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In CFM, a Maintenance Association (MA) defines a VLAN and associated ports on a device under an MD level. In this MA, a port can be a MEP (Maintenance End Point) port or a MIP (Maintenance Intermediate Point) port.


MAC (Media Access Control)  

On a local area network (LAN) or other network, the MAC address is a computer's unique hardware number. (On an Ethernet LAN, it's the same as your Ethernet address). The MAC layer frames data for transmission over the network, then passes the frame to the physical layer interface where it is transmitted as a stream of bits.


MAC Count Filter

MAC count filtering limits the number of MAC addresses (see MAC) that may be dynamically learned or statically configured on a port.


MAC Filtering

Media Access Control filtering filters incoming frames based on MAC (Media Access Control) address(es) that you specify.


MAC Force Forwarding

MAC force forwarding forces subscriber(s) to communicate with uplink device(s) through an IPv4 gateway. The gateway then routes or forwards subscriber traffic so the subscribers do not know the MAC addresses of uplink devices on the network.


MAC Freeze

When you enable MAC freeze on a port, all MAC addresses that have been dynamically learned on a port are considered as "static" MAC address entries and have exclusive access to that port from that time on.


Mac OS X

The computer operating system developed by Apple, and is used by all Macintosh computers.


Main Mode

Main mode is an IPSec phase 1 negotiation mode (see Negotiation Mode). Main mode ensures the highest level of security when the communicating parties are negotiating authentication (phase 1). See also Aggressive Mode.


Management Port

A management port is a dedicated port on a device for management purposes only. You cannot access the network through a management port.


Management VID

Management VLAN ID is the VLAN ID of the CPU and is used for management only. To access the switch make sure the port that you are connected to is a member of Management VLAN.


Manager (SNMP)

In the Simple Network Management Protocol (SNMP), a manager is software capable of querying SNMP agents and displaying the returned data.


Many One-to-One NAT Mapping

Many 1:1 NAT mapping maps each local IP address to a unique global IP address. One many 1:1 NAT rule works like multiple 1:1 NAT rules.


Many-to-One NAT Mapping

Many-to-one NAT mapping maps multiple local IP addresses to one global IP address. This is equivalent to Single User Account (SUA), also known as PAT, port address translation.


Many-to-Many Overload NAT Mapping

Many-to-many overload NAT mapping maps multiple local IP addresses to shared global IP addresses.


Max Age

In RSTP (or STP), this is the maximum time (in seconds) a device waits without receiving a configuration message before attempting to reconfigure.


Max. Frame Burst

Maximum Frame Burst sets the maximum time, in microseconds, that transmits IEEE 802.11g wireless traffic only. This helps to eliminate collisions in mixed-mode networks (networks with both IEEE 802.11g and IEEE 802.11b traffic) and enhance the performance of both pure IEEE 802.11g and mixed IEEE 802.11b/g networks.


Maximum Transmission Uni

The Maximum Transmission Unit (MTU) defines the size of the largest packet allowed on an interface or connection.



MBM (Media Bandwidth Management) allows you to allocate specific amounts of bandwidth capacity (bandwidth budgets) to outgoing traffic based on an application and/or subnet.



In ATM, the Maximum Burst Size is the maximum number of cells that can be sent at the PCR. After MBS is reached, cell rates fall below SCR until cell rate averages to the SCR again. At this time, more cells (up to the MBS) can be sent at the PCR again (see PCR).


Mbps (Megabits per Second)

Megabits per second = one million data bits, zeroes and ones, per second. This is a measure of how quickly data is transmitted over a communication link.



Minimum Cell Rate is the minimum rate at which the sender can send cells and applies with the ABR ATM traffic class (see ABR).



MDI (Medium Dependent Interface)/MDIX (MDI crossover) is a type of Ethernet port. MDI ports connect to MDIX ports using straight-through Ethernet cables; both MDI-to-MDI and MDIX-to-MDIX connections use crossover Ethernet cables.


