Enterprises have been migrating applications from running locally at each business location to running in centralized data centers for some time. Businesses are pursuing this migration because it results in tremendous savings in capital and operational expenses. It also simplifies and more efficiently enables a business to scale their application and storage requirements during changing economic conditions. However, once applications become centralized, the network becomes a critical component to ensure continuous data center connectivity to maintain business continuity.

Ethernet is the technology used for interconnecting individual users, servers and most networking devices on local area networks. Metro Ethernet is one of the fastest growing wide area networking (WAN) technologies to interconnect enterprise locations and provide high speed Internet access. Data centers have used Ethernet to interconnect servers and some types of storage. In the data center, Fibre Channel storage area networks (SAN) are widely deployed and continue to grow. Ethernet is advancing to support Fibre Channel through a technology called Fibre Channel over Ethernet (FCoE). With Ethernet widely deployed in LANs, increasingly being deployed for WANs and evolving to support SANs, isn’t it time you considered using Metro Ethernet to connect to your data centers?

This paper discusses the Metro Ethernet attributes that provide more flexible, scalable connectivity between your business locations and your data centers than SONET TDM private lines or IP VPNs. Unlike other WAN technologies, Metro Ethernet has some unique capabilities to allow you to more cost effectively connect multiple locations to your data centers.


Metro Ethernet is the fastest growing wireline data service throughout the world, according to Vertical Systems Group. The drivers for this growth are highly relevant when using Metro Ethernet for connectivity to data centers.

Bandwidth Flexibility

Metro Ethernet’s incremental bandwidth options enable you to purchase the bandwidth you need rather than purchase the amount of bandwidth dictated by the WAN technology. For example, if you need 1Gbps to connect to your data center, with SONET, you need to purchase an OC-48 (2.5Gbps) private line because it provides the closest SONET bandwidth increment to 1Gbps. Similarly, if you require 100Mbps, you need to purchase an OC-3 (155Mbps) private line.

With Metro Ethernet, bandwidth increments are commonly offered in increments as low as 1Mbps. This enables you to best match the Metro Ethernet service bandwidth you need to purchase with the bandwidth connectivity requirements to your data center.

With Metro Ethernet services,
you only purchase the bandwidth
you need, when you need it
More Flexible Connectivity Options

Metro Ethernet provides more flexible connectivity than legacy WAN approaches since it can support all types of topologies to connect to your data centers. Metro Ethernet supports point-to-point, point-to-multipoint (hub and spoke), and multipoint (any-to-any) connectivity. This flexibility enables you to optimize your data center connectivity to your business locations. You can also leverage this flexibility to more quickly and cost-effectively connect additional business locations to your data centers or add additional data centers for business continuity.

Metro Ethernet’s flexible connectivity
options simplify adding additional data
centers for business continuity

In Figure 1, three business locations are connected to a primary data center using an Ethernet Private LAN (EP-LAN) service which provides any-to-any connectivity between all locations. The bandwidth for each location is tailored to meet the site’s requirements. Any site’s bandwidth can be increased as required. If a new, secondary data center is added to the EP-LAN service, all other sites, including the primary data center, have connectivity to it.

Figure 1: Data Center added to EP-LAN Service
Figure 2: Two CoS Ethernet Service Example
Figure 2: Two CoS Ethernet Service Example

You assign 30 Mbps for the Gold CoS with a <15ms latency and <0.001% packet loss for your latency and loss sensitive applications and 70Mbps is for the Silver CoS with a <50ms latency and <1% packet loss for applications which have little to no sensitivity to packet latency or packet loss. Refer to Figure 3.

Figure 3: SLOs for example 2 CoS Ethernet Service
Figure 3: SLOs for example 2 CoS Ethernet Service

Network Availability

As applications are migrated to run in remote data centers instead of locally on the in-building LAN, network availability becomes a critical factor in order to maintain normal business operations. If the WAN connection to your data center experiences an outage, you no longer have access to your remote applications. Therefore, you need to carefully evaluate the performance metrics related to Metro Ethernet network availability such as:
  • Availability (or Service Availability)
  • Mean Time to Respond
  • Mean Time to Restore
Availability is typically defined as the percentage of time that a service is operational, measured over a 30 day period. A service may be deemed non-operational depending on the parameter being measured, e.g., packet loss, which would be specified in the SLA. For example, a service would be considered non-operational if there were a circuit failure caused by a fiber cut. This is considered a hard failure because the service is non-operational until the fiber is repaired, unless there is a redundant fiber connection.

The Availability metric also includes other types of failures that may be intermittent such as the service’s packet loss or packet latency exceeding the maximum service level objective over a brief time period. The Availability metric is clearly an important factor in WAN connections to data centers. Availability can be significantly improved by ensuring that the Metro Ethernet network is self healing, i.e., it has multiple levels of redundancy built-in to keep the network operational as faults occur. The Availability metric is critical to understand when using Metro Ethernet to connect to data centers.

Network Availability becomes a
critical Metro Ethernet performance
metric as you migrate your applications
to remote data centers

The Mean Time to Respond can be defined as the average time the Metro Ethernet service provider has to respond to troubleshoot a problem after it is either identified or reported to the network operations center. Mean Time to Restore can be defined as the average time to restore service to an operational condition as defined by the Availability metric in the SLA. These two metrics are important and interrelated because a small Mean Time to Restore would be negatively impacted by a long Mean Time to Respond and vice versa. These two metrics in conjunction with the Availability metric ultimately determine the Metro Ethernet network availability which again, is a critical metric as you move your applications to remote data centers using a Metro Ethernet service.

IP Version Transparency

Metro Ethernet does not require you to coordinate IP addressing and routing information with your Ethernet service provider. You can use existing IP addressing to your data centers with the freedom to use any IP addresses or routing protocols as you add additional data centers or business locations. Also, Metro Ethernet services transparently support IPv6-based applications alongside IPv4.


Enterprises are migrating applications to centralized data centers to achieve significant capital and operational expense savings while enabling efficient scaling of their organizations’ requirements during changing economic conditions. Ethernet enables you to standardize on a common technology for LAN, WAN and a converged data center. Metro Ethernet provides flexible, scalable bandwidth and network connectivity options with the QoS performance and IP transparency you need to connect to your data centers. As you migrate your applications to a remote data center, the WAN becomes a critical component and Metro Ethernet has become the technology of choice to meet these data center connectivity requirements.


Understanding Business Ethernet Services, Comcast white paper
Ethernet Services for Multi-Site Connectivity, Comcast white paper
Metro Ethernet Services – A Technical Overview, Ralph Santitoro, Metro Ethernet Forum


Comcast offers a complete range of MEF certified business Ethernet services including Ethernet Private Line, Ethernet Virtual Private Line, Ethernet Network Service (MEF E-LAN compliant) and Ethernet Dedicated Internet. Each service is offered with a 10 Mbps, 100 Mbps, 1 Gbps, or 10 Gbps Ethernet port in customer-selectable bandwidth increments ranging from 1 Mbps to 1 Gbps. For more information or to request a consultation about Comcast’s Business Ethernet Services, please visit

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