Telemetry An expendable dropsonde used to capture weather data. The telemetry consists of sensors for pressure, temperature, and humidity and a wireless transmitter to return the captured data to an aircraft. Telemetry is the highly automated communications process by which measurements are made and other data collected at remote or inaccessible points and transmitted to receiving equipment for monitoring.[1] The word is derived from Greek roots: tele = remote, and metron = measure. Although the term commonly refers to wireless data transfer mechanisms (e.g., using radio, ultrasonic, or infrared systems), it also encompasses data transferred over other media such as a telephone or computer network, optical link or other wired communications like phase line carriers. A telemeter is a device used to remotely measure any quantity. History[edit] Telemetering information over wire had its origins in the 19th century. Applications[edit] Meteorology[edit] Oil and gas industry[edit] Space science[edit]
RFC 4271 - A Border Gateway Protocol 4 (BGP-4) [Docs] [txt|pdf] [draft-ietf-idr-bgp4] [Diff1] [Diff2] [Errata] Updated by: 6286, 6608, 6793 DRAFT STANDARD Errata Exist Network Working Group Y. Rekhter, Ed. Request for Comments: 4271 T. Li, Ed. Obsoletes: 1771 S. RFC 4271 BGP-4 January 2006 Table of Contents 1. RFC 4271 BGP-4 January 2006 8.2.1.5. RFC 4271 BGP-4 January 2006 1. The Border Gateway Protocol (BGP) is an inter-Autonomous System routing protocol. 1.1. This section provides definitions for terms that have a specific meaning to the BGP protocol and that are used throughout the text. Virtual private network VPN connectivity overview A virtual private network connection across the Internet is similar to a wide area network (WAN) link between sites. From a user perspective, the extended network resources are accessed in the same way as resources available within the private network.[2] VPNs allow employees to securely access their company's intranet while traveling outside the office. Types[edit] Early data networks allowed VPN-style remote connectivity through dial-up modems or through leased line connections utilizing Frame Relay and Asynchronous Transfer Mode (ATM) virtual circuits, provisioned through a network owned and operated by telecommunication carriers. VPNs can be either remote-access (connecting an individual computer to a network) or site-to-site (connecting two networks together). VPN systems may be classified by: Security mechanisms[edit] To prevent disclosure of private information, VPNs typically allow only authenticated remote access and make use of encryption techniques.
RFC 2460 - Internet Protocol, Version 6 (IPv6) Specification [Docs] [txt|pdf] [draft-ietf-ipngwg...] [Diff1] [Diff2] [Errata] Updated by: 5095, 5722, 5871, 6437, 6564, 6935, DRAFT STANDARD 6946, 7045, 7112 Errata Exist Network Working Group S. Deering Request for Comments: 2460 Cisco Obsoletes: 1883 R. Hinden Category: Standards Track Nokia December 1998 Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. RFC 2460 IPv6 Specification December 1998 Appendix A. 1. IP version 6 (IPv6) is a new version of the Internet Protocol, designed as the successor to IP version 4 (IPv4) [RFC-791]. RFC 2460 IPv6 Specification December 1998 o Authentication and Privacy Capabilities Extensions to support authentication, data integrity, and (optional) data confidentiality are specified for IPv6. 2. 3. 4.
IEC 61131-3 IEC 61131-3 is the third part (of 8) of the open international standard IEC 61131 for programmable logic controllers, and was first published in December 1993 by the IEC. The current (third) edition was published in February 2013. Part 3 of IEC 61131 deals with programming languages and defines two graphical and two textual PLC programming language standards: Data types[edit] (Considering byte size 8 bits) Variables[edit] Variable attributes: RETAIN, CONSTANT, AT GlobalDirect (local)I/O Mapping - Input, Output, I/OExternalTemporary Configuration[edit] Resource - Like a CPUTasks - Can be multiple per CPU.Programs - Can be executed once, on a timer, on an event. Program organization units[edit] Functions Standard: ADD, SQRT, SIN, COS, GT, MIN, MAX, AND, OR, etc.CustomFunction Blocks Standard:Custom - Libraries of functions can be supplied by a vendor or third party.Programs Configuration, resources, tasks[edit] Configuration - processing resources, memory for IO, execution rates, number of tasks.
RFC 2740 - OSPF for IPv6 [Docs] [txt|pdf] [draft-ietf-ospf-o...] [Diff1] [Diff2] [Errata] Obsoleted by: 5340 PROPOSED STANDARD Errata Exist Network Working Group R. Coltun Requests for Comments: 2740 Siara Systems Category: Standards Track D. RFC 2740 OSPF for IPv6 December 1999 All of OSPF for IPv4's optional capabilities, including on-demand circuit support, NSSA areas, and the multicast extensions to OSPF (MOSPF) are also supported in OSPF for IPv6. RFC 2740 OSPF for IPv6 December 1999 1. This document describes the modifications to OSPF to support version 6 of the Internet Protocol (IPv6). 1.1. This document attempts to use terms from both the OSPF for IPv4 specification ([Ref1]) and the IPv6 protocol specifications ([Ref14]). 2.
