Router Installation and Configuration Manual/Glossary

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Asymmetric Digital Subscriber Line (ADSL) - form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. This is accomplished by utilizing frequencies that are not used by a voice telephone call. A splitter or micro filters allow a single telephone connection to be used for both ADSL service and voice calls at the same time. However, this technology is not perferred if the distances exceed 5km (approx. 3 miles).

Asymmetric Digital Subscriber Line (ADSL2) - is an ITU (International Telecommunication Union) standard, also referred to as ADSL2 (and Seamless Rate Adaptation). It extends the capability of basic ADSL in data rates. The data rates can, in the best situation, be as high as 12 Mbit/s downstream and 3.5 Mbit/s upstream depending on line quality. The distance from the DSLAM to the customer's equipment is usually the most significant factor in line quality.

Asymmetric Digital Subscriber Line (ADSL2+) - ADSL2+ is capable of doubling the frequency band of typical ADSL connections from 1.1 MHz to 2.2 MHz. This doubles the downstream data rates of the previous ADSL2 standard of up to 12 Mbit/s, but like the previous standards will degrade from its peak bitrate after a certain distance.

Asynchronous Transfer Mode (ATM) - cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells. ATM provides data link layer services that run over SONET (Synchronous Optical Networking) Layer 1 links. This differs from other technologies based on packet-switched networks (such as the Internet Protocol or Ethernet), in which variable sized packets (sometimes known as frames) are used. ATM is a connection-oriented technology, in which a logical connection is established between the two endpoints before the actual data exchange begins.

Basic Input/Output System (BIOS) - The BIOS software is built into the equipment, and is the first code run by a unit when powered on ('boot firmware'). The primary function of the BIOS is to load and start an operating system. When the unit starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk, CD/DVD drive and other hardware. The BIOS then locates software held on a peripheral device (designated as a 'boot device'), such as a hard disk or a CD, and loads and executes that software, giving it control of the PC

Border Gateway Protocol (BGP) - the core routing protocol of the Internet. It works by maintaining a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). BGP makes routing decisions based on path, network policies and/or rulesets.

Crypto IP Encapsulation (CIPE) - CIPE is a VPN implementation developed primarily for Linux. CIPE uses encrypted IP packets that are encapsulated, or "wrapped", in datagram (UDP) packets. Packets are given destination header information and are encrypted using the default CIPE encryption mechanism, then transferred over IP as UDP packets via its own virtual device (cipcbx) over a carrier network (such as the Internet) to an intended remote node.

CSU/DSU - For digital lines, a channel service unit (CSU) and a data service unit (DSU) are required. The two are often combined into a single piece of equipment, called the CSU/DSU. The CSU provides termination for the digital signal and ensures connection integrity through error correction and line monitoring. The DSU converts the T-carrier line frames into frames the LAN can interpret and vice versa. It also connects T-carrier lines with terminating equipment.

Data Link Connection Identifier (DLCI) - a channel number which is attached to frame relay data frames to tell the network how to route the data. A 10-bit field that defines the destination address of a packet. The address is local on a link-by-link basis.

Differentiated Services(DIFFServ) - a computer networking architecture that specifies a simple, scalable and coarse-grained mechanism for classifying, managing network traffic and providing quality of service (QoS) guarantees on modern IP networks.

Digital Signal 3 (DS3) - is a digital signal level 3 T-carrier. It may also be referred to as a T3 line.

Dynamic Routing - Routing algorithms designed to adjust to changing network circumstances by analyzing incoming routing update messages. If the message indicates that a network change has occurred, the routing software recalculates routes and sends out new routing update messages. These messages permeate the network, stimulating routers to rerun their algorithms and change their routing tables accordingly.

Dynamic Host Configuration Protocol (DHCP) - a set of rules used by communications devices such as a computer, router or network adapter to allow the device to requestand obtain an IP address from a server which has a list of addresses available for assignment.

E1 - E1 circuits are very common in most telephone exchanges and are used to connect to medium and large companies, to remote exchanges and in many cases between exchanges. E3 lines are used between exchanges, operators and/or countries, and have a transmission speed of 34.368 Mbit/s.

Firewall - a hardware or software device which is configured to permit, deny, or proxy data through a computer network which has different levels of trust. Standard security practices dictate a "default-deny" firewall ruleset, in which the only network connections which are allowed are the ones that have been explicitly allowed.

Frame Relay - consists of an efficient data transmission technique used to send digital information quickly and cheaply in a relay of frames to one or many destinations from one or many end-points. Network providers commonly implement frame relay for voice and data as an encapsulation technique, used between local area networks (LANs) over a wide area network (WAN). Each end-user gets a private line (or leased line) to a frame-relay node. The frame-relay network handles the transmission over a frequently-changing path transparent to all end-users.

