SFC P. Aranda Gutierrez Internet-Draft Intended status: Experimental M. Gramaglia Expires: January 2, 2018 UC3M DRL. Lopez TID W. Haeffner Vodafone July 01, 2017 Service Function Chaining Dataplane Elements in Mobile Networks draft-aranda-sfc-dp-mobile-04 Abstract The evolution of the network towards 5G implies a challenge for the infrastructure. The targeted services and the full deployment of virtualization in all segments of the network will be possible and necessary to provide some traffic-specific services near the next generation base stations where the radio is processed. Thus, service function chains that currently reside in the infrastructure of the Network operator (like, e.g. the Expeded Packet Gateway(EPG)) will be extended to the radio access network (RAN). In this draft we provide a non-exhaustive but representative list of service functions in 4G and 5G networks, and explore different scenarios for service-aware orchestration. We base on the problem statement [RFC7498] and architecture framework [RFC7665] of the SFC working group, as well on the existing mobile networks use cases [I-D.ietf-sfc-use-case-mobility] and the requirement gathering process of the ITU-R IMT 2020 [1] and different initiatives in Europe [2], Korea [3] and China [4] to anticipate network elements that will be needed in 5G networks. We then explore service-aware orchestration scenarios identifying where different network functions can be deployed in a fully virtualised future network, where both the core and the edge provide advanced virtualisation capabilities. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute Aranda Gutierrez, et al. Expires January 2, 2018 [Page 1] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 2, 2018. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology and abbreviations . . . . . . . . . . . . . . 3 1.2. General scope of mobile service chains . . . . . . . . . 4 1.3. Requirements for 5G networks . . . . . . . . . . . . . . 5 1.3.1. Evolution of the end-to-end carrier network . . . . . 5 2. Mobile network overview . . . . . . . . . . . . . . . . . . . 5 2.1. Building blocks of 4G and 5G networks . . . . . . . . . . 6 2.1.1. Classification schemes for 5G networks . . . . . . . 7 2.2. Transport Network Considerations . . . . . . . . . . . . 7 2.3. Control plane considerations . . . . . . . . . . . . . . 7 2.4. Operator requirements . . . . . . . . . . . . . . . . . . 7 3. New concepts for virtualised mobile networks . . . . . . . . 8 3.1. Service-aware orchestration . . . . . . . . . . . . . . . 8 3.2. Combining Access and Core . . . . . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.1. Normative References . . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . 12 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Aranda Gutierrez, et al. Expires January 2, 2018 [Page 2] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction The evolution of the network towards 5G implies a challenge for the infrastructure. The targeted services and the full deployment of virtualization in all segments of the network will need service function chains that previously resided in the(local and remote) infrastructure of the Network operators to extend to the radio access network (RAN). Existing mobile networks use cases presented to the working group and the requirement gathering process of the ITU-R IMT 2020 and different initiatives in Europe, Korea and China to anticipate network elements that will be needed in 5G networks allow us to define use cases for this next generation mobile networks. Once on the pillars of them will be service-aware orchestration. We present scenarios identifying where different network functions con be deployed in a fully virtualised future network, where both the core and the edge provide advanced virtualisation capabilities. These scenarios will allow us to derive Service Function Chaining (SFC)-specific requirements. 1.1. Terminology and abbreviations The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119 [RFC2119]. Much of the terminology used in this document has been defined by either the 3rd Generation Partnership Project (3GPP) or by activities related to 5G networks like IMT2020 in ITU-R. Some terms are defined here for convenience, in addition to those found in RFC6459 [RFC6459]. Aranda Gutierrez, et al. Expires January 2, 2018 [Page 3] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 +-------+-----------------------------------------------------------+ | UE | User equipment like tablets or smartphones | | eNB | enhanced NodeB, radio access part of the LTE system | | S-GW | Serving Gateway, primary function is user plane mobility | | P-GW | Packet Gateway, actual service creation point, terminates | | | 3GPP mobile network, interface to Packet Data Networks | | | (PDN) | | HSS | Home Subscriber Server (control plane element) | | MME | Mobility Management Entity (control plane element) | | GTP | GPRS (General Packet Radio Service) Tunnel Protocol | | S-IP | Source IP address | | D-IP | Destination IP address | | IMSI | The International Mobile Subscriber Identity that | | | identifies a mobile subscriber | | (S)Gi | Egress termination point of the mobile network (SGi in | | | case of LTE, Gi in case of UMTS/HSPA). The internal data | | | structure of this interface is not standardized by 3GPP | | PCRF | 3GPP standardized Policy and Charging Rules Function | | PCEF | Policy and Charging Enforcement Function | | TDF | Traffic Detection Function | | TSSF | Traffic Steering Support Function | | IDS | Intrusion Detection System | | FW | Firewall | | ACL | Access Control List | | PEP | Performance Enhancement Proxy | | IMS | IP Multimedia Subsystem | | LI | Legal Intercept | +-------+-----------------------------------------------------------+ Table 1 1.2. General scope of mobile service chains Current mobile access networks terminate at a mobile service creation point (called Packet Gateway) typically located at the edge of an operator IP backbone. Within the mobile network, the user payload is encapsulated in 3GPP specific tunnels terminating eventually at the P-GW. In many cases application-specific IP traffic is not directly exchanged between the original mobile network, more specific the P-GW, and an application platform, but will be forced to pass a set of service functions. Network operators use these service functions to differentiate their services. In order to cope with the stringent requirements of 5G networks (cf. Section 1.3), we expect a new architecture to appear. This architecture will surely make extensive use of virtualisation up to the RAN. We also expect that IP packets will need to be processed much earlier than in the current 3GPP architecture. In this context, Aranda Gutierrez, et al. Expires January 2, 2018 [Page 4] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 it is foreseeable that Service Function Chaining will play a substantial role when managing the chains network traffic will traverse. We also expect new kinds of service functions specific to the radio access part to appear and that these new service functions will need to be managed by the SFC management infrastructure of the operator. 1.3. Requirements for 5G networks As set forth by the 5G Infrastructure Public Private Partnership (5GPPP) [5], the evolution of the infrastructure towards 5G should enable the following features in the mobile environment: o Providing 1000 times higher wireless area capacity o Saving up to 90% of energy per service provided o Reducing the average service creation time cycle from 90 hours to 90 minutes o Facilitating very dense deployments of wireless communication links to connect over 7 trillion wireless devices serving over 7 billion people 1.3.1. Evolution of the end-to-end carrier network [SFC-Mobile-UC] presents the structure of end-to-end carrier networks and focused on the Service Function Chaining use cases for mobile carrier networks, such as current 3GPP- based networks. We recognise that other types of carrier networks that are currently deployed share similarities in the structure of the access networks and the service functions with mobile networks. The evolution towards 5G networks will make the distinction between these different types of networks blur and eventually disappear. 5G networks are expected to massively deploy virtualisation technologies from the radio elements to the core of the network. The four building blocks of the RAN, i.e. i) spectrum allocation or physical layer (PHY), ii) Medium Access Control (MAC), iii) Radio Link Control (RLC) and iv) Packet Data Convergence, are candidates for virtualisation. 2. Mobile network overview [SFC-Mobile-UC] provides an overview of mobile networks up to LTE (Long Term Evolution) networks. As the specifications mature, we will provide the updates to the LTE architecture. Aranda Gutierrez, et al. Expires January 2, 2018 [Page 5] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 2.1. Building blocks of 4G and 5G networks The major functional components of an LTE network are shown in Figure 1 and include user equipment (UE) like smartphones or tablets, the LTE radio unit named enhanced NodeB (eNB), the serving gateway (S-GW) which together with the mobility management entity (MME) takes care of mobility and the packet gateway (P-GW), which finally terminates the actual mobile service. These elements are described in detail in [ts-23-401]. Other important components are the home subscriber system (HSS), the Policy and Charging Rule Function (PCRF) and the optional components: the Traffic Detection Function (TDF) and the Traffic Steering Support Function (TSSF), which are described in [ts-23-203]. The P-GW interface towards the SGi-LAN is called the SGi-interface, which is described in [ts-29-061]. The TDF resides on this interface. Finally, the SGi-LAN is the home of service function chains (SFC), which are not standardized by 3GPP. +--------------------------------------------+ | Control Plane (C) [HSS] | [OTT Appl. Platform] | | | | | +--------[MME] [PCRF]--+--------+ Internet | | | | | | | | [UE-C] -- [eNB-C] == [S-GW-C] == [P-GW-C] | | | +=====|=========|==========|============|====+ +-----+----+-------+ | | | | | | | | | | | [UE-U] -- [eNB-U] == [S-GW-U] == [P-GW-U]-+--+----[SGi-LAN] | | | | | | | | | | | | | | [Appl. Platform] | | | | | | User Plane (U) | | | +--------------------------------------------+ +------------------+ Source [SFC-Mobile-UC] Figure 1: End to end context including all major components of an LTE network. Service Functions handle session flows between mobile user equipment and application platforms. Control plane metadata supporting policy based traffic handling may be linked to individual service functions. In 5G networks, we expect the packet gateway (P-GW) to loose its central position and be integrated with functions in the RAN. Radio Resource Control (RRC) in 5G network will be integrated into the Control Plane environment. Aranda Gutierrez, et al. Expires January 2, 2018 [Page 6] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 2.1.1. Classification schemes for 5G networks TBD: We expect classification schemes for 5G networks to evolve as the standards appear. 2.2. Transport Network Considerations The role of an enhanced SDN controller will become fundamental in the context of cloudified RAN deployments. RAN functions, e.g. PHY, Medium Access Control (MAC), RRM, located either at the edge or in the core network need to be flexibly controlled according to their functional split. This approach is also envisioned by e.g. 3GPP in its Rel. 14. A cRAN functional split takes place independently of other network management functionalities, the integrated SDN controller manages the transport network shall o Jointly optimize RAN and Core network functions by leveraging on its centralized network control capabilities. o Steer user flows across different network functions according to the functional split implemented in the network. SFC techniques are expected to play a fundamental role in this scenario. 2.3. Control plane considerations TBD: We except the RRC to be integrated with the SFC Control plane in 5G. 2.4. Operator requirements 4G mobile operators use service function chains to enable and optimize service delivery, offer network related customer services, optimize network behavior or protect networks against attacks and ensure privacy. Service function chains are essential to their business. Without these, mobile operators are not able to deliver the necessary and contracted Quality of Experience (QoE) or even certain products to their customers. Operators are forced to high efficiency with respect to cost and resources in deployment and operation to offer affordable services to their customers and, as we discussed in Section 1.3, the 5G Infrastructure Private-Public Partnership [6] has identified a set of additional requirements as the key differentiators for future networks. To meet these additional requirements, operators will need Aranda Gutierrez, et al. Expires January 2, 2018 [Page 7] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 to make an extensive use of service chains and to extend their scope to functions in the Radio Access Network. 3. New concepts for virtualised mobile networks Virtualisation and softwarization will be among the key technology introduced in the design of future 5G Network architecture. They allow to decouple the binding between hardware and software components in a flexible way. While used in conjunction with SFC, future mobile network may support the dynamical allocation of Network Functions (NFs) in network nodes and their orchestration according to the requirements of the implemented service. These concepts will be the building blocks of the future 5G architecture. Current efforts in the definition of SFC mostly focus on Core Network functions. We believe that the cloudification of RAN functions will increase the flexiblity needed to support very demanding and heterogeneous services envisioned by future 5G Networks, and hence the definition of the SFC Dataplane elements must also take into account functions once considered monolithically embedded in the eNB. In the next sections, we present some technical solutions that leverage on these novel concepts. 