1. A method comprising: identifying a transaction from a first processor to a second processor with an identifier having a first value, the first value less than or equal to a maximum number of outstanding transactions between the first processor and the second processor; forwarding the transaction to the second processor with a header including the identifier, a source identifier corresponding to the first processor and a home node identifier corresponding to the second processor; and identifying a second transaction from the first processor to a third processor with an identifier having the same first value, and forwarding the second transaction to the third processor with a header including the identifier, the source identifier corresponding to the first processor and a home node identifier corresponding to the third processor.