From ATM to IP/Ethernet

Ravi Mali, regional director, MENA Region at Tellabs outlines three approaches for enterprises to migrate from ATM to MPLS

Tags: Tellabs (www.tellabs.com)
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From ATM to IP/Ethernet Ravi Mali from Tellabs says that there are three different approaches to ATM-to-MPLS migration.
By  Ravi Mali Published  December 4, 2012

Ravi Mali, regional director, MENA Region at Tellabs outlines three approaches for enterprises to migrate from ATM to MPLS.

Depending on the existing customer base and service mix, as well as individual business strategies, service providers have three basic options when it comes to an ATM-to-MPLS migration strategy. They can migrate to IP/MPLS using:

Approach 1: ATM/FR service migration

Service providers can use IP enabled ATM or FR to migrate legacy services to MPLS-based services like IP-VPN or Ethernet, for example. The Layer 3 MPLS-based IP-VPN approach has one major advantage over legacy Layer 2 ATM and FR VPN services: ease of connecting new IP/Ethernet-based customer sites. While MPLS-based IP-VPNs can deliver cost-competitive, scalable and flexible services, using them to migrate ATM/FR services to MPLS is not the best option for all end-customers.

For one, many customers cannot and will not share their IP routing information for customer-specific routes with their service provider — a requirement when implementing MPLS-based IP-VPNs. This is often the case for route-sensitive customers like government agencies or financial institutions. Secondly, the service provider will need to maintain the existing ATM network and the IP/MPLS network in parallel for some time as this transition from ATM to IP/MPLS takes place.
Finally, all of a given customer’s endpoints connected and communicating using a common service need to be migrated simultaneously in a flash cut, adding both planning complexity and inflexibility.

Advantages:

- Ease of connecting new IP/Ethernet-based customer sites

Disadvantages:

- Requires supporting parallel ATM and IP/MPLS networks throughout a long migration

- Migration to IP/MPLS network requires an operationally complex customer-by-customer service cutover

- Potential revenue loss from customers that do not want to migrate away from ATM/FR

- MPLS-based services like IP and Ethernet lack the end-to-end OAM, QoS and security of the ATM networks

Approach 2: ATM/FR Data tunneling over MPLS

Service providers that do not want to share their customer specific IP routes can be migrated to an IP/MPLS core if the service provider constructs pseudowire-based Layer 2 VPNs. The pseudowire solution enables legacy services, such as ATM and FR, to traverse new high-speed packet networks while maintaining original attributes. However, the downside of the pseudowire migration strategy, especially for larger service providers, is that pseudowires lack dynamic setup or signaling of ATM/FR connections over MPLS, limiting large-scale deployments.

As the number of customer sites grow, the number of pseudowires needed to provision is going to grow by orders of magnitude. In addition, like the IP-VPN approach, all of a given customer’s endpoints connected and communicating using a common service need to be migrated simultaneously in a flash cut, adding planning complexity. The pseudowire solution works well for operators with fewer ATM/FR connections on an MPLS core. But, to simplify provisioning with dynamic connection setup, or to link multiple regional ATM networks over an MPLS core, a more scalable approach is required.

Advantages:

- No sharing of IP routing information needed

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