In the following guest post, TC2's London-based managing director Ben Fox continues his comments about the Mobile World Congress in Barcelona.

Besides the increasing momentum for establishing LTE as a global mobile broadband standard, the other very interesting announcement from Barcelona came from Verizon Wireless and Skype. The two companies reported that, beginning in late March, Verizon Wireless will allow subscribers to use Skype's IP voice application over its network.

By downloading the Skype application to their Verizon Wireless smartphones, end users will be able to call other Skype users around the world for free. This represents a significant change of heart from a carrier (and indeed an industry) that to date has been very territorial in terms of allowing users to take advantage of applications that could reduce its own revenue.

So what's in it for Verizon Wireless? The answer is data revenues. As I noted last month, Verizon Wireless' strategy is currently focused on driving the penetration of data services. And for Verizon Wireless users to be able to use Skype, they will need to subscribe to a voice and data plan.

No doubt Verizon Wireless has calculated that the lost voice revenues from Skype usage will be more than offset by the increased data plan revenues and by the increased adoption of the smartphones that will be needed to use Skype, which typically drive increased average revenue per user (ARPU) compared to more basic devices. Perhaps they're even anticipating a further compensation for lost voice revenues in the increased revenue from the higher ETFs associated with these types of devices and plans!

Skype and Verizon Wireless stated that their agreement is "exclusive", although it is unclear what that really means, since the Skype application has been available for some time on AT&T Mobility's network via the iPhone. Perhaps Verizon Wireless's thinking is that AT&T users have so far only been to use Skype over WiFi, not 3G, access. But a version that operates on GSM/HSPA is supposed to be pending.

Of course Skype does not tend to be an application that large enterprises actively roll out and support for their end-users, so this might have limited initial relevance to business users. However, using Skype (and similar VoIP applications) on a smartphone whilst roaming on WiFi networks to save money, compared to paying $1+ a minute to roam on a GSM network in a foreign country, is a far more intuitive and "traditional" phone experience than using a soft phone (Skype or otherwise) on your laptop. So there is certainly money-saving potential in this area for enterprise customers.

But the more important takeaway for the business user from this Skype/Verizon Wireless announcement is the continuing shift in focus for wireless carriers all around the globe from voice revenues to data revenues, driven by the evolution of all cell phones into smartphones. Similar announcements in 2010 already include Google's Nexus One, Windows Phone 7 for mobiles, the Wholesale Applications Community mobile application alliance, and carriers announcing increased after-sales support for smartphone users. These all demonstrate the importance of smartphones to the carriers and the pressure that all carriers, manufacturers and software developers are under to get ahead of the pack and differentiate their smartphone service offerings.

Although much of the initial adoption of the more innovative services (such as the iPhone and Apple's application store) has been driven by consumers, the carriers, manufacturers and software developers now have business users firmly in their sights. Google has already been talking about a version of its Nexus One aimed at business users, and in the UK, Vodafone is specifically targeting business users in its iPhone adverts.

The bottom line is that we are already seeing business end-users at our clients pressuring their telecoms departments to offer an increasing array of smartphone devices, not the least of which is the iPhone, as well as a rich variety of new services and applications. A BlackBerry that only provides voice calling, email, calendar and contact directory functions is no longer enough! Mobile device management, rather than getting easier, will become exponentially more challenging.

On the other hand, when the world ultimately moves to a single global mobile standard -- LTE -- the job of managing your enterprise's global mobility requirements should become somewhat easier, though I'm afraid that the impact of LTE will be a ripple on the ocean compared to the tsunami of challenges presented by user demands for an ever increasing range of smartphone applications and functionality.

For as long as anyone can remember, AT&T has been the carrier that's held on the longest to legacy products. In recent times, AT&T has been happy to let users continue to subscribe to its global business dial-up Internet service until they're ready for AT&T's broadband virtual tunneling service. AT&T has also let corporate WANs sail along on frame relay without putting out a marker on ending frame relay orders or contract renewals, as first Sprint and then Verizon have done.

And there will probably be some companies using AT&T for straight-on, long-haul, T1/T3 private lines in the year 2030 just as in 2010.

So it was jarring when AT&T grabbed some publicity at the end of last year with what looked like a request to the FCC to retire the public switched telephone network. AT&T severing itself from POTS, or Plain Old Telephone Service? It didn't seem right.

