Digital Equipment Corporation

Martin Edward Griesmer

David Benson

Parayath Gopal Krishnakumar

A forwarding information management system for a bridge or router is disclosed, including a method and apparatus for maintaining forwarding entries within a forwarding table. The forwarding table is allocated into forwarding entries, and the forwarding entries organized into forwarding entry sets. A set of free queues is used to manage the free space segments in the forwarding table that are not allocated into forwarding entries. Each free queue maintains pointers to free space segments of a particular size. A forwarding entry adding process creates a new forwarding entry set including a new forwarding entry, selects a non-empty free queue for free space segments large enough to hold the new forwarding entry set, and writes the new forwarding entry set one of the free space segments. Also included in the system are a forwarding entry deleting process, a learning process providing input for the forwarding entry adding process, and an aging process providing input for the forwarding entry deleting process. In an example embodiment, a hash table is used to locate the forwarding entry sets in the forwarding table. In a preferred embodiment, forwarding entries within the forwarding entry sets are organized into balanced binary trees.

Apparatus and method for maintaining forwarding information in a bridge

A forwarding information management system for a bridge or router is disclosed, including a method and apparatus for merging free space segments in a forwarding table. The forwarding table is allocated into forwarding entry sets and free space queues. Each forwarding entry set must be within a single contiguous block of the forwarding table memory. A set of free queues is used to manage the free space segments in the forwarding table that are not allocated into forwarding entries. Each free queue maintains pointers to free space segments of a particular size. The forwarding table becomes fragmented as forwarding entries are added. A table packing process is triggered by a predetermined trigger to merge small areas of free space into large areas of free space, making consecutive forwarding entry sets contiguous in order to combine small areas of free space into larger ones. The table packing process moves the forwarding entry sets in atomic operations to ensure that forwarding entry sets remain valid during the moves, thus allowing forwarding decisions to be made based on forwarding information within the forwarding entry set being moved while the forwarding entry set is being moved. The table packing process further ensures that the forwarding entry sets are efficiently moved such that they are accessible to the hardware frame forwarding apparatus, which is optimized to only read forwarding entry sets that do not cross memory page boundaries.

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Arlington, MA, United States of America

Martin Edward Griesmer