By Joel E. Welch, SCTE
2005 IS ARGUABLY THE “The Year of VoIP”. VoIP deployments have begun in earnest and operators are ensuring they have the talent, skill and knowledge to successfully compete with the incumbent telephone providers.
Last week, the Ontario Chapter of the Society of Cable Telecommunications Engineers (SCTE) organized a seminar in Toronto to help operators build upon the knowledge operators may have already acquired.
The goal of SCTE’s Practical Voice over Internet Protocol Seminar was to provide participants with knowledge, tools and examples of troubleshooting techniques to identify and resolve common technical problems that might be encountered with deployment of Voice over Internet Protocol (VoIP) built upon CableLabs PacketCable Specifications.
Our target audience consisted primarily of engineering managers responsible for VoIP deployment. We wanted to provide these folks with enough information about VoIP-related issues to enable them to better define their specific troubleshooting needs. We invited four vendors to help accomplish this, ARRIS, Agilent Technologies, Cedar Point Communications and Sunrise Telecom.
The seminar began by providing a foundation upon which to ensure all participants could stand. I presented topics including an overview of the Public Switched Telephone Network (PSTN). The PSTN has been in existence for a very long time and customers have a high degree of familiarity with it and the service it provides. This familiarity will require the voice service provided by Cable Operators to “look like, sound like, feel like and act like” the service with which they will compete.
In addition, PacketCable specifies that off-net calls (calls to a non-cable voice customer) are handed off to the PSTN in one way or another. This hand off requires an understanding of how the PSTN works and the interfaces required, including the Signaling System 7 (SS7) interface.
The second module of the seminar covered the PacketCable architecture, equipment, signaling and call flow. The embedded Multi-media Terminal Adaptor (eMTA), the Call Management Server (CMS), Media and Signaling Gateways, etc. all shared time within this module especially in discussions about call set up.
Once the foundation was laid, Joe Haver (Agilent Technologies) and John Samulak (Sunrise Telecom) concluded the first day with discussion about potential problems that could impair VoIP service. Haver presented IP impairments and Samulak presented RF impairments.
One key point from Haver’s presentation was that if a VoIP customer is hearing echo, the echo is most likely occurring near the far end of the network. The time it takes the signal to travel and return to the customer is too short for the echo to be perceived. It is through traveling a greater distance, thus inducing a longer time delay between the original voice signal and the delayed echo, that the echo becomes noticeable.
Day two of the seminar was designed to allow the vendors to showcase their expertise in a variety of troubleshooting areas. Al McNichols from ARRIS presented a module describing Management Information Blocks (MIBs). MIBs are “nuggets” of information that can be gathered to assess that state of operation relating to many of the components in the VoIP network.
In some cases MIBs are gathered after a truck has been rolled and the technician has escalated a customer problem to the next support level. One key point in McNichols’ presentation is that MIBs can be used to prevent truck rolls. There is an opportunity to use these “nuggets” to better identify the root cause of service failures and potentially save money by minimizing the need to send a vehicle and technician to the customer’s location.
Returning to their topic areas from the previous day, Joe Haver and John Samulak presented methodologies for isolating the cause of various network problems. Haver again outline IP-related issues and troubleshooting processes, where Samulak covered RF and DOCSIS issues.
The final speakers in the program were Rafael Fonseca and Peter Quigley, both from Cedar Point Communications. Cedar Point had graciously brought an operating Safari switching system working with a live ARRIS C3 Cable Modem Termination System (CMTS) and eMTAs.
Among other points, Fonseca explained that Cedar Point’s deployment experience points to the fact that 50% of VoIP problems are related to configuration and set-up issues, a.k.a. human error. Reducing the mistakes made when individuals enter data or manually intervene in set-up can significantly reduce the number of service problems encountered during VoIP deployments.
Quigley demonstrated how each vendor will likely have applications associated with their VoIP equipment that can be used to track and confirm call progress and events that might be used in during a VoIP call. Using the Cedar Point applications telephone sets connected to the active ARRIS eMTAs and the Cedar Point Switching System, a call was placed while the group watched signaling between the switch and the eMTAs.
Fonseca wrapped up the final module with a very interesting and important note. If a customer experiences a problem with their VoIP service, resist the tendency to begin with the more complex potential causes. More often than not, the problem is associated with something simple, so start there. Look for simple causes first, such as a mistyped MAC address or some similar mistake made during the setup or configuration process. Chances are that’s where the problem lies.
The well-attended SCTE Practical VoIP seminar overall was a success, though it was the maiden delivery of the seminar. It attempted to cover the troubleshooting of PacketCable VoIP service from top to bottom.
To qualify the seminar objectives, we hoped to address as many troubleshooting related issues as we could in two days. In addition this, we hope we provided an environment to cultivate questions specific to the various situations in which our attendees will find themselves.
Joel E. Welch is SCTE’s director, certification and program development. www.scte.org.
To sign on as a member of the Ontario chapter of the SCTE, visit www.scte-ontario.com.
