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1、 CEA Standard QoS Priority Groupings for 802.1Q CEA-2007 November 2003 Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 21:46:02 MDTNo reproduction or networking permitted without license
2、 from IHS -,-,- NOTICE CEA Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting
3、 and obtaining with minimum delay the proper product for his particular need. Existence of such Standards, Bulletins and other technical publications shall not in any respect preclude any member or nonmember of CEA from manufacturing or selling products not conforming to such Standards, Bulletins or
4、 other technical publications, nor shall the existence of such Standards, Bulletins and other technical publications preclude their voluntary use by those other than CEA members, whether the standard is to be used either domestically or internationally. Standards, Bulletins and other technical publi
5、cations are adopted by CEA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, CEA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard, Bulletin or other technical publication. T
6、his CEA Standard is considered to have International Standardization implication, but the International Electrotechnical Commission activity has not progressed to the point where a valid comparison between the CEA Standard and the IEC document can be made. This Standard does not purport to address a
7、ll safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. (From Project Number 2035, for
8、mulated under the cognizance of the CEA R7.5 A/V Network Subcommittee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2002 Technology 3 of the groups represent service models, and the fourth group is for critical network management. This standard does not specify how to implement QoS policies in the
9、 groupings. Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 21:46:02 MDTNo reproduction or networking permitted without license from IHS -,-,- Quality of Service Priority Groupings for 8
10、02.1Q 2 2. REFERENCES 2.1 Normative 1 IEEE 802.1Q Local and Metropolitan Area Networks: Virtual Bridged Local Area Networks 2 ANSI/IEEE Std 802.1D, 1998 Local and Metropolitan Area Networks: Media Access Control (MAC) Bridges 2.2 Informative 1 802-2001 IEEE Standard for Local and Metropolitan Area N
11、etworks: Overview and Architecture 2 RFC 2815 Integrated Service Mappings on IEEE 802 Networks 3 RFC 2814 A Protocol for RSVP-based Admission control over IEEE 802-style networks 4 RFC 2816 Framework for Int-Serv Over IEEE 802 LAN, May 2000 5 DVB-IPI2001-072r04, Ethernet Home Network Segment, May 3,
12、 2002, DRAFT 2.3 Reference Acquisition IEEE Standards Institute of Electrical and Electronics Engineers, 3 Park Avenue, 17th Floor, New York, New York, 10016-5997 U.S.A.; Tel: +1 212 419 7900; Fax: +1 212 752 4929 URL: www.ieee.org IETF Documents Internet Engineering Task Force (IETF) Secretariat, c
13、/o Corporation for National Research Initiatives, 1895 Preston White Drive, Suite 100, Reston, VA 20191-5434, USA; (703) 620- 8990 / (703) 620-9071 (FAX) URL: www.ietf.org, IETF RFCs may be downloaded from www.ietf.org/rfc.html DVB Standards Digital Video Broadcasting, DVB Project Office, 17a Ancien
14、ne Route, CH-1218 Grand Saconnex, Geneva, Switzerland, Phone +41 22 717 27 19, Fax: +41 22 717 27 27 URL: www.dvb.org, E-mail: dvbdvb.org Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007
15、21:46:02 MDTNo reproduction or networking permitted without license from IHS -,-,- CEA-2007 3 3. DEFINTIONS 3.1 Terms Best Effort A general method of accessing a network to deliver a message. Best effort access is not guaranteed, and therefore the message may not get delivered. Many communication pr
16、otocols use this approach. Best Effort is typically the default grade of service provided in a network when no specific QoS is requested Parameterized Services Parameterized services refer to a general methodology for obtaining QoS. A Contract is made with the network using a set of parameters, whic
17、h define the applications traffic requirements. The parameters typically include bandwidth and delay among others. Prioritized Services Prioritized services refer to a general methodology for obtaining QoS by differentiating traffic. Message types are grouped in order of importance and assigned a pr
18、iority. Message types assigned a higher priority are given preferential access to the network. There are no limits to the number of messages using a given priority, and the bandwidth of the network may be less than the bandwidth of the messages. Quality of Service (QoS) The term QoS refers to a broa
19、d collection of networking technologies and techniques. The goal of QoS is to provide guarantees on the ability of a network to deliver predictable results. Elements of network performance within the scope of QoS often include availability (uptime), bandwidth (throughput), latency (delay), and error
20、 rate 3.2 Acronyms SNMP Simple Network Management Protocol TCP Transmission Control Protocol 3.3 Conventions The requirements and specifications for this standard adhere to the following conventions: 1. Features or functions that are necessary to implement this standard are identified by the word sh
21、all in bold type. Failure to adhere to a feature or function identified by shall might cause application restrictions, result in improper functioning, or hinder operations. For a device to be compliant with this standard it must implement all features or functions identified by shall. Copyright Cons
22、umer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 21:46:02 MDTNo reproduction or networking permitted without license from IHS -,-,- Quality of Service Priority Groupings for 802.1Q 4 2. Features or fun
23、ctions that are desirable, but that are not necessary to implement this standard are identified by the word should in bold type. Failure to adhere to a feature or function identified by should might inhibit the implementation of some features or functions in specific applications or environments. 3.
