Importance

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Abstract

In a network device such as a network switch having a port coupled to a communications medium dedicated to a single virtual local area network and another port coupled to a communications medium shared among multiple virtual local area networks for transmitting data frames between the dedicated communications medium and the shared communications medium, a method of identifying the virtual network associated with each data frame received by the network switch when transmitting the data frames over the shared communications medium. The method comprises receiving data frames from the dedicated communications medium coupled to one port, and, with respect to each data frame so received, inserting a type or length field and a virtual network identifier field either between or before the Ethernet type field (of an Ethernet data frame) or the length field (of an IEEE 802-based data frame) and the data field, placing the contents of the Ethernet type or length field in the inserted type or length field, changing the contents of the Ethernet type or length field to indicate the data frame comprises a new type field and a virtual network identifier field, placing a value in said virtual network identifier field identifying the virtual network associated with the data frame, and, transmitting the data frame over the shared communications medium. Upon receipt of the data frames from over the shared communications medium, another network device can discern from the virtual network identifier field in each data frame the virtual network from which the data frames were received and determine whether to forward the data frames accordingly.

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First Claim