IP T1 Line Service

T1 line service has been available for decades. It originated as a proprietary telephone company technology designed as a trunk for transporting multiple phone calls between switching centers. Later, T1 was made available for businesses to support their PBX phone systems. When the Internet came along, T1 lines were pressed into service as dedicated Internet connections. But now we live in an IP world. Can T1 also act as an IP connection?

Yes, it can. That may seem counterintuitive to those who understand the origins and technology behind T1 service. The T-Carrier specifications, of which T1 is the most popular line service, describe a system organized as multiplexed channels 64 Kbps wide. That channel size was optimized to transport a single independent digitized telephone call using PCM (Pulse Code Modulation). Clearly, T1 is oriented toward the switched circuit based public telephone network.

That’s true, but the important thing to remember about digital network technologies is that a bit is a bit. It’s either true or false, one or zero, regardless of the particular physical layer or higher level protocols involved. That means that a time division multiplexing technology like T1 can be used to transport a packet oriented technology like IP or Ethernet with a little protocol conversion.

That’s essentially what’s being done when T1 lines are used for data transmission. It’s been a long time since anything but Ethernet has been the standard for local area networks. Ethernet is an IP technology, based on packet switching. Those packets can be queued up and loaded into T1 frames for transmission through T1 lines and even multiplexed into T3 and SONET frames for longer haul transmission. At the far end, the packets are offloaded and sent on their way through an IP edge router connected to the T1 CPE (Customer Premises Equipment.)

If you want to connect your Ethernet networks over metropolitan and wide area networks, one technology you’ll be interested in is called Ethernet over T1 or EoT1. This is also called EoDS1 for Ethernet over DS1.

DS1 is simply the data service or protocol that runs on T1 lines. The reason there are two designations is that T1 describes a physical line consisting of two twisted pair copper telco loops running at 1.5 Mbps. The DS1 is all the bits formated for transmission just before loading into the actual T1 line. You can take that same DS1 and feed it into an add/drop multiplexer and transport it along with many others on a T3 circuit or a fiber optic service like OC-3. At the other end, the DS1 can be demultiplexed from the other services on the same line and delivered separately.

In practice T1 and DS1 refer to the same thing to the actual user. What’s important is that Carrier Ethernet service can be delivered on a T1 line, albeit bandwidth limited to 1.5 Mbps. Who would want service that slow? Lots of companies need connectivity between locations, but don’t require high speeds. They may be using the service for retail credit card verification, communication with corporate headquarters, or to upload files to their web server. The big advantage they have with T1 lines is that they are almost universally available. If you can get business phone service, chances are that you can also get a T1 line installed. They are connected over the same telco wiring.

The competing service to Ethernet over T1 is Ethernet over Copper. That may seem like a fine line of distinction, but it is important. Ethernet over Copper (EoC) also uses twisted pair copper but a different modulation scheme that offers higher bandwidths but with distance limitations. If you are within a mile or two of the central office that has Ethernet over Copper equipment, you may be able to get 10 Mbps, 20 Mbps or even higher bandwidths from EoC. Some installations are transporting in excess of 100 Mbps over multiple copper pair.

Ethernet over T1 bandwidth can also be improved by adding more copper pair. The process of combining the bandwidths of several T1 lines into one larger bandwidth is called bonding. EoT1 bonding can deliver up to 10 or 12 Mbps to both metropolitan and rural areas, providing the equipment is available.

Are you interested in an IP connection for your computer or converged voice and data networks? If so, get pricing and availability for Ethernet over T1 or Copper now to see how much bandwidth is available for your business locations.

From LAN to MAN to WAN

We’re in something of a network revolution right now. Computer networking has deployed many different protocols for communication. Some of these have been borrowed from the telephone industry. But there’s a consolidation underway that is moving toward a single IP networking standard. From LAN to MAN to WAN, it’s all headed toward IP.

The standardization really started in the LAN or Local Area Network. Nearly all LANs are now constructed using Ethernet network interfaces? It’s not that other network architectures don’t have merit. It’s simply economy of scale. Perhaps the PC, more than anything else, helped to settle the issue with 10/100 Mbps NICs (Network Interface Cards) being included as standard equipment. Today’s faster machines offer 10/100/1000 interfaces with RJ-45 as the standard connector. If you want anything else, you have to pay extra.

This economy of scale encompasses not only desktop computers, but laptops, network switches, routers, servers, cabling and various appliances. The higher the volume produced, the cheaper each interface circuit becomes. Until something very much better comes along, Ethernet is the low cost solution.

The situation has been quite different beyond the company premises. The telephone industry has about a 100 year lead on the computer industry. If you’ve wanted to connect two business locations together or join the Internet, you had to convert your Ethernet protocol to something the telephone system could understand. Remember dial-up modems? Today’s equivalent is the T1 line. It’s all digital and offers rock solid 1.5 Mbps connectivity, but it’s a telco standard service.

The LAN to MAN or WAN connection is most often made with an interface called a CSU/DSU. This can be a stand alone box or a card that plugs in an edge router. It provides the protocol and signal level conversion between Ethernet on the LAN and T1 line connecting through the central office.

More recently, the T1 connection and faster speed DS3 and OCx services have been challenged by the rise of Metro Ethernet services. With MetroE, you connect directly from your Ethernet LAN to an Ethernet MAN and back again at other locations around town. Since this is a Level 2 switched service, it’s like having a way to expand your LAN over a much larger area to include other offices, a factory, warehouses, and an offsite data center.

Metro Ethernet melds LAN and MAN with one common service protocol. But what about the WAN or wide area needs? WANs often encompass regional areas of the country or even the entire US. Very large WANs include locations around the world. These, too, can now be joined by Ethernet through MPLS networks. While MPLS has an IP core, it uses its own tag switching system instead of IP routing while on the network. But being a multi-protocol system, it can easily transport Ethernet. Some larger providers have national and international service footprints, making it easier than ever to connect from LAN to MAN to WAN.

Are you interested in maximizing the efficiency of your metropolitan and wide area network services while minimizing your costs? You should get a quick quote on MAN & WAN Network Bandwidth to see how much you could be saving.