THE BUSINESS CASE FOR EMBEDDED DWDM OVER ACTIVE DWDM SYSTEMS

This article focuses on comparing embedded DWDM and active DWDM systems. Several methods are available for data center interconnectivity and for connecting traffic between sites in a distributed data center.

Companies can run the network by themselves in a private network or have an operator run it for them through a managed service. Building a private network requires access to fiber, either owned or leased, between the sites. Various technology choices are possible depending on the total amount of traffic required throughout the lifetime of the network and the distance between sites.

Active DWDM systems

An active DWDM system, commonly referred to as a transponder-based system, offers a way to transport large amounts of data between sites in a data center interconnect setting. The transponder takes the outputs of the SAN or IP switch format — usually in a short wave 850nm or long wave 1310nm format — and converts them through an optical-electrical-optical (OEO) DWDM conversion.

There is a clear demarcation point between the optical DWDM layer and the data layer (Ethernet or Fibre Channel protocols). This is important for two reasons. First, a DWDM signal can travel farther than a short-range signal, making it possible to connect geographically separated data centers. Second, many DWDM signals can be connected through a multiplexer and simultaneously transmitted over a dark fiber. But even though these systems can transport huge amounts of data, they are more suited to telecom operators and tend to be overly complicated for data center interconnect purposes for corporations.

Embedded DWDM

Embedded DWDM is able to transport the same number of traffic channels over a dark fiber as a standalone DWDM system, but in a much simpler way with fewer components. Instead of having the OEO conversion from short range to DWDM, the transponder is eliminated because the DWDM transceiver is connected directly in to the SAN or IP switch. From here an LC patch cable connects it to a passive multiplexer (a 1U fiber termination unit), which gathers the traffic signals together and transports them simultaneously over a single dark fiber link.

Active WDM

Embedded DWDM

dci-1-1
  • Telecom system not aimed at the enterprise
  • FC switch needs to be in R_Ready mode
  • R_Ready removes the FC proprietary functions
  • FEC in the FC switch needs to be disabled
  • 2 configurations required – switch and DWDM system
  • Complicated and inflexible networking
  • Layer 1 interoperability tested and approved by Brocade
  • ELWL type approach but with DWDM transceiver. No special configuration required in the switch
  • Easily upgradeable - just add SFP for extra channels
  • Total control of network and bid process
  • Lower TCO and no hidden opex, more budget for other areas
  • No power, small footprint, green data center networking
art1-chart-1
  • Equipment cost (capex) over 3 years

  • Years capex and opex over 3 years

  • 8-channel 16Gbps embedded WDM system

    Investment (first 3 years)
    1 x Embedded DWDM system $53,000
    Capital expenditure (capex): $53,000

     

    Continual operational costs (for 3 years)
    Fiber leasing costs $36,000
    Operational expenditure (opex): $36,000

    Total cost (3 years): $86,000

  • 8-channel 16Gbps active DWDM system

    Investment (first 3 years)
    1 x active DWDM system $70,000
    Capital expenditure (capex): $70,000

     

    Continual operational costs (for 3 years)
    Fiber leasing costs: $36,000
    SLA & SW licensing  $36,000
    Operational expenditure (opex): $72,000

    Total cost (3 years): $142,000

Assumptions

The active DWDM platform is based on a fiber rental cost of $1000/month and $70K for an 8-channel system.

The embedded DWDM platform is based on a fiber rental cost of $1000/month and $50K for an 8-channel system.

The clear benefits of dark fiber and embedded DWDM

Without a doubt, using a traditional DWDM system enables you to transport large amounts of data between customer sites. But these systems are inherently complicated and can be overly expensive. In most cases, the platforms are built for telecom-grade networks and have features simply not required for data center interconnect for enterprises. They are often cumbersome to maneuver and complicated to design, install and configure. Enterprises aim to carry as much data over their fiber network as needed with no impact on quality of service. Their requirements simply differ from those of a telecom operator, who delivers individual circuits to multiple users.

Embedded DWDM offers the same capacity as an active transponder-based DWDM platform, but in a much simpler way. With a passive multiplexer at the heart of the system, you eliminate unwanted heat or noise emissions, keep space to a minimum, and gain the ultimate green data center DWDM network. New services are quickly and conveniently added just by adding the required number of optical transceivers. Embedded DWDM — it really is that simple.

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