A means of uniquely identifying a device on a network.

The multicast destination address of all ones, defined as the group of all stations on a network. The standard requires that every station must receive and act upon every Ethernet frame whose destination address is all ones.

The set of all nodes connected in a network that will receive each other’s broadcast frames. All Ethernet segments connected with a Layer 2 bridge are in the same broadcast domain. Virtual LANs (VLANs) can be used to establish multiple broadcast domains in an Ethernet system based on switches.

Class of Service. The IEEE 802.1Q standard provides an extra field in the Ethernet frame to hold both a VLAN identifier and Class of Service tags. The Class of Service tag values are defined in the IEEE 802.1p standard.

Layer 2 of the OSI reference model. This layer takes data from the network layer and passes it on to the physical layer. The data link layer is responsible for transmitting and receiving Ethernet frames.

The process of moving frames from one port to another in a switch.

The maximum number of frames that can be forwarded by a switch, typically measured in frames per second.

The fundamental unit of transmission at the data link layer.

A signal transmission path that can support simultaneous data transmission and reception.

A communications method that allows a device to simultaneously send and receive data.

A version of Ethernet that operates at 1 billion (1,000,000,000) bits per second.

A measure of the delay experienced in a system. In Ethernet switches, latency is the time required to forward a packet from the input (ingress) port to the output (egress) port.

Link Aggregation Control Protocol. The IEEE 802.1AX Link Aggregation standard allows multiple parallel Ethernet links to be grouped together, functioning as a single “virtual” channel. A given packet flow over the channel is limited to a single link in the channel; therefore, single packet flows cannot exceed the speed of the individual links. However, multiple packet flows will be distributed across multiple links in the channel, resulting in an aggregate throughput for multiple flows that is the sum of the speeds of the individual links in the group. Link aggregation was first defined in the IEEE 802.3ad standard, and later moved to become IEEE 802.1AX.

See [entry_five].

Defined in the IEEE 802.3 specifications as a point-to-point segment that connects two—and only two—devices.

Media Access Control. A protocol defining a set of mechanisms operating at the data link layer of a local area network. The MAC protocol is used to manage access to the communication channel.

The 48-bit address used in Ethernet to identify a station interface.

Management Information Base. A list of manageable objects (counters, etc.) for a given device; used by management applications.

Multiple Spanning Tree Protocol. Originally defined in the IEEE 802.1s supplement to the IEEE 802.1Q standard. This version of spanning tree adds the ability for switches supporting VLANs to use multiple spanning trees, providing for traffic belonging to different VLANs to flow over different paths within the network. MSTP is an optional spanning tree protocol that is supported in some switches.

A multicast address allows a single Ethernet frame to be received by a group of stations. If the first bit of the destination address transmitted on the Ethernet channel is a one (1), then the address is a multicast address.

Network Interface Card. Also called an adapter or interface card. The set of electronics that provides a connection between a computer and an Ethernet cable.

Open Systems Interconnection. A seven-layer reference model for networks, developed by the International Organization for Standardization (ISO). The OSI reference model is a formal method for describing the interlocking sets of networking hardware and software used to provide computer communications over a network.

Organizationally Unique Identifier. A 24-bit value assigned to an organization by the IEEE. Ethernet vendors use the 24-bit OUI they receive from the IEEE in the process of creating unique 48-bit Ethernet addresses. Each Ethernet device a vendor builds is provided with a unique 48-bit address, whose first 24 bits are composed of the vendor’s OUI.

A unit of data exchanged at the network layer.

A connection point for a cable. Ethernet switches provide multiple ports for connecting Ethernet devices.

Quality of Service. QoS is typically achieved by providing different levels of service priority for packet transmission such that, in the event of congestion on a switch port, higher priority packets are served first and lower priority packets are more likely to be dropped. Class of Service bits are used to provide priority tagging on Ethernet frames.

A device or process based on Layer 3 network protocols, used to interconnect networks at the network layer.

Rapid Spanning Tree Protocol. Initially defined in the 802.1w supplement to the 802.1D standard, RSTP is an improved version of the spanning tree protocol which is interoperable with the classic STP. RSTP provides significantly faster spanning tree convergence in a Layer 2 network composed of Ethernet switches.

An Ethernet media segment is made up of a section of cable for carrying Ethernet signals.

Simple Network Management Protocol. A protocol specified by the Internet Engineering Task Force (IETF) for exchanging network management information among network devices and network management stations.

A unique, addressable device on a network.

Spanning Tree Protocol. The “classic” spanning tree protocol, defined in the IEEE 802.1D MAC layer bridging standard. The most recent version of the standard, IEEE 802.1D-2004, obsolesced classic STP and replaced it with the Rapid Spanning Tree Protocol.

The rate at which usable data can be sent over the channel. While an Ethernet channel may operate at 100 or 1000 Mbps, the throughput in terms of usable data will be less, due to the number of bits required for framing and other channel overhead.

The physical or logical layout of a network.

Virtual LAN. A method in which a port or set of ports in a switching hub are grouped together and function as a single “virtual” network. All ports within a given VLAN are members of the same broadcast domain.