1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T X.151TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2003) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS Public data networks Maintenance Frame Relay operations and maintenance Principles and functions ITU-T Recommendation X.151 ITU-T X-SERIE
2、S RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS PUBLIC DATA NETWORKS Services and facilities X.1X.19 Interfaces X.20X.49 Transmission, signalling and switching X.50X.89 Network aspects X.90X.149 Maintenance X.150X.179 Administrative arrangements X.180X.199 OPEN SYSTEMS INTERCONNECTION
3、 Model and notation X.200X.209 Service definitions X.210X.219 Connection-mode protocol specifications X.220X.229 Connectionless-mode protocol specifications X.230X.239 PICS proformas X.240X.259 Protocol Identification X.260X.269 Security Protocols X.270X.279 Layer Managed Objects X.280X.289 Conforma
4、nce testing X.290X.299 INTERWORKING BETWEEN NETWORKS General X.300X.349 Satellite data transmission systems X.350X.369 IP-based networks X.370X.399 MESSAGE HANDLING SYSTEMS X.400X.499 DIRECTORY X.500X.599 OSI NETWORKING AND SYSTEM ASPECTS Networking X.600X.629 Efficiency X.630X.639 Quality of servic
5、e X.640X.649 Naming, Addressing and Registration X.650X.679 Abstract Syntax Notation One (ASN.1) X.680X.699 OSI MANAGEMENT Systems Management framework and architecture X.700X.709 Management Communication Service and Protocol X.710X.719 Structure of Management Information X.720X.729 Management funct
6、ions and ODMA functions X.730X.799 SECURITY X.800X.849 OSI APPLICATIONS Commitment, Concurrency and Recovery X.850X.859 Transaction processing X.860X.879 Remote operations X.880X.899 OPEN DISTRIBUTED PROCESSING X.900X.999 For further details, please refer to the list of ITU-T Recommendations. ITU-T
7、Rec. X.151 (10/2003) i ITU-T Recommendation X.151 Frame Relay operations and maintenance: Principles and functions Summary This Recommendation defines the basic Frame Relay Operations and Maintenance Principles and Functions. The quality of Frame Relay services can be tested, measured and diagnosed
8、using OAM frames. FR OAM frames can be used to measure the primary performance parameters of frame relay networks. OAM frames provide the ability to do in-service monitoring on both SVC and PVC connections. This Recommendation includes a network reference model, an overview of the OAM frame structur
9、e, and OAM measurement procedures. The contents of this Recommendation are based on the reference model, the OAM protocol formats, the OAM procedures and descriptions of message flows as defined in FRF.19 Frame Relay Operations, Administration, and Maintenance Implementation Agreement. Additionally
10、procedures for measurement of frame delay jitter, frame loss ratio and use of loopback for fault detection are defined. Source ITU-T Recommendation X.151 was approved by ITU-T Study Group 17 (2001-2004) under the ITU-T Recommendation A.8 procedure on 29 October 2003. ii ITU-T Rec. X.151 (10/2003) FO
11、REWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and is
12、suing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these t
13、opics. 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 necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expressi
14、on “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability)
15、 and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recomm
16、endation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the 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
17、claimed Intellectual Property Rights, whether asserted by ITU members or others outside of 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 Re
18、commendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written pe
19、rmission of ITU. ITU-T Rec. X.151 (10/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations 2 5 Conventions 3 6 Reference model . 3 7 OAM protocol formats . 6 7.1 Encapsulation formats 6 7.2 OAM message format. 8 7.3 OAM information fields. 11 8 OAM procedures 19 8.1 Mess
20、age encoding/decoding rules 19 8.2 General message processing. 20 8.3 Hello message processing (device discovery) 22 8.4 Service level verification message processing . 24 8.5 Non-latching loopback message processing. 30 8.6 Latching loopback message processing 31 8.7 Diagnostic indication message p
21、rocessing . 32 8.8 Network applications of loopback 32 Appendix I General receive procedures 34 Appendix II Message flows 35 II.1 Discovery 35 II.2 FTD measurement 36 II.3 FDR/DDR measurement 37 II.4 Non-latching loopback . 39 II.5 Latching loopback 40 Appendix III Example of delivery ratio calculat
22、ion . 41 III.1 Ingress processing 42 III.2 Egress processing . 42 ITU-T Rec. X.151 (10/2003) 1 ITU-T Recommendation X.151 Frame Relay operations and maintenance: Principles and functions 1 Scope This Recommendation specifies OAM frame formats and procedures for measuring the performance of frame rel
23、ay networks. OAM provides a means to test, diagnose and measure the quality of frame relay services. The protocol and procedures may be used by public frame relay networks and by service providers and/or end-users. The procedures are applicable to PVCs, as well as to the data transfer phase of SVCs.