Measured Bandwidth

In load balancing, measured bandwidth is the bandwidth an interface is currently using.


Media Card

A VoIP media card terminates RTP packets and converts the payload into analog for the subscriber’s phone. The media card packetizes audio signals from the subscriber line into RTP packets and sends line events.


Media Extender

A media extender streams digital media files (video, music, photos) stored from the computer to a home entertainment device such as a TV, stereo, or home theater system.


Media Gateway

In an H.248 VoIP network, media gateways (MGs) encode and decode voice data, transmitting it from one network to another (for example, from the PSTN to an IP network, and vice versa).


Media Gateway Controller

In an H.248 VoIP network, media gateway controllers (MGC) are intelligent devices that manage the media gateways. They set up, manage, and tear down calls by providing instructions to the media gateways.


Media Hub

A device that receives digital media content (especially digital music collections) streamed from a computer to a stereo or home theater system.


Media Optimized Networking

Technology that prioritizes network traffic so that time-sensitive applications like HD video streams smoothly. Also known as Entertainment Optimized Networking.


Media Server

A media server is a computer or hardware device that stores and shares digital media files such as video, music, and photos.


A megapixel (MP or Mpx) is one million pixels, and is a term used not only for the number of pixels in an image, but also to express the number of image sensor elements of digital cameras or the number of display elements of digital displays. For example, a camera with an array of 2048 × 1536 sensor elements is commonly said to have "3.1 megapixels" (2048 × 1536 = 3,145,728).


Digital cameras use photosensitive electronics, either charge-coupled device (CCD) or complementary metal–oxide–semiconductor (CMOS) image sensors, consisting of a large number of single sensor elements, each of which records a measured intensity level. In most digital cameras, the sensor array is covered with a patterned color filter mosaic having red, green, and blue regions in the filter arrangement, so that each sensor element can record the intensity of a single primary color of light. The camera interpolates the color information of neighboring sensor elements, through a process called demosaicing, to create the final image. These sensor elements are often called "pixels", even though they only record 1 channel (only red, or green, or blue) of the final color image. Thus, two of the three color channels for each sensor must be interpolated and a so-called N-megapixel camera that produces an N-megapixel image provides only one-third of the information that an image of the same size could get from a scanner. Thus, certain color contrasts may look fuzzier than others, depending on the allocation of the primary colors.



In CFM, the Maintenance End Point (MEP) port in an MA has the ability to send pro-active connectivity check (CC) packets and get information about other MEP ports from the CC packets of neighboring switches within the MA.


Mesh Network

A type of multipoint-to-multipoint network in which each node has a connection to more than one other node, forming a "mesh" or lattice. In a mesh network, all nodes can communicate with all other nodes along more than one path. This redundancy means that mesh networks tend to be resilient, coping with disruptions to one signal path by rerouting to another.


Message Digest

A message digest is the fixed-length encrypted output that is the result of applying a hash to plain text input. The message digest functions as a digital fingerprint of the original message. A message digest provides a way to check the integrity of a message. If someone changes the original message, it produces a different message digest. See also Hash.


Message Waiting

Message waiting notifies you when a voice message arrives. The details of the message waiting feature depend on your telephone and your voice mail service.


Message Waiting Indication (MWI) Tone

The Message Waiting Indication (MWI) tone indicates a voicemail message is waiting.



Multiple Extended Service Set IDentifier (MESSID) allows one access point to operate several independent wireless networks (ESSs), each with configurable wireless and security settings.


Multi-Function Peripheral. Hardware that combines several functions in a single unit, such as a combined fax, copier, printer and scanner.



The management PVC is a PVC dedicated for management traffic transmissions.



A Management Information Base (MIB) is a collection of managed objects. The managed devices contain object variables/managed objects that define each piece of information to be collected about a device. Examples of variables include such as the number of packets received, node port status and so on.



