CDDIS https Archive Access/File Download FAQ
  1. What is the new CDDIS file download procedure?
    The CDDIS is adding an https-based method to retrieve files from its archive; for now, users can continue to use anonymous ftp to access the CDDIS archive and retrieve files. The new system also uses a NASA single sign-on system for user authentication.
  2. Why is CDDIS making this change?
    The major reason for changing these procedures at CDDIS is security; ftp with its clear text username and password is just not acceptable in this day and age. In fact, some organizations have deprecated ftp or outright banned its usage. ftp protocol also has the disadvantage of being a two-port protocol along with both an active and passive operation mode. This means that EVERY firewall/switch in the network path between CDDIS and the data provider must be configured correctly to function reliably. Unfortunately we have found this too often to not be the case and in most instances outside the control of CDDIS or the data provider to fix.
  3. What are the advantages of https over anonymous ftp?
    The https protocol is as efficient as ftp transfer without the firewall/router issues of ftp. Since ftp is a two-port protocol, users can have connectivity problems (e.g., with firewall, DNS, etc.); https is a one-port protocol with fewer issues with downloads. The Earthdata Login system will be used for access through https. Earthdata Login allows users to easily search and access the full breadth of all 12 EOSDIS DAAC archives. Earthdata Login will also allow CDDIS to know our users better which will then allow us to improve CDDIS capabilities.
  4. Why not use sftp or some other ftp variant?
    CDDIS looked into using some other variants to ftp for file upload but there were disadvantages (some major) to all of these approaches. The http(s) protocol offered more advantages and had performance equal to ftp.
  5. What is Earthdata Login?
    Earthdata login (https://urs.earthdata.nasa.gov/) is the single mechanism for user registration and profile management for all Earth Observing System Data and Information System (EOSDIS) components. CDDIS, as one of the 12 EOSDIS Distributed Active Archive Centers (DAACs), is moving to be more integrated with its larger parent organization.
  6. When will this new file download system become operational?
    Current plans are for the new file download procedure to be fully operational in Spring 2018.
  7. Will my old scripts stop working?
    Not in the near term. The https-based system will initially exist in parallel with the legacy ftp system.
  8. Do I need to only use cURL?
    No, you can use any tool that allows you to submit an https request and that follows an http redirect (302 request). CDDIS recommends that you use cURL as it’s what we support but you are free to use other tools or write your own.
  9. What browsers are supported for the web-based interface?
    The latest versions of Firefox, Chrome, Internet Explorer (IE), and Safari are officially supported. The process may work in other browsers, but is not guaranteed.
  10. What is the index.html file found in the archive directories?
    An index.html file is required in order for web browsers to be able to display the contents of a directory in a proper format. This file is used when accessing the CDDIS archive through https, not ftp. There is no harm in downloading this file; however, if you prefer to not retrieve the index.html file, you will need to modify your scripts to exclude any file named 'index.html' when downloading all files from a particular directory.
  11. Who do I contact for questions?
    Any questions related to the new upload system should be directed to cddis-help@lists.nasa.gov.

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