Cisco Router IOS XR Getting Started Manual page 204

Glossary
L
Layer 2 refers to the data link layer of the commonly referenced multilayered communication model,
Layer 2
Open Systems Interconnection (OSI). The data link layer contains the address inspected by a bridge or
switch. Layer 2 processing is faster than layer 3 processing, because less analysis of the packet is
required.
Layer 3 refers to the network layer of the commonly referenced multilayered communication model,
Layer 3
Open Systems Interconnection (OSI). The network layer is concerned with knowing the address of the
neighboring nodes in the network, selecting routes and quality of service, and recognizing and
forwarding to the transport layer incoming messages for local host domains.
A router is a Layer 3 device, although some newer switches also perform Layer 3 functions. The
Internet Protocol (IP) address is a Layer 3 address.
line card. Line cards in the Cisco CRS-1 system are referred to as modular services cards (MSCs).
LC
label distribution protocol. A standard protocol between MPLS-enabled routers to negotiate the labels
LDP
(addresses) used to forward packets. The Cisco proprietary version of this protocol is the Tag
Distribution Protocol (TDP).
Label Information Base. The table that contains the labels in use on the node.
LIB
Send the outgoing signals back to the receiving side for testing.
loopback
M
Standardized data link layer address that is required for every port or device that connects to a LAN.
MAC address
Other devices in the network use these addresses to locate specific ports in the network and to create
and update routing tables and data structures. MAC addresses are 6 bytes long and are controlled by
the IEEE. Also known as a hardware address, MAC layer address, and physical address.
Pattern of bits used to reject or accept bit patterns in another set of data.
mask
minimum boot image. Software image containing a kernel and minimum set of drivers and components
MBI
to boot a node.
megabits per second. A bit rate expressed in millions of binary bits per second. 1 megabit = 2
Mbps
1,048,576 bits.
Management Information Base. Database of network management information that is used and
MIB
maintained by a network management protocol like Simple Network Management Protocol (SNMP).
The value of an MIB object can be changed or retrieved using SNMP commands, usually through a GUI
network management system. MIB objects are organized in a tree structure that includes public
(standard) and private (proprietary) branches.
Multiprotocol Label Switching. Switching method that forwards IP traffic using a label. This label
MPLS
instructs the routers and switches in the network where to forward the packets based on pre-established
IP routing information
Cisco IOS XR Getting Started Guide
GL-6
20
bits, or
OL-10957-02