Integrated data table in a network

• US 6,661,787 B1
• Filed: 04/06/1999
• Issued: 12/09/2003
• Est. Priority Date: 05/21/1998
• Status: Expired due to Term

• Current Assignee: 3COM Technologies
• Original Assignee: 3COM Technologies
• Inventors: OʼConnell, Anne G., Quinlan, Una, OʼNeill, Eugene
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): TRAN, THIEN D
• Application Number:
  US09/286,470
• Time in Patent Office: 1,708 Days
• Field of Search: 370/389, 370/390, 370/392, 370/397, 370/398, 370/399, 370/401, 370/402, 370/409, 370/425, 370/426, 370/428, 709/238
• US Class Current: 370/389
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: H04L 12/4641 Virtual LANs, VLANs, e.g. virtual private networks [VPN] LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272
• CPC Class Codes: H04L 45/742 Route cache; Operation thereof

Abstract

A method of operating a network device in a communication system for the transmission of data packets which include network addresses identifying sources and destinations of data, the network device being capable of both bridging and routing decisions and including a forwarding database by means of which a packet including network address data can be forwarded to at least one port and thereby to at least one network path identified by a network address, and packets can be forwarded to at least one port in response to a media access control address. The method comprises establishing a data table which contains entries comprising a network address of an end station to which a packet is destined, a respective media access control address and an identification of at least one port to which the packet will be directed within the device. The table is accessed in response to network addresses and media access control addresses, whereby the same table can be used for both routing and bridging decisions.

Claims

1. A method of operating a network device in a communication system for the transmission of data packets which include network addresses identifying sources and destinations of data, the network device being capable of both bridging and routing decisions and including a forwarding database by means of which a packet including network address data can be forwarded to at least one port and thereby to at least one network path identified by a network address, and packets can be forwarded to at least one port in response to a media access control address, the method comprising:

establishing a data table which contains entries each comprising a destination network address of an end station to which a packet is destined, a respective media access control address and an identification of at least one port to which the packet will be directed within the device;

determining whether to access said data table to retrieve said identification on the basis of a destination media access control address in a received packet or on the basis of a destination network address in said packet; and

accessing said data table in response to either said destination network address or said destination media access control address in dependence on the determination whether to access said data table to retrieve said identification on the basis of the destination media access control address or the destination network address, whereby the same table can be used for both routing and bridging decisions.

2. A method according to claim 1 wherein determining whether to access said data table to retrieve said identification on the basis of the destination media access control address or the destination network address comprises:

determining whether said destination media access control address is within a specified range;

and said accessing said data table in response to either said destination network address or said destination media control address comprises performing a look-up in said data table to retrieve said identification on the basis of said destination media access control address in said received packet when said destination media access control address falls within said range; and

performing a look up in said data table on the basis of said destination network address of said packet when said destination media access control address is outside said range.

4. A method according to claim 1 wherein the accessing step comprises a hashing step to convert address data to a pointer to an address in said data table.

3. A method of operating a network device in a communication system for the transmission of data packets which include network addresses identifying sources and destinations of data, the network device being capable of both bridging and routing decisions and including a forwarding database by means of which a packet including network address data can be forwarded to at least one port and thereby to at least one network path identified by a network address, and packets can be forwarded to at least one port in response to a media access control address, the method comprising:

establishing a data table which contains entries each comprising a destination network address of an end station to which a packet is destined, a respective media access control address and an identification of at least one port to which the packet will be directed within the device;

determining whether to access said data table to retrieve said identification on the basis of a destination media access control address in a received packet or on the basis of a destination network address in said packet; and

accessing said data table in response to either said destination network address or said destination media access control address in dependence on the determination whether to access said data table to retrieve said identification on the basis of the destination media access control address or the destination network address, whereby the same table can be used for both routing and bridging decisions;

wherein determining whether to access said data table to retrieve said identification on the basis of the destination media access control address or the destination network address comprises;

determining whether said destination media access control address is within a specified range;

said accessing said data table in response to either said destination network address or said destination media control address comprises performing a look-up in said data table to retrieve said identification on the basis of said destination media access control address in said received packet when said destination media access control address falls within said range; and

performing a lookup in said data table on the basis of said destination network address of said packet when said destination media access control address is outside said range; and

each entry in said data table includes a VLAN number and wherein the look-up in said data table on the basis of said destination media access control comprises accessing the table in response to both the said destination media access control address and a VLAN number.

