Fibre channel arbitrated loop bufferless switch circuitry to increase bandwidth without significant increase in cost

• US 20080205421A1
• Filed: 04/30/2008
• Published: 08/28/2008
• Est. Priority Date: 11/19/1998
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Black, Alistair D., Chan, Kurt
• Granted Patent: US 8,798,091 B2
• Time in Patent Office: Days
• US Class Current: 370/401
• CPC Class Codes: H04J 3/245 in which the allocation protocols between more than two stations share the same transmission medium stations for satellite systems H04B7/185
• CPC Class Codes: H04L 49/101 using crossbar or matrix
• CPC Class Codes: H04L 49/357 Fibre channel switches

Abstract

A switch, switched architecture and process for transferring data through an FCAL switch is disclosed. The switch uses multiple switch control circuits each coupled to one FCAL network and all connected to a crossbar switch. The switch control circuits are coupled together by a protocol bus for coordination purposes. Local conversations can occur on each FCAL loop and crossing conversations through the switch can occur concurrently. The OPN primitive is used to establish the connection before any data is transferred thereby eliminating the need for buffer memory in the switch control circuits. The destination address of each OPN is used to address a lookup table in each switch control circuit to determine if the destination node is local. If not, the destination is looked up and a connection request made on the protocol bus. If the remote port is not busy, it sends a reply which causes both ports to establish a data path through the backplane crossbar switch.

Claims

1. A process for establishing one or more concurrent data transfers between different pairs of nodes comprising the steps:

for each desired data transfer, sending to a switch from a source node a request to start a loop tenancy with a destination node, said request being in the form of a Fibre Channel Arbitrated Loop (hereafter FCAL) primitive and including a tag which identifies the destination node with which data is to be exchanged;

receiving said request and tag in a switching circuit coupled to the FCAL upon which said source node is resident and using said tag to determine from a table of nodes resident on said FCAL upon which said source node is resident if said destination node is resident thereon;

if said destination node is not resident on said FCAL upon which said source node is resident, using a control channel on a multiplexed bus having data transfer channels and control channels to circulate said request and tag to other switching circuits coupled each of said other FCALs;

in each said other switching circuit, using said tag to determine from a table of nodes resident on said FCAL to which said switching circuit is coupled if said destination node is resident on a local FCAL coupled to said switching circuit to facilitate data transfers between the source node and the destination node.

2. The method of claim 1, further comprising:

generating in the switching circuit coupled to the FCAL upon which said destination node is resident a grant message identifying the FCAL upon which said destination node is present by inclusion of a identification code of the switching circuit coupled to the FCAL on which said destination node is present in said grant message.

3. The process of claim 2, wherein generating in the switching circuit comprises placing a grant message in a control channel timeslot known to all switching circuits.

4. The method of claim 2, further comprising:

assigning one or more data transfer channels of said multiplexed bus to carry data of said desired data transfer so as to establish a data transfer path between said switching circuit coupled to said FCAL upon which said source node is present and the switching circuit coupled to said FCAL upon which said destination node is present to carry the data and FCAL primitives of the desired FCAL protocol data transfer.

5. The process of claim 4, wherein the assigning of one or more data transfer channels comprises assigning said timeslot dedicated to carrying data to carry the data of the desired data transfer by locating an unused data timeslot and broadcasting the switching circuit identification code of the switching circuit coupled to the FCAL upon which said destination node is resident to all other switching circuits such that the switching circuit coupled to the FCAL upon which said source node is resident knows which timeslot to use to transfer further primitives and frame data to said switching circuit coupled to said FCAL upon which said destination node is resident.

6. The method of claim 4, further comprising:

using said switching circuits coupled to said FCALs upon which said source and destination nodes are resident to couple an RRDY FCAL protocol primitive from said destination node to said source node after said data transfer path across said multiplexed bus has been established to trigger and control the flow of data, and placing the data of said desired data transfer in one or more of said data transfer channels of said multiplexed bus to carry out said data transfer.

7. The process of claim 6, wherein the using of said switching circuits comprises receiving data frames from said source node, marking the beginning and ending of every frame with a delimiter, breaking each frame into timeslot sized pieces, and placing the pieces data of said desired data transfer into a timeslot for transfer to said switching circuit coupled to said FCAL upon which said destination node is resident.

8. The process of claim 1, wherein said multiplexed bus is a time division multiplexed bus wherein some timeslots are dedicated as control channels and other timeslots are dedicated to carrying data.

9. The process of claim 1, wherein the using of the control channel comprises placing said request and tag in a first one of said control channel timeslots known to all switching circuits.

