Multiport data switch having variable maximum packet length

摘要

A multiport data network switch includes a programmable Management Information Base (MIB) configuration register that serves as a reference for the Media Access Controller (MAC) at each port. The register is programmable for maximum packet length in two configurations. In a first configuration, the maximum packet length setting is constant for all ports. In the second configuration, the maximum packet length is set at a plurality of levels in accordance with certain dynamic conditions. On an untagged port, or on a tagged port capable of communicating with a Virtual Local Area Network (VLAN) that receives/transmits an untagged frame, the maximum packet length criterion is a first value. On a tagged port that receives/transmits a VLAN tagged frame, the maximum packet length criterion first level is expanded by the number of bytes required for the VLAN tag.