Why Your Telecom Lines Should Be Switched Ethernet

By: John Shepler

A major trend in telecom services is the massive migration from traditional circuit switched to packet switched networks. Right along with this has come the availability of Ethernet connections door to door and to the Internet. Even so, many organizations still embrace traditional technology and are loath to give up their trusty T1 lines and SONET fiber optic services. Why should they consider making change…. and to what?

Aren’t All Networks Ethernet?
Pretty much all Local Area Networks (LANs), including wireless networks, are based on the Ethernet protocol. There are exceptions, such as Fibre Channel that connects computers to Storage Area Networks (SANs), but the vast majority of networking equipment and software is based on supporting Ethernet.

So, What are T1, DS3 and SONET?
Traditional telecom standards were developed long before anyone thought of using packet technology to communicate. Their intended application was for bundling or trunking telephone lines between phone company offices. Their architecture is based on circuit switching instead of packet switching plus segmenting the line into many individual channels. Each channel carries a single phone conversation. The process for doing this is called TDM or Time Division Multiplexing.

Connecting TDM to Ethernet Networks
You can see there is a technology gap between TDM and Ethernet or IP networks. Fortunately, technology comes to the rescue to make this largely invisible to you, the user. All those little (64 Kbps) telephone channels can be combined on a given line to create one large bandwidth pipe. Plug in modules allow routers to connect to TDM lines going outside and LANs within the company. While this approach has allowed modern computer to computer communications to flourish, there are some good reasons to move on from this protocol conversion approach.

Ethernet vs Ethernet
The Ethernet protocol envisioned by Bob Metcalfe in the 70’s is a different animal than what we use today. The original Ethernet was based on a single wire channel with all packets from all systems vying for access in a giant “collision domain.” This technology is described by the mouthful, “Carrier Sense Multiple Access with Collision Detection” or CSMA/CD for short. It’s a self-policing system where each connection to the network is responsible for making sure that the line is clear before launching a packet and recovering if the packet gets in a collision with another.

This system works, but network gets crowded fast as devices are added and lines interconnected with simple hubs. Communication is limited to half-duplex because only one connection can talk at a time. The big improvement to the technology, and one we still use today, is called switched Ethernet.

The Switched Advantage
The Ethernet switch directs traffic from source to destination rather than having a single party line for everybody. Transmission and reception paths are physically separate on different wire pairs. This alone doubles the network rate from half-duplex to full duplex because devices and talk and listen at the same time. There is no collision domain anymore. Each device has its own network port and the switch takes care of getting the packets to the right place.

Beyond the LAN
It seems logical that the way to connect networks across town should be the same as connecting multiple small networks into one LAN in-house. It hasn’t been because you lose control of the net when you leave your property. Two business locations across town have to be connected through a no-man’s land in-between by a common carrier. This was originally the role of the local phone company but competition has opened the carrier business to many other players.

Scaling Up Ethernet
For decades, the transportation of voice, data and video between locations has been done using legacy switched circuit telecom technologies. Ethernet, by design, was limited to the LAN because of fairly short distance limitations for each network line. To get around this, Carrier Ethernet was developed. It’s pretty much the same switched Ethernet, but with additional provisions for long distance transmission and the operation and maintenance features needed by the carriers to maintain the lines. Carrier Ethernet scales up switched Ethernet so that packets can be carried across town or even around the world.

Ethernet All the Way
Now it is possible to plug your edge router into a familiar Ethernet connection (copper or fiber) at each of your business locations. In-between, the common carrier reliably transports your packets from location to location. It’s Ethernet all the way with no protocol conversions required.

Switched Ethernet Service Advantages
Think of the world as your network. Well, at least your parts of the world. With switched Ethernet, you can bridge two or more locations to put their LANs on one larger network… just like you would in-house. Ethernet Line Service (E-Line) replaces T1, DS3, and SONET OCx lines one a one to one basis. Carrier Ethernet also adds a couple of new options. Ethernet LAN Service (E-LAN) creates a fully meshed network for you. All you need is an Ethernet line connection at each location. Ethernet Tree Service (E-Tree) is a one to many connection that is popular with content providers. One location generates the traffic to be used by many, many other locations.

The Ethernet Cost Advantage
Carrier Ethernet networks are designed to be both easily scalable and lower in cost than what you are used to with traditional telecom services. It is not uncommon to get Ethernet over Copper connections at 3 Mbps for the same price or less than T1 lines at 1.5 Mbps. At higher speeds, the difference in cost is even more dramatic. The scalability technology lets you upgrade the speed of your service quickly and easily, often without needing new equipment installed.

Switched Ethernet For You
Are you thinking that you may be missing out on service improvements and more bandwidth for your money that can be offered by switched Ethernet service? No need to wait. Copper and fiber optic Carrier Ethernet services are available coast to coast and worldwide right now. Discover your options now.

Your Ethernet Connection To The World

It’s a given that you need to connect your business location to the outside world to reach your own geographically separated business locations and to reach anyone, anywhere, on Earth. There are various protocols that will get you this connectivity. The most popular is quickly becoming Carrier Ethernet service. Let’s see why.

Carrier Ethernet is an extension to the switched circuit Ethernet protocol that is nearly the universal for Local Area Networks (LANs). You know that there is a distance limitation to LAN Ethernet networks, especially for those running on Cat 5e/6 twisted pair copper wiring. How is it that Ethernet can now reach across town, to the other side of the country and around the world?

