Packet switching node

• US 20050063382A1
• Filed: 07/16/2004
• Published: 03/24/2005
• Est. Priority Date: 06/16/1989
• Status: Active Grant

• Current Assignee: Fenner Investments Limited
• Original Assignee: Fenner Investments Limited
• Inventors: Fenner, Peter R.
• Granted Patent: US 7,145,906 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• CPC Class Codes: H03M 7/4006 Conversion to or from arithmetic code
• CPC Class Codes: H04L 12/4625 Single bridge functionality, e.g. connection of two networks over a single bridge
• CPC Class Codes: H04L 2101/30 Types of network names
• CPC Class Codes: H04L 45/16 Multipoint routing
• CPC Class Codes: H04L 45/742 Route cache; Operation thereof
• CPC Class Codes: H04L 61/5038 for local use, e.g. in LAN or USB networks, or in a controller area network [CAN]
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04W 4/40 for vehicles, e.g. vehicle-to-pedestrians [V2P]
• CPC Class Codes: H04W 40/02 Communication route or path selection, e.g. power-based or shortest path routing
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99933 Query processing, i.e. searching

Abstract

To provide fast access times with very large key fields, an associative memory utilizes a location addressable memory and lookup table to generate from a key the address in memory storing an associated record. The lookup tables, stored in memory, are constructed with the aid of arithmetic data compression methods to create a near perfect hashing of the keys. For encoding into the lookup table, keys are divided into a string of symbols. Each valid and invalid symbol is assigned an index value, such that the sum of valid index values for symbols of a particular key is a unique value that is used as an address to the memory storing the record associated with that key, and the sum of keys containing invalid index values point to a location in memory containing similar data. Utilizing the lookup tables set and relational operations maybe carried out that provide a user with a maximum number of key records resulting from a sequence of intersection, union and mask operations.

Claims

1. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address;

circuitry for,

determining if a MAC source address of a received packet has been stored and associated with one of the at least three communications ports;

if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which the received packet is received, storing an association of the MAC source address with the one of the at least three communications ports at which the packet was received and causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

if the MAC source address of the received packet is associated by the node with the one of the at least three communications ports at which it is received, causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received.

2. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

circuitry for,

determining if a MAC source address of a received packet has been stored by the node and associated with one of the at least three communications ports at which the packet was received;

if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which it was most recently received, (i) storing an association of the MAC source address with the one of the at least three communications ports at which the packet was most recently received, (ii) causing the received packet to be forwarded on one of the at least three communications ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received, and (iii) storing in the node an indication that the MAC source address has been recently used;

if the MAC source address is associated with the one of the at least three communications ports at which it arrived, storing an indication that the MAC source address has been recently used, and causing the received packet to be forwarded on one of the at least three communications ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

disassociating MAC addresses from any of the at least three communications ports that have not been the MAC source address in any packet at the node within a preceding period of time.

3. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

circuitry for,

determining if a MAC source address of a received packet has been stored by the node and associated with one of the at least three communications ports at which the packet was received;

accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the packet according to the source filtering information;

if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which it was most recently received, storing an association of the MAC source address with the one of the at least three communications ports at which the packet was received, and causing the received packet to be forwarded on one of the at least three communications ports with which the received packet'"'"'s MAC destination address is associated, or, if the received packet'"'"'s MAC destination address is not associated with any of the at least three communications ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

if the MAC source address is associated with the one of the at least three communications ports at which it arrived, causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received.

4. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

circuitry for,

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address.

5. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

circuitry for,

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet;

if the destination MAC address associated by the node with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

if the destination MAC address associated by the node with the IP destination address does not have an association with one of the at least three-communications ports stored by the node, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets except for the one of the at least three communications ports on which the packet was received.

6. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

circuitry for,

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

.

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node.

7. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

circuitry for,

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address;

transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node; and

broadcasting an IP address resolution protocol packet on each of the at least three communications ports, the IP address resolution protocol packet containing the MAC address and IP address of the packet switching node, and receiving in response the MAC address and IP address of each device that is coupled at a MAC level with one of the at least three communications ports and that has been assigned an IP address.

8. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

circuitry for,

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet;

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

if the destination MAC address associated with the IP destination address of the received packet does not have a stored association with one of the at least three communications ports, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets except for the one of the at least three communications ports on which the packet was received;

transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node;

broadcasting an IP address resolution protocol packet on each of the at least three communications ports, the IP address resolution protocol packet containing the MAC address and IP address of the packet switching node, and receiving in response the MAC address and IP address of each device that is coupled at a MAC level with one of the at least three communications ports and that has been assigned an IP address.

9. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

circuitry for,

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the received packet according to the source filtering information;

if the received packet is to be forwarded, encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address.

10. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

circuitry for,

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the received packet according to the source filtering information;

if the received packet is to be forwarded, encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet;

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

if the node has no stored association between the destination MAC address associated with the IP destination address of the received packet and at one of the least three communications ports, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets according to the source filtering information associated with the source IP address, but not out the one of the at least three communications ports on which the packet was received.

11. A packet switching node comprising:

a least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

circuitry for,

if a first MAC address contained in a MAC source address field of a packet received on one of the at least three communications ports has a stored association with one of the three least communications ports at which it was received, and if source address filtering information is associated with the first MAC address contained in the received packet, filtering the received packet according to the source filtering information;

if the node has no stored association between the first MAC address and one of the at least three communications ports at which it is received, associating the first MAC address with the one of the at least three communications ports at which the packet was received and, if source address filtering information is associated with the first MAC address, filtering the received packet according to the source filtering information;

if a second MAC address contained in a MAC destination address field of the received packet has stored association with one of the least three communications ports, causing the packet to be forwarded out the one of the at least three communications with which the second MAC is associated if allowed by the source filtering information associated with the first MAC address; and

if the second MAC address contained in the received packet does not have a stored association with any one of the least three communications ports, forwarding the received packet from each one of the at least three communications ports except the one of the at least the communications ports at which the packet was received if allowed b the source filtering information associated with the first MAC address.

12. A packet switching node comprising:

a least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

circuitry for,

determining if a first MAC address contained in a MAC source address field of a packet received on one of the at least three communications ports does not have a stored association with one of the three least communications ports at which it was received, and associating the first MAC address with the one of the at least three communications ports at which the packet was received;

if a second MAC address contained in a MAC destination address field of the received packet has a stored association with one of the least three communications ports, causing the received packet to be forwarded on the one of the at least three communications ports with which the second MAC address is associated unless the one of the at least three communications ports, with which the second MAC address is associated, is associated with a stored protection record indicating protection of that communications port from packets containing the first MAC address as a MAC source address; and

if the second MAC address contained in the received packet does not have a stored association with any one of the least three communications ports, forwarding the received packet on each one of the at least three communications ports, except the one of the at least the communications ports at which the packet was received, that are allowed by the stored protection record to forward packets having been received with the first MAC as a MAC source address.

13. A method for switching packets at a node at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

determining if a MAC source address of a received packet has been stored and associated with one of the at least three communications ports;

if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which the received packet is received, storing an association of the MAC source address with the one of the at least three communications ports at which the packet was received and causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

if the MAC source address of the received packet is associated by the node with the one of the at least three communications ports at which it is received, causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received.

14. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

determining if a MAC source address of a received packet has been stored by the node and associated with one of the at least three communications ports at which the packet was received;

if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which it was most recently received, (i) storing an association of the MAC source address with the one of the at least three communications ports at which the packet was most recently received, (ii) causing the received packet to be forwarded on one of the at least three communications ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received, and (iii) storing in the node an indication that the MAC source address has been recently used;

if the MAC source address is associated with the one of the at least three communications ports at which it arrived, storing an indication that the MAC source address has been recently used, and causing the received packet to be forwarded on one of the at least three communications ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

disassociating MAC addresses from any of the at least three communications ports that have not been the MAC source address in any packet at the node within a preceding period of time.

15. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

circuitry for,

determining if a MAC source address of a received packet has been stored by the node and associated with one of the at least three communications ports at which the packet was received;

accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the packet according to the source filtering information;

if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which it was most recently received, storing an association of the MAC source address with the one of the at least three communications ports at which the packet was received, and causing the received packet to be forwarded on one of the at least three communications ports with which the received packet'"'"'s MAC destination address is associated, or, if the received packet'"'"'s MAC destination address is not associated with any of the at least three communications ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

if the MAC source address is associated with the one of the at least three communications ports at which it arrived, causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received.

16. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address.

17. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet;

if the destination MAC address associated by the node with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

if the destination MAC address associated by the node with the IP destination address does not have an association with one of the at least three-communications ports stored by the node, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets except for the one of the at least three communications ports on which the packet was received.

18. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node.

19. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address;

transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node; and

broadcasting an IP address resolution protocol packet on each of the at least three communications ports, the IP address resolution protocol packet containing the MAC address and IP address of the packet switching node, and receiving in response the MAC address and IP address of each device that is coupled at a MAC level with one of the at least three communications ports and that has been assigned an IP address.

20. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet;

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

if the destination MAC address associated with the IP destination address of the received packet does not have a stored association with one of the at least three communications ports, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets except for the one of the at least three communications ports on which the packet was received;

transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node;

broadcasting an IP address resolution protocol packet on each of the at least three communications ports, the IP address resolution protocol packet containing the MAC address and IP address of the packet switching node, and receiving in response the MAC address and IP address of each device that is coupled at a MAC level with one of the at least three communications ports and that has been assigned an IP address.

21. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the received packet according to the source filtering information;

if the received packet is to be forwarded, encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address.

22. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

removing the source and destination MAC addresses of a received packet;

accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the received packet according to the source filtering information;

if the received packet is to be forwarded, encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet;

if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

if the node has no stored association between the destination MAC address associated with the IP destination address of the received packet and at one of the least three communications ports, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets according to the source filtering information associated with the source IP address, but not out the one of the at least three communications ports on which the packet was received.

23. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

if a first MAC address contained in a MAC source address field of a packet received on one of the at least three communications ports has a stored association with one of the three least communications ports at which it was received, and if source address filtering information is associated with the first MAC address contained in the received packet, filtering the received packet according to the source filtering information;

if the node has no stored association between the first MAC address and one of the at least three communications ports at which it is received, associating the first MAC address with the one of the at least three communications ports at which the packet was received and, if source address filtering information is associated with the first MAC address, filtering the received packet according to the source filtering information;

if a second MAC address contained in a MAC destination address field of the received packet has stored association with one of the least three communications ports, causing the packet to be forwarded out the one of the at least three communications with which the second MAC is associated if allowed by the source filtering information associated with the first MAC address; and

if the second MAC address contained in the received packet does not have a stored association with any one of the least three communications ports, forwarding the received packet from each one of the at least three communications ports except the one of the at least the communications ports at which the packet was received if allowed b the source filtering information associated with the first MAC address.

24. A method for switching packets at a node having at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address, comprising:

determining if a first MAC address contained in a MAC source address field of a packet received on one of the at least three communications ports does not have a stored association with one of the three least communications ports at which it was received, and associating the first MAC address with the one of the at least three communications ports at which the packet was received;

if a second MAC address contained in a MAC destination address field of the received packet has a stored association with one of the least three communications ports, causing the received packet to be forwarded on the one of the at least three communications ports with which the second MAC address is associated unless the one of the at least three communications ports, with which the second MAC address is associated, is associated with a stored protection record indicating protection of that communications port from packets containing the first MAC address as a MAC source address; and

if the second MAC address contained in the received packet does not have a stored association with any one of the least three communications ports, forwarding the received packet on each one of the at least three communications ports, except the one of the at least the communications ports at which the packet was received, that are allowed by the stored protection record to forward packets having been received with the first MAC as a MAC source address.

25. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each communications port having an associated with it a MAC address;

means for determining if a MAC source address of a received packet has been stored and associated with one of the at least three communications ports;

if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which the received packet is received, means for storing an association of the MAC source address with the one of the at least three communications ports at which the packet was received and causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

if the MAC source address of the received packet is associated by the node with the one of the at least three communications ports at which it is received, means for causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, means causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received.

26. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

means for determining if a MAC source address of a received packet has been stored by the node and associated with one of the at least three communications ports at which the packet was received;

means for, if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which it was most recently received, (i) storing an association of the MAC source address with the one of the at least three communications ports at which the packet was most recently received, (ii) causing the received packet to be forwarded on one of the at least three communications ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received, and (iii) storing in the node an indication that the MAC source address has been recently used;

means for, if the MAC source address is associated with the one of the at least three communications ports at which it arrived, storing an indication that the MAC source address has been recently used, and causing the received packet to be forwarded on one of the at least three communications ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

means for disassociating MAC addresses from any of the at least three communications ports that have not been the MAC source address in any packet at the node within a preceding period of time.

27. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

means for determining if a MAC source address of a received packet has been stored by the node and associated with one of the at least three communications ports at which the packet was received;

means for accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the packet according to the source filtering information;

means for, if the MAC source address of the received packet is not stored by the node, or if the MAC source address of the received packet is not associated with the one of the at least three communications ports at which it was most recently received, storing an association of the MAC source address with the one of the at least three communications ports at which the packet was received, and causing the received packet to be forwarded on one of the at least three communications ports with which the received packet'"'"'s MAC destination address is associated, or, if the received packet'"'"'s MAC destination address is not associated with any of the at least three communications ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received; and

means for, if the MAC source address is associated with the one of the at least three communications ports at which it arrived, causing the received packet to be forwarded on one of the at least three ports with which the packet'"'"'s MAC destination address is associated or, if the MAC destination address is not associated with any of the at least three ports, causing the received packet to be forwarded on all of the at least three communications ports except the one of the at least three communications ports at which the packet was received.

28. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

means for storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

means for removing the source and destination MAC addresses of a received packet;

means for encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

means for, if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address.

