In-Service Software Upgrade

What Does In-Service Software Upgrade Mean?

An in-service software upgrade (ISSU) is a process through which networking devices and firmware can be patched or upgraded without interrupting the underlying device/equipment’s operations. ISSU is a method for updating a networking device without the need to stop its ongoing processes and restart, which degrades overall network services.

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Techopedia Explains In-Service Software Upgrade

ISSU is primarily used to ensure maximum network availability with minimal downtime as a result of device maintenance or upgrade processes. ISSU was initially introduced by Cisco Systems for updating and upgrading their suite of networking devices. For the ISSU to work, the networking/equipment must have a redundant route processor (RP) within its core architecture. This way, when updating, the upgrade process can be mapped onto a parallel RP and the routine operations/services can be performed from another RP. For example, some Cisco routers and switches are integrated with active and standby route processors. When the upgrade/patching process starts, the active RP’s operations are switched to the standby RP until the upgrade process is complete.

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Margaret Rouse

Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…