3.1. Service-aware orchestration The current 3GPP LTE Mobile Network architecture offers a low flexibility. Even by applying SFC techniques, specific network functions are executed in well-defined units (e.g., eNB and P-GW functions are carried out in dedicated hardware). Moreover, those network equipment are usually physically located in precise locations. This static approach burdens the flexibility needed by future 5G Networks. Softwarization and Virtualisation techniques allow for the flexible deployment of functions in the network. Therefore, the placement and execution of network functions should not be driven by topological constraints, but rather on QoS ones such as the specific requirements of the implemented service (e.g., latency, bandwidth and reliability, among others), the radio characteristics and the transport network capacity. This approach enables the concurrent execution of different instantiations of the protocol stack in the same nework infrastructure, as envisioned by the network slicing concepts. SFC is set to be a fundamental technology in this framework, allowing the dynamic deployment of different chains across many network slices spanning different cloud infrastructure arrangements. Hence, network functions can be physically located into different zones of the network: near the transmission point (edge cloud) or in centralised Aranda Gutierrez, et al. Expires January 2, 2018 [Page 8] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 data centers (central cloud). The choice on the orchestration of such network functions will hence happen on a per-service basis. Edge Cloud Central Cloud +--------------------Vehicular Communications----------------------+ | +----+ +----+ +----+ +----+ +----+ | | | DR | | CR | | DC | | CC | | CC | | | +----+ +----+ +----+ +----+ +----+ | +------------------------------------------------------------------+ +--------------------Haptic Internet-------------------------------+ | +----+ +----+ +----+ +----+ | | | DR | | CR | | DC | | CC | | | +----+ +----+ +----+ +----+ | +------------------------------------------------------------------+ +--------------------Internet Access-------------------------------+ | +----+ +----+ +----+ +----+ +----+ | | | DR | | DR | | CR | | DC | | CC | | | +----+ +----+ +----+ +----+ +----+ | +------------------------------------------------------------------+ DR: data plane RAN CR: control plane RAN DC: data plane Core CC: control plane Core Source [SFC-Mobile-UC] Figure 2: Service-aware orchestration of network functions. In order to achieve a service aware orchestration described above, there are some challenges that need to be addressed. They are illustrated by the following examples : o Vehicular communications need low latency and sessionless connectivity. Therefore, almost all the NFs belonging to this service should be located close to the transmission point, including those traditionally located in the core network; o Haptic Internet applications require both low latency and session continuity. Therefore, most of the network functions should be located close to the transmission point, but some control plane ones should be located in the core network; o Internet access users do not usually have strict latency requirements. Thus, the network functions related to them may be located in the core network, efficiently exploiting the multiplexing gain enabled by this kind of deployment. Aranda Gutierrez, et al. Expires January 2, 2018 [Page 9] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 3.2. Combining Access and Core Traditional architectures force a fixed topological relation between network functions, while in a virtualised architecture, as the one proposed above, these constraints are relaxed. This difference is especially highlighted for access and core network functions. While in a traditional architecture, these functions are usually executed in different parts of the network (e.g., the scheduler in the base station and a firewall in the centre of the network), a virtualised architecture blends the boundaries between access and core functions: their final location is decided on a functional basis. For instance, services with strict latency requirements may be located close to the transmission points, while services that can exploit centralisation may be located in the core data centre. The application of this concept may end up with access and core functions sharing the same network location. This fact enables possible improvements, as detailed in the following example. Currently, mobility and scheduling decisions are taken separately. The mobility-related network functions are traditionally located in the core network and their decisions are taken before scheduling ones, which are taken subsequently, in the access network. It is important to note that a decision about mobility cannot be modified at the scheduling level. With a fully virtualised architecture, the mobility and scheduler network functions may be co-located in the same network node, enabling a possible joint-optimisation between mobility and scheduling. However, this is only one example of possible optimisations that can be achieved using this kind of approach. The proposed approach reduces high latencies introduced by the traditionally separated deployment of access and core domains. Therefore, further optimisation may be introduced as the impact of signalling protocols is reduced. SFC is expected to play a fundamental role in this picture, allowing the flexible chaining of network functions. 