VPIMv2  Whitepaper
Networking for Voicemail

Connecting groups of employees when there is not enough bandwidth for real-time VOIP

Introduction

I've posted this to explain a bit about how VPIM works.  It is a subject of Study in the Cisco IIUC2 Authorized course.

Voice Profile Internet Mail version 2 (VPIMv2)  is defined in RFC 3801 and is a messaging protocol based on SMTP that  extends the familiar johndoe@domain name type of user addresses to voicemail and fax systems.  VPIM connects voice-messaging systems into special-purpose voice messaging networks.   VPIM is not meant to send to commercial email clients but rather to send voicemail from message store to message store.

In many corporate WAN environments, latency or bandwidth issues prevent VOIP connections but there is still a desire for non-realtime voice communication.   VPIM can also be used to interconnect different messaging platforms from the same and different vendors.

Assumptions

This paper presumes that your enterprise has multiple locations and multiple voicemail servers and or platforms.  In this white paper, the different options that are available to help interconnect disparate Cisco and third party voicemail servers will be examined.  This paper is based on Cisco Unity, Cisco Unity Connection and Cisco Unity Express as well as the Cisco Unified Messaging Gateway.

Limitations of non-networked voicemail systems

1. Companies with several locations may need to deploy multiple voicemail stores do to latency and bandwidth issues.
2. Voicemail distribution lists and users are local to their voicemail store and distribution of messages to remote users is difficult.

How VPIM Functions in a Cisco Environment

1. Allows a voicemail created on one system to be sent to another RFC 3801 compliant system.
2. Uses SMTP to transport messages over a TCPIP network.
3. Delayed messages generate a notification after one hour.
4. A nondelivery delivery message is generated if the voicemail message is undeliverable after six hours.
5. Spoken name, vCard and Voicemail are sent as MIME types.
6. QOS enabled bandwidth is not needed as the voice messages are not real-time.  They are treated as SMTP traffic.

A Case for VPIM

Acme Widget Corporation has a global sales group with offices in Tokyo, New York and London.  The Tokyo Office has 100 sales people and has deployed Cisco Unity Connection version 7.1 as a messaging server.  New York has 1000 sales people and has chosen Cisco Unity version 7.0 for voice messaging and the London office has 25 sales people with Cisco Unity Express as the messaging platform.  Each office is interconnected via a Wide Area Network and average latency is 350 ms between any two offices.

ACME Widgets, having a global sales force in different time zones would like to have sales managers able to address a single voicemail message and have it delivered to all sales people in all offices. 

The Design goal is to create a Voicemail Distribution list on each server that send a voicemail to all sales people in all offices.

General VPIM Concepts

1. Each site is assigned a numeric locationID.
2. When addressing a voicemail message the caller uses the combination of the location ID and subscriber extension.
3. The message contains
   1.  forwarded fax and text messages.

1.  Spoken name (If recorded)
2. vCard (phone number, text name and email address)

Configuring Locations

To start you create a VPIM delivery location on each messaging server to correspond to each remote messaging server. Usually, the Domain Name that you enter on the delivery location when configuring one server matches the Domain Name configured for the network local location on destination server. For ease of administration, you should consider matching  the Dial ID and Display Name for each delivery location in the same way.  You will also need to configure a local or Primary location on each server.

Addressing Remote Subscribers

Senders can blind address subscribers on remote systems by using a combination of location ID and the subscriber’s number. Additionally after blind addressing is used once, Cisco messaging servers can cache the text name, spoken name and phone number of the user.  This allows dial by name functionality for subsequent remote messages after the remote user has been sent a single message. An Administrator can also statically define a remote user and record a spoken name.

Codec Considerations

For low bandwidth connections G.729 is the preferred codec to use  and is supported by Cisco Unity and Cisco Unity Connection.  Unity Express only supports the G.711 format, so G.711 must be used when connecting to Unity Express.