Method and apparatus for updating and synchronizing forwarding tables in a distributed network switch
First Claim
1. A method for updating and synchronizing forwarding tables contained on cards interconnected by a switch fabric of a distributed network switch, the forwarding tables including an ingress forwarding table associated with an ingress card and an egress forwarding table associated with an egress card of the switch, the method comprising the steps of:
- switching a frame from the ingress card to the egress card, the switched frame containing a destination media access control (MAC) address and an ingress destination index (DI) representative of a location within the switch that is associated with the destination MAC address;
determining (i) whether a primary input (PI) indicator is asserted for an entry of the egress forwarding table associated with the destination MAC address and (ii) whether the ingress DI of the switched frame is different from an egress DI for the egress forwarding table entry;
generating a notification frame at the egress card for transfer to the ingress card, the notification frame including a source MAC address field and a source index field, the source index field having contents representative of a location within the switch associated with the source MAC address; and
updating the ingress forwarding table with the contents of the source MAC address and source index fields to thereby synchronize the ingress and egress forwarding tables.
1 Assignment
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Accused Products
Abstract
A mechanism and technique updates and synchronizes forwarding tables contained on line cards that are interconnected by a switch fabric of a distributed network switch. The network switch is preferably a L3 or L4 switch comprising a plurality of forwarding engines distributed among the line cards. Each forwarding engine has an associated forwarding table, which preferably includes a L2 portion and L3/L4 portions. The L2 portion of the table is used to execute forwarding decision operations for frames forwarded among ports of the line cards, whereas the L3/L4 portions of the table are used to execute shortcut and forwarding operations for frames routed among the ports. The mechanism comprises a media access control (MAC) notification (MN) frame for updating and synchronizing the location of a destination port stored in the L2 portions of the forwarding tables.
188 Citations
42 Claims
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1. A method for updating and synchronizing forwarding tables contained on cards interconnected by a switch fabric of a distributed network switch, the forwarding tables including an ingress forwarding table associated with an ingress card and an egress forwarding table associated with an egress card of the switch, the method comprising the steps of:
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switching a frame from the ingress card to the egress card, the switched frame containing a destination media access control (MAC) address and an ingress destination index (DI) representative of a location within the switch that is associated with the destination MAC address;
determining (i) whether a primary input (PI) indicator is asserted for an entry of the egress forwarding table associated with the destination MAC address and (ii) whether the ingress DI of the switched frame is different from an egress DI for the egress forwarding table entry;
generating a notification frame at the egress card for transfer to the ingress card, the notification frame including a source MAC address field and a source index field, the source index field having contents representative of a location within the switch associated with the source MAC address; and
updating the ingress forwarding table with the contents of the source MAC address and source index fields to thereby synchronize the ingress and egress forwarding tables. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 32, 33)
generating a negative MN frame at the egress card;
setting the contents of the source index field of the negative MN frame to a predetermined value representative of a flood operation; and
sending the negative MN frame to the ingress card.
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8. The method of claim 7 wherein the step of updating comprises the step of updating an entry associated with the destination MAC address in the ingress forwarding table with the predetermined value in the source index field of the negative MN frame.
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9. The method of claim 8 wherein the predetermined value is representative of a flood-to-virtual local area network (VLAN) operation.
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32. A computer readable media, comprising:
- said computer readable media containing instructions for execution in a processor for the practice of the method of claim 1 or claim 21.
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33. Electromagnetic signals propagating on a computer network, comprising:
- said electromagnetic signals carrying instructions for execution on a processor for the practice of the method of claim 1 or claim 21.
