SONET Rings To Support Ethernet

The hot bandwidth service these days is Carrier Ethernet. Everybody wants it once they see the cost advantage over the WAN connection they have now. The big question is can they get it?

In most cases, the answer is yes for a couple of reasons. First, new competitive carriers are rapidly building out their fiber optic core networks based on IP from the start. These networks are tailor made for Carrier Ethernet services. It’s relatively easy to get a point to point Ethernet connection between two distant business locations and use it to link their respective LANs. The result is one larger bridged LAN that enables all employees to be on essentially the same corporate network.

The other reason that Ethernet WAN services are so readily available is that established SONET fiber optic networks are being pressed into service to deliver Ethernet to the customer. This is known as Ethernet over SONET or EoS. The core of the network is still SONET, but operations at that level are invisible to you. As far as you are concerned, your connection is Ethernet all the way.

There’s no reason that SONET can’t transport Ethernet, ATM or other protocols. It was designed as a transport technology and has been adapted over the years to carry whatever traffic required hauling. The origins of SONET, like T-Carrier, are with the telephone industry. The name is an acronym for Synchronous Optical NETwork. Note the term synchronous. That tells you SONET is set up to be a highly synchronized network. The designed is based on multiplexing thousands of small channels called DS0s that each hold one telephone call. These DS0 building blocks can be combined to create T1 and T3 lines or SONET services such as OC-3, OC-12 and OC-48.

The beauty of synchronization for circuit switched architectures based on time division multiplexing is that everything is orchestrated so tightly and you can easily multiplex and demultiplex channels and higher level services. The device that does this is called an ADM or Add/Drop Multiplexer. An ADM can drop off a T1 line, DS3, OC3 or other service at your door from a much higher speed fiber line that carries traffic for many customers.

How does Ethernet squeeze into those tiny telephone channels? It takes some doing, considering that each DS0 carries exactly 64 Kbps. That’s about the speed of an old dial-up modem. What the industry has done is replace the telephone oriented channels with large concatenated frames and various mapping techniques to more efficiently carry Ethernet packets. SONET networks can now readily carry Ethernet services from standard 10 Mbps Ethernet to 100 Mbps Fast Ethernet, 1000 Mbps Gigabit Ethernet (GigE), and 10 Gigabit Ethernet (10GigE).

A feature of most SONET networks that makes them highly reliable is their twin ring design. Two separate fiber strands are used simultaneously. Each carries the same traffic, but in opposite directions. If a fault occurs in the working ring, the network switches over to the protection ring within 50 mSec. This self-healing property works best when the two rings are widely separated so that a single backhoe cut or equipment fault doesn’t take out both rings at once.

Ethernet over SONET and native IP networks are making Carrier Ethernet services of all speeds readily available for businesses looking to upgrade their bandwidth connections at reasonable costs. How much are we talking? Find out with an instant online Ethernet Fiber quote for 10 Mbps to 1 Gbps service levels. Higher bandwidths and SONET services quotes need some manual effort but will be sent to you promptly.

WAN Computer Network Connections

Computer networks are often categorized as LAN, MAN and WAN. The LAN is your local network. You design and maintain it to meet your specifications. Or, you hire a contractor to do this. When you need to connect your LAN to another LAN across town or around the world, you enter the realm of the MAN and WAN. Here’s a quick look at what’s available in the way of metro and long haul connections.

The difference between the MAN and the WAN is largely a matter of degree. The MAN is a Metropolitan Area Network. As the name suggests, MAN services are limited to a particular city or city and suburbs. It’s the right connectivity for companies that have multiple offices in the same city, a main facility and a remote data center across town, a factory or warehouse in an industrial park plus some satellite offices. Hospitals and their associated medical centers are good candidates for MAN service, especially higher bandwidths for medical image transmission.

A difference between the LAN and MAN is that you own your LAN and buy services from the MAN. A Metropolitan Area Network is typically privately owned and offers services to numerous clients. The network operator manages bandwidth and security to ensure that every customer feels like they have the network all to themselves.

Most MANs are organized as SONET rings that encircle the metropolitan area. A SONET ring is actually two fibers with the same traffic running in opposite directions. One is the primary service and the other is the backup. This is done to ensure reliability. If one fiber or its associated equipment experiences a failure, service is automatically switched to the other fiber in the ring within 50 milliseconds. SONET has designated service levels at OC-3 (155 Mbps), OC-12 (622 Mbps), OC-24 (1.24 Gbps), OC-48 (2.49 Gbps), OC-192 (9.95 Gbps) or OC-768 (39.8 Gbps). You may also be able to get DS3 service multiplexed onto an OC-3 service for transport across town.

Newer metro networks may offer Carrier Ethernet instead of SONET. Ethernet is highly scalable from as low as 1 Mbps on up through 10 Gigabit Ethernet. Popular MAN service levels are 10 Mbps, 100 Mbps, and 1,000 Mbps or GigE. An advantage of Ethernet is that changes in service level can be accomplished faster than with traditional SONET. You can also get layer 2 Ethernet connectivity, such as E-Line and E-LAN, to connect your LANs at other locations into one large bridged network. The MAN itself may have an IP core or be running as Ethernet over SONET to use existing facilities.

Think of the WAN as a very large MAN and you probably won’t be far off. WAN networks may also have SONET rings or IP core networks. They are certainly fiber optic based and often with so many strands that you can lease wavelengths or even dark fibers. Many WAN networks are structured as MPLS or Multi-Protocol Label Switching networks for flexibility. A MPLS network has inherent security due to a propriety routing technology that is not IP. MPLS networks can transport any protocol by encapsulating the packets within the switching labels.

WAN networks may have a regional, national or international footprint. Some are designed with low latency paths that are especially important for financial trading. WAN networks may also peer with other networks of similar size to share traffic. The newest wrinkle is the Ethernet Exchange that exchanges Ethernet traffic without having to first convert it to SONET.

How do you connect to a WAN network? Often you can pick the connection that is both readily available and lowest in cost for your particular application. These range from T1 lines to Ethernet over Copper, Ethernet over Fiber, and SONET last mile connections. In some cases, fixed wireless access is also available. The mix of copper, fiber and wireless access should accommodate just about any need.

Do you have a need to connect your LAN to another facility across town, or to locations in other states or countries? Compare prices and availability of various MAN and WAN connectivity options to meet your requirements.