1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 1.371.1 (1 1 /2000) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Overall network aspects and functions - General network requirements and functions Guaranteed frame rate ATM transfer capability ITU-T Recomme
2、ndation 1.371 .I (Formerly CCITT Recommendation) ITU-T I-SERIES RECOMMENDATIONS INTEGRATED SERVICES DIGITAL NETWORK GENERAL STRUCTURE Terminology Description of ISDNs General modelling methods Telecommunication network and service attributes General description of asynchronous transfer mode Scope Ge
3、neral aspects of services in ISDN Common aspects of services in the ISDN Bearer services supported by an ISDN Teleservices supported by an ISDN Supplementary services in ISDN Network functional principles Reference models Numbering, addressing and routing Connection types Performance obiectives SERV
4、ICE CAPABILITIES OVERALL NETWORK ASPECTS AND FUNCTIONS 1.110-1.119 1.120-1.129 I. 130-1.139 I. 140-1.149 I. 150-1.199 1.200-1.209 1.210-1.219 1.220-1.229 1.230-1.239 1.240-1.249 1.250-1.299 1.3 10-1.3 19 1.320-1.329 1.330-1.339 1.340-1.349 1.350-1.359 ISDN USER-NETWORK INTERFACES Application of I-se
5、ries Recommendations to ISDN user-network interfaces Layer 1 Recommendations Layer 2 Recommendations Layer 3 Recommendations Multiplexing, rate adaption and support of existing interfaces Aspects of ISDN affecting terminal requirements INTERNETWORK INTERFACES MAINTENANCE PRINCIPLES B-ISDN EQUIPMENT
6、ASPECTS ATM equipment Transport functions Management of ATM equipment Multiplexing aspects 1.420-1.429 1.430-1.439 1.440-1.449 1.450-1.459 1.460-1.469 1.470-1.499 1.500-1.599 1.600-1.699 1.730-1.739 1.740-1.749 1.750-1.759 1.760-1.769 I For further details, please refer to the list of ITD-T Recommen
7、dations. ITU-T Recommendation 1.371.1 Guaranteed frame rate ATM transfer capability Summary This Recommendation specifies the Guaranteed Frame Rate ATM Transfer Capability as an extension to the ATCs specified in ITU-T 1.37 1. Source ITU-T Recommendation 1.37 1.1 was prepared by ITU-T Study Group 13
8、 (200 1-2004) and approved under the WTSA Resolution 1 procedure on 24 November 2000. ITU-T 1.371.1 (11/2000) 1 FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-
9、T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four ye
10、ars, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the nec
11、essary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the
12、 possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of
13、 the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest i
14、nformation and are therefore strongly urged to consult the TSB patent database. o ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing fi-om I
15、TU. 11 ITU-T 1.371.1 (11/2000) CONTENTS 1 2 3 3.1 3.2 3.3 4 4.1 4.2 5 6 6.1 6.2 6.3 Scope . References . Abbreviations and terminology . Abbreviations Terminology External terminology Specification of other traffic parameters . High level description of the GFR ATC . Guaranteed Frame Rate transfer c
16、apability (GFR) . GFR trafic parameters and GFR traffic characteristics . Traffic characteristics relevant to ATCs . Definition and service model Source traffic descriptor and CDV tolerance Conformance definition and QoS commitments 6.3.1 Cell conformance . 6.3.2 Frame conformance and F-GCRA(T, 7) .