You can thank the Metro Ethernet Forum (MEF) for setting the standards that make long distance Ethernet possible. The MEF is an industry alliance of over 175 organizations who have a vested interest in Carrier Ethernet. Because carriers and manufacturers have agreed to work within these standards, it is possible to have interoperability among Carrier Ethernet systems worldwide.

What’s different about the MAN and WAN versions of Ethernet is that they are transported rather than running natively on the copper or fiber cabling. Technologies that enable this are Provider Backbone Bridges (PBB), Provider Backbone Bridge Traffic Engineering (PBB-TE), Provider Backbone Transport (PBT) and Carrier-Ethernet Transport (CET). Connectivity-Fault Management (CFM-OAM) technology adds operations, administration and management features needed to operate metro and long haul communications networks.

Note that the term Carrier Ethernet applies to Metropolitan Ethernet, also called Metro Ethernet, as well as longer haul networks that go beyond the immediate metropolitan area that is the domain of Metropolitan Area Networks (MAN). That’s because metro and wide area networks are more alike than different. They all involve use of a common carrier to transport the signal rather than private ownership of an in-house local area network.

The MEF has standardized Carrier Ethernet services regardless of the transport mechanism. E-Line is the familiar private point to point line service that is popular with T1, DS3 and SONET telecom services. E-Line gives you a direct ethernet connection between two Ethernet ports located across town or at any distance. E-LAN, or Ethernet LAN Service, is a multipoint to multipoint mesh network that covers multiple locations. These could be branch offices or franchise locations. E-LAN can bridge your multiple site LANs so that they act like one larger network.

Another service is E-Tree which is a point to multi-point service, not meshed. The center or root locations can communicate with any of the remote or leaf locations, but those leaf locations cannot directly communicate. They have to route all traffic through the roots that may or may not pass it on. This is similar to the proprietary star networks that companies have deployed to create their own private wide area networks.

Ethernet can be carried over twisted pair copper as EoC or Ethernet over Copper. It can also be transported over T1 (EoDS1) or DS3 (EoDS3) to take advantage of existing infrastructure. Ethernet can also be provided over fiber optic networks including legacy SONET/SDH and the newer Ethernet over Fiber (EoF) running on native IP networks. MPLS networks can easily transport Ethernet services as pseudowires using MPLS label switched paths. This expands the offerings to include Virtual Private Wire Service (VPWS) and Virtual Private LAN Service (VPLS).

In addition to the availability of standardized Ethernet services over MAN and WAN distances, Carrier Ethernet also offers the advantages of easy interfacing, granular scalability with nearly any bandwidth level available, and considerably lower cost than traditional telecom services. It is not unusual to get twice the bandwidth for the same price or cut your bandwidth costs in half by switching to Carrier Ethernet services.

Is your company looking for a bandwidth upgrade or to expand connectivity beyond your current network? Perhaps you’re curious to see if you could realize a considerable cost savings? If so, get pricing and options for Carrier Ethernet solutions now.

No LAN Is An Island

Corporate LANs or Local Area Networks have traditionally been just that -- local. But now you have the option to link multiple business sites into one very large, all encompassing, business LAN. You do that with layer 2 Ethernet services.

You may wonder what the big deal about this is. After all, you’ve successfully linked multiple locations together for years. But actually, you’ve been linking multiple islands. Each LAN is separate and independent. It has a very clear scope. Usually, the domain of one LAN is a single building. Occasionally, very large buildings may have multiple LANs. It’s also possible to connect multiple buildings on a common campus on the same LAN. The deciding factor is where your ownership of the property leaves off. Once you leave the building or corporate campus, you typically hire a common carrier to transport your network packets.

The reason that your business locations each have their own LAN networks and simply communicate between them is that there has traditionally been a protocol conversion needed to get across town or across the country. Telecom standards have been based on telephony requirements consisting of multiplexed channels. LAN networking standards have settled on packet switching using the Ethernet protocol. Wouldn’t it be nice if you could just extend your Ethernet-based LAN across town?

Well, now you can and you won’t have to run the cabling yourself. Carriers are now setup to transport Ethernet signals as Ethernet. The connections can be either layer 2 switched or layer 3 routed. With layer 2 switching, the Metro Ethernet link becomes part of your overall LAN topology. The office across town is no farther away on the network than the office down the hall.

What level of services are available? You’ll be pleased to know that you can order Ethernet services in the same standardized speeds as used on your network. That includes 10 Mbps Ethernet, 100 Mbps Fast Ethernet, 1000 Mbps Gigabit Ethernet or GigE, and 10,000 Mbps 10 Gigabit Ethernet or 10 GigE.

What’s more, you aren’t limited to simply connecting buildings in the same metropolitan area on the same network. You can extend Metro Ethernet services beyond your immediate metropolitan area to other metropolitan areas. That typically includes medium and larger cities and suburbs. Competitive carriers with nationwide fiber optic footprints can provide as much bandwidth as you require.

Are you ready to interconnect your far-flung LAN networks for more efficient operation? Would you like to enjoy the cost savings that Ethernet offers over conventional telecom services? If so, then find out what cost and performance advantages Ethernet has for your company or organization.