Understanding AT&T's about-face on maintaining legacy networks requires an understanding of the concept of financial harvesting. One of the best illustrations of harvesting came during an odd period in telecom carrier finance back in the mid-1990s -- basically a few years before and after enactment of the Telecommunications Act of 1996.

Back then, the Internet was emerging in its browser-enabled incarnation as the World Wide Web, the corporate telecom deal culture was thriving, and TV airwaves and telemarketing lines were buzzing with pitches for 10-cent, 7-cent, and 5-cent long distance minutes. Yet when AT&T held its quarterly earnings conference calls, the first question Wall Street analysts would invariably ask was why AT&T had only raised its basic, no-plan long distance rate from 25 cents a minute to 26 cents, not 27 cents. Wouldn't Aunt Mary from Kalamazoo, who would never in a million years switch to MCI or Sprint, overlook a larger increase and happily pay the bill?

AT&T was essentially harvesting its no-plan customers for a revenue stream for as long as these customers existed. And the analysts, almost to AT&T's annoyance, wanted them to do even more of it. Not until somebody rang a bell around 1997-1998 and the analysts realized that AT&T had to compete elsewhere for voice and data business did the harvesting issue start to fade.

Now look at AT&T's situation today. AT&T Mobility is thriving and sales of the iPhone are zooming. AT&T's share of the enterprise networking market is basically what it's been for years, and with the decline of Sprint it's even threatening to establish a virtual duopoly with Verizon.

But AT&T's consumer telephony business seems to be slipping away. Like the incumbent local businesses of Verizon and Qwest, AT&T is losing residential landlines at a remarkable pace, now edging close to 1% a month. The result is the reverse of harvesting: AT&T says it's bleeding from the need to maintain all-copper loops in a mass market that's beginning to reject them, and it wants to get out rather than stay in as long as possible.

Of course, AT&T, Verizon and Qwest get some of their landline customers right back when the same households buy their broadband packages. And the broadband and telephony customers that the cable companies win instead represent fair-and-square marketplace losses for the telcos. But that only seems to reinforce the reverse-harvesting instinct, feeding AT&T's argument that it needs to massively shift resources.

Aside from the fact that AT&T in the meantime hasn't lost its near-monopoly dedicated access business in its local territories, here's the problem with simply accepting AT&T's conclusion that the PSTN should be retired: From a business user standpoint, there's a little more to the legacy network than consumer migration to cell phones and broadband. As our friend Eric Krapf of VoiceCon/NoJitter has already pointed out, AT&T hasn't quite defined the PSTN to be retired, leaving us to assume they mean everything. But what about Class 5 switches and their unique functionality that's still in the process of being emulated in various VoIP services? What about the fact that many of the poles, trenches and conduits are the same for both older and newer services?

And what about all the people who make calls to the businesses who make up the enterprise market? If they don't have a cell phone or a broadband triple-play package, are they out of luck, and your business out of a sale?

Many business customers would benefit enormously if AT&T does what it says that PSTN retirement will free it to do: help create universal, affordable broadband. Widespread remote-agent call center functionality, broad-based telecommuting, and many facets of unified communications do rely on a pervasive broadband network.

But it's important to realize that AT&T is responding in a classic "lobbying" fashion to the current broadband stimulus, which requires the FCC to develop a national broadband plan. In effect AT&T is saying that if there has to be universal broadband, there can't be universal narrowband. That's either one of those unintended consequences that can result from regulatory initiatives, or an unproven assertion of investment motivation by an experienced Washington player.

At this point I think there are two key things for corporate telecom professionals to remember. One is that AT&T, with all of its legacy pressures and characteristic behavior patterns, has many piece-parts. In this case we're clearly talking about an AT&T whose heart is the former RBOC SBC, not the former interexchange giant.

The other is that some of the regulatory nuance got lost in some of the initial reports. What AT&T is supporting, in the context of a question posed by the FCC, is the initiation of a Notice of Inquiry about the PSTN, which is a more preliminary proceeding than even a Notice of Proposed Rulemaking, which itself has many procedural checkpoints before it results in new rules. It's unlikely that AT&T really wants to lose all its POTS customers in one fell swoop right now. More likely, it's just drawing a line in the sand.

So we'll have some time to watch this, and the market will invariably shift more along the way. Let me know if you have thoughts of your own on this fascinating matter that threatens to turn the tables of telecom history upside down.

