A host of chip and equipment developers unleashed solutions at the Supercomm show here this past week that enabled operators to map Ethernet traffic directly over existing Sonet infrastructure products.

Prior to Supercomm, many chip manufacturers unveiled OC-48 and OC-192 framer/mapper products that allow equipment developers to take Ethernet streams and map them over Sonet links.

During the show, several OEMs, including Sycamore, Tellabs, Native Networks, NEC and White Rock, followed suit, showing off modules and platforms that optimize Sonet infrastructure for Fast Ethernet and Gigabit Ethernet traffic.

Clearly, the big win here is reuse. "Carriers are asking, 'How do we make Sonet better and cheaper and not do a forklift upgrade?' " said Travis Karr, strategic marketing manager at PMC-Sierra Inc. Right now, the answer to that question lies in Ethernet over Sonet (EoS), he added.

New revenue

"In the short term, EoS is the holy grail," said Robert Schwaber, product marketing manager at TranSwitch Corp. "Carriers can implement it immediately to generate new revenue streams."

For example, Appian Communications (Boxborough, Mass.) demonstrated private-line connections and virtual private networks on its OSAP 4800 and OSAP 1600 boxes. The services behave like private Ethernet rings but traverse the existing Sonet network. "Think of it as a logical ring that spans multiple Sonet rings, with Ethernet running on that virtual path," said Karen Barton, Appian's vice president of marketing.

In a similar vein, Tropic Networks pitched its TRX-24000 — an all-optical alternative to an optical add-drop multiplexer — as a way to send Ethernet over Sonet, over multiprotocol label switching or over wavelengths. "There are some carriers that are thinking about deploying three different networks for these three different services," said Ed Dziadzio, director of product marketing. "A number of them understand they need more than one way to offer Ethernet to a customer, but they also need to leverage their existing infrastructure."

Virtual concatenation (VC) is one of the big reasons that EoS has become a force in the metro sector. Developed by the International Telecommunication Union, the virtual concatenation spec allows carriers to provision OC-48 Sonet pipes on an STS-1 or STS-3 basis. Therefore, designers can band together the appropriate number of STS-1s to support a Gigabit Ethernet stream while provisioning a different set of STS-1s to handle a Fast Ethernet stream.

Sycamore Networks Inc. is one company heavily touting the benefits of virtual concatenation for EoS applications. During the show, the metro optical-core equipment developer unveiled a four-port Gigabit Ethernet module that employs virtual concatenation for its SN 3000 intelligent optical switch. Through the concatenation features, the company believes it can eliminate more than 50 percent of the stranded bandwidth in a Sonet/SDH architecture.

Tellabs is being more aggressive in its capacity-saving estimates. In literature developed for its new 6400 metro transport switching system, the company claimed that VC could reduce wasted capacity by as much as 75 percent.

Following suit

All other manufacturers have followed suit on the virtual concatenation front. Native, Tellabs, NEC, White Rock, Coriolis Networks and Lumentis all displayed EoS equipment at Supercomm based on virtual concatenation as the baseline for mapping Ethernet frames. All the framer/mapper developers are also implementing this functionality in their architectures.

The generic-framing protocol (GFP) is also a key ingredient in the adoption of EoS technology. Defined under the ITU G.7041 specification, GFP is a protocol-agnostic frame delineation and encapsulation mechanism for transporting Ethernet packets. GFP comes in two flavors: frame-mapped and transparent. In the case of Gigabit Ethernet and Internet Protocol, the frame-mapped method is the preferred option.

Tellabs was one vendor that did not initially implement GFP in its 6400 switching product. The company is, however, working on adding this functionality to a future version of the product, said Stephen Susina, senior business manager at Tellabs.

While GFP and virtual concatenation are pretty much standard options, the link-capacity adjustment scheme (LCAS) and the link-access procedure for SDH are currently optional additions for manufacturers.

LAPS, also called X.86, will have its biggest impact for those equipment vendors looking to open the door to market share in Europe, where SDH is the key network technology. LAPS will be an important feature for penetrating the European market, said Bonnie Sitsis, director of product marketing at Sycamore.

Tellabs decided to come out of the gate with LAPS functionality built in. Sycamore and White Rock Networks, on the other hand, held off on LAPS functionality for future product designs.

Unlike the system developers, chip developers are building LAPS functionality into their designs. For example, Agilent, Multilink and TranSwitch all included LAPS as a key feature on their framer/mapper solutions.

The LCAS function is clearly the hotter option. LCAS is seen as a supplement to virtual concatenation, allowing designers to adjust the capacity of the virtual concatenation group in real-time. Therefore, carriers and equipment manufacturers can adjust the amount of STS-1s provided in a group to meet the changing needs of end users and to adjust to changing conditions in a network.

"There is strong interest in a virtual concatenation framer implementation featuring LCAS capabilities," said Tom Spencer, senior marketing manager at Multilink Technology Corp.

The OEMs are clearly driving home that interest. Several boxes, including the Sycamore product, come equipped with LCAS. The companies that don't provide it, such as White Rock, plan to add in the functionality.

Indeed, the matter of complexity could be delaying the adoption of LCAS functionality. Equipment designers need to make some tough choices on when to invoke LCAS functionality in system architectures, said William G. Bartholomay, chief technology officer at TranSwitch. LCAS also puts strains on the control plane, he said.

Fast enough

While most of the efforts so far have focused on developing EoS systems that map gigabit traffic over a Sonet link, there is an equal call for designers to support Fast Ethernet. Clearly, many of the corporations looking to establish private-line Ethernet services feature boxes with Gigabit Ethernet ports. Many of those corporations, however, don't need a full gigabit of bandwidth, said Colin Evans, vice president of business development at Native Networks. There are many cases where the enterprise will only want to connect with remote locations using slower links like Fast Ethernet, he said.

"Although Gigabit Ethernet is coming to enterprise sites, most of the installed base is Fast Ethernet," said Suresh Sane, director of product marketing at TranSwitch. With that in mind, TranSwitch's Ether-Map-48 device can deliver four Gigabit Ethernet ports, 24 Fast Ethernet ports or a combination of the two.

Agilent Technologies also provisioned its new HDMP-3002 for multi-Ethernet rates. Specifically, this chip delivers four Gigabit Ethernet channels. But two of those channels can be provisioned to also handle Fast Ethernet traffic, said Jim Shupenis, strategic business development manager at Agilent.

The support of Fast Ethernet is just one of the functionality questions that chip developers are going to have to face when building IC solutions for EoS designs. Chip designers must also make some tough choices when choosing a speed grade for their parts.

Right now, a majority of chip developers have focused on delivering parts for the OC-48 range and below. In addition to TranSwitch and Agilent, Cypress Semiconductor Corp. and PMC-Sierra have both developed framer/mappers at those rates.

Many of those developers see a sweet spot in the OC-48 rate because it matches well with the current capabilities of today's Sonet networks. In fact, instead of jumping to higher rates, some of those developers have looked to add other functionality like storage-area-networking support. Shupenis said the move to 10 Gbit may not be the next logical move for framer/mapper designs.

Despite those claims, Multilink, Vitesse Semiconductor Corp. and Infineon Technologies AG are prepping framer/mapper devices that work at rates of 10 Gbits/second.

Moving to 10 Gbits

Vitesse is putting considerable effort into developing EoS solutions for the 10-Gbit range, said Andrew Schmitt, product-line director in Vitesse's TDM transport and switching operation. Clearly, many equipment vendors are multiplexing four OC-48 optical links into a single card to reach OC-192 rates. Therefore, designers implementing existing framer/mapper solutions will need to implement four devices to handle the 10-Gbit stream, Schmitt said. "It's better to do a single 10-Gbit part."

Vitesse would be making a mistake by focusing solely on the framer/mapper device. "To support EoS, lots of work also has to be done at the MAC layer," Schmitt said.

Schmitt remained tight-lipped about Vitesse's framer/mapper product as well as its work at the MAC layer. However, the company did say that it plans to release products for that market later this year.