Ethernet Services over Mobile WiMAX

Transcription

1 WIMAX: A TECHNOLOGY UPDATE Ethernet Services over Mobile WiMAX Max Riegel, Nokia Siemens Networks ATRACT Ethernet services represent a steadily growing portion of the fixed telecommunication market. To enable the provisioning of Ethernet services over IEEE e, the Mobile WiMAX network architecture supports transparent Ethernet transport as an optional extension to the IP services architecture. Ethernet support is tightly aligned to the IP services network model, and leverages many data path and control plane functions from its IP sibling to keep the implementation and operation overhead low for the Ethernet extension. Mobile WiMAX provides IP services as well as Ethernet services over the same mobile access network. The intrinsic mobility support may create new deployment opportunities for Ethernet services. Initially, the Ethernet extension may be mostly used to realize wireless access for DSL networks based on the same network interfaces defined for the wired Ethernet-based DSL aggregation. INTRODUCTION Ethernet services (often called carrier Ethernet services) have become common telecommunication services for establishing and connecting private networks of corporations, public authorities, or service providers, offering telecommunication services on top of the infrastructure of another network operator. Transparent layer 2 (L2) connectivity is provided based on Ethernet technologies due to its widespread availability, high scalability in terms of bandwidth as well as network size, excellent support of all kind of network layer protocols, and leading edge cost position. While the basic Ethernet technology is standardized by IEEE 802, the Metro Ethernet Forum has established a set of specifications describing the services model and characteristics, an architectural framework, network interfaces, and the operation and management of Ethernet services. Meanwhile, the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) has adopted Ethernet as a transport technology and is extending the specification framework for usage in global public telecommunication networks. Mobile WiMAX deploys the IEEE e radio interface to serve fixed, nomadic, and mobile broadband applications over the same access network. Within its scope as a universal cellular access network technology, the support of Ethernet services over a Mobile WiMAX access network is a useful extension. It covers not only the traditional mobile telecommunication services market, but also allows participation in the growing carrier Ethernet market in areas or cases when an appropriate wired infrastructure is not available. In particular, support of Ethernet services may be deployed by digital subscriber line (DSL) operators to extend their access networks based on Ethernet aggregation over a wireless infrastructure to customers without a phone line. Even though it is not an established market yet, providing mobility for Ethernet services may open new business opportunities for operators as well as deployment opportunities for Mobile WiMAX. This article describes extensions to the Mobile WiMAX specification to enable the support of Ethernet services as part of WiMAX Forum Release 1.5. ETHERNET SERVICES The Metro Ethernet Forum (MEF) has established a full set of specifications for the introduction of Ethernet services, and the definition of the particular service attributes to facilitate commonly understood service level agreements between service providers and customers. Based on the concept of an Ethernet virtual connection (EVC), the MEF [1] distinguishes two kinds of Ethernet services (Fig. 1). E-LINE SERVICE E-Line service is a point-to-point connection carrying Ethernet frames between two customer interfaces of the network. It is frequently used for substituting legacy time-division multiplex (TDM) private lines with less expensive Ethernet private lines. When multiple point-to-point connections, each carrying its distinct service, are multiplexed onto a single Ethernet interface at the provider edge, the Ethernet private line service becomes an Ethernet virtual private line service, for example, used by an Internet service provider (ISP) to provide Internet service to multiple customers over a single Ethernet interface, a mode that is well supported by the bandwidth hierarchy of Ethernet interfaces. E-LAN SERVICE E-LAN service provides multipoint-to-multipoint connectivity for Ethernet frames across a number of customer interfaces, essentially behaving /08/$ IEEE IEEE Communications Magazine October 2008

