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||jitter (in the context of computer networks) is a measure of the variance of latency (pings) accross the network. Jitter in a network can be measured using the time variation in successive pings. The jitter (packet delay variation) is the amount by which pings vary.
Zero jitter in a network means that all pings to a host are exactly the same every time. While some jitter should be expected over the Internet, a lower jitter value is better, having it be a small fraction of the ping result is ideal.
In general, jitter is a significant, and usually undesired factor in the design of almost all communications links (e.g. USB, SATA, as well as all network/internet connections).
Jitter buffers or de-jitter buffers are used to counter jitter introduced by queuing in packet switched networks so that a continuous playout of audio or video transmitted over the network can be ensured. This works, however the buffer adds delay, and is finite in size (if it gets full packets will get discarded).
||Kbps (Kilobits per second, not to be confused with KBps) stands for thousands of bits per second or kilobits per second and is a measure of bandwidth (the total information flow over a given time) on a communications medium.
A kilobit is a thousand bits (binary pulses), or 1,000 (10^3) bits. Bits in data communications are discrete signal pulses and have historically been counted using the decimal number system.
See also: Bits/Bytes conversion calculator
||Kerberos is a network authentication system based on key distribution. It allows entities that communicate over a wired or wireless network to prove their identity to each other while preventing eavesdropping or replay attacks. It also provides for data stream integrity (detection of modification) and secrecy (preventing unauthorized reading) using cryptography systems such as DES.
Kerberos works by providing principals (users or services) with digital tickets that they can use to identify themselves to the network and secret cryptographic keys for secure communications. A ticket is a sequence of a few hundred bytes that can be embedded in virtually any other network protocol, thereby allowing the processes implementing that protocol to be sure about the identity of the principals involved.
Kerberos is available free from MIT and as a product from many different vendors.
||KVM (Keyboard, Video Mouse) switch is a hardware device that allows a single keyboard, video(monitor) and mouse to be used with a number of computers, when a single user interacts with all the computers (one at a time).
||L2TP (Layer Two Tunneling Protocol) is a tunneling protocol used by ISPs to enable the operation of VPN (Virtual Private Network) over the Internet.
L2TP merges the best features of two other tunneling protocols: PPTP from Microsoft and L2F from Cisco Systems. Like PPTP, L2TP requires that the ISP's routers support the protocol.
||A Local Area Network (LAN) is a computer network of devices within a small geographic area such as a home, computer lab, or an office building that share a common communications line. A LAN may serve as few as two or three, or as many as thousands of users. The most common type of local area network is an Ethernet LAN.
A LAN in turn can be connected to other LANs over any distance. A system of LANs connected via various data lines is called a wide area network (WAN), like the Internet.
||Latency, or simply delay is an expression of how much time it takes for a packet of data to get from one designated point to another. Latency is often measured by sending a packet that is returned to the sender and the round-trip time (RTT) is considered the latency.
||LEAP (Lightweight EAP) is a Cisco authentication technology for securing wireless networks with WEP-based devices.
See also: EAP, EAP-FAST
||LEC (Local Exchange Carrier) - a local telephone company.
Local carriers are responsible for the "last mile" of all connections to the Internet. When a customer purchases a circuit through a Tier 1 carrier (IXC), the carrier sends the LEC an order to provision a connection from the closest Central Office to the customer's premise. The IXC and the LEC must also arrange connectivity between the carrier's POP and the LEC's CO.
||Low Earth Orbit Satellites
||LNB (Low Noise Block Converter) is a device placed in the focal point of a satellite dish which amplifies the incoming signal and converts the frequencies for use by a satellite receiver.
||Load balancing refers to the distribution of communications activity evenly across a computer network, or multiple physical circuits, to provide for redundancy and additional bandwidth. Border Gateway Protocol (BGP) and Cisco Express Forwarding are some examples of load balancing technology.
||LTE (Long Term Evolution) is the last step toward the 4th generation of radio technologies designed to increase the capacity and speed of mobile telephone networks.
Where the current generation of mobile telecommunication networks are collectively known as 3G (for "third generation"), LTE is marketed as and called 4G insinuating that it's the "fourth generation". Most major mobile carriers are converting their networks to LTE since 2009.
LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) introduced in 3rd Generation Partnership Project (3GPP) Release 8. Much of 3GPP Release 8 focuses on adopting 4G mobile communications technology, including an all-IP flat networking architecture.
||MAC (Media Access Control) address is a unique number assigned to any Ethernet networking device by the manufacturer. The MAC address is permanent (unlike IP addresses) and therefore valuable identifier that allows a network to identify the hardware.
||MAE (Metropolitan Area Exchange) is a major public network access point (NAP) for interconnecting traffic between ISPs. The terms MAE and NAP are often used interchangeably.
