Ethernet in the First Mile (EFM), also known as IEEE 802.3ah, is defined as a collection of protocols specified in IEEE 802.3, defining the Ethernet in the access networks, i.e. first or last mile.
The first mile (also called the last mile, the subscriber access network, or the local loop), is the link between the end user and the public network. On a typical LAN setting DSL and cable modems operate at a modest 5-10% of the LAN setup’s total capacity which causes application bottlenecks. Bottlenecks happen even with E1 lines, at speeds of 1.5 Mbps. Though E1 lines are faster they are expensive.
Ethernet in the first mile (EFM)
can overcome this, using existing physical infrastructure whether it is ordinary telephone lines or dark fibre links. This technique is claimed to be the new highly resilient copper based Ethernet service, with the ability to transfer high bandwidth data at up to 10 Mbps speeds into users’ premises without the need for any end-to-end fibre leased lines.
An important aspect of the EFM is that it does not offer any improvement over nor replace existing equipment but it is just a set of additional specifications that will enable users to run Ethernet protocol over previously unsupported media, such as single pairs of telephone wiring and single strands of single-mode fibre (SMF). It is more suited for subscriber access networks – networks that connect subscribers to their respective service providers.
The access network in many areas is made up of copper cable based point to point connections and EFM can easily blend with the copper infrastructure because EFM mixes new technology with ‘old world’ copper in the first mile. As a network access technology, Ethernet offers a long list of quantitative and qualitative advantages over legacy first mile technologies.
With Ethernet there is only one interface required and unlike traditional E1, E3 and STM-1 interfaces, Ethernet significantly brings down the need to keep interfaces in stock and train technicians to install and maintain them. This means that companies can save on their expenditure by adopting Ethernet. Ethernet offers true un-contended, symmetric and guaranteed bandwidth that is easy to run QoS (Quality of Service) over.
On the other hand with leased lines the installation lead-in times, cost of installation and the maintenance and access fees imposed upon the line subscriber often make it unaffordable to small businesses.
Ethernet in the First Mile requires dedicated copper pairs and multiple pairs can be bonded together to realise more bandwidth. Theoretically speeds up to 100Mbit/s can be reached with this type of bonding and in UK there are providers who offer speeds up to 40Mbits/s by making use of the copper pairing technique.
One downside of this is the availability of bandwidth is inversely proportional to the distance of the access network. If the end user is located far away from the public network then there will be a decrease in the amount of bandwidth available to the end user. As EFM is delivered over normal Metallic Path Facility (MPF) copper pairs, in the event of fault users can expect the same kind of service levels to that of a DSL line. Also studies have indicated that there are only less exchanges available that support EFM services and that amount is nowhere near to traditional leased lines and private circuits. Users can realise the full potential of the EFM only when connected to an enabled exchange.
Also EFM is more suited for speed ranges between 10Mbit/s - 20Mbit/s. But if a company is looking for higher capacities and mission critical SLAs then traditional private circuits will still be the optimal choice for them.
The disadvantages of EFM arise largely due to the fact that it is a new technology and in the near future users can expect newer equipment and enhanced protocols that aim to minimise these setbacks. But it can be stated that EFM point-to-point technologies are very similar to existing Ethernet, and its layout of connected devices provides advantageous and cost-effective opportunities for replacing expensive E1 and E3 links.