Looking back on the telecom market crash-and-burn, a sort of unofficial network inventory count can be taken. Amidst the rubble of once high-flying long haul networkers, idealistic competitive broadband providers, and stodgy incumbent operators, what, pray tell, is left?

It seems the grim answer is countless miles of unlit, unused fiber "superhighways," with few "on-ramps" to dense commercial and residential areas, and multiple bottlenecks all along the way. In short, the first incarnation of the global transport network is an unconnected mess.

A question that has remained unanswered from the genesis of the boom to the reality of today: Who or what will get all of the tall, shiny residential and office buildings served with broadband communications services?

Once a potential panacea for upstart providers, the multi-tenant (MTU) commercial, multi-dwelling (MDU) residential, and hotel and hospitality markets (collectively called the MxU market here), have been problematic to serve, to say the least. A host of Building Local Exchange Carriers (BLECs) have come and gone as financing from the capital markets has disappeared. Left standing to serve the millions of potential customers holed up in multi-tenant buildings are just a few regional BLEC providers and incumbent telcos reticent to light up the MxU properties within the reach of their network resources.

A grim prospect, yes, but the light at the end of the MxU tunnel might be revealing itself through some major advancements in in-building technology–specifically the recent rise in momentum for VDSL (Very High-Speed DSL) and advanced Ethernet technologies. And as these technologies continue trending upward, the whole MxU mess might just get solved along the way.

How's that going to happen? Today, telecommunications providers are under increased scrutiny with growing competition from both competitive providers and now from cable operators as well. They're feeling the shareholder pinch to generate new revenue streams with advanced services like tiered, IP-based managed bandwidth services and broadband aggregation. Putting intelligent edge routers closer to the access network is an effective way to get to that stage. In fact, recent numbers from Synergy Research Group show that in the last quarter of last year, while the general router market suffered a 9.5 percent slide, service provider spending on edge routing equipment jumped almost 22 percent.

A major obstacle to lighting up complex MxU properties has been getting aggregation equipment and points-of-presence closer to buildings out on the edge of the network. And as providers look to new technologies–like VDSL and Gigabit Ethernet–to add intelligence to the edge, they are one step closer to having the required network elements near all those MxU properties in need of service.

Advancements in new technologies like VDSL are key to this move to the edge. Vendors are pushing faster and faster speeds over copper loops day by day. Much of the early aggregation gear used ADSL (asymmetric DSL) for transport over copper, but slow non-duplex speeds have really hampered widespread acceptance of ADSL-based products. New VDSL technologies are cost competitive with old ADSL, but offer much higher bandwidth. VDSL is capable of going as fast as 52 Mbps upstream and 6.4 Mbps downstream, yet early efforts at standardization are looking at about 26 Mbps up and 3 Mbps down. Symmetric VDSL, also under development, is likely to be duplex 10 Mbps–enough bandwidth to crank some serious ROI via services like VOD, high-speed Internet, lifeline voice, VPN access, and inter-facility LAN access...just to name a few.

But for carriers to adopt new VDSL technologies, they'll need to be assured that their investment isn't an empty one, and that VDSL technology as a platform has potential to grow and evolve. This is where standards come in–carriers will NOT buy VDSL gear until fears are allayed through standardization–and the momentum for VDSL standards is just now picking up steam.

The leading standards movement for VDSL is a spin-off from the influential Full Service Access Network, or FSAN. Called the FS-VDSL Committee, the body is really carrier-driven, with support from large international carriers like Korea Telecom, BT, Bell Canada, Qwest Communications and Deutsche Telekom. But it's the vendors who really are driving initial momentum for a set of VDSL specifications for network gear, and much of their early work has been to enable the uninterrupted flow of Ethernet traffic over copper loops. While most DSL services are based on an ATM interface, the ability to seamlessly carry Ethernet traffic will be essential to the success of VDSL, as millions of current business and residential users already employ Ethernet framing.

With that in mind, the FS-VDSL group recently met outside of Denver to demo some early VDSL gear and get started on a standard set of specifications due later this summer. At the meeting, a newcomer to the VDSL chip market surprised the group with some remarkable results. Fremont, Calif.-based Ikanos Communications showed a VDSL chip design called VDSL-DMT with 50 Mbps download and 26 Mbps upload speeds. In demonstrating transmission over 1,000-foot runs of copper, the Ikanos chip also showed that typical variable-frame Ethernet traffic could potentially reach 49.5 Mbps downstream and 28 Mbps in the return path.

