Rollout: Fluke Networks' NetTool Series II Pro

Though clearly designed to excel in an all-Cisco environment, this device provides an easy-to-use method for gathering nearly all the key measurements and parameters from your VoIP installation.

November 16, 2006

6 Min Read
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Fluke Networks' Handheld NetTool Series II Pro testing device is small enough to fit into a computer bag, simple to use and provides nearly all the key VoIP network parameters necessary to troubleshoot problems. Technicians who need quick answers and want to avoid using a $25,000 analyzer will find significant features here, such as gigabit support, port pinging, inline PoE (Power over Ethernet) current measurement, tone detection and a robust protective case.

The $2,995 NetTool supports any VoIP implementation, but works best with a Cisco Systems CallManager installation. By placing the tool inline with the phone, the network technician can see all the essential steps the phone makes when it comes online, registers with CallManager and starts or terminates a call. It takes minutes to gather this information, and just seconds more to create a report and transfer it to a PC. Doing the same thing with a full-featured analyzer, such as Agilent Technologies' Network Advisor or Fluke's OptiView Protocol Expert, typically take much longer and involves using several screens.

Valuable Find

Although Fluke markets the tester as an all-purpose device, NetTool was clearly designed to excel in an all-Cisco environment. This is one of the device's key flaws, and one that other Fluke handheld tools have exhibited. Still, NetTool detected the key devices in our setup and correctly measured packet loss, jitter and the number of transmitted frames in each of our three test environments.The device calculated and reported the jitter as measured in the stream of RTP (Real-Time Transport Protocol) packets that carry the voice. It also reported the jitter calculation made by the called phone. This value appeared in an RTCP (Real-Time Control Protocol) report sent by the called phone to the calling phone. In the past, many test products reported only one of these two values.

By measuring both types of jitter, the device helps the technician locate the switching device or segment that's contributing to the problem. RTCP jitter is calculated by the called phone and reported back to the calling phone. NetTool calculates jitter based on its own internal clock at the point at which the measurement is taken.

When NetTool is close to the calling phone, the calculated jitter is close to zero. As the technician moves away from the calling phone and toward the called phone, calculated jitter increases. Eventually it should match the value reported in the RTCP report generated by the called phone. At any point where the calculated jitter value increases significantly, a device or link is making a substantial contribution to the jitter effect.

3 Environments, 3 Protocols

We tested the NetTool device with systems from three major VoIP vendors--Avaya, Cisco and Vonage. These companies implement the three key call setup protocols, respectively: H.323, SCCP (Signaling Connection Control Point, aka Skinny), and SIP (Session Initiation Protocol).NetTool gives the best detail in a Cisco VoIP network. When we placed it inline with a Cisco 7941 phone, it reported almost everything we could have wanted and gave some surprising information too. It detected the PoE from the switch and passed the power to the phone and ran Autotest (though we had to wait for the phone to reboot). NetTool records everything being communicated by the phone during its boot process. You can execute the VoIP logging function and see the entire process, or you can execute the VoIP Monitor function and watch the call statistics for the RTP stream.

The logging feature records the exchanges between the phone and its CallManager. It also gives all the essential information from the SCCP packets as a call proceeds--even the digits pressed on the phone's keypad. This feature raises a security concern: Those digits could be part of a password if the call is to a voice mailbox or other password- protected resource. Unlike with Fluke's higher-end products, it's impossible to disable this feature on the NetTool.

NetTool Click to enlarge in another window

In our Avaya IP Office environment, NetTool provided some of the key VoIP measurements and detected PoE correctly. However, it couldn't see the H.323 call setup, limiting its ability to troubleshoot the phone registration and admission process. A Fluke spokesperson said the problem was caused by some proprietary extensions to the protocol Avaya added. Furthermore, when we executed the Autotest function, power to the phone was cut and it took more than a minute to complete the test while the phone rebooted.

NetTool did detect the RTP streams and recorded both its own calculated jitter, the RTCP reported jitter, dropped frames and total frame count. Because the device reported jitter in only one direction, we used Fluke's analyzer, Protocol Inspector, to check the trace and found NetTool was correct. The Avaya system was sending RTCP frames in only one direction.When NetTool was connected inline with a Vonage SIP phone, it correctly recorded all the steps in the SIP registration and call proceeding steps. It showed the "invite" with the called number, address and port, the OK, and the setup time. It also recorded the RTP stream statistics including the address, port, TOS (type of service) setting and VLAN tag. It even included the jitter and frame drop count for groups of packets, along with the number of packets used to make the calculation. Agilent's FrameScope provides similar SIP analysis but carries a significantly higher price tag.

Like its predecessors, NetTool provides other helpful network parameters, such as a list of key servers, VLAN IDs, QoS (quality-of-service) levels and ToS bit settings. You can query any switches and routers that are discovered, and get a vast array of SNMP statistics. This feature is available in most tools of this type.

Great Price

NetTool is a bargain for the technician supporting a large Cisco VoIP deployment. Its closest competitor is the Agilent FrameScope Pro. The latter adds several capabilities, including the ability to transmit traffic, both electrical and optical network interfaces, and the ability to simulate SIP calls with prerecorded or live voice. However, the FrameScope costs twice as much as NetTool and is more difficult to use. Most competitors' units are bulkier and more expensive than Fluke's tester.

NetTool ate through four alkaline batteries in about 90 minutes. If you use the recommended rechargeable batteries, it will recharge them from the PoE present in the inline circuit, even when the unit isn't powered up.Phil Hippensteel is an assistant professor of information systems at Penn State University. Write to him at [email protected].

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