RFC 1221 (rfc1221) - Page 1 of 68
Host Access Protocol (HAP) specification: Version 2
Alternative Format: Original Text Document
Network Working Group W. Edmond Request for Comments: 1221 BBN Updates: RFC 907 April 1991 Host Access Protocol (HAP) Specification - Version 2 Status of this Memo This memo describes the Host Access Protocol implemented in the Terrestrial Wideband Network (TWBNET). It obsoletes most but not all of RFC 907. This memo provides information for the Internet community. It does not specify an Internet standard. Distribution of this memo is unlimited. Preface This memo specifies the Host Access Protocol (HAP). HAP is a Network layer (OSI Layer 3 lower) access protocol that was first implemented about a decade ago for the DARPA/DCA sponsored Wideband Packet Satellite Network (WBNET), the precursor of the current Terrestrial Wideband Network (TWBNET). This version of the specification obsoletes references [1] and [2] in addition to most of RFC 907. HAP is a developmental protocol, and will be revised as new capabilities are added and unused features are eliminated or revised. One reason that HAP is being revised now is that, unlike the original WBNET's satellite channel, the TWBNET's T1 fiber links are not a broadcast medium. This has prompted some changes to the protocol that will permit greater efficiency in a mesh topology network. Another cause of revision is the need to make HAP able to support a variety of OSI layer 3 upper protocols, such as DECNET Phase V, ST, and CLNP, where before only Internet Protocol (IP) was used. Appendix B describes how backward compatibility with the older IP- only version of HAP is achieved. A third cause of protocol changes is the desire to simplify interaction between ST2 protocol (RFC 1190) agents and the TWBNET. This has mainly affected the way certain setup errors are handled. These changes are expected to be backward compatible. Appendix A describes two capabilities that may be added to HAP in the future. One of the protocol enhancements, "Group Streams", described in reference [2] has been eliminated. There are no known applications that use the feature. As described in Appendix A, a new mechanism, to be called "shared streams", capable of providing equivalent capabilities will be implemented if needed. Changes in [2] that have been retained include various query/reply control messages that permit a host to determine what resources it owns (mostly useful for Edmond
