Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-11-21
2001-05-22
Nguyen, Chau (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
Reexamination Certificate
active
06236658
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to message routing across interconnected networks, and more specifically may apply to such routing for messages on the internet.
BACKGROUND
Interconnected computer networks, such as the internet, are coupled together by routers. Such a computer network router is typically connected to two or more distinct networks. For a message sent from one network to another, destination network, the router receives the message, in the form of data packets, from one of the networks to which the router is connected, searches a database of routing information for determining to which of the connected networks the data packet should next be sent, so that the data packet can reach the destination network. The database of routing information can be quite large in networks, such as the internet, composed of many different interconnected networks. Therefore, searching the database may be relatively slow, in comparison with other aspects of data packet transmission, and a need consequently exists to speed up the searching.
SUMMARY
It is an object of the present invention to increase the rate of throughput for a router, by reducing the time required for finding routing information.
According to the present invention, the foregoing and other objects are attained by receiving a data packet from a first network, in a router coupled to a number of networks, and routing the data packet to a second one of the networks. A first portion of the data packet includes a destination network address. The destination network address for the packet is asserted to a content addressable memory (“CAM”), which identifies, while the router is still receiving a portion-of the data packet, one of the networks coupled to the router and corresponding to the destination network.
In a further aspect, at least a portion of the data packet is stored, while the router is still receiving a portion of the data packet, in a buffer for sending to the identified one of the networks.
In yet another aspect, it will, of course, be understood that identifying such a network while the router is still receiving the data packet requires a very fast response by the CAM; and, therefore, the CAM can only identify such a network this quickly when the CAM already has the necessary routing information stored therein at the time the destination address is asserted to the CAM. (The necessary routing information consists of the destination network address of the data packet and the identity of the one of the networks coupled to the router and corresponding to the destination address of the data packet.) When the CAM does not have the necessary routing information stored therein at the time the destination network address of the data packet is input to the CAM, a processor searches a database to identify one of the networks coupled to the router and corresponding to the destination address of the data packet. In this later case, the data packet is not written to the buffer until after the router has received the entire data packet, since searching the database is relatively slow.
In a further aspect, the destination network address of the data packet and the corresponding identity of the one of the networks coupled to the router, which were found by searching the database, are stored in the CAM, so that the CAM will have this routing information for subsequent data packets. If necessary, because the CAM is full, an existing entry will be discarded from the CAM to make room for the new entry.
Additional objects, advantages, and novel features are set forth in the following description, or will be apparent to those skilled in the art or those practicing the invention. Other embodiments are within the spirit and scope of the invention. These objects and embodiments may be achieved by the combinations pointed out in the appended claims. The invention is intended to be limited only as defined in the claims.
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Essbaum Alexander Dankwart
Ogden Aubrey Deene
Cesari and McKenna LLP
Cisco Technology Inc.
Johnston A. Sidney
Nguyen Chau
Trinh D.
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