2 like an extension to the customer s own LAN. It is mostly deployed for creation of transparent LAN service (TLS), which enables full transparency for Ethernet control protocols and allows customers to establish new virtual LANs (VLANs) across their private networks without involvement of the Ethernet service provider. Due to its inherent replication function for multicast and broadcast frames, E-LAN service may also be used for efficient delivery of multicast services from a service provider s head-end to multiple customers. Depending on whether TLS is used by private network operators to extend corporate LANs or by ISPs to provide public access to Internet services to many customers, different operational modes are distinguished: Public access mode When deploying Ethernet aggregation for public access services, the LAN service usually restricts direct communication between customers endpoints, and enforces that all Ethernet frames are passed through the ISP headend to enable accounting and enforcement of security policies by the ISP. From the customer s perspective the service looks more like an E-Line service toward the ISP, but from the ISP side all customers reside on the same link. Enterprise LAN mode When all connected end stations belong to the same enterprise and reside in the same security domain, direct connectivity across the TLS from any end station to any other end station is feasible. In this mode the E-LAN service really behaves like a LAN with all stations being reachable from any interface on the same link. While the enterprise LAN mode represents standard Ethernet behavior among all participants of the LAN service, the public access mode introduces special forwarding behavior in the bridges to enforce that all customer traffic passes the ISP head-end regardless of whether the communication peers are residing on the same link or different links. BASIC ETHERNET SERVICES STANDARDS The fundamental standards for Ethernet services were created in the Higher Layer LAN Protocols Working Group P802.1 of the IEEE802 LAN/MAN Standards Committee. An extension to the IEEE 802.1D standard on medium access control (MAC) bridges enabling end stations to transparently communicate with each other across multiple LANs, and defining the basic forwarding and filtering behavior in today s switched Ethernet, IEEE 802.1Q introduced the concept of segregating LAN traffic into VLANs, which allow the creation of multiple isolated LANs on the same bridged LAN infrastructure. VLANs are commonly used inside larger organizations to establish separate LANs for particular applications and organizational units across widespread campuses and sites. Two amendments to IEEE 802.1Q have expanded the applicability of VLANs to large operator networks and even across multiple operator networks: IEEE 802.1Q-2005 (Virtual Bridged Local E-line service type E-LAN service type Figure 1. Ethernet service types. Point-to-point EVC Multipoint-tomultipoint EVC Area Networks) [2] adopts from 802.1D the generic bridge architecture, the internal sublayer service, the major features of the filtering and forwarding process, the Rapid Spanning Tree Protocol, and the Generic Attribute Registration Protocol (GARP), and adds the definition of VLAN dervices, the required extensions to the filtering database and forwarding process, the definition of an extended frame format able to carry VLAN identifiers as well as priority information, the GARP VLAN Registration Protocol, and the Multiple Spanning Tree Protocol. The standard supports up to 4094 VLANs on the same bridged LAN infrastructure, which is usually sufficient for corporate networks but limits its applicability for larger provider networks. IEEE 802.1ad-2005 (Amendment 4: Provider Bridges) [3] amends the IEEE 802.1Q standard to enable service providers to offer the capabilities of IEEE 802.1Q virtual bridged LANs to a number of customers with no need for alignment across the customers and only minimal interaction between the operation, administration, and maintenance (OAM) of the service provider and the OAM of the customers. The standard introduces another layer of traffic segregation by appending the customer VLAN identifiers (C-VID) to a service provider VLAN identifier (S-VID), allowing the service IEEE Communications Magazine October

