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Broadband Terminology  

Broadband Terminology
 
Q: What is a POTS Splitter?
A: A POTS splitter is the alternative setup for DSL and Voice in the same premise. It sits at the NID, or entry point of the line to the premise, and splits off the data portion of the signal so that it can be run cleanly through the house. Generally, splitters support full rate ADSL if available, whereas filters limit top speed to a megabit or so.
 
Q: What is a Y-Adapter?
A: Where a socket needs to provide both voice and DSL, a Y-Adapter can be used. Exactly as it sounds, this simply splits the socket into two, so that one can have a filter and a phone attached, and the other goes to the DSL modem.
 
Q: Bridge Tap?
A: Bridged tap or bridge tap is a long-used method of cabling for telephone lines. One cable pair (of wires) will "appear" in several different terminal locations (poles or pedestals). This allows the telephone company to use or "assign" that pair to any subscriber near those terminal locations. Once that customer disconnects, that pair becomes usable at any of the terminals. In the days of party lines 2, 4, 6, or 8 customers were commonly connected on the same pair which appeared at several different locations.
 
DSL can be affected by bridged tap. It depends on where the bridged tap is located ... the farther away from the customer's location, the better.
 
DSL signal reflects back through the cable pair from the end of a bridged tap, much like a tennis ball against a brick wall. The deflected signal is now out of phase and mixed with the original. The modem receives both signals and gets confused. This is when you "take errors" or cannot sync. If the bridged tap is long, by the time the signal bounces back, the original signal is far ahead and more powerful. Therefore, the modem will ignore the weaker signal and shows no problems.
 
Almost every cable pair in the world has bridged tap on it, so it definitely isn't always a DSL killer.
 
Q: BPS (Bits Per Second)?
A: In data communications, bits per second (abbreviated bps) is a common measure of data speed for computer modem and transmission carriers. As the term implies, the speed in bps is equal to the number of bits transmitted or received each second. The bandwidth of a signal depends on the speed in bps.
 
Q: CAP and DMT?
A: CAP and DMT are two different "flavors" of DSL. CAP uses two channels to connect and DMT uses 256 channels to connect, giving it a greater connection range and making it easier for it to adapt to certain line issues.
 
Q: CIR (Committed Information Rate)?
A: In frame relay networks, a committed information rate (CIR) is a bandwidth (expressed in bits per second) associated with a logical connection in a permanent virtual circuit (PVC). Frame relay networks are digital networks in which different logical connections share the same physical path and some logical connections are given higher bandwidths than others. Because the CIR is defined in software, the network's mix of traffic bandwidths can be redefined in a relatively short amount of time.
 
Q: CLEC?
A: Pronounced see-lek. A Competitive Local Exchange Carrier is a telephone company that competes with an Incumbent Local Exchange Carrier (ILEC).
With the passage of the Telecommunications Act of 1996, there has been an explosion in the number of CLECs. The Act allows companies with CLEC status to use ILEC infrastructure.
 
Q: CPE?
A: Customer Premise Equipment. This is the router or DSL modem that connects your PC, to your DSL line. The CPE is usually bundled with your DSL line. CPE may require (but not include) a NIC. (Network Interface Card).
 
Q: DSLAM?
A: A Digital Subscriber Line Access Multiplexer (DSLAM) is a network device, usually at a telephone company central office, that receives signals from multiple customer Digital Subscriber Line (DSL) connections and puts the signals on a high-speed backbone line using multiplexing techniques. Depending on the product, DSLAM multiplexers connect DSL lines with some combination of asynchronous transfer mode (ATM), frame relay, or IP networks. DSLAM enables a phone company to offer business or homes users the fastest phone line technology (DSL) with the fastest backbone network technology (ATM). Also check: »webopedia.internet.com/TERM/D/DSLAM.html
 
Q: DNS (Domain Name System)?
A: The domain name system (DNS) is the way that Internet domain names are located and translated into Internet Protocol addresses. A domain name is a meaningful and easy-to-remember "handle" for an Internet address.
 