The term MAE is sometimes used to only identify the first NAPs set up by MFS Communications/MCI Worldcom:
MAE-East (Washington D.C.), MAE-Central (Dallas, TX), MAE-West (San Jose, CA), as well as the two MAE FE - Frame Encapsulation (FE), Packet over SONET (POS) services in Chicago and NY.
Basically, MAEs/NAPs are major interconnection points (and often the congestion points) that determine how/where traffic is routed in what is considered the Internet backbone.
||Malware (malicious software) is a general term that describes any type of software used to disrupt computer systems, show unwanted advertising, or gather sensitive informaiton.
Malware it typically installed covertly on a victim's computer, and can remain stealthy if intended to steal information or spy on a user for an extended period without their knowledge (spyware). Other types of malware can cause harm, sabotage, or try to extort payment (ransomware).
||MaxDupAcks - Fast Retransmission and Fast Recovery of TCP connections that are encountering IP packet loss in the network. Allow a TCP sender to quickly infer a single packet loss by reception of duplicate acknowledgements for a previously sent and acknowledged TCP/IP packet. This mechanism is useful when the network is intermittently congested. The reception of 3 successive duplicate acknowledgements indicates to the TCP sender that it can resend the last unacknowledged TCP/IP packet (fast retransmit) and not go into TCP slow start due to a single packet loss (fast recovery).
||Mbps (Megabits per second, not to be confused with MBps) stands for millions of bits per second or megabits per second and is a measure of bandwidth (the total information flow over a given time) on a communications medium.
A megabit is a million bits (binary pulses), or 1,000,000 (10^6) bits. Bits in data communications are discrete signal pulses and have historically been counted using the decimal number system.
See also: Bits/Bytes conversion calculator
||A mesh network is a network topology in which each node relays data for the network. All mesh nodes cooperate in the distribution of data in the network, so that data transfers can take a different path depending on distance, congestion, length, etc.
Mesh networks with multiple nodes offer a great amount of redundancy, so in the event one node fails, network traffic is directed through any of the other nodes. A typical example of mesh network topology is the internet.
One of the main advantages of a mesh network is the number of possible paths for traffic to travel through the network. In a traditional multi-node wireless network, each device can only connect directly to one other device (router to extender/repeater, or extender to another extender). This restricts all traffic to flow in a single path, regardless of congestion or wireless interference degrading the link quality (by 50% for each consecutive wireless hop). A mesh network topology, on the other hand offers redundancy, improved speed, link quality and reliability.
||MIB (Management Information Base) is a database containing ongoing information and statistics on each device in a network. It is used with SNMP to keep track of each device's performance and verify whether it's functioning properly.
||MIME (Multipurpose Internet Mail Extensions). MIME Extends the basic text-oriented Internet mail system in order that messages can contain binary attachments.
||MIMO (multiple input, multiple output) is an antenna technology for wireless communications in which multiple antennas are used simultaneously at both the source and the destination.
MIMO systems provide a significant capacity gain over conventional single antenna systems, along with more reliable communication. Many believe MIMO is the most promising of emerging wireless technologies.
MIMO is a key element of the 802.11n WiFi networking standard.
||MoCA (Multimedia over Coax Alliance) is a standard for home entertainment networking. MoCA uses coaxial cables to connect consumer electronics and home networking devices, allowing both data communication and the transfer of audio and video streams.
The current MoCA 2.0 specification can support multiple streams of HD video, deliver up to 800 Mbps net throughputs and offers parameterized quality of service (PQoS). The MoCA 2.0 standard uses RF signals with an operating frequency range of 500 to 1650 MHz.
The technology is designed so that it does not interfere with the broadcasts of traditional cable TV service. However, satellite TV, which runs on different spectrum, is not compatible with the 1.1 MoCA standard. For their respective multi-room DVR services, they use a proprietary coax networking technology. The MoCA 2.0 standard is expected to work for all service providers.
||modulation is the process of imposing information on carrier signal by varying some parameter of the carrier. The parameters that can be varied are the amplitude, frequency or phase.
||MPEG (Moving Pictures Experts Group) is a committee formed by the ISO to set standards for digital compression of full-motion video. Also stands for the digital compression standards created by this committee.
