Technical Requirements

Participation in a NASA Digital Learning Network™ event is possible through videoconferencing and/or webcast technology. Two-way audio/video videoconferencing systems that are standards based (either H.320 or H.323) are compatible with all systems of the same standards. There are numerous manufacturers with these standards-compatible products including: Tandberg, Polycom, PictureTel, VCON, Sony, VTel, and ClearOne. The systems used by the NASA DLN Hubs provide:

• Bandwidth - H.320 up to 2 Mbps, H.323 up to 3 Mbps.
• Video Standards - H.261. H.263, H.263+. H.263++, H.264.
• Audio Features - Acoustic echo cancellers, audio mixer, automatic gain control, automatic noise reduction.
• Multisite Features - Dial in/dial out capabilities, voice switched or continuous presence, up to four sites via IP & ISDN (any combination).

ISDN , which stands for Integrated Services Digital Network, is a system of digital phone connections that has been available for over a decade. This system allows voice and data to be transmitted simultaneously across the world using end-to-end digital connectivity. It uses the International Telecommunications Union (ITU) H.320 compression algorithm, a standard protocol for digital transmission across telephone lines. ISDN is a proven technology that has been refined over the last decade to the point that it delivers clear video and voice transmission with few limitations. A typical ISDN videoconference uses three ISDN pairs of lines (384 kbps), but from one pair (128 kbps) to six pairs of lines (768 kbps) can be used.

IP is an identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address. IP is the protocol used for sending emails across the Internet. The H.323 data format, a compression algorithm that provides consistent packet transmission of audio, video, and data across networks, is the standard for videoconferencing over IP. IP videoconferencing eliminates per minute long distance calling charges and allows management of most or all communication technology on a single network.

Schools should consider:

• Videoconferencing equipment capable of connectivity over ISDN (H.320) and/or IP networks (H.323). A system that is both IP and ISDN is recommended so that participation in videoconferencing is not limited.
• ISDN (Optimal: T1 Bandwidth) and/or IP Network connectivity.
• ISDN/BRI dial-out capabilities.
• Location of the systems on a subnet outside the firewall. However, if using IP technology and the system will be placed behind a firewall, access should be allowed locally through the firewall. All firewalls must be protocol aware. Your system administrator should assist with this process. (Additional details are given below.)
• Providing the capability to share data between presenter/audience and vice versa.
• Multisite features, which are optional but necessary if you plan to collaborate directly with more than one site.
• Webcast participation, which is possible via RealPlayer and Web connectivity. One computer and a projection device or a computer lab allows for student interaction via chat forum or email.

A firewall is a set of related programs (located at a network gateway server) that protects the resources of a private network. Basically, a firewall, working closely with a router program, filters all network packets to determine whether to forward them toward their destination. A firewall is often installed away from the rest of the network so that no incoming request can access private network resources. There are a number of firewall screening methods. A simple one is to screen requests to make sure they come from acceptable (previously identified) domain names and IP addresses.

The following information is provided by ClearOne Communications , located at 1825 Research Way, Salt Lake City, UT 84119, Tel 1-800-283-5936 ~ 1-801-975-7200. It applies specifically to the V-There units that have been provided to some of the NES schools.

Your Systems Administrator or Network Supervisor should consult with the manufacturer of your specific videoconferening system to obtain port settings to allow access through your firewall.

Firewall port settings must be correctly set for the V-Thereunitstoallow H.323 videoconferencing over IP (does not apply to ISDN or dial-up switched lines). The firewall settings are ports that must be opened in the network security system or "firewall." If these ports are not open, the connection that will be available over the IP network will not allow the videoconference data to pass properly. This could result in: (1) a failure to establish a connection, (2) a very brief connection and then loss of connection, or (3) freezing during the connection. It is important to understand that by opening these ports, you are punching holes in your firewall, which reduces the protection the firewall provides. CAUTION: For this reason, we recommend that your network administrator review these settings and that only qualified IT personnel make these changes. You will be enabling access to ports 1024+. This puts almost all third party TCP based products in vulnerable mode.

Below is a list of TCP/UDP ports that must be enabled for H.323 videoconferencing to work fully. The non-bold items are TCP (Transmission Control Protocol) and the bold item is UDP (User Datagram Protocol).

Port # Purpose

Q. What is the difference between a test call and a connectivity check?

A. We refer to a Test Call Connection as a recommended test connection from your location to our equipment after we have confirmed your event with us. A connectivity check should only be requested if you have not yet registered for an event.

Q. What is the difference between a Webcast and a videoconference?

A. A videoconference provides real-time, two-way, audio/video connectivity via compatible hardware and software on both ends. A Webcast is a video stream over the Internet of a special event or a videoconference event with up to three schools. The schools and teachers involved give permission to the DLN to stream the event, and a link is provided for participants to interact with the NASA presenter through e-mail or message board.

Q. What does it mean to share the connection with another school?

A. To facilitate the large number of DLN requests, you may be asked to share the connection with one or two other schools. When you share the connection, you will be able to interact with NASA and students from other schools.

Q. Does my class have to be available for a test connection?

A. No, your technical contact will handle the test connection with NASA.