3 Length Ethernet DA SA type Data FCS Length 802.1Q DA SA 0x8100 VID type Data FCS 802.1ad Length DA SA 0x88A8 S-VID 0x8100 VID type Data FCS 802.1ah Length B-DA B-SA I-SID DA SA 0x88A8 S-VID 0x8100 VID type Data FCS B-DA: Backbone destination MAC address B-SA: Backbone source MAC address I-SID: Backbone service instance identifier S-VID: Service provider VLAN identifier DA: (Customer) destination MAC address SA: (Customer) source MAC address VID: (Customer) VLAN identifier : Priority code point Figure 2. Ethernet frame formats. provider to encapsulate the particularities of the configuration of customer VLANs by a VLAN ID assigned and managed by the service provider. It also addresses the extension to the frame format for inclusion of the customer VLAN tag as well as the service provider VLAN tag, and reserves distinct MAC address spaces for customer and service provider L2 control protocols, respectively (Fig. 2). VLAN stacking (commonly called Q-in-Q) is the most widely used method in today s carrier Ethernet service deployments inside provider networks, but lacks the scalability for crossing multiple operator domains and backbone applications due to the 12-bit limit (~ 4000) of the S- VID. IEEE 802.1ah (Provider Backbone Bridges) is a new amendment to IEEE802.1Q and IEEE802.1ad-2005 allowing provider networks to scale up to 2 24 (~ 16 million) service VLANs by introduction of provider backbone bridges, which are compatible and interoperable with the provider bridges defined by IEEE 802.1ad. At the edge of a provider bridged network, the provider backbone bridge encapsulates customer MAC frames containing the C-VID and an S-VID by assigning a 24-bit service instance identifier inside backbone MAC frames containing the MAC addresses of the source and destination backbone bridges. At the other end of the backbone, the provider backbone bridge extracts the customer MAC frame from the backbone MAC frame and forwards it according to the service instance identifier to the addressed provider bridged network. Due to the encapsulation of customer MAC frames within backbone MAC frames, the protocol is commonly called MAC-in-MAC. IEEE802.1ah is not the only viable solution for extending Ethernet services over large-scale networks. Other protocols like Virtual Private Line Service, specified by RFC 4761 and RFC 4762, may be used as well for interconnection of customer and provider networks. ETHERNET-BASED ACCESS AGGREGATION IN DSL NETWORKS DSL networks are deploying Ethernet services based on Q-in-Q technologies in the access network to aggregate customer traffic, segregate different services, and even provide transparent LAN connectivity with support for customerassigned VLAN-IDs. The Broadband Forum specification TR-101 [4] describes the Ethernet-based access network architecture supporting multiple configurations to connect customer equipment and customer networks to the services of a DSL operator. The specification describes the processing and forwarding of Ethernet frames between the T-reference point toward the customer and the V-reference point toward the broadband network gateway (BNG). To facilitate all the different modes within the same access network infrastructure, C-VIDs and S-VIDs are used in a DSL-specific manner: For business TLS users, a unique S-VID is assigned at the T-interface and preserved throughout the network. For this kind of service the DSL access network strictly follows the recommendations in IEEE 802.1ad for usage and assignment of VLAN tags. For business or residential users with E- Line access to DSL services, unique S-VIDs or unique C-VID/S-VID combinations are assigned and preserved throughout the access network depending on scalability requirements or usage of the C-VID by the customer. For residential users with shared access to DSL services (E-LAN, public access mode), unique S-VIDs are assigned to groups of users or all users subscribing to a particular DSL service. C-VIDs are not used in this case. When Mobile WiMAX is used to provide access to DSL services over a wireless infrastructure, the WiMAX network emulates the behavior of the DSL access network and pro- 88 IEEE Communications Magazine October 2008

4 MS MS NAP GW GW NSP-A AAA PF HA NSP-B AAA PF HA NSP-C AAA PF ASP providing ethernet services Internet ASP providing IP services To become a provider of information and communication services over Mobile WiMAX, it is sufficient to operate a NSP deploying a single for connecting to one or more s and leveraging the mobile access services offered by the WiMAX NAPs. HA Internet Figure 3. Mobile WiMAX network reference architecture. vides Ethernet connectivity between the customer interface and the V-interface the same way as the Ethernet-based DSL aggregation network. MOBILE WIMAX NETWORK ARCHITECTURE The Mobile WiMAX architecture adopts the decomposition of the Internet access network operation into several distinct operator roles. The network access provider (NAP) establishes and operates the radio access network and offers its services to one or multiple network service providers (NSPs), which are in charge of customer-related functions like authentication, service provisioning, and billing, and provide the backbone connectivity to services networks like the Internet or application service providers (ASP) running their particular applications. Aligned to this role model, the Mobile WiMAX