About T3 and DS3

What's the Difference Between DS3 and T3 Bandwidth?

Don't be confused about the difference between DS3 and T3 circuits. These terms are really synonymous. Instead you should focus on what they can do for you...and the best scenarios for application.

Digital Signal (DS) is a system of classifying digital circuits according to the rate and format of the signal (DS) and the equipment providing the signals (T). DS and T designations have come to be used synonymously so that DS1 implies T1, and DS3 implies T3.

A DS3 line (also known as a T-3) is an ultra high-speed connection capable of transmitting data at rates up to 45 Mbps. A DS3 line is equal to approximately 672 regular voice-grade telephone lines, which is fast enough to transmit full-motion, real-time video, and very large databases over a busy network. A DS3 line is typically installed as a major networking artery for large corporations and universities with high-volume network traffic. Other example applications include large call centers, enterprise wide VoIP and IP PBX systems, Internet service providers, research labs, video conference centers and software development companies. A DS3 is the second fastest, non optical connection offered in North America. A DS3 line is comprised of 28 T1 lines, each operating at total signaling rate of 1.544 Mbps.

DS3 circuits provide businesses and Internet Service Providers (ISPs) with up to 45 Mb/s of dedicated Internet connectivity. This is an ideal solution for users who have outgrown their T1 connections and are in search of unlimited, high-capacity access. A DS3 line actually consists of 672 individual channels, each of which supports 64 Kb/s. DS3 lines are extremely high bandwidth connections into a carrier's backbone. They typically include SLAs (Service Level Agreements) that guarantee uptime and performance.

The DS3 signal itself is composed of 28 DS1 signals and is constructed using a two-step multiplexing process. First, the 28 DS1 signals are multiplexed into seven DS2 signals. Second, the seven DS2 signals are multiplexed into one DS3 signal. Each multiplexing step uses bit stuffing to handle the different input frequencies. Overhead bits provide alignment, error checking, in-band communications, and bit stuffing control information.

Line rate: 44,736,000 b/s 
Signals: 7 DS2 signals = 28 DS1 signals

Overhead bits: 
56 bits total/frame 
F-bits (framing) 28 bits/ 
M-bits (multiframing) 3 bits/ 
C-bits (stuffing) 21 bits 
X-bits (message) 2 bits/ 
P-bits (parity) 2 bits/ 
Data bits between overhead bits 84

A DS3 connection is comprised up of two monthly charges: the local loop and the port charge. The local loop charge is the cost of the circuit provided by the Local Exchange Carrier (LEC) that allows DS3 access into the carrier's network. The loop charge is based on the distance from the customer's location to the edge of the carrier's network; the farther the customer is from the network, the more the loop will cost. Nearly every carrier prices loops differently so it is in your best interest to price DS3 service with several providers to ensure that you get the best deal.

DS Internet Access is the ideal solution for businesses that require high-bandwidth access at a reduced price. Whether you host high-traffic Web sites, support Web hosting or need high-capacity bandwidth on an as-needed basis, there's a level of DS3 service (Full or fractional) that will meet your needs. Fractional to full DS3 or T3 circuits run from speeds of 3 Mbps up to 45 Mbps.

For customers that require more bandwidth than a T1 line can provide but do not yet require the capacity of a full DS3 line, a fractional DS3 connection is the ideal solution. A fractional DS3 is similar to a full DS(T)3, only with some of the channels turned off. This reduces the total monthly cost and provides additional capacity that can be turned up in a matter of days. Unfortunately, the DS3 (T) loop is still required for this service.

If a full DS3 line is more bandwidth that you really need, it is also possible to get Fractional DS3, which gives you a portion of full DS3 bandwidth at a lower cost. Of course, DS3 is also available in multiples to increase bandwidth, similar to bonded T1 service.

DS3 service can be deployed for a wide verity of applications. The most common uses are DS3 point-to-point, DS3 internet, DS3 frame relay, DS3 voice and DS3 VPN. The pricing for these connections varies widely depending on the carrier, location of service and the application for which the connection is being used. Visit DS3 Bandwidth Solutions to obtain current "real time" rate quotes for your location.

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Digital Signal 3

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

• The data rate for this type of signal is 44.736 Mbit/s.
• This level of carrier can transport 28 DS1 level signals within its payload.
• This level of carrier can transport 672 DS0 level channels within its payload.

 

Cabling

DS3 interconnect cables must be made with true 75 ohm cable and connectors. Cables or connectors which are 50 ohm or which significantly deviate from 75 ohms will result in reflections which will lower the performance of the connection, possibly to the point of it not working. Bellcore standard GR-139-CORE defines type 734 and 735 cables for this application. Due to losses, there are differing distance limitations for each type of cable. 734 has a larger center conductor and insulator for lower losses for a given distance. The BNC connectors are also very important as are the crimping and cable stripping tools used to install them. Trompeter, Cannon, Amphenol, Kings, and Canare are some of the true 7.5 x 10 ohm connectors known to work. RG-6 or even inexpensive RG-59 cable will work in a pinch when properly connectorized, though it does not meet telephony technical standards.

Usage

The level of transport or circuit is mostly used between telephony carriers, both wired and wireless.