Message Integrity Check (MIC) is a function designed to detect if someone has covertly altered data packets. The receiver and the transmitter each compute and compare the MIC. If they do not match, it is assumed that the data has been tampered with and the packet is dropped.


Microsoft RDP

Microsoft's Remote Desktop Protocol (RDP) allows you to access a computer through the Internet in order to work with its files, programs and resources. It uses TCP port 3389 by default.



This is software that provides a way for two systems to exchange information or connect with one another even though they have different interfaces. For example, you can use middleware to have a VDSL based router communicate with a set-top box.


MIME Headers

Multipurpose Internet Mail Extensions (MIME) allows varied media types to be used in e-mail. MIME headers describe an e-mail's content encoding and type.



MIMO (Multiple In, Multiple Out) is a radio signal distribution technique used in wireless networks. A MIMO wireless device possesses two or more antennas which process data simultaneously, increasing throughput. Is radio technology that utilizes multiple antennas at both the transmitter and receiver to improve range and performance.



A Mini Gigabit Interface Converter complies with the Small Form-factor Pluggable (SFP) Transceiver MultiSource Agreement (MSA). See the SFF committee's INF-8074i specification Rev 1.0 for details. See also GBIC.



In CFM, the Maintenance Intermediate Point (MIP) port in an MA only forwards connectivity check (CC) packets.


Mirroring (Disk)

In a RAID system using mirroring, data is copied to a duplicate hard disk. This provides 100% data redundancy as if one disk fails the other has the duplicated data. Mirroring always requires an even number of drives. See also RAID, Duplexing.


Mirror Port

This is a port that copies the network traffic of another port for the purpose of analyzing the network traffic. This is also known as the sniffer port or the analysis port.


MLD snooping, MLD proxy

MLD snooping and MLD proxy are analogous to IGMP snooping and IGMP proxy in IPv4.



A Metallic Line Test (MLT) tests the condition of a physical line used for VoIP.



Multimedia Messaging Service (MMS) allows the transfer of messages in the same way as SMS, but with the addition of multimedia objects such as pictures, audio, video and rich text.


MOD Port Isolation

Multimedia on Demand (MoD) port isolation stops communication between the specified port (on which the MoD service is provided) and other Ethernet ports to prevent interference from other ports.


Modulation technique

A modulation technique is a method used to encode digital or analog information onto an analog carrier signal so it can be transmitted. A modem modulates digital data onto an analog signal to send over the telephone network. The receiving modem demodulates the analog signals back to digital data. The specific frequency at which the information is modulated on the analog signal is called the carrier.


Monitor Port

This is a port whose traffic is duplicated and analyzed by a sniffer port. This is also known as the source port.



MPEG-4 is an audio/video compression/decompression algorithm technology developed by the Motion Picture Experts Group.



In a WiMAX network, mobile stations connect wirelessly to a base station for network access. Mobile stations use the IEEE 802.16e standard that allows rapid transition from one cell to another.



MS-CHAP, Microsoft CHAP (Challenge Handshake Authentication Protocol) uses a challenge-response mechanism where the response is encrypted.



Microsofts Challenge-Handshake Authentication Protocol (MS-CHAP-V2) is used to periodically verify the identity of a peer (station or other AP) through mutual authentication.



Minimum Square Error (MSE) is the minimum mean-square error (also known as MMSE) performance measure is a popular metric for optimal signal processing.



A Multiple Subscriber Number (MSN) is similar to a conventional telephone extension number, but is issued by a service provider for use on an ISDN line. When an incoming call includes an MSN in addition to the line number (111111222, for example, where 111111 is the line number and 222 is the MSN) only ISDN phones configured with that MSN will ring.



An MST Instance (MSTI) is a set of VLANs that use the same spanning tree. See also MSTP.



Multiple Spanning Tree Protocol (IEEE 802.1s) is backward-compatible with STP/RSTP. In MSTP, switching devices are grouped into a region which appears as a single network to the outside world. With MSTP, a switch can set up more than one spanning tree. In addition, more than one VLAN can exist in a spanning tree.