network reference architecture is built on two logical networks entities, the access serving network (), providing link layer connectivity and local mobility over the IEEE e radio interface, and the connectivity serving network (), comprising all subscriber-related functions for authentication, authorization, and accounting, as well as the home agent or data path anchor for access to services. There is a direct relation between the and NAP, and the and NSP. The represents a logical access network with all the Mobile WiMAX specific functions that belong to a NAP, and the contains the Mobile WiMAX specific network functions of a NSP. To facilitate interoperable implementations of equipment for WiMAX access networks, the is decomposed into a set of base stations (s) connected to a central control and gateway instance called the -gateway (- GW). The reuse of well-known and widely deployed IP protocols and ISP principles for the requires only a functional specification without further decomposition to allow NSPs to implement the required functions in their core networks. The design of the Mobile WiMAX network architecture allows an to connect to multiple s for load balancing as well as network sharing purposes. To become a provider of information and communication services over Mobile WiMAX, it is sufficient to operate an NSP consisting of a single with connections to one or more s and for leveraging the mobile access services offered by WiMAX NAPs (Fig. 3). Even when it is relatively easy to become a WiMAX service provider by implementing just a single, the adoption of the particularities of an Mobile WiMAX network in a corporate environment and the overhead to establish all the contractual framework to become able to use access connectivity of WiMAX NAPs may be too complex, especially for enterprises and smaller operators just looking for some point-to-point connectivity in areas where they do not have a wired infrastructure. Ethernet services over Mobile WiMAX will offer transparent Ethernet IEEE Communications Magazine October

5 A Metro Ethernet Network provider may extend their business by implementing the functions for Ethernet Services in their networks and may become wireless Ethernet Service providers without the need for huge investments to establish a wireless access infrastructure. Figure 4. Wireless access to Ethernet services networks. connectivity over a wireless access network exactly in the same way as metro Ethernet network providers today offer wired Ethernet services. A metro Ethernet network provider may extend their business by implementing the functions for Ethernet services in their networks and may become a wireless Ethernet service provider without the need for huge investments to establish its own wireless access infrastructure. ETHERNET SERVICES SUPPORT IN THE ACCESS NETWORK Primarily designed for access to the Internet and delivery of IP-based services, the Mobile WiMAX reference architecture is able to handle Ethernet services as well. Different operator roles, with the distinction between NAP and NSP, and the definition of the and, is also applicable to Ethernet services. The main difference to the IP services network architecture is the modification of the data path between the mobile station (MS) and the to support the transport of Ethernet frames. Fortunately, the protocols chosen for the data path for IP services are able to support Ethernet as well. The transport of Ethernet frames over the IEEE e radio interface between the MS and the requires the application of the Ethernet-specific part of the packet convergence sublayer (Ethernet-CS) instead of the IP-CS. The Ethernet-CS supports the transport of Ethernet frames with IEEE e MAC frames and extends the classification capabilities of the CS to Ethernet-specific header fields such as source and destination MAC addresses, Ethernet priority, and VLAN-ID in addition to the IP header fields supported by the IP-CS. The GRE tunneling protocol is deployed between the and the -GW, and supports the encapsulation of Ethernet frames in the same way as the encapsulation of IP packets. GRE may also be used for the connection between and for the MIP data path. When Mobile IP is applied for dynamic tunnel management between the -GW and the, the GRE-based tunnel enables the transport of Ethernet frames in the payload. To enable this ne deployment of Proxy Mobile IPv4 SNI AAA PF Service provider Service provider (PMIPv4), WiMAX makes use of an optional extension of PMIPv4 to signal the mobile host by its 48-bit MS-ID instead of an IPv4 address. Without the demand for dynamic tunnel establishment and tunnel relocation between the -GW and the, any Ethernet transport protocol can be used between and, which is able to forward Ethernet