Apparent Networks' AppareNet Voice Professional

Voice Professional comprises a server, database and sequencers, which are nothing more than remote Java agents that send ICMP (Internet Control Message Protocol) packets across the network. Sequencers are configured and monitored from the server. In our Syracuse University Real-World Labs®, I tested Voice Professional's batch facility to schedule tests that run in the background. Test results were stored in the included Microsoft Desktop Engine SQL database (Microsoft SQL Server is also supported). An included copy of Crystal Reports will report such results, though the database can be queried for ad hoc reporting.

Spotting Jams

Voice Professional uses a proprietary formula to determine network utilization and bandwidth. The sequencers ride the same networked path as regular traffic to identify bottlenecks. It may seem like the only way to get data is through SNMP or direct access, but that's a part of AppareNet's secret sauce. You can find a condensed version of the explanation and links to the marketing-spin-free white papers on AppareNet's Web site.

The additional network load resulting from my tests was less than 1 percent of a 10-Mbps link. That's because Voice Professional doesn't dive deep into packet capture, SNMP collection or session-layer analysis like most network probes and network-management products do. In fact, it doesn't require probes at each network-aggregation segment. Rather, it examines Layer 3 performance to determine where and why voice traffic is having problems.

All this is done without specialized agents on application servers. Synthetic transactions and specialized application or topology knowledge also are unnecessary because Voice Professional mainly uses ICMP and some UDP to test network performance.Because Voice Professional tests at the IP layer, higher-layer protocol overhead that affects end-use throughput is avoided. Layer 2 and lower provide throughput to Layer 3, making network problems visible when measured using IP. (For more on this, see "AppareNet Bags Bottlenecks,".)

Results-Driven

The new VoIP testing results helped me understand the impact network-path performance has on voice calls. Voice Professional includes a per-hop MOS evaluation that I tuned from the intuitive GUI and used to adjust concurrent call volume.

Each of my tests indicated the codex, load and existence of QoS (quality of service). Each segment in the path under test is given a loss, jitter, bandwidth, utilization, propagation delay, RTT (round-trip time) and average/mean/maximum MOS. Additional diagnostics provide summary recommendations, along with the specific analysis and a rough probability that lead to the summary.

These are heady results for a simple ICMP test. Additionally deeper and even more jaw-dropping tests show indications of duplex mismatch and MTU mismatch. Voice Professional does a good job documenting the messages it reports and inferring from the tests possible problem causes and some suggested actions.When a tougher problem, like excessive round-trip times or duplex mismatch, is reported, Voice Professional provides good white papers on what's going on technically and how to interrupt the problem. For example, I looked at a high router CPU utilization report that showed the path to have plenty of bandwidth. Voice Professional explained that the routers direct packets addressed to themselves to a secondary queue and use CPU to respond, but for packets that travel through the router, the routing is handled by ASIC. Thus it's possible for Voice Professional to report a high CPU that may not be problematic. This insight into the path packets that are traveling might not impact overall throughput, but it will characterize a particular path.

One particularly bad path I measured gave me a relatively good MOS score in a best-use case but a poor score in the worst case. I could easily reference which segments in the path were problematic. The accompanying analysis suggested some possible causes. In this case, the problem was out of my control, but the information was useful because I could go to my service provider with specific suggestions about where the problem is and how it might be remedied.Hearing Is Believing

A cool voice-measure feature is the voice-sample playback. Voice Professional uses the test results to simulate link degradation and then plays a recorded message affected by that degradation--a sound is worth a thousand MOS scores. I'd love to have one of these for my cell phone so I could mail my service provider a clip of my call quality along with my reduced payment.

Unfortunately, I found a couple of usability problems. First on the list: The reporting interface, Crystal Reports, functions but not easily. To see a trend report, for example, I had to know the exact name/number of the test, which meant looking at the main server interface, which is a separate interface. You should be able to get this from a scrolling list and/or context launch from the test itself.

Second is the requirement to search the database to see the running and configured batch tests. I had to do a SQL "select" and a Voice Professional form gathered my search results, but because I didn't know exactly what I was looking for, I had to enter '*' to see all the existing reports.

Save these two minor usability problems, AppareNet Voice Professional is easily deployed--a claim no other end-to-end network-management product can make--and, more important, it gets at network-performance problems that often go undiagnosed.Bruce Boardman, executive editor of Network Computing, tests and writes about network and systems management. Write to him at [email protected].