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Data Link Switching: Switch-to-Switch Protocol (RFC1434) Disclosure Number: IPCOM000002262D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2019-Feb-10
Document File: 33 page(s) / 40K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

R. Dixon: AUTHOR [+1]

Related Documents

10.17487/RFC1434: DOI


This RFC describes IBM's support of Data Link Switching over TCP/IP. This memo provides information for the Internet community. It does not specify an Internet standard.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 7% of the total text.

Network Working Group R. Dixon Request for Comments: 1434 D. Kushi IBM March 1993

Data Link Switching: Switch-to-Switch 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.


This RFC describes IBM’s support of Data Link Switching over TCP/IP. The RFC is being distributed to members of the Internet community in order to solicit their reactions to the proposals contained in it. 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 should be sent to the following Internet address:

Table of Contents

1. Introduction 2 2. Overview 2 3. Transport Connection 4 3.1. SSP Frame Formats 5 3.2. Address Parameters 8 3.3. Message Types 10 4. Protocol Specification 11 4.1. Protocol Flow Diagrams 11 4.1.1. Connect Protocols 11 4.1.2. Link Restart Protocols 13 4.1.3. Disconnect Protocols 15 4.2. DLS State Machine 16 4.2.1 Data Link Switch States 16 4.2.2 State Transition Tables 21 4.3. NetBIOS Datagrams 30 Acknowledgments 32 References 32 Security Considerations 32 Authors’ Addresses 33

Dixon & Kushi [Page 1]

RFC 1434 DLS: Switch-to-Switch Protocol March 1993

1. Introduction

Data Link Switching (DLS) is a forwarding mechanism for the IBM SNA and IBM NetBIOS protocols. It does not provide full routing, but instead provides switching at the Data Link layer and encapsulation in TCP/IP for transport over the Internet. This memo documents the Switch-to-Switch Protocol (SSP) that is used between IBM 6611 Network Processors.

Today, the IBM 6611 supports SNA (PU 2 and PU 4) systems and NetBIOS systems attached to token-ring networks, as well as SNA (PU 2) systems attached to SDLC links. For the later case, the SDLC attached systems are provided with a LAN appearance within the IBM 6611. For the LAN attached systems, the IBM 6611 appears as a source-routing bridge. Remote systems that are accessed through the IBM 6611 appear as systems attached to an adjacent ring. This ring is a virtual ring that is manifested within each IBM 6611.

2. Overview

Data Link Switching was developed to provide support for SNA and NetBIOS in multi-protocol routers. Since SNA and NetBIOS are basically connection oriented protocols, the Data Link Control procedure that they use on the LAN is IEEE 802.2 Logical Link Control (LLC) Type 2. Data Link Switching also accommodates SNA protocols over WAN links via the SDLC protocol.

IEEE 802.2 LLC Type 2 was designed with the assumption that the network transit delay would be small and predictable (i.e., a local LAN). Therefore the LLC elements of procedure use a fixed timer for detecting lost frames. When bridging is used over wide area lines (especially at lower speeds), the network delay is larger and it can vary greatly based...