1、 International Telecommunication Union ITU-T Y.1222TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2007) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Architecture, access, network capabilities and resource managemen
2、t Traffic control and congestion control in Ethernet-based networks ITU-T Recommendation Y.1222 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 mid
3、dleware Y.200Y.299 Network aspects Y.300Y.399 Interfaces and protocols Y.400Y.499 Numbering, 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.11
4、00Y.1199 Architecture, access, network capabilities and resource management Y.1200Y.1299 Transport 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 NEXT
5、GENERATION NETWORKS Frameworks and functional architecture models 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 Numbering, naming
6、and addressing Y.2300Y.2399 Network management Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. Y.1222 (11/2007) i ITU-T Recommendation Y.12
7、22 Traffic control and congestion control in Ethernet-based networks Summary ITU-T Recommendation Y.1222 provides a general description of and procedures for traffic control and congestion control in Ethernet-based networks. It describes the concepts of the traffic contract between a user and the ne
8、twork. It specifies the Ethernet transfer capabilities (ETCs) including, for each ETC, the service model, the associated traffic patterns and conformance definition for an Ethernet flow that are observable at any point in the network. Source ITU-T Recommendation Y.1222 was approved on 13 November 20
9、07 by ITU-T Study Group 12 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. Y.1222 (11/2007) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs).
10、 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 issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Sta
11、ndardization 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 topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of informati
12、on 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 expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.
13、Compliance with this Recommendation is voluntary. However, the 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
14、 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 Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or impleme
15、ntation 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 the Recommendation development process.
16、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, implementers are cautioned that this may not represent the latest information and are therefore strongly urg
17、ed to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2008 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. Y.1222 (11/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terminol
18、ogy . 1 4 Abbreviations 2 5 Convention 3 6 Introduction 3 7 Traffic parameters and descriptors . 4 7.1 Definitions 4 7.2 Requirements on traffic parameters and traffic descriptors . 5 7.3 Traffic parameter specifications. 5 8 Ethernet transfer capabilities 6 8.1 Dedicated bandwidth (DBW) transfer ca
19、pability. 6 8.2 Statistical bandwidth (SBW) transfer capability 7 8.3 Best effort (BE) transfer capability 7 9 Functions for traffic control, congestion control and overload treatment 8 9.1 Traffic control functions. 8 9.2 Functions for congestion control and overload treatment 9 ITU-T Rec. Y.1222 (
20、11/2007) 1 ITU-T Recommendation Y.1222 Traffic control and congestion control in Ethernet-based networks 1 Scope This Recommendation describes traffic control and congestion control procedures for Ethernet-based networks. Traffic control refers to all network actions aiming to meet the negotiated pe
21、rformance objectives and negotiated QoS commitments in an Ethernet-based network, and to avoid congested conditions. Congestion control refers to all network actions to minimize the intensity, spread and duration of congestion. This Recommendation provides a general description of and procedures for
22、 traffic control and congestion control. It describes the concepts of the traffic contract between a user and the network. It specifies the Ethernet transfer capabilities (ETCs) including, for each ETC, the service model, the associated traffic patterns and conformance definition for an Ethernet flo
23、w that are observable at any point in the network. 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 Recommen
24、dations and other 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 pu
25、blished. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T I.371 ITU-T Recommendation I.371 (2004), Traffic control and congestion control in B-ISDN. ITU-T Y.1221 ITU-T Recommendation Y.1221 (2002), Traffic contr
26、ol and congestion control in IP-based networks. Metro Ethernet Metro Ethernet Forum Technical Specification 10.1 (2006), Ethernet Services Attributes Phase 2. IEEE 802.3 IEEE 802.3 (2005), IEEE Standard for information technology Telecommunications and information exchange between systems Local and
27、metropolitan area networks Specific requirements Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications. 3 Terminology For the purposes of this Recommendation, the following terminology applies: 3.1 conformance: Conformance is the app
28、lication of one or more criteria, at a given standardized interface, to a flow. 3.2 congestion: Congestion is defined as a state of network elements (e.g., switches) in which the network is not able to meet the network performance objectives and the negotiated QoS commitments for the already establi
29、shed flow. 3.3 Ethernet flow: An Ethernet flow at a given interface is defined as the occurrence at that interface of the set of Ethernet frames which match a given classification (see clause 7.1.2). 2 ITU-T Rec. Y.1222 (11/2007) 3.4 Ethernet traffic control: Refers to network actions aiming to meet
30、 the network performance objectives and negotiated QoS commitments. 3.5 Ethernet congestion control: Refers to all network actions to minimize the intensity, spread and duration of congestion. 3.6 Ethernet transfer capability: An Ethernet transfer capability is a set of network capabilities provided
31、 by Ethernet-based network to transfer Ethernet flows. 3.7 overload: Overload is defined as a state of network elements in which buffer overflow results in frame discard for flows with no QoS commitments. 3.8 packet classification: The process of distinguishing Ethernet frames for the purpose of app
32、lying appropriate traffic control and congestion control mechanisms is called Ethernet frame classification (see clause 7.1.1). 3.9 traffic contract: For a given Ethernet flow, the selected Ethernet transfer capability (see clause 8), the traffic descriptor at a given interface and the QoS class def
33、ine the traffic contract at that interface. See clause 7.1.5. 3.10 traffic descriptor: A traffic descriptor is the set of traffic parameters that is used to capture the traffic characteristics of an Ethernet flow at a given standardized interface as part of the traffic contract. See clause 7.1.4. 3.
