Raw versus refined speed

Another facet of open-source routing is performance. In most cases, the use of highly optimized packet forwarding code and custom ASICs will outperform generalized networking software. However, given enough horsepower, that's not the case. You're likely to get better performance from a server-class system running dual-core CPUs than a Cisco router, even though the underlying code on the server might not be as heavily optimized. When planning a network that will terminate hundreds or thousands of VPNs at a central office, this is a very big deal indeed -- especially with a Vyatta router coming in at around one-third of the cost of a Cisco 7200-series router.

Jim Rigas is the president of Zito Media, a company currently evaluating Vyatta routers for use in a new large-scale network. Zito Media is building a carrier network to serve small communities in northern Pennsylvania, and the routers will be located in each town or city to handle all the routing tasks. "We're very interested in the BGP capabilities," Rigas says, "since that's an important part of the network we're building."

The potential cost savings is the big draw, and here Rigas is taking the long view. "We are believers in getting into something that rides the cost curve of standard CPUs, and doesn't lock us into proprietary hardware," he says. "Particularly in an area like this, where we're dealing with a smaller number of customers, the cost/performance ratio is very attractive."

Conjunction functions

When I was discussing the concepts of open-source routers with a few network admins recently, the first thing they jumped on was non-Ethernet routing. It's simple to implement any system as an Ethernet router, because Ethernet NICs are commonplace. But there are only a few places in any infrastructure where Ethernet routing is required. After all, Layer 3 switches perform far better than routers at that task, and one of the main tenets of routing is to move packets between disparate media types, such as between an Ethernet LAN and a T1 circuit.

So where does that leave open-source routing? Well handled, as it turns out. There are several manufacturers that make TDM (Time Division Multiplexing) PCI interface cards. One of the most popular is Sangoma, which offers single, dual, and quad-port T1/E1 interfaces as well as T3 interfaces. With Vyatta's code running on commodity hardware, these interfaces appear to the OS and can be used as ordinary Ethernet interfaces. The single-port T1 interface costs around $700, so it's not bargain basement, but it offers a viable alternative for edge routing needs.

Another conversation point was political viability. It's easy to justify purchasing a Cisco network, but when you start coloring outside the lines, executives can get nervous. It's the same hurdle that open-source software has had to jump for years, though the widespread use of open-source projects has certainly lowered the bar. There may be no better answer to these issues than a side-by-side comparison of features and price. Many misgivings can be erased when the right numbers are presented.

VPN use is a case in point. Open-source routers can serve as extremely cheap VPN concentrators. Although they arguably do not offer the ease of configuration found in some commercial products, they do speak L2TP, IPSEC, and PPTP. Several open-source VPN clients including OpenVPN are available for Windows, Mac, and Linux to support the end-user side. Given the horsepower available on commodity servers, it's possible to build and run a very high-performance VPN concentrator without the high cost. Terminating LAN-to-LAN VPNs on open-source routers is significantly simpler due to the fact that client software isn't needed.