Abstract:
A combination error detector to detect errors in an InfiniBand packet. The detector includes registers that stores fields of an InfiniBand packet as the packet is being received and comparison logic that, as the fields are stored in the registers, compares the fields with check values and when an error is detected sets a flag corresponding to the error. After the packet has been completely received and all checks have been complete, all of the error flags are prioritized in accordance with the InfiniBand Architecture Specification.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    InfiniBand™ is an emerging bus technology that hopes to replace the current PCI bus standard, which only supports up to 133 Mbps (Megabits per second) transfers, with a broader standard that supports a maximum shared bandwidth of 566 Mbps. InfiniBand is the culmination of the combined efforts of about 80 members that are led by Intel, Compaq, Dell, Hewlett-Packard, IBM, Microsoft and Sun Systems who collectively call themselves the InfiniBand Trade Association. The InfiniBand Trade Association has published a specification entitled: Infiniband™ Architecture Specification Release 1.0. The Specification spans three volumes and is incorporated herein by reference.  
           [0002]    The InfiniBand Architecture (referred to herein as “IBA”) is a first order interconnect technology, independent of the host operating system (OS) and processor platform, for interconnecting processor nodes and I/O nodes to form a system area network. IBA is designed around a point-to-point, switched I/O fabric, whereby end node devices (which can range from very inexpensive I/O devices like single chip SCSI or Ethernet adapters to very complex host computers) are interconnected by cascaded switch devices. The physical properties of the IBA interconnect support two predominant environments:  
           [0003]    i. Module-to-module, as typified by computer systems that support I/O module add-in slots  
           [0004]    ii. Chassis-to-chassis, as typified by interconnecting computers, external storage systems, and external LAN/WAN access devices (such as switches, hubs, and routers) in a data-center environment.  
           [0005]    IBA supports implementations as simple as a single computer system, and can be expanded to include: replication of components for increased system reliability, cascaded switched fabric components, additional I/O units for scalable I/O capacity and performance, additional host node computing elements for scalable computing, or any combinations thereof. IBA is scalable to enable computer systems to keep up with the ever-increasing customer requirement for increased scalability, increased bandwidth, decreased CPU utilization, high availability, high isolation, and support for Internet technology. Being designed as a first order network, IBA focuses on moving data in and out of a node&#39;s memory and is optimized for separate control and memory interfaces. This permits hardware to be closely coupled or even integrated with the node&#39;s memory complex, removing any performance barriers.  
           [0006]    IBA uses reliable packet based communication where messages are enqueued for delivery between end nodes. IBA defines hardware transport protocols sufficient to support both reliable messaging (send/receive) and memory manipulation semantics (e.g. remote DMA) without software intervention in the data movement path. IBA defines protection and error detection mechanisms that permit IBA transactions to originate and terminate from either privileged kernel mode (to support legacy I/O and communication needs) or user space (to support emerging interprocess communication demands).  
           [0007]    IBA can support bandwidths that are anticipated to remain an order of magnitude greater than current I/O media (SCSI, Fiber Channel, and Ethernet). This enables IBA to act as a common interconnect for attaching I/O media using these technologies. To further ensure compatibility across varying technologies, IBA uses IPv6 headers, supporting extremely efficient junctions between IBA fabrics and traditional Internet and Intranet infrastructures.  
           [0008]    [0008]FIG. 1 is a block diagram of the InfiniBand architecture layers  100 . IBA operation can be described as a series of layers  100 . The protocol of each layer is independent of the other layers. Each layer is dependent on the service of the layer below it and provides service to the layer above it.  
           [0009]    The physical layer  102  specifies how bits are placed on a wire to form symbols and defines the symbols used for framing (i.e., start of packet &amp; end of packet), data symbols, and fill between packets (Idles). It specifies the signaling protocol as to what constitutes a validly formed packet (i.e., symbol encoding, proper alignment of framing symbols, no invalid or non-data symbols between start and end delimiters, no disparity errors, synchronization method, etc.).  
           [0010]    The link layer  104  describes the packet format and protocols for packet operation, e.g. flow control and how packets are routed within a subnet between the source and destination. There are two types of packets: link management packets and data packets.  
           [0011]    Link management packets are used to train and maintain link operation. These packets are created and consumed within the link layer  104  and are not subject to flow control. Link management packets are used to negotiate operational parameters between the ports at each end of the link such as bit rate, link width, etc. They are also used to convey flow control credits and maintain link integrity.  
           [0012]    Data packets convey IBA operations and can include a number of different headers. For example, the Local Route Header (LRH) is always present and it identifies the local source and local destination ports where switches will route the packet and also specifies the Service Level (SL) and Virtual Lane (VL) on which the packet travels. The VL is changed as the packet traverses the subnet but the other fields remain unchanged. The Global Route Header (GRH) is present in a packet that traverses multiple subnets. The GRH identifies the source and destination ports using a port&#39;s Global ID (GID) in the format of an IPv6 address.  
