Q. What is “Topology Hiding”?

A. Topology hiding is a feature that allows service providers to forward traffic to other carriers without revealing the origination device of the media stream. Termination partners see only the traffic from IP addresses, not that of VoIP origination partners. Session Controllers are required to ensure adequate topology hiding and protection of commercial confidentiality while routing media streams.

Q. What is “High Availability?”

A. High availability is achieved by having a backup system running in parallel with the active (primary) system. If the active system fails for any reason –power outage, severed cables, code upgrades, etc.— the backup system automatically assumes handling of calls ensuring high overall system availability.

Q. What is Load Balancing?

A. Similar to high availability, load balancing employs a redundant system, but one that is active at the same time as the primary system. The two systems do not share an IP address but instead both use separate IP addresses, thus ensuring that the backup system is ready to go at all times, but requiring partners to know about both systems.

Q. What is the difference between the SPX and the VSX?

A. The SPX VoIP Session Controller is oriented toward the subscriber access market where dynamic learning of subscriber IP addresses and firewall/NAT management issues typically arise. The SPX forwards calls to other switching devices without looking at the DNIS of the call.

The VSX addresses the needs of tandem switching environments providing call routing based on DNIS or ANI. The VSX requires devices’ IP addresses to be programmed in advance and will not listen to unauthorized IP addresses.

Q. How do you get CDR files from the VSX?

A. All calls are logged into the VSX’s CDR files. These files are SCP’d into the billing server with a simple importation procedure used to align the information with the server’s internal database.

Q. How does the “codec control” feature work?

A. This feature allows service providers to control the codec options offered on individual calls. The inbound codec request is outside the SBC’s control, but the VSX lets codec lists be set for each resource configured into the system. If a call is being routed to a specific resource, the codecs offered to that endpoint will be only those ones programmed into the VSX.

Q. What are CA, ASR, FCR, and ACD?

A. These acronyms are used in the statistics page in the VSX. They relate to the call completion performance for each partner, resource, or route. “CA” stands for Call Attempts, “ASR” denotes “Answer/Seize Ratio,” “FCR” means “Failed Call Ratio,” and “ACD” refers to Average Call Duration in seconds. These statistics are extremely useful in monitoring the service levels of each VoIP partner.

Q. Can configuration be copied from one system to another?

A. Yes. Both the VSX and SPX provide for offline storage of configuration using the System > Advanced > Save Config button. Once stored on a local system, configurations can be uploaded to another system. It is recommended that configurations be saved prior to any major changes being implemented.

Q. Why do I have a demo license and how can I get rid of it?

A. The demo license is kept on the system until it is paid off in full. If your system has a demo license then it is not fully paid for yet.

Q. How do the SPX and VSX fit into the IMS architecture?

A. Both the SPX and VSX will play key roles in an IMS-compliant network. The SPX will transition to be a P-CSCF and SPDF and support the IMS extensions. The VSX will become an integrated BGCF, IWF and IBCF. The two systems will provide excellent access to IMS compatible devices and applications.

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