Overview
ISO/IEC TR 11802-5:1997 (ANSI/IEEE Std 802.1H, 1997) is a Technical Report that provides extensions and guidelines for Media Access Control (MAC) bridging of Ethernet V2.0 in local area networks. It addresses interoperability issues when CSMA/CD LANs (a mix of ISO/IEC 8802-3 and Ethernet V2.0 end stations) are bridged to other IEEE 802 networks (e.g., Token Ring, FDDI). The report clarifies expected bridge behavior, describes techniques such as selective translation, and gives protocol designers guidance to avoid future incompatibilities.
Key Topics
- Bridging extensions to ISO/IEC 10038 (IEEE 802.1D): Recommended behavior changes to MAC bridges to support Ethernet V2.0 frames in bridged LAN environments.
- Ethernet V2.0 vs IEEE 802.3 frame structure: Discussion of the difference between the Ethernet “type” field and 802.3 “length” field and implications for forwarding.
- SNAP / RFC1042 interoperability: Analysis of the Subnetwork Access Protocol (SNAP) and the RFC1042 mechanism used to carry Ethernet-type values over IEEE 802 LANs, including known conflicts and interoperability problems.
- Selective translation and translation tables: Concepts for selectively translating or handling frame formats at bridges to preserve interoperability between mixed-endstation networks.
- Guidelines for nonstandard and legacy protocol migration: Advice for converting existing Ethernet-based protocols and designing new IEEE 802 protocols to work cleanly with MAC bridges.
- Interoperability restoration: Recommended practices to restore or maintain interoperability when conflicting uses of encapsulation mechanisms arise.
Applications and who uses it
This Technical Report is practical for:
- Network architects and system integrators designing bridged LANs that mix Ethernet V2.0 and IEEE 802.3 stations.
- Network equipment vendors and firmware developers implementing MAC bridge behavior, translation tables, and SNAP handling.
- Protocol designers migrating legacy Ethernet protocols to IEEE 802 environments or creating new MAC/LLC-aware protocols.
- Operations and support teams troubleshooting interoperability issues in heterogeneous LANs (CSMA/CD, Token Ring, FDDI).
Practical uses include configuring bridges to forward or translate frames correctly, planning protocol migrations to avoid RFC1042 conflicts, and ensuring multi-vendor bridged LAN interoperability.
Related Standards
- ISO/IEC 10038 (IEEE 802.1D) - MAC Bridging architecture and protocol
- ISO/IEC 8802-3 (IEEE 802.3) - CSMA/CD access method and physical layer
- IEEE Std 802 family (802.2, 802.1, 802.5, etc.) - LAN/MAN architecture and access methods
- RFC 1042 - IP over IEEE 802 networks (SNAP encapsulation)
Keywords: ISO/IEC TR 11802-5:1997, MAC bridging, Ethernet V2.0, IEEE 802.1H, CSMA/CD, RFC1042, SNAP, selective translation, ISO/IEC 10038, LAN interoperability.