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FAQ |
X Web FAQ
In addition to the
Frequently Asked Questions below, you may find further
information about X Web on the X Web Users mailing list.
Low Bandwidth X FAQ
BROADWAY was originally the code name for an initiative from the X Consortium which was aimed at delivering Web capability to X. The code name has remained as the popular handle for the latest release of the X Window System Version 11 Release 6.3. The easily recognizable term "X Web" is also used to describe Web-enabled X access.
X Web allows X applications to be distributed via Web protocols. That is, a user may browse a corporate intranet (or the Internet) and click on a link within an HTML page to launch an X client. The application will then display within the Web-browser.
X Web architecture includes five key components:
- Remote Execution - provides the mechanism to remotely launch an X application.
- Universal Access - is provided by integrating X11R6.3 with HTTP protocols making it platform independent, hence widely available.
- Web browser plug-in - works with Remote Execution and provides the glue between X client display and a browser.
- Security - distinguishes between Trusted (internal) and Untrusted (external) applications. There are three pieces to security: an extension to the PC X server, a piece of code on the firewall and a security manager that interfaces with the user to authorize data exchanges between trusted and untrusted applications.
- LBX (Low Bandwidth X) - was designed to improve the performance of X on WANs and slow dial-up connections. Techniques include caching, compression and short-circuiting.
The benefit of X Web is the ability to centrally deploy and manage X application access while eliminating the costs associated with training users on the semantics of the X Window System protocol.
Anyone who wishes to deliver access to corporate applications via an intranet or the Internet is a candidate for X WEB. The alternative method available today for launching graphical UNIX applications via a Web browser include Java. The Java method involves re-coding applications and employing less than acceptable graphics widgets. The investment protection of X Web make it an ideal solution for enterprise deployment via Web protocols.
You need an X server that fully supports X11R6.3, the latest X Window System Release from The Open Group.
How do I enable X Web on a Web server?
The specific details are beyond the scope of this FAQ but in short you will need to do the following:
- add an <embed> tag in an HTML page for the X client
- configure the Web server to understand the Xrx MIME type
- a CGI script that is called when a user clicks on an <embed> link that launches the X client
Where do I get what I need to use X Web?
Beyond an X server that fully supports X Web (X11R6.3) there is nothing else to seek. Refer to the LBX faq for information on where to get the correct LBX proxy for your server.
Do I need to re-code my X applications to Web-enable them?
No. X Web was designed to be application friendly and transparent. Re-coding applications is not necessary.
Can I protect my data from attacks?
Yes. BROADWAY (aka X11R6.3) includes a SECURITY extension which differentiates between Trusted and Untrusted applications thereby allowing for protection of data. An X server must explicitly support the extension. Currently, not all X servers fully support X11R6.3 and hence may not support SECURITY.
The SECURITY extension includes management of:
- Keyboard security - controls which clients have access to incoming keystrokes.
- Image security - manages which clients have access to the image contents of other trusted windows.
- Property security - monitors the activities of clients that try to access/change X properties of other applications.
- Manages the Trusted Hosts List
Is X Web designed for use across the Internet?
Yes. X WEB includes explicit support for distributing applications across the Internet, including an enhanced SECURITY extension, X Firewall Proxy support and a security manager that interfaces with the user to authorize data exchanges between Trusted and Untrusted applications.
How do I pass through the corporate firewall?
Passing through a firewall requires two things. First, you require an X server that fully implements X11R6.3 (BROADWAY) including Proxy Management Protocol and SECURITY as well as support user based authentication. Second, a small piece of code, known as xfwp, must run on the firewall. Xfwp is the proxy that forwards X requests from a remote client to an X server behind a firewall.
How does X Web compare to Java?
Java requires a re-write of existing code to Web-enable applications. X11R6.3 (BROADWAY) was designed to be transparent to applications and requires no re-coding. Both Java and X11R6.3 (BROADWAY) have a future in Web-delivery of applications. X11R6.3, however, has the advantage of protecting existing technology investments.
Can I run intricate applications detached from my browser window?
This depends on how the X client was configured to be displayed by the Web master (or system administrator) and the X server being used. The application can be configured to run embedded or externally.
What is an "embedded" X client?
An X client that displays within a browser is said to be "embedded" when a user can not "detach" it and display it outside of the browser, much in the same fashion as one can not detach a document from within Microsoft Word.
An X client is typically "configured" by the system administrator (or Web master) to run either embedded or externally to the browser.
Can I print from my X applications directly to a local or network redirected printer?
Yes. X Web includes an extension known as XPRINT. XPRINT permits an X client to print though Windows GDI to a local or network attached printer. Currently, not all X servers implement this extension. To verify support run xdpyinfo and look for the XPRINT extension.
Can I run selected applications across the Web while simultaneously denying host access?
Yes. This is the way X WEB was meant to be run. The new security extensions permit running Web applications while denying any host based access. Note though, that the X Firewall Proxy uses User based authentication, therefore your X server must support both user and host based access control.
What security must my X server support to run through a firewall?
Your X server must support three security models - user and host based authentication and the SECURITY extension of X11R6.3.
- User based authentication allows connection to the Xfwp proxy on a firewall.
- Host based authentication permits greater security within the X Web model, permitting a user to display X clients within a browser while simultaneously denying any host based access.
- The SECURITY extension of X11R6.3 includes explicit support for the definition of Trusted and Untrusted applications, the Xfwp proxy and an extension to the X server which secures data.
