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 L.1321 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2015) SERIES L: CONSTRUCTION, INSTALLATION AND PROTECTION OF CABLES AND OTHER ELEMENTS OF OUTSIDE PLANT Reference operational model and interface for improving ener
2、gy efficiency of ICT network hosts Recommendation ITU-T L.1321 Rec. ITU-T L.1321 (03/2015) i Recommendation ITU-T L.1321 Reference operational model and interface for improving energy efficiency of ICT network hosts Summary Recommendation ITU-T L.1321 describes a reference operational model and inte
3、rface for improving energy efficiency of ICT network hosts. The operational model and interface specify network proxy operation to support IPv4 ARP and DHCP in order to promote the deployment of network proxy. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T L.1321 2015-03-01
4、 5 11.1002/1000/12429 _ * 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. ii Rec. ITU-T L.1321 (03/2015) FOREWORD The International Telecommu
5、nication 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 permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff
6、 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, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommend
7、ations 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 standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendat
8、ion, 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 Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperabilit
9、y 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 equivalents are used to express requirements. The use of such words does not suggest that complia
10、nce with the Recommendation 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 o
11、r 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 not received notice of intellectual property, protected by patents, which may be required t
12、o 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/ipr/. ITU 2015 All rights reserved. No part of this publication may be reproduced, by
13、 any means whatsoever, without the prior written permission of ITU. Rec. ITU-T L.1321 (03/2015) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 1 4 Abbreviations and acronyms 1 5 Conventions 2 6 Referenc
14、e operational model and interface for improving energy efficiency of ICT network hosts 2 6.1 Overview of energy management for ICT network hosts 2 6.2 Reference operational model for delegating network connectivity maintenance 3 6.3 Network protocols for network connectivity maintenance delegation .
15、 4 7 Operation interface for energy efficient network host management 4 7.1 Operation interface for network host management 4 8 Security considerations . 6 Bibliography. 7 Rec. ITU-T L.1321 (03/2015) 1 Recommendation ITU-T L.1321 Reference operational model and interface for improving energy efficie
16、ncy of ICT network hosts 1 Scope This Recommendation specifies a reference model for improving energy efficiency of wired network hosts so that network hosts can reduce energy consumption by entering an energy saving sleep state. This Recommendation describes the specification for improving energy e
17、fficiency by defining a reference operational model of a network proxy to handle mandatory protocols for network hosts in the sleep state. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Rec
18、ommendation. 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 encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other refe
19、rences listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Y.3021 Recommendation ITU-T Y.3021 (2012), Framework of energy sa
20、ving for future networks. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following term defined elsewhere: 3.1.1 network proxy b-ECMA 393: An entity that maintains network presence for a sleeping higher-power host. 3.2 Terms defined in this Recommendation This Recommendation
21、defines the following terms: 3.2.1 host: An entity that uses a network proxy functionality for maintaining network presence in a lower power state. 3.2.2 sleep: The state in which the host uses less energy than it does when fully operational. 4 Abbreviations and acronyms This Recommendation uses the
22、 following abbreviations and acronyms: ACK Acknowledgement ARP Address Resolution Protocol DHCP Dynamic Host Configuration Protocol ICMP Internet Control Message Protocol ICT Information and Communication Technology IP Internet Protocol 2 Rec. ITU-T L.1321 (03/2015) LAN Local Area Network MAC Media
23、Access Control NACK Negative ACK NIC Network Interface Card UDP User Datagram Protocol 5 Conventions None. 6 Reference operational model and interface for improving energy efficiency of ICT network hosts 6.1 Overview of energy management for ICT network hosts The information and communications techn
24、ology (ICT) sector is facing rapid growth and consuming a lot of power in order to provide large bandwidth and complex application services. According to b-ITU-T CC Report, wired and wireless networks consume large amount of power and the amount of green-house gas emissions caused by ICT sector is e
25、stimated 2% of total man-made emissions. It is also estimated that network sector, including network equipment and equipment connected to networks, contributes 4% of world power consumption. Further, it is observed that the power consumption is higher at access networks and users, so how to reduce t
26、he power consumption in these areas is becoming an important issue. According to recent surveys, network equipment shows a constant power consumption profile irrespective of their utilization level, i.e., an energy-agnostic power profile. Such equipment represents the worst case in terms of utilizat
27、ion and power consumption profile. On the contrary, ideally, energy-aware equipment represents a power consumption pattern proportional to their utilization or offered load. Practical approaches for realizing the energy-aware equipment are implementing multi-stepped power profiles in order to adapt
28、to the utilization level b-IEEE Computer b-IEEE Comm Sur b-IEEE 802.3az. There is another research direction for improving energy efficiency of network equipment using network proxy technology b-IETF EEI b-ECMA 393 b-IEEE IPCCC. Network proxy describes technologies that maintain network connectivity