Avaya came out with its product roadmap for the acquired Nortel base this week, and you could summarize it like this: We'll give you lots of space at the beginning of the year, provided you're playing ball with us by the end of the year.

Avaya is cutting off nobody in the Nortel PBX base -- at least, nobody whose Nortel product hadn't already begun down the end-of-sale, end-of-support trail. And it's declaring its own end-of-sale only on some supplementary products like the Nortel MCS 5100, a multimedia communications server providing audio and videoconferencing, collaboration tools and the like.

On the core question of what to do with Nortel's IP PBX flagship, the Communication Server 1000, Avaya's immediate plan is to follow on Nortel's post-bankruptcy Release 6 with more upgrades of its own over the next 12-18 months. But this looks like a time-delimited strategy.

Some experts think there will be two more CS 1000 full releases over the 12-18 month period. Others, such as Stephen Leaden, who gave an excellent webinar yesterday on the Avaya-Nortel roadmap for our friends at The Voice Report, thinks there will be only one. After this initial year or year and a half, Avaya has made it clear that CS 1000 users will have to begin "layering on" Avaya's own Aura platform to stay current.

Aura is Avaya's new unified communications architecture that incorporates a SIP Session Manager to handle supported applications, including SIP trunking carrier services. As we've discussed, those services can eliminate many traditional voice trunks in favor centralizing voice streams over a corporate MPLS network with an expedited-forwarding, or real-time, class of service, and then out to the public as necessary (or the reverse in the case of calls into contact centers, including those taken by remote agents logged onto the network).

But as you can imagine, the common challenge in all of the Nortel users' roadmap options is enterprise capital availability. Leaden explained that during 2010, Nortel users theoretically have three choices -- wait and consider, begin investigating an investment in Aura (which was designed for interoperability with other vendors even before Nortel's downfall), or begin due diligence on a move to another vendor (such as Cisco, Siemens, etc.). But by 2011 that's really squeezed down to the last two options due to the timeline Avaya laid out.

There's a lot more to the Avaya-Nortel roadmap, and I encourage you to check out the replay of the Voice Report webinar especially to learn about the other products in play. What I personally found fascinating were repeated references to exactly how Avaya will be presenting investments in the Aura platform to Nortel users. It's clear that Nortel users will be hit with ROI and payback analyses, and that Avaya will load in benefits that are dependent on other parts of an enterprise's telecom "ecosystem."

Leaden listed not only items such as centralized voicemail and unified messaging but also the trunk consolidation benefits from SIP trunking as likely inputs into Avaya ROI models. No doubt Avaya will use rosy ROI assumptions to push Aura on the Nortel users, including theoretical savings from the maximum amount of eliminated or consolidated telephony infrastructure.

Of course, it's ultimately up to AT&T, Verizon or others to propose such complete exchanges of traditional rate elements for dynamic VoIP call allocation in their own SIP trunking proposals. But think about the size of Nortel's base. Avaya's plan means that a huge number of telecom buyers will be getting proposals at a time of unusual urgency -- after their major equipment supplier has been bought out of bankruptcy -- in which the new vendor will be highlighting the maximum savings that a carrier should be offering them in service of the new equipment vendor's roadmap.

An insta-poll taken during the webinar showed that 48% of the attendees with Nortel gear (and there were at least 230 live users on the conference) are initially inclined to go the "due diligence, find another vendor" route. So I'm sure Avaya won't be shy about its ROI claims for Aura, including what it thinks the carriers can do!

Like the pressure-from-below that I recently highlighted in the smaller carriers' discovery of a potential gold mine in SIP trunking, this Avaya-Nortel transition will thus provide another pressure point on the big carriers to make solid VoIP/SIP trunking deals. At some point soon, a little roadmap discussion of your own with current and prospective carriers on this matter could prove quite rewarding.

A growing number of large enterprises are reporting various experiences in sounding out and testing AT&T and Verizon on SIP trunking services. The big carriers are moving at sometimes uncertain speeds to completely leap into the market with aggressive proposals that actually leverage the replacement of legacy elements in their own incumbent infrastructure.

But there's no question about the speed of SIP trunking's ramp-up at the other end of the carrier market -- the small-business CLECs and alternative carriers. One after another they are jumping head-first into the SIP trunking pool. And if past experience with new carrier products is any guide, you'll be hearing about sales calls from these companies to your business units and branch offices, no matter how many protections you have in place for who's authorized to buy telecom services.

