Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-09-11
2001-01-09
Vu, Huy D. (Department: 2739)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S351000, C370S389000, C370S392000
Reexamination Certificate
active
06172980
ABSTRACT:
BACKGROUND OF THE INVENTION
Machines, such as computers, switches and routers communicate to each other through established conventions known as protocols. These protocols define a set of procedural rules for information exchange over a communication medium, the rules governing the content, format, timing, sequencing, and error control of messages exchanged in a network.
Prior art network devices such as routers have supported the routing of data units of differing protocols through the identification of the applicable protocol and carrying out the necessary data unit processing in software. Such data unit processing includes reencapsulation of data units and providing the appropriate routing of the data unit through the network device.
Typical data unit transfer rates require present day switches and routers to process 4,000,000 data units per second. Software routing, as provided by routers of the prior art, are incapable of processing incoming data units at such rates without significant data loss or throttling of upstream network elements. Data loss necessitates time intensive and bandwidth consuming retransmission, while throttling requires complex flow control mechanisms and costly buffering capacity in the source network element, in the router, or both.
SUMMARY OF THE INVENTION
The present invention provides a network bridge/router for identifying received data units which may require routing, for identifying a protocol associated with the received data unit, for determining whether the received data unit is in fact to be bridged or routed, and for carrying out appropriate data unit transfer operations, all in hardware. Such hardware processing enables the presently disclosed network bridge/router to operate at the maximum rate at which data units are received, known as the wire speed.
Major elements of the presently disclosed network bridge/router which enable these functions include a Receive Header Processor (RHP), an Address Cache ASIC (ACA), a Receive Frame Processor (RFP), and a Transmit Header Processor (THP). The RHP analyzes the destination address of the received data unit, in hardware, for determining if routing or bridging is required. If routing is required, the RHP uses portions of the received data unit header as an index into associated data structures. These data structures provide a protocol ID as an index to the appropriate microcode handling routine, executed by the RHP, for the data unit. The handling routine causes the RHP to forward data unit identifying information, including source and destination addresses and protocol ID, from the received data unit to the ACA.
The ACA utilizes the received data unit information from the RHP in looking up entries in an Address Cache. The ACA then provides data to the RHP and RFP reflecting a new layer-
2
destination address, protocol ID, Address Cache lookup status, destination address masks, and other information. The RHP overwrites the layer-
2
destination address with the new address, and forwards the data unit to a Receive Segment Unit (RSEG) for storage in buffers.
The RFP takes the information from the ACA, address, VLAN, status and other information from the RHP, and data from other sources in creating code vectors which determine whether the received data unit is to be forwarded entirely by the network bridge/router hardware, or if the assistance of software run by a Frame Processor is necessary. If handled in hardware, information appropriate for further data unit processing is passed to the THP.
If the data unit is to be bridged the THP performs any necessary layer-
2
header translations. If the data unit is to be routed the THP performs further layer-
2
and layer-
3
header processing using a microcode routine indexed by the protocol ID for this data unit. A new layer-
2
source address is generated by the THP prior to reassembling the data unit and transmitting it from the network bridge/router.
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patent: 5917821 (1999-06-01), Gobuyan et al.
patent: 5920566 (1999-07-01), Hendel et al.
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patent: 5963556 (1999-10-01), Varghese et al.
patent: 6014380 (2000-01-01), Hendel et al.
Bailey Brian W.
Flanders John A.
Lamaire Thomas A.
Radogna Thomas V.
Ross Ryan T.
3Com Corporation
Trinh Dung
Vu Huy D.
Weingarten, Schurgin Gagnebin & Hayes LLP
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