T he so-called network computer (NC) aims to give users access to centralized resources from simple, inexpensive devices. These devices act as clients to more powerful server machines that are connected to the network and provide applications, data, and storage for a user's preferences and personal customizations. We have taken this idea a stage further. In the virtual network computing (VNC) system, server machines supply not only applications and data but also an entire desktop environment that can be accessed from any Internet-connected machine using a simple software NC. Whenever and wherever a VNC desktop is accessed, its state and configuration (right down to the position of the cursor) are exactly the same as when it was last accessed.In contrast to many recent Internet applications, which have focused on giving users access to resources located anywhere in the world from their home computing environments, VNC provides access to home computing environments from anywhere in the world. Members of the Olivetti & Oracle Research Laboratory (ORL) use VNC to access their personal Unix and PC desktops from any office in our Cambridge building and from around the world on whatever computing infrastructure happens to be available-including, for example, public Web-browsing terminals in airports. VNC thus provides mobile computing without requiring the user to carry any device whatsoever. In addition, VNC allows a single desktop to be accessed from several places simultaneously, thus supporting appli-VNC is an ultra-thin client system based on a simple display protocol that is platformindependent. It achieves mobile computing without requiring the user to carry any hardware. *Andy Hopper is also affiliated with Cambridge University Engineering Department.cation sharing in the style of computer-supported cooperative work (CSCW).The technology underlying VNC is a simple remotedisplay protocol. It is the simplicity of this protocol that makes VNC so powerful. Unlike other remote display protocols such as the X Window System and Citrix's ICA, the VNC protocol is totally independent of operating system, windowing system, and applications (see the sidebar, "Thin Clients"). The VNC system is freely available for download from the ORL Web site at http://www.orl.co.uk/vnc/.We begin this article by summarizing the evolution of VNC from our work on thin-client architectures. We then describe the structure of the VNC protocol, and conclude by discussing the ways we use VNC technology now and how it may evolve further as new clients and servers are developed.

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RFB ("remote framebuffer") is a simple protocol for remote access to graphical user interfaces that allows a client to view and control a window system on another computer. Because it works at the framebuffer level, RFB is applicable to all windowing systems and applications. This document describes the protocol used to communicate between an RFB client and RFB server. RFB is the protocol used in VNC. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6143.

Previous work has described teleporting, an approach to mobile computing in which it is the user's personal application environment which is mobile rather than the hardware on which the applications run. In this paper we describe a new teleporting system which makes the user's environment available on any machine in the world running a Java-compliant web browser. We present some preliminary experimental results together with discussions of security and performance issues.

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