h in turn rides over an MPLS-derived pseudowire. It is certain that the architecture of the modern telecom provider will continue to evolve toward technologies that achieve critical mass and as such IP and mobile services will play an ever increasing role. The business model adopted is one of converged networks with customer-driven differentiated products and services. References Allan, D., et al. (2006) Ethernet as Carrier Transport Infrastructure, IEEE Commun. Mag. (2):134-140. American National Standards Institute (1991) ANSI T1.617, Annex D. Atkins, J. W., Cooper, N.J.P., and Gleen, K. E. (2007) The Evolving Art of Packet Switching, BT Technol. J. 25(3/4):222-228. Davie, B., and Rekhter, Y. (2001) MPLS: Technology and Applications, Morgan Kaufmann. De Prycker, M. (1991) Asynchronous Transfer Mode: Solution for Broadband ISDN, Ellis Horwood. Forster, J., Satz, G., and Glick, G. (1994, May) X.25 over TCP (XOT), IETF RFC 1613. IDC (2006) Analyst Report, U.S. Frame Relay Services 2006-2009 Forecast, Publication ID: IDC1266863. IDC (2007) Analyst Report, Western Europe Frame Relay/ATM Services Market Analysis 2007-2011, Publication ID: IDC1573601. References ISO (International Standards Organization) (1984) Standard ISO 7498: Open Systems Interconnection- Basic Reference Model. ITU-T (1993a) Recommendation Q.930/I.450: ISDN User-Network Interface Layer 3-General Aspects. ITU-T (1993b) Recommendation Q.920/I.440: ISDN User-Network Interface Data Link Layer-General Aspects. ITU-T (1993c) Recommendation I.431: Primary Rate User-Network Interface-Layer 1 Specification. ITU-T (1995) Recommendation 1.430: Basic User-Network Interface-Layer 1 Specification. ITU-T (1996) Recommendation X.25: Interface between Data Terminal Equipment (DTE) and Data Circuit- Terminating Equipment (DCE) for Terminals Operating in the Packet Mode and Connected to Public Data Networks by Dedicated Circuit. ITU-T (1997) Recommendation Q.921/I.441: ISDN User-Network Interface-Data Link Layer Specification. ITU-T (1998) Recommendation Q.931:ISDN 