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 Series Y TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Supplement 41 (07/2016) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES Deplo
2、yment models of service function chaining ITU-T Y-series Recommendations Supplement 41 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS, INTERNET OF THINGS AND SMART CITIES GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Se
3、rvices, applications and middleware 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 Se
4、rvices and applications Y.1100Y.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
5、 Charging Y.1800Y.1899 IPTV over NGN Y.1900Y.1999 NEXT 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 servi
6、ces and networks in NGN Y.2250Y.2299 Enhancements to NGN Y.2300Y.2399 Network management Y.2400Y.2499 Network control architectures 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
7、 NETWORKS Y.3000Y.3499 CLOUD COMPUTING Y.3500Y.3999 INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES General Y.4000Y.4049 Definitions and terminologies Y.4050Y.4099 Requirements and use cases Y.4100Y.4249 Infrastructure, connectivity and networks Y.4250Y.4399 Frameworks, architectures and protoco
8、ls Y.4400Y.4549 Services, applications, computation and data processing Y.4550Y.4699 Management, control and performance Y.4700Y.4799 Identification and security Y.4800Y.4899 Evaluation and assessment Y.4900Y.4999 For further details, please refer to the list of ITU-T Recommendations. Y series Suppl
9、ement 41 (07/2016) i Supplement 41 to ITU-T Y-series Recommendations Deployment models of service function chaining Summary Supplement 41 to the ITU-T Y-series Recommendations describes use cases and deployment models of service function chaining. This Supplement also specifies requirements in order
10、 to support service function chaining in IP-based fixed and mobile networks. Service function chaining determines the requisite service functions (SFs), based on context information and selects a proper service function chain that consists of the requisite SFs providing specific treatment of packets
11、. Therefore, service provisioning can be rapid and flexible with high manageability. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T Y Suppl. 41 2016-07-08 13 11.1002/1000/13021 Keywords Service function, service function chain, service function chaining, service function pa
12、th. * 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 Y series Supplement 41 (07/2016) FOREWORD The International Telecommunication Union
13、(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 questions and
14、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 Recommendations on these
15、 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 publication, the expressio
16、n “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this publication is voluntary. However, the publication may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and
17、compliance with the publication 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 compliance with the publication is
18、 required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this publication may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intelle
19、ctual Property Rights, whether asserted by ITU members or others outside of the publication development process. As of the date of approval of this publication, ITU had received notice of intellectual property, protected by patents, which may be required to implement this publication. However, imple
20、menters 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 2016 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior writte
21、n permission of ITU. Y series Supplement 41 (07/2016) 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 Supplement 1 4 Abbreviations and acronyms 2 5 Conventions 3 6 Overview of service function chaining . 3 6.1 Service fu
22、nctions 3 6.2 Service function chaining . 4 6.3 Use cases 5 7 Deployment models of service function chaining 6 8 Requirements 9 9 Security considerations . 10 Appendix I Standardization activities of service function chaining . 11 Bibliography. 12 Y series Supplement 41 (07/2016) 1 Supplement 41 to
23、ITU-T Y-series Recommendations Deployment models of service function chaining 1 Scope This Supplement explains the concept of service function chaining and presents required functionalities. It describes use cases and deployment models of service function chaining. It also specifies requirements in
24、order to support service function chaining in IP-based fixed and mobile networks. 2 References ITU-T Y.2012 Recommendation ITU-T Y.2012 (2010), Functional requirements and architecture of next generation networks. ITU-T Y.2701 Recommendation ITU-T Y.2701 (2007), Security requirements for NGN release
25、 1. ITU-T Y.3043 Recommendation ITU-T Y.3043 (2013), Smart ubiquitous networks - Context awareness framework. ITU-T Y.3300 Recommendation ITU-T Y.3300 (2014), Framework of software-defined networking. 3 Definitions 3.1 Terms defined elsewhere This Supplement uses the following term defined elsewhere
26、: 3.1.1 middlebox b-IETF RFC 3234: Any intermediary device performing functions other than the normal, standard functions of an IP router on the datagram path between a source host and destination host. NOTE Normal, standard IP routing functions (i.e., the route discovery and selection functions des
27、cribed in, and their equivalent for IPv6) are not considered to be network processing functions; a standard IP router is essentially transparent to IP packets. 3.2 Terms defined in this Supplement This Supplement defines the following terms: 3.2.1 service function: A function, specifically represent
28、ing network service function, that is responsible for specific treatment of received packets other than the normal, standard functions of an IP router (e.g., IP forwarding and routing functions) on the network path between a source host and destination host. NOTE The examples of service function are
29、 similar to, but not limited to that of a middlebox. 3.2.2 service function chain: A chain that defines an ordered set of abstract service functions and ordering constraints that must be applied to packets and/or frames and/or flows selected as a result of classification and/or policy. 3.2.3 service