24、 Features or functions that are optional and not needed to implement this standard, are identified by the word may in bold type. Such features or functions represent goals to be achieved, and might enhance the convenience and utility of this standard. The letters TBD represent the words “to be deter
25、mined,” and indicate that further requirements or specifications are expected to be included in future issues of this standard Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 21:46:02 MD
26、TNo reproduction or networking permitted without license from IHS -,-,- CEA-2007 5 4. IEEE 802.1Q and the Priority Field 4.1 IP Ethernet Frame Structure For reference purposes, below is the standard Ethernet Frame. Destination Address Source Address Ethertype/Length Data FCS In 802.1Q a Tag field ha
27、s been inserted as follows: The Tag Field includes the following (highlighted) fields: 48 bits 48 bits 16 bits 3 bits 1 bits 12 bits 16 bits Variable 32 bits DA SA TPID Priority 0-7 CFI VLAN ID Length/Type Data with PAD FCS The Priority field is 3 bits. This standard defines the use of the priority
28、field only. For the definitions and use of other fields see normative reference 1 Destination Address Source Address Ethertype/Length Data FCS Tag Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03
29、/30/2007 21:46:02 MDTNo reproduction or networking permitted without license from IHS -,-,- Quality of Service Priority Groupings for 802.1Q 6 5. Priority Allocation and Grouping This standard assigns groupings to the 802.1Q Priority field. The priority field is logically divided into 4 groups: 1. N
30、etwork Management highest priority 2. Parameterized (Managed) QoS -2nd highest priority 3. Prioritized (Unmanaged) QoS 3rd highest priority 4. Best Effort lowest priority Network management traffic is allocated the highest priority level. Network management commands use this priority to ensure that
31、network bandwidth and resources can be recovered. The second group, parameterized QoS, ensures that devices which have allocated resources throughout the network have first access to the network. The third group, prioritized QoS, benefits from using priority to gain access to the network but paramet
32、erized services still has a higher priority. Best Effort is low priority, and its traffic is restricted to the availability of the network after all higher priority traffic has been sent. The lowest priority is used when non- priority packets are converted to 802.1Q packets. As a default, these pack
33、ets are mapped to the lowest 802.1Q priority setting. Table 5-1 shows the priority groups, service type and the priority value: Table 5-1 802.1Q Priority Groupings for AV supported networks Priority Group Service Type Service Level (Attributes) Typical Application Priority (3-bit) Examples (non-exha
34、ustive) 1) Highest Network Management Critical controls Critical controls 111 SNMP Stream Management Connection control Connection control 110 Stream setup and control(play, stop) 2) 2nd highest Parameterized Very low latency therefore they are given a higher priority over latency-tolerant applicati
35、ons. Note that control packets for both parameterized and prioritized use the higher priority “stream management” category to ensure that streams can be taken down (“livelock“ avoidance). The priority field bit map is defined to optimize hardware queue mapping for switches that implement less than e
36、ight output queues. Annex A discusses output queue mapping. Annex B discusses in more detail how typical home network applications would choose the appropriate priority setting. NOTE: The above priority groupings represent use of the 802.1Q priority field that is consistent with 802.1d user prioriti
37、es. In the home network, the consumer will ultimately choose what content is of most importance. Thus, this standard sets a default starting point for QoS services in the home network that can be overridden. Overriding the default priority mapping is an upper layer function (above layer 3) and is no
38、t addressed by this standard. Copyright Consumer Electronics Association Provided by IHS under license with CEA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 21:46:02 MDTNo reproduction or networking permitted without license from IHS -,-,- Quality of Service Priori
39、ty Groupings for 802.1Q 8 Annex A Ethernet Switch Requirements for Handling Priority Packets (Normative) IEEE 802.1Q specifies eight levels of priority, and it is expected that Ethernet hardware supporting 802.1Q includes a separate output queue for each priority level. However, when reduced hardwar
40、e complexity is desired, there may be fewer hardware queues available than priority levels. Table A-1 shows how the Table 5-1 priority groupings map to a reduced number of hardware queues. Table 5-1 priority mappings are chosen to map to simple hardware decoder algorithms (modulus base-2 reduction).
41、 Service Mappings to Priority Level (User Priority level in 802.1d) # of Queues 111 110 101 100 011 000 010 001 1 All services 2 Control and Parameterized Prioritized and Best Effort 4 Control Parameterized Prioritized Best Effort 8 (per Table 5-1) Network Management Stream Management Parameterized
42、2 Way Parameterized 1 Way Prioritized 2 Way Prioritized 1 Way Best Effort Default Table A- 1 Hardware Queue Mapping to Priority Levels This service mapping is designed to be compatible with switches that use 802.1d. Copyright Consumer Electronics Association Provided by IHS under license with CEA Li
43、censee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 21:46:02 MDTNo reproduction or networking permitted without license from IHS -,-,- CEA-2007 9 Annex B Guidelines for Priority Assignment (Informative) Table 5-1 includes examples of applications with an underlying assumpti
44、on that the applications start and terminate on Ethernet. However, home networks are expected to contain differing network technologies. For example, a home network may contain a cluster of 1394 AV devices, an Ethernet backbone, and an 802.11e wireless access point (connected to the Ethernet backbon
45、e). In this case, both 1394 and 802.11e support parameterized services. Thus, a unidirectional AV stream, i.e. a TV show, originating on a 1394 set top box and ending on wireless 802.11e could have parameters allocated on 1394 and 802.11e as part of the stream setup. In this case, the recommended Et
46、hernet mapping should use the low latency Parameterized priority service to meet the QoS expectations across the overall network. If in the above scenario the AV stream originated from an Ethernet device that does not implement parameterized services, then the recommended priority mapping is low lat
47、ency prioritized service. However, if an application is able to gain knowledge of the stream parameters, and it is capable of implementing 802.11e parameter allocation, then the application could override the prioritized service level and select the parameterized service level. The permutations of n
48、etwork technologies and their levels QoS support make it extremely difficult to make exacting rules of QoS service mappings on Ethernet. Therefore, “Rules of Thumb” are included as a guide for mapping applications and technologies to QoS service levels on Ethernet. They are: If parameters are allocated on any part of the network, and therefore network QoS expectations are implied, then Parameterized service levels should be used on the Ethernet portion of the network. If no parameterization is possible, but the