Internet Data Distribution

An Alternative to Ku-Band Reception

Background

The Unidata Program Center (UPC) has been planning, developing, and testing a system called the Internet Data Distribution. We had a rapid deployment of the system during the summer/fall of 1994 resulting in over half of the Unidata institutions connecting to the IDD.

The deployment of the IDD was accelerated due to the National Weather Service announcing its plans to move to higher data rates for their Family of Services (FOS). In response to the higher data rates requirements, Alden Electronics, Inc. (the vendor that holds the contract with Unidata to broadcast NWS data and the Unidata/Wisconsin data stream to universities at reduced rates) announced that it would require all its sites to switch to Ku-band receivers. (Most Unidata universities had received the satellite broadcast on C-band receivers.) Sites that leased equipment from Alden had their receivers replaced by Alden; sites that purchased the receiving equipment had to replace it at their own expense. (For further information, contact Alden at 1-800-225-9492.)

What is the IDD?

The Internet Data Distribution system is designed to replace the satellite-broadcast distribution system. The IDD uses Unidata's Local Data Manager (LDM) software to move data over the Internet computer network in near-real time. As data arrive, they are distributed to relay sites which, in turn, relay them to end-users or other relays until all recipients have been served. Data available via IDD will include: FOS, NIDs, and the Unidata/Wisconsin data service. Difax service is also available through subscription service via the IDD. Clearly, the IDD is a community endeavor, one that depends upon voluntary commitments to one another by universities. Maintenance of adequate computing and networking resources must be among these commitments.

Why would I want the IDD?

• Family of Services data (with the exception of DIFAX) will be free to you. (Unidata has purchased these data from Alden under terms that allow distribution to Unidata universities.)
• You will have access to a greater range of data.
• You may use IDD instead of purchasing or leasing satellite receivers. (However, the IDD may be less reliable)
• Over the long term, you may experience fewer data-reception errors than with the satellite broadcast system.

What are the risks?

• Reliability. Over the short term, the IDD may not be as reliable as the Ku-band broadcast by satellite.
• Network performance. Receiving and relaying data will require communications bandwidth beyond that consumed by your current network traffic.
• Timelines. Although many data products will be delivered to IDD sites sooner than with the satellite broadcast, network congestion may cause some products to be delayed up to several minutes, especially if they must first pass through multiple relay sites.
• Preparation. To use the IDD software you will need to meet specific operating-system and platform requirements.
• Internet connectivity. You must be connected to the Internet to participate.

What do I contribute?

Consider being a relay relay site. The success of the IDD depends on your relaying data to other Unidata sites. (If you only have OS/2 platforms, you may not act as a relay site at this time, but you can still receive data.)

What does this mean for me?

In terms of costs, if you join the IDD and do not acquire Ku-band equipment, you save the cost of the equipment and you may decrease your expenses for data. However, you may encounter increased costs for network service. In either case, you should not expect this path to be trouble-free; rapid increases in the number of IDD users are bound to create unforeseen difficulties, and some of these may result in data losses. Over the long term, however, we expect reliability of the IDD to match or better the satellite-broadcast system. By 1996, the Internet will be the only mode of data delivery supported by Unidata.

Here is additional information on the principles of the IDD.

This provides information on Site Requirements and what is needed to get started.

Universities wishing to participate in the IDD need to address some technical questions about their computing environment. To obtain the IDD and system information, please send an email message to support@unidata.ucar.edu

Special considerations

Unidata presents LDM workshops every six months that start with a half-day session on the UNIX system administration concepts and terminology necessary for understanding and administering the LDM. Annoucements of the Unidata workshops are provided via email and the Unidata Newsletter.

McIDAS users, please note:

The Unidata/Wisconsin data service (i.e., the McIDAS data stream) will not be broadcast via satellite after December 1995, although Alden will continue its satellite broadcast of FOS and other NWS data. We intend to continue the Ku-band broadcast of this service through December 1995.

ULTRIX users, please note:

The LDM will not run on ULTRIX platforms; the capabilities needed for IDD are present only in DEC's OSF1 operating system.

Please contact support@unidata.ucar.edu for more details.