Network Working Group L. Xue Internet-Draft B. Sarikaya Intended status: Informational Huawei Expires: April 18, 2013 D. von Hugo Telekom Innovation Laboratories October 15, 2012 Problem Statement for Fixed Mobile Convergence draft-xue-fmc-ps-02.txt Abstract The purpose of this document is to analyze the issues that have arisen so far and to propose several use cases for the Fixed Mobile Convergence. This document gives a brief overview of the assumed Fixed Mobile Convergence architecture and related works and then introduces several Intarea type of use cases based on the partnership in Fixed Mobile Convergence architecture, such as User Equipment identification, mobility consideration, such as mobility status reporting in Wi-Fi network and transporting Wi-Fi link characteristics type of considerations. 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 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 April 18, 2013. Copyright Notice Copyright (c) 2012 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 Xue, et al. Expires April 18, 2013 [Page 1] Internet-Draft PS for FMC October 2012 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 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 6 3. Key Issues in Fixed Mobile Converged Interworking . . . . . . 7 4. UE identification in Fixed Broadband Network . . . . . . . . 7 5. UE Mobility in Fixed Broadband Network . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Xue, et al. Expires April 18, 2013 [Page 2] Internet-Draft PS for FMC October 2012 1. Introduction Growing availability of intelligent mobile devices and mature networks of operators providing both reliable carrier grade connectivity and affordable high bandwidth access offer to the customer a nice climate of mobile broadband. With widespread availability and easy usability of mobile broadband, mobile broadband applications become more ubiquitous. Subscribers demand for various service applications, especially Internet applications, such as mobile Internet video, mobile Internet real-time communication, etc. The subscribers requirements lay the foundation of mobile broadband. On the other hand, simultaneously, the subscribers' services promote the evolution of mobile broadband, which will impact the network architecture. The flourishing mobile applications demand more and more bandwidth offered by the operators. Even with wireless networks becoming mature, such as 3G and LTE, the average bandwidth offered is not comparable to data rates offered by fixed networks. With data services rapidly increasing, the traditional cellular network operating at a shared medium and thus being limited in transmission rate often becomes the bottle-neck of mobile broadband. In addition radio network technology generally requires high capital investment and operational expenditures. Cellular network operators are facing the challenge of increasing traffic demand at decreasing revenue and have to provide means of more cost efficient access technology in a highly competitive environment. The trend of offloading the traffic to fixed broadband network is emerging. Mobile industry has specified functionalities to offload the data traffic to the fixed broadband (FBB) network, via WLAN or a Home (e)NodeB (HNB or eNodeB, aka. Femtocell) [TR23.829], which could alleviate traffic pressure on the mobile network. That is to say, today, operators are able to employ mechanisms to manage the subscriber service over both the mobile and the fixed broadband network. We can say, FMC is emerging on the basis of subscribers and operators requirements. Fixed Mobile Convergence is a technology trend which aims to provide the subscribers access to services regardless of the access network type they are connecting to and provide the operators with the flexibility to ensure transparency of services to the end user. For a mobile subscriber to access services over both mobile and fixed broadband networks seamlessly, additionally, the subscriber's end-to- end service level agreement (SLA) must be maintained. This is achieved by interworking the control planes of the fixed broadband network and the mobile network. In the FMC interworking scenario addressed here, the fixed broadband network must partner with the mobile network to perform authorisation, authentication, and accounting (AAA) and acquire the Xue, et al. Expires April 18, 2013 [Page 3] Internet-Draft PS for FMC October 2012 policies for the mobile subscriber. Please note, a single converged control plane, used for both the fixed broadband and the mobile network, may be used in a truely converged, i.e. integrated convergence scenario. This document only focuses on the interworking scenario in this version. The convergence scenario is for further study. Figure 1 shows the assumed reference architecture of Fixed Mobile Convergence Interworking for a Mobile (3GPP) Network and a fixed non- 3GPP access network as proposed by 3GPP and BroadBand Forum (BBF) as an example in document [TR203]. Xue, et al. Expires April 18, 2013 [Page 4] Internet-Draft PS for FMC October 2012 +---------------------------------------+ | Mobile Network | | ---- | | +------+ / \| | +----+ PCRF | |Operator| | | +---+--+ | Service| | | | \ /| | | | --+- | +------+ +------+ | +------+ +---+--+ | | | | UE | | eNB +-----+ SGW +---+ PGW +-----|---------+----------+ +------+ +------+ | +------+ +--+---+---+ | +------+| | | +--+---+ +-|-----+M AAA || --+- | | ePDG +---+ | +---+--+| / \ +------------+------+-----|---------|---+ |Internet | | | | Service +---------------|---------|---------|---+ \ / | Fixed Network | +---+--+ +---+--+| --+- | | +---+ BPCF | |F AAA || | | +--+-+-+ +------+ +---+--+| | +------+ | | BNG +---------------+ | | | Femto+-----------+ +--+-+-+ | | +------+ | | | +----------------------------+ +------+ | | +--+---+ | | UE | | +----+ AN | | +------+ +------+ | +--+---+ | |WiFiAP|-------------------+ | | CPE | | | +------+ | | +---------------------------------------+ Legend: M AAA Authentication Authorization Accounting in Mobile Network F AAA Authentication Authorization Accounting in Fixed Network AN Access Node BPCF Broadband Policy Control Function BNG Broadband Network Gateway ePDG evolved Packet Data Gateway PCRF Policy Charging Rule Function PGW Packet Data Network Gateway SGW Serving Gateway UE User Equipment Figure 1: Reference Architecture of Fixed Mobile Convergence The policy and charging control (PCC) system is an important element in FMC architecture. PCC system of FMC consists of policy decision point (PCRF in the mobile network and BPCF in the fixed broadband network) and the policy enforcement point (PGW and BNG, respectively), shown in Figure 1. PCC should support for controlling Xue, et al. Expires April 18, 2013 [Page 5] Internet-Draft PS for FMC October 2012 the QoS (e.g., QoS class and bit rates) authorized for service, and IP flow based charging. In FMC interworking scenario, these services can be divided into four types. 1. Service via macrocell wireless network 2. Service via WiFi/Femtocell access routed back to 3GPP Evolved Packet Core (EPC), where the fixed broadband network is used as the access network, * The service from a mobile UE is connected to WiFi or to Femtocell Access Point (FAP) at the residential gateway (RG), routed back to 3GPP Evolved Packet Core (EPC). 3. Services via WiFi access only fixed broadband routed * The service from a mobile UE is connected to WiFi without traversing the mobile network. * In this scenario, the UE service may be guaranteed based on subscriber's policy from the mobile network. 4. LIPA/SIPTO traffic * Support of Local IP access (LIPA) and of Selected IP traffic offload (SIPTO) for the Home (e)NodeB Subsystem and for the macro layer network include a more integrated FMC scenario and thus are for further study. As for the services stated above, only the second and the third type are related to FMC, where both the fixed broadband and the mobile network are involved. The FMC architecture shall be capable to set operator policies to support simultaneous access to these service. In the network today, deploying FMC is a worthy way for operators to satisfy subscriber's requirement and ease pressure from bandwidth. In the following sections, we first describe the motivation and then discuss the key issues that are at this time limited to the Intarea and to FMC interworking scenario. 