Cisco Cisco IOS Software Release 12.2(25)S

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.

ATM-AAL5—ATM adaptation layer 5. One of four AALs recommended by the ITU-T. AAL5 supports 
connection-oriented variable bit rate (VBR) services and is used predominantly for the transfer of 
classical IP over ATM and LAN emulation (LANE) traffic. AAL5 uses simple and efficient AAL (SEAL) 
and is the least complex of the current AAL recommendations. It offers low bandwidth overhead and 
simpler processing requirements in exchange for reduced bandwidth capacity and error-recovery 
capability.

encapsulation—Wrapping of data in a particular protocol header. For example, Ethernet data is wrapped 
in a specific Ethernet header before network transit. Also, when dissimilar networks are bridged, the 
entire frame from one network is simply placed in the header used by the data link layer protocol of the 
other network.

IETF—Internet Engineering Task Force. A task force (consisting of more than 80 working groups) that 
is developing standards for the Internet and the IP suite of protocols.

interface—The boundary between adjacent layers of the ISO model.

label—A short, fixed-length identifier that is used to determine the forwarding of a packet.

label switching—The forwarding of IP (or other network layer) packets by means of a label-swapping 
algorithm based on network layer routing algorithms. The forwarding of these packets uses the exact 
match algorithm and rewrites the label.

LSR—label switch router. A device that forwards MPLS packets based on the value of a fixed-length 
label encapsulated in each packet.

MIB—Management Information Base. A database of network management information that is used and 
maintained by a network management protocol such as SNMP. The value of a MIB object can be changed 
or retrieved by means of SNMP commands, usually through a network management system. MIB objects 
are organized in a tree structure that includes public (standard) and private (proprietary) branches.

MPLS—Multiprotocol Label Switching. A switching method that forwards IP traffic through use of 
labels. Each label instructs the routers and the switches in the network where to forward packets based 
on preestablished IP routing information.

MPLS interface—An interface on which MPLS traffic is enabled.

MTU—Maximum transmission unit. Maximum packet size, in bytes, that a particular interface can 
handle.

NMS—network management system. A system responsible for managing at least part of a network. An 
NMS is generally a reasonably powerful and well-equipped computer, such as an engineering 
workstation. NMSs communicate with agents to help keep track of network statistics and resources.

OID—Object identifier. Values are defined in specific MIB modules. The Event MIB allows you or an 
NMS to watch over specified objects and to set event triggers based on existence, threshold, and Boolean 
tests. An event occurs when a trigger is fired; this means that a specified test on an object returns a value 
of true. To create a trigger, you or an NMS configures a trigger entry in the mteTriggerTable of the Event 
MIB. This trigger entry specifies the OID of the object to be watched. For each trigger entry type, 
corresponding tables (existence, threshold, and Boolean tables) are populated with the information 
required for carrying out the test. The MIB can be configured so that, when triggers are activated (fired), 
either an SNMP set is performed, a notification is sent out to the interested host, or both.