Hammerhead takes PBT past point-to-point

Hammerhead Systems today unveiled a new version of its carrier Ethernet aggregation switch designed to bridge the gap between provider backbone transport (PBT) and multiprotocol label-switching (MPLS) technologies as well as to allow PBT to become more than just a point-to-point technology.

As announced in April, a software upgrade on the vendor’s quarter-rack 120-Gb/s HSX 6000 edge aggregator uses pseudowires to translate MPLS traffic into PBT traffic, allowing carriers to maintain complementary networks: MPLS in the core and PBT in the metro, for example.

But the HSX 6000 also does something perhaps more noteworthy in that it aims to bring PBT, a Layer 2-based tunneling technology, beyond its current limitations as a purely point-to-point architecture. Starting sometime in the first half of next year, the 6000 will include support for point-to-multipoint and multipoint-to-multipoint networks, defined by the Metro Ethernet Forum as E-Tree and ELAN, respectively.

To provision and manage tunnels in these networks, Hammerhead’s switch will rely on control plane software from a partner, Soapstone Networks, a startup created earlier this year by core router vendor Avici Systems.

“It’s up to Soapstone to provision these boxes and provide quality of service,” said Norival Figueira, Hammerhead's principal architect.

However, Hammerhead’s relationship with Soapstone is not exclusive, and Hammerhead executives say they are already talking to potential alternative suppliers of PBT control planes, though none are currently known to exist outside Soapstone.

“We know there are other solutions out there,” said Rob Keil, Hammerhead’s founder and vice president of marketing. “As they mature and as customers embrace other solutions, we’re open to working with a whole range of third-party providers.”

A key part of Hammerhead’s approach is the use of virtual switching instance (VSI), a technology standardized by the Internet Engineering Task Force and used widely already for virtual private LAN service (VPLS). With VSI, switches learn the MAC addresses of the switches in their immediate vicinity, building a table of those addresses, much as they would in a standard Ethernet LAN. But whereas Ethernet LANs learn the addresses of physical ports, VSI learns the addresses of the virtual ports that are pseudowires. And unlike standard Ethernet LANs, VSI does not require spanning tree protocols, which are incompatible with PBT.

Hammerhead executives imagine carriers will want to make use of the system’s E-Tree capabilities for delivering IPTV. One criticism of PBT since Nortel Networks began marketing it last year has been its inability to handle multicast traffic. Nortel has been recommending the use of a more common standards-based technology, provider backbone bridging, or PBB, in those cases.

Keil acknowledges that small telcos offering video services may not use MPLS in their IPTV networks (since their video headends may be close to their customers) and therefore may not need a system that interworks MPLS and PBT for E-Tree networks. But, in addition to large telcos with great distances between their customers and their superheadends, Keil said, the E-Tree application may also be useful in financial applications—in the multicasting of real-time stock-trading data, for example.

The challenge in selling the solution to major carriers, however, may be their reluctance to trust a small startup like Soapstone with the complexity of control plane management. That’s another reason why an emerging alternative provider of PBT control plane software could come in handy.

Hammerhead also hopes its approach adds a salve to some of the debates between PBT switch vendors and entrenched MPLS router vendors.

“Router vendors have not shown a willingness to work with any vendor embracing [PBT] in any way,” Keil said. “The beauty of Hammerhead’s approach is we allow customers to interwork with MPLS routers--be they Cisco, Juniper, Alcatel--without Cisco or Juniper having to weigh in one way or the other.”