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Loopback for Testing

Overview

To complete a local loopback voice call on a single IP Network Interface Series 2 card in a lab environment, the source and destination IP addresses for the call should be set to the IP addresses of the two local VoIP modules installed on the card.

Local Ethernet packet routing restrictions prevent loopback testing using a single VoIP module.

The Route Control (or Outseize Control) message is used to set the source and destination IP addresses and RTP ports for a call. The IP addresses must be different. The RTP ports are not required to be different. If you try to re-use a port number for a channel that is already being used for a call (RTP/RTCP/T.38), you will receive the following status error code:

0x4B: RTP Port in Use

For example, when using Profile 1 up to 512 (Profile 2 up to 256) simultaneous loopback calls can be setup between the two VoIP modules installed on a single IP Network Interface Series 2 card.

Important! In Profile 2 there are a total of 256 channels. However, one channel is used internally for ICMP support leaving 255 channels.

All RTP traffic between these two modules will be routed locally on the IP Network Interface Series 2 card (no data will be routed through the card’s I/O Ethernet ports).

Internet Protocol. Part of the TCP/IP family of protocols used to route messages and tracks the addresses of nodes.
Voice over Internet Protocol. The delivery of voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public-switched telephone network (PSTN).
The protocol used in most local area PC networks. Typically, most Ethernet networks support data transmission speeds up to 10 Mbps, but 100 Mbps is also possible.
Outgoing call setup during real-time call processing on a specific channel.
Real-Time Transport Protocol. Supports transport of real-time data like interactive voice and video over packet-switched networks.
Real-Time Transport Control Protocol.
The point in the Excel platform where a DS0 connects to a network. Also known as a "socket."