Q: Download? Upload?
A: Download is the process of information coming from someplace else to you. When you browse to a web page, you are "downloading" that page. When you get a file from some place on the internet, you are downloading that file.
Upload is the process of sending information from your computer onto the internet. The most common upload for most users is the simple request to "download" a new web page.
 
Q: Drop?
A: Historically, the wire that "drops" from a Telco pole. For DSL, the terminal point of the DSL line outside the building or premise.
 
Q: F1 pair?
A: Often a CLEC reports the ILEC has 'facilities' issues and cannot provide an F1 pair to the CLEC. F1 (first facility) pairs refer to the usually buried pair bundles which go from the Central Office to the Cross Box. F2 cables (second facility) are the ones usually aerial, that leave cross boxes.
 
Q: Filters?
A: A distributed filter, or micro-filter, is a small electronic component that fits between your phone line and a regular voice device, such as a phone, a fax, or any device with a regular modem such as a cable box, alarm system or digital TV.
When DSL (ADSL) is provided over voice lines, all devices in the house except the DSL modem must be connected through filters. The filter protects the phone devices from high frequency noise. They are low-pass filters. The filter is also there to protect the DSL signal from being contaminated by high frequency noise added by analog phone devices, answering machines, etc.
 
Q: FOC date?
A: Firm Order Commitment. The date at which outside wiring is scheduled (and the order becomes "real"). The normal procedure for a DCLEC DSL install, is for the Telco to schedule a FOC date to your MPOE (minimum point of entry). The ISP should advise you of your FOC date, (if one is required), as you may have to be there to let them have access.
 
Q: Fractional T1 / T3?
A: A fractional T-1 or T-3 line is a T-1 or T-3 digital phone line in the North American T-carrier system that is leased to a customer at a fraction of its data-carrying capacity and at a correspondingly lower cost. A T-1 line contains 24 channels, each with a data transfer capacity of 64 Kbps. The customer can rent some number of the 24 channels. The transmission method and speed of transfer remain the same.
 

Variable-length packets
 
Statistical multiplexing
 
Variable-length packets are used for more efficient and flexible data transfers. These packets are switched between the various segments in the network until the destination is reached.
 
Statistical multiplexing techniques control network access in a packet-switched network. The advantage of this technique is that it accommodates more flexibility and more efficient use of bandwidth. Most of today's popular LANs, such as Ethernet and Token Ring, are packet-switched networks.
 
Q: FTP?
A: FTP - File Transfer Protocol
A method of server and obtaining files to and from the internet. Common FTP software include CuteFTP and WSFTP.
 
Q: ILEC
A: Pronounced eye-lek. Short for incumbent local exchange carrier. An ILEC is a telephone company that was providing local service when the Telecommunications Act of 1996 was enacted. For example: GTE, SWB, AT&T.
 
Q: IMAP (Internet Message Access Protocol)?
A: Internet Message Access Protocol (IMAP) is a standard protocol for accessing e-mail from your local server. IMAP (the latest version is IMAP4) is a client/server protocol in which e-mail is received and held for you by your Internet server. IMAP requires continual access to the server during the time that you are working with your mail.
 
Q: Kbps (Kilobits Per Second)?
A: Kbps stands for kilobits per second (thousands of bits per second) and is a measure of bandwidth (the amount of data that can flow in a given time) on a data transmission medium.
Higher bandwidths are more conveniently expressed in megabits per second (Mbps, or millions of bits per second) and in gigabits per second (Gbps, or billions of bits per second).
 
Q: LAN?
A: LAN stands for "local area network" & is a group of computers and associated devices that share a common communications line or wireless link and typically share the resources of a single processor or server within a small geographic area (for example, within an office building).
Usually, the server has applications and data storage that are shared in common by multiple computer users. A local area network may serve as few as two or three users (for example, in a home network) or many as thousands of users.
 
