Standards for IP over WDM begin to evolve
By Eve L. Varma
The accelerating convergence of data-communications and telecommunications networks, in conjunction with the explosion of data services (see Lightwave, May 1999, page 43), is increasingly imposing requirements for a flexible, efficient, reliable, and scalable network infrastructure. Internet protocol (IP) is often cited as the convergence layer in today's data-communication networks; it can be transported over a broad variety of data-link-layer protocols and underlying networking infrastructures.
This diversity of data-link-layer protocols and mappings of IP into different underlying network infrastructures are among the major strengths of IP and are characteristics likely to endure. However, they present a considerable challenge in terms of the design of broadband data-centric transport networks that enable service providers to optimally carry massive amounts of IP traffic.
Thus, there is considerable interest surrounding the notion of developing data-centric optical-networking solutions commonly called IP over WDM (wavelength-division multiplexing), to facilitate cost-effective delivery of the full range of voice and data services over a unified network infrastructure. The two primary alternative approaches toward meeting this objective are optical internetworking and optical-data networking. Data-centric optical networking has entered the deliberations of both national and international standards and industry forums.
Optical internetworking is under consideration within the optical-internetworking forum (OIF). In this context, it represents a data-optimized network infrastructure in which switches and routers have integrated, optical interfaces and are directly connected by fiber or optical-network elements, such as dense wavelength-division multiplexers (DWDM). Here, IP over WDM means IP packets mapped into Synchronous Optical Network/Synchronous Digital Hier archy (SONET/SDH), coupled with SONET/SDH-based point-to-point DWDM systems. The OIF is working toward optical-internetworking agreements, which it expects to publish in the 2000/2001 timeframe. These will be based upon selection and augmentation, as appropriate, of material drawn from applicable national and international standards.
Optical-data networking is under consideration in Committee T1X1 and the International Telecommunication Union's Telecommunication Standardization Sector (ITU-T). It represents carriage of data over a service-transparent infrastructure that provides optical transport networking (OTN) features, including optical-channel (wavelength) routing, fault and performance monitoring, and protection and restoration. Here, IP over WDM means packets directly mapped-via encapsulation-into an optical channel, where any client signal is accommodated, regardless of its protocol format and bit rate. This procedure involves usage of a digital wrapper "around" the optical-channel client to support channel-associated operations, administration, maintenance, and provisioning functionality. The optical channel may then be networked and managed without being constrained to follow point-to-point links coupled with router topology.
Eve L. Varma is manager of an advanced networking architecture and technology group at Lucent Technologies (Holmdel, NJ). She is active in the ITU-T and Committee T1. She can be contacted at tel: (732) 949-8559; fax: (732) 949-3210; email: firstname.lastname@example.org.