Fully Qualified Domain Name (FQDN) - consists of a host and domain name, including top-level domain. For example, is a fully qualified domain name. www is the host, ImageStream is the second-level domain, is the top level domain.

High-Level Data Link Control (HDLC) - is now the basis for the framing mechanism used with the Point-to-Point Protocol on synchronous lines, as used by many servers to connect to a wide area network, most commonly the Internet. A mildly different version is also used as the control channel for E-carrier (E1) and SONET multichannel telephone lines.

ip address - An IP address (Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)-in simpler terms, a computer address. IP addresses are managed and created by the Internet Assigned Numbers Authority (IANA). The IANA generally allocates super-blocks to Regional Internet Registries, who in turn allocate smaller blocks to Internet service providers and enterprises.

Integrated Services Digital Network (ISDN) - is a circuit-switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds than that which is available with the PSTN system. More broadly, ISDN is a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the user.

iptables - iptables are a standard part of all modern Linux distributions from which the system administrator creates the rules for the packet filtering and NAT modules.

IP Tunnel - is the process of embedding one IP packet inside of another, for the purpose of simulating a physical connection between two remote networks across an intermediate network. IP tunnels are often used in conjunction with IPSec protocol to create a VPN between two or more remote networks across a "hostile" network such as the Internet.

International Telephone and Telegraph Consultative Committee (CCITT) - coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland.

Local Area Network (LAN) - a computer network covering a small geographic area, like a home, office, or group of buildings. The defining characteristics of LANs, in contrast to Wide area networks (WANs), include their much higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines.

Local Management Interface (LMI) - a signaling standard used between routers and frame relay switches. Communication takes place between a router and the first frame relay switch it's connected to. Information about keepalives, global addressing, IP Multicast and the status of virtual circuits is commonly exchanged using LMI.

Multilink PPP (MLPPP) - Multilink PPP can connect multiple links between two systems as needed to provide extra bandwidth. Remotely accessing resources through PPP Multilink allows for the increase in overall throughput by combining the bandwidth of two or more physical communication links such as analog modems, ISDN, and other analog/digital links.

Network Address Translation (NAT) - also known as Network Masquerading, Native Address Translation or IP Masquerading) involves re-writing the source and/or destination addresses of IP packets as they pass through a Router or firewall. Most systems using NAT do so in order to enable multiple hosts on a private network to access the Internet using a single public IP address (or gateway). Many network administrators find NAT a convenient technique and use it widely. Nonetheless, NAT can introduce complications in communication between hosts and may impact performance.

Open Shortest Path First (OSPF) - protocol is a hierarchical interior gateway protocol (IGP) for routing in Internet Protocol, using a link-state in the individual areas that make up the hierarchy to determine the "best path" routes.

Open Systems Interconnection Basic Reference Model (OSI reference model) - a layered, abstract description for communications and computer network protocol design, developed as part of Open Systems Interconnection (OSI) initiative. It is also called the OSI seven layer model. The layers, described below, are, from top to bottom, Application, Presentation, Session, Transport, Network, Data Link and Physical. Point-to-Point Protocol (PPP) - is commonly used to establish a direct connection between two nodes. It can connect computers using serial cable, phone line, trunk line, cellular telephone, specialized radio links, or fiber optic links. Most Internet service providers use PPP for customers' dial-up access to the Internet. Two common encapsulated forms of PPP are used in a similar role with Digital Subscriber Line (DSL) Internet service. These are:

  • Point-to-Point Protocol over Ethernet (PPPoE), and
  • Point-to-Point Protocol over ATM (PPPoA)

QoS - is a feature of routers and switches which prioritizes traffic so that more "important" traffic can pass first. The result is a performance improvement for critical network traffic. QoS equipment is useful with VoIP phones or in LANs with high volumes of local traffic.

QUAGGA - is a free software routing suite, providing implementations of OSPF (v2 & v3), RIP (v1, v2 & v3) and BGP (v4) for Unix platforms, particularly FreeBSD, GNU/Linux, Solaris and NetBSD. Quagga is a fork of the GNU Zebra project (inactive since 2003) which was developed by Kunihiro Ishiguro.

Remote Authentication Dial In User Service (Radius) - is an authentication, authorization and accounting (AAA) protocol for applications such as network access or IP mobility.