frames based on the MS-ID instead of the destination MAC address and preserve the customer VLAN ID assignment. When the MS is not the end station but contains a bridge forwarding to end stations behind the MS, the Ethernet frames contain destination MAC addresses other than the MS-ID (Fig. 4). ETHERNET SERVICES ANCHOR IN THE A supporting Ethernet services contains the bridging function for forwarding Ethernet frames between connected MSs and the Ethernet service provider. A dedicated bridge port is provided for each of the MSs to ensure compliance with standard bridging behavior. In alignment with the generic Mobile WiMAX network architecture, all payload Ethernet frames going over the radio interface are forwarded across the to the bridge port in the to enable the NSP to take full control on the traffic of subscribers. The configuration of the bridge in the determines which kind of Ethernet service is provided to a particular MS. E-Line service is realized by forwarding the traffic of an MS to a single other end station on either the wireless or wired side of the network. E-LAN service involves multiple other end stations, and the applied forwarding behavior in the bridge determines whether the enterprise LAN or public access mode is realized. Due to its location behind the mobility anchor in the, the bridge does not have to cope with mobility issues in the access network. From the perspective of the bridge, the MS always appears on the same bridge port like in today s fixed Ethernet networks, not imposing any new requirement on the bridging functionality for support of Ethernet services over a cellular infrastructure. The dynamics of the access network in a cellular infrastructure requires management func- 90 IEEE Communications Magazine October 2008

6 tions by a control plane, which allow the instantaneous provisioning of any kind of Ethernet services to any place in the access network. Such functions are not known in current fixed access networks for Ethernet services. The approach taken in Mobile WiMAX is the reuse of the existing control plane for IP services. In addition to the adaptation of the data path, there are only minor modifications necessary in the control protocols of the Mobile WiMAX access network to support Ethernet services. The following chapter explains the reuse of the existing control plane for Ethernet services and presents the few places where enhancements are necessary. REUSE OF THE MOBILE WIMAX CONTROL PLANE The Mobile WiMAX control plane comprises all the functions to establish, maintain, and tear down mobile connectivity in a cellular network based on the IEEE e radio standard. The specification for IP services [5] defines the following control plane functions. Most of the functions are applicable to Ethernet services without any modifications, but some of them have to be amended to support Ethernet services. Network Entry Discovery and Selection/Reselection describes the procedures of an MS to scan and detect the available WiMAX access networks, as well as to choose the preferred NAP for connecting to the home NSP. This section is applicable to Ethernet services without modifications. WiMAX Key Hierarchy and Distribution specifies the generation, derivation, and distribution of all the keying material needed in the Mobile WiMAX access network. This section is applicable to Ethernet services without modifications. Authentication, Authorization and Accounting describes the procedures for the network access authentication and authorization according to the user profile of the subscription, and the accounting procedures for measuring and signaling the usage of the access network by a particular subscriber. While the authentication procedures are applicable to Ethernet services without modifications, authorization was extended to enable Ethernet-specific user profiles. Not applicable to Ethernet services is the accounting model of IP services, which is based on the status of the IP session. Accounting events for Ethernet services are based on the status of Ethernet connectivity, which fully depends on the establishment of the link layer session and the service flows making use of the Ethernet CS. Network Entry and Exit describes the procedures for establishing initial connectivity to a Mobile WiMAX network after network entry detection and selection, and the procedures for terminating the network connectivity orderly. This section is applicable to Ethernet Services without modification. QoS and SFID Management defines the procedures for creation, modification, and deletion of the initial and further preprovisioned service flows, as well as the management of service flow identifiers (SFIDs) and the static quality of service (QoS) policy provisioning. This section got