Accelerating Wholesale Carrier Ethernet: 4 Success Factors
As Ethernet services have grown in popularity, communications service providers (CSPs) are coming to terms with the fact that, in order to deliver this popular offering to multi-site enterprise customers, they must partner with other operators to expand their service footprint and reach. This has resulted in a red-hot wholesale market for Carrier Ethernet which has surpassed Frost & Sullivan’s predicted growth rates with rising demand for Ethernet both for mobile backhaul (tower/cell site access) and aggregation. Heavy Reading expects this trend to continue into the foreseeable future.
Wholesale Ethernet, also referred to as E-Access, is an integral part of the MEF’s CE2.0 initiative. An E-Access service is one offered by a wholesale operator as a virtual connection between one or more end user locations and the retail service provider. The interface between the operator (who has last mile access in this case) and the end customer is an Ethernet port called the User Network Interface (UNI). The interface between the operator and the service provider (who sells the service to the customer) is also an Ethernet port and is called the External Network to Network Interface (ENNI).
Figure 1. E-Access and the relationship between operator and service provider
Despite the efforts of the MEF and other standards organization, the early pioneering service providers who are already buying and selling wholesale Ethernet services have discovered that there are four key factors – not covered by the current standards – that are required to offer successful Ethernet services.
These four factors critical to the success include support for:
- Consistent Class of Service (CoS)
- Local switching
- Fine grained Quality of Service (QoS)
- Broad on-net service footprint
Mapping Service Classes for Consistent User Experience
The service provider challenge is that CoS levels that determine guaranteed delay, jitter, and loss of characteristics required of the service in a network are not universally supported by operators and service providers. If the demarcation device at the User Network Interface (UNI) is not able to push multiple tags with meaningful CoS information in all, then the service provider must re-mark the traffic so it is handled properly in the service provider network. To do this, the service provider Service Edge equipment needs visibility into all three CoS levels on the traffic, the Service Provider, Operator, and Customer CoS Domains, or 3-CoS domain support.
Figure 2. Class of Service Treatment must be Consistent Across Domains
Like Politics, Business Traffic is Local
The ability to locally switch service is critical in reducing network ports, backhaul expenses and latency. Wholesale Ethernet adds an additional consideration for local switching because now the connected business locations appear as virtual circuits in the same GigE interface between the service provider and the operator. This creates a condition where frames with the same MAC addresses are received and sent back out on the same Ethernet interface on the Service Edge equipment, but in different virtual circuits.
Figure 3. Hairpin local switching saves ports and backhaul expenses
Traditional Carrier Ethernet switches do not handle this condition, referred to as a “hairpin”. If the Service Edge equipment cannot support local and hairpin traffic then the service must be forwarded deeper into the service provider’s network, increasing the equipment cost, backhaul expenses and service latency.
Per E-Access EVC Quality of Service (QoS)
Another important factor is the granularity with which the service provider administers QoS on wholesale Ethernet. The wholesale Ethernet interface carries multiple virtual connections. Each virtual connection delineates a customer end point. In a congestion situation, service providers must control what packets are dropped and not leave that to the operator. For the service provider this means that it is not enough to have output queuing and scheduling only on a per-interface basis. The Service Edge equipment needs the ability to manage QoS on a per-customer or per-service class end point basis. This means having the ability to define and manage QoS for multiple “virtual interfaces” within the physical GigE.
Figure 4. Managing per-EVC QoS in local switching Environment
Selling E-Access – Footprint Matters
As a seller of wholesale Ethernet access, the number one success factor is whether or not you have access to the business or cell site to which your buyer is trying to connect. The more on-net buildings and towers you serve, the greater likelihood you will win the business when the buyer comes calling. The most successful wholesale Ethernet operators have learned that using multiple access technologies, including Ethernet over bonded Copper T1, DS3 and SONET to augment their on-net fiber buildings ensures they can reach the end customers no matter where they are located.
Figure 5. The E-Access Provider with Broadest Footprint will Win