2. Conventions and Terminology 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 RFC 2119 [RFC2119]. Xue, et al. Expires April 18, 2013 [Page 6] Internet-Draft PS for FMC October 2012 3. Key Issues in Fixed Mobile Converged Interworking There is a need to highlight and discuss the issues when facilitating FMC. We systematically analyze the issues that have been proposed so far and briefly assess the possible protocol extensions which could solve the problems. In the network architecture, we target and limit the scope to the interworking architecture for FMC. Regarding the traffic management and control requirements in FMC interworking scenario, these are the issues from an IETF Internet Area and fixed broadband network point of view. 1. UE identification in fixed broadband network 2. UE mobility status reporting in fixed broadband network 3. Transportation of UE link characteristics in fixed broadband network. There are many standardization issues related to FMC and protocol extension work needed are stated in this document. If these issues are fixed, the advantages brought out will be: 1. Optimize traffic management (per-UE granularity in the fixed broadband network) 2. Enhance device management (via IP address synchronization between fixed broadband network and mobile network) 3. Quick Responsiveness based on UE status These issues are elaborated in the sections that follow. 4. UE identification in Fixed Broadband Network Nowadays, a subscriber is always provided with a single private IPv4 address at their home or small business, which should reduce the pressure on the available public IPv4 addresses which are now exhausted. For instance, in the fixed broadband network, each host within the local network will be assigned a private IPv4 address, then NA(P)T function is responsible for translating the private IPv4 address to the public IPv4 address assigned to the CPE (Customer Premises Equipment) by operators, and vice versa. As a result of maintaining growth of IPv4 service, private addressing plan will require address sharing, which will cause issues for operators, such as traffic management, QoS enforcement, etc. in the Xue, et al. Expires April 18, 2013 [Page 7] Internet-Draft PS for FMC October 2012 FMC scenarios, where the policy control must be based on the fundamental concept of per-UE granularity. Note that ultimately, deploying IPv6 without NA(P)T function is the only perennial way to ease pressure on the public IPv4 address without the need for address sharing mechanisms that give rise to the issues identified herein. But in the interim, however, IPv4 services are also very important for end-users, and service providers, which can not be ignored. Consider Figure 2 where several UEs are connected to the same RG in a fixed broadband network in an address sharing scheme. Each UE is assigned a private IPv4 address which are shared by RG private/public Wide Area Network (WAN) interface IPv4 address. Problems are introduced because of address sharing via NA(P)T and UEs identification or Host Identifier (HOST_ID) needs to be communicated to fixed broadband network nodes such as the edge router (BNG) or Traffic Detection function (TDF) [RFC6269]. In FMC network, it is assumed that fixed broadband network manages the traffic in per-UE granularity. The important consideration is that today's PCC (including QoS control and IP flow based charging) must be based on the concept of IP Connectivity Access Network (IP- CAN) in per-UE granularity. IP-CAN session [TS23.203] is the association between a UE and an IP network. Obviously, the fixed broadband network and mobile network must support inter-operator subscribers policy exchange, this introduces a major challenge on how to coordinate UE identification across the operators' domains so that the mobile network can inform the suitable policy to the serving fixed broadband access network that its mobile user equipment (UE) is attached to so that the fixed broadband network can provide the appropriate FMC interworking policy and bearer control on UE's traffic. There may be limitations with BNG implementations with respect to the level of granularity (per-UE) of the enforcement. A key problem is to identify offloaded traffic from a UE behind the NA(P)T embedded into RG. There is no longer a unique IP address per UE, in addition, the UDP port behind NA(P)T is not bound to the special UE. Another problem that arises is efficient packet inspection. Operators expect the fixed broadband network could be configured in such a way that the traffic subject to packet inspection is routed via the Traffic Detection Function (TDF) [TS29.212], otherwise, the traffic that is not subject to packet inspection may bypass the TDF. This assumption only holds if it is possible to identify individual UEs behind NA(P)T in fixed broadband network, shown in Figure 2. Xue, et al. Expires April 18, 2013 [Page 8] Internet-Draft PS for FMC October 2012 +----+ | UE | +----+ Internet +----+ |TDF |---> W +----+ Mobile +----+ i | Network | UE | F +----+ | +----+ i | AP | +----------+ +----------+ +----+ | & | | | | | | UE | L | RG |----| | +-------------+ | | +----+ i +----+ | Access |-----| Aggregation | | Edge | +----+ n | Node | | Network |---| Router | | UE | k | | +-------------+ | | +----+ +----------+ +----------+ RG with NA(P)T Figure 2: UE's Identification in Broadband Network As discussed before, there are many drivers for the identification of the host or UE when an IP (v4 or v6) address is shared among several users in the broadband network. They include efficient packet inspection, QoS enforcement, charging. We can note that all these functions in FMC depend on being able to identify UEs behind the NA(P)T functionality. There are several possibilities which provide solutions. There are several possible IP, ICMP (both v4 and v6) or TCP/UDP protocol extensions, discussed in [I-D.ietf-intarea-nat-reveal-analysis]. Additionally, there may be other possibilities, such as some other new identifier to be defined as the host identifier to be passed by the subscriber to a server such as BNG or TDF. It is difficult to foresee which is the suitable solution, more work needs to be done. There are also several possibilities which provide link layer solutions. Using VLANs or link layer address/ MAC address of the UE provide the necessary identification for the UE. Link layer solutions to UE identification are left out of scope. 5. UE Mobility in Fixed Broadband Network The users are the mobile subscribers in FMC. Note that all the services depend on the substantive character of subscriber's mobility. It is important for operators to capture the user device when it is moving into or outside the network, even in WiFi access. Besides, the application and service from the subscriber must be guaranteed based on the policy of operators. Xue, et al. Expires April 18, 2013 [Page 9] Internet-Draft PS for FMC October 2012 In mobile network today, there are many mature solutions offered for user's mobility already. Herein, only mobility in fixed access, i.e., WiFi access, will be considered. For example, the user device is attached to the home LAN (e.g., WiFi ) network, and establishes a connection back to the subscriber's mobile service provider network via the fixed broadband network. The mobile operator should cooperate with the broadband access operator to deliver proper policy for the service from UE. +----+ +------+ +----------+ | UE1| |AP&RG |----| | +----+ +------+ | | W | AN |\ +----+ i+------+ | | \ | UE2| F|AP&RG |----| | \ +----+ i+------+ +----------+ \ +----------+ \ | | L +-------------+ | | i | Aggregation | | Edge | n | Network |-------| Router | k +-------------+ | | +----------+ / +----------+ +----+ +-----+ | | / | UE3| |AP&RG|----| AN |/ +----+ +-----+ | | +----------+ Figure 3: UE Mobility in Broadband Network The mobility considered in the fixed access does not consider the use of a mobility protocol. Consider Figure 3 where there are many mobile nodes, i.e. UEs connected to the fixed braodband network. Status of these nodes at a given time needs to be communicated to the network by the access points. In this section, we divide the mobility status reporting capability into two cases: 1. UE is moving into or outside the coverage area of WiFi AP 2. UE's WiFi access is dormant or not. Figure 3 shows an example of the scenario where mobile UEs are served in WiFi deployment over the fixed broadband network. RG embeds WiFi AP and NA(P)T function. Each UE is provided with a single private IPv4 address assigned within the local network. NA(P)T in RG is responsible for translating the private IPv4 address to the public IPv4 address assigned by the fixed operator. BPCF in fixed broadband network must have partnership with PCRF in Xue, et al. Expires April 18, 2013 [Page 10] Internet-Draft PS for FMC October 2012 mobile network in order to maintain the service level agreement (SLA). In order to allow the PCRF to retrieve the UE's policy to be passed onto the BPCF in the fixed broadband network, it is mainly concerned about the traffic and UE identification binding used to achieve the actual traffic control. The BPCF/BNG will perform the policy control based on the binding. Based on the UE's mobility, problems will arise. For example, the PCRF will download the policy to the BPCF when UE first attaches the AP after the UE is authenticated and an IP