Importance

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Abstract

An apparatus and method of using same for associating a tag with each packet in an ATM switch to eliminate the need for an OVC table, thus saving both egress processing time and memory resources. The tag includes both a type of switching identifier and a per-logical-interface or per-external-VC information field. A packet received by the egress packet processing engine has associated with it (by the control plane) a frame control word containing a new cell header (NCH) corresponding to the OVC on which the packet was received from the fabric. This NCH contains the tag used to expedite egress processing. In one embodiment of the present invention, the tag value is provided in two fields, a tag type and a tag parameter. The tag type represents a code for different data path applications. The tag parameter takes on multiple values based on the tag type. The present invention efficiently uses the OVC to NCH mapping to map many OVCs to a small set of tags coded within the switch's NCH so that, rather than having to do an extra look-up in the egress engine in a large and non-scaleable OVC table, the egress engine has only to look in a small, fully-scaleable tag table. In fact, in one embodiment, no egress look-up is required at all.

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First Claim