Standards for IP over WDM begin to evolve

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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.Th 0003lwe038

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:

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