NetEss7EdChapter08

RAM buffering

A NIC feature for including additional memory to provide temporary storage for incoming and outgoing data.

PCI Express (PCIe)

A bus standard that uses a high-speed serial communication protocol of one or more lines or lanes. Each lane of PCIe 1.0 can operate at 250 MBps in each direction. See also Peripheral Component Interconnect (PCI).

Peripheral Component Interconnect-Extended (PCI-X)

A bus standard that's backward- compatible with PCI and supports speeds of 66 to 533 MHz with 32-bit or 64-bit bus widths. See also Peripheral Component Interconnect (PCI).

Peripheral Component Interconnect (PCI)

A bus standard used to connect I/O devices to the memory and CPU of a PC motherboard. PCI is implemented in both 32-bit and 64-bit versions at speeds of 33 and 66 MHz, respectively, and is rapidly becoming obsolete. 8

Spanning Tree Protocol (STP)

A communication protocol switches use to ensure that they aren't connected in a way that creates a switching loop. See also switching loop.

broadcast storm

A condition that occurs when a broadcast frame is forwarded endlessly in a switching loop. See also switching loop.

switching loop

A condition that occurs when switches are connected in such a way that frames can be forwarded endlessly from switch to switch in an infinite loop.

Routing Information Protocol (RIP)

A distance-vector protocol that uses hop count as the metric to determine the best path to a destination network.

fault tolerance

A feature available on some high-end NICs. By installing a second NIC in a PC, failure of the primary NIC shifts network traffic to the second NIC instead of cutting off the PC from the network.

onboard co-processors

A feature included on most NICs that enables the card to process incoming and outgoing network data without requiring service from the CPU.

wake-on-LAN (WoL)

A feature on many NICs that allows an administrator to power on a computer remotely by sending a special packet, called a "magic packet," to the NIC's MAC address.

shared system memory

A feature on some NICs in which a NIC's onboard processor selects a region of RAM on the computer and writes to it as though it were buffer space on the adapter.

shared adapter memory

A feature on some NICs in which the NIC's buffers map directly to RAM on the computer. A computer actually writes to buffers on the NIC instead of writing to its own memory.

Preboot Execution Environment (PXE)

A feature on some NICs that allows remotely booting an OS stored on a server through the PC's NIC instead of from local storage.

virtual local area networks (VLANs)

A feature on some switches that allows configuring one or more switch ports into separate broadcast domains.

bus mastering

A feature that allows a network adapter to take control of the computer's bus to initiate and manage data transfers to and from the computer's memory, independent of the CPU.

automatic link aggregation

A feature that enables you to install multiple NICs in one computer and aggregate the bandwidth so that, for example, you can install two 1 Gbps NICs and have a total bandwidth of 2 Gbps to and from that computer.

managed switch

A high-end switch with many advanced features that can be configured.

blocking mode

A mode on a switch port that prevents the switch from forwarding frames out the blocked port, thereby preventing a switching loop. See also switching loop.

autonomous system

A network under the control of a single administrative entity, such as an organization's internetwork or an ISP's network.

Routing Information Protocol version 2 (RIPv2)

A newer version of RIP that supports a more complex IP addressing scheme and uses multicast packets rather than broadcasts to transmit routing table updates. See also Routing Information Protocol (RIP).

metric

A numeric value that tells the router how "far away" the destination network is. It can be composed of values such as the bandwidth of links between the source and destination, the hop count, and the link's reliability.

packet filtering

A process whereby a router blocks a packet from being forwarded based on rules specified by an access control list. See also access control list (ACL).

border router

A router that connects one autonomous system to another—for example, an organization's network to an ISP. See also autonomous system.

exterior gateway protocol (EGP)

A routing protocol category in which the routing protocol is used to exchange routing information between autonomous systems. See also autonomous system.

link-state protocol

A routing protocol that a router uses to share information with other routers by sending the status of all its interface links to all other routers in the internetwork. The status includes link speed, whether the link is up or down, and the link's network number.

path-vector routing protocol

A routing protocol that analyzes the path to each destination network so that it can form a nonlooping routing topology.

distance-vector protocol

A routing protocol that routers use to share information about an internetwork's status by copying their routing table to other routers with which they share a network.

static route

A routing table entry that's entered manually by an administrator.

access control list (ACL)

A set of rules configured on a router's interface for specifying which addresses and protocols can pass through the interface and to which destinations.

routing protocol

A set of rules routers use to exchange information so that all routers have accurate information about an internetwork to populate their routing tables.

trunk port

A switch port configured to carry traffic from all VLANs to another switch or router. See also virtual local area networks (VLANs).

auto-MDIX

A switch port option used to detect the type of device and cable the switch port is connected to; if necessary, the port swaps its transmit and receive pins, which enables you to use a straight-through or crossover cable regardless of the type of device you're connecting to the port.

administrative distance

A value assigned to a routing protocol that indicates its reliability compared with other routing protocols that might be in use on the same router. If a route is derived by using two different routing protocols, the one with the least administrative distance is used.

Border Gateway Protocol (BGP)

An exterior gateway routing protocol used to exchange routing information between two autonomous systems. See also autonomous system and exterior gateway protocol (EGP).

Universal Serial Bus (USB)

An external PC bus interface for connecting I/O devices. Speeds range from 12 Mbps in USB 1.0 to 3.2 Gbps in USB 3.0.

next hop

An interface name or the address of the next router in the path to the destination network.

frame fragment

An invalid frame that's damaged because of a collision or a malfunctioning device.

auto-negotiate mode

Communication between a switch and a device connected to a switch port, in which the switch attempts to set the port's operating mode to the highest performance setting the device supports.

PCMCIA cards

Credit card-sized expansion cards used mainly to add functionality to laptop computers. The main standards are Cardbus and ExpressCard. Cardbus operates at 33 MHz and supports a 32-bit bus; ExpressCard uses PCIe technology to provide data transfer speeds up to 500 MBps.

Rapid Spanning Tree Protocol (RSTP)

Defined in 802.1w, this enhancement to the older, slower Spanning Tree Protocol (STP) provides much faster convergence when the switch topology changes. See also convergence and Spanning Tree Protocol (STP).

hop

Each router a packet must go through to get to the destination network.

neighbor

In an internetwork, routers sharing a common network.

convergence

Refers to how fast the routing tables of all routers in an internetwork are updated with accurate information when a change in the network occurs.

aging time

The amount of time a switch maintains a switching table entry that hasn't been updated.

destination network

The network address of a network to which the router can forward packets.

packet forwarding

The process of a router receiving a packet on one port and forwarding it out another port based on the packet's destination network address and information in the routing table.

flood

The process whereby a switch forwards a frame out all connected ports.

hop count

The total number of routers a packet must travel through to get to its destination network. interior gateway protocol (IGP) A routing protocol category in which the routing protocol is used to exchange routing information within an autonomous system. See also autonomous system.

store-and-forward switching

This switching method requires the switch to read the entire frame into its buffers before forwarding it. It examines the frame check sequence (FCS) field to be sure the frame contains no errors before it's forwarded.

fragment-free switching

With this switching method, the switch reads enough of the frame to guarantee that it's at least the minimum size for the network type, reducing the possibility that the switch will forward a frame fragment.

cut-through switching

With this switching method, the switch reads only enough of the incoming frame to determine its source and destination addresses. After the forwarding location is determined, the frame is switched internally from the incoming port to the outgoing port, and the switch is free to handle additional frames.