What is a router

“I gave up on what my traditional concept of a router was some time ago,” says Sam Noble, senior network systems administrator for New Mexico Courts. “It’s an obvious location to add additional services. But it does change the focus of the device. What it highlights is how much of a router is software, not as much a hardware platform as we tend to traditionally think of it.”

Some, however, still feel that if that general purpose device routes, it should be called a router despite the number of additional tasks it performs that push routing to the background. As long as it is forwarding packets based on Layer 3 source and destination information – despite whatever else it does – it’s still a router, says Cisco Certified Design Expert Mike Morris, a communications engineering manager at a $3 billion high-tech company and a Network World blogger.

“It’s still a router, but the definition of ‘router’ is changing,” Morris says. “We think of routers at Layer 3 moving packets in and out of interfaces after altering the data slightly. A lot of the extra features added to routers these days do the very same thing, but at different layers: [session border controllers] operate at Layer 5, application acceleration is Layer 4 and Layer 7, firewall can be at many layers. But all still deal with moving data in one interface and moving it out another after altering the data in some fashion.”

Juniper agrees. It recently enhanced its service provider routers to enable network operators to perform application-layer, real-time MPEG video stream quality monitoring to improve performance and scale.

This capability or any other layered on top of the company’s M- or MX-series platforms, does not make them any less of a router though, according to Juniper.

“Maybe the capabilities of a router have evolved and enhanced over time but I still consider the core functions, the heart of a router, to be unchanged,” says Rami Rahim, vice president of product management for Juniper’s Edge and Aggregation business unit. “As long as the introduction of these advanced services like MPEG-level video monitoring don’t compromise our ability to also scale the router in its more traditional Layer 3 routing function, then I think it’s still a router. It’s just a router that’s vastly enhanced with advanced services. Our customers buy routers; whether they add functionality or not doesn’t make it any less of a router.”

The key, Rahim says, is the “architectural integrity” of the platform that the routing and advanced services functionality runs on. To Juniper, this means separating the packet processing of a router cleanly and distinctly into forwarding, control and services planes.

Without this separation, “innovation” on one plane — such as MPEG video monitoring on the services or control plane — could compromise performance of another plane, like forwarding, he says.