Q: LATA?
A: LATA (local access and transport area) is a term in the U.S. for a geographic area covered by one or more local telephone companies, which are legally referred to as local exchange carriers (LECs).
 
A connection between two local exchanges within the LATA is referred to as intraLATA. A connection between a carrier in one LATA to a carrier in another LATA is referred to as interLATA.
 
InterLATA is long-distance service.
 
Q: Latency?
A: One of the most commonly misunderstood concepts in networking is speed and capacity. Most people believe that capacity and speed are the same thing. For example, it's common to hear "How fast is your connection?" Invariably, the answer will be "640K", "1.5M" or something similar. These answers are actually referring to the bandwidth or capacity of the service, not speed.
 
Speed (latency) and capacity (bandwidth) are two very separate things. The combination of latency and bandwidth gives users the perception of how quickly a webpage loads or a file is transferred. It doesn't help that broadband providers keep saying "get high speed access" when they probably should be saying "get high capacity access". Notice the term "Broadband" - it refers to how wide the pipe is, not how fast.
 
Latency:
Here's the most common example to compare latency and bandwidth:
Imagine water running through a pipe. The pressure is latency, the width of the pipe is bandwidth. If you have a wide pipe but low pressure, you can move more water through the pipe but at a slower rate. If you have a narrow pipe but high pressure, you can move less water but at a faster rate.
 
Another example that is sometimes given:
Imagine people in an aircraft. In this example, people are the data packets, the size of the aircraft is the bandwidth, and the speed of the aircraft is the latency. A 747 can carry about 400 people but a 707 can carry only 200 people. Both fly at about 500 knots. If both leave New York at the same time, they will arrive in Los Angeles at the same time. But notice that although the 747 has more capacity (or bandwidth) it is the same speed (latency) as the 707.
 
Latency is normally expressed in milliseconds. One of the most common methods to measure latency is the utility ping. A small packet of data, typically 32 bytes, is sent to a host and the RTT (round-trip time, time it takes for the packet to leave the source host, travel to the destination host and return back to the source host) is measured.
 
The following are typical latencies as reported by others of popular circuits type to the first hop. Please remember however that latency on the Internet is also effected by routing that an ISP may perform (ie, if your data packet has to travel further, latencies increase).
 
Ethernet                      .3ms
Analog Modem             100-200ms
ISDN                           15-30ms
DSL/Cable                   10-20ms
Stationary Satellite      >500ms, mostly due to high orbital elevation
DS1/T1                        2-5ms
 
Bandwidth:
Bandwidth is normally expressed in bits per second. It's the amount of data that can be transferred during a second.
 
Solving bandwidth is easier than solving latency. To solve bandwidth, more pipes are added. For example, in early analog modems it was possible to increase bandwidth by bonding two or more modems. In fact, ISDN achieves 128K of bandwidth by bonding two 64K channels using a datalink protocol called multilink-ppp.
 
Bandwidth and latency are connected. If the bandwidth is saturated then congestion occurs and latency is increased. However, if the bandwidth of a circuit is not at peak, the latency will not decrease. Bandwidth can always be increased but latency cannot be decreased. Latency is the function of the electrical characteristics of the circuit.
 
Q: Line Tap Splitters (DC taps)?
A: DC Taps are special types of splitters that lose a ton of signal on one leg, but very little on another. The model number generally determines how great the larger loss number is.
For example:
 
DC-4 Tap: Loses 4db on one leg, around 1db on the other.
DC-6 Tap: Loses 6db on one leg, around 1db on the other.
DC-9 Tap: Loses 9db on one leg, around 1db on the other.
These splitters have one leg labeled "tap", and the other "out". The "tap" leg is the one with a large amount of loss.
 
Q: Load Coils?
A: Loading coils are used to extend the range of a local loop for voice applications. They are inductors added in series with the phone line which compensate for the parallel capacitance of the line.
 
