"Some of our competitors are suggesting that you pull out [your Ethernet network] and start again with a branded solution," said Greg Zweig, a 3Com product manager. "A customer who has a perfectly good, operational system is told by a sales rep 'That's nice, but it doesn't meet our requirements for X, Y, and Z'."
To many, the tactics violate one of the founding principles of IP networking: that third-party equipment should interoperate with equipment from other vendors.
Cisco Systems is one of the worst offenders, according to Zweig, who accused the networker of preventing them from selecting solutions that best meet their needs.
Worse, some observers feel that the move toward branded solutions is being conducted very subtly, meaning that customers are unlikely to realise that they are being forced into committing to a single vendor.
"You hear a lot of references to the ability to take advantage of installed equipment," Zweig explained. "But what if you don't have that equipment? What if you have something older installed? What [other vendors] are really saying is that you have to take out [legacy equipment] and put in [new equipment]."
Cisco has defended itself by saying that its equipment is completely interoperable with third-party equipment. The company sticks by the single-vendor approach, however, arguing that end-to-end solutions offer features such as integrated management that are not available in mixed-equipment environments.
"If you're using a best-of-breed approach, you assume that you can't get everything you're looking for in an end-to-end solution; and if you're [using] an end-to-end solution, perhaps you're willing to give up a feature or two to get an integrated solution that has integrated management," said Craig Cotton, a senior product manager with Cisco's enterprise voice and video business unit.
Other VoIP players, such as Avaya, have sided with Cisco's approach, suggesting that even if the company is guilty of trying to corner the market, this does not conflict with standard business practices.
"Cisco, with much of the installed base, is doubtless arguing - as any of us would do in that situation - that it all works together," said Donald Peterson, Avaya's president and CEO. Peterson allowed that "there's an increasing realisation that VoIP needs to work within other ongoing networks at the enterprise level", but he also said that Cisco's success bodes well for the industry as a whole.
"Four out of five Lans are not ready for VoIP," Peterson said, citing independent research. "What [Cisco] wants to do is build the infrastructure. Voice, more than any other application today, drives upgrades to that infrastructure. It's the right thing to do, because there is value in delivering application access broadly."
In the standards arena, Cisco admits to sometimes breaking away from the norm in order to innovate, because standards have not been established in all areas of VoIP and because standards do not always address customer requirements.
Cisco's use of Skinny Client Control Protocol (SCCP) signalling technology in its IP telephony systems, for example, still provides a more effective means by which IP phones can communicate with call agents than the H.323 standard can, although it is not ratified by any standards body.
Microsoft struck a blow against Cisco when it rejected Cisco's AVVID standard in favour of SIP, citing the technology's ability to integrate with legacy systems. SIP support is included in Microsoft's Windows Messenger, XP and CE products.
Many other vendors, such as Sei Yang Network Communications and Voix, are also jumping aboard the SIP bandwagon, which demonstrated SIP support for their VoIP products at Comdex.