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Comparison of line speeds

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A Local Area Network (LAN) supplies networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. A LAN is useful for sharing resources like files, printers, games or other applications. A LAN in turn often connects to other LANs, and to the Internet or other WANs (Wide Area Networks).

Most local area networks are built with relatively inexpensive hardware such as Ethernet cables, network adapters, and hubs. Ethernet operates at 10 Mbps and Fast Ethernet LAN operates at 100 Mbps. Wireless LAN speed on most wireless networks is typically slower than wired LANs operating at 1-108 Mbps (very few are able to handle 100 Mbps). There are other more advanced LAN hardware options but they are not typically found in “home” use or “small business” use.


Digital Subscriber Line service is usually offered at several pricing tiers with speeds ranging from 512 Kbps to 8 Mbps (faster is more expensive).

The advantages of DSL:

·You can leave your Internet connection open and still use the phone line for voice calls.

The speed is much higher than a regular modem

DSL doesn't necessarily require new wiring; it can use the phone line you already have.

The company that offers DSL will usually provide the modem as part of the installation.

The disadvantages:

A DSL connection works better when you are closer to the provider's central office.

The connection is faster for receiving data than it is for sending data over the Internet.

The service is not available everywhere.

T1 – T4:

T1 is a high speed digital network (1.544 mbps) developed by AT&T in 1957 and implemented in the early 1960's to support long-haul pulse-code modulation (PCM) voice transmission. The primary innovation of T1 was to introduce "digitized" voice and to create a network fully capable of digitally representing what was up until then, a fully analog telephone system.

T1 is a "two-point”, dedicated, high capacity, digital service provided on terrestrial digital facilities capable of transmitting 1.544 Mb/s. The interface to the customer can be either a T1 carrier or a higher order multiplexed facility such as those used to provide access from fiber optic and radio systems.

So T1 is a network that has a speed of 1.544 Mbps and was designed for voice circuits. In addition, there is T1-C which operates at 3.152 Mbps. There is also T-2, operating at 6.312 Mbps.

There is also T-3, operating at 44.736 Mbps and T-4, operating at 274.176 Mbps. These are known as "super groups" and their operating speeds are generally referred to as 45 Mbps and 274 Mbps respectively. T1 pricing starts around $360/month and T2 through T4 are not an option for a home or small business operation (unless your pockets are unusually deep).

T1 vs T3 Lines

The digital capacity of a plain old telephone service (POTS) line is 64 Kbs. There are 8000 timing bits added, so the actual throughput is 56 Kbps. This is enough to carry a single voice call or to connect a 56 Kbs modem. The POTS line is an analog line; it transmits and receives analog or sound-based signals.

A T1 line is a pure digital line. Conversations are converted (at a PBX) from analog (sound) to digital before being transmitted on the T1 line.

The T1 line can handle 24 simultaneous voice calls. (24 simultaneous voice calls can satisfy anywhere from 24 to well over 100 office workers, depending on their calling patterns.)

Sometimes one of the 24 lines is dedicated to caller ID; this line is usually connected to a computer that looks up customer records that are routed to the computer of the person taking the call.

A T1 line can handle a high speed Internet connection speed of 1.544 Mbps.

Or, as an integrated service it can handle a combination of fewer voice calls with some bandwidth given to Internet connections.

A T3 line is also a pure digital line. It is the equivalent of 28 T1 lines or 672 POTS lines.

A T3 line can handle 672 simultaneous voice calls or provide a high speed Internet connection of 44.736 Mbps. As an integrated service, it can handle a combination of fewer voice calls and provide high speed Internet connections. The T3 is typically used by high end data and voice customers.

Monthly costs for T1 and T3 lines vary, primarily depending on the distance from your local phone company's Customer Office. As a very rough comparison we can say a T1 might cost $500 per month while a T3 might cost $4,000 per month.

High Speed Internet:

High Speed Internet can be provided over fiber optic (optical carrier) lines or by “cable” (coaxial cable). Modems using coaxial cable are limited to 512 Kbps to 52 Mbps. The upper limit of 52 Mbps on a cable is to an ISP, not currently to an individual PC. Many cable providers have replaced their coaxial lines with fiber optic lines in order to increase their speed and bandwidth.

OC 1 through 255 – is short for Optical Carrier, used to specify the speed of fiber optic networks conforming to the SONET standard. The list below shows the speeds for common OC levels.