29. The packet switching node of claim 28, further comprising means for, if the destination MAC address associated by the node with the IP destination address does not have an association with one of the at least three-communications ports stored by the node, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets except for the one of the at least three communications ports on which the packet was received.

30. The packet switching node of claim 28, further comprising means for transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node.

31. The packet switching node of claim 30, further comprising means for broadcasting an IP address resolution protocol packet on each of the at least three communications ports, the IP address resolution protocol packet containing the MAC address and IP address of the packet switching node, and receiving in response the MAC address and IP address of each device that is coupled at a MAC level with one of the at least three communications ports and that has been assigned an IP address.

32. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

means for storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received,

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet,

means for removing the source and destination MAC addresses of a received packet;

means for encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet;

means for, if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address; and

means for, if the destination MAC address associated with the IP destination address of the received packet does not have a stored association with one of the at least three communications ports, sending the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets except for the one of the at least three communications ports on which the packet was received; and

means for transmitting IP routing protocol packets to other packet switching nodes, and receiving IP routing protocol packets from other packet switching nodes, on one or more of the at least three communications ports in order to identify IP addresses that may be reached from each of the at least three communications ports of the packet switching node;

means for broadcasting an IP address resolution protocol packet on each of the at least three communications ports, the IP address resolution protocol packet containing the MAC address and IP address of the packet switching node, and receiving in response the MAC address and IP address of each device that is coupled at a MAC level with one of the at least three communications ports and that has been assigned an IP address.

33. A packet switching node comprising:

at least three IEEE 802 media access controller (MAC) communications ports, each of the at least three communications ports having a MAC address;

means for storing an association between a MAC source address of a received packet and one of the at least three communications ports at which the packet was received by the node if there is no association between the MAC source address and the one of the at least three communications ports at which the packet is received; and

if the received packet contains a destination MAC address that is a MAC address associated with the node, and if the packet encapsulates an Internet Protocol (IP) packet;

means for removing the source and destination MAC addresses of a received packet;

means for accessing stored source filtering information associated with a source Internet Protocol (IP) address contained in the received packet and filtering the received packet according to the source filtering information;

means for, if the received packet is to be forwarded, encapsulating the IP packet as a MAC packet with a destination MAC address associated by the node with an IP destination address contained in the IP packet; and

means for, if the destination MAC address associated with the IP destination address has an association stored by the node with one of the at least three communications ports, sending the encapsulated IP packet out the one of the at least three communications ports associated with the destination MAC address.

34. The packet switching node of claim 33, further comprising means for sending, if the node has no stored association between the destination MAC address associated with the IP destination address of the received packet and at one of the least three communications ports, the encapsulated IP packet out all of the at least three communications ports that are allowed to forward MAC packets according to the source filtering information associated with the source IP address, but not out the one of the at least three communications ports on which the packet was received.

35. A packet switching node comprising:

a least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

means for, if a first MAC address contained in a MAC source address field of a packet received on one of the at least three communications ports has a stored association with one of the three least communications ports at which it was received, and if source address filtering information is associated with the first MAC address contained in the received packet, filtering the received packet according to the source filtering information;

means for, if the node has no stored association between the first MAC address and one of the at least three communications ports at which it is received, associating the first MAC address with the one of the at least three communications ports at which the packet was received and, if source address filtering information is associated with the first MAC address, filtering the received packet according to the source filtering information;

means for, if a second MAC address contained in a MAC destination address field of the received packet has stored association with one of the least three communications ports, causing the packet to be forwarded out the one of the at least three communications with which the second MAC is associated if allowed by the source filtering information associated with the first MAC address; and

means for, if the second MAC address contained in the received packet does not have a stored association with any one of the least three communications ports, forwarding the received packet from each one of the at least three communications ports except the one of the at least the communications ports at which the packet was received if allowed b the source filtering information associated with the first MAC address.

36. A packet switching node comprising:

a least three IEEE 802 media access controller (MAC) communications ports, each communications port having associated with it a MAC address;

means for determining if a first MAC address contained in a MAC source address field of a packet received on one of the at least three communications ports does not have a stored association with one of the three least communications ports at which it was received, and associating the first MAC address with the one of the at least three communications ports at which the packet was received;

means for, if a second MAC address contained in a MAC destination address field of the received packet has a stored association with one of the least three communications ports, causing the received packet to be forwarded on the one of the at least three communications ports with which the second MAC address is associated unless the one of the at least three communications ports, with which the second MAC address is associated, is associated with a stored protection record indicating protection of that communications port from packets containing the first MAC address as a MAC source address; and

means for, if the second MAC address contained in the received packet does not have a stored association with any one of the least three communications ports, forwarding the received packet on each one of the at least three communications ports, except the one of the at least the communications ports at which the packet was received, that are allowed by the stored protection record to forward packets having been received with the first MAC as a MAC source address.