address/prefix is assigned. Consider the two UEs, shown in Figure 3. UE1 and UE2 are assigned different private/public IP addresses within the local network, IP1 and IP2 respectively. BPCF/BNG will perform the admission control and policy enforcement on the UE1 and UE2 traffic. Since plenty of UEs may move into the coverage of WiFi AP, it is possible that large amount of resources will be needed at the BPCF/ BNG. for optimum operation, the resources need to be released when the UE goes out of the coverage of WiFi AP. So timely detection of UE detachments is crucial in fixed mobile convergence environments. That is to say the configuration must be updated regularly to satisfy that the WiFi AP can serve thousands of UEs and proper resource allocation at the BPCF/BNG. Possible solutions approaches include extending the Control And Provisioning of Wireless Access Points (CAPWAP) architecture RFC 5415 [RFC5415]. Access Controllers using an extended protocol can be charged to keep track of the mobility status of the UEs that are connected to the fixed broadband network using IEEE 802.11 links. However, in Fixed Mobile Convergence, this information is needed by entities not necessarily co-located with the Access Controller. In some cases, e.g. home networks, CAPWAP protocol is not commonly used. In such cases, it becomes even more challenging to keep track of the UE mobility status. Protocol solutions need to be developed to solve this problem. During the solution process, CAPWAP protocol could be used as an example. 6. IANA Considerations This document makes no request to IANA. 7. Security Considerations Serious concern of mobile operators towards FMC approaches has been the customer access via networks not under control of the operator. Xue, et al. Expires April 18, 2013 [Page 11] Internet-Draft PS for FMC October 2012 Operators would like to keep their own high security measures to prevent various kinds of fraud or attack to the operators services and network entities. Well known risks and vulnerabilities which are common to any NA(P)T application are documented in the NAT specification [RFC2663]. Any additional security considerations arising from FMC are TBD. 8. Acknowledgements Many people provided comments that have been incorporated into this document including Mohamed Boucadair, David Binet, Pierrick Seite, Daniel Park and Cameron Byrne. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And Provisioning of Wireless Access Points (CAPWAP) Protocol Specification", RFC 5415, March 2009. [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010. [RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P. Roberts, "Issues with IP Address Sharing", RFC 6269, June 2011. [TR23.829] "3GPP TR23.829, Local IP Access and Selected IP Traffic Offload (LIPA-SIPTO)", October 2011. [TS23.203] "3GPP TS23.203, Policy and Charging control architecture", September 2012. [TS29.212] "3GPP TS29.212, Policy and Charging Control (PCC) over Gx/Sd reference point", September 2012. Xue, et al. Expires April 18, 2013 [Page 12] Internet-Draft PS for FMC October 2012 9.2. Informative References [I-D.ietf-intarea-nat-reveal-analysis] Boucadair, M., Touch, J., Levis, P., and R. Penno, "Analysis of Solution Candidates to Reveal a Host Identifier (HOST_ID) in Shared Address Deployments", draft-ietf-intarea-nat-reveal-analysis-04 (work in progress), August 2012. [RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address Translator (NAT) Terminology and Considerations", RFC 2663, August 1999. [RFC6264] Jiang, S., Guo, D., and B. Carpenter, "An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition", RFC 6264, June 2011. [TR203] "Broadband Forum Technical Report TR-203, Interworking between Next Generation Fixed and 3GPP Wireless Access", August 2012. [TS24.302] "3GPP TS24.302, Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks", September 2012. [WT146] "Broadband Forum Working Text WT-146, Subscriber Sessions", June 2012. Authors' Addresses Li Xue Huawei No.156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan, Beijing, HaiDian District 100095 China Email: xueli@huawei.com Behcet Sarikaya Huawei 5340 Legacy Dr. Plano, TX 75024 Email: sarikaya@ieee.org Xue, et al. Expires April 18, 2013 [Page 13] Internet-Draft PS for FMC October 2012 Dirk von Hugo Telekom Innovation Laboratories Deutsche-Telekom-Allee 7 D-64295 Darmstadt Germany Phone: Email: Dirk.von-Hugo@telekom.de Xue, et al. Expires April 18, 2013 [Page 14]