RFC 1538 (rfc1538) - Page 2 of 10
Advanced SNA/IP : A Simple SNA Transport Protocol
Alternative Format: Original Text Document
RFC 1538 Advanced SNA/IP October 1993 1. Introduction Advanced SNA/IP suggests a method for the transmission of SNA session data over an IP network. This memo documents the SNA/IP protocol as implemented in the McDATA LinkMaster(R) 6200 Network Gateway, McDATA LinkMaster(R) 7100 Network Controller, and I/O Concepts X-Direct TN3270 Server. Advanced SNA/IP differs from other protocols designed to enable routing of SNA session traffic over an IP network. SNA/IP was originally designed for implementation in peripheral network nodes like SNA gateways and downstream nodes (DSNs). It is the authors' view, however, that SNA/IP could also be implemented in intermediate network nodes like routers as the base for an LLC to IP subnet gateway or data link switch function. 2. Motivation and Rationale The token-ring media access control (MAC) protocol 802.5 and logical link control (LLC) protocol 802.2 were the first set of LAN protocols used to provide a reliable and connection-oriented data link service for SNA sessions in a LAN environment. McDATA's experience with transporting SNA over 802.5 networks led to an 802.3/802.2 (Ethernet) based variation. As prospective customers were introduced to these Ethernet products, the question of routability arose. Network administrators, accustomed to working with Ethernet networks and the IP-based protocols, required an IP routable solution. McDATA's "SNA over Ethernet" products were bridgeable, but were not routable. SNA sessions require a reliable and connection-oriented data link. TCP running over IP provides a reliable and connection-oriented transport service and has the added benefit of being routable. It seemed the UDP and TCP protocols could be used in place of 802.2 Type I and Type II levels of service used in traditional SNA token-ring implementations. Advanced SNA/IP was created as a result of these observations. Behl, Sterling & Teskey