4. Security Considerations Organizational security policies must apply to ensure the integrity of the SFC environment. SFC will very likely handle user traffic and user specific information in greater detail than the current service environments do today. This is reflected in the considerations of carrying more metadata through the service chains and the control systems of the service chains. This metadata will contain sensitive information about the user and the environment in which the user is situated. This will require proper considerations in the design, implementation Aranda Gutierrez, et al. Expires January 2, 2018 [Page 10] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 and operations of such environments to preserve the privacy of the user and also the integrity of the provided metadata. 5. IANA Considerations This document has no actions for IANA. 6. Acknowledgements This work has been partially performed in the scope of the SUPERFLUIDITY project, which has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No.671566 (Research and Innovation Action). This work has also been partially performed in the framework of the H2020-ICT- 2014-2 project 5G NORMA. The authors would like to acknowledge the contributions of their colleagues. This information reflects the consortium's view, but the consortium is not liable for any use that may be made of any of the information contained therein. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6459] Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen, T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation Partnership Project (3GPP) Evolved Packet System (EPS)", RFC 6459, DOI 10.17487/RFC6459, January 2012, . [RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for Service Function Chaining", RFC 7498, DOI 10.17487/RFC7498, April 2015, . [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015, . Aranda Gutierrez, et al. Expires January 2, 2018 [Page 11] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 7.2. Informative References [I-D.ietf-sfc-use-case-mobility] Haeffner, W., Napper, J., Stiemerling, M., Lopez, D., and J. Uttaro, "Service Function Chaining Use Cases in Mobile Networks", draft-ietf-sfc-use-case-mobility-05 (work in progress), October 2015. [fiveg] "The 5G Infrastructure Public Private Partnership", . [ts-23-003] 3GPP, ""Numbering, addressing and identification"", , July 2015. [ts-23-203] 3GPP, "Policy and charging control architecture", TS 29.203, July 2015. [ts-23-401] 3GPP, "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access", 3GPP YS 23.401, July 2015. [ts-29-061] 3GPP, "Interworking between the Public Land Mobile Network(PLMN) supporting packet based services and Packet Data Networks (PDN)", 3GPP TS 29.061, March 2015. [ts-29-212] 3GPP, "3GPP Evolved Packet System (EPS); Evolved General Packet Radio Service (GPRS) Tunneling Protocol for Control plane (GTPv2-C); Stage 3", 3GPP TS , July 2015. [ts-29-274] 3GPP, "3GPP Evolved Packet System (EPS); Evolved General Packet Radio Service (GPRS) Tunneling Protocol for Control plane (GTPv2-C); Stage 3", 3GPP 29.274, December 2013. [ts-29-281] 3GPP, "General Packet Radio System (GPRS) Tunneling ProtocolUser Plane (GTPv1-U)", 3GPP TS , January 2015. [ts-33-210] 3GPP, "3G security; Network Domain Security (NDS); IP network layer security", 3GPP TS 33.210, December 2012. Aranda Gutierrez, et al. Expires January 2, 2018 [Page 12] Internet-Draft SFC Dataplane Elements in Mobile Networks July 2017 7.3. URIs [1] http://www.itu.int/en/ITU-R/study-groups/rsg5/rwp5d/imt- 2020/Pages/default.aspx [2] https://5g-ppp.eu [3] http://www.5gforum.org/#!eng/cvb1 [4] http://www.imt-2020.cn/en/introduction [5] https://5g-ppp.eu [6] fiveg Authors' Addresses Pedro A. Aranda Gutierrez Email: paaguti@gmail.com Marco Gramaglia Universidad Carlos III de Madrid Av. Universidad, 30 Leganes 28911 Spain Email: mgramagl@it.uc3m.es Diego R. Lopez Telefonica I+D Zurbaran, 12 Madrid 28010 Spain Email: diego@tid.es Walter Haeffner Vodafone D2 GmbH Ferdinand-Braun-Platz 1 Duesseldorf 40549 Germany Email: walter.haeffner@vodafone.com Aranda Gutierrez, et al. Expires January 2, 2018 [Page 13]