The primary investment in networks today is focused on the challenges delivering new bandwidth hungry applications over Last Mile access networks. As operators expand their network footprint to address rural subscribers and roll out new services to already connected households, networks are seeing dramatic increases in bandwidth. Last Mile access solutions including Passive Optical Network (PON), Fiber-to-the-Home (FTTH), and wireless broadband access are the hot technologies delivering connectivity and new services to subscriber households. Less discussed is the impact that the services and applications are having on the next segment of the network a little further upstream: The Middle Mile.

This article examines drivers for service growth, how network architectures are changing to address the new service demands, and discuss the emergence of packet optical networking systems as a means to dramatically altering the economics of The Middle Mile.

Figure 1. Services drive bandwidth growth.

Heavy Bandwidth Growth: Driven By Our Connected Lifestyle
We have entered an era where many elements of our online world are driving exponential bandwidth growth. (See Figure 1.)
• Consumers leveraging Internet-based broadband services for digital entertainment, social networking, and information access.
• Business communications to a distributed workforce, off-site storage of sensitive data,  e-commerce, and 24/7 operations.’
• Mobility and wireless access for personal and business communications to support our always connected lifestyle.
• Service provider competitive differentiation, high bandwidth web-based applications, and savvy users are all factors in driving increases in service bandwidth.

Today’s Middle Mile networking architectures, typically based on SONET Add/Drop Multiplexer (ADM)-based networks, using OC-12 (622 Mbps) or OC-48 (2.5 Gbps) transport have adequately offered connectivity for lower speed, existing service offerings. These network solutions are not well suited to cost effectively address the combination of new access technologies, higher bandwidth services, and rising subscriber growth rates. Network operators must begin migration to a service architecture that can deliver the anticipated capacity requirements at a much reduced cost-per-bit to remain profitable.

Key requirements include:
• The network supporting the shift to Ethernet interfaces and high bandwidth, IP-based service delivery and ensuring a revenue-generating service model.
• Providing capacity that can correlate to service demand and ensure costs are closely tied to available service revenue and subscriber requirements.
• Realizing significant operational value through such tangibles as efficient use of precious rack space and network OAM&P that limits truck rolls and allows dynamic changes to service delivery infrastructure.

A Lighter Alternative
The deployment strategy of choice for The Middle Mile is to move SONET/SDH, wavelength switching and connection-oriented Ethernet functionality onto a single device. This category of infrastructure, called packet optical networking, was basically unheard of in the mid-2000s but will make up $1 billion of telecommunications sales by 2012 according to analysts at Heavy Reading¹. (See Figure 3.)

Figure 3. Packet Optical Network Platform Features.

Packet optical networking platforms bring significant value to The Middle Mile with their modular, "Swiss Army knife" multi-layer approach through their modular fusion of key network technologies.
• Service-oriented Carrier Ethernet providing a comprehensive range of traffic and service management functions for differentiated service levels, end-to-end service management, high availability, and service performance monitoring capabilities
• G.709 Optical Transport Network (OTN) technology for efficient multiplexing, provisioning, and switching of packet-oriented, high bandwidth optical services. OTN also offers integrated 1+1 50ms facility protection, an in-band communications channel, and improved optical link budgets with Forward Error Correction (FEC)
• SONET and TDM-based bandwidth management offering sub-wavelength efficiency, and ADM-on-a-blade functionality; optional SONET wavelength encapsulation also smoothes network migration as it provides the opportunity to interoperate with deployed network systems.
• Optical network building blocks for highly efficient bandwidth growth, dynamic connectivity and reconfiguration, regional network extension, high capacity service interconnect, and streamlined operations.

Why is this a better option? Three simple reasons are outlined below.

1. Converged Service Delivery: The integration of a fully featured Carrier Ethernet switch for demarcation, extension and aggregation functionality for simplified distribution of Ethernet and IP services, plus a full portfolio of muxponders and transponders, provides packet, optical private line, and optical ADM-on-a-blade service delivery functionality from one platform.

2. Cost-Effective Capacity: Traditional SONET network elements require a significant amount of CAPEX to deploy based on their use of common equipment (line optics, cross connects, etc.). The modular architecture of packet optical network platforms means the client service modules contain all functionality -- from client to line -- and relies only on platforms for power, cooling, and management. This means that network elements are provisioned with only the client service modules required -- correlating capacity, and network cost, to service demand.