They benefit the frequencies in the high end of the voice spectrum at the expense of the frequencies above 3.6 kHz.
 
Thus, loading coils significantly distort xDSL frequencies and must be removed for any DSL operation. They are often found at loops extending farther than 12,000 ft.
 
Q: Local Loop?
A: In Telco, a local loop is the wired connection from a telephone company's CO (central office) in a locality to it's customers' telephones at homes and businesses.
 
This connection is usually on a pair of copper wires called twisted pair. The system was originally designed for voice transmission only using analog transmission technology on a single voice channel. Today, your computer's modem makes the conversion between analog signals and digital signals.
 
With Integrated Services Digital Network (ISDN) or Digital Subscriber Line (DSL), the local loop can carry digital signals directly and at a much higher bandwidth than they do for voice only.
 
Q: Mbps?
A: Mbps stands for "megabits per second" and is a measure of bandwidth on a telecommunications medium. Depending on the medium and the transmission method, bandwidth is sometimes measured in the Kbps (thousands of bits or kilobits per second) range or the Gbps (billions of bits or gigabits per second) range.
 
Q: MPOE?
A: MPOE (Main Point of Entry)
 
Local Carriers are responsible for bringing lines to the Main Point Of Entry (MPOE) for multi-dwelling business, high-rise, and apartment buildings. If the line is brought to the MPOE by the local carrier (ILEC - Incumbent Local Exchange Carrier), the CLEC (Competitive Local Exchange Carrier) is responsible for finding and wiring an available pair from the MPOE to the Customer Premise Equipment (CPE, AKA Router) location.
 
MPOE's are also referred to as NIDs and DMARCs.
 
Q: Noise Margin?
A: Noise may be defined as the combination of unwanted interfering signal sources whether it comes from crosstalk, radio frequency interference, distortion, or random signals created by thermal energy. Noise impairs the detection of the smallest analog levels which may be resolved within the demodulator. The noise level along with the maximum clip level of an analog signal path set the available amplitude dynamic range.
 
The maximum data rate of a modem is limited by the available frequency range (bandwidth) and signal-to-noise ratio (SNR) which is amplitude dynamic range. If more of either is available, more bits may be transferred per second. In an audio analogy, the better (higher) the signal-to-noise ratio is, the easier it is to 'hear' the desired signal above the noise. The same principle applies here. The better the margin (the difference between the signal and the noise) the easier it is for your modem to pick out the DSL signal from the background noise.
 
Q: Ping?
A: PING: A protocol (command) that sends a message (packet) to another computer and waits for acknowledgment, often used to check if another computer (host) on a network is reachable.
 
It has been said that PING stands for "Packet INternet Groper"
 
Q: POTS?
A: POTS stands for Plain Old Telephone Service.
Is sometimes used in talking about Upgrading/Testing your POTS line to support DSL.
 
Q: PPPoE? PPPoA?
A: Point To Point Protocol over Ethernet and Point To Point Protocol over ATM
These are different VC Encapsulations. They differ in some ways (the most important is that PPPoA allows for MTUs of 1500), but there is mostly no difference in speed between the two.
 
