1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T G.8261.1/Y.1361.1 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1 (05/2014) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Packet over Transport aspects Synchronization, quality and avail
2、ability targets SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Transport Packet delay variation network limits applicable to packet-based methods (Frequency synchronization) Amendment 1: Revision to clause 8 on packet del
3、ay variation Recommendation ITU-T G.8261.1/Y.1361.1 (2012) Amendment 1 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G
4、.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE
5、 TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 T
6、RANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 Ethernet over Transport aspects G.8000G.8099 MPLS over Transport aspects G.8100G.8199 Synchronization, quality and availability targets G.8200G.8299 Service Mana
7、gement G.8600G.8699 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.8261.1/Y.1361.1 (2012)/Amd.1 (05/2014) i Recommendation ITU-T G.8261.1/Y.1361.1 Packet delay variation network limits applicable to packet-based methods (Frequency sy
8、nchronization) Amendment 1 Revision to clause 8 on packet delay variation Summary Amendment 1 to Recommendation ITU-T G.8261.1/Y.1361.1 provides a revision of clause 8 (PDV network limit). History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G.8261.1/Y.1361.1 2012-02-13 15 11.100
9、2/1000/11522 1.1 ITU-T G.8261.1/Y.1361.1 (2012) Amd. 1 2014-05-14 15 11.1002/1000/12190 _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. i
10、i Rec. ITU-T G.8261.1/Y.1361.1 (2012)/Amd.1 (05/2014) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a
11、 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 years, es
12、tablishes 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 necessary
13、standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the
14、 Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) 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 equival
15、ents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claim
16、ed 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 the Recommendation development process. As of the date of approval of this Recommendation, ITU had re
17、ceived notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/
18、ipr/. ITU 2014 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.8261.1/Y.1361.1 (2012)/Amd.1 (05/2014) 1 Recommendation ITU-T G.8261.1/Y.1361.1 Packet delay variation network limits applicable to pa
19、cket-based methods (Frequency synchronization) Amendment 1 Revision to clause 8 on packet delay variation 1 Clause 8 (PDV network limit) Replace clause 8 with the following: 8 PDV network limit The packet delay variation network limit given in this clause represents the maximum permissible levels of
20、 packet delay variation at the interface C shown in Figure 3. In general, these network limits are compatible with the minimum tolerance to packet delay variation that all PEC-S-F equipment are required to provide. NOTE 1 It should be recognized that, as a result of some network performance degradat
21、ions, failure conditions, maintenance actions and other events the PDV network limits might not be met. During these exceptional infrequent conditions and for a short settling period afterwards the slave clock is not required to meet the performance objectives that are specified in ITU-T G.8263. The
22、 length of the required settling period is for further study. NOTE 2 The PEC embedded within the end application, as shown after the connection C2 in Figure 3 is for further study in ITU-T G.8263. Note that the PDV network limit specified in this clause assumes that the network equipment composing t
23、he hypothetical reference model generates a controlled amount of PDV. It is known that some network equipment may generate excessive PDV and may potentially exceed these PDV network limits. What constitutes a controlled amount of PDV, how to determine if network equipment is suitable for considerati
24、on in the hypothetical reference models defined in this Recommendation, or in a reduced hypothetical reference model, as well as how to evaluate the level of PDV generated by network equipment, is for further study. 8.1 HRM-1 network limit 8.1.1 Network limit The packet delay variation network limit
25、 at point C of Figure 3 for the HRM-1 shown in Figure 1 is defined as follows: With window interval W = 200 s and fixed cluster range = 150 s starting at the floor delay, the network transfer characteristic quantifying the proportion of delivered packets that meet the delay criterion should satisfy:
26、 FPP (n, W, ) 1% That is, the floor packet percentage must exceed 1%. This means that for any window interval of 200 s at least 1% of transmitted timing packets will be received within a fixed cluster, starting at the observed floor delay and having a range of 150 s. 2 Rec. ITU-T G.8261.1/Y.1361.1 (
