100 Mbps Fast Ethernet system based on 4B/5B signal encoding transmitted over fiber optic cable utilizing 1300 nm fiber optic technology.
850 nm fiber optic technology that supports auto-negotiaton. 100BASE-SX devices can communicate with 10BASE-FL devices at 10 Mbps and other 100BASE-SX devices at 100 Mbps.
A Protocol defined in the Ethernet standard that allows devices at either end of a link segment to advertise and negotiate modes of operation such as the speed of the link, half- or full-duplex operation and full-duplex flow control.
A protocol which allows two Ethernet devices to negotiate their use of the Ethernet TX and RX cable pairs. This allows two Ethernet devices with MDI-X or MDI connectors to connect without using a crossover cable. This feature is also known as Auto-crossover.
Twisted-pair cable with electrical characteristics suitable for all twisted-pair Ethernet media systems, including 10BASE-T and 100BASE-TX. Category 5 and Category 5e cable are preferred cable types for structural cabling systems.
An enhanced version of Category 5 cable, developed to improve certain cable characteristics important to Gigabit Ethernet operation. It is recommended that all new structured cabling systems be based on Category 5e cable; however, this cable may not be the best for use in industrial installations because of noise susceptibility.
A twisted-pair patch cable wired in such a way as to route the transmit signals from one piece of equipment to the receive port of another piece of equipment, and vice versa. This allows communication between two peer devices. The opposite of a crossover cable is the straight-through cable.
Data Link Layer
Layer 2 of the OSI reference model. This layer passes data between the network layer and the physical layer. The data link layer is responsible for transmitting and receiving frames. It usually includes both the media access control (MAC) protocol and logical link control (LLC) layers.
The ability of a switch to observe Internet Group Multicast Protocol (IGMP) traffic in order to learn IP Multicast group membership for the purpose of restricting multicast transmissions to only those ports which have requested them.
See a tutorial on IGMP Snooping
A failure of the network in which the collision indication arrives too late in the frame transmission to be automatically dealt with by the medium access control (MAC) Protocol. The defective frame may not be detected by all stations requiring that the application layer detect and retransmit the lost frame, resulting in greatly reduced throughput.
Link Integrity Test
This test verifies that an Ethernet link is connected correctly and that signals are being received correctly. This is a helpful aid but does not guarantee the link is completely functional.
A unique address assigned to a station interface, identifying that station on the network. With Ethernet, this is the unique 48-bit station address. It is also known as the physical address.
Signal encoding method used in all 10 Mbps Ethernet media systems. Each bit of information is converted into a "bit symbol" which is divided into two halves. One half is high and the other is low. Manchester encoding results in a 20 Mbaud stream although data is only being sent at 10 Mbps.
Medium Dependent Interface. The name for the connector used to make a physical and electrical connection between a transceiver and a media segment. For example, the RJ-45-style connector is the MDI for 10BASE-T and 100BASE-TX.
An MDI port on a hub or media converter that implements an internal crossover function. This means that a "straight-through" patch cable can be used to connect a station to this port, since the required signal crossover is performed inside the port instead of in the cable.
Management Information Base. An MIB describes a set of managed objects. An SNMP management console application can manipulate the objects on a specfic computer if the SNMP service has an extension agent DLL that supports the MIB. Each managed object in a MIB has a unique identifier. The identifier includes the object's type (such as counter, string, gauge or address), the object's access level (such as read, or read/write), size restrictions and range information.
Medium Independent Interface. Similar to the original AUI function, but designed to support both 10 and 100 Mbps, an MII provides a 40-pin connection to outboard transceivers (also called PHY devices). Used to attach 802.3 interfaces (MACs) to a variety of physical media systems.
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 deliver network services. It is a good model, but strict compliance to the model is seldom accomplished.
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. Contemporary Controls has been assigned a vendor OUI.
