RAD - L

Last Mile - (Sometimes referred to as Local Loop). The final leg of delivering communications connectivity to a resident or customer. Typically seen as an expensive challenge because “fanning out” wires and cables is a considerably expensive and physically difficult task.

Latency - The time between initiating a request for data and the beginning of the actual data transfer. Network latency is the delay introduced when a packet is momentarily stored, analyzed and then forwarded.

Leased Line - A permanent telephone connection between two points that is rented for exclusive use from a telecommunications common carrier. In contrast to a normal dial-up connection, a leased line is always active. Typically, the highest speed data connections require a leased line connection. For example, a T1 channel is a type of leased line that provides a maximum transmission speed of 1.544 Mbps.

Loopback - A type of diagnostic test in which the transmitted signal is returned to the sending device after passing through all or part of a communications link or network.

MAC (Media Access Control) - A protocol that defines the way workstations gain access to transmission media, most widely used in reference to LANs. For IEEE LANs, the MAC layer is the lower sublayer of the data link layer protocol.

MAN (Metropolitan Area Network) - A network that provides regional connectivity within a metropolitan area (such as a city).

Master Clock - The source of timing signals (or the signals themselves) that all network stations use for synchronization.

MEF (Metro Ethernet Forum) - A non-profit organization chartered with the mission of accelerating the adoption of optical Ethernet as the technology of choice in future metro networks worldwide. Ethernet was chosen for its relative simplicity and popularity with end-users, as well as for lowering costs of Ethernet equipment.

MPLS (Multiprotocol Label Switching) - A standards-approved technology that allows core network routers to operate at higher speeds without needing to examine each packet in detail, allows more complex services to be developed, enabling discrimination on a QoS basis. MPLS speeds up network traffic flow by bringing Layer 2 information to Layer 3 (IP) and facilitating network management. It forwards traffic using a label that instructs the routers and the switches in the network where to forward the packets based on pre-established IP routing information. MPLS is called multiprotocol because it works with the IP, ATM, and Frame Relay network protocols.

Multiplexer - At one end of a communications link, a device that combines several lower speed transmission channels into a single high speed channel. A multiplexer at the other end reverses the process. Sometimes called a mux. See Bit Interleaving/Multiplexer.

Multiplexer (Mux) - A device allowing two or more signals to pass over and share a common transmission path simultaneously.

Network - (1) An interconnected group of nodes. (2) A series of points, nodes, or stations connected by communications channels; the collection of equipment through which connections are made between data stations.

Node - A point of interconnection to a network.

OAM (Operation Administration and Maintenance) - A set of network management functions that provide for network fault and performance management, analysis and fault isolation. OAM functions exist in carrierclass TDM and ATM networks, but are now also being implemented in MPLS and Ethernet networks. These capabilities will provide the basic tools for carriers to monitor, diagnose, and troubleshoot first-mile Ethernet access links.