PPPoE (PPP over Ethernet):
Another dial-up type connection method. PPPoE client software is from NTS (or various unsupported alternatives). The icon is typically located in a NTS EnterNet 300 folder. (As of EnterNet 1.34, integration with DUN is also possible.) Username, password and then connect as with PPPoA. Note that an additional layer of software is involved here.
PPPoE/A Connectivity
All new installations are now PPP. This can be either PPPoE (PPP over Ethernet) or PPPoA (PPP over ATM), two similar yet different protocols. Both use a mechanism similar to a dialup style connection: username and password are required. The server passes a (dynamic) IP address, netmask and other networking details back to the client once authentication has been successful.
The main difference is that with PPPoA, most of the work is done at the hardware level. So a modem that supports PPPoA is required. The Efficient 3060 and 4060 modems both support PPPoA (the Alcatel 1000/STH does not). The appropriate driver then needs to be loaded. The default connection method is via Windows DUN. A separate client ala NTS EnterNet is not required. DSL runs over ATM from the DSLAM to the modem no matter what modem we use. So this would seem to be the 'cleanest' solution for PPP customers.
PPPoE works via the 1483 Bridged driver, and requires client software to manage the session. This means that PPPoE is the only choice for Alcatel 1000/STH modem owners, and also IFITL customers. PPPoE, by requiring client software, also means there is more overhead due to the additional Ethernet layer. And consequently more system resources are used to maintain the connection. This may not be significant depending on your hardware and horsepower.
One of the drawbacks of the current PPP implementations is occasional disconnects. Apparently, the protocols are sensitive to any hiccup in the connection. One consequence here is that your IP address will change each time the connection is re-established. So why PPP? Aren't we trying to get away from dialup type connections?
Well, the answer from any ISP on this is that PPP simplifies a number of things on their end. They can essentially use their same infrastructure as their already well established, and much larger, dialup base. Simpler, means easier, means less costly. In any case, it is here to stay.
 



Q: PSTN
A: Short for Public Switched Telephone Network, which refers to the international telephone system based on copper wires carrying analog voice data. This is in contrast to newer telephone networks base on digital technologies, such as ISDN and FDDI.
 
Telephone service carried by the PSTN is often called plain old telephone service (POTS).
 
Q: PVC’s - Permanent Virtual Circuits?
A: Permanent virtual circuits (PVC's) are permanently established connections that are used for frequent and consistent data transfers between DTE devices across the Frame Relay network. Communication across a PVC does not require the call setup and termination states that are used with SVCs. PVCs always operate in one of the following two operational states:
 
Data transfer—Data is transmitted between the DTE devices over the virtual circuit.
 
Idle—the connection between DTE devices is active, but no data is transferred. Unlike SVC's (Switched Virtual Circuits), PVC's will not be terminated under any circumstances when in an idle state.
 
Q: QoS?
A: QoS stands for "Quality of Service" & is the idea that transmission rates, error rates, and other characteristics can be measured, improved, and, to some extent, guaranteed in advance.
 
QoS is of particular concern for the continuous transmission of high-bandwidth video and multimedia information.
 
Q: Remote DSLAM?
A: A Remote DSLAM is an extension of the DSLAM in your CO (Central Office). It acts like an amplifier, in a sense. So, the same copper loop length restrictions apply to that Remote..(depending on the gauge of wire within the facilities).the service envelope from that remote would be 18kft out (24 gauge wire) or 15.5kft out (26 gauge wire)
 
Q: Repeater?
A: In telecommunication networks, a repeater is a device that receives a signal on an electromagnetic or optical transmission medium, amplifies the signal, and then retransmits it along the next leg of the medium.
 
A series of repeaters make possible the extension of a signal over a distance. Repeaters are used to interconnect segments in a local area network (LAN).
 
Q: RT (Remote Terminal)?
A: A Remote Terminal (RT) is fiber fed extension of the central office bringing the capabilities of the central office closer to customers. The remote terminals use next-generation digital loop carriers (Litespan, SLC, Urban, and Optera) to provide high-speed data services and traditional telephone service to additional customers, typically those who live farther than a two or three-mile radius of a central office. Remote terminals take many forms including Cabinets, CEV's and Hut's. One example of widespread deployment of RTs is SBC's Project Pronto.
 
Q: SMDS (Switched Multimegabit Data Service) ?
A: SMDS is a high-speed, packet-switched, datagram-based WAN networking technology used for communication over public data networks (PDNs). SMDS can use fiber or copper-based media.
 
It supports speeds of 1.544 Mbps over Digital Signal level 1 (DS-1) transmission facilities, or 44.736 Mbps over Digital Signal level 3 (DS-3) transmission facilities.
 
