New Edge Architectures Target Smaller Carriers

COLORADO SPRINGS, Colo. — Edge routers that emphasize the streamlined services of smaller carriers will debut this month at Supercomm 2004 in Chicago.

Laurel Networks Inc. has put the functionality of its ST200 broadband remote-access server (B-RAS) into a small chassis called the ST50, emphasizing DSL provisioning and "triple-play" services. Riverstone Networks Inc., meanwhile, has leveraged its traditional base in Ethernet services to offer the 15008 edge router, a 10-Gbit Ethernet system based on an Internet Protocol/multiprotocol label-switching (MPLS) control plane.

The introductions highlight a bifurcation at the network edge. Router vendors that aggregate such legacy services as frame relay, ATM and Sonet emphasize routed aggregation services in which Ethernet is but one Layer 2 choice among many. Laurel is in this camp, as are Cisco, Redback and Juniper.

But OEMs that entered carrier markets via enterprise Ethernet switching--for example, Riverstone, Foundry Networks and Extreme Networks--rank Ethernet as the most important universal service to support. While some analysts consider Ethernet-centric routers one-armed, single-protocol systems, promoters of such architectures insist that, with complex forwarding of IPv4 and IPv6 packets using MPLS flow identification, an Ethernet edge router can be as complex and as useful as its multiprotocol cousin.

Rafael Francis, director of product management at Laurel, said the impetus for moving from the 20RU midplane chassis of the ST200 to the 10RU backplane chassis of the ST50 was carriers' need for small systems suitable for co-located central offices and remote points of presence. The smaller system is less expandable in aggregate capacity--5 Gbits/second, vs. 160 Gbits/s for the 20RU chassis--but Laurel preserved the same chip sets for control plane route controllers, data plane line cards and physical-layer interfaces.Boards for the control and data cards were redesigned to meet the new backplane format of the ST50, and Laurel turned to a new mini-PHY card, 16 of which can be used in a single chassis. There are separate mini-PHYs for 1-Gbit Ethernet and for OC-3/STM-1--any service, any port--multiservice functions. More mini-PHYs will be offered in the future.

When used in B-RAS applications such as DSL fanout, up to 32,000 active sessions can be supported. Version 3.1 of the ShadeTree software, used in both the ST200 and the ST50, supports nonstop PPP session failover and Layer 2 tunneling protocol access concentration. The new software release offers full IPv6 features.

For its part, Riverstone's 15000 series, beginning with the 15008, is based on a distributed, fault-tolerant modular operating system in which all software protocols are run as modular processes. The ROS-X software is based on Riverstone's RapidOS environment.

David Ginsburg, who recently joined Riverstone as vice president of marketing after heading up marketing at Allegro Networks, called fault-tolerant Ethernet routing as viable as multiprotocol edge routers for triple-play applications (voice, video and data). Riverstone works with Marconi Communications and Sonus Networks in packetized voice networks, Ginsburg said.

Riverstone's original switch routers melded the architectural talents of Cabletron Systems Inc. and Yago Systems Inc., which was acquired by Cabletron before that company split into four networking entities. Riverstone uses a programmable ASIC suite to optimize Ethernet systems for MPLS and virtual private LAN services.Ginsburg pointed out the differences among multiservice edge systems that are optimized for ATM, TDM and Ethernet service. But he scoffed at "pretenders who are trying to position enterprise Ethernet switches as multiservice edge platforms."

Several generations of Riverstone architectures had evolved the new 15000 series into a highly fault-tolerant, modular routing system, Ginsburg said.