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10. Apparatus for updating and synchronizing forwarding tables contained on cards interconnected by a switch fabric of a distributed network switch, the forwarding tables including an ingress forwarding table associated with an ingress card and an egress forwarding table associated with an egress card of the switch, the apparatus comprising:
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a switch fabric for switching a frame from the ingress card to the egress card, the switched frame containing a destination media access control (MAC) address and an ingress destination index (DI) representative of a location within the switch that is associated with the destination MAC address in the switch;
means for determining (i) whether a primary input (PI) indicator is asserted for an entry of the egress forwarding table associated with the destination MAC address and (ii) whether the ingress DI of the switched frame is different from an egress DI for the egress forwarding table entry;
means for generating a notification frame at the egress card for transfer to the ingress card, the notification frame including a source MAC address field and a source index field, the source index field having contents representative of a location within the switch associated with the source MAC address; and
means for updating the ingress forwarding table with the contents of the source MAC address and source index fields to thereby synchronize the ingress and egress forwarding tables. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A computer readable medium containing executable program instructions for synchronizing forwarding tables contained on cards interconnected by a switch fabric of a distributed network switch, the forwarding tables including an ingress forwarding table associated with an ingress card and an egress forwarding table associated with an egress card of the switch, the executable program instructions comprising program instructions for:
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switching a frame from the ingress card to the egress card, the switched frame containing a destination media access control (MAC) address and an ingress destination index (DI) representative of a location within the switch that is associated with the destination MAC address;
determining (i) whether a primary input (PI) indicator is asserted for an entry of the egress forwarding table associated with the destination MAC address and (ii) whether the ingress DI of the switched frame is different from an egress DI for the egress forwarding table entry;
generating a notification frame at the egress card for transfer to the ingress card, the notification frame including a source MAC address field and a source index field, the source index field having contents representative of a location within the switch associated with the source MAC address; and
updating the ingress forwarding table with the contents of the source MAC address and source index fields to thereby synchronize the ingress and egress forwarding tables. - View Dependent Claims (18, 19, 20)
generating a negative MN frame at the egress card;
setting the contents of the source index field of the negative MN frame to a predetermined value representative of a flood operation; and
sending the negative MN frame to the ingress card.
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21. A method for updating and synchronizing forwarding tables contained on cards interconnected by a switch fabric of a distributed network switch, the method comprising the steps of:
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providing a forwarding table on each card;
receiving a frame at a first card, hereinafter an ingress card;
switching the frame from the ingress card to an egress card, the switched frame containing a media access control (MAC) address associated with a destination end station and an ingress destination index (DI) representative of a location within the switch that is associated with the destination MAC address, the ingress DI determined by the ingress card using its forwarding table;
determining whether the ingress DI of the switched frame is different from an egress DI, the egress DI determined by the egress card using its forwarding table;
generating, in response to a difference between the ingress DI and egress DI, a notification frame at the egress card for transfer to the ingress card; and
updating, responsive to the notification frame, the ingress forwarding table to match the egress forwarding table. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
generating a negative MN frame at the egress card;
setting the contents of the source index field of the negative MN frame to a predetermined value representative of a flood operation; and
sending the negative MN frame to the ingress card.
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30. The method of claim 29 further comprising:
- updating an entry associated with the destination MAC address in the ingress forwarding table with the predetermined value in the source index field of the negative MN frame.
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31. The method of claim 30 further comprising:
- making the predetermined value be representative of a flood-to-virtual local area network (VLAN) operation.
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34. A distributed network switch, comprising:
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an ingress card for receiving frames, the ingress card having an ingress forwarding table;
an egress card to send received frames, the egress card having an egress forwarding table; and
a forwarding engine for (i) switching the frame from the ingress card to an egress card, the switched frame containing a media access control (MAC) address associated with a destination end station and an ingress destination index (DI) representative of a location within the switch that is associated with the destination MAC address, the ingress DI determined by the ingress card using its forwarding table, (ii) determining whether the ingress DI of the switched frame is different from an egress DI, the egress DI determined by the egress card using its forwarding table, (iii) generating, in response to a difference between the ingress DI and egress DI, a notification frame at the egress card for transfer to the ingress card, and (iv) updating, responsive to the notification frame, the ingress forwarding table to match the egress forwarding table. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41)
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42. An apparatus for updating and synchronizing forwarding tables contained on cards interconnected by a switch fabric of a distributed network switch, comprising:
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means for providing a forwarding table on each card;
means for receiving a frame at a first card, hereinafter an ingress card;
means for switching the frame from the ingress card to an egress card, the switched frame containing a media access control (MAC) address associated with a destination end station and an ingress destination index (DI) representative of a location within the switch that is associated with the destination MAC address, the ingress DI determined by the ingress card using its forwarding table;
means for determining whether the ingress DI of the switched frame is different from an egress DI, the egress DI determined by the egress card using its forwarding table;
means for generating, in response to a difference between the ingress DI and egress DI, a notification frame at the egress card for transfer to the ingress card; and
means for updating, responsive to the notification frame, the ingress forwarding table to match the egress forwarding table.
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Specification