Low Bandwidth X FAQ
LBX, X.Fast,
Serial X, Dial-up X
What
is LBX?
LBX (Low Bandwidth X) is an open standard serial X technology from The Open Group, the governing body of the X Window System, and is part of the X Window Version 11 Release 6.3. LBX addresses the performance issues associated with running X clients across high latency dial-up or WAN connections.
LBX has also been referred to as X.Fast.
Anyone who regularly accesses X applications across slow connections such as dial-up or WAN is a candidate for LBX. The X Window protocol has been optimized for high speed LAN connections. The verbose nature of X - which may generate a considerable amount of network traffic - is not well suited for high latency media. LBX uses advanced caching, compression and short-circuiting techniques to improve X client response times.
While technically possible to run LBX across LANs you may find no perceivable benefit from doing so. The X Window protocol was optimized for LANs. LBX’s additional overhead - compression and caching - may tend to slow overall performance - although it may result in a reduction of network traffic.
LBX in principle introduces a "proxy server" on the host which oversees caching and compression. X clients "speak" to the proxy instead of directly to the X server. The proxy in turn forwards X requests to the X server. Since LBX is an extension to the X server no further configuration is required.
A further advantage to LBX is that the proxy is encompassed in a single executable. No cumbersome configuration or run control files are required.
First, to run LBX you require an X server that supports X11R6.3 better known as BROADWAY, the latest X Window System release from The Open Group. Secondly, you will need the LBX proxy server for the host you are connecting to. Currently, you should speak to your host vendor for the availability of lbxproxy - note: you should quote them the version of your operating system.
Where do I get what I need to run LBX (lbxproxy)?
Currently, lbxproxy is available as part of the distribution of X11R6.3 in source form. To get lbxproxy for your operating system you have a few alternatives.
- Refer to your UNIX vendor. They should make lbxproxy available.
- Download and build lbxproxy from the X11R6.3 distribution from The Open Group.
- Find a source that provides the lbxproxy binary.
- Refer to the Web Page at http://www.broadwayinfo.com for frequent updates. As binary proxies become available these sites will be referenced.
Do I need to make any code changes to my X applications?
No. LBX is transparent to all X clients. You will not have to recode applications to take advantage of LBX.
To start LBX:
- Make the dial-up connection as per normal.
- Ensure that the remote system has "access" to your X server. Add it via ‘Xhost +remote’ or if using a PC X server (such as Exceed) ensure Host Access Control is disabled, or add the remote host discreetly)
- Start the X server
- Run Telnet or launch an xterm on the remote host (or Rexec the following lbxproxy command)
- Run lbxproxy in a fashion similar to this on the remote system: (requires a remote shell)
- %remote: lbxproxy :22 -display my_ip:0&
{Where my_ip is your IP address & 22 is the correct display number}
- Launch X clients. Any X client on DISPLAY remote:1 will use LBX.
LBX uses advanced compression, caching and "short-circuiting" techniques to enhance the responsiveness of X clients over slow (high latency) links, such as modems and WANS. The exact technical description of "how" LBX performs these functions is beyond the scope of this FAQ.
Further information may be found at http://www.opengroup.org.
How does LBX compare to other technologies like Serial Xpress?
Serial Xpress from Tektronix is a proprietary protocol and transport technology popularized through bundling by Hummingbird. Over the last few years support for running Xpress over IP was added to facilitate the desire to run non-X winsock applications over the same connection (such as e-mail or a browser).
Technically the technologies are similar in function, but differ in approach. LBX is an industry standard extension to the X server. LBX extends the Xpress performance benefit by adding caching and enhanced compression. Both Xpress and LBX work with a proxy on the remote host forwarding X requests to the X server.
Can I use other IP applications when using LBX?
Yes. LBX is an extension to the X server and is not concerned with the transport. That is, LBX is not a proprietary transport protocol and will run on TCP/IP including SLIP, CSLIP and PPP. Therefore, IP applications are not affected.
How does LBX compare to straight PPP/SLIP/CSLIP?
The X protocol is verbose, that is, bandwidth consuming for seemingly simple tasks. Both X and TCP/IP encoding of the X protocol is optimized for high speed LANs. While casual use of X over dial-up may be survivable, prolonged use can quickly become frustrating. It should be remembered that X applications behave differently and therefore their use over slow dial-up may cause varied results. That is, some widgets and drawing operations can perform as well over SLIP/PPP compared to Xpress, yet other operations continue to be handled up to ten times faster via Xpress.
SLIP - Serial Line IP: This is a protocol for transmitting IP packets over a serial interface. It has existed for several years and is now thought to be stable and passé. Use of X over SLIP is slow at best, however, some requests can be dealt with quickly enough to make SLIP acceptable - this is application specific.
CSLIP - Compressed header SLIP: a variant of SLIP that compresses the "heavy" 40 byte IP headers down to 5 or 6 bytes. Like SLIP, CSLIP does not re-encode X, hence there may be no perceivable performance benefit.
PPP - Point to Point Protocol: The defacto standard for dial-up links with more option negotiations than SLIP. Running X over PPP still requires re-encoding of the protocol and compression to make it truly useable.
LBX - Low Bandwidth X: The
industry standard for dial-up X from The Open Group. LBX
enhances performance through reduced packet generation by
caching commonly used information such as, connection
setup, large window properties, font metrics, keymaps
etcetera. Compression also enhances performance.
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