Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-12-18
2001-07-31
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S392000, C370S397000, C370S400000
Reexamination Certificate
active
06269098
ABSTRACT:
TECHNICAL FIELD
The present invention relates to network communications and more particularly, to scaling the number of virtual local area networks (VLANs) in 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 data 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 network switch includes switching logic for receiving and forwarding frames to the appropriate destinations. One arrangement for generating frame forwarding decisions uses a direct addressing scheme, where the network switch accesses a fixed address table storing switching logic to generate a frame forwarding decision. However, these direct addressing arrangements may not support data transmissions from stations utilizing virtual local area network (VLAN) tagging as well as transmissions from stations that do not utilize VLAN tagging.
The use of VLANs facilitates the transmission of data to multiple stations by creating workgroups of users who may be physically separated from each other. As the number of stations in the network increases, the number of VLANs normally increases. In many prior art systems, increasing the number of VLANs requires extensive changes to the hardware/software of the network switch.
SUMMARY OF THE INVENTION
There exists a need for a switching device that supports virtual local area networks (VLANs) and can be modified to change the number of VLANs supported.
There is also a need for a switching device that may be easily customizable to support any number of VLANs with minimal changes to the architecture of the switch.
These and other needs are met by the present invention, where data received by the network switch includes a VLAN identifier. The data is routed to an internal decision making engine that includes an address table. The internal decision making engine generates a VLAN index from the VLAN identifier and searches the address table for data forwarding information.
According to one aspect of the invention, a multiport switch is configured for controlling the communication of data frames between stations. The switch includes a receive device for receiving data frames and an address table for storing source addresses, destination addresses and VLAN index information. The switch also includes a control device that receives information from a data frame, including a VLAN identifier, and searches the address table for data forwarding information.
Another aspect of the present invention provides a method for making data forwarding decisions. The method includes receiving information from a data frame. The received information includes a VLAN identifier. The method also includes searching an address table for data forwarding information that is based on the received information. The address table includes an address field for storing source addresses and destination addresses and a VLAN index field.
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“Virtual Lans Get Real Ethernet Switch Makers Are Taking The Lead in Deploying Virtual Lans Across Campus Networks”, Data Communications, vol. 24, No. 3, Mar. 1, 1995, pp. 87-92, 94, 96, 98, and 100, XP000496027.
Advanced Micro Devices , Inc.
Chin Wellington
Tran Maikhanh
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