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M

MAC — Media access control. In the OSI seven-layer networking model defined by the IEEE, MAC is the lower sublayer of the data link layer. The MAC sublayer governs protocol access to the physical network medium. By using the MAC addresses that are assigned to all ports on a router, multiple devices on the same physical link can uniquely identify one another at the data link layer. See also MAC address.

MAC address — Serial number permanently stored in a device adapter to uniquely identify the device. See also MAC.

maintenance association — The combined set of nodes (MEPs and MIPs) within a maintenance domain. See also LTR.

maintenance association end point — See MEP.

maintenance association ID — The ID associated with the maintenance association.

maintenance association intermediate point — See MIP.

maintenance domain — The part of the network where connectivity fault detection is performed.

maintenance point — See MP.

MAM — Maximum allocation bandwidth constraints model. In Differentiated-Services-aware traffic engineering, a constraint model that divides the available bandwidth among the different classes. Sharing of bandwidth among the class types is not allowed.

management daemon — See mgd.

management Ethernet interface — Permanent interface that provides an out-of-band method, such as ssh and telnet, to connect to the routing platform. SNMP can use the management interface to gather statistics from the routing platform. Called fxp0 on some routing platforms. See also permanent interface.

Management Information Base — See MIB.

Management Module, JCS — See JCS Management Module.

mapping agent — Router used in an auto-RP multicast network to select the rendezvous point for all multicast group addresses. The rendezvous point is then advertised to all other routers in the domain.

martian address — Network address about which all information is ignored.

martian route — Network routes about which all information is ignored. The JUNOS software does not allow martian routes in the inet.0 routing table.

MAS — Mobile network access subsystem. A GSN application subsystem that contains the access server.

mask — See subnet mask.

master — Router in control of the OSPF database exchange during an adjacency formation.

match — Logical concept used in a routing policy or firewall filter. A match denotes the criteria used to find a route or IP packet before an action is performed.

match type — JUNOS software syntax used in a route filter to better describe the routes that should match the policy term.

maximum allocation bandwidth constraints model — See MAM.

maximum received reconstructed unit — See MRRU.

maximum transmission unit — See MTU.

MBGP — Multiprotocol Border Gateway Protocol. An extension to BGP that allows you to connect multicast topologies within and between BGP ASs.

MBone — Multicast Backbone. An interconnected set of subnetworks and routers that support the delivery of IP multicast traffic. The MBone is a virtual network that is layered on top of sections of the physical Internet.

MCS — Miscellaneous Control Subsystem. On the M40e and M160 routers, provides control and monitoring functions for router components and SONET clocking for the router.

MD5 — Message Digest 5. A one-way hashing algorithm that produces a 128-bit hash used for generating message authentication signatures. MD5 is used in AH and ESP. See also hashing, SHA-1.

MDRR — Modified deficit round robin. A method for selecting queues to be serviced. See queue.

MDT — Multicast distribution tree. The path between the sender (host) and the multicast group (receiver or listener).

mean time between failures — See MTBF.

MED — Multiple exit discriminator. An optional BGP path attribute consisting of a metric value that is used to determine the exit point to a destination when all other factors determining the exit point are equal.

MEP — The start and end point within a maintenance domain. See also LTM.

mesh — Network topology in which devices are organized in a manageable, segmented manner with many, often redundant, interconnections between network nodes.

message aggregation — Extension to the Resource Reservation Protocol (RSVP) specification that allows neighboring routers to bundle up to 30 RSVP messages into a single protocol packet.

Message Digest 5 — See MD5.

mgd — Management daemon. JUNOS software process responsible for managing all user access to the router.

MIB — Management Information Base. Definition of an object that can be managed by SNMP.

midplane — Physically separates front and rear cavities inside the chassis, distributes power from the power supplies, and transfers packets and signals between router components, which plug into it.

MIP — An intermediate node within the maintenance domain..See also LTM.

Miscellaneous Control Subsystem — See MCS.

MLD — Multicast listener discovery. A protocol that manages the membership of hosts and routers in multicast groups. IPv6 multicast routers use MLD to learn, for each of their attached physical networks, which groups have interested listeners.

MLFR — Multilink Frame Relay. Logically ties together individual circuits, creating a bundle. The logical equivalent of MLPPP, MLFR is used for Frame Relay traffic instead of PPP traffic. FRF.15 and FRF.16 are two implementations of MLFR.