27、2012)/Amd.1 (05/2014) NOTE 1 The selection method (using sliding, overlapping or jumping windows) applicable to the network limit specified in this Recommendation is for further study. NOTE 2 The number of packets received within the fixed cluster range depends on the nominal packet rate. For exampl
28、e, with a nominal packet rate of one packet per second, FPP 1% implies that two or more packets will be received within the fixed cluster range in each 200 s interval. The number of packets in a selection window is important for considering the tolerance limit of a slave clock. For more details on t
29、he measurement methodology refer to clause I.5 of ITU-T G.8260. This network limit can be applied independently on the forward or the reverse direction of a packet timing flow. Consideration of the combined effect of both directions is for further study. Other PDV metrics emulating the behaviour of
30、a packet slave clock are currently under study and might be used in the future for specifying the PDV network limits in a less conservative way. Some information can be found in clause I.4 of ITU-T G.8260. NOTE 3 A packet slave clock tolerating this PDV limit is defined in ITU-T G.8263. 8.1.2 Networ
31、ks with lower packet delay variation Clause 8.1.1 specifies the network limit for HRM-1. Many HRM-1 networks may exhibit much lower packet delay variation than indicated by this limit and therefore it is considered very conservative. For instance, some measurements on HRM-1 networks show that FPP (n
32、, W, ) 1% is respected when considering = 75 s. This corresponds to a scenario where the PDV generated by the traffic carried over the network is engineered according to certain rules for transport networks. The rules to meet this network performance are for further study. Nevertheless, networks tha
33、t are designed to meet the requirement specified in clause 8.1.1 need not be changed. To accommodate exceptional conditions (e.g., infrequent congestion (overload) of multiple links simultaneously), the FPP (n, 200, 75 s) may not be met within the following constraints when: there are no more than 4
34、 periods over a 24 hour duration where there are less than 1% of packets within the 75 s FPP cluster range (these are termed “congestion periods“); there are at least 900 seconds between the end of a congestion period and the start of the next congestion period; and an individual congestion period d
35、oes not exceed 200 seconds in length; and the PDV network limit of HRM-1 is still satisfied during all periods of the measurement, including during the periods of congestion (i.e., FPP(n,200,150 s) =1%). It is the responsibility of the operator to decide if its network fits within this scenario. NOT
36、E A packet slave clock optimized for these networks but not tolerating the PDV limits defined in clause 8.1.1 is for further study 8.2 HRM-2 network limit The packet delay variation network limits for the HRM-2 are for further study. For HRM-2, different limits may apply, and may use different metri
37、cs. ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Network aspects Y.300Y.399 Interfaces and protocols Y.400Y.499 Numbering,
38、 addressing and naming Y.500Y.599 Operation, administration and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800Y.899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applications Y.1100Y.1199 Architecture, access, network capabilities and resource management Y.1200Y.1299 Tra
39、nsport Y.1300Y.1399 Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599 Signalling Y.1600Y.1699 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 IPTV over NGN Y.1900Y.1999 NEXT GENERATION NETWORKS Frameworks and functional architecture models
40、 Y.2000Y.2099 Quality of Service and performance Y.2100Y.2199 Service aspects: Service capabilities and service architecture Y.2200Y.2249 Service aspects: Interoperability of services and networks in NGN Y.2250Y.2299 Enhancements to NGN Y.2300Y.2399 Network management Y.2400Y.2499 Network control ar
41、chitectures and protocols Y.2500Y.2599 Packet-based Networks Y.2600Y.2699 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 Carrier grade open environment Y.2900Y.2999 FUTURE NETWORKS Y.3000Y.3499 CLOUD COMPUTING Y.3500Y.3999 For further details, please refer to the list of ITU-T Recommendatio
42、ns. Printed in Switzerland Geneva, 2014 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecommunication services Series G
43、Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia signals Series K Protection against interference Series L
44、 Construction, installation and protection of cables and other elements of outside plant Series M Telecommunication management, including TMN and network maintenance Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipmen
45、t Series P Terminals and subjective and objective assessment methods Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks, open system communications and security Series Y Global information infrastructure, Internet protocol aspects and next-generation networks Series Z Languages and general software aspects for telecommunication systems