In addition, SMDS data units are large enough to encapsulate entire IEEE 802.3, IEEE 802.5, and Fiber Distributed Data Interface (FDDI) frames.
 
Q: Sync?
A: The vast majority (possibly all) DSL lines are rated at their sync rate. Since DSL runs over atm/frame relay, it is very important that your DSL modem or router and the DSLAM (the device that takes data from your modem and transmits it onto your ISP's network and vice versa) use a common frame size and frame rate. Your sync rate is only really affected by one thing: Packet loss. DSL companies in 99.9% of cases guarantee only the sync rate on residential lines. This is also why providers will never give you the maximum amount of speed you can theoretically receive. Since there are really no factors that affect sync rate on a regular basis they can do this.
 
The reason you never achieve your sync rate is because of latency and the internet. Once the signal is off of your local Telco line, then it is affected by MANY MANY other things. There have been many good descriptions of how latency and the internet work. If you want more information, then check this out.
 
Q: TLS (Transport Layer Security)?
A: The TLS protocol provides communications privacy over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery.
 
Q: Training the line?
A: Training the line comes from the days of analog modem connections. Remember the long sequence of hisses, beeps, and just some other plain weird sounds after the dialing of the modem?
 
Training the line means to negotiate the best possible speed on the line. Sometimes, line noise can interfere with normal DSL line traffic, so, the modem must negotiate the best possible speed despite the noise.
 
With the noise, the best speed can't be offered, so, it throttles the speed back through a negotiation sequence so that you can get the best speed and connection stability despite the noise.
 
Q: Trouble Ticket?
A: A trouble ticket is an official complaint to the Tech Support department because standard troubleshooting via the phone or e-mail has not corrected the problem.
 
Once the Tech Support representative has exhausted all the things they can do by just talking, they submit a "trouble ticket" to someone who has more resources to correct the problem like Telco.
 
Once a trouble ticket is inserted in the pool, it must wait for an engineer to open the complaint. Once the ticket is open, the engineer then diagnoses the problem, and then checks all the ISP's settings, hardware, etc. that could relate to the issue. Once something has been discovered or done, the engineer makes a note into the ticket.
 
The note in the ticket is a comment from the engineer that states what he has found and what could be done to solve the issue (if not solved already).
At this point, the ticket is closed. Usually the ISP contacts the customer stating the results of the trouble ticket and asks for confirmation that the problem has been corrected. If the issue has been resolved, it's archived into your account details. If it hasn't, either the ticket goes back into the pool to re-check or a Telco tech is dispatched to your location to check the physical end of the customer's side. Once the tech reports after the session has been completed, the ticket is then closed and everyone is happy again.
 
Q: Upstream Signal to Noise Ratio
A: This basically shows how much signal the HEAD END is getting compared to noise. The higher this number is the better. As this number goes down, it means there is more and more noise in the line.
 
Usually this is caused by bad shielding, R59 cabling, or bad connectors/wall plates. It's not easy to determine the location of interference.
 
Upstream interference means that the head end is getting a lot of noise around the frequency that your cable modem broadcasts at (15 to 50 MHz). Troubleshoot this just like you would "fuzzy LOW channels".
 
Q: VPN (Virtual Private Network)?
A: A virtual private network (VPN) is a way to use a public telecommunication infrastructure, such as the Internet, to provide remote offices or inDIVidual users with secure access to their organization's network. A virtual private network can be contrasted with an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same capabilities, but at a much lower cost.
 
A VPN works by using the shared public infrastructure while maintaining privacy through security procedures and tunneling protocols such as the Layer Two Tunneling Protocol (L2TP). In effect, the protocols, by encrypting data at the sending end and decrypting it at the receiving end, send the data through a "tunnel" that cannot be "entered" by data that is not properly encrypted. An additional level of security involves encrypting not only the data, but also the originating and receiving network addresses




 

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