MLPPP — Multilink Point-to-Point Protocol. Enables you to bundle multiple PPP links into a single logical link between two network devices to provide an aggregate amount of bandwidth. The technique is often called bonding or link aggregation. Defined in RFC 1990. See also PPP.

MM — The JCS management module.

MMF — Multimode fiber. Optical fiber supporting the propagation of multiple frequencies of light. MMF is used for relatively short distances because the modes tend to disperse over longer lengths (called modal dispersion). For longer distances, single–mode fiber (sometimes called monomode) is used. See also single-mode fiber.

mobile network access subsystem — See MAS.

mobile point-to-point control subsystem — See MPS.

mobile station — Mobile device, such as a cellular phone or a mobile personal digital assistant (PDA).

Mobile Station Integrated Services Digital Network Number — See MSISDN.

Mobile Switching Center — See MSC.

mobile transport subsystem — See MTS.

MPLS — Multiprotocol Label Switching. Mechanism for engineering network traffic patterns that functions by assigning to network packets short labels that describe how to forward them through the network. Also called label switching. See also traffic engineering.

MPLS EXP classifier — Class–of–service (CoS) behavior classifier for classifying packets based on the MPLS experimental bit. See also EXP bits.

MPS — Mobile point-to-point control subsystem. A GSN application subsystem that controls all functionality associated with a particular connection.

MRRU — Maximum received reconstructed unit. Similar to the MTU, but is specific to link services interfaces. See also MTU.

MSA — Multisource Agreement. The definition of a fiber-optic transceiver module that conforms to the 10-Gigabit Ethernet standard. See also XENPAK module.

MSC — Mobile Switching Center. Provides origination and termination functions to calls from a mobile station user.

MSDP — Multicast Source Discovery Protocol. A protocol used to connect multicast routing domains to allow the domains to discover multicast sources from other domains. It typically runs on the same router as the PIM sparse mode rendezvous point (RP).

MSISDN — Mobile Station Integrated Services Digital Network Number. A number that callers use to reach a mobile services subscriber.

MST — See MSTP.

MSTI — Multiple Spanning Tree Instance. One of a number of spanning trees calculated by MSTP within an MST region. The MSTI provides a simple and fully connected active topology for frames classified as belonging to a VLAN that is mapped to the MSTI by the MST configuration table used by the MST bridges of that MST region. See also CIST.

MSTP — Multiple Spanning Tree Protocol. A spanning-tree protocol used to prevent loops in bridge configurations. Unlike other types of STPs, MSTP can block ports selectively by VLAN. See also RSTP.

MTBF — Mean time between failures. Measure of hardware component reliability.

MTS — Mobile transport subsystem. A GSN application subsystem that implements all the protocols used by the GSN.

MTU — Maximum transmission unit. Limit on the data size for a network.

multicast — Operation of sending network traffic from one network node to multiple network nodes.

multicast distribution tree — See MDT.

multicast listener discovery — See MLD.

multicast-scope number — Number used for configuring the multicast scope. Configuring a scope number constrains the scope of a multicast session. The number value can be any hexadecimal number from 0 through F. The multicast-scope value is a number from 0 through 15, or a specified keyword with an associated prefix range. For example, link-local (value=2), corresponding prefix 224.0.0.0/24.

Multicast Source Discovery Protocol — See MSDP.

multiclass LSP — In Differentiated-Services-aware traffic engineering, a multiclass label-switched path (LSP) functions like a standard LSP, but also allows you to reserve bandwidth for multiple class types. The experimental (EXP) bits of the MPLS header are used to distinguish between class types.

multiclass MLPPP — Enables multiple classes of service while using MLPPP. Defined in RFC 2686, The Multi-Class Extension to Multi-Link PPP.

multifield classifier — Method for classifying traffic flows. Unlike a behavior aggregate (BA) classifier, a multifield classifier examines multiple fields in the packet to apply class–of–service (CoS) settings. Examples of fields that a multifield classifier examines include the source and destination address of the packet, as well as the source and destination port numbers of the packet. See also BA classifier, classification.

multihoming — Network topology that uses multiple connections between customer and provider devices to provide redundancy.

Multilink Frame Relay — See MLFR.

multimode fiber — See MMF.

multiple exit discriminator — See MED.

multiple spanning tree instance — See MSTI.

Multiple Spanning Tree Protocol — See MSTP.

multiprotocol BGP — See MBGP.

Multiprotocol Label Switching — See MPLS.

Multisource Agreement — See MSA.

MVS — Mobile visitor register subsystem.

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