VIPR: Requirements and Key Properties

Bridging VoIP Islands

VIPR: Requirements and Key Properties

By TMCnet Special Guest
Mary Barnes, Principal Engineer at Polycom
  |  June 04, 2012

This article originally appeared in the June 2012 issue of INTERNET TELEPHONY

The fundamental requirement of VIPR is to enable inter-domain communications between any number of domains without requiring any prior arrangement between the domains. This means, for example, that employees in company A can have a video call with employees in company B without needing to know any information, other than a PSTN phone number – e.g., no prior exchange of IP addresses. Without a technology such as VIPR, company A would need to exchange information with company B before setting up a video call.  A common approach is to establish a federation between company A and company B.   Another approach is for the users of the endpoints to exchange unique identifiers such as IP addresses before setting up a video call - e.g., in the case of equipment from the same vendors. 

The only pre-requisite for VIPR is that a previous audio call must have been successfully completed via the PSTN, obviously using existing infrastructure.  It’s important to note that while VIPR enables calls that previously could only be completed via the PSTN to be established entirely over the IP network, the confidence that the calling party is really reaching the intended user is entirely based on the integrity and security of the PSTN. VIPR uses information associated with the PSTN call to validate the phone numbers for subsequent VIPR calls.

Given that VIPR requires no prior exchange of information, the VIPR solution must work with any kind of endpoint in any kind of configuration, such as through gateways. VIPR also must ensure that there is no change in behavior for a user to make inter-domain calls. In the case of a VIPR call failure, the solution must ensure that the process for making calls reverts to the functionality used prior to the initiation of VIPR. Again, this ensures that there is no configuration or change in user behavior required for VIPR.    

VIPR must not require any processing by any intermediaries. A VIPR call should be able to be completed directly – i.e., point to point. VIPR must ensure that phone calls cannot be misrouted or numbers hijacked.  While other technologies use a secure centralized model to ensure the numbers are correctly mapped, VIPR must provide security for a distributed model. Due to the nature of VIPR, a given phone number can be associated with multiple distributed directories. In addition, nothing prevents someone from populating a directory with phone numbers that are not under their control.  The distributed directories in and of themselves are completely insecure.  This would seem to introduce a very difficult problem to solve. However, VIPR does not directly store phone numbers or any other identifying information in the distributed directories, but rather VIPR stores the hash of the phone number along with a node ID associated with the domain that has responsibility for the endpoint associated with that phone number.  As described above, information associated with the previous PSTN call is used to validate the phone number when a VIPR call is made. 

An important characteristic of VIPR and a requirement for its widespread adoption is spam avoidance.  Since VIPR requires that a PSTN call first be established prior to a VIPR call, there is a natural financial disincentive to spammers.  Again, VIPR is building on the PSTN foundation that involves relatively high rates for international calls as well as regulations requiring do not call lists, etc. In addition, a natural characteristic of VIPR is that it maximizes cost savings in cases where there are frequent calls to a smaller set of numbers. However, a  Spam model involves much smaller numbers of calls to a very large set of numbers. Thus, spammers don’t really benefit from the use of VIPR. Certainly, this doesn’t necessarily solve the problem of Spam as some Spam clearinghouses may still decide it is worthwhile to incur the costs.  But, it is not anticipated that this will in any way be a common situation. 

In summary, VIPR is able to solve the inter-domain federation problem because it works with existing phone numbers. VIPR works with existing endpoints and thus requires no deployment of new equipment.  The value of VIPR is the ability for users to participate in enhanced audio, video and other unified communications modalities using the power of the Internet, in situations where previously they only had audio communications provided by the PSTN. VIPR is scalable and is available worldwide making use of the existing deployed Internet and PSTN infrastructure. 

Future columns in this series will discuss further detail on the mechanics of a VIPR call, as well as the security features provided by VIPR.

Edited by Brooke Neuman