24、 The following clauses of this Recommendation are based on the text of FRF.19: Clause 6. A reference model for different networks and domains over which FR OAM measurements can be made. Clause 7. OAM protocol formats Detailed structure (message formats) of FR OAM frames. Clause 8. OAM procedures use
25、 of FR OAM frames to measure the primary performance parameters of frame relay services. Appendices I, II and III Informative text describing general receive procedures, message flows and delivery ratio calculation to aid interpretation and interoperability. The following clauses of this Recommendat
26、ion are additional to the text of FRF.19: Clause 8.4.3.6: Procedures for the estimation of frame delay jitter. Clause 8.4.4.5: Frame loss ratio calculation. Clause 8.8: Network applications of loopback. NOTE Interoperability with ATM OAM as defined by ITU-T Rec. I.610 and other OAM protocols is beyo
27、nd the scope of this Recommendation. 2 References The following ITU-T Recommendations 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 ot
28、her references are subject to revision; users of this Recommendation are therefore encouraged 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. The r
29、eference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Recommendation E.164 (1997), The international public telecommunication numbering plan. ITU-T Recommendation I.370 (1991), Congestion management for the ISDN frame rel
30、aying bearer service. ITU-T Recommendation I.555 (1997), Frame Relaying Bearer Service interworking. ITU-T Recommendation I.610 (1999), B-ISDN operation and maintenance principles and functions. ITU-T Recommendation X.36 (2003), Interface between Data Terminal Equipment (DTE) and Data Circuit-termin
31、ating Equipment (DCE) for public data networks providing frame relay data transmission service by dedicated circuit. 2 ITU-T Rec. X.151 (10/2003) ITU-T Recommendation X.76 (2003), Network-to-network interface between public data networks providing PVC and/or SVC frame relay data transmission service
32、. ITU-T Recommendation X.121 (2000), International numbering plan for public data networks. ITU-T Recommendation X.144 (2003), User information transfer performance parameters for public frame relay data networks. ITU-T Recommendation X.145 (2003), Connection establishment and disengagement performa
33、nce parameters for public Frame Relay data networks providing SVC services. ITU-T Recommendation X.146 (2000), Performance objectives and quality of service classes applicable to frame relay. ITU-T Recommendation X.147 (2003), Frame Relay network availability. ITU-T Recommendation X.148 (2003), Proc
34、edures for the measurement of the performance of public data networks providing the international frame relay service. Frame Relay Forum Implementation Agreement 19, FRF.19 (2001), Frame relay operations, administration, and maintenance implementation agreement. 3 Definitions The following terms, wh
35、en used in this Recommendation, are used as defined in ITU-T Recs X.144, X.145, X.146, X.147 and X.148. Frame Transfer Delay Frame Delivery Ratio Data Delivery Ratio Frames_offered Frames_received Data_offered Data_received Availability 4 Abbreviations This Recommendation uses the following abbrevia
36、tions: AESA ATM End System Address ATM Asynchronous Transfer Mode BECN Backward Explicit Congestion Notification CIR Committed Information Rate DCE Data Circuit-terminating Equipment DDR Data Delivery Ratio DE Discard Eligibility DLCI Data Link Connection Identifier DTE Data Terminal Equipment FDR F
37、rame Delivery Ratio FECN Forward Explicit Congestion Notification ITU-T Rec. X.151 (10/2003) 3 FR Frame Relay FROMP Frame Relay OAM Maintenance Point FTD Frame Transfer Delay IA Implementation Agreement IEEE Institute of Electrical and Electronics Engineers IF Information Field IPv4 Internet Protoco
