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Certpedia: Terms That Start With L


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  • L2TP (Layer 2 Tunneling Protocol) - Published in 1999 as proposed standard RFC 2661, L2TP has its origins primarily in two older tunneling protocols for PPP: Cisco's Layer 2 Forwarding (L2F) and Microsoft's Point-to-Point Tunneling Protocol (PPTP). A new version of this protocol, L2TPv3, was published as proposed standard RFC 3931 in 2005. L2TPv3 provides additional security features, improved encapsulation, and the ability to carry data links other than simply PPP over an IP network (e.g., Frame Relay, Ethernet, ATM, etc). L2TP acts as a data link layer (layer 2 of the OSI model) protocol for tunneling network traffic between two peers over an existing network (usually the Internet). It is common to carry Point-to-Point Protocol (PPP) sessions within an L2TP tunnel. L2TP does not provide confidentiality or strong authentication by itself. IPsec is often used to secure L2TP packets by providing confidentiality, authentication and integrity. The combination of these two protocols is generally known as L2TP/IPsec.




  • LANLAN (Local Area Network) - A computer network that spans a relatively small area and typically offers high-speed communications. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines, coaxial cable, wi-fi, etc. A system of LANs connected in this way is called a wide area network (WAN). Most LANS of today utilize Ethernet and/or Wi-Fi connections.




  • Latency - (AKA "lag") is the amount of time it takes a packet of data to move across a network connection. When a packet is being sent, there is "latent" time, when the computer that sent the packet waits for confirmation that the packet has been received. Latency and bandwidth are the two factors that determine your network connection speed. Latency in a packet-switched network is measured either one-way (the time from the source sending a packet to the destination receiving it), or round-trip (the one-way latency from source to destination plus the one-way latency from the destination back to the source). Round-trip latency is more often quoted, because it can be measured from a single point. Note that round trip latency excludes the amount of time that a destination system spends processing the packet. Many software platforms provide a service called ping that can be used to measure round-trip latency. Ping performs no packet processing; it merely sends a response back when it receives a packet, thus it is a relatively accurate way of measuring latency.



  • LDAP (Lightweight Directory Access Protocol) - A protocol used to access listings in hierarchical information directories (databases). LDAP is a simplified version of the standard used to gain access to X.500 directories. Microsoft's Active Directory which was first released in Windows 2000 utilizes LDAP for locating records in the directory.




  • Link State Routing Protocols are one of the two main classes of routing protocols used in packet switching networks and includes protocols such as Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS). The link-state protocol is performed on every router on the network, where every routing node constructs a map of the connectivity to the network by showing which nodes are connected to each other. Each router calculates the next best logical hop from it to every possible known destination which forms the node's routing table.




  • Lithium-Ion - Lithium-ion rechargeable batteries generally provide more energy capacity than nickel based types of the same weight. They also do not suffer from "memory effect" and are non-toxic. These batteries are used in many devices including laptops, cell phones, and digital cameras.




  • Load Balancing - is a technique to distribute workload evenly across two or more computers, network links, CPUs, hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, minimize response time, and avoid overload. Using multiple components with load balancing, instead of a single component, may increase reliability through redundancy. The load balancing service is usually provided by a dedicated program or hardware device (such as a multilayer switch or a DNS server).








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