From WWPI.com - Extracted notes on Wavelength Division Multiplexing
Today’s new multimedia applications are putting a tremendous amount of pressure on enterprise networks to increase bandwidth. As communication moves from text-based email messages to bandwidth-intensive streaming audio/video, ever-increasing volumes of data are flowing across organizations’ networks. Ethernet is the communications protocol of choice for this data flow across Local Area Networks (LANs). As the amount of data moving across LANs increased, the initial 10Base-T Ethernet protocol (10Mbps) gave way at the backbone to 100Base-T or Fast Ethernet (100Mbps). Now, 100Base-T is giving up its place at the backbone to Gigabit Ethernet, which has the capacity to move data at rates up to one Gigabit per second.Where Fibre Channel Fits In
As the amount of data on enterprise networks proliferates, data warehousing and storage is becoming an increasingly important element of a company’s information technology strategy. High-speed Storage Area Networks (SANs) allow different kinds of storage devices (such as tape libraries and disk arrays) to be shared by all users via network servers. SANs, coupled with the Fibre Channel protocol used for communication in such networks, promise significant performance (up to 10 Gbps) and administrative benefits over traditional LAN-based storage.
Beyond the LAN
Business geographic expansion, remote storage and disaster recovery needs require the ability to port LAN and storage protocols across a metro network, with a minimum of protocol conversion and network overhead. In many cities, the increasing cost and scarcity of real estate has caused more and more businesses to relocate workgroups and computing resources (e.g., data centers) off-campus. Many companies must travel 30 miles or more from headquarters to find suitable off-campus sites or locate backup sites "across the river" on a separate power or communications grid. High-speed access services need to accommodate a mix of Ethernet, IP, ATM and Fibre Channel— transparently and regardless of distance—from one side of a large metro footprint to the other. These networks demand guaranteed throughput at native wire speeds, highly responsive service restoration, minimal latency of data delivery, and real-time management of the network’s storage resources—without disruption to LAN performance.
Wavelength Division Multiplexing – Native Transportation of LAN/SAN Protocols
The suite of wavelength division multiplexing (WDM) products offered today enables service carriers to offer new classes of service (such as Gigabit Ethernet and Storage Area Networks) in a transparent and native fashion without the inefficiencies and expenses of protocol conversion. A classic example of this type of network is to use a modular optical access platform consisting of a central concentrator for service provider central offices (COs) or Points of Presence (POPs); a multi-port access multiplexer for buildings serving multiple tenants or services; and an edge interface device for individual customer premises. The system functions as an optical modem, providing an "extension cord" which allows connection of business premises to carrier infrastructures at full LAN speed.
The ability to provide LAN-speed access to metro networks eliminates the need for bridging and routing functions in the Customer Premise Equipment (CPE). Carriers can use a hub-and-spoke architecture to bring all customer traffic into the CO or POP, and route it from that point. By aggregating traffic in this fashion, carriers can leverage investments in routing equipment and utilize the latest developments for improved operational economy. Ancillary equipment, such as the new terabit routing switches, can be most efficiently used in these new net work configurations.
Multiple Configurations
WDM networks provide carriers with multiple configuration options such as point-to-point, cascaded multidrop (through the use of an add-drop module), access ring and hub-and-spoke architectures. Most WDM systems also support multiprotocol, remote provisioning. If a carrier wants to upgrade a particular application, for example from SONET OC3 to Gigabit Ethernet, the provisioning can be done remotely via software.The universality of WDM equipment allows carriers to upgrade or capture new services immediately without expensive truck rolls or the investment in new equipment
Benefits of WDM Networks- Investment Protection: By supporting and co-existing with existing SONET equipment and protocols, WDM networks protect a carrier’s current infrastructure investment while creating new revenue-generating opportunities. Furthermore, additional capacity is built in to the each WDM platform. By increasing the number of wavelengths (via channel modules), additional services can be procured simply, quickly and incrementally as customer demand increases.
- Scalability and Flexibility: Most WDM networks offer the ability to scale as the need for bandwidth increases. For example using a single interface card that can support services for a number of standard protocols, including Gigabit Ethernet, Fibre Channel and ATM at OC-3/12/48 rates. WDM platforms can also provide an interface card to integrate wire-speed Ethernet/Fast Ethernet service with multiple T1/E1 channels, enabling service providers to offer bundled voice and data service over an optical infrastructure.
