A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment or it can be bridged to other LAN segments.
Ethernet is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. Ethernet has since been refined to support higher bit rates, a greater number of nodes, and longer link distances, but retains much backward compatibility. Over time, Ethernet has largely replaced competing wired LAN technologies such as Token Ring, FDDI and ARCNET.
A network switch is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.
Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.
The Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. Spanning tree also allows a network design to include backup links providing fault tolerance if an active link fails.
A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer. In this context, virtual refers to a physical object recreated and altered by additional logic, within the local area network. Basically, a VLAN behaves like a virtual switch or network link that can share the same physical structure with other VLANs while staying logically separate from them. Between network devices, VLANs work by applying tags to network frames and handling these tags in networking systems –creating the appearance and functionality of network traffic that is physically on a single network but acts as if it were split between separate networks. In this way, VLANs can keep network applications separate despite being connected to the same physical network, and without requiring multiple sets of cabling and networking devices to be deployed.
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer.
A multilayer switch (MLS) is a computer networking device that switches on OSI layer 2 like an ordinary network switch and provides extra functions on higher OSI layers. The MLS was invented by engineers at Digital Equipment Corporation.
Unidirectional Link Detection (UDLD) is a data link layer protocol from Cisco Systems to monitor the physical configuration of the cables and detect unidirectional links. UDLD complements the Spanning Tree Protocol which is used to eliminate switching loops.
The Multiple Spanning Tree Protocol (MSTP) and algorithm, provides both simple and full connectivity assigned to any given virtual LAN (VLAN) throughout a bridged local area network. MSTP uses bridge protocol data unit (BPDUs) to exchange information between spanning-tree compatible devices, to prevent loops in each Multiple Spanning Tree instance (MSTI) and in the common and internal spanning tree (CIST), by selecting active and blocked paths. This is done as well as in Spanning Tree Protocol (STP) without the need of manually enabling backup links and getting rid of switching loop danger.
A network bridge is a computer networking device that creates a single, aggregate network from multiple communication networks or network segments. This function is called network bridging. Bridging is distinct from routing. Routing allows multiple networks to communicate independently and yet remain separate, whereas bridging connects two separate networks as if they were a single network. In the OSI model, bridging is performed in the data link layer. If one or more segments of the bridged network are wireless, the device is known as a wireless bridge.
A broadcast storm or broadcast radiation is the accumulation of broadcast and multicast traffic on a computer network. Extreme amounts of broadcast traffic constitute a broadcast storm. It can consume sufficient network resources so as to render the network unable to transport normal traffic. A packet that induces such a storm is occasionally nicknamed a Chernobyl packet.
A forwarding information base (FIB), also known as a forwarding table or MAC table, is most commonly used in network bridging, routing, and similar functions to find the proper output network interface controller to which the input interface should forward a packet. It is a dynamic table that maps MAC addresses to ports. It is the essential mechanism that separates network switches from Ethernet hubs. Content-addressable memory (CAM) is typically used to efficiently implement the FIB, thus it is sometimes called a CAM table.
In wired computer networking a hop occurs when a packet is passed from one network segment to the next. Data packets pass through routers as they travel between source and destination. The hop count refers to the number of network devices through which data passes from source to destination.
IEEE 802.1aq is an amendment to the IEEE 802.1Q networking standard which adds support for Shortest Path Bridging (SPB). This technology is intended to simplify the creation and configuration of Ethernet networks while enabling multipath routing.
IEEE 802.1ad is an amendment to the IEEE 802.1Q-1998 networking standard which adds support for provider bridges. It was incorporated into the base 802.1Q standard in 2011. The technique specified by the standard is known informally as stacked VLANs or QinQ.
High-availability Seamless Redundancy (HSR) is a network protocol for Ethernet that provides seamless failover against failure of any single network component. PRP and HSR are independent of the application-protocol and can be used by most Industrial Ethernet protocols in the IEC 61784 suite. HSR does not cover the failure of end nodes, but redundant nodes can be connected via HSR.
Parallel Redundancy Protocol (PRP) is a network protocol standard for Ethernet that provides seamless failover against failure of any network component. This redundancy is invisible to the application.
In computer networking, a unicast flood occurs when a switch receives a unicast frame and the switch does not know that the addressee is on any particular switch port. Since the switch has no information regarding which port, if any, the addressee might be reached through, it forwards the frame through all ports aside from the one through which the frame was received.
The link layer is the lowest layer in the TCP/IP model. It is also referred to as the network interface layer and mostly equivalent to the data link layer plus physical layer in OSI. This particular layer has several unique security vulnerabilities that can be exploited by a determined adversary.
