Optical transport technologies are rapidly becoming more friendly to emerging data services, and new data-optimized optical equipment arriving on the market this year is also proving interoperable across various vendor brands thanks to cooperation among key manufacturers that began last fall.
When it meets this month in Montreal, Quebec, Canada, the Data Aware Transport Activity (D.A.T.A.) vendor consortium will have a lot to celebrate--more members, more actual products and success in creating a quiet but substantial revolution in metropolitan fiber optic network efficiency. And happily for carriers, D.A.T.A. vendors also are finding ways to introduce data-friendly components to traditional equipment incrementally to avoid forcing any wholesale change in optical horses mid-stream.
In related news, on July 29, San Diego-based start-up manufacturer SilkRoad Inc. successfull demonstrated what analysts say is a 60-times increase in fiber optic network performance. Unlike dense wave division multiplexing (DWDM), which uses multiple lasers generating multiple wavelengths to multiply optical network capacity, SilkRoad's PathFinder technology multiplies capacity--and accommodates multiple, bidirectional digital and analog services and protocols--over a single, lower-cost laser. SilkRoad promises to make the product commercially available by the first quarter of next year.
Given the potential value of SilkRoad's breakthrough, Atlanta-based telecommunications industry analyst Jeffrey Kagan suggests the startup manufacturer may soon become the acquisition target of a major communications network systems supplier, such as Cisco Systems Inc., San Jose, Calif.; Lucent Technologies Inc., Murray Hill, N.J.; or Nortel Networks, Research Triangle Park, N.C.
Both the D.A.T.A. and SilkRoad stories are good news for metropolitan fiber optic network operators struggling to cost-effectively accommodate both voice and rapidly growing data traffic generated by their customers.
Since its founding last October by ADC Telecommunications Inc., Minneapolis; Atmosphere Networks Inc., Cupertino, Calif.; Fujitsu Network Communications Inc., Richardson, Texas, and Nortel, the goal of D.A.T.A has been development of synchronous optical networking (SONET) products designed to accommodate multiple services.
Independently, each of those manufacturers began to conclude over the past several years that widely used SONET equipment must be made data aware. The problem, they say, is that SONET multiplexing technologies were set before the current data traffic explosion began. Members of the D.A.T.A. interoperability alliance are now integrating technologies--particularly asynchronous transfer mode (ATM) packet switching and DWDM--into their SONET equipment, thereby making SONET intelligent enough to transport various data types over "virtual private optical rings."
Typically, where carriers have built bidirectional rings of fiber that cover metropolitan areas, they employ SONET add/drop multiplexers (ADMs) at nodes along the ring to pick up and drop off traffic. Based on the historical need to aggregate 64 kilobits per second (kbps), time division multiplexed (TDM) voice circuits, SONET standards created a hierarchy of fixed-size channels that are multiples of 64kbps, ranging from 1.5 megabits per second (mbps [T1]) to 51mbps (STS-1) to 155mbps (OC-3), 622mbps (OC-12), 2.5 gigabits per second (gbps [OC-48]) and 10gbps (OC-192).
Such fixed TDM-based channels are fine for constant bit rate (CBR) services like voice, but have proved a square hole for the round pegs constituted by variable rate, bursty data sessions.
For example, a carrier wanting to extend its 10mbps Ethernet local area network (LAN) across a wide area network (WAN) must either shrink the Ethernet to a 1.5mbps rate or pay for a 51mbps channel, thereby wasting 41mbps of capacity.
In the past there have been separate network elements, called service access multiplexers (SAMs), to interwork ATM and SONET, but adding more layers to a network increases costs. Those costs can be reduced or even eliminated when those functions are implemented directly in the transport infrastructure.
To solve this problem, new ADMs like Fujitsu's FLASH600 ADX, introduced in June, employs data-friendly circuit board modules, or blades, that can be integrated ADM by ADM.
