Digital Equipment Corporation

Nortel Networks Corporation

David Benson

Martin Edward Griesmer

Yunzhou Li

Bilel N Jamoussi

Peter C Hayden

Paul W Ciarfella

David S Sawyer

Dan Adamski

Parayath Gopal Krishnakumar

Jagannath Shantigram

In a router, externally received messages addressed to an active line card are bridged to a protection line card. Each line card in the router is programmed to respond to such externally received messages by directing them to the protection line card associated with the active line card as well as to the active line card. The protection line card is configured with inbound and outbound path tables that are the clones of the inbound and outbound path tables of its corresponding active line card. Bridging is accomplished by revising descriptors stored in a plurality of line cards to indicate an association between an active one of the line cards and its protection line card. Received messages are addressed using the revised descriptors to the active line card and also to its protection line card. Upon failure of an active line card, its physical interface can be disabled once its protection line card has clones of the inbound and outbound path tables and bridging has been set up.

Mechanism for automatic protection switching in a router

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.

Method and apparatus for free space management in a forwarding database

A method and apparatus for adaptive interrupt servicing is disclosed. The number of interrupts occurring within a predetermined time period is counted and stored as a value in an interrupt counter. At the end of each interrupt service, the interrupt counter value is compared to a predefined threshold value. If the value in the interrupt counter equals or exceeds the threshold value, further interrupt servicing is disabled.

Method and apparatus for adaptive interrupt servicing in data processing

Growing community of inventors

Acton, MA, United States of America

David Benson