Serial communication In telecommunication and computer science, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole, on a link with several parallel channels. Serial communication is used for all long-haul communication and most computer networks, where the cost of cable and synchronization difficulties make parallel communication impractical. Serial computer buses are becoming more common even at shorter distances, as improved signal integrity and transmission speeds in newer serial technologies have begun to outweigh the parallel bus's advantage of simplicity (no need for serializer and deserializer, or SerDes) and to outstrip its disadvantages (clock skew, interconnect density). Cables that carry serial data[edit] Keyboard and mouse cables and ports are almost invariably serial -- such as PS/2 port and Apple Desktop Bus and USB. See also[edit]
RFC 791 - Internet Protocol [Docs] [txt|pdf] [Errata] Updated by: 1349, 2474, 6864 INTERNET STANDARD Errata Exist RFC: 791 INTERNET PROTOCOL DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION September 1981 prepared for Defense Advanced Research Projects Agency Information Processing Techniques Office 1400 Wilson Boulevard Arlington, Virginia 22209 by Information Sciences Institute University of Southern California 4676 Admiralty Way Marina del Rey, California 90291 September 1981 Internet Protocol TABLE OF CONTENTS PREFACE ........................................................ iii 1. INTRODUCTION ..................................................... 1 1.1 Motivation .................................................... 1 1.2 Scope ......................................................... 1 1.3 Interfaces .................................................... 1 1.4 Operation ..................................................... 2 2. September 1981 Internet Protocol [Page ii] 1.1. 1.2. 1.3. 1.4. 2.1. 2.2. 2.3. 2.4. 3.1.
Parallel communication In telecommunication and computer science, parallel communication is a method of conveying multiple binary digits (bits) simultaneously. It contrasts with serial communication, which conveys only a single bit at a time; this distinction is one way of characterizing a communications link. The basic difference between a parallel and a serial communication channel is the number of electrical conductors used at the physical layer to convey bits. Parallel communication implies more than one such conductor. Examples of parallel communication systems[edit] IBM System/360 Direct Control Feature (1964).[1]:p.18. Comparison with serial links[edit] Before the development of high-speed serial technologies, the choice of parallel links over serial links was driven by these factors: References[edit] This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188). See also[edit]
Border Gateway Protocol BGP may be used for routing within an AS. In this application it is referred to as Interior Border Gateway Protocol, Internal BGP, or iBGP. In contrast, the Internet application of the protocol may be referred to as Exterior Border Gateway Protocol, External BGP, or EBGP. Current version[edit] The current version of BGP is version 4 (BGP4) codified in RFC 4271 since 2006. Uses[edit] Most Internet service providers must use BGP to establish routing between one another (especially if they are multihomed). Very large private IP networks use BGP internally. Operation[edit] Filtering routes learned from peers, their transformation before redistribution to peers or before plumbing them into the routing table is typically controlled via route-maps mechanism. Extensions negotiation[edit] During the peering handshake, when OPEN messages are exchanged, BGP speakers can negotiate[5] optional capabilities of the session, including multiprotocol extensions and various recovery modes. Communities[edit]
How Ethernet Works" Bridges can reduce congestion by allowing multiple conversations to occur on different segments simultaneously, but they have their limits in segmenting traffic as well. An important characteristic of bridges is that they forward Ethernet broadcasts to all connected segments. This behavior is necessary, as Ethernet broadcasts are destined for every node on the network, but it can pose problems for bridged networks that grow too large. When a large number of stations broadcast on a bridged network, congestion can be as bad as if all those devices were on a single segment. Routers are advanced networking components that can divide a single network into two logically separate networks. Routers operate based on protocols that are independent of the specific networking technology, like Ethernet or token ring (we'll discuss token ring later). See How Routers Work for a detailed discussion of this technology.
Dijkstra's algorithm Graph search algorithm The algorithm exists in many variants. Dijkstra's original algorithm found the shortest path between two given nodes,[6] but a more common variant fixes a single node as the "source" node and finds shortest paths from the source to all other nodes in the graph, producing a shortest-path tree. For a given source node in the graph, the algorithm finds the shortest path between that node and every other.[7]: 196–206 It can also be used for finding the shortest paths from a single node to a single destination node by stopping the algorithm once the shortest path to the destination node has been determined. For example, if the nodes of the graph represent cities and costs of edge paths represent driving distances between pairs of cities connected by a direct road (for simplicity, ignore red lights, stop signs, toll roads and other obstructions), then Dijkstra's algorithm can be used to find the shortest route between one city and all other cities. (where . History[edit]
How LAN Switches Work" If you have read other HowStuffWorks articles on networking or the Internet, then you know that a typical network consists of: nodes (computers)a connecting medium (wired or wireless)specialized network equipment like routers or hubs. In the case of the Internet, all of these pieces work together to allow your computer to send information to another computer that could be on the other side of the world! Switches are another fundamental part of many networks because they speed things up. Switches allow different nodes (a network connection point, typically a computer) of a network to communicate directly with one another in a smooth and efficient manner. There are many different types of switches and networks.
Open Shortest Path First OSPF is perhaps the most widely used interior gateway protocol (IGP) in large enterprise networks. IS-IS, another link-state dynamic routing protocol, is more common in large service provider networks. The most widely used exterior gateway protocol is the Border Gateway Protocol (BGP), the principal routing protocol between autonomous systems on the Internet. Overview[edit] The OSPF routing policies to construct a route table are governed by link cost factors (external metrics) associated with each routing interface. Cost factors may be the distance of a router (round-trip time), network throughput of a link, or link availability and reliability, expressed as simple unitless numbers. An OSPF network may be structured, or subdivided, into routing areas to simplify administration and optimize traffic and resource utilization. By convention, area 0 (zero) or 0.0.0.0 represents the core or backbone region of an OSPF network. Neighbor relationships[edit] OSPF message types[edit] Hello: