K-M

kernel

The core of the operating system which implements system calls and provides access to memory, disk, and devices.

kernel mode

Used to indicate execution of a function in a supervisory mode, where it has access to all kernel functions and devices.

LAN

Local Area Network. The most popular one is the Ethernet LAN specified via IEEE 802.3.

Layer 2

Used to indicate the Data Link Layer, and, in the case of LANs, a MAC address based function, which deals only with flat networks without routing.

Layer 2 switch

A MAC bridge over which the forwarding between ports A and B can proceed independent of the forwarding between ports C and D. Forwarding is typically done in hardware to enable this.

Layer 3 switch

An IP router which typically uses hardware-based forwarding.

line card

A component of a multi-board system which provides its physical ports. The ports are housed on media modules which plug in to line cards or on the line cards themselves.

link

A physical connection between two nodes in a network.

link handler

A component of the OSE real- time operating system used for distributed messaging.

link state protocol

A type of routing protocol which floods status updates of connected links throughout the network for each router to build a database of the complete topology. The routers can then apply the SPF algorithm to determine the shortest path to various destinations. Examples are OSPF and IS–IS. Contrast with a distance vector protocol like RIP.

logical interface

A term used for the abstraction of an interface. A logical interface can have a one-to-one mapping with a physical port (e.g., a serial port) or correspond to one of several interfaces on a physical port, e.g., a set of PVCs on a Frame Relay serial port.

longest prefix match (LPM)

A table lookup scheme used in IP routing in which the prefix match covers the most bits.

low-level design

Same as detailed design.

low-water mark

An indicator that the number of entries in a queue/memory or buffer pool has fallen below a predetermined level.

MAC

Medium Access Control. The data link layer sublayer which is responsible for access to a shared medium. Typically used to specify the access mechanism of LANs like Ethernet.

MAC

Media Access Control. A reference to the Layer 2 protocols used to access a network.

MAC address

Used as a synonym for Ethernet address.

management plane

The third part of the classical planar networking architectural model.

manager

An entity responsible for the control and configuration of various devices in the network. It can be a remote entity like an SNMP or CMIP manager or a local one like a CLI user. The manager sends requests and obtains responses from the communications device.

market requirements document (MRD)

A document generated by Marketing to provide specifications/market requirements for a product. This is the first step in the product development cycle.

master agent

Defined in the AgentX architecture, a master agent provides the management functionality for a system. It is typically on a control card and interfaces with the subagents on the line cards for management operations. The master agent is the only one which talks directly to the manager. The subagents communicate only with the master agent—the protocol used on this interface is AgentX.

memory management

A set of facilities usually provided by the operating system which allows applications to allocate, release and manipulate memory blocks for their functioning.

memory protection

Usually implemented on processors which have a memory management unit (MMU), this ensures that two areas of memory are protected via the MMU. So, if code in one area attempts to access the other, a memory violation exception will be raised by the MMU.

messaging interface

A scheme in which entities desiring to communicate with each other use messages. The messages are filled in by the source entity and passed on to the destination entity.

MIB

Management Information Base. Defines the network-related variables that can be read or written on a node.

MIB-II

The Management Information Base specified in RFC 1213. This includes the configuration/control of interfaces, IP and TCP protocols, SNMP, and forwarding and address resolution tables. This is the standard which most IP routers and end nodes implement.

monolithic control plane

An implementation in which the control plane functions like routing, and signaling protocols are fully implemented on the control card. There are no control plane functions on the line card, unlike a Split Control Plane implementation.

MOSPF

Multicast OSPF. An extension of OSPF routing protocol to handle multicast routing.

Motorola PowerPC

A popular RISC processor from Motorola used in several communications equipment designs.

MPLS

Multi-Protocol Label Switching. A connection oriented technology used to forward traffic based on labels.

MTU

Maximum Transmission Unit. A value indicating the maximum size of a packet/frame that can be sent on a specific interface.

multi-service switch

A switch which forwards various types of traffic between interfaces. For example, the same device can implement switching of ATM cells, Frame Relay packets, and Ethernet frames. It may also switch TDM frames.

multicast

A method of transmitting packets to a subset of nodes on a network.

multiplexer

A device that combines distinct channels or streams into a single stream.

mutual exclusion

An agreed-upon way of accessing a shared resource when multiple entities are involved. The entities agree that only one of them can access the resource at a given time.