISDN) which fragments higher layer PDU's into ATM cells. 779 Discussion: SAR is not a measurement, but the speed in which SAR can be 780 completed on a bit stream can be measured. This measurement will not be 781 discussed in this document. 783 Specification: AF-UNI3.1 785 1.2.59. Sustainable Cell Rate (SCR): 787 Definition: The SCR is an upper bound on the conforming average rate of an 788 ATM connection over time scales which are long relative to those for which 789 the PCR is defined. Enforcement of this bound by the UPC could allow the 790 network to allocate sufficient resources, but less than those based on the 791 PCR, and still ensure that the performance objectives (e.g., for Cell Loss 792 Ratio) can be achieved. 794 Discussion: none. 796 Specification: AF-TM4.0 798 1.2.60. Switched Virtual Circuit (SVC): 800 Definition: A connection established via signaling. The user defines the 801 endpoints when the call is initiated. 803 Discussion: SVC's are established using either UNI signaling or PNNI 804 signaling. The signaling state machine implements several timers, which 805 can effect the time required for call establishment. This will, in turn, 806 effect TCP round trip time calculation, effecting TCP throughput. 808 Specification: AF-UNI3.1, AF-UNI4.0, AF-PNNI1.0 810 1.2.61. Switched Virtual Channel Connection (SVCC): 812 Definition: A Switched VCC is one that is established and taken down 813 dynamically through control signaling. A Virtual Channel Connection (VCC) 814 is an ATM connection where switching is performed on the VPI/VCI fields of 815 each cell. 817 Discussion: none. 819 Specification: AF-UNI3.1 821 1.2.62. Switched Virtual Path Connection (SVPC): 823 Definition: A Switched Virtual Path Connection is one that is established 824 and taken down dynamically through control signaling. A Virtual Path 825 Connection (VPC) is an ATM connection where switching is performed on the 826 VPI field only of each cell. 828 Discussion: none. 830 Specification: AF-UNI3.1 832 1.2.63. Switched Connection: 834 Definition: A connection established via signaling. 836 Discussion: none. 838 Specification: AF-UNI3.1 840 1.2.64. Tagged Cell Rate (TCR): 842 Definition: An ABR service parameter, TCR limits the rate at which a 843 source may send out-of-rate forward RM-cells. TCR is a constant fixed at 844 10 cells/second. 846 Discussion: none. 848 Specification: AF-TM4.0 850 1.2.65. Traffic Contract 852 Definition: A specification of the negotiated traffic characteristics of 853 an ATM connection. 855 Discussion: none. 857 Specification: AF-TM4.0 859 1.2.66. Transmission Convergence (TC): 861 Definition: A sub-layer of the physical layer of the B-ISDN model 862 transforms the flow of cells into a steady flow of bits and bytes for 863 transmission over the physical medium. On transmit the TC sublayer maps 864 the cells to the frame format, generates the Header Error Check (HEC), and 865 sends idle cells when the ATM layer has none to send. On reception, the TC 866 sublayer delineates individual cells in the received bit stream, and uses 867 the HEC to detect and correct received errors. 869 Discussion: TC is not a measurement, but the speed in which TC can occur 870 on a bit stream can be measured. This measurement will not be discussed in 871 this document. 873 Specification: AF-UNI3.1 875 1.2.67. TDF: 877 Definition: An ABR service parameter, TDF controls the decrease in ACR 878 associated with TOF. TDF is signaled as TDFF, where TDF=TDFF/RDF times the 879 smallest power of 2 greater or equal to PCR. TDF is in units of 1/seconds. 881 Discussion: For ABR traffic, TDF effects the time rate of change of the 882 ACR. This value effects TCP round trip time calculations, which in turn 883 effects TCP throughput. 885 Specification: AF-TM4.0 887 1.2.68. TDFF. 889 Definition: Refer to TDF. TDFF is either zero or a power of two in the 890 range 1/64 to 1 in units of 1 /cells. 892 Discussion: Refer to TDF. 894 Specification: AF-TM4.0 896 1.2.69. Traffic Management (TM): 898 Definition: Traffic Management is the aspect of the traffic control and 899 congestion control procedures for ATM. ATM layer traffic control refers to 900 the set of actions taken by the network to avoid congestion conditions. 