Closing on Broadway: Can the final X11 spec survive the Internet and NCs? What are the new features of the X Consortium's Broadway, and how do they improve Web integration, application access, printing, and security?

February  1997

The X Consortium's latest and last release of the X11 networked display environment, X11 Release 6.3 or Broadway, opens a new area of communications using this important and ubiquitous environment in the workstation world. Broadway introduces elements such as integration with Web servers, universal access to applications, improved low-bandwidth network communications, network printing, and networked audio. (2,200 words)

Mail this article to a friend

The style and pizzazz of one of the most well-known streets in the world has brought the glimmer of hope to many an eye. If you can make it there, you can make it anywhere, to borrow a line from Old Blue Eyes, Frank Sinatra.

In a similar vein, the X Consortium attempted to provide a unified vision for the networked computer world. X11 Version 6.3, code-named Broadway, will be the last version of the X Window System protocol to be released by the X Consortium. With this final release, the X Consortium will merge with, or more accurately, be subsumed by, the Open Group. Any future releases of X Windows will come from this other standards body. It is sad to see such a group, which has popularized network computing usage to such a high degree, fade.

The X11 network display system has been one of the most popular desktop environments in the history of computing. Even when Macintosh and Windows users were declaring how easy to use, yet powerful, their desktop environment was, the X11 desktop has superceded any and all such work in many areas. Although they seem to be catching up, the native Windows and Macintosh desktops have yet to offer many of the features of the X11 protocol.

Once predominantly used on Unix workstations and dedicated X-terminals, X11 has since spread to PC desktops and even given the old guard a good run for the money. PC X-server software packages run alongside, or even replace, the native desktop environment. You can now display Unix and other network applications directly at the same cost, or even lower cost, on a PC than on a good X-terminal.

In fact, even though I run Microsoft Windows 95 and NT on my system, most of my time is spent on xterms (a graphical terminal window to remote hosts) connected to our various Unix hosts or running the X11 version of Emacs. The Windows side comes in handy every now and then as both a contact manager and a way to do reports in Microsoft Word.

As a quick reminder, the X environment uses slightly different concepts than those of typical network displays. Each workstation or desktop runs an X-server software package, which allows you to start applications from remote hosts. These applications are called X clients.

This is the opposite of Virtual NT products in which the software on the local workstation is called the client and the Virtual NT server hosts the actual display server. All processing of graphical elements is performed on the X server on the local desktop, vastly speeding up the display process. Actual actions to be performed to the application are sent back to the remote host, and all actual application processing is performed on the remote host. This creates the traditional X11 based thin-client environment.

To X or not to X, that is the question
If you are wondering why the X Consortium is fading from view, just consider the growth of the Web over the past three years. Users now see how much easier it is to create HTML documents and applications. In spite of the bare bones structure and reduced functionality, a large number of X11 users have instead become Web users.

There isn't a complete switchover, of course. The function of X11 is quite different than mass-scale, Internet-wide document access. X11 is mostly for accessing network applications; however, with the promulgation of intranets, developers are moving towards using Web servers and database tools rather than specialty X11 applications.

Many of the applications for low-bandwidth access of networked information now fall within the scope of Web/intranet. Perhaps the recent additions to X11 in the Low-Bandwidth X (LBX) arena have arrived too late.

Additionally, X11 programming is much more technical than HTML and CGI scripts. Furthermore, the X Consortium now feels that X11 is mature enough to stand on its own without the support of a standards body. Any further development beyond what is in Broadway would stretch the intended use of X too thin.

It is, however, very unlikely that X11 will die anytime soon. Almost all Unix servers and workstations created in the past seven years have some form of graphical display system available based upon X11. There are some variants and extensions to the protocol, but the basic protocol itself has remained the same for at least three years now.

The widespread usage of X11 is due mostly to the work of the X Consortium in making it publicly available without cost. With Web browsers you still have shareware concerns; X11-based servers have been available for most of the popular Unix platforms for free and without any limitations. X11 for more custom environments, like the Macintosh and Windows, have been commercial for some time. With the Unix market wrapped up, the commercial PC-X market has done well on its own.

