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The freedom that software-defined networking delivers is not magic. It still depends on having the right software in place operating on an appropriate hardware layer. To optimize network operations, the best approach to determining when software-defined networking upgrades to hardware or software are either needed or possible is specific to the organization.
Most organizations are on a five- to seven-year switch replacement cycle, but the specifics with SDN can vary, said Forrester analyst Andre Kindness.
"Historically, if you look at just a firmware and switch, people upgrade the switch 70 to 80% of the time because they need a faster switch, not new features," he said.
In many cases, it is a chicken-and-egg scenario. Sometimes with software, admins must make the effort to figure out if they should install a specific update. There may also be predeployment testing that admins can do to figure out what features to include or activate during installation, said Greg Schulz, senior advisory analyst at StorageIO.
In data centers, the traditional approach was to simultaneously refresh hardware and software, typically when the free maintenance ran out and it was more cost-effective to buy new infrastructure instead of pay for maintenance
Develop an upgrade approach
"One of the major points of SDN was to disaggregate the control plane -- the software -- from the data plane [and] the hardware," said Bob Laliberte, senior analyst at Enterprise Strategy Group.
This makes it easier to apply new software-defined networking upgrades without refreshing the underlying hardware. However, the answer to the question of when and how often to update either is dependent on the organization's risk tolerance, experience with SDN technology and successful upgrade record.
As usual though, the technology has far outpaced the culture and standard operating procedure.
"For applications consumed in the cloud, this isn't really a problem. The vendor can upgrade the software [and] fix a bug as often as they like. However, with enterprise data centers, many organizations are rightfully apprehensive about performing frequent upgrades," Laliberte said.
Potential bugs and glitches are why organizations typically test out new releases in a controlled lab setup first, and then schedule maintenance windows to do the upgrade.
From a practical standpoint, software updates should generally be easier to deploy and, if necessary, roll back in case of any issue. Hardware upgrades require more planning and time to install and test before admins make any transition.
In fact, in many cases, organizations are forced to upgrade the hardware because the latest software version will no longer support legacy hardware, he said.
A complicating factor, according to Schulz, is the "shiny new thing" consideration. Certain organizations and executives like to have the latest and greatest infrastructure, but sometimes it can help to wait if it isn't a critical upgrade. This way, admins can see if the upgrade brings any operating issues into the data center.
It's helpful to evaluate if the SDN upgrade brings new capabilities, addresses a specific pain point or someone in the organization just wants to have the most up-to-date technology.
"Sometimes it can help to sit and wait; if it isn't an emergency, maybe you might want to let someone else be the first to implement because there might be patches or revisions later on," Schulz said.
Admins should be concerned with software and hardware compatibility as well as infrastructure stability. According to Gartner analyst Joe Skorupa, a more conservative approach is the way to achieve a more stable SDN and avoid downtime.
"A production environment is not your lab, and this isn't about passing your next certification or building up your resume," he said.
Despite the promise of SDN, there are many potential glitches involved with upgrading either software or hardware, Schulz said. With hardware-based offerings, the manufacturer validates everything before it is shipped out for delivery.
Use a software foundation for smooth SDN updates
SDN gives admins freedom from hardware vendors as well as many more options as to when and how often to upgrade. But admins should still exercise caution when considering an SDN update.
"On the other hand, now you have more permutations that may not have been tested," which further supports the importance of taking a phased approach when completing an upgrade, Schulz said.
Though admins can unobtrusively install software, making the program function is another task. Even if the hardware is plug-and-play, there are SDN components that introduce complexity, such as network virtualization, coding and overlay applications.
Skorupa emphasized that having a solid software base to manage the hardware underpinning can be very helpful.
"Anytime you have any kind of mixed [infrastructure], it is potentially clumsy and messy. The single console should let you do upgrades in a reasonable way," he said.
Experience also matters. Laliberte cites a customer who was deploying SD-WAN setups to 43 sites. The first few upgrades were completed in maintenance windows in the middle of the night. After the team gained that experience, the team found it could perform the upgrade and switchover in the middle of the business day with only a few seconds of disruption.