901 ATM layer congestion control refers to the set of actions taken by the 902 network to minimize the intensity, spread and duration of congestion. The 903 following functions form a framework for managing and controlling traffic 904 and congestion in ATM networks and may be used in appropriate 905 combinations. 906 Connection Admission Control 907 Feedback Control 908 Usage Parameter Control 909 Priority Control 910 Traffic Shaping 911 Network Resource Management 912 Frame Discard 913 ABR Flow Control 915 Discussion: none. 917 Specification: AF-TM4.0 919 1.2.70. Time Out Factor (TOF): 921 Definition: An ABR service parameter, TOF controls the maximum time 922 permitted between sending forward RM-cells before a rate decrease is 923 required. It is signaled as TOFF where TOF=TOFF+1. TOFF is a power of 2 924 in the range: 1/8 to 4,096. 926 Discussion: For ABR traffic, TOF effects the time rate of change of the 927 ACR. This value effects TCP round trip time calculations, which in turn 928 effects TCP throughput. 930 Specification: AF-TM4.0 932 1.2.7 1. Time Out Factor (TOFF): 934 Definition: Refer to TOF. 936 Discussion: none 938 Specification: AF-TM4.0 940 1.2.72. Trm. 942 Definition: An ABR service parameter that provides an upper bound on the 943 time between forward RM-cells for an active source. It is 100 times a 944 power of two with a range of 100*2-7 to 100*20 946 Discussion: For ABR traffic, Trm effects the time rate of change of the 947 ACR. This value effects TCP round trip time calculations, which in turn 948 effects TCP throughput. 950 Specification: AF-TM4.0 952 1.2.73. Traffic Shaping (TS): 954 Definition: Traffic Shaping is a mechanism that alters the traffic 955 characteristics of a stream of cells on a connection to achieve better 956 network efficiency, while meeting the QoS objectives, or to ensure 957 conformance at a subsequent interface. Traffic shaping must maintain cell 958 sequence integrity on a connection. Shaping modifies traffic 959 characteristics of a cell flow with the consequence of increasing the mean 960 Cell Transfer Delay. 962 Discussion: TS should improve TCP throughput by reducing round trip time 963 variations. 965 Specification: AF-UNI3.1 967 1.2.74. Unspecified Bit Rate (UBR): 969 Definition: UBR is an ATM service category, which does not specify traffic 970 related service guarantees. Specifically, UBR does not include the notion 971 of a per-connection-negotiated bandwidth. No commitments are made with 972 respect to the cell loss ratio experienced by a UBR connection, or as to 973 the cell transfer delay experienced by cells on the connection. 975 Discussion: RFC 2331 specifies UBR service class for IP over ATM. UBR 976 service models the best effort service type specified in RFC 791; 977 however, UBR has specific drawbacks with respect to TCP service. Since 978 UBR makes no guarantee with respect to cell loss, cell delay variation or 979 cell mis-insertion, TCP round trip time estimates may not be accurate. 981 Specification: AF-TM4.0 983 1.2.75. User-Network Interface (UNI): 985 Definition: An interface point between ATM end users and a private ATM 986 switch, or between a private ATM switch and the public carrier ATM 987 network; defined by physical and protocol specifications per ATM Forum UNI 988 documents. The standard adopted by the ATM Forum to define connections 989 between users or end stations and a local switch. 991 Discussion: none. 993 Specification: AF-UNI3.1 995 1.2.76. Usage Parameter Control (UPC): 997 Definition: Usage Parameter Control is defined as the set of actions taken 998 by the network to monitor and control traffic, in terms of traffic offered 999 and validity of the ATM connection, at the end-system access. Its main 1000 purpose is to protect network resources from malicious as well as 1001 unintentional misbehavior, which can affect the QoS of other already 1002 established connections, by detecting violations of negotiated parameters 1003 and taking appropriate actions. 