I’m Sourav Khanna. Today we are going to be talking about the public switched telephone network. Then I’m going to move on to the broadband cable. And I’m going to conclude with a brief section on fiber optics. And with that, let’s go ahead and begin this session. Of course, we begin with the public switched telephone network. Before I begin with the public switched telephone network, let’s talk about what makes a win a win as opposed to a LAN. Well, as a general rule, if you own and control the line that the data is using to get from one place to another, you are not using a wide area network or when technology. On the other hand, if you are using a form of transmission that you don’t own, as in your leasing a line or you’re paying for the use of it, then you are likely using when technology.
One of the most common physical infrastructures used in wind technology is the public switched telephone network, the PSTN due to its widespread availability, just about everybody has a telephone line being run to their house or to their building. An older technology but still somewhat valid today for when technology is dial up. No dial up utilizes the PSTN to transmit network traffic as an analog signal. Dial up does require an analog modem to format the network traffic correctly so it can be transmitted. You’re maximum theoretical speed on dial up is 56 kilobits per second. It’s not very fast. Then there’s ISDN integrated service.
What are Integrated Services Digital Network?
Digital Network ISDN is a digital point to point when technology that utilizes the PSTN. It’s a completely digital service, it requires the use of a terminal adapter or ta to make the connection to the end nodes. This ta is often called a digital modem, but it’s not it’s a terminal adapter ISDN can use a primary rate interface or PRI. Now the PRI is composed of 2364 kilobit per second B channels and once 64 kilobit per second D channel that D channel is used for call setup in link management. A PRI can achieve 1.544 megabits per second speed, and that is commonly referred to as a T one leased line. The most commonly implemented form of an ISDN though is the BRI the basic rate interface, it uses only two B channels and one D channel, and the BRI can achieve speeds of up to 128 kilobits per second. Now ISDN is not as capable as a digital subscriber line or DSL, but it can often be implemented where DSL cannot be installed. Speaking about DSL, let’s move on to it. Xx DSL is the term for generic DSL.
What is DSL? Digital Subscriber Line
DSL is a digital wind technology that utilizes the PSTN DSL does require the use of a digital modem. It uses a dedicated digital line between the endpoint in a class five central office or CEO. Now in order for the most basic forms of DSL to be installed, you have to be within 18,000 feet of the CEO. DSL is capable of carrying voice and data. When it does carry both filters are put in place in order for the voice signal to come through without any interference. Now let’s move on to the different types of DSL. In First up is symmetric DSL or sdsl. Symmetric DSL is synchronous in nature. That means that the upload and download speeds are the same as DSL does not carry voice communication. So if you need voice service, an additional line is going to be needed. As DSL is used by businesses that don’t quite need the performance of a T one leased line, but they do require the symmetrical upload and download speeds. More common than sdsl is ADSL or asymmetric DSL, it’s asynchronous in nature. That means that the upload speed is slower than the download speed.
What is ASDL? Asymmetric Digital Subscriber Line
ADSL can carry data and voice common upload speeds for ADSL are 768 kilobits per second, with download speeds of up to nine megabits per second. It is the most common implementation of DSL, in the small office home office environment. Last up for DSL is VDSL are very high bitrate DSL, it’s asynchronous in nature as well. It’s used when high quality video in Voice over IP is necessary. VDSL is commonly limited to download speeds of 52 megabits per second with an upload speed of 12 megabits per second. That’s a whole lot faster than ADSL. But VDSL is only possible when you’re located within 4000 feet of a central office. There is an exception to what I just told you though, the current standards do allow for up to 100 megabits per second speed over the PSTN using VDSL. But in order to achieve that, you must be within 300 meters of the central office.
Now that the PSTN is out of the way, let’s move on to broadband cable. Broadband cable is coaxial cable networking. It’s a broadband connection to a location delivered by the cable company. Broadband cable can deliver voice data and television all through the same connection. And the way it works is the digital signal is delivered to the head and this is where all the cable signals are received. The signal is then processed in format added and then transmitted to the distribution network. The distribution network is a smaller service area served by the cable company. The distribution network architecture can be composed of fiber optic cabling, or coaxial cabling, and or a hybrid fiber coaxial cabling or HFC. Unlike DSL, the bandwidth of the distribution network is shared by all of those who connect to it. This can lead to increase latency in congestion during busy times. The final distribution to the premise is usually through a coaxial cable. The other thing that you need to know about broadband cable is that all cable modems and similar devices must measure up to the ISP is required data over cable service interface specifications or DOCSIS specification. If it doesn’t measure up, you’re not going to achieve the speeds that you expect. Now let’s conclude with fiber.
Fiber Optic Networking
Fiber Optic networking is using light to transmit data and voice. This allows for more bandwidth over greater distances. Fiber Optic networking is more expensive to install, but it’s also less susceptible to line noise. The fiber synchronous data transmission standard in the United States is called the synchronous optical network or sonnet standard. The international standard is called the synchronous digital hierarchy are SDH. Both sonet and SDH defined the base rates of transmission over fiber optic cabling, which are known as optical carrier levels. Dense wavelength division multiplexing is a method of multiplexing several optical carrier levels together, up to 32 of them into a single fiber optic cable, effectively increasing the bandwidth of that single optical fiber. Instead of dw dm you could use CW dm, course wavelength division multiplexing. It’s similar to dw dm, but it only allows for up to eight channels on a single fiber. When fiber optic is delivered to the premise, it’s usually delivered over a passive optical network or upon upon is a point to multipoint technology that uses a single optical fiber that used to connect multiple locations to the internet. The passive optical network uses unpowered optical splitters. Now that concludes this session on wind technologies. Part One, I talked about the public switched telephone network. Then we moved on to broadband cable, and I briefly ran through fiber optic networking.
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