Monday, June 20, 2011

Pair Bonding and Distance Determine Ethernet Speed

Ethernet over Copper is coming on strong as a competitor to T1, satellite and fractional T3 (DS3) services. It has considerable advantages, such as lower cost and ease of interface. So, just how much EoC bandwidth can you get and where can you get it?

Check out pricing and availablility of Ethernet over Copper solutions.The magic behind Ethernet over Copper is in re-purposing the same twisted pair copper wires that are used to bring in analog business phone lines and T1 lines. There is a huge advantage in making good use of copper that is already in the ground. The installation of that copper has already been paid for. Companies looking to bring in fiber optic service sometimes get a nasty shock when they see what the construction costs are going to be. The technical capability of that copper is also much higher than many assume.

Believe it or not, some carriers are offering 50 Mbps and even 100 Mbps bandwidth over ordinary twisted pair copper. That is enough to forestall fiber installation until even higher bandwidths are required years from now. Typical EoC offerings range from 2 & 3 Mbps on up to 30 Mbps, with steps of 10 Mbps, 15 Mbps, 20 Mbps and 30 Mbps in-between. The bandwidth is highly scalable, but there are tricks in getting it to work.

Many carriers are using terminal equipment provided by Overture Networks, formerly Hatteras Networks. What this equipment does is generate a highly efficient modulation scheme over multiple copper pair. There are variants for 2, 4 and 8 pair setups. One box is at the telephone company office. The other is installed in your building. The hand-off to your network equipment is a standard RJ-45 Ethernet connection. With this arrangement, the telecom circuit looks just like another network link.

What makes this work is the ability of competitive carriers to rent unbundled local loops from the local phone company, also called the Incumbent Local Exchange Carrier or ILEC. Why the ILEC? It’s because by tradition and by law, the ILECs are the owners of all that telephone wire strung on poles and buried in the ground over the last century or so. Since deregulation, competing companies called CLECs or Competitive Local Exchange Carriers have been able to lease just the wires between the phone company office and the service location. That pair of wires is called the local loop.

For EoC to work, multiple pairs of local loop wiring must be available to the business location in question. What’s really desired is just the plain wires between the switching office and the service location with no signals on the line and no equipment installed in-between. Some lines have what is called pair gain equipment in place. This is analog or digital multiplexing circuitry that allows multiple phone conversations to share one physical phone line. Such circuitry is incompatible with the Ethernet over Copper digital signals.

Fortunately most business locations do have 2, 4, 6 or 8 suitable copper pair available. Now it comes down to distance. EoC offers higher bandwidth than bonded T1 lines, but unlike T1 its technology is distance sensitive. If you are more than 15,000 feet or about 3 miles from the telco office serving your location you are probably out of luck for EoC, although T1 is an option. The closer you are to the office and the more pairs of wires employed, the higher your Ethernet bandwidth.

At about a mile, you can probably get whatever maximum service is available. Between 1 and 3 miles, using 2, 4, 6 or 8 pair, you’ll likely get somewhere between 5 and 30 Mbps maximum bandwidth. Bonded T1 lines can reach further but top out at about 12 Mbps using 8 pair.

Obviously, there is no stock answer to exactly how much Ethernet bandwidth you can get at any particular location. It all depends on what facilities have already been installed by the local phone company and which competitive carriers serve your city. You can find out, though, with little effort on your part. Simply request availability and pricing of Ethernet over Copper services for your business location or locations.

Click to check pricing and features or get support from a Telarus product specialist.

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