Broadway melody: Key features outlined
Broadway, which has been in the works for the past two years, has been eagerly anticipated. Vendors who could not wait for the X Consortium had already gone ahead and implemented some of the concepts of Broadway in their own products. Broadway, nonetheless, represents the unification of some nonstandard extensions into an acceptable cross-vendor format.

Some of the included features and standards in Broadway:

• X.Fast Extension 96: a protocol for using X applications over a low-speed network such as a dial-up line, or across the spread of the Internet. X.Fast was once known as the Low-Bandwidth X (LBX) protocol.

  Traditionally, X11 was perfect for 10 megabit-per-second Ethernet environments, but performed poorly over serial lines or modems. Having run X11 client applications over a 14.4 kilobits-per-second mode in the past, I know that such poor performance is severely discomforting. X.Fast provides features such as protocol data compression, caching, and short-circuiting.

• Remote X (RX) 96: a new remote execution MIME type. This allows integration with Web browsers to allow X clients to be launched by and displayed within the browser using plug-in technology. The RX protocol works in conjunction with your Web browser and Web server in addition to the X-server.

  When you access a Web page that has a link to or contains an X client application, the browser contacts the remote Web server requesting a specific application. The Web server must be configured to understand the proper MIME type which matches the RX protocol. Through a CGI script, the application is launched. This X client application must, of course, be programmed with RX functionality. On a Unix system, the client will use the system libraries and the X11 or Motif libraries to pass the calls.

  On a Windows NT system, the client application will use the NT Graphics Device Interface to pass the calls. In either case, if X.fast is also installed, it may pass through these layers as well.

• Security Extension 96: an expansion of the security system to include more information to distinguish trusted and untrusted client applications. This high-level security mechanism allows applications to distinguish each other's security levels. There are several different elements to this new extension.

  Extension security manages the effects of dynamic extensions on the client applications. Keyboard security manages which applications have access to the keystrokes coming into the event queue, so that only properly registered applications receive keystrokes for processing. Image security manages which client applications have access to the image contents of other trusted windows. Property security monitors the activities of applications that attempt to check or set the X property values of other applications. Finally, there is a miscellaneous security mechanism to watch which applications can affect the list of trusted hosts that can display on your X server.

• Print Extension: a new network printing protocol through the X11 protocol. Although network printing has been available through Unix servers for well over a decade, printing through X client applications required a separate mechanism through the Unix filesystem. With XPRINT services, you can now have a client application print directly to a network printer through the graphics context. Rather than having to translate the graphics context into a different format, the X-server can now have a print server system that communicates directly with the printer. This is also platform neutral so it will work with Unix or NT systems. This new print system can be used directly with Raster device printers, Postscript level 2, and color or monochrome PCL printers.

• Application Group Extension 96 allows multiple programs to have control access of applications on the X desktop. Web applications can be controlled by the Web browser, for example. These applications are each group members controlled by the Group Leader (the Web browser), and events that happen to the leader, or are generated by the leader, can be sent to individual group members.

• X-Agent 96 allows special X client applications to have real-time access to interface and graphics of other X clients. Together with the Security extension and the Application Group extension, this allows one client application to monitor or receive the output of another in real-time. It is important mainly for 3D and heavy-graphics applications where in the view of an object may need to be sent to several applications at the same time.

• Proxy Management Protocol 96 creates the ability to use proxy services, such as running an application through a firewall. The X-server uses TCP and/or UDP network ports just like any other network application. Each application in turn also uses one or more network ports for communicating with the X-server and/or other network applications. With the new proxy protocol, a standard format is available for relaying X11 data through firewalls and other network security guards.

• Network Audio 96: after all these years, networked audio in X11 is becoming standard. A separate audio server runs alongside the X-server. This component is necessary to communicate the flow of data through the proper devices and mechanism. Users can play and record across the network.