1005 Discussion: none. 1007 Specification: AF-TM4.0 1009 1.2.77. Variable Bit Rate (VBR): 1011 Definition: An ATM Forum defined service category which supports variable 1012 bit rate data traffic with average and peak traffic parameters. 1014 Discussion: VBR may potentially adversely effect TCP throughput due to 1015 large round trip time variations. 1017 Specification: AF-TM4.0 1019 1.2.78. VC: 1021 Definition: A communications channel that provides for the sequential 1022 unidirectional transport of ATM cells. 1024 Discussion: none. 1026 Specification: AF-TM3.1 1028 1.2.79. Virtual Channel Connection (VCC): 1030 Definition: A concatenation of VCI's that extends between the points where 1031 the ATM service users access the ATM layer. The points at which the ATM 1032 cell payload is passed to, or received from, the users of the ATM Layer 1033 (i.e., a higher layer or ATM-entity) for processing signify the endpoints 1034 of a VCC. VCC's are unidirectional. 1036 Discussion: none. 1038 Specification: AF-TM3.1 1040 1.2.80. Virtual Channel Identifier (VCI): 1042 Definition: A unique numerical tag as defined by a 16 bit field in the ATM 1043 cell header that identifies a virtual channel, over which the cell is to 1044 travel. 1046 Discussion: none. 1048 Specification: AF-UNI3.1 1050 1.2.8 1. Virtual Path (VP): 1052 Definition: A unidirectional logical association or bundle of VCs. 1054 Discussion: none. 1056 Specification: AF-UNI3.1 1058 1.2.82. Virtual Path Connection (VPC): 1060 Definition: A concatenation of VPIs between Virtual Path Terminators 1061 (VPT's). VPC's are unidirectional 1063 Discussion: none. 1065 Specification: AF-TM3.1 1067 1.2.83. Virtual Path Identifier (VPI): 1069 Definition: An eight-bit field in the ATM cell header that indicates the 1070 virtual path over which the cell should be routed. 1072 Discussion: none. 1074 Specification: AF-UNI3.1 1076 1.2.84. Virtual Source/Virtual Destination (VSND): 1078 Definition: An ABR connection may be divided into two or more separately 1079 controlled ABR segments. Each ABR control segment, except the first, is 1080 sourced by a virtual source. A virtual source implements the behavior of 1081 an ABR source endpoint. Backward RM-cells received by a virtual source are 1082 removed from the connection. Each ABR control segment, except the last, 1083 is terminated by a virtual destination. A virtual destination assumes the 1084 behavior of an ABR destination endpoint. Forward RM-cells received by a 1085 virtual destination are turned around and not forwarded to the next 1086 segment of the connection. 1088 Discussion: none. 1090 Specification: AF-TM4.0 1092 1.2.85. Xrm Decrease Factor (XDM): 1094 Definition: An ABR service parameter, XDF controls the decrease in ACR 1095 associated with Xrm. It is a power of two in range: [0, 1]. 1097 Discussion: For ABR traffic, XDM effects the time rate of change of the 1098 ACR. This value effects TCP round trip time calculations, which in turn 1099 effects TCP throughput. 1101 Specification: AF-TM4.0 1102 1.2.86. Xrm: 1104 Definition: An ABR service parameter, Xrm limits the number of forward RM- 1105 cells which may be sent in the absence of received backward PM-cells. The 1106 range is 0-255. 1108 Discussion: For ABR traffic, Xrm effects the time rate of change of the 1109 ACR. This value effects TCP round trip time calculations, which in turn 1110 effects TCP throughput. 1112 Specification: AF-TM4.0 1114 2. Performance Metrics 1116 2. 1. Definition Format (from RFC 1242) 1118 Metric to be defined. 1120 Definition: The specific definition for the metric. 1122 Discussion: A brief discussion of the metric, its application and any 1123 restrictions on measurement procedures. 1125 Measurement units: Intrinsic units used to quantify this metric. This 1126 includes subsidiary units; e.g., microseconds are acceptable if the 1127 intrinsic unit is seconds. 1129 2.2. Definitions 1131 2.2.1. Physical Layer- SONET 1133 2.2.1.1. Pointer Movements 1135 Definition: Pointer Movements is the number of changes in a SONET pointer 1136 due to clock synchronization slips. 1138 Discussion: SONET Pointer Movements can cause loss of information in the 1139 SONET payload envelop (SPE) which contains IP datagrams, either in the 1140 form of cells or as PPP delimited PDUs. 1142 Measurement Units: Per second. 1144 2.2.1.2. Transport Overhead Error Count 1146 Definition: SONET Transport Overhead Error Count is the number of SONET 1147 transport overhead errors detected. 1149 Discussion: SONET Transport Overhead Errors SONET Transport Overhead 1150 Errors cause SONET frames to be lost. These frames may contain IP 1151 datagrams, either in the form of cells or as PPP delimited PDUs. 1153 Measurement Units: Positive integer 1155 2.2.1.3. Path Overhead Error Count 1157 Definition: SONET Path Overhead Error Count is the number of SONET path 1158 overhead errors detected. 1160 Discussion: SONET Path Overhead Errors cause SONET frames to be lost. 1161 These frames may contain IP datagrams, either in the form of cells or as 1162 PPP delimited PDUs. 1164 Measurement Units: Positive integer 1166 2.2.2. ATM Layer 1168 2.2.2.1. Cell Delay Variation (CDV): 1170 Definition: The variation in cell transfer delay associated with a given 1171 traffic load, orientation and distribution, as well as an integration 1172 period. CDV = max (CTD) - min (CTD) where max and min indicate the maximum 1173 and minimum over the integration period, respectively. 1175 Discussion: 1176 CDV is a component of cell transfer delay, induced by buffering and cell 1177 scheduling. Peak-to-peak CDV is a QoS delay parameter associated with CBR 1178 and VBR services. The peak-to-peak CDV is the ((1-a) quantile of the CTD) 1179 minus the fixed CTD that could be experienced by any delivered cell on a 1180 connection during the entire connection holding time. The parameter "a" is 1181 the probability of a cell arriving late. 1183 CDV effects TCP round trip time calculations. Large values of CDV will 1184 adversely effect TCP throughput. 1186 Measurement Units: seconds 1188 2.2.2.2. Cell Delay Variation Tolerance (CDVT): 1190 Definition: ATM layer functions may alter the traffic characteristics of 1191 ATM connections by introducing Cell Delay Variation. When cells from two 1192 or more ATM connections are multiplexed, cells of a given ATM connection 1193 may be delayed while cells of another ATM connection are being inserted at 1194 the output of the multiplexer. Similarly, some cells may be delayed while 1195 physical layer overhead or OAM cells are inserted. Consequently, some 1196 randomness may affect the inter-arrival time between consecutive cells of 1197 a connection as monitored at the UNI. The upper bound on the "clumping" 1198 measure is the CDVT. 1200 Discussion: 1201 CDVT effects TCP round trip time calculations. Large values of CDVT will 1202 adversely effect TCP throughput. 1204 Measurement units: seconds 1206 2.2.2.3. Cell Error Ratio (CER): 1208 Definition: The ratio of errored cells in a transmission in relation to 1209 the total cells sent in a transmission associated with a given traffic 1210 load, orientation and distribution, as well as an integration period. 1211 CER = Errored Cells / Total Cells Transmitted. 1213 Discussion: The measurement is taken over a time interval and is desirable 1214 to be measured on an in-service circuit. 1216 CER causes ATM cells to be lost. These cells may contain AAL5 segments of 1217 IP datagrams. 1219 Measurement Units: dimensionless. 1221 2.2.2.4. Cell Loss Ratio (CLR): 1223 Definition: The ratio of lost cells in a transmission in relation to the 1224 total cells sent in a transmission associated with a given traffic load, 1225 orientation and distribution, as well as an integration period. CLR 1226 Lost Cells / Total Cells Transmitted. 1228 Discussion: 1229 CLR is a negotiated QoS parameter and acceptable values are network 1230 specific. The objective is to minimize CLR provided the end-system adapts 1231 the traffic to the changing ATM layer transfer characteristics. The CLR 1232 parameter is the value of CLR that the network agrees to offer as an 1233 objective over the lifetime of the connection. It is expressed as an order 1234 of magnitude, having a range of 10-1 to 10-15 and unspecified. 1236 CLR measures the number of ATM cells lost. These cells may contain AAL5 1237 segments of IP datagrams. 1239 Measurement Units: dimensionless. 1241 2.2.2.5. Cell Misinsertion Rate (CMR): 1243 Definition: The ratio of cells received at an endpoint that were not 1244 originally transmitted by the source end in relation to the total number 1245 of cells properly transmitted associated with a given traffic load, 1246 orientation and distribution, as well as an integration period. CMR=Mis- 1247 inserted Cells / Total Cells Transmitted. 1249 Discussion: 1250 CMR causes ATM streams to be corrupted. These streams may contain AAL5 1251 segments of IP datagrams. 1253 Measurement Units: dimensionless. 1255 2.2.2.6. Cell Rate Margin (CRM): 1257 Definition: This is a measure of the difference between the effective 1258 bandwidth allocation and the allocation for sustainable rate in cells per 1259 second. 1261 Discussion: none. 1263 Measurement units: Cells per second 1265 2.2.2.7. CRC Error Ratio: 1267 Definition: The ratio of PDUs received at an endpoint that which contain 1268 an invalid CRC in relation to the total number of cells properly 1269 transmitted associated with a given traffic load, orientation and 1270 distribution, as well as an integration period. 1272 Discussion: 1273 CRC errors cause ATM cells to be lost. These cells may contain AAL5 1274 segments of IP datagrams. 1276 Measurement Units: dimensionless 1278 2.2.2.8. Cell Transfer Delay (CTD): 1280 Definition: The elapsed time between a cell exit event at the measurement 1281 point 1 (e.g., at the source UNI) and the corresponding cell entry event 1282 at a measurement point 2 (e.g., the destination UNI) for a particular 1283 connection. 1285 Discussion: 1286 The cell transfer delay between two measurement points is the sum of the 1287 total inter-ATM node transmission delay and the total ATM node processing 1288 delay. 1290 Measurement units: seconds 1291 2.2.3. ATM Adaptation Layer (AAL) Type 5 (AAL5) 1293 2.2.3.1. AAL5 Reassembly Errors 1295 Definition: AAL5 Reassembly Errors constitute any error which causes the 1296 AAL5 PDU to be corrupted. 1298 Discussion: 1299 AAL5 Reassembly errors cause AAL5 PDUs to be lost. These PDUs may 1300 contain IP datagrams. 1302 Measurement Units: Positive Integer 1304 2.2.3.2. AAL5 Reassembly Time 1306 Definition: AAL5 Reassembly Time constitutes the time between the arrival 1307 of the final cell in the AAL5 PDU and the AAL5 PDU being made available to 1308 the service layer. 1310 Discussion: 1311 AAL5 Reassembly time directly effects TCP round trip time calculations. 1313 Measurement Units: seconds 1315 2.2.3.3. AAL5 CRC Error Ratio: 1317 Definition: The ratio of PDUs received at an endpoint that which contain 1318 an invalid CRC in relation to the total number of cells properly 1319 transmitted associated with a given traffic load, orientation and 1320 distribution, as well as an integration period. 1322 Discussion: 1323 AAL5 CRC errors causes AAL5 PDUs to be dropped. These PDUs may contain 1324 IP datagrams. 1326 Measurement Units: dimensionless 1328 3. Security Considerations. 1329 As this document is solely for the purpose of providing terminology and 1330 describes neither a protocol nor an implementation, there are no security 1331 considerations associated with this document. 1333 4. References 1334 [AF-ILMI4.0] ATM Forum Integrated Local Management Interface Version 4.0, 1335 af-ilmi-0065.000, September 1996. 1336 [AF-TEST-0022] Introduction to ATM Forum Test Specifications, af-test- 1337 0022.00, December 1994. 1339 [AF-TM4.0] ATM Forum, Traffic Management Specification Version 4.0, af-tm- 1340 0056.00, April 1996. 1341 [AF-UNI3.1] ATM Forum, User Network Interface Specification Version 3.1, 1342 September 1994. 1343 [AF-UNI4.0] ATM Forum, User Network Interface Specification Version 4.0, 1344 July 1996. 1346 5. Editor's Addresses 1347 Jeffrey Dunn 1348 Advanced Network Consultants, Inc. 1349 11241-B Skilift Court, Columbia, MD 21044 USA 1350 Phone: +1 (410) 730-6300, E-mail: Jeffrey.Dunn@worldnet.att.net 1352 Cynthia Martin 1353 Advanced Network Consultants, Inc. 1354 11241-B Skilift Court, Columbia, MD 21044 USA 1355 Phone: +1 (410) 730-6300, E-mail: Cynthia.E.Martin@worldnet.att.net