34、11 traffic parameter: A traffic parameter describes one aspect of a flow. See clause 7.1.3. 4 Abbreviations This Recommendation uses the following abbreviations: B Bucket size of a token bucket Bc Bucket size of committed token bucket BCB Backbone Core Bridge BE Best Effort Be Bucket size of excess
35、token bucket BEB Backbone Edge Bridge B-TAG Backbone VLAN TAG CBS Committed Burst Size CF Coupling Flag CM Colour Mode CIR Committed Information Rate C-TAG Custom VLAN TAG DBW Dedicated Bandwidth EBS Excess Burst Size EIR Excess Information Rate ETC Ethernet Transfer capability GBRA Generic Byte Rat
36、e Algorithm I-TAG Service instance TAG LAN Local Area Network ITU-T Rec. Y.1222 (11/2007) 3 M Maximum allowed frame size MAC Media Access Control MEF Metro Ethernet Forum PBN Provider Bridged Network PBBN Provider Backbone Bridged Network PC Parameter Control PVID Port VLAN ID QoS Quality of Service
37、 R Rate of a token bucket Rc Rate of committed token bucket Re Rate of excess token bucket SBW Statistical Bandwidth S-TAG Service VLAN TAG TB Token Bucket TC Transfer Capability VID VLAN Identifier 5 Convention None. 6 Introduction The primary role of traffic control and congestion control procedur
38、es is to protect the Ethernet network and the traffic entering the network in order to achieve the Ethernet network performance objectives and QoS commitments. Traffic and congestion control allows the use of Ethernet network resources to be optimized. In Ethernet-based networks, congestion is defin
39、ed as a state of network elements (e.g., switches) in which the network is not able to meet the network performance objectives and the negotiated QoS commitments for the established flow. Congestion is to be distinguished from the state where buffer overflow causes Ethernet frame loss, but the negot
40、iated quality of service is still met. For services with no QoS commitments such as best effort services, the term overload is used rather than congestion. This Recommendation defines a set of traffic control and congestion control capabilities. It may be appropriate to consider additional sets of s
41、uch capabilities, for which additional traffic control mechanisms will be used to achieve increased network efficiency. This Recommendation also specifies a set of Ethernet transfer capabilities (ETCs) including, for each ETC, the service model, the associated traffic patterns and conformance defini
42、tion for an Ethernet flow that are observable at any point in the network. 4 ITU-T Rec. Y.1222 (11/2007) 7 Traffic parameters and descriptors 7.1 Definitions 7.1.1 Ethernet frame classification For the purpose of Ethernet traffic control and congestion control, it is essential that not all Ethernet
43、frames are treated the same way but differently, depending on the objectives and on the commitments made. Therefore, it is useful to classify Ethernet frames into different categories. Ethernet frame can be classified based on information in the Ethernet frame header fields, such as priority, VID, s
44、ource MAC address and destination MAC address. The level of detail in the classification may be different, which depends on its intended use. Usually, the classification can be done as follows: In order to recognize Ethernet frames which are with a given priority in a given VLAN, the priority field
45、and VID field in the corresponding TAG field (C-TAG in IEEE 802.1Q LAN, S-TAG in 802.1ad PBN, I-TAG for BEB and B-TAG for BCB in 802.1ah PBBN) are used in the classification. In order to recognize Ethernet frames which flow from a given source MAC address to a given destination MAC address in a give
46、n VLAN with a given priority, the source and destination address fields, the priority field and VID field in the corresponding TAG field (C-TAG in IEEE 802.1Q LAN, S-TAG in 802.1ad PBN, I-TAG for BEB and B-TAG for BCB in 802.1ah PBBN) are used in the classification. For the 802.1D LAN, the VID corre
47、sponds to the PVID, and the priority corresponds to the port default priority. In some conditions, according to different applications, there may be other modes for the classification. 7.1.2 Ethernet flow An Ethernet flow at a given interface is defined as the occurrence at that interface of the set
48、 of Ethernet frames which match a given classification (see clause 7.1.1). 7.1.3 Traffic parameter A traffic parameter is a specification of a particular traffic aspect. It may be qualitative or quantitative. Traffic parameters may, for example, describe peak bit rate, average bit rate, the average
49、or maximum frame size, etc. 7.1.4 Traffic descriptor A traffic descriptor is the set of traffic parameters which can be used to capture the traffic characteristics of an Ethernet flow at a given standardized interface as part of the traffic contract (see clause 7.1.5). 7.1.5 Traffic contract For a given Ethernet flow, the selected Ethernet transfer capability (see clause 8), the traffic descriptor at a given interface (see clause 7.1.4) and the associated QoS class define the traffic contract at that interface. ITU-T Rec. Y.1222 (11/2007) 5 7.2
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