Method and apparatus for communicating routing and attribute information for a transaction between hubs in a computer system

A system, comprising:

• a sending hub coupled to a data path;
• and
• a receiving hub coupled to the data path, the receiving hub including a data path input/output unit to receive a packet header for a transaction delivered by the sending hub, the packet header including
• a transaction descriptor routing field to identify an initiating agent that initiated the transaction, the transaction descriptor routing field including a hub identification portion and a pipe identification portion, the hub identification portion to identify an initiating hub that contains the initiating agent, the pipe identification portion to further identify the initiating agent within the initiating hub if the transaction has no ordering requirements with respect to a second agent in the initiating hub.

A method, comprising:

• outputting a packet header from a sending hub to a data path, wherein outputting the packet header includes
• outputting a transaction descriptor routing field to identify an initiating agent that initiated the transaction, the transaction descriptor routing field including a hub identification
• portion and a pipe identification portion, the hub identification portion to identify a hub that contains the initiating agent, the pipe identification portion to further identify the initiating agent within the identified hub if the transaction has no ordering requirements with respect to a second agent in the identified hub;
• and
• outputting a transaction descriptor attribute field.