10. A process for establishing one or more concurrent data transfers between different pairs of nodes comprising the steps:

for each desired data transfer, sending to a switch from a source node a request to start a loop tenancy with a destination node after arbitrating for and winning control of a FCAL upon which said source node is resident, said request being in the form of FCAL OPN primitive and including a tag which identifies the destination node with which data is to be exchanged;

receiving said request and tag in a switching circuit coupled to the FCAL upon which said source node is resident and using said tag to determine from a table of nodes resident on said FCAL upon which said source node is resident if said destination node is also resident thereon;

if said destination node is not resident on said FCAL upon which said source node is resident, using a control channel on a multiplexed bus having data transfer channels and control channels to broadcast a destination node location request and the destination address of the destination node identified in said OPN primitive, said request requesting other switching circuits coupled each of said other FCALs to search their tables to determine which of them is coupled to the FCAL to which the destination node is connected;

in each said other switching circuit, using said destination address as a search key to search a table of addresses of nodes resident on said FCAL to which said other switching circuit is coupled to facilitate data transfers between the source node and the destination node.

11. The process of claim 10, further comprising:

if said destination node is resident on a local FCAL coupled to said switching circuit and is available for a transaction, generating a grant message in the switching circuit coupled to the FCAL upon which said destination node is resident, said grant message identifying the FCAL upon which said destination node is present by inclusion of the identification code of the switching circuit coupled to the FCAL on which said destination node is present in said grant message.

12. The process of claim 11, further comprising:

establishing a data transfer path between said switching circuit coupled to said FCAL upon which said source node is present and the switching circuit coupled to said FCAL upon which said destination node is present to carry the data and FCAL primitives of the desired FCAL protocol data transfer.

13. The process of claim 12, further comprising:

using said switching circuits coupled to said FCALs upon which said source and destination nodes are resident and the established data path to couple an RRDY FCAL protocol primitive from said destination node to said source node after said data transfer path has been established to trigger and control the flow of data, and transferring data over said data transfer path between said source and destination nodes.

14. The process of claim 12, wherein the establishing of the data transfer path comprises receiving a grant message at said switching circuit coupled to said FCAL upon which said source node is resident and generating suitable steering signals to a crossbar switch which functions to selectively couple all switching circuits to each other under the influence of steering signals received from said switching circuits, said steering signals received from said switching circuit coupled to said FCAL upon which said source node is resident causing said crossbar switch to establish a data path connection between said switching circuit coupled to said FCAL upon which said source node is resident and said switching circuit coupled to the FCAL on which the destination node is resident.

15. A switch for selectively, concurrently coupling the nodes on a plurality of a Fibre Channel Arbitrated Loops together comprising:

a multiplexed bus;

a plurality of switch control means, each for coupling to one local FCAL network, and each coupled to said multiplexed bus, each for receiving OPN primitives from a source node on the local FCAL network to which said control means is coupled and determining if the destination node identified in said OPN corresponds to said local FCAL network by searching a table of destination addresses for nodes on the local FCAL of said switch control means to determine if the destination node is located on the local FCAL to which said switch control means is coupled, and, if so, routing the OPN to the destination node via a local traffic data path in said switch control means and the local FCAL network, but if the destination node is not on said local FCAL, transmitting a destination node location request and the destination address of the destination node identified in said OPN primitive to all said other switch control means via a channel on said multiplexed bus, and for scanning messages received back from said other switch control means to determine which switch control means and local FCAL network to which flow control primitives and data are to be transferred to accomplish the desired data transfer.

16. The switch of claim 15, wherein each of the plurality of switch control means is for, when a grant message is received from another switch control means, indicating said other switch control means is the place to send flow control primitives and data and indicating that the FCAL to which said other switch control means is coupled is available for a loop tenancy.

17. The switch of claim 16, wherein each of the plurality of switch control means is for cooperating with said other switch control means to establish a data transfer path across said multiplexed bus.

18. The switch of claim 17, wherein each of the plurality of switch control means is for using said data transfer path to transfer flow control primitives between said source and destination nodes.

19. The switch of claim 18, wherein, each of the plurality of switch control means is for, upon determining that the destination node corresponds to the local FCAL of the switch control means, arbitrating for control of said local FCAL and, when control is won, sending a grant message back to said switch control means which initiated destination node location request identifying the switch control means coupled to the local FCAL on which said destination node is resident and for sending one or more messages to said switch control means which initiated said destination node location request for purposes of controlling establishment of said data transfer path.