"Our approach is to allow the ADX to start as a standalone ADM, then you can add blades to introduce ATM as a data-aware transport," and that blade can accommodate IP over 10mbps or 100mbps Ethernet; native ATM traffic via DS-3, OC-3 or OC-12 links; traditional telephony traffic via DS-1, DS-3, OC-3 and OC-12 interfaces; and standard SONET channels at OC-3, OC-12 and OC-48 line rates," says Paul Havala, manager of wideband product planning for Fujitsu, which plans to introduce an additional blade for direct IP input this fall. In the meantime, the system can accommodate IP when it is interworked over TDM, Ethernet, frame relay or ATM.
Through the use of ATM, such next-generation ADMs can now provision bandwidth on demand to each traffic session while enabling a range of data types to share a fixed SONET channel on a single fiber ring.
ADC, Atmosphere Networks, Nortel and new members of D.A.T.A. including Ciena Corp., Linthicum, Md.; Ericsson, Stockholm; Lucent; Lockheed Martin Corp., Bethesda, Md.; RAD Data Communications Ltd., Tel Aviv; Siemens AG, Munich; and Tellabs Inc., Lisle, Ill., are introducing similar products this summer.
Even in advance of fully integrated D.A.T.A. products, some new carriers are moving ahead with new combinations of SONET, ATM and DWDM to achieve the desired results.
Dallas-based competitive local exchange carrier (CLEC) CapRock Communications Corp., for example, is launching ATM overlay networks over individual DWDM wavelengths, so a customer needing plain telephony can get it over private TDM SONET lines while data and Internet services ride the ATM network.
"With DWDM, we have the flexibility to provide different types of transport, including ATM, separately on additional wavelengths one ADM at a time," says Bryan Olivier, vice president of engineering and program management for CapRock, which plans to complete 6,100 fiber network route miles in the southwest United States by year's end. "And we can make wavelength-based services available for our network customers or for resellers of our capacity."
The so-called ATM bandwidth tax is not a factor with data-aware equipment, which may be slightly more efficient than pure SONET, says Tony Farinholt, ATM transport program manager, ADC Telecommunications. SONET muxes also add overhead at each step of the hierarchy from individual VT1.5s (roughly equivalent to a T1 plus 200kbps of overhead) to STS-1s, OC-3s and beyond.
Another advantage of data-aware equipment, says Alex Dobrushin, vice president of marketing, Atmosphere Networks, is that all traffic types can be converted into a single packet or traffic stream. With this ability to concentrate multiple services, "you can extend the power of the packet backbones all the way to the edge of the network," Dobrushin says.
With TDM-only SONET, a customer who wants a transparent LAN service and Internet access service would have to buy two different services and two interfaces to the network because there is no convenient way of providing those servies on the same interface. With data-aware functions in a carrier infrastructure, those services can be delivered over a single interface.
In Atmosphere Networks' products, "the transport infrastructure is intelligent enough to decide if a packet from a subscriber needs to go onto the transparent LAN service or if it is destined for the Internet," Dobrushin says."
All this promises to go to carriers' bottom lines. According to Dobrushin, Atmosphere's solution is capable of delivering 100mbps Ethernet to a subscriber at the same cost as a 1.5mbps circuit can be delivered over conventional infrastructure today.
Until recently, these kinds of solutions were proprietary, hybrid add-on components to existing TDM-based SONET systems. Even among new manufacturers using all-packet transport for all services, some are using ATM as a mechanism for transport and multiplexing, and other companies are looking to the possibility of using IP as their transport layer.
Now, D.A.T.A. members have reached interoperability agreements among themselves and will demonstrate multiple devices working together in Chicago at the National Fiber Optic Electronics Conference (NFOEC) later this month. And, says Farinholt, the push by the group in the coming months will be to define interoperability for packet over SONET or IP over SONET.
Even in advance of fully integrated D.A.T.A. products, some new carriers are moving ahead with new combinations of SONET, ATM and DWDM to achieve the desired results.