3. Scalability: Wavelength Division Multiplexing (WDM) "virtual fiber" expands the capacity of physical infrastructure and is the foundation for today's next-generation, service-oriented networks. Coarse WDM (CWDM) wavelength plan addresses low-to-moderate capacity requirements and offers 16 wavelengths with up to 10 Gbps capabilities. Dense WDM (DWDM) solutions offer high-capacity with 40 10 Gbps-capable wavelengths. WDM solutions can be implemented with as little as 1 service wavelength on Day One and scaled to full system capacity as requirements grow.

The Business Behind the Light-er Option
Traditional strategies that leverage separate packet and optical service layers, plus photonic layer functionality independently is not feasible-- especially as service margins continue to diminish. An integrated approach, where all functions are consolidated on one platform, limits network CapEx and realizes significant operational value.

The case comparing an outbound Carrier Ethernet switch plus WDM transport relative to a packet optical platform results in 30 percent CapEx savings; similar -- and in some cases enhanced savings -- are realized when SONET transport subtends the packet switch. (See Figure 4.)

Figure 4. CapEx Savings versus the traditional approach.

In addition to direct monetary savings, a converged Middle Mile strategy demonstrates benefits from an operational perspective:
• Instead of separate packet and transport network elements, service delivery and connectivity functions are consolidated in one platform, simplifying the network, improving technician familiarity, and expediting maintenance.
• A complete photonic toolkit is available for addressing a broad range of network applications: amplifiers, regenerators, dispersion compensation, and coupler/splitters.
• Sparing is significantly reduced with standardized pluggable optics for client and line interfaces; one module can be customized to address any client service demand on any wavelength. Further improvements are realized through the use of new tunable optics.
• A single management platform addresses both the service layer and transport layer, doing away with separate, isolated systems for different equipment, and improving the ability to correlate capacity to service demands.

Shrinking Investments Find the Light-er Solution
Packet optical network platforms bring the right technologies together to provide rapid service provisioning and scalable delivery of services connectivity, eliminating the need for overlaid platforms. They simplify the network environment, which is key to delivering voice, video, and data services over a common infrastructure, reducing the physical number of elements to manage -- and spare.

A packet optical solution for The Middle Mile can address existing service sets and easily evolve portfolio capabilities to offer new services, ensure competitive differentiation, and scale easily as demand grows, with one network investment.

One platform delivers a comprehensive service portfolio including multi-service optical, Ethernet connectivity services, plus acts as the foundation for data and IP services (including IPTV, VoIP, Internet access, and IP VPN services).

Heightened customer retention and service revenue growth is achieved by offering a high availability network with stringent SLAs, and the opportunity to evolve a customer service set from connectivity through to hosted offers expedited service delivery with point-and-click provisioning rather than truck rolls

The inevitable migration from circuit-switched networks to more cost-efficient packet-based ones is occurring; a packet optical-enabled Middle Mile ensures it is optimized to address the road ahead.

The Middle Mile 101
The Middle Mile refers to the broadband infrastructure that aggregates, converges, and backhauls broadband service bandwidth and connects COs, POPs, hubs, or data centers. This infrastructure includes interoffice transport, backhaul, Internet connectivity, special access solutions, and can also refer to mobile base station backhaul infrastructure and connectivity to the Internet backbone. The Middle Mile differs from traditional metropolitan networks in that the emphasis is on fiber optimization. It typically has a hubbed traffic architecture,
and a key requirement is cost-effective scalability.  (See Figure 2.)

Figure 2. The Middle Mile.

Endnote
1. "Packet Optical Market Set to Explode" by Ryan Lawler, Light Reading, September 14, 2007. http://www.lightreading.com/document.asp?doc_id=133860

 About the Author
Jason Smith, Technical Solutions Marketing Manager, BTI Systems Inc., has more than 10 years of experience in telecommunications. He utilizes his expertise in network planning, enterprise network consulting, managed services business development, and product marketing, to convey the value of BTI’s packet optical networking portfolio. Jason oversees BTI’s portfolio value proposition, segment and vertical go-to-market plans, communications programs, and product certifications. For more information, email info@btisystems.com or visit www.btisystems.com.

What is your experience with this? Tell your fellow readers now!