Metro Ethernet Networking Technology

Metropolitan Area Networks (MAN) are well established as a way for businesses to transport their traffic within a given metropolitan area. Now the MAN is becoming the MEN, or Metro Ethernet Network. Let’s take a look at what this new technology has to offer.

Metropolitan or Metro Ethernet Networks are based on Carrier Ethernet standards established by the Metro Ethernet Forum (MEF), and industry standards group. This ensures that you know what services you are getting and that you can directly compare these services from provider to provider.

Why bother with Metro Ethernet when the MAN connections you have now are working just fine? While these services are no doubt running reliably and getting the job done, you may be missing out on service options that could better meet your needs. You many also be paying more than you really have to.

The core networking technologies of Metro E networks could be pure IP networks or they may be Ethernet services running on top of legacy SONET fiber optic networks. That’s a perfectly legitimate technical approach. Protected SONET rings have a history of high reliability, low latency and considerable bandwidth. As a user, having to deal with SONET at the SONET level does limit your options compared with Carrier Ethernet. You can be better off with Ethernet over SONET or Ethernet over IP core networks.

SONET is a TDM or Time Division Multiplexing technology with all traffic loaded into neat little time slots lined up one right after the other. An ADM or Add/Drop Multiplexer handles getting specific traffic on and off the network. Your connection is by one of the standardized Optical Carrier levels, such as OC-3 (155 Mbps), OC-12 (622 Mbps), OC-24 (1.24 Gbps) or OC-48 (2.5 Gbps).

Carrier Ethernet is based on packets rather than time slots. Packets are distinguished by the information in their headers that are read by switches and routers. This is the same Ethernet than runs on your company LAN. That’s the first advantage of Metro Ethernet. It’s directly compatible with LAN Ethernet so there are no inefficiencies from protocol conversions between dissimilar networks.

The other obvious advantage is interfacing. Connections to Metro E is a conventional Ethernet connector. At lower bandwidths, including 10, 100 and even 1000 Mbps, a standard RJ-45 connector can suffice. Higher bandwidths have fiber optic connectors.

Carrier Ethernet is designed to be both highly and rapidly scalable. You can generally get far more bandwidth options than are available with SONET levels. They are also easy to scale up and down. What sets the limit on your bandwidth is the port speed that you connect through. If you have a 100 Mbps port, you can specify any bandwidth up to 100 Mbps. With a Gigabit Ethernet port, you can get any bandwidth up to 1,000 Mbps. Likewise a 10 Gig E port lets you scale to 10 Gbps. The GigE port is very popular for this reason. You can call up your provider and move up from 200 to 400 Mbps in a matter of hours or days. There is no need to change hardware interfacing as long as you are operating below the maximum port speed.

Metro Ethernet Networks can give you the same point to point connections that you are getting now or a multipoint service that operates as a LAN extension. E-Line is an Ethernet Line Service. E-LAN is an Ethernet LAN service. E-LAN can run at layer 2, letting you connect multiple metro locations together in one large bridged LAN. This is a popular service for companies with multiple offices, factories, warehouses, retail outlets and so on within a given metropolitan area.

Can Metro Ethernet networking technology work to your advantage? Get network options and pricing for Metro Ethernet services to compare with your current connection setup.



Note: Photo of city lights courtesy of Wikipedia Commons.

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.