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Terms for computer junkies
PUMP up your computer-related vocabulary! Load your brains with these frequenty used i-terms.
DLC: short for Data Link Control, the second lowest layer in the OSI Reference Model. Every network interface card (NIC) has a DLC address or DLC identifier (DLCI) that uniquely identifies the node on the network. Some network protocols, such as Ethernet and Token-Ring use the DLC addresses exclusively. Other protocols, such as TCP/IP, use a logical address at the Network Layer to identify nodes. Ultimately, however, all network addresses must be translated to DLC addresses. In TCP/IP networks, this translation is performed with the Address Resolution Protocol (ARP).
For networks that conform to the IEEE 802 standards (e.g., Ethernet ), the DLC address is usually called the Media Access Control (MAC) address.
MAC layer: the Media Access Control Layer is one of two sublayers that make up the Data Link Layer of the OSI model. The MAC layer is responsible for moving data packets to and from one Network Interface Card (NIC) to another across a shared channel.
The MAC sublayer uses MAC protocols to ensure that signals sent from different stations across the same channel don’t collide.
CSMA/CD: short for Carrier Sense Multiple Access/Collision Detection, a set of rules determining how network devices respond when two devices attempt to use a data channel simultaneously (called a collision). Standard Ethernet networks use CSMA/CD. This standard enables devices to detect a collision. After detecting a collision, a device waits a random delay time and then attempts to re-transmit the message. If the device detects a collision again, it waits twice as long to try to re-transmit the message. This is known as exponential back off.
Hub: a common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.
A passive hub serves simply as a conduit for the data, enabling it to go from one device (or segment) to another. So-called intelligent hubs include additional features that enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub. Intelligent hubs are also called manageable hubs.
A third type of hub, called a switching hub, actually reads the destination address of each packet and then forwards the packet to the correct port.
Switching hub: Short for port-switching hub, a special type of hub that forwards packets to the appropriate port based on the packet’s address. Conventional hubs simply rebroadcast every packet to every port. Since switching hubs forward each packet only to the required port, they provide much better performance. Most switching hubs also support load balancing, so that ports are dynamically reassigned to different LAN segments based on traffic patterns.
Some newer switching hubs support both traditional Ethernet (10Mbps) and Fast Ethernet (100Mbps) ports. This enables the administrator to establish a dedicated, Fast Ethernet channel for high-traffic devices such as servers.
Segment: In networks, a section of a network that is bounded by bridges, routers or switches. Dividing an Ethernet into multiple segments is one of the most common ways of increasing available bandwidth on the LAN. If segmented correctly, most network traffic will remain within a single segment, enjoying the full 10Mbps bandwidth.
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