What is a router?

They still forward packets, but today's routers from Cisco and others are more about applications and services

Is a router still a router even if forwarding packets is just one of its many jobs?

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More and more applications, such as firewalls, VPN concentration, voice gateways and video monitoring, are being piled onto routers. Cisco's Integrated Services Router (ISR), for example, even boasts an optional application server blade for running scores of Linux and open source packages.

"A customer came to us inquiring about all the services on a router but they did not need the routing capabilities," says Inbar Lasser-Raab, senior director of network systems at Cisco. "It's becoming a hosting platform for any service linked or tied into the routing capability."

A short history of the router

About a fifth of Cisco's annual $35 billion to $40 billion in revenue is attributable to sales of enterprise and service provider routers. And the worldwide router market in 2008 was just less than $13 billion, according to Dell'Oro Group.

But those numbers might become harder to track as the definition of a router changes.

"Whether you call a particular platform or chassis a router depends on what the thing is primarily used for," says Jeff Doyle, president of consultancy Jeff Doyle and Associates and a Network World blogger. "Media gateways, firewalls, GGSNs, etc. They might all have router functions in them, but they are generally called by whatever their primary role in the network is."

In many respects routing has become a more general purpose utility on a hardware platform not exclusively optimized for routing. The routing aspect becomes back-of-mind as the capabilities of the device's other applications and services are of more immediate need.

"As the hardware has evolved…it's similar to the hardware that's used for servers," says Eric Wolford, senior vice president, marketing and business development at Riverbed, which makes WAN optimizers. "The software becomes a bigger and more important part of deciding what it is. Routing is the software logic that does the connecting of the dots. Routing can be done on a variety of hardware platforms.”

Vyatta, for example, runs Linux-based routing code on x86 hardware. It also runs several other open source network applications on the standard hardware, including firewall, VPN concentration, virtualization, address management, traffic management and intrusion prevention that scales from the branch office to the service provider edge.

"In the old days, vendors developed a new box around a new function; we're now seeing a move to bring all of these functions together," says Dave Roberts, vice president of strategy and marketing at Vyatta. "It doesn't make sense every place in the network to plop down three different boxes, or four or five and daisy chain them altogether. It makes sense to still have all these functions but as pieces of a larger system that plays in different places in the network -- more of a general purpose device that supports a lot of functionality."

Vyatta customer New Mexico Courts says the more features that are added to a router, the more the software component of routing is distinguished from the hardware. Time was when router hardware – specialized ASICs and packet processors – was intrinsic to the function itself.

"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.

Still, anything that manipulates packets beyond Layer 3 should be called something else – like a gateway, according to Paul Congdon, CTO at HP ProCurve.

"A router is Layer 3, a switch/bridge is Layer 2, and a gateway anything above that," Congdon says. "Gateway is probably the more accurate term these days, when you look at all the levels of forwarding that takes place."

HP ProCurve recently unveiled a server blade for its 8200 and 5400 switches that enables users to begin integrating and consolidating switching and application processing. The ProCurve ONE module runs software applications from Microsoft (security and network access), McAfee (Web security, filtering and intrusion-prevention system), Avaya (unified communications), F5 Networks (application delivery control and load balancing), Riverbed (WAN optimization), and others.

The ProCurve ONE module is intended to open the switch forwarding plane to more network-centric application awareness, Congdon says. HP has no plans to rename its switches gateways, however.

Carrier Qwest is responding to the federal Networx RFP for "service enabling devices" with routers. It's not a term Qwest disagrees with, and the routers they're providing are not much more sophisticated than the DSL modem in Product Management Vice President Eric Bozich's home.

"The DSL modem probably has the same kind of routing intelligence that devices you pay thousands of dollars for have," Bozich says. "So things have progressed significantly in terms of what's the right terminology. I think service enabling devices is more accurate because it's really what these things do."

Bozich says "there's no magic anymore" to routing -- the functionality of being a traffic cop and moving packets from one interface to another and making those kinds of decisions at wire speed. But it's still essential if not sexy anymore – a DSL modem with 100 features on it still has to route.

"On a DSL modem, I can create ACLs, it's got wireless connectivity, got firewall capabilities… the device goes way beyond packets in/packet out," Bozich says. "But if it didn't do the packets in/packets out, it wouldn't be a very useful modem.”

So where is all of this heading? Cisco's Lasser-Raab believes the trend of hosting more and more applications on a router will change the complexion of the device – but not the name.

"We already have the ISR name; but it's an integrated services platform," she says. "A router is still the device that sits between the WAN and the business network, the LAN. I do associate that with routing more than anything."

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