802.1d --IEEE standard for MAC bridges.
802.1p --IEEE standard for queuing and multicast support.
802.1q--IEEE standard for VLAN frame tagging.
802.1x--IEEE standard for port-based network access control.
ACE --access control entry. Entry in an access control list.
ACL--access control list. Used for security or as a general means to classify traffic.
AgPort --aggregate port (another name for EtherChannel).
ATM--Asynchronous Transfer Mode. The international standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
authentication server --Entity that validates the credentials of a host trying to obtain access to the network.
authenticator --Entity that enforces authentication rules for hosts connecting to a LAN via one of its ports.
authorization state --The state of a controlled port. It can be authorized (access allowed) or unauthorized (access denied).
AVVID--Architecture for voice, video, and integrated data.
BRI--Basic Rate Interface. ISDN interface comprising two B channels and one D channel for circuit-switched communication of voice, video, and data.
CAC--connection admission control. Set of actions taken by each ATM switch during connection setup to determine whether a connection's requested QoS will violate the QoS guarantees for established connections. CAC is also used when routing a connection request through an ATM network.
candidate --Switch that is not part of a cluster, but is eligible to join a cluster because it meets the qualification criteria of the cluster.
CBWFQ--class-based weighted fair queuing. Extends the standard WFQ functionality to provide support for user-defined traffic classes.
CCN--Cisco Communications Network (Cisco IP phones and IP PBX).
classification --Process of sorting incoming packets by examining fields of interest in the packet header. Fields can be addresses, ports, DSCP value, and so on.
cluster --Group of switches that are managed as a single device. A cluster comprises one commander and multiple members.
cluster commander --Switch that provides the primary management interface to a cluster.
cluster member --Member switch that is managed through the cluster commander.
CoS --class of service. An indication of how an upper-layer protocol requires a lower-layer protocol to treat its messages. In SNA subarea routing, CoS definitions are used by subarea nodes to determine the optimal route to establish a session. A CoS definition comprises a virtual route number and a transmission priority field. Also called ToS.
DSCP --differentiated services code point. In QoS, a modification of the type of service byte. Six bits of this byte are being reallocated for use as the DSCP field, where each DSCP specifies a particular per-hop behavior that is applied to a packet.
DSL--digital subscriber line. Public network technology that delivers high bandwidth over conventional copper wiring at limited distances. There are four types of DSL: ADSL, HDSL, SDSL, and VDSL. All are provisioned via modem pairs, with one modem at a central office and the other at the customer site. Because most DSL technologies do not use the whole bandwidth of the twisted pair, there is room remaining for a voice channel.
EAP--Extensible Authentication Protocol. A mechanism (originally designed for PPP in RFC 2284) that provides authentication of hosts requesting access to a network.
EAPOL --EAP over LAN.
Frame Relay --The capability to carry normal telephony-style voice over an IP-based network with POTS-like functionality, reliability, and voice quality. VoIP lets a router carry voice traffic (such as telephone calls and faxes) over an IP network. In VoIP, the DSP segments the voice signal into frames, which then are coupled in groups of two and stored in voice packets. These voice packets are transported using IP in compliance with ITU-T specification H.323.
FXO--Foreign Exchange Office. An FXO interface connects to the Public Switched Telephone Network (PSTN) central office and is the interface offered on a standard telephone. Cisco's FX interface is an RJ-11 connector that allows an analog connection at the PSTN's central office or to a station interface on a PBX.
FXS--Foreign Exchange Station. An FXS interface connects directly to a standard telephone and supplies ring, voltage, and dial tone. Cisco's FXS interface is an RJ-11 connector that allows connections to basic telephone service equipment, keysets, and PBXs.
HSRP --Hot Standby Router Protocol. Provides high network availability and transparent network topology changes. HSRP creates a hot standby router group with a lead router that services all packets sent to the hot standby address. The lead router is monitored by other routers in the group, and if it fails, one of these standby routers inherits the lead position and the hot standby group address.
IGMP --Internet Group Management Protocol. Used by IP hosts to report their multicast group memberships to an adjacent multicast router.
ISL --InterSwitch Link, which is used to carry traffic for multiple VLANs. A method of encapsulating tagged LAN frames and transporting them over a full-duplex, point-to-point Ethernet link. The encapsulated frames can be Token Ring or Fast Ethernet and are carried unchanged from transmitter to receiver.
