IN133 - Chapter 06

PCIe (PCI Component Interconnect Express)

A 32-bit bus capable of transferring data at up to 1 Gbps per data path, or lane, in full-duplex transmission.

BID (Bridge ID)

A combination of a 2-byte priority field and a bridge's MAC address, used in STP (Spanning Tree Protocol) to select a root bridge.

ethtool

A popular tool for viewing and modifying network interface properties on Linux computers.

bus

The type of circuit used by a computer's motherboard to transmit data to components.

routing table

A database stored in a router's memory that maintains information about the location of hosts and best paths for forwarding packets to them.

interior router

A router that directs data between nodes on an autonomous LAN.

exterior router

A router that directs data between nodes outside a given autonomous LAN, for example, routers used on the Internet's backbone.

runt

An erroneously shortened packet.

cost

In the context of routing metrics, the value assigned to a particular route as judged by the network administrator. The more desirable the path, the lower its cost.

distance-vector

The simplest type of routing protocols, these determine the best route for data based on the distance to a destinations.

on-board NIC

A NIC that is integrated into a computer's motherboard, rather than connected via an expansion slot or peripheral bus.

expansion board

A circuit board used to connect a device to a computer's motherboard.

filtering database

A collection of data created and used by a bridge that correlates the MAC addresses of connected workstations with their locations.

gateway

A combination of networking hardware and software that connects two dissimilar kinds of networks. These perform connectivity, session management, and data translation, so they must operate at multiple layers of the OSI model.

switch

A connectivity device that logically subdivides a network into smaller, individual collision domains. It can interpret MAC address information to determine whether to discard or forward packets it receives.

bridge

A connectivity device that operates at the Data Link layer (Layer 2) of the OSI model and reads heaeder information to forward packets according to their MAC addresses. These use a filtering database to determine which packets to discard and which to forward. They contain one input and one output port and separate network segments.

hub

A connectivity device that retransmits incoming data signals to its multiple ports.

loopback plug

A connector used for troubleshooting that plugs into a port (for example, a serial, parallel, or RJ-45 port) and crosses over the transmit line to the receive line, allowing outgoing signals to be redirected back into the computer for testing.

firewall

A device that selectively filters or blocks traffic between networks.

BGP (border Gateway Protocol)

A distance-vector routing protocol capable of considering many factors in its routing metrics. Used on Internet backbones

IS-IS (Intermediate System to Intermediate System)

A link-state routing protocol that uses a best-path algorithm similar to OSPF's. These were originally codified by ISO, which referred to routers as "intermediate systems", thus the protocol's name. These are designed for use on interior routers only.

dynamic routing

A method of routing that automatically calculates the best path between two nodes and accumulates this information in a routing table.

store-and-forward mode

A method of switching in which a switch reads the entire data frame into its memory and checks it for accuracy before transmitting it.

router

A multiport device that operates at Layer 3 of hte OSI model and uses logical addressing information to direct data between networks or segments. These can connect dissimilar LANs and WANs running at different ransmission speeds and using a variety of Network layer protocols.

VLAN (Virtual local area network)

A network within a network that is logically defined by grouping its devices' switch ports in the same broadcast domain. A VLAN can consist of any type of network node in any geographic location and can incorporate nodes connected to different switches.

uplink port

A port on a connectivity device, such as a hub or switch, used to connect it to another connectivity device.

expansion slot

A receptacle on a computer's motherboard that contains multiple electrical contacts into which an expansion board can be inserted.

border router

A router that connects an autonomous LAN with an exterior network -- for example, the router that connects a business to its ISP.

EIGRP (Enhanced Interior Gateway Routing Protocol)

A routing protocol developed in the mid-1980s by Cisco Systems that has a fast convergence time and a low network overhead, but is easier to configure and less CPU-intensive than OSPF. Also supports multiple protocols and limits unnecessary network traffic between routers.

EGP (exterior Gateway Protocol)

A routing protocol that can span multiple, autonomous networks.

