Glossary
			A Application Service Provider (ASP): Firms that offer a contractual service for deploying, and hosting managing packaged software from a central facility. B     top Back Bone: The part of a communications network that connects main nodes, central offices, or LANs. The backbone usually has its own high-speed protocol, such as switched token ring or FDDI for LAN interconnections, and SONET for central-office and main-node interconnections. Bandwidth: A measure of the communication capacity or data-transmigrate of a circuit. Bandwidth is the total frequency range, in H or cycles per second that is available to a channel or the arm of data that can be carried, in bits per second (bps), by a channel. Bandwidth Chart C     top Cabinet: An enclosed frame into which equipment is mounted. MeetMeRoom cabinets are available in full spaces that are suitable for networking and/or server colocation. The cabinet dimensions have enough space suitable for front mount ear flaps. Cable trays are included so customers can run cables between their cabinets. Colocation, Physical: A colocation is an interconnection agreement and a physical place where telephone companies hand-off calls and services to each other. This is usually done between a CLEC and an RBOC. The CLEC installs and maintains interconnection equipment usually consisting of optical carrier (SONET) equipment and a digital cross-connect system. There are other types of colocation. Alarm companies like to have their alarm signaling equipment located in the local central office for the security and convenience of connecting alarm circuits. Long-distance companies collocate with local telephone companies, as well. D     top Data Packet Switch: A device that routes packets of data to another data packet switch until the packet reaches the data packet switch that has access to the address contained in the overhead of the packet. It is also called a PSE (Packet Switching Exchange). Packet switching is a family of protocols for data communications. There are two basic innovations of packet switching. The first is to get away from having to send a huge amount of information at one time and the second is to enable multiple users to utilize the network connection at the same time. When using a modem to transfer a data file, the modem seizes the telephone line, dials a number, and starts ending information. This is very effective, but no one else can use the line, and there is a risk that the call could be disconnected, and all the data would have to be retransmitted (newer modem protocols can pick up where the disconnect occurred, but this is still inconvenient). The other need for improvement is the ability for more than one user to use the line at the same time. Packet switching is an excellent remedy for these concerns. The way that packet switching works is that large amounts of data to be transmitted are broken down into smaller pieces by a PAD (Packet Assembler/Dissembler), which can be a software program in an end-user's computer or a separate piece of hardware on the customer's premises. The PAD then gives each smaller piece of data an address and an identification number relative to the rest of the pieces. The pieces of data with their address, ID number, error-control information, and other HDLC (high-level digital link control) information are called packets. The important thing to know here is that each packet has its own address and identity relative to all the other packets of the broken-down file. The packets are then sent to a PSE (Packet-Switching Exchange) via a modem that is connected to a packet-switching exchange then makes copies of the packets, transmits the originals to another PSE that has access to the address contained in the overhead of the packet. A packet can travel through several PSEs before reaching the end PSE. When the packet is safely received by the end PSE, a receipt acknowledgment is sent to the originating PSE, at which time the copy is deleted (or flushed from memory). If any packet is received in other-than-perfect condition, the end PSE sends a request to the originating PSE to retransmit the packet. DS3 (Digital Service Level 3): 44.736Mb/s. A DS3 is a circuit that is provided to customers by telephone companies. It is a transport for 28 T1 circuits, which adds up to 672 DS0 circuits (voice channels). Telecommunications customers use DS3 circuits as private lines to connect data devices from one geographical place to another or to transport large amounts of dial tone to the premises. DS3 circuits are also used to connect directly to a long-distance company for broadband WAN service. Telecommunications companies also use DS3 circuits to provide more telephone service where a shortage of twisted pairs is in their cable plant. Sometimes it is less expensive for a telephone company to install the DS3 electronics in areas, rather than long feeds of large twisted copper-pair cables. DS4 (Digital Service Level 4) 274Mb/s. A DS4 is a transport for six DS3 circuits. Its capacity in DS1 circuits is 168. The capacity in DS0 circuits is 4032. F     top FM-200: FM-200 is an odorless, colorless, and liquefied compressed gas. FM-200 is stored as a liquid and dispensed into a hazard as a colorless, non-conductive vapor that will not obscure vision. It leaves residue and has acceptable toxicity for occupied spaces. IT suppresses fire by a combination of chemical and physical processes and does not displace oxygen-therefore there is danger of oxygen deprivation. G     top Gateway: A gateway is a demarcation point for different networks. International telecommunications are done through gateway central offices. Gateway central offices (class 1 central offices) connect communications to other countries. The gateway does the translation from T1 to E1, T3 to E3, and vise-versa. A gateway can also be a translating device on a smaller network as well. A smaller gateway would connect two different LAN networks of different protocols (e.g., Token Ring to Ethernet). I     top Interconnection: The connection of one telecommunication carrier to either another telecommunication company, an ISP or other telecommunication user via fiber optic or copper transmission lines. These connections typically take place in a colocation, data center or MeetMeRoom facility and allow the providers to utilize service on the carriers network. Colocation, data centers and MeetMeRooms simplify interconnection because multiple carriers are located within a close proximity of one another. Internet Exchanges (IX): A junction or "meeting point" for major Internet Service Providers to Exchange traffic across their networks. Internet Protocol (IP): Lowest level communications protocol upon which the Internet is based. IP enables a packet of information to travel through multiple networks to get to its ultimate destination. Internet Service Provider (ISP): A company that provides access to the Internet. AN ISP provides leased-line or dial-up access to the Internet end-users, generally at a monthly fee. ISPs must in turn purchase transit access to the larger Internet from a Network/National