Using Windows Messenger Voice and Video
Updated: May 28, 2002
By Barb Bowman, Windows XP Expert Zone Community Columnist
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Will Windows Messenger voice and video real time communications work behind a residential home gateway that includes Network Address Translation (NAT) support? Until recently, I didn't think it would ever happen. I've been using developmental firmware and I've got really good news: Voice and video now work behind a NAT box in my home office with Windows XP Windows Messenger!
In the traditional world of residential/broadband gateways and NAT boxes, applications such as NetMeeting and many games depend on a fixed port and/or range of ports being available and usually can be accessed only after a manual configuration of ports, triggers, and DMZ zones. Windows Messenger is one of the first applications to take advantage of session initiation protocol (SIP), an emerging Internet Engineering Task Force (IETF) standard. When it comes to media streams for voice and video, SIP has the same problems behind a NAT box since voice and video are transmitted using the UDP protocol, not TCP. The port number of the end point PC will be wrong in the SIP headers due to the NAT. To fix this problem, Microsoft has implemented the Universal Plug and Play (UPnP) protocols in Windows XP, but that will only work if the NAT device also implements the UPnP protocol. (Without this support, voice and video using Windows Messenger will not work reliably behind a NAT device).
UPnP and the Networked Home
UPnP is a set of specifications that enable diverse devices to communicate with each other, announcing their presence and capabilities on a network and in the PC realm, allowing UPnP-enabled operating systems such as Windows XP and UPnP-enabled devices to recognize each other, communicate with each other, negotiate ports, and allow UPnP applications to work transparently with no configuration needed. In the simplest terms, UPnP devices broadcast their capabilities to all points on the network and allow authorized UPnP clients to act as control points. And, in the not-too-distant future, my networked UPnP alarm clock will turn the networked UPnP thermostat up on a wintry morning and turn on my networked coffee pot. Once a week, I'll send a shopping list of staples from my UPnP-networked refrigerator to my 802.11b-networked Pocket PC and when on the road, I'll probably be able to send instructions from my laptop to my UPnP personal video recorder to record a documentary I'd otherwise miss.
In tomorrow's world, UPnP devices will be embedded in many standard appliances such as TVs, microwave ovens, and HVAC systems and will be transparent to the entire range of networking mediums, including traditional cabled Ethernet, wireless 802.11 (a, b, g and whatever's next), HPNA, power line, Bluetooth, and 1384 or FireWire. Today, I've got a UPnP-enabled residential gateway and am seeing, for the first time, a small part of the home and home office of the future. It looks good indeed, and the best news is that you won't need a personal IT consultant to install it or keep it running.
Automatic Discovery and Setup
D–Link has released the UPnP firmware for their DI-804 router (or Internet gateway device in the new UPnP terminology) and it is available on their support site. I'm pleased to report that the firmware I'm using today is both UPnP enabled and SIP aware. To get the upgrade, visit D-Link Support and select firmware as a resource, then select DI-804 as a product, and then select PROM code and click the download button. I've been happily running Windows Messenger using voice and video behind this residential gateway device over my 802.11b wireless network. These devices are the best of all worlds. Older applications that still require manual opening of ports and special configurations can use the traditional and familiar manufacturer's interfaces. With UPnP-enabled applications such as Windows Messenger and UPnP-enabled home gateways, there's absolutely no configuration or intervention needed. It just works.
Installing a UPnP-enabled residential gateway couldn't be easier. Connect the uplink port to a cable or DSL modem and connect Ethernet clients to the internal LAN ports. Windows XP immediately discovers the presence of a UPnP residential gateway and configures it automatically. As with any other network connection, it is displayed in the Network Connections window; right-click the connection to display a menu that allows you to Enable/Disable the connection, view Status, or display the Internet Connection Properties dialog box. The image below shows the Status display.
Clicking the Settings button in the Internet Connection Properties dialog box opens the Advanced Settings dialog box where services currently running are displayed. As shown in the image below, Windows Messenger is active and the TCP and UDP ports currently open are displayed.
The ports were opened automatically using the UPnP protocol. After a period of inactivity, these ports should automatically be closed and should disappear from the services list. Highlighting and clicking Delete will remove them from the list of available ports immediately.
The Add button may, for some residential gateways, allow you to specify ports using the Windows XP graphical user interface.
D-Link's Web configuration interface allows me full control to make the configuration changes to open specific TCP or UDP ports for other types of media transfer or applications such as file transfer capabilities in Windows (as it requires specific ports to be opened).
Firmware for Existing Internet Gateway Devices
I'm really excited about the great experience I've had with the first crop of UPnP-enabled residential home gateways and can't wait for the technology to be available more widely in new devices and in firmware upgrades for existing devices.
D-Link has released UPnP firmware for the DI-714 (version 5.02 or higher) and advises users of other routers to regularly check D-Link Tech Support for updated information related to when and if UPnP support will be available for models other than the DI-804 and the DI-714.
Linksys includes UPnP firmware on their new BEFSR41W wireless-ready residential gateway, and I'm pleased to report great success using Windows Messenger voice and video with this new equipment. Linksys has also released UPnP firmware for their BEFSR41/11/31U and BEFW11S4 routers, which is available for download. Linksys currently has UPnP firmware in beta for their BEFSR81 and router.
 | I'm hoping that all the vendors who have promised UPnP support are able to release their new hardware as well as firmware upgrades to existing devices in the very near future. |  | |
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I'm hoping that all the vendors who have promised UPnP support are able to release their new hardware as well as firmware upgrades to existing devices in the very near future. And I'm also hoping that vendors who have thus far not committed to UPnP enabling their hardware will quickly realize the need to join the UPnP party because this technology that enables NAT traversal and transparently passes SIP is a real must have. The number of residential home networking users with two or more computers behind a residential home gateway is growing exponentially and when the next generation of Direct Play-enabled games arrives, the requirement for UPnP/NAT traversal gateway devices will explode.
Barb Bowman enjoys sharing her own experiences and insights into today's leading edge technologies. She is a product development manager for AT&T Broadband Internet Services, but her views here are strictly personal.