           [0013]    There are two CRCs in each packet. The Invariant CRC (ICRC) covers all fields which should not change as the packet traverses the fabric. The Variant CRC (VCRC) covers all of the fields of the packet. The combination of the two CRCs allow switches and routers to modify appropriate fields and still maintain an end to end data integrity for the transport control and data portion of the packet. The coverage of the ICRC is different depending on whether the packet is routed to another subnet (i.e. contains a global route header).  
           [0014]    The network layer  106  describes the protocol for routing a packet between subnets. Each subnet has a unique subnet ID, the Subnet Prefix. When combined with a Port GUID, this combination becomes a port&#39;s Global ID (GID). The source places the GID of the destination in the GRH and the LID of the router in the LRH. Each router forwards the packet through the next subnet to another router until the packet reaches the target subnet. Routers forward the packet based on the content of the GRH. As the packet traverses different subnets, the routers modify the content of the GRH and replace the LRH. The last router replaces the LRH using the LID of the destination. The source and destination GIDs do not change and are protected by the ICRC field. Routers recalculate the VCRC but not the ICRC. This preserves end to end transport integrity.  
           [0015]    While, the network layer  106  and the link layer  104  deliver a packet to the desired destination, the transport layer  108  is responsible for delivering the packet to the proper queue pair and instructing the queue pair how to process the packet&#39;s data. The transport layer  108  is responsible for segmenting an operation into multiple packets when the message&#39;s data payload is greater than the maximum transfer unit (MTU) of the path. The queue pair on the receiving end reassembles the data into the specified data buffer in its memory.  
           [0016]    IBA supports any number of upper layers  110  that provide protocols to be used by various user consumers. IBA also defines messages and protocols for certain management functions. These management protocols are separated into Subnet Management and Subnet Services.  
           [0017]    [0017]FIG. 2 is a block diagram of an InfiniBand subnet  200 . An IBA subnet  200  is composed of endnodes  202 , switches  204 , a subnet manager  206  and, possibly one or more router(s)  208 . Endnodes  202  may be any one of a processor node, an I/O node, and/or a router (such as the router  208 ). Switches  202  are the fundamental routing component for intra-subnet communication. The switches  202  interconnect endnodes  202  by relaying packets between the endnodes  202 . Routers  208  are the fundamental component for inter-subnet communication. Router  208  interconnects subnets by relaying packets between the subnets.  
           [0018]    Switches  204  are transparent to the endnodes  202 , meaning they are not directly addressed (except for management operations). Instead, packets transverse the switches  204  virtually unchanged. To this end, every destination within the subnet  200  is configured with one or more unique local identifiers (LID). From the point of view of a switch  204 , a LID represents a path through the switch. Packets contain a destination address that specifies the LID of the destination. Each switch  204  is configured with forwarding tables (not shown) that dictate the path a packet will take through the switch  204  based on a LID of the packet. Individual packets are forwarded within a switch  204  to an out-bound port or ports based on the packet&#39;s Destination LID and the Switch&#39;s  204  forwarding table. IBA switches support unicast forwarding (delivery of a single packet to a single location) and may support multicast forwarding (delivery of a single packet to multiple destinations).  
           [0019]    The subnet manager  206  configures the switches  204  by loading the forwarding tables into each switch  204 . To maximize availability, multiple paths between endnodes may be deployed within the switch fabric. If multiple paths are available between switches  204 , the subnet manager  206  can use these paths for redundancy or for destination LID based load sharing. Where multiple paths exists, the subnet manager  206  can re-route packets around failed links by re-loading the forwarding tables of switches in the affected area of the fabric.  
           [0020]    [0020]FIG. 3 is a block diagram of an InfiniBand Switch  300 . IBA switches, such as the switch  300 , simply pass packets along based on the destination address in the packet&#39;s LRH. IBA switches do not generate or consume packets (except for management packets). Referring to FIG. 1, IBA switches interconnect the link layers  104  by relaying packets between the link layers  104 .  
           [0021]    In operation the switch  300  exposes two or more ports  302   a ,  302   b  . . .  302   n , between which packets are relayed. Each port  302   n  communicates with a packet relay  304  via a set of virtual lanes  306   a  though  306   n . The packet relay  304  (sometimes referred to as a “hub or “crossbar”) redirects the packet to another port  302 , via that port&#39;s associated with virtual lanes  306 , for transmission based on the forwarding table associated with the packet relay  304 .  
           [0022]    During operation a 32-bit word arrives into an InfiniBand virtual link  306  at a port  302  of a switch  300  every clock cycle. To maximize bandwidth and minimize switch latency, it is desirable to be able to transfer data through the switch packet relay at the same frequency. In an 8 port switch, it is desirable to provide at least 3 output ports to the packet relay.  
           [0023]    As noted above, IBA uses packets as the main unit of communication. An IBA data packet conforms to the format shown in TABLE 1.  