OSPF (Open Shortest Path First)

A routing protocol that makes up for some of the limitations of RIP and can coexist with RIP on a network.

IGP (Interior Gateway Protocol)

A routing protocol, such as RIP, that can only route data within an autonomous (internal) network.

SFP (small form-factor pluggable) transceiver

A standard hot-swappable network interface used to link a connectivity device's backplane with fiber-optic or copper cabling. SFPs are known as a mini-GBICs, because they perform a similar function as GBICs, but have a smaller profile. Current SFP standards enable them to send and receive data at up to 10Gbps.

GBIC (Gigabit interface converter)

A standard type of modular interface deigned in the 1990s for Gigabit Ethernet connections. These may contain RJ-45 or fiber-optic cable ports. These are inserted into a socket on a connectivity device's backplane.

Layer 3 switch

A switch capable of interpreting data at Layer 3 (network layer) of the OSI model.

Layer 4 switch

A switch capable of interpreting data at Layer 4 (Transport layer) of the OSI model.

application switch

A switch that provides functions between Layer 4 and Layer 7 of the OSI model.

content switch

A switch that provides functions between Layer 4 and Layer 7 of the OSI model.

cut-through mode

A switching mode in which a switch reads a frame's header and decides where to forward the data before it receives the entire packet. Faster, but less accurate than other switching methods, store-and-forward.

STP (Spanning Tree Protocol)

A switching protocol defined in IEEE 802.1D. This protocol operates in the Data Link layer to prevent traffic loops by calculating paths that avoid potential loops and by artificially blocking links that would complete loop.

backplane

A synonym for motherboard, often used in the context of switches and routers.

static routing

A technique in which a network administrator programs a router to use specific paths between nodes. Because it does not account for occasional network congestion, failed connections, or device moves, static routing is not optimal.

link-state

A type of routing protocol that enables routers across a network to share information, after which each router can independently map the network and determine the best path between itself and a packet's destination node.

RIPv2 (Routing Information Protocol version 2)

An updated version of the original RIP routing protocol which makes up for some of its predecessor's overhead and security flaws. However, RIPv2's packet forwarding is still limited to a maximum 15 hops.

RSTP (Rapid Spanning Tree Protocol)

As described in IEEE's 802.1w standard, a newer version of the Spanning Tree Protocol that can detect and correct for network changes much more quickly.

VTP (VLAN trunking protocol)

Cisco's protocol for exchanging VLAN information over trunks. This protocol allows one switch on a network to centrally manage all VLANs.

802.1w

The IEEE standard that describes RSTP (Rapid Spanning Tree Protocol), which evolved from STP (Spanning Tree Protocol)

802.1D

The IEEE standard that describes bridging and STP (Spanning Tree Protocol)

802.1q

The IEEE standard that specifies how VLAN and trunking information appear in frames and how switches and bridges interpret that information.

trunking

The aggregation of multiple logical connections in one physical connection between connectivity devices.

hot-swappable

The feature of a component that allows it to be installed or removed without disrupting operations.

trunk port

The interface on a switch capable of managing traffic from multiple VLANs.

access port

The interface on a switch used for an end node. Devices connected to these are unaware of VLAN information.

routing protocols

The means by which routers communicate with each other about network status. Routing protocols determine the best path for data to take between nodes.

routing metric

The method used by routing protocols to determine the best path for data to follow over a network. Routing metrics may be calculated using any of several variables, including number of hops, bandwidth, delay, MTU, cost, and load.

best path

The most efficient route from one node on a network to another.

RIP (Routing Information Protocol)

The oldest routing protocol that is still widely used, It does not work in very large network environments in which data may have to travel through more than 15 routers to reach their destination (for example, on the Internet). And, compared to other routing protocols, it is slower and less secure.

root bridge

The single bridge on a network selected by the Spanning Tree Protocol to prove the basis for all subsequent path calculations.

device driver

The software that enables an attached device to communicate with the computer's operating system.

convergence time

The time it takes for a router to recognize a best path in the event of a change or network outage.