Routing for small networks: Hardware or software?

Microsoft Corp. would have you believe the software-based router it offers at no charge with Windows NT Server will enable your existing servers to take on basic workgroup routing tasks. We decided to pit the company's Routing and Remote Access Service (RRAS) against a low-end Cisco Systems, Inc. 2514 router to see just how much substance is behind Microsoft's claim. The answer? A fair amount, although, in reality, RRAS is far from free.

We found that RRAS works as stated for workgroups with a couple dozen users per segment, if you shell out for a high-powered server and adapters. But for larger installations, a dedicated hardware-based router is a better choice.

We chose the 2514 because it's priced at the low end of Cisco's line and thus was the best choice to compare with a router that's included at no extra charge with Windows NT. But the two products are not completely comparable.

Specifically, RRAS has extra features to support dial-in connections via modems or ISDN adapters installed in the server. Low-end Cisco routers have no such capabilities. To gain these features, you would have to go to the midrange series, such as the 4000 models. On the other hand, the Cisco 2514 offers faster processing speed as well as two synchronous serial ports for connections to wide-area links. However, its network interface runs at only 10M bit/sec, while an NT Server can support 100M bit/sec network interface cards (NIC).

Because of the varied capabilities of the products, we focused solely on their ability to route between two segments or subnets to see which needs each satisfies best.

Performance

Performance is the key criterion by which a router is measured. We began testing with 10M bit/sec NICs in the server running RRAS. With a full complement of 20 users printing and running SQL Server queries as well as a backup running across the network, the server running RRAS showed a steady CPU load of 23%.

Users saw a significant degradation in network performance, with collisions in excess of 17%. Increasing the traffic forced the CPU to work even harder, and the server was unable to keep up with the load.

Since Fast Ethernet NICs are now commonplace, we next replaced our 10M bit/sec NICs with 100M bit/sec models. CPU utilization dropped to 6%, and collisions were virtually eliminated.

Running the same tests using the Cisco 2514 to route between our two subnets, the proces-sor of the 2514 ran at only 6% of capacity, according to the CiscoWorks administration software used to administer Cisco devices. Un-like the RRAS server, when the 2514 was running at 10M bit/sec, its internal processor handled every IP and IPX packet without dropping a single one.

To further press the 2514, we loaded both segments with more traffic but still were able to produce a collision rate of only 5% and CPU utilization no higher than 12%. User response time across the 2514 was drastically better than the equivalent test with RRAS. SQL query response time improved, and Internet queries no longer timed out.

Although the 2514 only works with 10M bit/ sec Ethernet (and X.25 and serial synchronous traffic), it takes a powerful server and high-speed adapters for RRAS to keep up.

Even with the right hardware, we concluded that it's unwise to run RRAS on a production server that's supporting other applications. Thus, while the software is free, our test server configuration cost approximately $5,000, compared with $2,600 for the 2514.

Given that configuration, our testing showed that the dedicated hardware device performed better in a demanding network environment. The hardware router also had less overhead than RRAS when complex filtering was brought into play.

Some of the increase in CPU utilization with RRAS was attributed to the filters we established to protect our corporate data, while equivalent filters in the 2514 produced negligible performance degradation.

Management software

RRAS' administration program, Routing and RAS Admin, provides a graphical view of subnets, including manually created routes and the interfaces for those routes that are created by the Routing Information Protocol and Open Shortest Path First routing protocols (see Figure 1, page 43). Clicking on the IP Routing section brings you to the part where each interface is configured for static routes.

You can manage the 2514 via telnet with a command-line interface or across the LAN using the much easier CiscoWorks graphical user interface. CiscoWorks has two main parts, Configuration Builder and CiscoView. Configuration Builder provides a relatively easy way to manage router configuration, as long as you remember that any updates have to be sent to the router's memory. You can keep multiple copies of the configuration ready to be reloaded in case something goes wrong or the router is replaced. RRAS has a similar function.

CiscoView watches the router's ports for bad packets, collisions, giant frames and carrier-sense errors. Statistics gathered include the number of packets, large and small, as well as misaligned packets that the 2514 handles. RRAS lacks the ability to gather many of these statistics but does have decent reporting capabilities.

Installation and documentation

For each subnet routed by RRAS, you must install one Ethernet adapter in a Windows NT 4.0 server. You have to bring down the server to make hardware changes. By contrast, a router does not require you to power it off when changing segments.

After installing the network adapters, we downloaded RRAS from Microsoft's Web site and installed it in less than 15 minutes. This is a marked contrast to the router installation - it took us one hour to set it up with all of the protocols and filters for our two segments.

Initially, we had to connect to the router using a laptop connected to the router's console port via a supplied null modem cable. An automated log-in and configuration script then took care of 90% of the tasks we had to complete. This initial configuration was easy, but ongoing management via CiscoWorks wasn't as smooth as managing RRAS with Microsoft's Routing and RAS Admin tool. One helpful feature of CiscoWorks is its ability to "learn'' what settings you have installed and then set the nonvolatile memory of the router based on what it found. However, the setup of routing protocols, filters and related options takes much longer than it does with RRAS.

RRAS documentation came with the software in electronic form. It made getting started a breeze. The Cisco documentation comes on CD-ROM, and you can either browse it or install it on your PC. It was fairly complete and technically competent.

Summary

All in all, RRAS is an excellent tool for routing on small networks. We believe that RRAS, running on a Pentium 200-MHz server with PCI 10/100 adapters, could handle about 25 users per segment or up to 100 users overall before seeing significant problems.

Low-end hardware-based routers such as the 2514 are more appropriate when 50 to 75 users per segment have the same demanding needs.

For networks with heavy workloads, such as CAD/CAM or database environments, hardware-based routing is a better way to go.

The hardware router initially is cheaper overall than a high-powered server but is more complex to administer than RRAS.