OC# = Speed - Common Usage

OC-1 = 51.85 Mbps - ISP to Internet infrastructure

OC-3 = 155.52 Mbps - Large company backbone

OC-12 = 622.08 Mbps - Internet backbone

OC-24 = 1.244 Gbps - Internet backbone

OC-48 = 2.488 Gbps - Internet backbone

Optical Carrier speeds above 48 are used for Internet backbone or other commercial high speed data transfer applications.

A Lan is a Local Area network. Local area is not strictly defined - it could be internal to your house, it could be to your floor in a building, it could be an entire floor of a building. Local generally means that you're serving an internall define group of people and sharing data locally between you. This is different from a WAN (Wide Area Network) that can be between buildings, betwen campuses, between cities, and so on.

A T-1 line is the name for a phone-company supplied data connection that moves data at about 1.5 mb per second. That used to be considered fast, but is not anymore - many cable modems go faster than a T-1 line.

T-3 is usually the next step up - it moves data at around 43-45 megabytes per second - that's pretty fast. That's about twice as fast as a cable modem runs.

The next step up is OC (Optical Carrier) data lines:

OC = Speed
OC-1 = 51.85 Mbps
OC-3 = 155.52 Mbps
OC-12 = 622.08 Mbps
OC-24 = 1.244 Gbps
OC-48 = 2.488 Gbps
OC-192 = 9.952 Gbps
OC-255 = 13.21 Gbps

DSL stands for digital subscriber line - and that refers to sorta high speed data service over the copper wires that bring phone service to your house. DSL is almost always about 1/3 the speed of a cable modem.

LAN = Local Area Network. A LAN is the network inside your house/office (assuming you have a network and not one computer). It connects your local computers together through hubs/switches and wireless access points. Generally, you connect your LAN to the internet using one of the other technologies.

T1 is the old standard for high-speed service from the phone company (24 pulse-code modulated, time-division multi-plexed voice channels to be exact). It is not just for internet access and works for any telecommunications need. When DS-1 (Digital Signal 1) is run over the T1 line is when it generally becomes high speed internet (1.5Mbps). T2 and higher are just bundles of T1 lines (1 T4 = 6 T3 = 42 T2 = 168 T1 or, put another way, T2 = 4 T1, T3 = 7 T2, T4 = 6 T3).

DSL = Digital Subscriber Loop (or Line). This is the "modern" residential high speed internet access method offered by the phone company. Attainable speeds depends on how far your house/office is from the DSLAM (Access Multiplexer) which are usually in COs (Central Offices) but are sometimes elsewhere. In theory, DSL can achieve 24Mbps.

Cable Modem is the "residential" high speed internet access method from the cable company. Many people will get higher download speeds with a Cable Modem (compared to DSL) - however, Cable usually has the upload speed highly limited (384kbps is common).

VIOS (and similar) are "last mile" optical solutions that provide very fast very reliable (based on what I've heard from friends) internet access. Unfortunately, it is only available in very limited areas (only parts of New York City for VIOS I believe).


Fractional vs. Full T1

There isn't much of a cost savings between a fractional T1 and a full (1.5 Mbps) T1. Why? So we can better understand, let's start by taking a look at the specific costs of delivering a T1 service either Full or Fractional.

The service provider has two costs associated with your fractional T1 - the "local loop" and the "port". The local phone company ( LEC - Local Exchange Carrier ) provides and installs the loop. The T1 provider supplies the "port" which is the connection between the local loop and the Internet.

Loop Cost

The cost of your local loop is exactly the same - irregardless if it's a full or fractional T1 because the local phone company always sets the local loop a 1.54 Mbps. Why? Because it takes the same amount of copper wires, time to install, and equipment to run a fractional T1. The LEC passes this cost to your T1 provider. Since there are no cost savings for the T1 provider or the local phone company on a local loop, the end user doesn't get any cost savings on this portion. Advantages - This can save time and reduce or eliminate install fees in the event you expand your bandwidth in the future. The Full T1 circuit is already in place.

Port Cost

The cost of the port has two parts. Equipment and bandwidth charges. The equipment is the same for the local loop. The amount of time required to install and maintain the fractional T1 port equipment is the same as required for a full T1 port. No cost savings on equipment.

Cost Savings

For the T1 provider, bandwidth charges make up probably only 10% of the total cost of providing a T1. Fractional T1 providers are willing to discount services only slightly because it only costs them slightly less to offer the fractional T1 instead of the full T1! Except for bandwidth expenses, the T1 providers' cost of offering fractional and full T1 service is nearly the same when selecting speeds of 512 Mbits or 768 Mbits.

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Page last modified on June 03, 2010, at 07:37 AM EST