a major amendment to support dynamic QoS for Ethernet services because it is not acceptable to tear down a connection completely just to install or modify the service parameters of a service flow (e.g., for adding another VLAN to a bundle of established VLANs on a link). Ethernet connections may carry a number of VLANs in parallel, and it is necessary to add, modify, or remove service flows assigned to particular VLANs while other service flows are carrying VLANs with missioncritical applications over the same link. Furthermore, Ethernet-specific attributes were added for describing the classification and QoS parameters of service flows carrying Ethernet frames. Anchored Mobility Management describes the handover of radio links across s inside a single or across s without change of the anchor. This section is applicable to Ethernet services without modifications. Anchored Mobility Management describes mobility management based on Mobile IP across s with the mobility anchor located in the. A new part was added to the Proxy MIPv4 specification to make this section applicable to Ethernet services for the transport of Ethernet frames over PMIPv4 managed tunnels. An additional attribute is used to allow signaling of the MSID in the Mobile IP protocol. Radio Resource Management is a function to increase the radio resource usage efficiency within an. This section is applicable to Ethernet services without modifications. Paging and Idle-Mode MS Operation describes the control procedures for location update, paging, and entering and leaving the idle mode according to the specifications in IEEE e. Even when idle mode may be a rarely used function for Ethernet services, this section can be applied to Ethernet services without modification. Two other functions of the Mobile WiMAX control plane are specific to IP services and are not used for Ethernet services: IPv4 Addressing describes the assignment of IPv4 addresses to MSs via DHCP, PMIPv4, and CMIPv4. This section is not applicable to Ethernet services. The section on IPv6 defines the operation of IPv6 in the Mobile WiMAX access network. This section is not applicable to Ethernet services. As explained in the list above, most of the existing Mobile WiMAX control plane is applied to Ethernet services without any modifications. A few functions accounting, QoS management, and anchored mobility management required Ethernet-specific amendments, which can coexist with the IP specific functions inside the same access network. Coexistence is highly important to allow a Mobile WiMAX access network to provide IP services as well as Ethernet services concurrently over the same The approach taken in Mobile WiMAX is the reuse of the existing control plane for IP services. In addition to the adoption of the data path, there are only minor modifications in the control protocols of the Mobile WiMAX access network to support Ethernet Services. IEEE Communications Magazine October

7 Mobile WiMAX network User 1 User 2 T MS NAP GW NAP Other network services A10 NSP NSP BNG L2TS L2TP NSP 1 User 3 CPE User 4 T Customer prem. net NID U Access loop MDF V-interworking Access node DSLAM Access network V Ethernet aggreg. BB network gateway IP Regional broadband network A10 NSP QoS-IP A10 NSP QoS-IP A10 ASP NSP 2 ASP 1 WiMAX network emulates DSL network between T and V interface Figure 5. Mobile WiMAX interworking with DSL networks. infrastructure to support participation in all the telecommunication markets out of a single cellular infrastructure. Support of Ethernet does not require a new network architecture or any new functional entities in the network. The support of Ethernet services is smoothly integrated into the Mobile WiMAX network architecture, and Ethernet services can be operated parallel to IP services in the same network. INTERWORKING WITH DSL NETWORKS An important usage model of Ethernet services over Mobile WiMAX is interworking with DSL networks to offer DSL services over a wireless infrastructure. The WiMAX network provides a DSL conformant T reference point to the subscriber and connects the user interface with Ethernet to the V aggregation point of the DSL network. DSL-specific network functions in the Mobile WiMAX network with support for Ethernet services realize the exact network behavior for Ethernet-based aggregation according to DSL Forum TR-101. DSL user authentication is performed by the DSL network across the Ethernet connectivity of the WiMAX network either within the PPPo- ETH protocol or implicitly by DHCP options when IPoETH is deployed. The WiMAX security framework with PKMv2 is used to establish secure Ethernet connections over the IEEE e radio interface based on device or user identities with the credentials stored in the MS. The identities are