MIB --Management Information Base. Database of network management information that is used and maintained by a network management protocol, such as SNMP or Common Management Information Protocol (CMIP). The value of a MIB object can be changed or retrieved using SNMP or CMIP commands, usually through a graphical user interface (GUI) network management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches.
policing --Process of ensuring whether a stream of classified incoming packets conforms to a particular traffic profile. An action (drop or remark) is taken based on the rate of arrival of packets.
PRI--primary rate interface. ISDN interface to primary rate access. Primary rate access consists of one 64-kbps D channel and 23 (T1) or 30 (E1) B channels for voice or data. Compare with BRI.
PSTN--public switched telephone network. General term referring to the variety of telephone networks and services in place worldwide. Also called POTS.
PVC--permanent virtual circuit. Virtual circuit that is permanently established. PVCs save bandwidth associated with circuit establishment and tear down in situations where certain virtual circuits must exist all the time. In ATM terminology, called a permanent virtual connection.
PVST --Per-VLAN spanning tree. Support for dot1q trunks to map multiple spanning trees to a single spanning tree.
QoS--quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability.
RADIUS --Remote Access Dial-In User Service. A service used to authenticate and authorize clients.
RMON --remote monitoring. MIB agent specification described in RFC 1271 that defines functions for the remote monitoring of networked devices. The RMON specification provides numerous monitoring, problem detection, and reporting capabilities.
RSVP--Resource Reservation Protocol. Protocol that supports the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature (bandwidth, jitter, maximum burst, and so on) of the packet streams they want to receive. RSVP depends on IPv6. Also known as Resource Reservation Setup Protocol.
SIP--Session Initiation Protocol. Protocol developed by the IETF MMUSIC Working Group as an alternative to H.323. SIP features are compliant with IETF RFC 2543, which was published in March 1999. SIP equips platforms to signal the setup of voice and multimedia calls over IP networks.
SNMP --Simple Network Management Protocol. Network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices and to manage configurations, statistics collection, performance, and security.
stacking --Connecting two switches so they behave as one entity for management purposes. Regarding an EtherSwitch Network Module, stacking means connecting two EtherSwitch Network Modules inside a chassis so that they behave as one switch.
STP --Spanning Tree Protocol. Bridge protocol that uses the spanning-tree algorithm, which enables a learning bridge to dynamically work around loops in a network topology by creating a spanning tree. Bridges exchange Bridge Protocol Data Unit (BPDU) messages with other bridges to detect loops and then remove the loops by shutting down selected bridge interfaces. Refers to both the IEEE 802.1 Spanning-Tree Protocol standard and the earlier Digital Equipment Corporation Spanning-Tree Protocol upon which it is based. The IEEE version supports bridge domains and allows the bridge to construct a loop-free topology across an extended LAN. The IEEE version generally is preferred over the Digital version.
supplicant --Entity requesting access to the network via the authenticator.
SVI --Switch Virtual Interface. Represents a VLAN of switch ports as one interface to the routing or bridging function in a system.
VBR--variable bit rate. QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a real time (RT) class and non-real time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections in which there is no fixed timing relationship between samples but that still need a guaranteed QoS.
VLAN --virtual LAN. Group of devices on one or more LANs that are configured (using management software) so that they can communicate as if they were attached to the same wire, when in fact they are on separate LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible.
VoIP--Voice over IP. Ability to carry normal telephony-style voice over an IP-based internet with POTS-like functionality, reliability, and voice quality. VoIP enables a router to carry voice traffic (such as telephone calls and faxes) over an IP network. In VoIP, the digital signal processor (DSP) segments the voice signal into frames, which then are coupled in groups of two and stored in voice packets. These voice packets are transported using IP in compliance with ITU-T specification H.323.
VoIPoFR--Voice-over-IP over Frame-Relay.
VPN--virtual private network. Enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one network to another. A VPN uses "tunneling" to encrypt all information at the IP level.
VQP --VLAN Query Protocol.
VTP --VLAN Trunking Protocol.
WAN--wide area network. A communications network that covers a wide geographic area such as state or country. A LAN (local-area network) is within a building or complex, and a MAN (metropolitan-area network) generally covers a city or suburb.
WFQ--weighted fair queuing. In QoS, a flow-based queuing algorithm that schedules low-volume traffic first while letting high-volume traffic share the remaining bandwidth. This is handled by assigning a weight to each flow, where lower weights are the first to be serviced.
WRR --Weighted Round-Robin. Type of round-robin scheduling that prevents low-priority queues from being completely neglected during periods of high-priority traffic. The WRR scheduler transmits some packets from each queue in turn. The number of packets it transmits corresponds to the relative importance of the queue.