  Additionally, the audio clips can be synchronized with other events or applications, making it ideal for teleconferencing and voice annotated applications. X11 is, however, limited in audio quality to support the capabilities of networks. Currently it is only supported in the Unix environment with NT device drivers still to come.

What's the future of X11?
The RX protocol is the first to provide universal access from all graphical Unix- and Windows NT-based applications to any platform with an X-server. This means that you can launch Windows or Unix applications within your browser. When we discussed the ICA protocol in last month's issue, we saw a similar situation with products like Citrix WinFrame, which allows you to launch and display Windows NT applications inside your browser. In products such as NCD's PC X-ware, Santa Cruz Operation's XVision, and other PC-based X-server products, you can also launch Unix-based X11 applications within your Web browser.

Broadway finally brings these two elements together into one common protocol. The catch is, of course, that you need an X-server on your workstation, as well as the remote server. However, this common protocol works for both Unix and PC X-servers. With one X-server on your host server and others on each desktop, you can access the network servers without the expensive licensing costs of Virtual Windows NT products such as WinFrame, NTrigue, WinCenter. This could mean hundreds of dollars of savings per desktop.

Network audio capabilities have long been available through vendors such as NCD. other more popular Internet companies, however, have risen to the top of the network audio pyramid. Companies such as RealAudio, VoxWare, and StreamWorks have proprietary file encoding and streaming protocols to help speed the delivery of network audio over WANs. While X audio does perform very well over a LAN, it remains to be seen if this new standard will gain a foothold on the WAN environment.

Recent news of a collaboration of 40 Internet vendors, including Netscape and RealAudio on a new protocol known as the Real-Time Streaming Protocol (RTSP) may just be the nail in the coffin for X audio.

Leading vendors in the PC X-server market, such as Hummingbird and Walker Richer & Quinn, are already working on software that incorporates the Broadway specifications. Some have already taken the leap ahead and created their own protocols, primarily for serial network connections; X.Fast took too long to arrive, and other protocols like SerialXpress from Tektronix have taken some hold already.

There is reason to believe that many other vendors will also incorporate these features as well into their products, including X-terminal and X-terminal-based Network Computer vendors.

While the future of the X11 remains cloudy, it is unlikely to disappear from view anytime soon. Developments like the intranet and the NC revolution, however, are offering alternatives that seem either more affordable or at least receive more press coverage. Still, the Broadway specification goes a long way towards addressing many issues for X11. In any case, I would like to extend my thanks to the X Consortium for its long-standing contribution to the world of networked computing; X11 is a product that has stood the test of time and has survived unfailingly.

Resources

• Sites where you can download Broadway
  http://www.x.org/consortium/GettingX11R6.3.html
• Release notes for Ver. 6.3
  http://www.x.org/consortium/R6.3doc/relnotes/RELNOTES.html
• The X Consortium home page
  http://www.x.org/
• The Open Group home page
  http://www.opengroup.org
• The Broadway Audio System white paper
  http://www.x.org/consortium/audio/xtech96.html Universal Access to Interactive Applications over the Web http://www.x.org/consortium/bwaywww5/index.html
• The Real Time Streaming Protocol (RTSP) Resource Center
  http://www.realaudio.com/prognet/rt/index.html
• Last month's Connectivity column titled "Virtually NT on Unix"
  http://www.sunworld.com/swol-01-1997/swol-01-connectivity.html
• More on PC connectivity
  /sunworldonline/common/swol-siteindex.html#pcconnectivity
• A list of other Connectivity
  /sunworldonline/common/swol-backissues-columns.html#connectivity

About the author
Rawn Shah is vice president of RTD Systems & Networking Inc., a Tucson, AZ-based network consultancy and integrator. Reach Rawn at rawn.shah@sunworld.com.

If you have technical problems with this magazine, contact webmaster@sunworld.com

URL: http://www.sunworld.com/swol-02-1997/swol-02-connectivity.html
Last modified: