The IBM 8209 LAN bridge

The issues involved in bridging 802.5 (token-ring) and 802.3 (Ethernet) networks at the media access control (MAC) layer are discussed. The issues concern incompatibilities between the two networks in six areas: routing schemes, station addresses, frame formats, and local area network speeds. An approach incorporated in the IBM 8209 LAN bridge for resolving the incompatibilities is described. The IBM 8209 LAN bridge, a two-port MAC bridge, supports source routing on the token ring/802.5 side and transparent bridging on the Ethernet/802.3 side. Recently proposed changes in the token-ring source routing standards are discussed.<>