1、 International Telecommunication Union ITU-T Y.2053TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2008) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Next Generation Networks Frameworks and functional architecture models Functional requireme
2、nts for IPv6 migration in NGN Recommendation ITU-T Y.2053 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.3
3、00Y.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.1100Y.1199 Architecture, access, network
4、 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 GENERATION NETWORKS Frameworks and fun
5、ctional 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 and addressing Y.2300Y.2399 Network ma
6、nagement 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. Rec. ITU-T Y.2053 (02/2008) i Recommendation ITU-T Y.2053 Functional requirements for IPv6 mi
7、gration in NGN Summary Recommendation ITU-T Y.2053 provides feasible IPv6 migration scenarios and functional requirements necessary for them. Source Recommendation ITU-T Y.2053 was approved on 29 February 2008 by ITU-T Study Group 13 (2005-2008) under Recommendation ITU-T A.8 procedure. Keywords IPv
8、4, IPv6, migration, NGN ii Rec. ITU-T Y.2053 (02/2008) 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
9、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 Standardization Assembly (WTSA), which meets every four years, e
10、stablishes 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
11、 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, th
12、e 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 equivale
13、nts 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 implementation of this Recommendation may involve the use of a claim
14、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 no
15、t 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 urged to consult the TSB patent database at http:/www.itu.int/IT
16、U-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. Rec. ITU-T Y.2053 (02/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this
17、 Recommendation. 2 4 Abbreviations and acronyms 2 5 Conventions 2 5.1 Native IPv6 device . 2 5.2 IPv6 transition mechanism . 2 5.3 Basic IPv6 transition mechanisms 2 6 IP as a transport function of NGN 2 7 Basic approaches for interworking and migration 3 7.1 Dual IP layer (Dual stack) 3 7.2 Configu
18、red tunnelling. 3 7.3 Network address translation and protocol translation 3 8 Migration scenarios 4 8.1 CASE 1 3 (NAT-PT cases) . 6 8.2 CASE 4 7 (configured tunnelling cases) . 6 8.3 CASE 8 (NAT-PT case) . 6 8.4 CASE 9 (configured tunnelling cases) . 7 8.5 CASE 10 11 (dual stack cases) . 7 8.6 CASE
19、 12 (native IPv6 case). 7 9 Functional requirements for IPv6 migration at transport stratum 7 9.1 Transport stratum functions 7 9.2 End-user functions 12 9.3 Other non-NGN network functions 12 10 Security considerations. 12 Appendix I IPv6 migrations in NGN 13 I.1 IPv6 transition mechanisms 13 I.2 E
20、xample migration scenarios according to Table 1 . 15 Bibliography 20 Rec. ITU-T Y.2053 (02/2008) 1 Recommendation ITU-T Y.2053 Functional requirements for IPv6 migration in NGN 1 Scope The objective of this Recommendation is to identify IPv6 migration scenarios and functional requirements necessary
21、for them. NGN transport stratum provides IP connectivity services to NGN users, but the current NGN assumes no specific version of IP. It means that IPv4 and IPv6 could coexist in NGN while IPv4 is being replaced with IPv6. So the interim solution like IPv6 transition mechanism (see clauses 6 and 7)
22、 is required for this period. If the IPv6 transition mechanism is introduced to NGN, there could be various migration scenarios satisfying various applications requirements or service providers requirements, and these migration scenarios will also impact on existing FEs of NGN. Thus, this Recommenda
23、tion provides feasible IPv6 migration scenarios, and functional requirements required to support each scenario. 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
24、 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 references listed below. A list
25、 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.2011 Recommendation ITU-T Y.2011 (2004), General principles and general reference model fo
26、r Next Generation Networks. ITU-T Y.2012 Recommendation ITU-T Y.2012 (2006), Functional requirements and architecture of the NGN release 1. ITU-T Y.2111 Recommendation ITU-T Y.2111 (2006), Resource and admission control functions in Next Generation Networks. ITU-T Y.2701 Recommendation ITU-T Y.2701
27、(2007), Security requirements for NGN release 1. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 host b-ITU-T Y.1540: A computer that communicates using the Internet protocols. A host implements routing functions (i.e., it operates at t
28、he IP layer) and may implement additional functions including higher layer protocols (e.g., TCP in a source or destination host) and lower layer protocols (e.g., ATM). 3.1.2 router b-ITU-T Y.1540: A host that enables communication between other hosts by forwarding IP packets based on the content of
29、their IP destination address field. 2 Rec. ITU-T Y.2053 (02/2008) 3.1.3 dual IP layer b-IETF RFC 4213: Dual IP layer is a technique for providing support for both Internet Protocols IPv4 and IPv6 in a node. Dual IP layer is also known as dual stack. 3.1.4 configured tunneling b-IETF RFC 4213: The co
30、nfigured tunneling is a technique for establishing point-to-point tunnels by encapsulating IPv6 packets within IPv4 headers to carry them over IPv4 infrastructures (or vice versa). 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 node: A node is a devic
31、e that is connected as part of a computer network. Nodes can be computers, cell phones, or various other network appliances, such as routers, switches, and hubs. 3.2.2 subnet: A subnet is a physical network served by one router, for instance an Ethernet network (consisting of one or several Ethernet
