Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-07-01
2001-01-30
Olms, Douglas W. (Department: 2732)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S389000
Reexamination Certificate
active
06181699
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to data switches that route data frames to ports based on tagging information in the packets. In particular, the invention relates to circuits which assign default tags to data frames.
2. Description of the Related Art
Local area networks (LANs) of all types that are IEEE 802 compliant may be connected together with media access control (MAC) bridges, as specified in ISO/IEC 10038, as modified by supplement P802.1p. The IEEE 802.1Q standard defines the operation of virtual LAN (VLAN) bridges that permit the definition, operation, and administration of VLAN topologies within a bridged LAN infrastructure.
Within 802.1 Q, data frames are routed between ports of the VLAN according to VLAN tags. If a frame does not contain a VLAN tag, a default tag may be assigned to it based on the port on which the frame was received.
However, this assignment of the default tag fails to account for other information in the frame which may be used to more intelligently assign a default tag. A frame may contain information such as a source address, a destination address, and protocol information which provide more information than just the port at which the frame was received. There is a need for an apparatus and a method of assigning a default tag which accounts for this additional information.
In addition, IEEE 802.1Q does not enable the assignment of a priority level to untagged frames when assigning the default tag, nor enable an assigned priority level to be changed. There is a need for an apparatus and a method of assigning and changing priority levels.
Finally, it would be advantageous if the circuitry solving both these deficiencies included a number of common functional blocks. Such commonality would allow functions to be performed with the same circuitry, reducing the total number of circuits required.
SUMMARY OF THE INVENTION
The present invention addresses these and other problems of the prior art by providing a circuit for assigning VLAN tags based on data frame information in addition to the port on which the data frame was received. Common parts of the circuit may also be used to assign a priority level to untagged data frames or to change an assigned priority level.
According to one embodiment, an apparatus according to the present invention includes a circuit for assigning a VLAN tag to a data frame received at a port of a switch. The circuit includes a content addressable memory, a data frame memory, a search circuit, and a tagging circuit. The content addressable memory stores tagging information, the tagging information including lookup data and associated tag data. The data frame memory stores at least part of a data frame, the part including data frame information. The search circuit is connected to the content addressable memory and the data frame memory. The search circuit reads the data frame information, searches the content addressable memory for the lookup data corresponding to the data frame information, and reads a corresponding subset of the associated tag data. The tagging circuit is connected to the search circuit and the data frame memory. The tagging circuit writes in the data frame memory a VLAN tag including the corresponding subset of the associated tag data.
According to another embodiment, a method according to the present invention assigns a VLAN tag to a data frame received at a port of a switch. The method includes the steps of storing tagging information (including lookup data and associated tag data), storing at least part of a data frame (including data frame information), reading the data frame information, searching the tagging information for the lookup data corresponding to the data frame information, reading a subset of the associated tag data according to a result of the step of searching, and writing in the part a VLAN tag including the subset of the associated tag data.
REFERENCES:
patent: 5852607 (1998-12-01), Chin
patent: 5930254 (2000-07-01), Liron et al.
patent: 5956335 (1999-09-01), Backes et al.
patent: 5959990 (1999-09-01), Frantz et al.
patent: 6016308 (2000-01-01), Crayford et al.
patent: 6018526 (2000-01-01), Liu et al.
The Virtual LAN Technology Report, May 1996.
“P802.1Q/D7” of Oct. 3, 1997, IEEE. (Please note specifically pp. 52-54, 73-80, Appendix C—pp. 156-182 and 183-186).
Crinion Patrick T.
Pagnon Vickie
Limbach & Limbach L.L.P.
National Semiconductor Corporation
Olms Douglas W.
Vanderpuye Ken
LandOfFree
Apparatus and method of assigning VLAN tags does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method of assigning VLAN tags, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method of assigning VLAN tags will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2513082