If there were an "ugly duckling" award for technologies most despised by architects and beloved by users, Multi-protocol Label Switching would be a top contender.If there were an "ugly duckling" award for technologies most despised by architects and beloved by users,\u00a0Multi-protocol Label Switching\u00a0would be a top contender.Derided by IP purists as a wart on the side of IP and blamed several years ago for the incipient demise of the Internet (which hasn't happened yet), MPLS continues to gain momentum. Market growth rates for MPLS are in the double to triple digits. Infonet, for example, estimates that 80% of its new business is MPLS IP VPNs. The Japanese market for MPLS topped $1 billion in 2002, according to NTT.A less formal metric: The recent MPLSCon in New York was jam-packed with most sessions standing-room only. Attendees and exhibitors included a majority of domestic and international service providers and a surprising number of companies. (If you're thinking of attending, the next one will be held next spring in New York; see www.mpls.com for details.)The decibel level of MPLS opposition also finally has begun to ratchet down. Just six months ago, anti-MPLS holdouts such as\u00a0Sprint \u00a0took\u00a0public stands against the technology. But now that most major service providers publicly or privately have committed to deploying MPLS in at least some part of their networks, the religious fervor seems to have faded.As one service provider executive said, "There are no great technologies. There are just technologies that meet business needs." Amen!So what accounts for MPLS' ongoing growth? Several factors:Lowered operational costs to service providers. By simplifying backbone architectures and allowing for the integration of multiple technology types (frame relay, ATM, IP) across a common infrastructure, MPLS networks are easier and less expensive to manage.Increased flexibility. MPLS enables deployment of a range of business solutions, from virtual LAN services to traditional broadband WANs, and can be integrated with other VPN technologies such as IP Security to provide a spectrum of remote-access and site-to-site services.Potential cost savings to users. I've said often that users should not expect massive cost savings when migrating from a traditional frame or ATM WAN to MPLS. That's still true. But for certain applications, MPLS can help users save money. For example, by collapsing an enterprise videoconferencing network onto MPLS users can offer video to branch offices more cost-effectively. MPLS class-of-service also can permit higher oversubscription rates on access circuits - which means buying less bandwidth to deliver the same services.Finally, service providers that have taken the plunge have had surprising successes. AT&T likes the technology so much that it now offers a "click-to-switch" capability for customers of its IP-enabled Frame service to switch over to MPLS (with zero hassle).And NTT's Arcstar service - one of the world's largest MPLS networks, with 65,000 ports and thousands of customers - has an unprecedented customer satisfaction rate of 98.5%, according to the company.