Table of Contents
GridFTP is a high-performance, secure, reliable data transfer protocol optimized for high-bandwidth wide-area networks. The GridFTP protocol is based on FTP, the highly-popular Internet file transfer protocol. We have selected a set of protocol features and extensions defined already in IETF RFCs and added a few additional features to meet requirements from current data grid projects.
Features new in GT 4.0
- A new, complete reimplementation of the server.
- Support for striping.
- This new implementation will greatly ease new feature additions and modifications of the server (new commands, new data sources such as mass storage devices, etc.), maintainability, and resolves a licensing issue that was discovered.
Features that continue to be supported from previous versions
- GSI security: This is the PKI based, de facto standard security system used in Grid applications. Kerberos is also possible but is not supported and can be difficult to use due to divergence in the capabilities of GSI and Kerberos.
- Third-party transfers: Very common in Grid applications, this is where a client mediates a transfer between two servers (both likely at remote sites) rather than between the server and itself (called a client/server transfer).
- Partial file access: Regions of a file may be accessed by specifying an offset into the file and the length of the block desired.
- Reliability/restart: The receiving server periodically (the default is 5 seconds, but this can be changed) sends “restart markers” to the client. This marker is a messages specifying what bytes have been successfully written to the disk. If the transfer fails, the client may restart the transfer and provide these markers (or an aggregated equivalent marker), and the transfer will pick up where it left off. This can include “holes” in the file.
- Large file support: All file sizes, lengths, and offsets are 64 bits in length.
- Data channel reuse: Data channel can be held open and reused if the next transfer has the same source, destination, and credentials. This saves the time of connection establishment, authentication, and delegation. This can be a huge performance difference when moving lots of small files.
- Integrated instrumentation (Performance Markers).
- Logging/audit trail (Extensive Logging in the server).
- Parallel transfers (Multiple TCP streams between a pair of hosts).
- TCP Buffer size control (Protocol supports Manual and Automatic; Only Manual Implemented).
- Server-side computation (Extended Retrieve (ERET) / Extended Store (ESTO) commands).
- Based on Standards: RFC 959, RFC 2228, RFC 2389, IETF Draft MLST-16 , GGF GFD.020.
Other Supported Features
- On the client side we provide a scriptable tool called globus-url-copy. This tool can take advantage of all the GridFTP protocol features and can also do protocol translation between FTP, HTTP, HTTPS, and POSIX file IO on the client machine.
- We also provide a set of development libraries and APIs for developers wishing to add GridFTP functionality to their application.
Deprecated Features
- None
The following areas have received substantial effort in order to make using GridFTP easier, more enjoyable, etc:
- 100% protocol compatibility with previous versions. Any client/server combination since 2.4.0 should work (barring a new client trying to invoke new functionality on an old server).
- Greatly improved documentation. It is not complete, and we will continue to develop it, but it is far better than past versions.
For GT 4.0.0 there is a completely new server implementation that provides the following benefits:
- More stable (one project went from on the order of 1000 failures in a large workflow with the 2.4.3 server to zero failures with the new server).
- More scalable (we had a single server supporting 1800 clients).
- Easier to extend and modify. The Data Storage Interface (DSI) allows a clean way to access things other than POSIX file systems, such as tape systems, custom storage systems, etc.
- Ability to run threaded servers (previous versions of the server did not support this).
- striping is now available (allows multi-Gigabit speeds).
- Easier server configuration.
Protocol changes since GT 3.2
- None
API changes since GT 3.2
- None
Exception changes since GT 3.2
- Not Applicable (GridFTP is not Java-based)
Schema changes since GT 3.2
- Not Applicable (GridFTP is not SOAP-based)
GridFTP depends on the following GT components:
- Pre-WS Authentication / Authorization
- C Common Libraries
- XIO
GridFTP depends on the following 3rd party software:
- OpenSSL (version included in release)
Tested platforms for GridFTP
- i386 Linux
- ia64 Linux (TeraGrid)
- AIX 5.2
- Solaris 9
- PA-RISC HP/UX 11.11
- ia64 HP/UX 11.22
- Tru64 Unix
- Mac OS X
While the above list includes platforms on which we have tested GridFTP, it does not imply support for a specific platform. However, we are interested in hearing reports of success or bug reports on any platform.
Associated standards for GridFTP:
- RFC 959 Base FTP protocol
- RFC 2228 gssapi security extensions for FTP RFC 2389 FEAT, OPTS, etc.
- extensions to FTP (IETF FTP Working group draft) for structured directory listings, SIZE, MDTM commands.
- GFD.020 GridFTP extensions
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