Klaus H. Wolf ----------------------- wolf@cobrow.com ----------------------- TCP & UDP ----------------------- The protocol has been defined independent of the message format. But an HTTP encapsulation of the protocol is currently used. The internet draft draft-iesg-using-http-00.txt has been taken into account. This HTTP encapsulation variant is regarded as the default encoding. It is documented by the internet draft draft-wolf-vpp-00.txt. If other encoding variants will be used in the future, then they will use the same port numbers. Protocol engines distinguish encoding variants by the first 4 octets of each message. The following fields are used: request: protocol-version, subject, property, method, attributes, additional-data. response: protocol-version, response-code, additional-data. Additional-data is always accompanied by data-length and data-type. ------------------------- request, reply ------------------------- ENTER, LEAVE, LINK, UNLINK, SUBSCRIBE, UNSUBSCRIBE, GET, NOTIFY ------------------------- A client sends a request and must wait for a reply from the server. If TCP then requests and responses can be pipelined on a single connection. ------------------------- The purpose of the Virtual Presence Protocol (VPP) protocol is to enable the exchange of document based virtual presence information. Virtual presence information is the foundation for virtual neighborhood services which provide users with information about virtual neighbors, i.e. other users who are close within the virtual document space. VPP enables the creation of dynamic vicinities based on hypertext references. It augments online presence (PIP) with location information. The protocol described in this document is based on 2 years of experience with location based virtual presence. ------------------------- System Port ------------------------- The virtual neighborhood service (VNS) provides users with informa- tion about virtual neighbors, i.e. other users who are close to each other in terms of the documents they are presented with. The VNS is a network of loosely coupled VPP servers. Information about the registration of users with locations is exchanged between a VPP client and a VPP server. On the other hand VPP servers exchange information about users and locations. Both VPP clients and VPP servers need a well known port number at which they can expect the virtual neighborhood service. The reason for the application for a system port is that the experience shows that the VNS is a system level service. It is usually installed once per domain or once per HTTP server. The service must definitely be installed and maintained by a site operator. Please contact wolf@cobrow.com, if you need further information. An internet draft is available from the on-line Internet-Drafts directories, e.g.: ftp://ftp.ietf.org/internet-drafts/draft-wolf-vpp-00.txt ------------------------- VPP -------------------------