Also showing off at the FS-VDSL meeting was Tut Systems, one of the first companies to tailor aggregation equipment specifically for the MxU market. Tut has already evolved its IntelliPOP line of service gateways to include VDSL technology, with the release of the IntelliPOP 5000 platform. And at that March FS-VDSL meeting, Tut demonstrated vendor partner interoperability by showing advancements to its next-gen IntelliPOP 8000 platform.

By integrating Tut's proprietary SIGMA Signature Switch with the 8000 platform, Tut showed the 8200 central office fiber switching system and the counterpart 8100 Broadband Services Nodes, which can deliver up to 240 VDSL subscriber lines from a single carrier-class chassis. For Tut, the new IntelliPOP 8000 platform is aimed at carriers as a complete cable replacement package, and should be available just as the cable-telco race for new services begins to heat up.

"We have learned over the last 10 years what it really takes to run data over any unknown copper pair," explains Mark Carpenter, executive vice president of development and marketing for Tut Systems. The evolution to VDSL will mean delivering more than data over that copper pair–video and managed data are sure to follow as more robust VDSL gets specified by the FS-VDSL group in the near future.

Not surprisingly, the early market for VDSL products has found a home in the Far East. Korea, where the percentage of DSL infrastructure is unmatched in the world, is a prime target for new VDSL gear. Korean vendor Gigalink is one equipment company gravitating to VDSL, offering multiple MxU platforms based on VDSL technology.

Other vendors are part of the VDSL fray, and most of these early entrants have technologies that bridge legacy and new IP infrastructures–an important qualification for carriers going forward. Advanced Fibre Communications, which recently acquired access gear maker AccessLan, touts the multi-protocol Tellium 5000 edge switching platform, most notable for its ability to translate legacy ATM functionality with next-generation transport protocols. Similar technologies from companies like ARESCOM, VDSL Systems and ZyXEL combine Ethernet functionality with traditional transport protocols like ATM for access in the last mile.

In the future, what's becoming clear is that platforms combining legacy and copper loop transport with Ethernet and IP are necessary to serve the majority of the MxU market, and of the biggest network players in the world, Cisco seems to fully realize this. Cisco is alone in targeting a hybrid VDSL-Ethernet platform specifically at the MxU market. Through a host of LRE (Long Range Ethernet) technologies, Cisco offers providers a way to serve virtually any multi-tenant environment, be it a hotel with 1920s-era copper infrastructure or business complexes employing modern Ethernet networking architecture. Through a combination of Catalyst brand LRE switches, LRE CPE devices and POTS splitters, Gigabit interface converters, and even Aironet wireless devices, the Cisco platform can be applied to applications that run the MxU gamut, and uses base VDSL technology to route signals over copper in the last mile.

On the other side of the vendor aggregation coin are the pure-play Ethernet companies, which are busy pushing Gigabit Ethernet technologies to unheard-of speeds. Ethernet gear makers are apostles in the movement to adopt Ethernet wherever and whenever, and they're coalescing under the banner of the Ethernet in the First Mile Alliance (EFMA) to convince others of their all-Ethernet vision.

Alliance members include vendors like Cisco, Intel, Ericsson, Extreme Networks and World Wide Packets, and the group is in the early stages of creating a set of platform specifications for the technology. Recently, the group brought an introductory proposal to carriers as a replacement platform for legacy ATM switching. But carriers sent the group back to the drawing board, so to speak, with concerns about Ethernet's inability to guarantee service quality during transmission. However, the EFMA could have a standard ready to take to carriers later this year, which might go a long way toward convincing them that a transition to Ethernet is inevitable in their transport networks.

"I think that for (the carriers) it's an eventual transition, but it's going to be slow," says Amy Cravens, an MxU analyst with researcher InStat/MDR.

But in the carrier world, at least in the near term, doing Ethernet involves more than just IP, because of all the legacy transport protocols that exist on their networks. Even though subscriber traffic begins and ends as IP when using Ethernet, in the telecom world that traffic must ultimately travel over a variety of protocols–like point-to-point (PPP), ATM and Sonet. New technologies that provide for a migration to all-IP in the future must have legacy considerations, which is why carriers' next purchases will be hybrid VDSL-Ethernet products...they have to be for carriers to leverage what they currently have running from core to edge to subscriber.

And what's the biggest obstacle to lighting up all the MxU properties for broadband services so far? Some MxUs are flush with old copper wiring, while some properties (especially in metro areas) have Ethernet runs coursing through their walls. If carriers begin to put aggregation equipment that can handle both of these environments out closer to the MxU properties themselves, lighting them up is the next logical step.