A twisted-pair or fiber optic jumper cable used to make a connection between a media segment and a network interface (on a station) or a network port (on a hub), or to directly connect stations and hub ports together.
The bottom layer in the OSI seven-layer reference model. This layer is responsible for physical signaling—including connectors, timing, voltages, and related issues. Data sent over the physical layer are termed symbols.
A cable that is rated as having adequate fire resistance and satisfactorily low smoke-producing characteristics for use in plenums (air handling spaces). Air handling spaces are often located below machine room floors or above suspended ceilings, requiring the use of plenum-rated cable.
A network system composed of point-to-point links. Each point-to-point link connects two and only two devices—one at each end. Devices could be DTEs or DCEs, but no more than two can be connected on one link.
Port Mirroring allows a switch port to monitor packets from any or all of its ports so that traffic can be analyzed.
See a tutorial on Port Mirroring
Prevents a switch port from learning MAC addresses. Thus, frames pass through only if their destinations are listed in the switch address look-up table. Static addresses are not affected. This feature is typically used to limit device access to a network.
Quality of Service
Some switches support QoS (per 802.1p and 802.1Q standards) whereby tagged measures, or messages received on a certain port can be assigned one of eight levels of priority. QoS can be important where time-critical applications can be impaired by data delays.
See a tutorial on Quality of Service (QoS)
Contemporary Controls' proprietary redundant ring technology which provides an alternate path in the event of a single break in the ring.
See a tutorial on RapidRing redundancy
The ability of a switch to limit the throughput of particular ports on the switch. Used to prevent certain ports from consuming all the bandwidth.
See a tutorial on Rate Limiting
A physical layer DCE used to interconnect segments within the same network. An Ethernet repeater can only link Ethernet segments that are all operating in half-duplex mode and at the same speed. Some repeaters offer media conversion as well.
Simple Network Management Protocol. The de facto standard for switch management. A familiarity with MIB objects is necessary to manage a switch with an SNMP management program. SNMP is not necessarily limited to TCP/IP networks.
See a tutorial on Simple Network Management Protocol (SNMP)
A link management protocol providing path redundancy and preventing network loops by defining a tree to span all switches in a network. It forces redundant data paths into a standby (blocked) state. If a path malfunctions, the topology is reconfigured and the link reestablished by activating the standby path.
Straight Tip. This is a type of fiber optic connector used in 10BASE-FL and FOIRL links, but also in 100BASE-TX links. The male end of this connector has an inner sleeve with a slot cut into it, and an outer ring with a bayonet latch. The inner sleeve is aligned with a mating key in the socket and the outer ring is turned to complete the bayonet latch.
A switching hub is another name for a bridge; a DCE that interconnects network segments at the data link layer. Switching hubs are typically located in the center of a star topology, and provide multiple ports for connections to network stations. Frequently this name is shortened to switch.
A combination of the words transmitter and receiver. A transceiver is the set of electronics that sends and receives signals on a media system. Transceivers may be internal or external. Sometimes called a MAU.
Two or more ports grouped together as one logical path to increase bandwidth between a switch and a network node when a single path cannot handle the traffic. Loops are avoided because specific paths are designated. Often a single link is designated for flooding broadcasts and packets of unknown destination. Trunks can provide redundancy to critical devices.
See a tutorial on Trunking redundancy
A multiple-conductor cable whose component wires are paired together, twisted, and enclosed in a single jacket. A typical Category 5 twisted-pair segment is composed of a cable with four twisted pairs contained in a single jacket. Each pair consists of two insulated copper wires that are twisted together.
Virtual Local Area Network. A LAN that maps stations on a basis other than location such as by department, user type or application. Managing traffic, workstations, and bandwidth can be easier with a VLAN and improve network efficiency.
See a tutorial on Virtual Local Area Networks (VLANs)
A computer or device that serves up Web pages. By installing server software into a computer or device and connecting it to a network, it can become a Web server. Every Web server has an IP address and possibly a domain name.