Explicit Congestion Notification in Mixed Fabric Networks

1. A system comprising: a transmitter; a receiver configured to receive, over a communications network, a protocol data unit of a first protocol, the protocol data unit of the first protocol including: (i) a first header portion containing a first string that indicates whether congestion has been detected in the communications network, the first header portion being used in a first explicit congestion notification standard to indicate congestion, and (ii) a payload including at least part of a first protocol data unit of a second protocol; and a processor coupled to the transmitter and the receiver, the processor being configured to: prepare a second string based on the first string such that the second string is identical to the first string or derived from the first string, insert the second string in a second header portion of a second protocol data unit of the second protocol, the second header portion not being used in the first explicit congestion notification standard to indicate congestion, and provide to the transmitter the second protocol data unit of the second protocol for transmission to a sender of the first protocol data unit of the second protocol; wherein the second header portion is used in a second explicit congestion notification standard to indicate congestion, the second explicit congestion notification standard being different from the first explicit congestion notification standard; and a network interface card configured to maintain separate transmission queues for each type of protocol data unit payload, and in response to receiving an indication of congestion of the communications network for protocol data units of the first protocol, changing a transmission rate of protocol data units from at least one of the queues corresponding to protocol data unit payloads of the second protocol, the network interface card configured to translate notifications of congestion from the first explicit congestion notification standard to the second explicit congestion notification standard.

2. The system of claim 1 , wherein the first protocol implements the first explicit congestion notification standard and the second protocol implements the second explicit congestion notification standard.

3. The system of claim 1 , further comprising a memory coupled to the processor, the memory storing processor-executable instructions for transferring content of the first header portion into the second header portion.

4. The system of claim 1 , wherein the second string is inserted only when the first string indicates that congestion has been detected in the communications network.

5. The system of claim 1 , wherein: the first protocol is the Internet Protocol (IP) and the first header portion is the Congestion Experienced (CE) codepoint; and the second protocol is an InfiniBand protocol and the second header portion includes at least one of the Backward Explicit Congestion Notification (BECN) and the Forward Explicit Congestion Notification (FECN) bits.

6. The system of claim 1 , wherein the first protocol is the Internet Protocol (IP) and the second protocol is an InfiniBand protocol.

7. A method comprising: receiving over a non-InfiniBand communications network a non-InfiniBand protocol data unit that comprises at least a part of a first InfiniBand protocol data unit, the non-InfiniBand protocol data unit including an indication of congestion of the non-InfiniBand communications network, the indication of congestion being a first string that is part of the non-InfiniBand protocol data unit; transferring, by a processor, the indication of congestion from the non-InfiniBand protocol data unit to a second InfiniBand protocol data unit, wherein transferring comprises inserting a copy of a first string, or a string derived from the first string, into the header of the second InfiniBand protocol data unit, wherein the first string is part of a header of the non-InfiniBand protocol data unit; transmitting the second InfiniBand protocol data unit to a sender of the first InfiniBand protocol data unit over the non-InfiniBand communications network; maintaining separate transmission queues for each type of payload of the protocol data units; in response to receiving the indication of congestion of the non-InfiniBand communications network for non-InfiniBand protocol data units, changing a transmission rate of protocol data units from at least one of the queues corresponding to payloads of an InfiniBand protocol; translating the first string from a first format to a second format to produce a translated string; and inserting the translated string into the second InfiniBand protocol data unit.

8. The method of claim 7 , wherein the non-InfiniBand communications network is an Internet Protocol network and the non-InfiniBand protocol data unit is an Internet Protocol (IP) protocol data unit.

9. The method of claim 8 , wherein the transferring of the indication of the congestion comprises copying a value of at least a part of the Congestion Experienced (CE) codepoint of the Internet Protocol (IP) protocol data unit into the Base Transport header of the second InfiniBand protocol data unit.

10. The method of claim 7 , wherein the transferring comprises inserting a copy of a string that is part of a header of the non-InfiniBand protocol data unit into the header of the second InfiniBand protocol data unit.

11. The method of claim 7 wherein the non-InfiniBand communications network is one of a transport-layer network and a data-link-layer network.

12. A method comprising: receiving an incoming non-InfiniBand protocol data unit that comprises a payload portion including at least a part of a first InfiniBand protocol data unit, the non-InfiniBand protocol data unit also including a first string that indicates whether congestion is detected in a non-InfiniBand communications network, the first string being part of a header of the non-InfiniBand protocol data unit; identifying an outgoing non-InfiniBand protocol data unit that comprises a payload portion including at least a part of a second InfiniBand protocol data unit; when the first string indicates that congestion has been detected, modifying, by a processor, the payload portion of the outgoing non-InfiniBand protocol data unit so as to insert a second string in a header portion of the second InfiniBand protocol data unit, the second string being based on the first string such that the second string is identical to the first string or derived from the first string; transmitting the outgoing non-InfiniBand protocol data unit; maintaining separate transmission queues for each type of payload of the protocol data units; in response to receiving an indication of congestion of the non-InfiniBand communications network for non-InfiniBand protocol data units, changing a transmission rate of protocol data units from at least one of the queues corresponding to payloads of an InfiniBand protocol; and translating the first string from a first format to a second format to produce a translated string; wherein the first string is one or more characters long.

13. The method of claim 12 , wherein the modifying is performed when the first string indicates that congestion has not been detected.

14. The method of claim 12 , wherein the first string is the same as the second string.

15. The method of claim 12 , wherein the non-InfiniBand communications network is one of a transport-layer network and a data-link-layer network.