Service Provider (NSP) and/or peer with other ISPs. L     top Last Mile: the connection between the customer and the telephone company also referred to as "local loop". The last mile is a copper-based wire. Local Central Office (LSO): Local Serving Office. A central office that performs telecommunications switching for a specific number-plan area. The number-plan area is currently defined by the first three digits of a seven-digit telephone number. When a number portability takes effect, a local central office will no longer be defined as its number-plan area. It will be defined by the laws set forth by the PUC and the area its outside plant reaches. Typical switching systems installed in central offices in North America are Lucent Technologies' 5ESS and Northern Telecom's DMS family of switches. There are five classes of central offices and a local central office is a class five. There are five major parts to a central office. As a whole, these parts are referred to as inside plant. Local Loop: The lines between a customer and the telephone company’s central office, also referred to as the "last mile". Local loops use copper-based wire. M     top Mbps (Megabits Per Second): Equivalent to one million bits per second. Memory or data transferred per unit of time is measured in bits. Memory storage is measured in bytes. The difference in abbreviations is that bits are lowercase (b) and bytes are uppercase (B). Mega (M): The prefix for million. Sixteen megabytes is equal to 16,000,000 bytes, and would be abbreviated 16MB. Megabyte: One million bytes. Mega is abbreviated "M" and bytes are abbreviated "B". Sixteen megabytes is equal to 16,000,000 bytes and would be abbreviated 16MB. N     top Network Access Point (NAP): A junction point for major Internet Service Providers to interconnect with each other. Connection at one or more NAPs implies being connected to the greater Internet. -NAPs came into being when the Internet went commercial in 1995. At that point four official NAPs were created-3 were operated by telephone companies and based in Pennsauken, NJ, Chicago, and San Francisco and the fourth based in Washington DC and operated by Metropolitan Fiber Systems (MFS). The latter NAPs were in existence (two of them governmental) and four more MAEs were created, bringing the total to approximately 12 NAPs nationwide. P     top Packet: A unit of data in a transmission that contains payload (transmitted information) and overhead (addressing and error-correcting information). Packet-transmission techniques are used in different ways in frame relay, ATM, and Ethernet protocols. Patch Panel: A panel equipped with plugs, rather than terminals, for connecting wires or fiber optics. A patch panel can be used to terminate installed wire or be used as a "plug-in" test access point for communications circuits. DS0 and DS3 patch panels are very popular in central offices for testing purposes. Cat 5 patch panels are popular in computer LAN environments for the easy connection of computers to a network of pre-installed wire. Peering: A relationship whereby two autonomous networks exchange traffic, generally using the BGP protocol. Point of Presence: Point of presence is another term for demarcation or network interface. It is where the telephone company formally hands-off their services to a customer. Wire and equipment on the phone company side of the demarcation belongs to the phone company. Wire and equipment on the customer side of the demarcation belongs to the customer. Every building and home has a network interface. It is against the law (federal) to not have one. Private Peering: Partly due to congestion at Network Access Points (NAPS), many ISPs formed private agreements with each other to interconnect directly via dedicated circuits. R     top Rack: A frame or a cabinet without doors and sides, typically found in a collation area or a MeetMeRoom. Redundancy: Commonly known as "N+1 Redundancy" and is designed into all Carrier Centers and MeetMeRooms. We offer the ability of a system to continue non-stop when a failure occurs. A redundant system is usually designed from the ground up for reliability by building multiples of critical components. In the event that a component fails, another takes over without disruption. Raised Floor: Many computer and telecommunications rooms have a raised floor. The raised floor is a very sturdy framework of iron, with heavy 1" tiles placed into the framework. The tiles are easily removed and replaced with a suction cup. The raised floor is used as a giant "duct" to move and run connecting cables through, and it is also used as an airway to pump cool air through the equipment. Instead of cooling a room, cool air is blown under the floor, where it finds its way into the equipment through holes in the floor. The holes are cut into the floor when the equipment is installed. S     top SONET (Synchronous Optical Network): SONET is strictly a broadband transport system. It is implemented over fiber optic and is able to be configured in a ring, which allows it to reroute traffic with no interruption of service if a fiber is cut. CLECs are implementing SONET as the mainstay of their network construction. SONET is based on a hierarchy of STS (Synchronous Transport Signals), which is the electrical version of an OC-1 (Optical Carrier Level 1). An OC 1 has a transmission speed of 51.84 Mb/s. The hierarchy of telephone communications services and their speeds is shown in the table. SONET works similar to switched token ring, except at much higher speeds. SONET permits a virtual tributary to be created from one node to another on a network. Virtual tributaries can be equal to a DS1, DS3, STS-1, or any of the OC levels. The important thing to know about a SONET network is that it simply replaces the older telecommunications technology copper twisted-pair outside plant with fiber optic and electronics. Splice: The connecting of two wires, cables, coax cables, or cable pairs together. A splice is shown on an engineering diagram as an arrow. The actual splices of twisted-pair telephone cable are done with modular-type splices, plain B wire connectors, or 3M Scotchloks. Fiber-optic cable is spliced via mechanical or fusion splicing, and coaxial cable is spliced with barrel connectors. U     top UPS: Acronym for Uninterruptible Power Supply. A device designed to supply power in the event of temporary or permanent loss of AC line power. Often these supplies will operate with either an AC line input or DC battery backup input. W     Top Wavelength Division Multiplexing (WDM): A way of increasing a fiber optic's capacity by using multiple colors of light. Each color of light has its own wavelength (and its own frequency). The electronic equipment on each end of the fiber can distinguish the different signals by their color (frequency/wavelength). In most applications today, each fiber optic in a communications network carries on light signal that is one pure color. In the future, fiber optic will be wavelength-division multiplexed to carry many transmission signals.
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