I came across this info on the bandwidth requirements for Communicator and OCS 2007 server.

Hardware and software requirements for Communicator 2007 from the OCS 2007 deployment guide: http://www.microsoft.com/downloads/details.aspx?familyid=f1d1a947-6eff-4ac4-8878-f0a77894ac99&displaylang=en

Table 4.   Minimum system requirements for Office Communicator 2007  

System Component 

Minimum Requirement 

Display Resolution 

Required: Super VGA 800x600

Recommended: Super VGA 1024x768 or higher

Note: Microsoft® Windows® Tablet PC portrait mode is supported.

Operating System 

Windows Vista™ 32-bit (RTM) operating system

Microsoft® Windows® XP Professional with Service Pack 2

Windows 2000 Professional with Service Pack 4 (requires Microsoft® Windows Media® technologies player, version 9, and Microsoft® Windows® Installer, version 3.0 or later)

Computer/Processor 

Data and Voice: 500-megahertz (MHz) or higher processor, Intel Pentium-compatible

For video: 1 GHz or higher

For Microsoft® Office RoundTable™ communications and archival system: 1.8 GHz or higher

Memory 

512 megabytes (MB) of RAM

Install Space 

1.5 MB

Video Memory 

Video card with 64 MB of RAM (video RAM or VRAM) and Microsoft® DirectX® application programming interface

Telephony

Microphone and speakers, headset with microphone, or equivalent device

Video

Video camera or Office RoundTable device

Bandwidth Requirements 

 

Minimum1

High-Quality1

Data

56 kbps

56 kbps

Voice

50 kbps

80 kbps

Video

50 kbps

350 kbps

Office RoundTable

50 kbps

350 kbps

Security

Administrator privileges, or, in Windows Vista® Standard User Mode, administrator credentials.

Other Requirements

Microsoft® Office Outlook® 2007 and Microsoft® Exchange Server 2007 are required for Outlook integration options. See the section titled, "Outlook 2007 Integration," later in this document.

1 The required and recommended bandwidth speeds are cumulative. For example, if you want to use voice, webcam, and RoundTable, the minimum bandwidth would be 50+50+50=150 kbps.