38、l Version 4 ITU International Telecommunication Union MTU Maximum Transmission Unit NLPID Network Layer Protocol Identification NNI Network-to-Network Interface OAM Operations, Administration and Maintenance OUI Organizationally Unique Identifier PHY Physical Interface PVC Permanent Virtual Circuit
39、SLA Service Level Agreement SVC Switched Virtual Circuit UNI User-to-Network Interface VC Virtual Circuit 5 Conventions For the purposes of ensuring interoperability of OAM systems, the following terms, when used in this Recommendation and highlighted in bold, are used as defined in this clause: Mus
40、t, Shall, or Mandatory the item is an absolute requirement of this Recommendation. Should the item is highly desirable. May or Optional the item is not compulsory, and may be followed or ignored according to the needs of the Recommendation. Not Applicable the item is outside the scope of this Recomm
41、endation. NOTE The abbreviation OAM is used throughout this Recommendation and has the same meaning as the abbreviation OA An OAM message (see 7.2) containing one or more; OAM Information Fields (see 7.3). NOTE See 8.1 for rules on encoding and decoding these formats. Figures throughout this Recomme
42、ndation illustrate 2-octet DLCI encoding. Both 2- and 4-octet addresses are supported in all cases. 7.1 Encapsulation formats The frame relay OAM protocol supports two encapsulation formats. These formats allow for implementation in a variety of network elements and for compatibility with U-plane tr
43、affic formats. ITU-T Rec. X.151 (10/2003) 7 Implementations must support the multiprotocol encapsulation format to be compliant with this Recommendation. Implementations may optionally support the non-UI encapsulations. 7.1.1 Multiprotocol encapsulation The multiprotocol encapsulation format is comp
44、atible with frame relay equipment and applications. The format uses a NLPID (0xB2) to distinguish OAM traffic from U-plane traffic conforming to ITU-T Rec. X.36. Figure 4 depicts the multiprotocol encapsulation format when an X.36 2-octet header is used. Bits 8 7 6 5 4 3 2 1 Octet DLCI (msb) C/R EA
45、x x x x x x 0 0 1 DLCI (Isb) FECN BECN DE EA x x x x x x x 1 2 Control 0 0 0 0 0 0 1 1 3 (Note) NLPID 1 0 1 1 0 0 1 0 4 FR_OAM Message 5 NOTE Control is at octet 5 when 4-octet addressing of X.36 is used. Figure 4/X.151 Multiprotocol encapsulation format 7.1.2 Non-UI encapsulation The non-UI encapsu
46、lation format is designed for use with frame relay traffic that is not distinguishable from the OAM multiprotocol encapsulation format. The prime example of this is clause 5/I.555 (X.25 encapsulated) traffic. Figure 5 depicts the non-UI encapsulation format when an X.36 2-octet header is used. Bits
47、8 7 6 5 4 3 2 1 Octet DLCI (msb) C/R EA x x x x x x 0 0 1 DLCI (Isb) FECN BECN DE EA x x x x x x x 1 2 Control 0 0 0 0 0 0 1 0 3 (Note) NLPID 1 0 1 1 0 0 1 0 4 FR_OAM Message 5 NOTE Control is at octet 5 when 4-octet addressing of X.36 is used. Figure 5/X.151 Non-UI encapsulation format 8 ITU-T Rec.
48、 X.151 (10/2003) 7.2 OAM message format Figure 6 depicts the format of OAM messages. Bits 8 7 6 5 4 3 2 1 Octet Message type (see 7.2.1) N + 1 (Note 1) Domain identification (see 7.2.2) N + 2 Source location identifier (see 7.2.3) N + 7 Destination location identifier (see 7.2.4) N + 11 Information
49、field 1 (see 7.2.5) N + 15 Information field x N + m (Note 2) NOTE 1 Offset N is 4, 6, or 10, depending upon encapsulation and address size used. NOTE 2 Information fields are populated as needed. Figure 6/X.151 OAM message format 7.2.1 Message type field The purpose of the message type field is to identify the message being sent. Values for this field are shown in Table 1. Table 1/X.151 OAM message type values Message type value Usage 0x1 Hello (see 8.3