32、 segments or local area networks, interconnected by switches and bridges) or a virtual local area network (VLAN). 4 Abbreviations and acronyms This Recommendation uses the following abbreviations: ALG Application Layer Gateway CPE Customer Premises Equipment FE Functional Entity NAT-PT Network Addre
33、ss Translation and Protocol Translation SCF Service Control Function SIIT Stateless IP/ICMP Translation Algorithm 5 Conventions 5.1 Native IPv6 device A device that only has IPv6 stack. 5.2 IPv6 transition mechanism An IPv6 transition mechanism means a mechanism that supports transition between IPv4
34、 and IPv6. There are many kinds of IPv6 transition mechanisms available, and the user can choose one that fits into a deployment environment. 5.3 Basic IPv6 transition mechanisms Basic IPv6 transition mechanisms means “Dual IP layer“ and “Configured tunneling“ which can be implemented on the IPv6 no
35、de b-IETF RFC 4213. 6 IP as a transport function of NGN NGN functions are divided into service stratum functions and transport stratum functions as described in ITU-T Y.2011. The transport stratum provides IP connectivity to NGN service stratum and users under the control of transport control functi
36、ons. This means that IP plays the key role of transport function of NGN. In NGN, most of services are carried over IP, although IP itself may in turn be carried over a number of underlying technologies like ATM, Ethernet, etc. According to the NGN release 1, it is assumed that the version of IP is n
37、ot fixed. This means that IPv4 and IPv6 could coexist in NGN Rec. ITU-T Y.2053 (02/2008) 3 while IPv4 is being replaced with IPv6, thus a mechanism that supports migration into IPv6 is required for this period. IETF introduced several IPv6 transition mechanisms as recommendations for migration to IP
38、v6 b-IETF RFC 4213. These mechanisms could also be recommendations for the NGN which uses IP as a transport function. The study of IPv6 with NGN has not yet been completed. The IPv6 transition mechanisms used in this Recommendation are dual stack, configured tunnelling, and network address translati
39、on/protocol translation (NAT-PT) b-IETF RFC 4213. These mechanisms are explained in more details in clause 7. When the IPv6 transition mechanisms are introduced to NGN, various migration scenarios could be possible. This Recommendation also shows such feasible scenarios. 7 Basic approaches for inter
40、working and migration The network consists of various IPv4-based and IPv6-based networks at different geographic locations which are connected via an underlying transport network. There are three major approaches in providing interworking and migration between the IPv4-based network and the IPv6-bas
41、ed network: dual IP layer, configured tunnelling and NAT-PT. For more information on these mechanisms, see Appendix I. 7.1 Dual IP layer (Dual stack) The node that has dual IP layer provides implementations of both versions of the Internet Protocol (IPv4 and IPv6) which are also enabled at the same
42、time. This node can directly interoperate with IPv4-only node using IPv4 packets, and also directly interoperate with IPv6-only node using IPv6 packets. There will be no IP protocol conversion necessary when communicating with a dual stack node on either the media path or the signalling path. Detail
43、s on dual IP layer node have been identified in b-IETF RFC 4213. 7.2 Configured tunnelling The configured tunnelling is a technique for establishing point-to-point tunnels by encapsulating IPv6 packets within IPv4 headers to carry them over IPv4 infrastructures (or vice versa). In most deployment sc
44、enarios, the IPv6 routing infrastructure will be built up over time. While the IPv6 infrastructure is being deployed, the existing IPv4 routing infrastructure can still remain and can be used to carry IPv6 traffic. Tunnelling provides a way to utilize an existing IPv4 routing infrastructure to carry
45、 IPv6 traffic. Dual stack nodes can tunnel IPv6 packets over regions of IPv4 routing topology by encapsulating them within IPv4 packets. Tunnelling can be used in a variety of ways: router-to-router; host-to-router; host-to-host. Configured tunnelling can be used in all of the above cases, but it is
46、 most likely to be used in router-to-router due to the need to explicitly configure the tunnelling endpoints. 7.3 Network address translation and protocol translation NAT-PT uses address translation like NAT and IPv6/IPv4 protocol translation as described in stateless IP/ICMP translation (SIIT) b-IE
47、TF RFC 2765 to provide transparent routing to end-hosts in IPv6 realm trying to communicate with end-hosts in IPv4 realm and vice versa. 4 Rec. ITU-T Y.2053 (02/2008) The SIIT identifies a protocol translation mechanism that allows communication between IPv6-only and IPv4-only hosts via protocol ind
48、ependent translation of IPv4 and IPv6 packets, requiring no state information for the session. Some applications carry network addresses in payloads. The NAT-PT is application unaware and does not snoop the payload. Application layer gateway (ALG) could work in conjunction with the NAT-PT to provide
49、 support for many such applications. Generally the NAT-PT function is placed on the edge of network. If the NAT-PT function is placed in the core of the network, the overall performance of the network would decrease seriously because the NAT-PT function reconstructs all IP packets that pass through it. NAPT-PT extends the notion of translation one step further by also translating transport identifier (e.g., TCP and UDP port numbers, ICMP query identifiers). The NAPT-PT, which stands for “Network Address Port Transl