29、 on behalf of other devices so that these can go into low power sleep states. This mainly targets the reduction of unnecessary energy waste through edge devices. There are typically two types of network proxies: internal and external, respectively. Internal Proxy: proxy functionality is implemented
30、within the ICT equipment such as network interface card. External Proxy: proxy functionality is placed within other network equipment such as a switch or external server in a network. The European Computer Manufacturers Association (ECMA) International has published specification b-ECMA 393 that des
31、cribes an overall architecture for network proxies and provides capabilities that a proxy may expose to a host. Also, information that must be exchanged between a host and a proxy, and required and optional behaviour of a proxy during its operation are described. A generalized network proxy is capab
32、le of providing full network presence for a broad range of network protocols and applications. The generalized network proxy includes a list of packet types that may require routine reply, auto-generation, and wakeup, as well as the detailed steps and methods for state information transfer each requ
33、ires b-Ether Alliance. It is well known that many network hosts are in an active state in order to maintain network presence and this behaviour hinders hosts from entering an energy saving state. Even when a node is idle with Rec. ITU-T L.1321 (03/2015) 3 no running applications, background traffic
34、is received and processed, which inhibits the node from sleeping. The use of a network proxy is one of the possible solutions to resolve this issue. The general framework for a network proxy was developed, but the control interface and operational model between network hosts and network proxies to h
35、andle incoming packets destined to network hosts in sleep state have not been developed. Thus, in order to promote the wider deployment of the network proxy mechanism, the control interface and operational model of a network proxy to handle protocols on behalf of network hosts in sleep state should
36、be specified. This Recommendation describes a reference operational model and interface that is needed for communication between a network proxy and network nodes. The interface and operation model for network proxy operation and relevant messages can be used to increase energy efficiency of network
37、 hosts. 6.2 Reference operational model for delegating network connectivity maintenance Network proxy refers to a set of mechanisms dedicated to put network interfaces and network hosts into an energy saving sleep state, which is a management method used by energy efficient network hosts. Energy con
38、sumption of network host in a sleep state is less than in an active state in general, so the longer the sleep period, the higher the achievable energy saving can be. A network proxy is a technology that delegates some networking functions in network hosts to other network elements such as external n
39、odes or other modules in the nodes. The network proxy enables the network hosts to maintain network connectivity during the sleep state. Figure 1 shows the typical operational scenario of network proxy. When a sleeping host wants to enter energy saving sleep state, the host delivers its network stat
40、us and state to a network proxy and goes into sleep state. Then, the network proxy responds to periodic messages on behalf of the host in the sleep state. If the proxy receives a message that it cannot process, it sends a wake-up message to the host so that the host can process the message after wak
41、e-up. It is noted that this Recommendation specifies the operational model and interfaces between a network proxy and other network nodes in Figure 1. The specification for operations between the sleeping host and network proxy are out of scope of this Recommendation. Figure 1 Reference operational
42、model for delegating network connectivity maintenance 4 Rec. ITU-T L.1321 (03/2015) 6.3 Network protocols for network connectivity maintenance delegation The following list summarizes the requirement status about what types of protocols a network proxy should support b-ECMA 393. Among them, this Rec
43、ommendation describes address resolution protocol (ARP) and dynamic host configuration protocol (DHCP) related operation as mandatory protocols for rapid deployment. Mandatory 1: Media (IEEE 802.3) b-IEEE 802.3 Mandatory 2: IPv4 ARP b-IETF RFC 826 Mandatory 3: Wake packets b-Magic Pkt Mandatory 4: D
44、HCP b-IETF RFC 2131 Regarding wake packets among mandatory protocols, this Recommendation recommends to use “Magic Packet“ over UDP. It broadcasts a UDP packet containing synchronization stream and the target MAC address of sleeping host. The synchronization stream is expressed as a six-byte hexadec
45、imal value. After that, 16 duplications of the target MAC address are appended. The packet format of “Magic Packet“ over UDP is as follows: Destination IP address: 255.255.255.255 UDP data: 0xFF FF FF FF FF FF Target MAC 16 duplications Those mandatory protocols are typically used within local area
46、network (LAN) environment, so this Recommendation is applicable to a LAN environment. Extending the applicability of this Recommendation to other environment such as enterprise networks and wide area networks are not within the scope of this Recommendation and extending the applicability requires fu
47、rther investigation on security and network administration issues. 7 Operation interface for energy efficient network host management 7.1 Operation interface for network host management Figure 2 depicts network proxy operation for IPv4 ARP. A sleeping host performs discovery procedures to detect the
48、 network proxy and proxy capability. After the discovery procedure, the host and discovered network proxy exchange ARP configuration information including the hosts media access control (MAC) address(es) and IP address(es) so that the host can enter a sleep state. Then the network proxy discards ARP
49、 Request messages broadcast from other nodes in the network. By doing so, the sleeping host can sleep without receiving or processing ARP broadcast message not destined to the sleeping host itself. If the network proxy receives an ARP request message for the sleeping host, it sends a wake packet to wake up the sleeping host. Since IP packets are followed by ARP request message that resolves the sleeping hosts IP address and MAC address, the network proxy initiates a wake-up procedure on receivin
