Advanced SNA/IP : A Simple SNA Transport Protocol
RFC 1538
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RFC - Informational
(October 1993; No errata)
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2013-03-02
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RFC 1538 (Informational)
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Network Working Group W. Behl
Request for Comments: 1538 McDATA Corporation
Category: Informational B. Sterling
McDATA Corporation
W. Teskey
I/O Concepts
October 1993
Advanced SNA/IP : A Simple SNA Transport Protocol
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. Distribution of this memo is
unlimited.
Abstract
This RFC provides information for the Internet community about a
method for establishing and maintaining SNA sessions over an IP
internet. While the issues discussed may not be directly relevant to
the research problems of the Internet, they may be interesting to a
number of researchers and implementors. Any questions or comments
relative to the contents of this RFC may be sent to the following
Internet address: snaip@mcdata.com.
Table of Contents
1. Introduction.................................................. 2
2. Motivation and Rationale...................................... 2
3. SNA/IP Protocol Specification................................. 3
3.1 Glossary..................................................... 3
3.2 Conventions and Assumptions.................................. 3
3.3 The Protocol................................................. 3
3.3.1 Connection Establishment................................... 3
3.3.2 Data Transfer.............................................. 5
3.3.3 Connection Termination and Loss............................ 6
3.3.4 Session Data Flow.......................................... 7
3.3.5 State Transition Table for the Initiating Node............. 8
4. LLC to SNA/IP Conversion...................................... 8
5. Performance................................................... 8
6. VTAM Definition............................................... 9
7. Acknowledgments............................................... 9
8. References.................................................... 9
9. Security Considerations....................................... 10
10. Authors' Addresses........................................... 10
11. Disclaimer................................................... 10
Behl, Sterling & Teskey [Page 1]
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 [Page 2]
RFC 1538 Advanced SNA/IP October 1993
3. SNA/IP Protocol Specification
3.1. Glossary
Data Link Switching (DLSw) - This is best described as a routing
protocol used for the conversion of LLC-based SNA sessions to an IP
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