A key point came in early December with the announcement of SIP trunking from XO Communications. XO is a fixture in the telecom industry that's hung on through Chapter 11, mergers, technology migrations and strategy shifts. It's primarily seen in the small business market, although it has a clear strategy to move substantially into the middle market and occasionally provides circuits or hosting to large enterprises (and would like to do more).

But XO is hardly alone. Individual companies with no particular play (yet) in the enterprise market, and much less of a legacy in the 1990s CLEC boom and bust, are clearly putting SIP trunking front and center.

Speakeasy out of Seattle, which began as an Internet cafe company and is now actually part of Best Buy, offers an "Integrated Voice" package that neatly offers SIP trunking provided you have an IP PBX at a centralized voice location (or old-fashioned PRIs if you don't).

Cbeyond out of Atlanta offers what it calls its BeyondVoice with SIP service, boasting its early role in helping develop the "SIPconnect" standard. SIPconnect, as we've previously discussed, is a kind of global certification label that IP PBX makers and carriers can use to specify that they adhere to a certain approved subset of SIP procedures, and may be appropriate for locations without large-enterprise, mission-critical requirements (like full-featured contact centers) or strict testing requirements.

And our friends at Network World just reported on the new "Dynamic Office" service from Windstream Communications based on SIP trunking. This one is particularly intriguing because Windstream is actually an independent ILEC -- an incumbent, not alternative, local carrier based in North Carolina that serves areas that the big incumbents either never served or offloaded.

Clearly there are some cautionary items with regard to these new services. Most small SIP trunking carriers will in fact rely on SIPconnect or other methods to ensure compliance rather than engage in individual carrier-PBX certification tests. Some of them don't offer MPLS, so what you're basically buying is integrated voice-data access over dedicated Internet lines to bring voice streams from branch offices to the SIP trunking core and out to the public network.

And you have to be aware of any alternative carrier's financial status -- XO, for example, has an odd set-up where it's 89% owned by Carl Icahn and his affiliated companies. It's still not really profitable and probably not independently viable without this single backer, which doesn't need to be a large concern until you start using them strategically rather than tactically.

But all of these SIP trunking carriers are leveraging the now solid penetration of pure IP PBXs from Cisco, Avaya, ShoreTel and others. And they're certainly less beholden than the big carriers to separate voice trunks, unconverged dedicated access lines, and old ISDN infrastructure. It's great to see them pressuring the market from below, and that can only bode well for the acceleration of SIP trunking into the large enterprise market in a truly competitive, financially compelling way.

Most corporate telecom managers have a pretty big to-do list for 2010. For many of you, that list includes deciding what to do about your Nortel voice equipment, and when to do it.

Last Friday, Avaya closed its $900 million deal (including debt) to buy Nortel Enterprise Solutions out of Nortel's bankruptcy. Avaya then scheduled a January 19 video webinar to explain its roadmap for the combined product set. But prudent managers are already laying the groundwork for communicating throughout their telecom and IT organizations the directions the combined Avaya/Nortel may well take.

Obviously Avaya is in the driver's seat, and it's helpful to know their corporate thinking as well as their product leanings. Avaya, which is an enterprise equipment/software pure play that was formed out of successive spinoffs from legacy "Ma Bell" type organizations, is currently privately held. But almost everyone believes that Avaya's private-equity owners, Silver Lake Partners and TPG Capital, want to bring the company public again as an exit strategy for themselves.

With Cisco gaining rapidly in voice market share, the Nortel buy was necessary for Avaya to ensure that it comes to the financial markets as the No. 1 vendor for corporate voice gear and unified communications. In particular, as PBX market share guru Al Sulkin has explained at recent VoiceCon events, Avaya/Nortel can still lay claim to dominating the contact center market, where enterprises have been less eager to move to new vendors. Avaya and Nortel still add up to half the market for call center premises switches/software, with Cisco and Genesys taking about 15% each and others battling for the rest.

So Avaya is hardly likely to thumb its nose at the big Nortel base during the period it presents its case to the financial markets (and it is hiring 6,000 Nortel employees). But promises to maintain duplicative product sets for a long time won't earn Silver Lake/TPG a big stock market payday either.

