What are legacy protocols?

Supported Legacy Protocols

Protocols are sets of rules and standards for data communication.

The most well-known and popular protocol today is the Internet Protocol (IP) and the closely related Transmission Control Protocol (TCP). Most savvy internet users are, at the very least, familiar with the acronym TCP/IP and understand that it relates to how information is sent across a network.

Several other communications protocols dominated the computer networking scene before TCP/IP became popular. These older standards are called legacy protocols. Legacy protocols are simply older data communications standards - such as X.25, SNA, and Bisync - that are still in use. In fact, the term legacy is commonly used in the IT industry to describe older technologies still in use.

As TCP/IP has grown in popularity, legacy protocol expertise has diminished, leaving few professionals qualified to configure and maintain legacy networks, and/or create and maintain programs designed to use these networks.

Nevertheless, legacy networks still constitute the majority of the communications infrastructure in many industries and government agencies.

Why use legacy protocols?


Conversion to an all-IP network often requires hardware replacement as well as rewrites to software applications - some of which may not have available source code. The expertise required to reengineer a legacy application does not come cheap. That's why many Gcom® customers chose to keep their legacy protocol networks but move their legacy applications to newer platforms, allowing them to increase reliability and, in some situations, eliminate costly service contracts on aging hardware.


In some business sectors, notably the banking and financial markets, TCP/IP is the malicious hacker's protocol of choice. There are far more security holes in IP networks than in, say, SNA networks. This is partly because of the physical properties of IP networks, which almost invariably have some connection to the internet, and the obscurity of the legacy code in the applications themselves. Few modern-day hackers know how to deal with anything other than TCP/IP applications.


Once properly configured, legacy networks have an excellent reputation for long-term stability. In fact, many Gcom customers have been happily using equipment and software that is well over ten years old and has never crashed or failed. Gcom solutions can bring hardware up to date while maintaining the rock-solid stability of the legacy protocols that have earned so much respect over the decades.