Arrangement for rendering forwarding decisions for packets transferred among network switches
AssigneeCisco Systems, Inc.
InventorHon Wah Chin
Life of this patent
Estimating the term…
Abstract
An arrangement facilitates rendering of a forwarding decision for a packet transferred between high-speed switches of a network using a path identifier (PTID) encapsulated within the packet. The PTID is a tag associated with a destination address of the packet and comprises a value that uniquely identifies a corresponding entry of a forwarding table of the switch. Rather than requiring a full compare of the destination address with the contents of the forwarding table, the PTID is used as a direct index address into the table that identifies the corresponding entry in a fast and efficient manner.
Claims16
In a communications network, an arrangement comprising:
- A) a first switch that includes a first-switch port from which the first switch forwards packets, each of a plurality of said packets including a path-identifier field and link-level destination- and source-address fields;
- and
- B) a second switch comprising:
- i) a plurality of second-switch ports, including second-switch output ports and a second-switch input port coupled to the first-switch port;
- ii) a forwarding table into which the second switch places at each of a plurality of table locations therein a respective entry that associates a respective link-level address with a second-switch output port at which the second switch has received a packet that included a source-address field containing that link-level address, each table location being represented by a respective index address;
- and
- iii) means for fetching the table entry at the table location represented by the contents of the path-identifier field of each of said plurality of packets forwarded from said first-switch port and received at the second-switch input port and, if that entry associates a given second-switch port with the contents of that packet's destination-address field, forwarding that received packet from the given second-switch port.
A method for facilitating rendering of a forwarding decision for a packet transferred from a first switch to a destination station via a second switch of a network, which second switch includes second-switch output ports and a second-switch input port coupled to the first switch, the method comprising the steps of:
- configuring a forwarding table, associated with the second-switch input port, that includes at each of a plurality of table locations therein a respective table entry that associates a respective link-level address with a second-switch output port at which the second switch has received a packet that included a source-address field containing that link-level address, each table location being represented by a respective index address;
- sending a message from the second switch to the first switch notifying the first switch of the index address that represents the location at which a table entry associates the destination station's link-level address with one said second-switch output port;
- encapsulating the packet with that index address at the first switch prior to forwarding the packet to the second switch;
- and
- rendering the forwarding decision for the packet received at the second switch using that index address to locate the corresponding table entry.
Dependencies are inferred from the claim text.