Many if not most observers draw a distinction between users of Nortel's venerable PBX product, the Meridian 1, and its next-generation IP PBX platform, the CS (Communication Server) 1000. Some observers are advising Meridian 1 users to order crash kits and all the spare parts they can find, although the Meridian installed base is believed to be big enough in enough important places for Avaya not to do anything hasty.

As far as the CS 1000, Nortel made a show earlier this year, even after its bankruptcy filing, of introducing a comprehensive Release 6 with notable features such as, for big financial institutions in the capital markets, a SIP-based turret system. Some PBX industry watchers are speculating that Avaya will likely provide full-scale support for CS 1000 for 2-3 years, although that presumes being current on the releases.

All this is taking place at a time when Avaya is rolling out its own distinct architecture called "Aura." It's a sort of bridging technology where Avaya uses SIP as a session manager to interoperate with its own and other (including Cisco) gear across multiple sites and a wide range of applications, including many that are critical to call center managers. But how far this goes in pulling Nortel platforms into the fold permanently -- or, alternatively, drawing Nortel users to core Avaya platforms -- is something Avaya officials will have to explain in their January 19 show.

You could say that in the Nortel situation we have a "consequential bankruptcy," one that isn't simply a reorganization of the company but a wholesale reordering of the market. In Internet discussions, many users have actually lauded parts of Nortel for engineering prowess that they view as superior to Cisco's (for some things) and Avaya's (for others), and ex-Nortel and Bay Networks employees can be found saying the same thing. But the center didn't hold, and here's a hat tip for an old colleague of mine at the trade publication Network World, Jim Duffy, who earlier this month wrote a very informative (and morosely entertaining) article documenting the systematic dismantling of Nortel in bankruptcy.

In short, there was something about the organization as a whole that just didn't work once the new IP era came along. As we say good-bye, apparently for good, to the venerable old "Northern Telecom," outside players will be writing the script for the users of its products, starting very soon.

When you go to install a new wide-area network technology that involves the interaction of carrier trunks with your premises equipment, do you:

a) trust statements of compliance by all parties with the technology's open standards;

b) look to the carriers and equipment vendors involved to certify that each other party's specific service or gear works with theirs, or

c) do you own interoperability tests?

This question is very much alive when enterprises go to buy "SIP Trunking" services from carriers. These services essentially make VoIP full-featured for corporate on-net and off-net calling, and reduce or eliminate dedicated local and long distance trunks in favor of dynamic allocation of packetized voice streams over data networks such as MPLS real-time classes of service. To do so, SIP Trunking relies on a set of IP standards that tell carrier networks, PBXs and other gear how to interpret call set-up instructions, signaling and other commands.

But like many standards, the Session Initiation Protocol itself and the SIP Trunking methodology that derives from it can be subject to interpretation and options. That can make things dicey when you consider what it's replacing -- TDM voice trunks, often into mission-critical call centers with call-transfer feature functionality, PRIs, national enterprise dialing plans, and the like.

If anything, SIP is particularly prone to this standards-extension challenge. At one of my VoiceCon sessions on SIP trunking earlier this year, one of the panelists said he had done a word search of IETF RFC 3261, the main (though not only) SIP standards document. He found that the word "may" showed up 378 times in the document. So much for a "standard" telling everybody in the industry exactly what to do!

The decisions that each vendor makes around these SIP choices is critical to what the industry labels interoperability but really means the kind of feature transparency that enterprises must have. To bring it home to many corporate telecom managers, there are functions such as "SIP Refer" and "SIP Redirect" defined in the standard. If the implementation of these items doesn't emulate what call center managers have traditionally known as AT&T's Transfer Connect, Verizon's (previously MCI's) Take Back and Transfer, or Sprint's Agent Transfer, no amount of theoretical cost savings is going to be worth it for most enterprises.

When you go to investigate SIP Trunking and ask about this kind of interoperability, you're bound to hear about the SIPconnect certification process established since 2005 by the SIP Forum's IP PBX and Service Provider Interoperability Task Force. Any vendor's compliance with SIPconnect 1.0 or the emerging SIPconnect 1.1 guarantees a certain degree of out-of-the-box interoperability.

And certain specialized, CLEC-type carriers have built a business around SIPconnect. They go primarily to smaller businesses and tell them that their locations can probably go straight to SIP Trunking and full-featured (for them) VoIP even with a wide variety of telephone equipment, including many older TDM switches.

But for larger customers, Verizon and AT&T make a point of doing their own SIP interworking tests on IP PBXs and then publicly "certifying" specific key vendors such as Avaya, Cisco and Nortel on their flagship families of IP communications gear. They don't just rely on SIPconnect, partly because SIPconnect makes certain choices on SIP Trunking options that may not agree with some enterprise advanced features.

That's why, when you go to Verizon's page for IP Trunking Services, you'll see "fact sheets" and "solutions briefs" speaking to relationships they've established with Avaya, Nortel and others to bring SIP trunking to the market. These are really references to interoperability tests but speak to the importance attached to knowing that specific gear provides a match to a carrier's SIP Trunking implementations. (By the way, this will still be as key after Avaya completes its acquisition of Nortel, as these separate platforms remain widely deployed.) Some of these tests apparently took quite some time and a great deal of communication among the vendors away from the standards forums.

Even beyond that, the Verizon and AT&T panelists at my sessions have made the point that large customers can also come to their own labs to do their own tests. In this way, the ramp of SIP Trunking reminds me of the early days of MPLS, including in its original guise as IP-enabled frame relay, when customers felt they had to test older versions of Cisco IOS software releases to see if they would be supported over these new label-switching protocols.

Basically, the larger and more complex your organization, the more legwork is invariably involved with SIP Trunking, despite its roots as an IP standard. At some point the legwork factor will be reduced, especially if the service takes off in the marketplace, although there are plenty of signs that the major carriers would prefer to carefully manage this transition away from their traditional and profitable local trunking services. It's an arc we'll be following closely as the SIP Trunking story continues.

I'm in San Francisco for the fall version of the VoiceCon conference, which I regularly attend and speak at. Over the past two years, one topic in particular has ballooned in interest at the spring and fall VoiceCon meetings: SIP trunking. That's a service you can purchase from carriers that takes the Session Initiation Protocol now used for VoIP call set-up and other signaling functions, and rides it over specific data networking links such as MPLS or dedicated Internet.

The ultimate hope of SIP trunking is that by purchasing a certain number of ports for concurrent calls based on a study of your peak voice traffic, and having the bandwidth for your VoIP dynamically allocated across your network, you can eliminate many if not all of the elements of traditional telephony that have remained in place under more rudimentary VoIP implementations. Among these are some of the stickiest in price in an otherwise deflationary industry: local telephone trunks and PRIs.

You may still have to pay what is in effect a toll for the switched end of a call (often the origination of a call to a contact center) as part of the SIP trunking package. But other pricing parts of the separate voice-network equation drop away, typically in favor of a voice-grade class of service on the MPLS network you may have installed anyway, and the potentially very scalable concurrent-call rate element.

While the interest in the service is real -- and justified, because SIP trunking is being sold and installed by a number of carriers -- it's fascinating to note the different perception of the broad user base and the carriers as to its practical availability.

I shared a panel today with Alla Reznik, Verizon's director of Global Advanced Voice Services, in which we discussed SIP Trunking and other services with moderator Eric Krapf, editor of NoJitter.com and long-time organizer of VoiceCon. Alla has served on my own VoiceCon panels in the past on the same subject, and she is one of the most conversant people on the subject. There's no question from her presentations that Verizon sees SIP trunking as a core offering in both national and, ultimately, international rollouts of integrated voice and data networks.

But in general discussion at VoiceCon, including in other sessions, it's clear that many users feel that the major carriers are holding back on them on SIP trunking. Account teams seem reluctant to bring it up, we repeatedly hear, and the first pass at asking about availability and pricing can be rocky.

Some of this is undoubtedly because many carrier reps really don't know much about the product. But the user perception is that as the main national enterprise carriers have merged back into combined local and long distance behemoths, they've become loath to present a product that may cannibalize the local telephony trunks from the old "RBOC" sides of their business.

Our experience at TC2 on this issue of re-monopolization is that there are two very different sides of the same coin. In the case of SIP trunking, the very fact that the two largest carriers have a huge installed base of local telephony to protect can actually be turned against them, if you play your cards right.

Sure, if you talk to a single carrier, and you ask in isolation to get a service that will wind up earning that carrier less money, you are likely to get the foot-dragging type of response that has bedeviled telecom users, in one way or the other, for decades.

But we are beginning to find that SIP trunking as an additional service is one of those tools that carriers in a competitive situation can positively employ to try to win your business. Say two carriers are bidding on a national data network that also prospectively can be used for voice and video. Now add the fact that if the user does go forward with convergence using the service, the losing bidder will not only lose the "long distance" business of that company, but also the local telephony part of that company's business in their native territory.

Now the need to protect an installed base is being leveraged against both carriers. So at least one of them may have to respond -- either with a competitive VoIP service that makes the other carrier lose their "POTS" business with no compensating new business, or with a better bid on the national network itself.

Clearly, many variables go into this kind of situation. In the real world, many enterprises are not willing to give up their local trunks because of issues surrounding E911 and diversity. But for some large enterprises, the greater number and uses of local trunks, T-1 access lines to long distance POPs, and high-capacity virtual LANs and WANs from SONET to Ethernet at numerous locations gives them a lot to play with. That means that even a partial elimination of local infrastructure that used to have to go to the incumbent carrier in each territory can have a big payoff.

This keen interest in SIP trunking provides a notable example of the "Jekyll and Hyde" carrier behavior that my colleague Ben Fox has discussed in his own NoJitter article, There Is Only One Sure Way To Get The Lowest Possible Telecom Prices. In fact, it's a multiplier effect: in this case, the tension between a legacy base and a next-generation service can swing in completely different directions depending on how competitively you are presenting yourself to the carriers.

We'll be watching to see how quickly the SIP trunking trend accelerates, and how well enterprises are effectively using competitive leverage to make it go. Even though many people in the big carriers don't want to acknowledge it, the carriers' businesses is changing, and if you're in a position to force them to realize it, you're probably doing something right. Getting yourself into that kind of position is what much of telecom procurement for the long run is all about.

Nortel Enterprise Solutions is going into the hands of its onetime arch-rival for voice premises equipment, Avaya.

That result was assured with Monday morning's announcement that an auction for the Nortel enterprise unit -- a key element of Nortel's bankruptcy proceeding -- had been completed. While not explicitly announced this way, it's widely believed that the Siemens enterprise unit bid up Avaya's original offer of $475 million over several rounds before letting Avaya have it for $900 million.

Avaya's clinching of the Nortel prize keeps intact many of the expected user impacts of the impending marriage of the one-time No. 1 and No. 2 U.S. PBX vendurs. Avaya gets feet on the street through Nortel's extensive distribution network, although much of that network is also now invested in the enterprise voice and convergence products of Cisco. Indeed, Cisco and Avaya are now set up as the Coke and Pepsi of the enterprise voice gear market, with the possibility of far more concentration than this market has ever seen in the past.

Acquirers often are ruthless wielders of power, deciding which of the acquired company's products, employees and projects to keep and which to get rid of. And let's be fair -- it's clear that Avaya would be justified in doing some rationalization. Possibilities include:

-- A convergence-products alliance that Nortel had with Microsoft has never really borne fruit, especially since Microsoft is pursuing enterprise voice in an explicitly Windows-based softphone environment, and that alliance may go.

-- Avaya may also see no value in the longstanding problem Nortel has had in making sense of its data switching product portfolio from the basically botched acquisition of Bay Networks in the 1990s.

-- Of perhaps more concern, support for some Nortel products (or some distributors) may change or drop, a concern being made explicit by Verizon as one of Nortel's legacy "RBOC"-type distributors.

Excellent discussions of these detailed matters are taking place with our friends at NoJitter.com; I particularly like a post by Allan Sulkin called Questions re the Future of Nortel ES.

But from a strategic standpoint, one thing that I think enterprise telecom managers should be asking themselves is what kind of role voice and unified communications equipment should play in managed services procurements going forward. Many corporate PBX footprints are very scattered and diverse based on long-lived legacy considerations in various business units, geographic divisions and even individual locations. But if Cisco and Avaya go head-to-head as the dominant players, we know that this can be played to strategic advantage going forward.

From a data perspective, obviously most companies are "Cisco shops." But from a VoIP/unified communications standpoint, holding out a large chunk of business for archrivals to bid on could be in the offing. Thus, the looming Cisco vs. Avaya war could be seen as a reduction of choice -- or, alternatively, a big opportunity for savvy enterprise users, especially when you consider that managed services procurements often offer the best transport pricing. Much remains to shake out, but we'll be watching this closely.