used to manage the provisioning and accounting of Ethernet connectivity across the WiMAX network according to the profiles stored in the AAA server in the. Essentially there is no difference between device authentication and user authentication in the DSL interworking case. The identity always points to a particular MS, and the difference is only whether the identity is hard- or soft-coded in the MS (Fig. 5). RELATED STANDARDIZATION ACTIVITIES The specifications for Ethernet services over Mobile WiMAX as described by this article are part of WiMAX Network Release 1.5 of the Network Working Group in the WiMAX Forum. Accompanying standardization topics were addressed in the 16ng Working Group (WG) of the Internet Engineering Task Force (IETF) as well as within the REV2 project of IEEE P The 16ng WG has a specification on transmission of IP over Ethernet over IEEE networks [6] that provides the generic architectural framework for Ethernet networks over IEEE , and specifies a number of enhancements to the bridging function on the network side to increase the efficiency of the radio resource usage and reduce the power consumption of terminals when running IP over Ethernet over a cellular network. The IEEE P802.16REV2 task group created a revision of the IEEE standard, which incorporates the IEEE , IEEE e, IEEE f, and IEEE g standards into a single document. Within this effort 92 IEEE Communications Magazine October 2008

8 the specification of the Ethernet-specific part of the packet convergence sublayer was refined to make its application less cumbersome. In particular, it became possible to use the same Ethernet CS for Ethernet frames with or without IPv4 or IPv6 payload optionally tagged by VLAN IDs and priority bits. CONCLUSION This article presents the current state of support for Ethernet services over Mobile WiMAX. The approach of the WiMAX community is to align the Ethernet service provisioning model as closely as possible to the model for IP services. It reduces not only the necessary standardization efforts for developing the specifications but also enables the development of WiMAX network equipment, which serves IP as well as Ethernet out of the same box. Such equipment can be deployed by any kind of WiMAX network operator, is well prepared for the evolution of services into broader telecommunication markets, and provides high commonality, which finally leads to better scale of economies. With the biggest part of the investments of a network operator going into the access infrastructure, it is important to enable the most flexible deployment of the access network. Participation in the growing market for Ethernet services without the prerequisites of huge investments may considerably contribute to a sustainable business case for a wireless broadband access provider. Mobile WiMAX supports an integrated approach to provide fixed, nomadic, and mobile IP services and Ethernet services out of the same network infrastructure. REFERENCES [1] Metro Ethernet Forum, MEF 6 Ethernet Services Definition Phase 1, June [2] IEEE 802.1Q-2005, Virtual Bridged Local Area Networks. [3] IEEE 802.1ad-2005, Amendment 4: Provider Bridges. [4] Broadband Forum TR-101, Migration to Ethernet-Based DSL Aggregation, Apr [5] WiMAX Forum Network Architecture, Stages 2 and 3, Release 1 v. 1.2; age_2-3_rel_1v1.2.zip [6] H. S. Jeon, M. Riegel, and S. J. Jeong Transmission of IP over Ethernet over IEEE Networks, draft-ietf- 16ng-ip-over-ethernet-over txt, work in progress. BIOGRAPHY MAX RIEGEL (maximilian.riegel@nsn.com) is head of WiMAX and IEEE standardization at Nokia Siemens Networks. He is engaged in the WiMAX Forum as one of the co-chairs of the Networking Working Group, and participates in the 16ng working group of the IETF as technical advisor and contributor. He has more than 25 years experience in the telecommunication industry with more than 15 years of professional experience in technical and operational issues of the Internet. After more than 10 years in different management positions in product development for telecommunication equipment within several companies, he joined Siemens in 1998, taking over management of IETF standardization. Also participating in the IEEE 802 standardization from 2000 on, he has become one of the experts in mobile broadband wireless Internet access with deep involvement in the Mobile WiMAX radio and network standardization from its very beginning. He has a Dipl.-Ing. degree in electrical engineering from the Technical University of Munich, Germany. Participation in the growing market for Ethernet Services without the prerequisites of huge investments may considerably contribute to a sustainable business case for a wireless broadband access provider. IEEE Communications Magazine October