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Intelligent MCs debunk perceptions; today's media converters offer many more capabilities than their predecessors.

Many network professionals have the perception that media converters simply provide stopgap copper-to-fiber conversion, and are a commodity product that will be obsolete within a few years. This perception has shifted as media converters have evolved into intelligent fiber-connectivity tools that feature remote management, built-in switch technology and other advanced features.

Media converters use transceivers to convert electrical signals to light waves, allowing seamless and transparent integration of copper UTP to fiber-optic lines. By converting copper to fiber, IT managers can extend network distances, add security and eliminate electromagnetic interference.

Media converters also provide fiber-to-fiber conversion to enable dual-fiber to single-fiber connectivity and multimode to single-mode connectivity, with bidirectional data flow using wavelength divisional multiplexing. Media converters support multiple network types and data rates, including 10, 100, 10/100, 10/100/1000 Ethernet, OC-3, OC-12, OC-48, T-I, T-3, asynchronous transfer mode, synchronous optical network and serial technologies.

One of the important advancements in media converter technology is the ability to support virtual LANs (VLANs). The two types of VLAN technology supported by media converters are port VLAN and tag VLAN. Port VLAN enables a network administrator to specify, and restrict traffic flow between a media converter's fiber and UTP ports, providing security and intrusion protection. Tag VLAN incorporates the IEEE 802.1Q packet tagging and untagging standard, including double-tagging.

Enterprise networks that segregate tag VLAN data by department or location can use VLAN media converters as intelligent switches that securely isolate and direct each department's VLAN data, as well as the network-management traffic. Media converters with double-tagging VLAN capabilities are used by service providers to add a second tag to a customer's own tagged VLAN data, 'allowing them to offer their enterprise customers secure VLANs.

Another advancement is support of the quality-of-service (QoS) IEEE 802.1p prioritization standard. This gives IT managers the ability to assign priorities to different data types, enabling the delivery of high-priority, real-time applications such as voice or video over Ethernet. For example, by assigning a low prioritization to user data packets, and a high prioritization to video data, the user data would be "parked" for a few milliseconds, while the video data would have priority to pass through a specified media converter port.

Other features supported by media converters include bandwidth control and port access control. Bandwidth control enables the network administrator to selectively throttle different levels of traffic bandwidth to different ports, thereby limiting the bandwidth allocated to individual users. Port access control provides the ability to easily control and deny individual port access, while maintaining hardware port configuration for easy port re-enabling.

Several media converter manufacturers offer managed product lines, which typically require additional management hardware. The management hardware can be built into the chassis or take the form of a management module installed in a chassis. Management capabilities can also be integrated into a media converter module.

Management provides the ability to remotely monitor, configure and receive trap notifications, which is convenient in campus networks, and essential in enterprise networks that can extend hundreds of kilometers. Monitoring capabilities include individual module and port status and statistics.

Configuration allows the setting of port parameters, such as data rates, duplex modes, port access, VLAN, QoS priority and bandwidth levels. Trap notification presents alarms when link-up/link-down, configuration changes or power Failure events (dying gasps) are detected by the management hardware.

Management can be performed via SNMP, Telnet or a serial/modem connection. Proprietary, SNMP-based management software is available from media converter manufacturers or as third-party software, such as HP's OpenView.

SNMP software uses an intuitive, easy-to-use graphical user interface and provides a depth of network data. Telnet and serial interfaces are available as complicated command line interfaces or self-explanatory, menu-driven interfaces. Management can also be in-band or out-of-band. In-band management data flows on the same cable as the customer/user data, whereas out-of-band management data uses its own dedicated cable. The advantage of in-band management is that it works on existing lines, but the disadvantage is that it can utilize user bandwidth.

Using managed media converters, IT managers can remotely configure network parameters and quickly diagnose problems-reducing maintenance costs associated with lengthy troubleshooting procedures, trips to edge equipment locations, lost revenue and lost productivity from down time.

Managed media converters are available in a variety of chassis configurations. When first introduced, media converter chassis had backplanes that simply supplied power to individual "dumb" modules. Today, chassis backplanes deliver power from triple-redundant power supplies, handle the management traffic and provide Ethernet connectivity that allows modules to share and distribute Ethernet data throughout the chassis.

Manufacturers are also integrating switch technology into media converters and offering multiport switch modules, providing the ability to switch data flow between a fiber port and multiple copper ports. By combining media converters and switch modules in a compact chassis, a fiber uplink can be distributed to multiple end-users.

Media converters are a proven method of distributing fiber segments of up to 120 kilometers from a copper switch in a central office core. In this example, copper UTP from a core switch is converted to fiber via a high-density rack of managed media converters and then distributed to smaller chassis (5, 2 or 1-module) of media converters and switch modules. The fiber is then converted back to copper and distributed to end-users. The copper ports can support advanced features such as VLAN, bandwidth control and QoS.

A ring topology provides a redundant path that prevents a single point of failure from bringing down the entire network. In this example, two copper UTPs from a central office spanning-tree switch are converted to two fiber links via a rack of managed media converters. One of the two fiber links is distributed to the first location on the ring, where a two-module chassis with two media converters sharing backplane Ethernet traffic drops off two 10/100 UTPs to local Ethernet equipment along the ring.

Traffic from the network core switch enters one media converter's fiber port, crosses the Ethernet backplane and exits the other media converter's fiber port, beginning a new fiber segment that cascades to the next location. This continues through multiple locations on the ring, until the fiber segment closes the network loop by connecting to the other fiber link on the rack of managed media converters at the network core.

Ironically, the old perception that media converters would become obsolete because conversion technology would be integrated into switches has proved just the opposite--switch technology has been integrated into media converters.

For more information from Omnitron Systems:
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Title Annotation:Infrastructure
Publication:Communications News
Geographic Code:1USA
Date:Oct 1, 2004
Previous Article:In-the-cloud filtering.
Next Article:PoE media converters.

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