CushionTheBlow (구 BluemoonSoft)

In the late 19th century, luminiferous aether (or ether), meaning light-bearing aether, was the term used to describe a medium for the propagation of light. The word aether stems via Latin from the Greek αιθήρ, from a root meaning to kindle, burn, or shine. It signified the substance thought in ancient times to fill the upper regions of space, beyond the clouds.

Later theories including special relativity were formulated without the concept of aether. Today the aether is regarded as a superseded scientific theory.

Reference:
http://en.wikipedia.org/wiki/Lumiferous_aether

In telecommunications, a jam signal is a signal that carries a 32-bit binary pattern sent by a data station to inform the other stations that they must not transmit.

In CSMA/CD the maximum jam-time is calculated as follows: The maximum allowed diameter of an Ethernet installation is limited to 232 bits. This makes a round-trip-time of 464 bits. As the slot time in Ethernet is 512 bits, the difference between slot time and RTD is 48 bits (6 bytes), which is the maximum "jam-time".

This in turn means: A station noting a collision has occurred is sending a 4 to 6 byte long pattern composed of 16 1-0 bit combinations. Note: The size of this jam signal is clearly beyond the minimum allowed frame-size of 64 bytes.

Some notes about jam signals include the following:

1. In carrier sense multiple access with collision detection (CSMA/CD) networks, the jam signal indicates that a collision has occurred.
2. In carrier sense multiple access with collision avoidance (CSMA/CA) networks, the jam signal indicates that the sending station intends to transmit.

Reference:
http://en.wikipedia.org/wiki/Jam_signal

In communication and computer network research, network simulation is a technique where a program models the behavior of a network either by calculating the interaction between the different network entities (hosts/routers, data links, packets, etc) using mathematical formulas, or actually capturing and playing back observations from a production network. The behavior of the network and the various applications and services it supports can then be observed in a test lab; various attributes of the environment can also be modified in a controlled manner to assess how the network would behave under different conditions. When a simulation program is used in conjunction with live applications and services in order to observe end-to-end performance to the user desktop, this technique is also referred to as network emulation.

Reference:
http://en.wikipedia.org/wiki/Network_simulation

Network emulation is a technique where the properties of an existing, planned and/or non-ideal network are simulated in order to assess performance, predict the impact of change, or otherwise optimize technology decision-making.

Methods of emulation
Network emulation can be accomplished by introducing a device on the LAN that alters packet flow in a way that imitates the behavior of application traffic in the environment being emulated. This device may be either a general-purpose computer running software to perform the network emulation or a dedicated emulation device. The device incorporate a variety of network attributes into its emulation model – including the round-trip time across the network (latency), the amount of available bandwidth, a given degree of packet loss, duplication of packets, reordering packets, and/or the severity of network jitter. Desktop PCs can be connected to the emulated environment, so that users can experience the performance and behavior of applications in that environment first-hand. Similarly, phones can be connected to the emulated environment so that users can directly assess VoIP call quality for themselves.

Emulation, simulation and traffic generation
Emulation differs from simulation in that a network emulator appears to be a network; end-systems such as computers can be attached to the emulator and will behave as if they are attached to a network. Network simulators are typically programs which run on a single computer, take an abstract description of the network traffic (such as a flow arrival process) and yield performance statistics (such as buffer occupancy as a function of time).

A network emulator emulates the network which connects end-systems, not the end-systems themselves. Systems which emulate the end-systems are called traffic generators.

Reference:
http://en.wikipedia.org/wiki/Network_emulation

IEEE 802 refers to a family of IEEE standards dealing with local area networks and metropolitan area networks. More specifically, the IEEE 802 standards are restricted to networks carrying variable-size packets. (By contrast, in cell-based networks data is transmitted in short, uniformly sized units called cells. Isochronous networks, where data is transmitted as a steady stream of octets, or groups of octets, at regular time intervals, are also out of the scope of this standard.) The number 802 was simply the next free number IEEE could assign, though "802" is sometimes associated with the date the first meeting was held - February 1980.