Below are some current standards for video/audio digital compression created by the comittee:
MPEG-1 - VHS quality, full-motion video (mp3 is derived from MPEG-1, audio layer-3)
MPEG-2 - broadcast quality, full-motion video (digital TV, DVD)
MPEG-3 - broadcast quality audio (High Definition TV, it has been merged with MPEG-2)
MPEG-4 - "speech and video synthesis, fractal geometry, computer visualization, and an artificial intelligence (AI) approach to reconstructing images..."
||MRC (Monthly Recurring Charges). The MRC for a circuit includes recurring charges not associated with installation, primarily port and loop charges.
||MS-DOS (MicroSoft Disk Operating System) - A clone of CP/M for the 8088 crufted together in 6 weeks by hacker Tim Paterson at Seattle Computer Products, who called the original QDOS (Quick and Dirty Operating System) and is said to have regretted it ever since. Microsoft licensed QDOS in order to have something to demo for IBM on time, and the rest is history...
||Multi-system operator (MSO) is an operator of multiple cable, or direct-broadcast satellite television systems. Any cable company that serves multiple communities is an MSO.
The term is widely used for companies that own a large number of cable systems, such as: Comcast, Time Warner Cable, Rogers Communications, Shaw Communications, Virgin Media, etc.
||MSS (Maximum Segment Size) defines the largest segment of TCP (Transfer Control Protocol) data that the Winsock is prepared to receive. When a connection is established, the two ends agree to use the smaller of each end's value. Because headers are typically 40 bytes, MSS is usually 40 less than the MTU (Maximum Transmission Unit).
||MTBF (Mean Time Between Failure) A measure of the average time interval between a previous failure and the onset of the next failure of a device or network.
||MTU (Maximum Transmission Unit) is the greatest amount of data that can be transferred in one physical frame on the network. If a packet that has a smaller MTU than the packet's frame length is sent, fragmentation will occur. For TCP (Transmission Control Protocol) MTU can range from 68 to 1500 bytes. Larger MTUs provide for lower overhead (fewer headers).
||MTU Discovery ( RFC1191 ) determines whether TCP uses a fixed, default maximum transmission unit (MTU) or attempts to find the actual MTU. If the value of this entry is 0, TCP uses an MTU of 576 bytes for all connections to computers outside of the local subnet. If the value of this entry is 1, TCP attempts to discover the MTU (largest packet size) over the path to a remote host.
Note: the setting under Windows NT 4 is EnablePMTUDiscovery.
||MU-MIMO (multi-user, multiple-input and multiple-output) is a technology that uses multi-user beamforming, letting wireless access points send different data streams to different receivers at the same time. It is part of the newer-generation 802.11ac wireless networking, and only getting implemented into latest models. MU-MIMO acts similarly to a network "switch", being able to send different data to different receivers at the same time.
||Multicast is a technique in which packets are simultaneously sent to multiple recipients on a network.
More specifically, multicast is a mechanism for defining groups of nodes, and sending IP messages to that group, rather than to every node on the LAN (broadcast), or just a single node (unicast).
It is often used to send an audio and/or video program to multiple users on a network more efficiently. The efficiency is realized by sending only one data stream from the file server, rather than one stream for each recipient. The digital data stream is duplicated as necessary in the downstream path by routers and/or switches in order to account for different signal paths to the end-users.
||Multihomed is typically used to describe a device connected to two or more networks.
Essentially, Cable/DSL modems and NAT routers are multi-homed, because they have an external and an internal IP address on two separate networks, while switches, hubs, and network adapters are not. If a machine has multiple NICs, but is only attached to one network, it is not considered multihomed.
||Multiplexer is a device that allows the transmission of multiple data streams over a common medium. Several communications paths or channels may be either permanently or dynamically established over the medium to accomplish this.
||The transmission of more than one independent signal over a single transmission media. The transmitted signals need not operate continuously or simultaneously in order for multiplexing to have occurred.
||MVNO (Mobile Virtual Network Operator) is a mobile operator that does not own its own spectrum and usually does not have its own network infrastructure. Instead, MVNO's have business arrangements with traditional mobile operators to provide the actual services. MVNO's typically add value such as brand appeal, distribution channels, and other affinities to the resale of mobile services.
||NAP (Network Access Point) is a major public network exchange facility for interconnecting traffic between ISPs.
NAPs (and MAEs) are interconnection points (and often the congestion points) that determine how/where traffic is routed in what is considered the Internet backbone.
The term is often used interchangeably with MAE (Metropolitan Area Exchange), see the MAE term description for more details.
||NAPT (Network Address Port Translation) a.k.a. PAT, port mapping, NAT overloading, port-level NAT, or single-address NAT.
The term refers to an extension to NAT, in which multiple client computers communicate through the same IP, and also have unique port numbers assigned to transmissions in order to distinguish between them.
In other words, NAPT/PAT extends NAT from "one-to-one" into "many-to-one" by associating unique source ports with the data flow.
NAPT is discussed in RFC 2663
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