Ethernet is a widely deployed technology, renowned for its robustness and cost-effectiveness. Standardscompliant interfaces are available on a plethora of data communication/telecommunication devices at line rates of 10/100/1000 Mbps, and the draft-standard for 10 Gbps has recently been ratified.
In Metropolitan Area Networks (MANs), Ethernet has the potential to increase network capacity costeffectively and offer a wide range of services in a simple, scalable, and flexible manner. An Ethernet-based MAN is generally termed a Metro Ethernet Network (MEN), although some European service providers have also introduced MEN-like technology for Wide Area Networks (WANs).
In enterprise networks, Metro Ethernet is used primarily for two purposes: connectivity to the public Internet and connectivity between geographically separate corporate sites — an application that extends the functionality and reachability of corporate networks. Figure 1 illustrates the key areas of interest in a MEN and sets the scene for the balance of this white paper.
A. Links are primarily point-to-point and can be any speed of Ethernet.
B. Nodes can be either switches or routers, depending on their location in the MEN,
the nature of the services being provisioned, and the level of service resilience
(network protection). Nodes are meshed to whatever degree necessary to provide
the desired connectivity, services, and protection.
C. WAN links connect MENs together across large distances.
D. Ethernet services can be topologically classified into point-to-point
(as shown in this illustration), multipoint-to-multipoint, or point-to-multipoint.
Services are then further classified according to the bandwidth provisioned and
used. This bandwidth usage can be exclusive or shared across multiple users.
Bandwidth is provisioned on demand from 1 Mbps to 1 Gbps, in increments as fine
as 1 Mbps.
E. Varying degrees of service resilience are obtained by implementing a combination
of network protection techniques. Protection can be end-to-end (as shown in this
illustration) or node-to-node.
F. Quality of Service (QoS) is realized using a combination of various techniques to
provide both ‘hard’ and ‘soft’ bandwidth and packet-loss guarantees. QoS can be
end-to-end (as shown in this illustration) or nodeto-node.
From an enterprise end-customer perspective, QoS is visible as a technical /
operational Service Level Specification (SLS), which is underwritten by a
commercial Service Level Agreement (SLA).