August 2000

Optical MANs: Making Waves In E-Business

BY TONY RYBCZYNSKI

Critical to the unfolding of the new e-business strategy is the continued evolution of the back-office network, which in most cases consists of a relatively small number of large sites distributed over a metropolitan area. And what is the next step for the back-office network? One possibility is that it will take advantage of Dense Wave Division Multiplexing (DWDM), a key enabling technology, and a means of cost-effectively multiplexing multiple broadband signals (for example, from mainframes, servers, LANs, and video sources) onto multiple beams of light on a single fiber. This multiplexing results in tens to hundreds of Gbps being reliably networked across a metropolitan network.

NETWORKS OF DEPTH
Service providers have deployed literally millions of miles of fiber optic cables, both in metropolitan and wide area networks. Some large enterprises, notably financial institutions, are already using application-specific, point-to-point dark fiber systems and metropolitan SONET rings. But more common is a mesh of T1 and T3 private lines across the metropolitan area.

New optical wavelength multiplexing technologies present opportunities for much more cost-effective, high-performance multi-Gbps metropolitan solutions with unprecedented levels of reliability. These solutions can be based on the installed base of dedicated fiber or be supplied as a carrier-managed service solution. The availability of both solutions is spurred by increased competition among a growing number of service providers.

KEEPING MANs ABOVE WATER
Optical technologies allow Metropolitan Area Networks (MANs) to satisfy a variety of performance requirements. These requirements, for the most part, fall into three main categories: application support; scalability and flexibility; and reliability. We will discuss each category in turn.

Support For A Broad Range Of Applications
Today, MAN environments accommodate multiple application-specific networks. These include:

• Channel extension and storage networks running within the widely deployed Enterprise System CONnection architecture (ESCON at 200 Mbps) or via the newer FIber CONnection (FICON at 1 Gbps) for "big iron" mainframe environments.
• Inter-router links between campus LANs running long-reach Ethernet, point-to-point protocol (PPP) over links (at 45 Mbps) or asynchronous transfer mode (ATM).
• High-quality video links for employee communications and training.

Such application-specific networks impose specific demands on optical MAN systems. For example, the application-specific networks cited above present a variety of optical signals. The optical MAN system must be able to accept, in native mode, all of these optical signals, and then map them onto a wavelength.

A MAN system with these capabilities needn't use expensive extension and conversion devices, that is, devices that map ESCON onto IP or ATM, or onto slow facilities (these are widely used in today's MANs). A MAN system with these capabilities is both bit-rate and protocol independent. A MAN system with these capabilities has flexibility, allowing for shorter provisioning cycles, reduced engineering times, and reduced lifecycle costs.

A word needs to be said about storage networking, which may present the most pressing high-growth requirement. Storage networking includes ESCON and emerging FICON environments, as well as potentially more open client/server storage area networks or SANs, which are still being standardized. A common characteristic across these applications is that they all use optical transmission at broadband speeds ranging from 45 Mbps to 1.2 Gbps.

Scalability And Agility
To support unplanned traffic demands, scalability and agility are key, particularly with so many applications contributing to ever-increasing traffic demands. In large enterprises, it is fairly common to find dozens of broadband facilities crisscrossing the metropolitan area, supporting channel extension, storage networks, inter-router links, and video.

Applications such as these account for a 30 to 100 percent increase in traffic each year, growth of sufficient magnitude to drive a continuous evolution of network capabilities--specifically, higher capacity interface and backbone speeds. Optical DWDM MAN systems typically support up to 64 unprotected wavelengths (32 fully protected) on a fiber pair, in either a point-to-point or meshed ring configuration supporting ten sites. With a meshed ring configuration, wavelengths can be more effectively utilized and more easily managed. Since a given wavelength can be configured to support payloads ranging from 16 Mbps up to 2.5 Gbps, backbone capacity may approach 160 Gbps on a fiber pair.

Not only are the number of interfaces that need to be supported going up, but so are interface speeds. Channel extension and storage networking speeds operate at a variety of speeds from 200 Mbps to 1.2 Gbps, Ethernet has been standardized to run at 10/100/1000 Mbps and soon 10 Gbps, and ATM runs at link speeds of 45/155/612/2400 Mbps. For example, traffic-driven changes from 100 Mbps Ethernet to 1 Gbps Ethernet, from ATM at 155 Mbps to 622 Mbps, or from ESCON to FICON should be handled in the optical MAN without any hardware changes. State-of-the-art optical MAN systems meet this need by being totally transparent to the bit rate and the protocol of the application. This takes the uncertainty out of network design and creates a competitive advantage by decreasing the time to market for new service delivery.

ULTRA-HIGH RELIABILITY
Given that the optical MAN may be carrying over 100 Gbps of business-critical traffic, ultra-high reliability is the third key requirement. Not only must the optical MAN system architecture meet the stringent electrical, physical, and thermal requirements of service providers and enterprises, but it must also support comprehensive per-wavelength end-to-end monitoring and management capabilities. In the event of a severed cable, the industry standard is a 20-ms protection switch across dual-fiber designs. All this translates into "always-on networking" and 99.999 percent availability, critically required in connecting mainframe/servers, disk storage, tape back up, and print servers.

Today's optical metropolitan solutions substantially simplify the metropolitan networking environment for a broad range of applications, provide unprecedented levels of scalability both in terms of bandwidth and application technology, and deliver carrier-grade reliability.

CATCHING THE LIGHT WAVE
Could you benefit from optical MAN technologies? Most likely -- if you're able to answer yes any of the following questions:

1. Do you have a concentration of large head office, campus, and data center sites spread across the MAN, and are you looking for better networking approaches to meet application and growth needs?
2. Do you have a need to carry high-bandwidth services like ESCON, FICON, high-speed video, Fast or Gigabit Ethernet, ATM, SONET, and FDDI across the MAN?
3. Do you have a dark fiber or SONET-based MAN today, and are you looking for more agility to grow this environment with higher levels of reliability?

You could consolidate your various applications across the MAN, eliminating the need for application-specific networking devices. You could realize the competitive advantage of forecast-tolerant networking through bit rate and protocol transparency and configurable point-to-point and meshed ring topology support. And, of course, you could realize ultra-high reliability for your critical MAN environment. In many cases, with a payback period of less than a year, you will gain control of your destiny to add new services, applications, and protocols without delay.

Tony Rybczynski is director of strategic marketing and technologies for Nortel Networks' Enterprise Solutions unit.  E-mail questions or comments to [email protected]. 

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