5. A network device for use in a communication system for the transmission of data packets which include network addresses and/or media access control addresses, the network device being capable of bridging decisions in response to media access control addresses and routing decisions in response to network addresses, said device including a multiplicity of ports for receiving and forwarding data packets and a data table for entries each comprising destination address data and an identification of a port, whereby an incoming packet can be examined for its destination address data and be forwarded from the device on the port associated with the respective destination address data,

wherein said data table is organised to contain entries each including a destination network address, a media access control address and port identification data;

and

said device includes;

means for making a decision whether to access said data table and to retrieve an identification of said port on the basis of either a destination network address or a destination media access control address in said incoming packet; and

means for accessing said data table in response to either said destination network address or said destination media access control address in accordance with said decision.

6. A device according to claim 5 wherein the means for accessing comprises two hash tables each containing entries each pointing to an address in said data table and further comprises means for hashing address data comprising a destination network address to access a first of the hash tables and means for hashing address data including a destination media access control address to access a second of the hash tables.

7. A network device for use in a communication system for the transmission of data packets which include network addresses and/or media access control addresses, the network device being capable of bridging decisions in response to media access control addresses and routing decisions in response to network addresses, said device including a multiplicity of ports for receiving and forwarding data packets and a data table for entries each comprising destination address data and an identification of a port, whereby an incoming packet can be examined for its destination address data and be forwarded from the device on the port associated with the respective destination address data,

wherein said data table is organised to contain entries each including a destination network address, a media access control address and port identification data;

and

said device includes;

means for making a decision whether to access said data table and to retrieve an identification of said port on the basis of either a destination network address or a destination media access control address in said incoming packet;

means for accessing said data table in response to either said destination network address or said destination media access control address in accordance with said decision;

wherein the means for accessing comprises two hash tables each containing entries each pointing to an address in said data table and further comprises means for hashing address data comprising a destination network address to access a first of the hash tables and means for hashing address data including a destination media access control address to access a second of the hash tables; and

each of the entries in the data table includes a VLAN number and the said means for hashing address data comprising a destination media access control address hashes address data including a VLAN number.

8. A method of operating a network device in a communication system for the transmission of data packets which include network addresses identifying sources and destinations of data, the network device being capable of both bridging and routing decisions and including a forwarding database by means of which a packet including network address data can be forwarded to at least one port and thereby to at least one network path identified by a network address, and packets can be forwarded to at least one port in response to a media access control address, the method comprising:

establishing a data table which contains entries each comprising a destination network address of an end station to which a packet is destined, a respective media access control address and an identification of at least one port to which the packet will be directed within the device;

determining in respect of a received packet whether said received packet can be bridged on the basis of a destination media access control address in said received packet;

consequent on a determination that said received packet can be bridged, matching said destination media access control address to a respective media access control address in one of said entries and thereby identifying said at least one port for the forwarding of the received packet; and

consequent on a determination that said received packet cannot be bridged on the basis of said media access control destination address in said received packet, matching a network destination address in said received packet with a network address in one of said entries and thereby identifying a port for the forwarding of said received packet,

whereby the same table is used for both routing and bridging decisions.

9. A network device for use in a communication system for the transmission of data packets which include network addresses and/or media access control addresses, the network device being capable of bridging decisions in response to media access control addresses and routing decisions in response to network addresses, said device including:

a multiplicity of ports for receiving and forwarding data packets; and

a data table for entries each comprising destination address data and an identification of a port, whereby an incoming packet can be examined for its destination address data and be forwarded from the device on the port associated with the respective destination address data,

wherein said data table is organised to contain entries each including a destination network address, a respective destination media access control address and port identification data; and

said device includes;

a look-up engine organized for;

(i) determining in respect of a received packet whether said received packet can be bridged on the basis of a media access control destination address in said received packet;

(ii) consequent on a determination that said received packet can be bridged, matching said destination media access control address to a respective media access control address in one of said entries and thereby identifying said at least one port for the forwarding of said received packet; and

(iii) consequent on a determination that said received packet cannot be bridged on the basis of said destination media access control address in said received packet, matching a destination network address in said received packet with a network address in one of said entries and thereby identifying a port for the forwarding of said received packet.