Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-12-18
2001-05-22
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S422000
Reexamination Certificate
active
06236654
ABSTRACT:
TECHNICAL FIELD
The present invention relates to network communications and more particularly, to a method and apparatus for managing an address table of a network switch.
BACKGROUND ART
In computer networks, a plurality of network stations are interconnected via a communications medium. For example, Ethernet is a commonly used local area network scheme in which multiple stations are connected to a single shared serial path. These stations often communicate with a switch located between the shared data path and the stations connected to that path. Typically, the switch controls the communication of data packets on the network. The switch passes data frames received from a transmitting station to a destination station based on the header information in the received data frame, including source address and destination address.
One arrangement for generating a frame forwarding decision uses a direct addressing scheme, where the network switch includes a fixed address table storing switching logic for the destination addresses. Such arrangements, with fixed address tables, are typically unable to dynamically learn new addresses of stations that may have been added to the network after the initial configuration. A further problem with such arrangements is that a data packet is often “flooded” to all of the connected stations when the source or destination address is not found in the address table. This causes unnecessary transmission of data to stations that may end up discarding the packet, wasting both processing time and data throughput.
SUMMARY OF THE INVENTION
There exists a need for a switching device that dynamically adds entries to an address table for frames with station addresses not contained in the address table.
There is also a need for a switching device that controls data forwarding to limit unnecessary processing for packets with station addresses that are not contained in the address table.
These and other needs are met by the present invention, where data received by the network switch is routed to an internal decision making engine that includes an address table. The internal decision making engine searches the address table and adds a new entry if the search is not successful. The new entry may be used in subsequent searches to generate frame forwarding information.
According to one aspect of the invention, a network switch is configured for controlling the communication of data frames between stations. The switch includes a table for storing address information. The address information includes both source addresses and destination addresses. The switch also includes a control device that receives information from the data frames and searches the table for data forwarding information, based on the received information. The control device adds an entry to the address table when the search is unsuccessful.
Another aspect of the present invention provides a method for adding an entry to an address table. The method includes receiving data frames from stations connected to a multiport switch and performing a search of the address table for an entry having a specified source address and receive port number. If the search does not yield a match for the source address and receive port number, an entry is added to the table.
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Advanced Micro Devices , Inc.
Elallam Ahmed
Kizou Hassan
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