Multiservice switches were built to offer ATM and frame relay services. Now some service providers are leveraging — or wanting to leverage — the investment in those switches by extending them to offer additional layer 2 services such as Ethernet and voice over packet. At the same time, service providers that have or are building MPLS backbones want to fill up those core networks with revenue-generating, layer 3 services like IP VPNs. Meanwhile, carriers want to be able to use all their network assets and services to deliver end-to-end services to corporate customers whose needs may vary on a site-by-site basis. Service interworking can help make all that happen.
“Service interworking has been the missing piece in the area of multiservice networking,” says Jim Guillet, Alcatel’s assistant vice president of product marketing. “We’ve kicked around MPLS now, and we know what it can and cannot do. And now we need to look at service interworking.”
Service interworking can enable a network operator to offer its customers integrated, end-toend services to multiple locations using a patchwork of different networks and technologies. This is important for service providers, given that they may not have homogenous networks to all their customers, and since various customer sites — such as a headquarters office vs. branch locations — may have different service and connectivity requirements.
Alcatel’s Guillet explains that with service interworking, one customer site could connect to the network via a frame relay service, which would then run over an ATM backbone, then connect to an MPLS backbone that then hands off that traffic to a customer at the other end via a public Ethernet service.
Mark Cadiz, marketing manager for Nortel Networks’ Passport switching line, adds the biggest problem with the popular new service known as optical Ethernet is that providers don’t have fiber everywhere. That means carriers need to figure out how to terminate the traffic from optical Ethernet customers. One option, he says, is to terminate that over frame relay or ATM links because the customer already may have that access. Some locations of a given customer may be optical Ethernet while others might be ATM or frame relay, he adds. But that requires service interworking.
Of course, the idea of service interworking isn’t new. ATM-to-frame relay interworking and ATMto- Ethernet interworking are well-established.
For example, Lucent Technologies Inc. products already support ATM-to-frame relay and Ethernet-to-ATM interworking, says Mike Nielsen, who is CTO of Lucent’s Integrated Network Solutions (INS) business and president of Lucent’s multiservice switching unit, which is part of INS.
Additionally, Lucent and its partner Juniper Networks offer an integrated IP VPN solution that enables service providers to carry ATM and frame relay services over a packet-based MPLS network. The IP VPN and Multiservice MPLS Core Solutions consist of Lucent multiservice switches, Juniper Networks routers, Lucent OSS solutions and network services from Lucent Worldwide Services.
Lucent also is developing an IP/MPLS module for its CBX 500 multiservice switches. This will allow customers to interface to an IP/MPLS core network if they wish. Lucent would not provide further details on the planned module during an interview with xchange in late January.
Lucent’s multiservice switching products include the CBX 500, which is an edge ATM switch; the GX550, a core ATM switch; the PacketStar product line, which is used in access and edge ATM applications; and router products that it offers through its partnership with Juniper. Nortel Networks, meanwhile, sells its Passport line of products, which deliver ATM, frame relay, various versions of VPNs and VoIP.
Inbar Lasser-Raab, director of product marketing for wireline data at Nortel, says the biggest issue relating to the convergence of different networks and technologies is how to best design the edge network. The edge needs to be designed for MPLS, Lasser-Raab says, but questions remain about the right price point for new edge products, the characteristics of these edge products, which ATM functions the edge products should have and how these new edge products should relate to edge routers. “That’s an area Nortel is looking at,” says Lasser-Raab. The vendor doesn’t offer an MPLS edge product at this time, she says “but we’ve been putting some R&D dollars into it at Nortel.”
As for Alcatel, its flagship multiservice switch/router is the 7670, which does both layer 2 switching and layer 3 routing. The company also sells the 7470 multiservice platform and the 7270 multiservice concentrator, which today are ATM products that offer native IP routing through plug-in only. Also tying into the theme of edge networking, Alcatel sells the 7750 service router (acquired from TiMetra), which delivers multiple services on routed IP networks.
Alcatel has already implemented a pre-standard version of frame relay-to-Ethernet interworking on its products, Guillet says.
He adds that various industry groups are working on standardizing implementations for frame relay-to-Ethernet interworking, and something called PNNI-to-ATM interworking. This will allow service interworking to happen on a much broader scale, he explains.
Guillet says there are three main pieces of service interworking: the user plane, which addresses how customers’ traffic is encapsulated and carried across the network end to end; the control plane, which has to do with how one network signals the other network; and the maintenance plane, which centers around operations, administration and maintenance issues such as how to detect, diagnose and repair a failure.
On the user plane, Guillet says, most standards are already in place or nearly complete through the work by such groups as The ATM Forum, The Internet Engineering Task Force (IETF), The International Telecommunications Union, and The MPLS and Frame Relay Alliance. One such example is the widely discussed Martini Draft, which is being combined with other drafts to create a document which Guillet, in January, told xchange would be issued in its final form about now.
For the control plane, Alcatel has submitted to the IETF a draft known as Watkinson, which is about how signaling and routing information can be exchanged between MPLS, ATM, frame relay and Ethernet, he says. The control plane work, however, is still in working group mode, Guillet says, adding he expects the IETF to conduct several more sessions on the issue until it reaches consensus on the issues.
Service interworking issues related to the maintenance plane, says Guillet, are just at the beginning of the standards process, and it’s hard to say when this work will be complete. “But for many network operators, this is the most important [piece of the service interworking triumvirate],” he says.