Request for Comments (RFC) - dDocuments that contain the protocols, standards, and information that define the Internet. These standards are gathered and published by the Internet Engineering Task force, a consensus-building body made up of institutions and corporations involved with online communications, they are preceded by RFC and followed by a number. RFC archives can be found Internet Network information Center (InterNIC)

Routing Information Protocol (RIP) - one of the most commonly used interior gateway protocol (IGP) routing protocols on internal networks, which help routers dynamically adapt to changes of network connections by communicating information about which networks each router can reach and how far away those networks are. safety extra-low voltage (SELV) circuits - The use of extra-low voltage (ELV) in an electrical circuit is one of several means to provide protection against electrical shock. Avoid hooking these circuits to telephone-network voltage (TNV) circuits as these are not compatable and can result in damage to your equipment.

Secured Shell (SSH) - Is a network protocol that allows data to be exchanged over a secure channel between two computers. Encryption provides confidentiality and integrity of data. SSH uses public-key cryptography to authenticate the remote computer and allow the remote computer to authenticate the user, if necessary.

Secured Sockets Layer (SSL) - are cryptographic protocols that provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers.

Service Profile identifier (SPID) - is a number issued by ISDN service providers in North America that identifies the services and features of an ISDN circuit. Service providers typically assign each B channel a unique SPID. A SPID is derived from the telephone number assigned to the circuit, and in the U.S. it typically follows a generic, 14-digit format.

Simple Network Protocol (SNMP) - a part of the internet protocol suite as defined by the Internet Engineering Task Force (IETF). SNMP is used by network management systems to monitor network-attached devices for conditions that warrant administrative attention. It consists of a set of standards for network management, including an Application Layer protocol, a database schema, and a set of data objects.

Synchronous Data Link Control (SDLC) - is a computer communications protocol. It is the layer 2 protocol for IBM's Systems Network Architecture (SNA). SDLC supports multipoint links as well as error correction. It also runs under the assumption that an SNA header is present after the SDLC header. It was the basis for the HDLC and ADCCP protocols, which added features such as the balanced response mode

telnet - A terminal emulation program for TCP/IP networks such as the Internet. The Telnet program runs on your computer and connects your PC to a server on the network. This enables you to control the server and communicate with other servers on the network.

Terminal Access Controller Access-Control System Plus (TACACS+) - protocol which provides access control for routers, network access servers and other networked computing devices via one or more centralized servers. TACACS+ provides separate authentication, authorization and accounting services.

Transmission Control Protocol (TCP/IP) - TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

T1 - is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and Korea. The basic unit of the T-carrier system is the DS0, which has a transmission rate of 64 kbit/s, and is commonly used for one voice circuit.

Vitual Channel Identifier (VCI) - a unique identifier which indicates a particular virtual circuit on a network. It is a 16-bit field in the header of an ATM cell. The VCI, together with the VPI (Virtual Path Identifier) is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination.

Virtual LAN (VLAN) - a method of creating independent logical networks within a physical network. Several VLANs can co-exist within such a network. This helps reduce the broadcast domain and aids in network administration by separating logical segments of a LAN (like company departments) that should not exchange data usinga LAN (they still can exchange data by routing).

Virtual Path Identifier (VPI) - refers to an 8-bit (user to network packets) or a 12-bit (network-network packets) field within the header of an Asynchronous Transfer Mode packet. The VPI, together with the VCI (Virtual Channel Identifier) is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination. VPI is useful to reduce the switching table for some Virtual Circuits which have common paths.

Virtual Router Redundancy Protocol (VRRP) - The Virtual Router Redundancy Protocol is designed to eliminate the single point of failure associated with statically routed networks by providing routing redundancy for specific IP addresses utilizing multiple LAN paths through alternate routers.

Voice Over Internet Protocal (VoIP) - refers to communications services — voice, fax, SMS, and/or voice-messaging applications — that are transported via the Internet, rather than the public switched telephone network (PSTN).

ide Area Network (WAN) - used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations.

Modem - is a simple file transfer protocol. XMODEM became extremely popular in the early bulletin board system (BBS) market, largely because it was so simple to implement. It was also fairly inefficient, and as modem speeds increased this problem led to the development of a number of modified versions of XMODEM to improve performance or address other problems with the protocol.

Modem - originally YMODEM was essentially the same as XMODEM except that it sent the file's name, size, and timestamp in a regular XMODEM block before actually transferring the file. Sending the file size solved XMODEM's problem of superfluous padding at the end of the file.

Modem - is a sophisticated file transfer protocol developed to improve file transfers. In addition to dramatically improved performance compared to older protocols, ZMODEM also offers restartable transfers, auto-start by the sender, an expanded 32-bit CRC, and control character quoting, allowing it to be used on networks that might "eat" control characters.

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