17、 6.3.3 QoS commitments . 6.3.4 UPC/NPC actions Appendix I . Additional material related to the F-GCRA . I . 1 The support of QoS commitments through F-GCRA . 1.2 Example implementation illustrating how F-GCRA may be used to support QoS commitments . 1.3 1.4 Proof of a result related to F-GCRA . Appe
18、ndix II - Providing GFR QoS with the CF-GCRA . Appendix III - Expectations of a GFR network element behaviour Appendix IV - Applicability of GFR ATM Transfer Capability to applications Implementation limits for the case of many non-conforming frames . Page 1 1 1 1 2 2 2 2 3 3 4 4 5 5 5 6 7 8 8 8 9 9
19、 9 11 12 13 . ITU-T 1.371.1 (11/2000) 111 ITU-T Recommendation 1.371.1 Guaranteed frame rate ATM transfer capability 1 Scope This Recommendation extends the specification of ATM Transfer Capabilities provided in ITU-T 1.371 with the specification of the Guaranteed Frame Rate ATC. It provides a gener
20、al description, the definition and service model, the source traffic descriptor and the conformance definition and QoS commitments for GFR. Appendices I to IV contain additional material related to the F-GCRA (used in the GFR conformance definition). 2 References The following ITU-T Recommendations
21、and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore enc
22、ouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. 11 2 ITU-T 1.371 (2000), Trafic control and congestion control in B-ISDN. ITU-T 1.356 (2000
23、), B-ISDNATM layer cell transferperfomance. 3 Abbreviations and terminology ATC ATM AUU B-ISDN CDV CF-GCRA CLP CLR F-GCRA GCRA GFR LIT MBS MCR MFS 3.1 Abbreviations This Recommendation uses the following abbreviations. ATM Transfer Capability Asynchronous Transfer Mode ATM user to ATM user indicatio
24、n (ITU-T 1.361) Broadband ISDN Cell Delay Variation Conforming Cell F-GCRA (Appendix II) Cell Loss Priority (bit) Cell Loss Ratio Frame based Generic Cell Rate Algorithm Generic Cell Rate Algorithm Guaranteed Frame Rate Last Increment Time Maximum Burst Size Minimum Cell Rate Maximum Frame Size ITU-
25、T 1.371.1 (11/2000) 1 NPC Network Parameter Control OAM Operation And Maintenance PCR Peak Cell Rate QOS Quality of Service RM Resource Management UPC Usage Parameter Control vcc Virtual Channel Connection 3.2 Terminology For the purpose of this Recommendation, the terminology as used in ITU-T 1.371
26、 applies. 3.3 External terminology Term Acronym Reference Cell delay variation CDV ITU-T 1.356 Cell loss ratio CLR ITU-T 1.356 Cell loss priority CLP ITU-T I. 150 4 This clause lists the additional GFR trafic parameters and the GFR trafic characteristics to extend the specification provided in 5.4.2
27、.3h.371 and 5.4.4h.371. GFR traffic parameters and GFR traffic characteristics 4.1 The following traffic parameters are specified to extend the list provided in 5.4.2.3h.371. - Specification of other traffic parameters Minimum Cell Rate (MCR): For a GFR connection it is used (in conjunction with oth
28、er parameters) to quanti the lower bound on the number of cells to which the committed QoS applies. It is specified on a per-connection basis. Maximum Frame Size (MFS): The maximum number of user generated cells in a frame that may be sent on a GFR connection. - 2 ITU-T 1.371.1 (11/2000) 4.2 The fol
29、lowing traffic characteristics apply to GFR and extend Table 1h.371. Traffic characteristics relevant to ATCs PCR(O+l) Table 1A.371.1- Traffic characteristics relevant to GFR 5.4. M.37 1 X I I Parameter reference I GFR I zPCR(o+1) zZBdo 5.4. M.37 1 X 5.4.2h.371 X (Note 1) Frame tagging MFS I MCR(0)
30、I 5.4.3/1.371,6.7.2/I.371,6.2 I X I 6 (Note 2) 6.2 X 6.2 X NOTE 1 - The value of zzBTis derived fkom the parameters MBS, PCR and MCR (see 6.3.3). NOTE 2 - Frame tagging applies to GFR2 only. 5 High level description of the GFR ATC This clause contains the high level description of the Guaranteed Fra
31、me Rate ATM Transfer Capability, to extend the descriptions provided in 6.2h.37 1. The GFR transfer capability provides a minimum cell rate (MCR) for loss tolerant, non-real time applications with the expectation of transmitting data in excess of the MCR. It is assumed that the user generated data c
32、ells are organized in the form of frames that are delineated at the ATM layer. The network does not provide feedback to the user concerning instantaneous available network resources. Traffic parameters are PCR(O+l), MCR(O), a maximum burst size MBS(O), a maximum frame size MFS(O+l) and tolerances as
33、sociated with PCR(O+l) and MCR(0). A GFR cell is conforming if it conforms to the PCR(O+l), if it conforms to the maximum frame size and if it conforms to the homogeneous setting of the CLP bit of cells within the same frame. A GFR frame is conforming if all its cells are conforming and if the frame
34、 conforms to the Frame based GCRA, F-GCRA(T,T), with parameters T= l/MCR and T= TIBT+TMCR, where TIBT= (MBS- 1) x (l/MCR- l/PCR). By sending a frame with all CLP = 1 cells, the user indicates to the network that such a frame is of lesser importance than a frame with all CLP = O cells on the same GFR
35、 connection. The GFR ATC allows the commitment to transmit the number of cells in conforming frames with the QoS corresponding to the associated QoS class. QoS commitments can only apply to cells in CLP = O frames of which all cells are conforming. Furthermore, with GFR the network attempts to deliv
36、er complete frames in excess of the minimum cell rate commitment, if all cells in the frame are conforming and provided that sufficient resources are available. There are two variants of GFR: GFR1 and GFR2. In GFR1, tagging is not applicable. In GFR2, the network may apply frame tagging to non-confo
37、rming frames. Frame tagging means that the CLP bit of each cell of the frame is changed to 1. Frames tagged by the network and frames marked as CLP = 1 by the user are treated identically by the network. For a complete specification of the GFR ATC, refer to clause 6. ITU-T 1.371.1 (11/2000) 3 6 This
38、 clause contains the definition of the Guaranteed Frame Rate ATM Transfer Capability, to extend the definitions provided in 6.4-6.7h.37 1. Some users have traffic characteristics that make it difficult to determine trafic parameters required by existing ATM transfer capabilities. Often such users ar
39、e also not able to react to explicit feedback from the ATM network. In addition, user data is often organized in frames and may tolerate loss. For sources of such user data it may be sufficient to get a low cell loss commitment that applies to a minimum cell rate and to expect that some of the frame
40、s in excess of the minimum cell rate are delivered. To support such trafic in an ATM network, an ATM transfer capability is defined which is termed Guaranteed Frame Rate (GFR). Guaranteed Frame Rate transfer capability (GFR) 6.1 Definition and service model The Guaranteed Frame Rate (GFR) ATM transf
41、er capability is intended to support non-real-time applications. The GFR ATC requires that the user data cells are organized in the form of frames that can be delineated at the ATM layer. The GFR applies to ATM connections that delineate frames using the AU indication. Any other delineation method,
42、e.g. the use of RM cells, is for further study. The GFR ATC only applies to VCCs, because the AU indication is not a reliable frame delineation at the VP sublayer. In the GFR ATC, the user can send a frame either unmarked or marked. By marking a frame the user indicates that the frame is of lesser i
43、mportance than an unmarked frame on that particular GFR connection. An unmarked frame has all cells of the frame set to CLP = O, a marked frame has all cells in the frame set to CLP = 1. Frames sent by the user should have all cells with the same setting of the CLP bit. QoS commitments do not apply
44、to cells in frames with mixed setting of the CLP bit nor to cells in marked frames. The GFR ATC uses a Minimum Cell Rate (MCR), in conjunction with a given Maximum Frame Size (MFS) and a given Maximum Burst Size (MBS). The MFS and MBS are both expressed in cells. QoS commitments apply only if MCR is
45、 greater than zero. It is a network option whether the GFR ATC supports MCRs greater than zero. In addition to MCR, MBS and MFS, a PCR for the user generated CLP = O + 1 cells is defined for the GFR ATC. PCR is always larger than MCR. The following two examples describe the commitment that the user
46、of a GFR connection will receive: - If MCR O and if the user sends unmarked frames that do not exceed the Maximum Frame Size and the user sends them at a constant rate that is less than or equal to the MCR, then the commitment is that all these frames are delivered across the network according to th
47、e QoS class. If MCR O and if the user sends unmarked frames that do not exceed the Maximum Frame Size and the user has not sent cells for a long time and the user sends them in a burst with a length that does not exceed the Maximum Burst Size and at a rate that does not exceed PCR, then the commitme
48、nt is that all these frames are delivered across the network according to the QoS class. The GFR ATC also allows the user to send in excess of the negotiated MCR, but trafic that exceeds MCR will only be delivered within the limits of available resources. The GFR ATC does not provide explicit ATM la
49、yer feedback to the source regarding the current level of network congestion. Instead, the level of congestion is derived by the higher layer protocols from the delivery or discard of frames of the connection. VC RM cells on a VCC are not used to operate GFR; however, such cells that would still be present on the connection are considered as part 4 ITU-T 1.371.1 (11/2000) of the user data cell flow. The present version of GFR does not support OAM cells for performance monitoring on a GFR connection. The service model distinguishes between frames of which all cells are conforming and fr
