Wassim

This article describes how I implemented Toll Bypass and PSTN fallback in CUCM and in IOS gateways. Toll Bypass = voice calls follow the WAN and not PSTN. PSTN fallback is the ability to route voice traffic to PSTN when the WAN gets down. I implemented it in my home lab between HQ and Branch1. Toll Fraud Scenarios In these sample Toll fraud scenarios, we will assume that we have the following elements: Destination A Destination B corporate user John. destination A and destination B are international numbers. scenario 1 John calls A and puts it on hold by clicking on the “Transfer” softkey . Then he calls B and puts it on hold too with the “Transfer” softkey. He presses “Transfer” for the third time and now A is transferred to B. They communicate with each other and the call is charged on the company’s bill scenario 2 John calls A and puts it in a conference by clicking on the “Conference” softkey. Then he calls B and puts it in the same conference. Now all three parties can hear each o...

Before plunging into the world of CUCM digit manipulation, let us learn what an E.164 number is. What is E.164? E.164 is an ITU-T recommendation for international PSTN numbering. It is meant to be a way to globalize phone numbers, which means to define and standardize the format of phone numbers around the world. Historically, E.164 evolved from the ITU-T E.163 created in 1997. E.164 format E.164 introduces a powerful symbol: the plus sign “+”. If you take a look at the résumé of an international consultant or a Sales Manager who travels frequently, did you notice something special in the phone number section? The plus sign for example, in front of the phone number? That’s what I’m talking about. The phone number of our Sales Manager is written in the E.164 format. For example, in the US, if you want to dial long distance number 512.555.1234, its E.164 format will be +1.512.555.1234. You won’t dial the dots of course they’re just seperators for e...