PWE3/Dry Martini: Drink Up

Convergence is the final frontier for every service provide. And while the telecom industry doesn’t have a Captain Kirk-equivalent to lead the charge, the notion of convergence remains a challenge for service providers.

The simple answer would be to just force IP into every network, but the reality is that every incumbent service provider has an existing set of profitable circuit-based services (e.g., ATM, frame relay and private line) that enterprise users still depend on to support their business needs.

At the very same time, all parties are well aware of, and are moving to capitalize on, IP networks. So, how do you maintain those existing profitable s ervices while migrating to a consolidated IP/MPLS backbone and while also fulfilling the desire for new IP-based Ethernet services? The answer might lie in the IETF’s PWE3 (pseudo wire edge-to-edge) mechanism.

Previously called the Martini Draft, PWE3 was initially designed to emulate Ethernet over MPLS. With PWE3, this extends to any service, whether it is frame relay, ATM, or Ethernet over a packet-switched network. PWE3 can encapsulate a service specific PDU (protocol data unit), which contains the necessary data and control information to emulate a specific service. In addition, PWE3 can serve as the foundation for emerging virtual private LAN service and virtual private wire service. But while PWE3 is a sound mechanism for IP/MPLS revolution, not all networks are IP-based.

While not yet exactly shaken or stirred, Dry Martini allows a service provider to extend PWE3 over these networks without the need to install an IP/MPLS layer between each node. Although admittedly the PWE3 and Dry Martini are still nascent, there are a number of applications that could be a good fit for PWE3. There’s a growing cadre of players (Alcatel, Axerra, Cisco, Hammerhead, Juniper, Mangrove and Overture) developing solutions to take advantage of this burgeoning market. In addition to emulating wireline services, PWE3 and Dry Martini can handle wireless backhaul, FTTX and DSLAM backhaul.

John Coons, vice president of telecom infrastructure for Current Analysis, says the emergence of the Dry Martini and PWE3 shows the dedication to appeal to a broader set of networks and services. “In the late ’90s we had MPLS pop out, and one of the first interesting uses of that was for VLAN services. Then you had Lucca Martini write his Martini draft, which was specific to Ethernet emulation over MPLS, but eventually that got generalized into PWE3.”

Coons added: “The first event was taking something specific, which was the Martini Draft, and generalizing that to handle a bunch of different protocols. I kind of look at Dry Martini as taking PWE3, which was specified for running over IP/MPLS networks, and generalizing it so it can run over any sub-IP network. From that standpoint, I always applaud whenever technologists take something more specific and generalize it to make it much more useful.”