Review: RouteScience's PathControl

RouteScience's PathControl can help your data get to where it's going faster. This device optimizes outgoing Border Gateway Protocol routes by measuring the latency across site-to-site Internet connections. Our lab tests showed PathControl monitors the delay found in each ISP connection network and then ensures data is sent along the most available routes. PathControl's strong performance in our tests, easy-to-use interface and extensive set of BGP features combined to earn our World Class Award.

In any multihomed Internet environment, the network router will receive multiple routes for the same destination network. The BGP routing algorithm computed by an Internet router determines the best egress route by comparing default attributes in a specific order for each route, from each provider, until a best path can be determined. In a situation in which all the metrics are identical, the best path selected is the route with the lowest BGP router identification number.

Because BGP does not take into account link congestion or the difference in delay among multiple ISP connections, a product such as PathControl increases the likelihood that end users will get the best connection possible. We tested the 14-slot version of PathControl that supports up to 10 peerings and found it will increase the likelihood the Internet router will select the route with the lowest latency.

PathControl ships with three modules. The engine stores live measurements and runs the BGP routing process. The management module serves up a Cisco-like command-line interface that lets a user configure the other modules. The user statistics (USTAT) modules measure the handshake round-trip time (HRTT), which is the time it takes for a host to complete a TCP handshake.

An optional reporting module, which costs $35,000, mirrors the data stored on the engine module and produces comprehensive summary and trending reports via a Java-based front end. With the reporting module, a user can see which Internet links perform the best over time and the percent optimization improvement.

Passive mode lets the user test the product without interfering with outgoing BGP routes. In active mode, the PathControl device makes decisions regarding outgoing BGP routes based on configured parameters.

We tested PathControl using a network that simulated peering with two external BGP providers (see How we did it). We introduced 300 msec of latency and 25% frame loss into the default BGP preferred path. The Cisco 7206 box we used as our Internet router still preferred the degraded connection. But PathControl determined that an alternate route existed via another ISP.

PathControl made this determination by measuring the HRTT between its USTAT modules and the end user across both ISP connections. PathControl advertised the preferred route by adding a higher weight to the route through the other ISP, to the Cisco 7206 router. When the latency and packet loss were removed from the network, PathControl adjusted the preferred route back to the original default egress path on the Cisco 7206 router.

In a multihomed Internet environment, one of the Internet connections often will be more utilized than others. As a content provider's overall utilization increases, more load is placed on the already heavily utilized link, and at some point this would require a bandwidth increase. The monthly price per megabit of Internet connectivity is very expensive, so in a situation like this the user would be adding bandwidth to one ISP connection while the other ISP connections still have unused bandwidth. A device like PathControl, although it is very pricey, could be worth the investment because it allows for even distribution of outgoing traffic over multiple ISP connections.

For PathControl to be used in a production network, a small graphic is placed inside the Web page that an end user is trying to access. This is the mechanism by which PathControl initiates its HRTT measurements. Because this is a very small file, we found no adverse effects to the network or the user by placing it on multiple Web pages.

We don't feel PathControl would be good to use on an ISP link used predominantly to deliver streaming media content. Content providers that use third-party distributed content caches would need to make sure that the file was not placed on any Web page that is to be cached. If a caching engine serves the file, no request is generated to PathControl, so no HRTT could be measured for route optimization by PathControl. RouteScience says it is working on a way to resolve this issue.

PathControl also includes options that can be used to improve BGP routing decisions. We tested the penalty value, the Autonomous System-padding, the asserted-routes-timeout, and the min-required-measurements options. All worked as advertised.

The penalty value is used as a bias to control link selection. The higher the penalty, the less likely a route will be preferred. Autonomous System-padding adds private Autonomous System numbers to the Autonomous System-path to make the asserted route unattractive to other ISPs in case it is accidentally advertised. The asserted-routes-timeout values define how long PathControl will leave an asserted route in the Internet router if no measurable traffic has been received. The min-required-measurements determines how many HRTT measurements should be taken before a route is asserted.

Other untested options include the ability to change the outage control, flap-control and metric change threshold.

Overall our tests showed that PathControl can assist in monitoring, controlling and optimizing Internet connections. It also provides a reliable mechanism for configuring preferred routes based on latency measurements and user configurable parameters. The increase in egress routing performance by PathControl can provide a definite return on investment.

PathControl 4.7 Rating Company: RouteScience, (866) 817-6883, www.routescience.com Cost: Pricing for the eight-slot version of this device starts at $99,900. Pros: Increases egress routing performances; easy to use command-line interface; many BGP options. Cons: Not ideal for routing streaming media content.

PathControl Performance 30% 4   Configuration/Management 30% 5   Features 30% 5   Installation/Documentation 10% 5   TOTAL SCORE 4.7

Individual category scores are based on a scale of 1 to 5. Percentages are the weight given each category in determining the total score. Scoring Key: 5: Exceptional showing in this category. Defines the standard of excellence; 4: Very good showing. Although there may be room for improvement, this product was much better than the average; 3: Average showing in this category. Product was neither especially good nor exceptionally bad; 2: Below average. Lacked some features or lower performance than other products or than expected; 1: Consistently subpar, or lacking features being reviewed.

Goddard and Vaughn are network engineers at the University of Florida. They can be reached at ggoddard@ufl.edu and rwvaughn@ufl.edu.

How we did it
A look at how we tested RouteScience's PathControl.

More information about PathControl
From RouteScience.

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