XTP Overview - A general overview of the XTP protocol.

 

Multicast File Transfer with XTP - SMPTE FTP+ Description of point to multipoint file transfer functionality within XTP and how it is being used as part of the SMPTE FTP+ multimedia file transfer specification.

 

Performance of Mentat XTP Over the Internet - Results of tests comparing the throughput of XTP to that of TCP using actual applications over the Internet

 

XTP 4.0 Specification - Official specification of the Xpress Transfer Protocol 4.0. Published by the XTP Forum.

 

XTP 4.0b Specification Draft - working draft of the 4.0b specification of XTP merging in changes to the multicast algorithm. [Postscript Format (1.2 MB)] [Adobe Acrobat Format (416 KB)]

 

SMPTE XTP Draft - working draft of the SMPTE XTP specification in SMPTE/ANSI/ISO format. [Postscript Format (1.3 MB)] [Adobe Acrobat Format (320 KB)]

 

Description of XTP Reliable Multicast Algorithms - Paper published in the 21st Conference on Local Computer Networks. Written by J. William Atwood, Octavian Catrina, John Fenton, and W. Timothy Strayer.

 

Click here to transfer to the XTP Forum Home Page.

XTP Specification

The Xpress Transport Protocol is an open standard developed by the XTP Forum, a non-profit organization composed of researchers, implementors, and users founded to oversee and develop the XTP specification.

As shown in the diagram below, XTP can run either over IP or directly over the link layer. XTP can also operate as both Transport and Network Layers (ISO Layers 3 and 4) for maximum efficiency or to take advantage of special link layer functionality in situations where internet routing is not required.

The efficient design of XTP includes flexible control and error handling algorithms, a 64-bit architecture, and rate and burst flow control. Over large latency or high error rate conditions typical of satellite, wireless, radio, and other long-distance wide area links, XTP provides significantly higher throughput than TCP while maintaining lower bandwidth and CPU utilization.

In addition to high performance, XTP offers protocol-level reliable multicast functionality. XTP reliable multicast provides a highly efficient method of transferring files simultaneously to multiple receivers as well as populating caches, synchronizing distributed databases, or performing distributed computing.

XTP protocol engine designed for efficiency and maximum performance.
Protocol level reliable multicast functionality.
Support for XTP reliable byte stream (virtual circuit) service type.
Support for XTP unacknowledged datagram service type.
Rate and burst flow control.
Runs over IP or directly over the link layer.
Coexistence with TCP/IP and other protocols.

Mentat XTP is licensed as source code designed for easy portability to any operating system. Mentat XTP requires only a System V, Release 4 (SVR4) STREAMS environment and can be combined with Mentat Portable Streams™ (MPS®) for operating systems without a native STREAMS environment.

Mentat XTP is written entirely in ANSI C. Port-specific issues, such as byte ordering, memory alignment, and synchronization primitives, are isolated into macros and system dependent header files. Mentat XTP has been ported to a variety of platforms including Windows NT, Sun Solaris, Wind River VxWorks, and Apple Mac OS without altering the base source files.

Mentat XTP supports the STREAMS-standard Transport Provider Interface (TPI) as its upper layer interface. This design provides access to the protocol from any user library or upper level module written to conform to TPI. Above TPI, Mentat XTP can be integrated with both TLI/XTI and BSD Sockets interfaces.

Mentat XTP runs over IP or directly over a DLPI Version 2.0 compliant STREAMS device. The Data Link Provider Interface (DLPI) permits Mentat XTP to operate with a variety of device drivers and to coexist with other protocols using the same network interface.

Mentat XTP is implemented as a set of STREAMS modules as shown in the accompanying XTP STREAMS configuration diagram.

Device streams are created and configured by an XTP Configuration Daemon which opens a DLPI and/or IP stream and pushes an XTP Interface Module above it. The Interface Module receives inbound packets and passes them to the appropriate XTP application stream for processing.

To create a virtual circuit or to send an unacknowledged datagram, an application opens separate XTP devices. These devices provide the necessary TPI interface to upper layers and deliver outbound packets to the appropriate XTP Interface Module stream.

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