Aggregating Subscriber Traffic

If the benefits of Ethernet in terms of cost and ease of deployment are obvious for the first mile, because the Ethernet in the First Mile (EFM) technology was designed to be cost-effective and simple, this is not necessarily the case for the aggregation network, the layer-2 network that provides connectivity between the subscribers of a certain service provider and a Broadband Access Server (BRAS) or an IP service edge that interfaces with the IP core network. The technology for the aggregation network can be selected independently of the technology in the first mile, provided that there is adequate protocol conversion at the end of the first mile (remote unit, DSLAM, access multiplexer).

The functions of the aggregation network are unavoidably more complex than those of the first mile. The first mile is a simple point-to-point connection (or virtual point-to-point connection, in the case of EPON), taking in data on one end and handing it to the client at the other end. The aggregation network is a complex topology where measures must be taken to use the available bandwidth as efficiently as possible while avoiding congestion, support different levels of Quality of Service (QoS), and prohibit potentially harmful traffic from malicious subscribers to reach other subscribers equipment; in brief, it...