This document describes the specifics of the VAT IAP. For a general description of an IAP, refer iap.html.

The VAT IAP is an Iceberg front-end (or proxy if you will) to the VAT audio conferencing tool.

The specifics of the VAT IAP are as follows:


The files

Running the IAP

The IAP needs to be run as an iSpace service. Add the following line to your iSpace.config file (the one you pass as argument when you run ninja.ispace.Main.

iceberg.iap.vat_iap.Vat_Iap name-server iPOP[:port] Format

The name-server argument exists for historical reasons -- plug in a dummy value. The iPOP is the machine that is running the iPOP, and the port is the iSpace port on which the iPOP is running (defaults to 1099). Format is one of "gsm" or "pcm-ul-8000". Vat is run with "gsm" format or PCM U-Law 8kHz when given those arguments, respectively.

Modifications to VAT

I had to modify vat a wee-bit to make things work. The original vat strictly runs with RTP data on an even port, and RTCP control on the next odd port. This happens even when you give an odd port as a command-line argument. This restriction created problems when the APC chose ports that were odd. Modifying APC to work-around this seemed less appropriate because of two reasons: (a) it required too much change, and (b) it is a hack to get around a specific restriction. Hence I changed vat to allow operation with odd data ports as well. Here's the change I made to the "vat" TCL script (you can find this by typing "which vat"):

In procedure "AddressBlock instproc data-port", replace the "return [expr $p &~ 1]" with "return $p". Do the same in the procedure "AddressBlock/RTP instproc data-port" as well.

Bhaskaran Raman,
Last modified: Sat Jun 3 00:20:44 PDT 2000