Method and apparatus for virtual switching

A physical switching device for use in a communication network to switch Open Systems Interconnection (OSI) network layer protocol data units within the communication network on a shared communication medium, the physical switching device comprising:

• (a) at least a first and a second virtual switch, each virtual switch comprising decision means for determining an associated directive based on a destination identifier within a particular protocol data unit received at a data port, each virtual switch further comprising processing means for inserting the particular protocol data unit into an outgoing data stream on another data port according to the associated directive to enable delivery of the protocol data unit to the destination identifier, both data ports being associated with a set of data interfaces selected from a plurality of data interfaces in a physical communication network switch, the set of data interfaces being assigned exclusively to a unique virtual switch;
• (b) virtual link management means, operatively coupled to at least the first and the second virtual switches, for maintaining information on at least one virtual link between at least the first and the second virtual switch, each virtual link comprising a first end and a second end of a data path on the shared communication medium, each virtual link end comprising a data port from the plurality of data interfaces in the physical communication network switch.

A communication system which delivers Open Systems Interconnection (OSI) network layer protocol data units within a first and a second virtual closed user group on a shared communication medium, the communication system comprising:

• (a) first virtual closed user group processing means for examining and modifying data bits within a protocol data unit received from a member of the first virtual closed user group on the shared communication medium, each member of the first virtual closed user group having a unique destination identifier, the first virtual closed user group processing means comprising delivery means for delivering the modified protocol data unit to another member of the first virtual closed user group;
• (b) second virtual closed user group processing means for examining and modifying data bits within a protocol data unit received from a member of the second virtual closed user group on the shared communication medium, each member of the second virtual closed user group having a unique destination identifier, the second virtual closed user group processing means comprising delivery means for delivering the modified protocol data unit to another member of the second virtual closed user group;
• and
• (c) a framer means, operatively coupled to the first and the second virtual closed user group processing means, for maintaining a database of all destination identifiers representing users in that user group currently reachable for delivery of protocol data units within the communication system, the framer means comprising means for requiring verification that each destination identifier in a protocol data unit indicates a user in that user group can be currently reached for delivery through a lookup in the database prior to completing delivery of the protocol data unit to the user indicated by the associated destination identifier, the framer means further comprising means for limiting access to the database such that each virtual closed user group only has access to specific destination identifiers owned by that particular virtual closed user group so that a protocol data unit having a destination identifier which is not owned by the particular virtual closed user group will not be delivered.

A method for delivering Open Systems Interconnection (OSI) network layer protocol data units within a first and a second virtual closed user group on a shared communication medium in a communication system, the method comprising the device-implemented steps of:

• (a) examining and modifying data bits within a protocol data unit received from a member of the first virtual closed user group on the shared communication medium, each member of the first virtual closed user group having a unique destination identifier;
• (b) examining and modifying data bits within a protocol data unit received from a member of the second virtual closed user group on the shared communication medium, each member of the second virtual closed user group having a unique destination identifier;
• (c) maintaining a database of all destination identifiers representing members which are currently reachable for delivery of protocol data units within the communication system;
• (d) limiting access to the database such that each virtual closed user group only has access to specific destination identifiers owned by that particular virtual closed user group;
• (e) requiring verification that each destination identifier in a protocol data unit indicates a member which is currently reachable for delivery through a lookup in the database prior to completing delivery of the protocol data unit to the member represented by the associated destination identifier;
• (f) delivering the first virtual closed user group modified protocol data unit to another member of the first virtual closed user group after verifying that the first virtual closed user group member destination identifier is currently reachable;
• and
• (g) delivering the second virtual closed user group modified protocol data unit to another member of the second virtual closed user group after verifying that the second virtual closed user group member destination identifier is currently reachable, step (f) and (g) being device-implemented such that a protocol data unit having a destination identifier which is not owned by the particular virtual closed user group will not be delivered.