The services and protocols specified in IEEE 802 map to the lower two layers (Data Link and Physical) of the seven-layer OSI networking reference model. In fact, IEEE 802 splits the OSI Data Link Layer into two sub-layers named Logical Link Control (LLC) and Media Access Control, so that the layers can be listed like this:

- Data link layer
 - LLC Sublayer
 - MAC Sublayer
- Physical layer

The IEEE 802 family of standards is maintained by the IEEE 802 LAN/MAN Standards Committee (LMSC). The most widely used standards are for the Ethernet family, Token Ring, Wireless LAN, Bridging and Virtual Bridged LANs. An individual Working Group provides the focus for each area.

See its working groups:

- IEEE 802.1 Bridging (networking) and Network Management
- IEEE 802.2 Logical link control
- IEEE 802.3 Ethernet
- IEEE 802.4 Token bus (disbanded)
- IEEE 802.5 Defines the MAC layer for a Token Ring
- IEEE 802.6 Metropolitan Area Networks (disbanded)
- IEEE 802.7 Broadband LAN using Coaxial Cable (disbanded)
- IEEE 802.8 Fiber Optic TAG (disbanded)
- IEEE 802.9 Integrated Services LAN (disbanded)
- IEEE 802.10 Interoperable LAN Security (disbanded)
- IEEE 802.11 Wireless LAN & Mesh (Wi-Fi certification)
- IEEE 802.12 demand priority
- IEEE 802.13 Cat.6 - 10Gb lan (new founded)
- IEEE 802.14 Cable modems (disbanded)
- IEEE 802.15 Wireless PAN
 - IEEE 802.15.1 (Bluetooth certification)
 - IEEE 802.15.4 (ZigBee certification)
- IEEE 802.16 Broadband Wireless Access (WiMAX certification)
 - IEEE 802.16e (Mobile) Broadband Wireless Access
- IEEE 802.17 Resilient packet ring
- IEEE 802.18 Radio Regulatory TAG
- IEEE 802.19 Coexistence TAG
- IEEE 802.20 Mobile Broadband Wireless Access
- IEEE 802.21 Media Independent Handoff
- IEEE 802.22 Wireless Regional Area Network

Reference:
http://en.wikipedia.org/wiki/IEEE_802

In computer networking, the Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to support virtual private networks (VPNs).

Reference:
http://en.wikipedia.org/wiki/L2tp

Generic Routing Encapsulation (GRE) is a tunneling protocol designed to encapsulate a wide variety of network layer packets inside IP tunneling packets. The original packet is the payload for the final packet. The protocol is used on the Internet to secure virtual private networks.

GRE was developed by Cisco and was designed to be stateless; the tunnel end-points do not monitor the state or availability of other tunnel end-points. This feature helps service providers support IP tunnels for clients, who won't know the service provider's internal tunneling architecture; and it gives clients the flexibility of reconfiguring their IP architectures without worrying about connectivity. GRE creates a virtual point-to-point link with routers at remote points on an IP internetwork.

One key difference between an encrypted GRE tunnel and an IPsec tunnel is the ability to make use of Multicast protocols over GRE tunnels. An example would be the use of OSPF over a GRE tunnel.

GRE uses IP protocol number 47.

Reference:
http://en.wikipedia.org/wiki/Generic_Routing_Encapsulation

Simplex communication is a name for a type of communication circuit. There are two (contradictory) definitions that have been used for the term. When one definition is used for "simplex" then the other definition is referred to as half duplex.

Reference:
http://en.wikipedia.org/wiki/Simplex_communication

In computing, memoization is an optimization technique used primarily to speed up computer programs by having function calls avoid repeating the calculation of results for previously-processed inputs. Memoization has also been used in other contexts (and for other purposes other than speed gains), such as in simple mutually-recursive descent parsing by Norvig, in a general top-down parsing algorithm by Frost, Hafiz and Callaghan that accommodates ambiguity and left-recursion in polynomial time and space. Although related to caching, memoization refers to a specific case of this optimization, distinguishing it from forms of caching such as buffering or page replacement.

Reference:
http://en.wikipedia.org/wiki/Memoization

In computing, an abstract data type (ADT) is a specification of a set of data and the set of operations that can be performed on the data. Such a data type is abstract in the sense that it is independent of various concrete implementations. The definition can be mathematical, or it can be programmed as an interface. A first class ADT supports the creation of multiple instances of the ADT, and the interface normally provides a constructor, which returns an abstract handle to new data, and several operations, which are functions accepting the abstract handle as an argument.

Reference:
http://en.wikipedia.org/wiki/Abstract_data_type