Let’s see why DS3 has become such a popular bandwidth service and why it will likely be replaced by Carrier Ethernet. A DS3, sometimes called a T3 line, isn’t simply 3x the bandwidth you get with T1. It is 28x the bandwidth. So if you have a 1.5 Mbps T1 line and you upgrade to DS3 service, your new bandwidth is about 45 Mbps. Those numbers are actually rounded so the multiplication isn’t exact. There are also overhead bits that must be assigned to manage a DS3 circuit.As you might suspect, T1 and DS3 are in the same technology family. The tipoff is that DS3 is also called a T3 line. The “T” designation comes from “T-Carrier,” a set of specifications developed by the phone companies right after WWII to convert analog telephone trunks to digital. The T-Carrier specs are based on a 64 Kbps channel called a DS0 for Digital Signal level 0. A DS1 is comprised of 24 DS0 channels or 1.536 Mbps plus 8 Kbps for synchronization and maintenance for a total of 1.544 Mbps. That’s the T1 line speed.
A T3 line is also composed of DS0 channels at the most basic level. What’s so important about DS0 is that it is exactly the right size to carry one digitized telephone call. These channels can also be used to carry data packets instead of phone conversations. Package 672 DS0 channels together plus synchronization and maintenance bits and you have a DS3 running at 44.736 Mbps. That’s the T3 line speed.
T1 lines were designed to be delivered on 2 pair of ordinary twisted pair copper telephone wiring in a multi-pair binder cable. T3 lines were designed to be delivered on coaxial copper line or microwave transmission. Today, fiber optic cable is generally used to transport DS3 and higher bandwidth services. Bonded copper pair may get the job done over short distances, but is only found in densely populated cities.
The fact is that an upgrade from T1 to DS3 is a major move that requires equipment replacement, perhaps significant construction costs, and a considerable monthly lease price increase. Once you run out of bandwidth on a DS3, you need to move up to the next level of compatible services, OC3, at 155.52 Mbps.
What’s the competition for T1, DS3, OC3 and above? It’s a completely different family of network services called Carrier Ethernet, also known as Metro Ethernet. Carrier Ethernet has more in common with LAN Ethernet than it does with T-Carrier technology. T-Carrier was designed to transport telephone calls. Ethernet was designed to transport data packets. Yes, Ethernet can also be used to carry phone calls and does so exquisitely on converged voice and data networks. An Ethernet connection used to transport telephone traffic may also be called a SIP Trunk.
Now, let’s look at the replacement services for the old T-Carrier system. EoC or Ethernet over Copper is a direct replacement for T1 lines. There are two major benefits to going with EoC. First, the bandwidth is higher. A 2 or 3 Mbps Ethernet over Copper service replaces a 1.5 Mbps T1 line. The cost for both services is roughly the same. When you want to, you can upgrade to 10 or 20 Mbps over copper for more bandwidth.
The replacement for DS3 or T3 lines is 50 Mbps Ethernet. You get a modest increase in bandwidth and you’ll likely see a significant reduction in your monthly line services bill. It is not uncommon to pay half or less for 50 Mbps Ethernet compared with DS3.
You’ll need a fiber optic connection for either service. There is no standard fiber service that runs at the DS3 speed, so it is delivered on a SONET OC3 service using just a third of the available bandwidth. Ethernet is far more scalable. 10 Mbps, 100 Mbps and 1000 Mbps are standard network speeds, but you can get a wide range of increments between these levels. A good strategy is to order the Ethernet bandwidth you need now with an eye to easily upgrading to an incrementally higher speed as needed. The trick is to have an Ethernet port installed that can handle the maximum bandwidth you anticipate needing. If you have a 100 Mbps port, you can get 50 Mbps Ethernet out of that port now and then upgrade in steps to the maximum capacity of 100 Mbps later. Often, this can be done quickly and easily with a simple phone call to your service provider.
Are you anticipating a major WAN bandwidth upgrade, or are you already using DS3 service and either want more bandwidth or lower pricing? If so, get 50 Mbps Ethernet pricing and availability before you make any decisions. It’s a service that will serve you well in the coming years and offer a compelling cost savings as well.