You may remember that earlier this year, Avaya struck a deal to buy Nortel's enterprise division out of bankruptcy for $475 million. But the process has always been set up to make Avaya's offer a "stalking horse." That means that Nortel's bankruptcy trustee has always planned ultimately to hold an auction to see if anyone wants to outbid Avaya. That auction is due to take place this Friday, September 11.

In a narrow sense, the auction is obviously key for Nortel users. For its wide base of voice equipment users -- including many companies that may use other vendors, but have lots of Nortel installations too -- the question is whether Nortel products will be actively supported, or slink along to end-of-support and ultimately end-of-life status.

Siemens' enterprise group, which itself has had a rocky few years, is mentioned as a possible bidder, as are some less likely players. But you do have to remember that much of the traditional PBX industry has already been sold out (in full acquisitions or joint ventures) to various private equity groups, who are all managing debt loads and may be wary of taking on further leverage to expand by acquisition. So Avaya could walk away with the prize with little or no further effort.

But in a larger sense, the question is whether the PBX or enterprise/unified communications industry (by whatever name) is heading inevitably for duopoly, like so many other industries. If no one outbids Avaya, then Avaya -- the ultimate successor to the original AT&T PBX business -- will gain Nortel's big if somewhat degraded distribution channel. That will leave two major players: Avaya, the champion of the traditional phone switch business, and Cisco, the behemoth data networking company that successfully clawed its way into the premises voice communications market. For all intents and purposes, enterprise managers going forward would be left with a binary choice on their strategic unified communications partner.

Does that simplify matters in the historically fractured voice equipment market, or is it an anti-competitive warning shot? And should the government step in?

That's a fascinating parallel with the emerging situation of AT&T and Verizon in the network transport (and managed) services market -- one that would have been unthinkable until recently, given the dozens of players that have given the PBX market a fair shot. Right now there is a lively debate on the matter hosted by our friends at NoJitter.com. Kind of a portal to the debate can be found in one of NoJitter editor Eric Krapf's recent e-newsletters. We'll examine the matter more after the results of Friday's auction are known, and we look forward to your views as well.

For all the changes in the telecommunications industry, almost all enterprises still make their primary "long distance" provider the descendants of the original AT&T, MCI or Sprint.

The same cannot be said of the voice equipment industry. You can draw a straight line between the entry of Cisco into the IP PBX market and the events of the last few days, where Avaya has offered $475 million to buy Nortel's enterprise unit out of bankruptcy.

The traditional leading players in the PBX industry are coming together to compete with a new player, much as if the legacy AT&T and MCI had to come together to compete with a new, fully successful long distance entrant that actually made it to the first tier (which never happened).

Of course, it was Nortel's cost structure in a recessionary environment that was the proximate cause of its bankruptcy filing at the beginning of the year. But looking at the big picture, it's worth remembering exactly who Avaya and Nortel are.

Avaya is the descendant of the old AT&T PBX business, when AT&T, even divested of the "RBOCs," was still a combination of a long distance provider, a PBX maker, and a seller of central office switches to phone companies. On the PBX side, AT&T typically sold direct into corporate accounts. This same business eventually became Lucent and then further spun off into the separate Avaya (because Lucent management succumbed to the siren song of the "carrier" business when people thought hundreds of alternative carriers would succeed).

Nortel is the old Northern Telecom, which typically sold PBXs indirectly into enterprise accounts, through RBOC account teams and certain specialized channel players. This method of approaching the market changed from time to time, but was the time-honored way they did business.

It's now as if the market is pulling together these venerable players with opposite channel strategies to set up an ongoing challenge with voice communications entrants from the data world. Several of the columnists at the NoJitter.com VoIP website are also noting that the smaller, traditional PBX players are going to have to combine if they want any traction at all in the new market.

How Microsoft with its fully software-based softphone applications reacts after having something of an alliance with Nortel also remains to be seen -- and it could be a big player in its own right. And what happens to Nortel's data equipment that comes from the legacy of the original Bay Networks also remains to be seen.

It's not 100% certain that Avaya will actually buy Nortel. The shape of the bankruptcy proceedings and the terms of this "stalking horse" offer could make it the opening shot in a competition. One way or another, however, the PBX market is now truly upended.