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What is a Gigabit Interface Converter?

Kurt Inman
Kurt Inman

A Gigabit Interface Converter is a hot-swappable transceiver for networking equipment. It can connect a Gigabit Ethernet, fiber channel or other high-speed cable to a compatible network card. It is often used in computer networks that depend on flexibility in the types of connections they can accommodate.

Also known by the acronym GBIC, a Gigabit Interface Converter can be quickly replaced without powering down the server it is attached to. A GBIC-compatible network card can be connected to any of the supported high-speed media. A GBIC is available for each of several fiber channel cable types as well as Gigabit Ethernet. This gives network designers and maintainers the flexibility to expand and reconfigure their networks at will.

Cat 5 cable with RJ45 plug.
Cat 5 cable with RJ45 plug.

Without a GBIC, changing out a particular type of cable media was a time-consuming and potentially expensive task. The server containing the old media-specific network card often had to be turned off, which could be problematic. The card had to be replaced with a potentially expensive one for the new media type. Once the server was powered up again, software may have needed reconfiguration as well.

This process is often made faster, easier and more cost-effective by using a less-expensive GBIC. The original media-specific Gigabit Interface Converter is unplugged while the server is running. The new GBIC is simply inserted in its place without shutting down or reconfiguring the system.

The Small Form Factor (SFF) Committee, an ad hoc industry group, created a Gigabit Interface Converter specification in the late 1990s. Called SFF-8053, it establishes a common electronic interface and a mechanical form factor for these devices. Originally written for a fiber channel converter design, the spec now includes Gigabit Ethernet-specific information as well. It also details algorithms to be used for GBIC management and error recovery.

A Gigabit Ethernet GBIC generally includes a microcontroller and a 1,000 Base-T transceiver. They can communicate with each other over the Inter-Integrated Circuit (I2C) bus. Signals to and from the network card connector can also travel over this serial bus. On the network side, a transformer couples the transceiver signals to a Registered Jack 45 (RJ45) connector. A fiber channel GBIC is similar, replacing media-specific components as appropriate. The transceiver, transformer and network-side connector would be different, for example.

The form factor of a Gigabit Interface Converter was originally designed for a fiber channel connection. A physically smaller variety known as a Small Form Factor Pluggable (SFP) transceiver also exists. Sometimes called a mini-GBIC, it provides the same flexibility as a standard GBIC in a smaller package. A 10 Gigabit SFP (XFP) transceiver, specially designed for the higher-speed network technology, is slightly larger. The XFP includes digital diagnostics and extensive management capabilities in its design.

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    • Cat 5 cable with RJ45 plug.
      Cat 5 cable with RJ45 plug.