In the last part of our series on Cisco's drivers and challenges in the service provider market, we focus on the company's venerable routing software, IOS, which may present Cisco with one of its most daunting technical challenges. IOS routing code is often considered a blessing and a curse for the company: It's widely installed, yet it\u2019s 15 years old and its roots are in enterprise networking.In the last part of our series on\u00a0Cisco's\u00a0drivers and challenges in the service provider market, we focus on the company's venerable routing software, IOS, which may present Cisco with one of its most daunting technical challenges. IOS routing code is often considered a blessing and a curse for the company: It's widely installed, yet it\u2019s 15 years old and its roots are in enterprise networking.Analysts and competitors bash it for being monolithic, unstable and a CPU resource hog -\u00a0Juniper\u00a0continually states that IOS saps wire-speed performance from the 12000 series routers when additional software-based services are turned on.\u201cYes, it's a monolithic piece of code that is sensitive to changes and new additions,\u201d says Joe McGarvey, an analyst at Current Analysis. \u201cAt the same time, it runs throughout its product line and is ingrained in thousands of environments. It's sort of like the weather: There's no point in complaining about it, because you can't do anything about it.\u201dCisco is, however, making incremental changes to the current IOS specifically for service provider duty, says Roland Acra, Cisco senior vice president and service provider CTO.\u201cWe\u2019ve done a lot with IOS specifically for the service provider space,\u201d he says, citing recent scalability, reliability and high-availability enhancements such as non-stop forwarding, stateful switchover and Globally Resilient Internet Protocol capabilities. \u201cThe amount of investment in IOS is going predominantly for service provider purposes. Many of our large carrier customers have installed these capabilities and found tremendous uptime improvements. The adoption is high because these are the guys who asked us to do these things.\u201dThere's been years of speculation that Cisco is rewriting IOS or developing a new, unique operating system from the ground up specifically for carriers to meet their requirements for modularity, protected memory operation and availability.This new software is referred to as "IOS NG," where NG stands for "next generation." But Acra says talk of a new operating system is overstated, and that Cisco will not take a "flash cut" approach to optimizing its routing code for the service provider environment.Cisco is doing a lot of "piecemeal" work, Acra has said, to modify IOS platform software, operating system and applications exclusively for the service provider space. IOS images currently shipping to service providers have had little to do with the same code that runs in enterprise routers.The work currently underway on IOS includes "cleaner" interfaces, increased modularity, uptime and protection against failures, and the ability to shadow redundant processors, Acra says. Cisco is also looking to scale IOS to support "super POPs," where heavy-duty aggregation and peering involving thousands of peers and tens of thousands of interfaces takes place.Cisco has also made progress in reducing the number of route flaps and routing loops in IOS, he says.