Ethernet Active Line Access: Technical Requirements
Discussion Document : To accompany the policy consultation document: Delivering super-fast broadband in the UK
1.1 This document accompanies the policy consultation document ‘Delivering super-fast broadband in the UK ’[ (-1-)].
1.2 The delivery of next generation broadband services is likely to require an upgrade to the local access infrastructure. The existing network topology of copper wire running from the exchange to the customer premises will not be able to support the wide range of new, faster services that are being proposed by operators. This change in the access network will most likely require the development of a new range of competitive options for the provision of broadband services.
1.3 Ethernet Active Line Access (ALA) is our current vision for the set of requirements for one of the competitive options in Next Generation Access. It is designed to enable the provision of innovative services to customers through a wholesale bitstream product that is as close as possible to access at the physical layer of the network. It is most likely to be attractive to Communications Providers (CPs) where it might not be possible or practical to require shared passive access to infrastructure. As far as possible, Ethernet ALA should offer CPs a similar scope for innovation and control as they would have with direct access to the passive infrastructure. Therefore, the functionality of products based on Ethernet ALA requirements should be as close as possible to the functionality of the underlying infrastructure, i.e. at the lowest possible OSI[ (-2-)] layer.
1.4 Competition, based on NGA networks, is likely to take many different forms depending on the local conditions and the state of market development. Passive access methods such as sub-loop unbundling and duct sharing, and active access methods such as bit-stream, may all have a role to play. A range of competitive options is shown in the diagram below.
Figure 1: Examples of active and passive remedies being considered by Ofcom
1.5 Regulators favour passive access as it provides CPs with the greatest level of control over the underlying infrastructure. This, in turn, provides the greatest scope for innovation, allowing CPs to lower prices and develop new products. However, in some cases physical and economic conditions may not allow passive access, and so active line access may be the more viable option. Within active access, regulators prefer local (i.e. exchange based) active line access over more centralised (aggregated) active line access.
1.6 In the case of active line access, we believe that it would be beneficial to CPs using ALA[ (-3-)] and ultimately end-users if the bit-stream products available had two general characteristics:
1.6.1 That they provide the maximum opportunity to innovate (i.e. were implemented at lowest possible OSI layer); and
1.6.2 That all NGA operators use a common set of requirements, to simplify interconnection/interoperability and avoid local variations in service offerings. Any local variations (or ‘technology islands’) would reduce economies of scale and limit benefits to end-customers.
1.7 Ofcom is technology neutral, but it makes sense to propose an interface technology to facilitate the development of ALA. There are a number of technical issues associated with ALA that would be difficult to address on a generic basis. The interface technology needs to be infrastructure agnostic, well established and have the scope to deliver innovative services. Ethernet is simple, cheap, ubiquitous and well developed. There is a wide availability of low cost equipment and it is well standardised. It supports flexible bandwidth, excellent interoperability, and security and QoS protocols. It operates at a low OSI layer allowing innovation in services and the standard is being adopted by telecommunications companies around the world for transport of IP based services. In consultation with industry[ (-4-)], the use of Ethernet for ALA has been an uncontroversial choice.
1.8 Ofcom has identified a series of characteristics that should be considered for inclusion in Ethernet ALA to support effective competition using this access. These characteristics are security enablement, Quality of Service (QoS) enablement, multicast enablement, flexible customer premises equipment (CPE), and flexible interconnection/aggregation. The characteristics were identified as those areas of functionality that would be required to give CPs using ALA users a level of control and scope for innovation that is as close to passive access as possible.
1.9 This document sets out in detail our proposals for the minimum technical requirements for Ethernet ALA, based on the five characteristics. The requirements are designed to facilitate the definition of standards by industry, and Ofcom hopes that the appropriate standards bodies will take the development of Ethernet ALA forward. Once defined, the standards will allow the creation of wholesale products by ALA providers which will deliver Ethernet ALA to ALA users. The full process, with the remit of each stakeholder, is shown in the figure below.
Figure 2: Development of Ethernet ALA with remit of stakeholders
1.10 The requirements are presented for discussion and Ofcom is looking to receive feedback on this first draft. The requirements are designed to provide a common reference for industry, around which stakeholders can engage. It should be noted that the requirements are for technical functionality, not a specific wholesale product (or products). Ofcom expects that, once agreed within industry, the requirements could be met by multiple products that would be chosen according to the specific physical and economic conditions in each implementation. It should also be noted that the requirements are for core, minimum functionality, and should not preclude additional functionality being included, except where it would contradict an existing requirement.
1.11 The first group of requirements are general requirements that reflect the basic aims of Ethernet ALA: innovation, customer choice and standardisation. The access should be independent of the network technology underlying it (e.g. VDSL, PON, PtP fibre, WiFi, etc). The access interface should be at the lowest possible OSI layer to maximise the scope for innovation in the layers above. In the case where multiple ALA users supply a customer, the customer should have the choice to decide how their services are prioritised. ALA should also align with the wider characteristics of Carrier Ethernet.
1.12 Further technical requirements for an ALA user’s interface with Ethernet ALA are grouped under the five characteristics. ALA should separate different traffic streams and allow ALA users to implement their own security measures. ALA should support QoS according to current industry standards. Multicast should also be supported, with ALA users having the choice of using ALA provider equipment or installing their own solution. There should be support for flexible customer premises equipment (CPE), and these requirements suggest the position of the user network interface for Ethernet ALA. Finally, the interconnection point should be flexible and should be available at a national, regional and local level.
1.13 Although beyond the scope of these requirements, a discussion around additional characteristics required by an ALA service is also included. The systems and business process for Ethernet ALA should be as close as possible to those currently employed. The relative benefits of a common ordering approach should be investigated. Migrations should be as straightforward as possible, i.e. for customers, both onto the new technology and between ALA users, and also for ALA users between interconnection points. Finally, management protocols, such as Ethernet OAM, should also be explored.
1.14 This document is targeted at standardisation bodies, infrastructure providers, wholesale providers, potential purchasers of ALA products ( ALA users), regulators and other interested parties.
1.15 The requirements set out in this document suggest the core, minimum functionality of Ethernet ALA. We hope that these requirements will provide a framework to facilitate the development of standards for competitive active line access, and would encourage all industry stakeholders to engage in the process and provide feedback. We further hope that once developed, Ethernet active line access will support a diverse and competitive NGA market with benefits for all consumers.
2.-Terminology associated with the layers of the OSI protocol stack is used throughout this document. The focus is on the lower 3 layers of the stack: physical, data-link and network. Further detail on the functionality of the stack can be found in Annex 2.
3.- ‘ ALA users’ are those communications providers that would purchase wholesale ALA-based products.
The full document is available below