MST Region

An MST (Multiple Spanning Tree) region is a logical grouping of multiple network devices that appears as a single device to the rest of the network. See also MSTP.



Mean Time Between Failures (MTBF) is the average time between system hardware failures.



Buildings such as hotels, motels, resorts, residential multi-dwelling units, office buildings, university campuses, etc.



Mu-Law and A-Law are Pulse Code Modulation (PCM) techniques that dictate forms of compression for audio signals. They are widely-used standard methods of coding voice as they improve the signal-to-noise ratio without increasing the amount of data. Mu-Law is a standard in North America; A-Law in Europe.



Deliver IP packets to a specific group of hosts using IP multicast. IGMP (Internet Group Management Protocol) is the protocol used to support multicast groups.


Multicast Bandwidth Control

Some DSLAMs can limit bandwidth for multicast channels. During IGMP snooping, the system checks the total bandwidth usage to see if it exceeds the specified limit. If the specified limits are reached, the system restricts the joining of multicast groups.


Multicast Delivery Tree

In DVMRP, multicast packets are forwarded along the multicast delivery tree branches. DVMRP dynamically learns host membership information using Internet Group Multicast Protocol (IGMP). The trees are updated dynamically to track the membership of individual groups.


Multicast Group Limit

Some service provider switches can limit the number of IGMP multicast groups a subscriber on a port can join.


Multicast Listener Discovery (MLD)

The Multicast Listener Discovery (MLD) protocol is derived from IPv4's Internet Group Management Protocol version 2 (IGMPv2). MLD uses ICMPv6 message types, rather than IGMP message types. MLDv1 is equivalent to IGMPv2 and MLDv2 is equivalent to IGMPv3.



Multiple ESS is a function that allows multiple ESSs to be configured on just one access point. Wireless stations can use different ESSIDs to associate with the same AP. Only wireless stations with the same ESSID can communicate with each other. This allows the AP to logically group wireless stations in a manner similar to VLAN (Virtual LAN).


Multiple PVC

Some DSLAMs support more than one Permanent Virtual Circuit per DSL port. The PVCs can be used in providing different services to subscribers.



Multiplexing takes numerous individual data subchannels and combines them into a single stream. This can be done by using time division multiplexing (TDM), frequency division multiplexing (FDM), code division multiplexing (CDM), or wave division multiplexing (WDM). A multiplexer (sometimes referred to as a MUX) combines subchannels into the single stream, and a demultiplexer (sometimes referred to as a DEMUX) extracts subchannels from the single stream.



Multiplexors or MUXs, as they are often called, are devices that combine signals from various sources such as PBX (Private Branch Exchange), asynchronous terminals or a bridge connected to a WAN. A multiplexor transmits these signals as a single data stream over a digital line. Multiplexors conserve bandwidth.



A network configuration in which each node (host computer) can communicate with numerous other nodes.



Multicast VLAN Group (MVG) is designed for applications (such as Media-on-Demand (MoD)) using multicast traffic across an Ethernet network. MVG allows one single multicast VLAN to be shared among different subscriber VLANs on the network. This improves bandwidth utilization by reducing multicast traffic in the subscriber VLANs and simplifies multicast group management. MVG is also known as Multicast VLAN Registration (MVR).



Multicast VLAN (MVLAN) allows different subscriber VLANs to share a single multicast VLAN. This improves bandwidth utilization by reducing multicast traffic in the subscriber VLANs and simplifies multicast group management.



Multicast VLAN Registration (MVR) is designed for applications (such as Media-on-Demand (MoD)) using multicast traffic across an Ethernet network. MVR allows one single multicast VLAN to be shared among different subscriber VLANs on the network. This improves bandwidth utilization by reducing multicast traffic in the subscriber VLANs and simplifies multicast group management. MVR is also known as Multicast VLAN Group (MVG).


MX Record

A MX (Mail eXchange) record identifies a mail server that handles the mail for a particular domain.