30、 function chaining: A mechanism of building service function chains and forwarding packets/frames/flows through them. 3.2.4 service function path: A path that defines an ordered set of specific instantiations of service functions that packets and/or frames and/or flows must visit within a specific s
31、ervice function chain. 2 Y series Supplement 41 (07/2016) NOTE A service function path is determined among the relevant service function paths within a specific service function chain, satisfying capacity and QoS requirements of service functions and their connecting links. There is typically a 1:n
32、relationship between a service function chain and a service function path. 4 Abbreviations and acronyms This Supplement uses the following abbreviations and acronyms: 3G 4G DPI FW HSS HTTP IDS IMSI IPS IPTV L2 L3 LTE NAT NF OSI PCRF QoE QoS RAT SF SFC SFI SFP SIP SMTP SNS TCP URL VLAN VO VoIP 3rd Ge
33、neration 4th Generation Deep Packet Inspection Firewall Home Subscriber System Hypertext Transport Protocol Intrusion Detection System International Mobile Subscriber Identity Intrusion Prevention System Internet Protocol Television Layer 2 Layer 3 Long Term Evolution Network Address Translation Net
34、work Function Open System Interconnection Policy Control and Repository Function Quality of Experience Quality of Service Radio Access Technology Service Function Service Function Chain Service Function Instance Service Function Path Session Initiation Protocol Simple Mail Transport Protocol Social
35、Networking Service Transport Control Protocol Uniform Resource Locator Virtual Local Area Network Video Optimizer Voice over Internet Protocol Y series Supplement 41 (07/2016) 3 VXLAN WAN Virtual Extensible Local Area Network Wide Area Network 5 Conventions NOTE This Supplement contains material tha
36、t is supplementary to the ITU-T Y-series of Recommendations. As such, this Supplement is not required for the implementation of service function chaining. In this Supplement: The keywords “is required to“ indicate a requirement which must be strictly followed and from which no deviation is permitted
37、, if conformance to this Supplement is to be claimed. The keywords “is prohibited from“ indicate a requirement which must be strictly followed and from which no deviation is permitted, if conformance to this Supplement is to be claimed. The keywords “is recommended“ indicate a requirement which is r
38、ecommended but which is not absolutely required. Thus, this Supplement need not be present to claim conformance. The keywords “is not recommended“ indicate a requirement which is not recommended but which is not specifically prohibited. Thus, conformance with this Supplement can still be claimed eve
39、n if this requirement is present. The keywords “can optionally“ indicate an optional requirement which is permissible, without implying any sense of being recommended. This term is not intended to imply that the vendors implementation must provide the option, and the feature can be optionally enable
40、d by the network operator/service provider. Rather, it means the vendor may optionally provide the feature and still claim conformance with this Supplement. 6 Overview of service function chaining This clause describes overview of service function chaining in terms of service functions and use cases
41、. 6.1 Service functions This clause introduces a various kind of service functions (SFs) and their roles, which is considered as an extension of middleboxes b-IETF RFC 3234. Until now, many kinds of middleboxes have been deployed in IP-based fixed and mobile networks in order to enhance the capabili
42、ties of the network. The middlebox performs numerous network processing functions, each providing a specific treatment of received packets. They range from security (e.g., firewall, intrusion detection system, traffic scrubber), traffic shaping (e.g., rate limiter, load balancer), dealing with addre
43、ss space exhaustion (e.g., network address translation) or improving the performance of network applications (e.g., traffic accelerator, cache, proxy). With the middlebox, the capability of a network can be quite enhanced in providing network services. The network services include examples such as v
44、oice/data, Internet access and a virtual private network b-ETSI GS NFV 002. However, most of these network services are implemented in costly, hard-to-modify, dedicated hardware, thus resulting in difficulty to rapidly deploy and easily adapt to new requirements. A service function is newly devised
45、and extended from the middlebox with the help of virtualisation technology and can be realized in a virtual entity as well as a physical entity. Similarly to a middlebox, a service function performs a specific treatment of received packets at various layers of a protocol stack. The specific treatmen
46、t of packet represents transformation, inspection and filtering. The examples of service functions include, but are not limited to the following: Network address translation (NAT) replaces the source and/or destination IP addresses of packets that traverse the NAT service function. Typically, NAT is
47、 deployed to allow multiple 4 Y series Supplement 41 (07/2016) end hosts to share a single IP address: hosts “behind“ the NAT are assigned a private IP address, and their packets destined to the public Internet traverse NAT which replaces their internal, private address, with a shared public address
48、. IP tunnel endpoints, including virtual private network endpoints, uses basic IP services to set up tunnels with their peer tunnel endpoints which might be anywhere in the Internet. Packet classifiers classify packets flowing through them according to policy and either select them for special treat
49、ment or mark them, in particular for differentiated services. TCP proxies modify the timing or action of the TCP protocol in flight for the purposes of enhancing performance. Load balancers provide one point of entry to a service, but forward traffic flows to one or more hosts that actually provide the service. Firewall (FW) functions filter traffic based on a set of predefined security rules defined by a network administrator. IP firewalls reject packets based purely on fields in the