                                                                                                                                                                                                                       TABLE 1                       Word/Bits   31-24   32-16   15-8   7-0   Notes                                 0   VL   LVER   SL   rsv   LNH   DLID   LRH             1   resv 5   PktLen (11 bits)   SLID   GRH             2   IPVers   Traffic Class   Flow Label                 3   Payload Length   Next Hdr   Hop Limit                 4   GRH Body           11            12   OpCode   S   r   Pa   TVER   PKey   BTH            13   resv (variant   Destination QP           14   resv 8   PSN            . . .        Other               Headers       n-1       EOP               PYLD       n   IRC       n + 1   VRC                  
 
           [0024]    As packets pass through the switch  300  they must be checked for errors, this process is typically termed error detection. To perform such error detection the Link Next Header (LNH) field of the packet must be decoded. The LNH field conforms to the format shown in Table 2.  
                                                 TABLE 2                       LNH   Packet Type   Transport   Next Header                                1   1   IBA Global   IBA   GRH       1   0   IBA Local   IBA   BTH       0   1   IP - Non-IBA   Raw   GRH       0   0   Raw   Raw   RWH (Ethertype)                  
 
           [0025]    The IBA specification discloses and recommends the use of a state machine to perform a multi-step packet error check. The checks are ordered with no consideration as to the order of the incoming packet data, but instead by their precedence. Fields VL, LVer, LNH, DLID, PktLen, IPVers, TVER, ICRC and VCRC are extracted, stored and analyzed by the state machine. This implies that a packet must be fully received, and hence stored, prior to performing error detection.  
           [0026]    [0026]FIG. 4 is a flow chart of the operation of a data packet check machine as described in the IBA specification. The data packet check machine resides in each port  302  and determines whether a data packet is valid and should be forwarded from the port  302  to the packet relay  304 . The method starts in step  400 . Subsequently, a series of checks  402  through  414  are made to validate the packet. The order of the states in FIG. 4 does not necessarily represent the chronological order of the checks, but does represent the priority of the error classes. According to the InfiniBand specification, only one error is logged per packet in step  418 . This state ordering determines which one, if any, is logged. If the packet satisfies all of the checks (e.g. states) the packet is forwarded to the packet relay  304  in step  416 .  
           [0027]    [0027]FIG. 5 is a flow chart of the operation of a link packet check machine as described in the IBA specification. The Link Packet Check Machine resides in each port and determines whether a link packet meets the rules of the InfiniBand specification, and thus whether or not the link packet should be interrogated for flow control or other information. The method starts in step  500 . Subsequently a series of checks  502  through  508  are made to validate the link header. The order of the states in FIG. 5 does not necessarily represent the chronological order of the checks, but does represent the priority of the error classes. According to the InfiniBand specification, only one error is logged per packet in step  512 . This state ordering determines which one, if any, is logged. If the packet satisfies all of the checks (e.g. states) the packet is forwarded to flow control circuitry (not shown) in step  416 .  
           [0028]    The Inventors of the present invention have recognized a need for methods and apparatus that enable error detection to be performed during reception of a packet, thereby eliminating the need to receive and store the entire packet prior to beginning such error detection. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    An understanding of the present invention can be gained from the following detailed description of the invention, taken in conjunction with the accompanying drawings of which:  
         [0030]    [0030]FIG. 1 is a block diagram of the InfiniBand architecture layers.  
         [0031]    [0031]FIG. 2 is a block diagram of an InfiniBand subnet.  
         [0032]    [0032]FIG. 3 is a block diagram of an InfiniBand switch.  
         [0033]    [0033]FIG. 4 is a flow chart of the operation of a data packet check machine as described in the IBA specification.  
         [0034]    [0034]FIG. 5 is a flow chart of the operation of a link packet check machine as described in the IBA specification.  
         [0035]    [0035]FIG. 6 is a block diagram of an InfiniBand switch in accordance with a preferred embodiment of the present invention.  
         [0036]    [0036]FIG. 7 is a block diagram of an InfiniBand switch in accordance with a preferred embodiment of the present invention.  
         [0037]    [0037]FIG. 8 is a block diagram of combinational error circuitry in an InfiniBand switch in accordance with a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0038]    Reference will now be made in detail to the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.  
         [0039]    In general, the present invention relates to apparatus and method steps embodied in software and associated hardware including computer readable medium, configured to store and/or process electrical or other physical signals to generate other desired signals. In general, the method steps require physical manipulation of data representing physical quantities. Usually, though not necessarily, such data takes the form of electrical or magnetic signals capable of being stored, transferred, combined, compared or otherwise manipulated. Those of ordinary skill in the art conveniently refer to these signals as “bits”, “values”, “elements”, “symbols”, “characters”, “images”, “terms”, “numbers”, or the like. It should be recognized that these and similar terms are to be associated with the appropriate physical quantities they represent and are merely convenient labels applied to such quantities.  
         [0040]    Accordingly, the detailed description which follows contains descriptions of methods presented in terms of methods that are described using symbolic representations of data transfixed in a computer readable medium such as RAM, ROM, CR-ROM, DVD, hard disk, floppy disk, data communication channels such as USB, SCSI, or FIREWIRE and/or a network such as IBA, the Internet, or a LAN. These descriptions and representations are the means used by those skilled in the art effectively convey the substance of their work to others skilled in the art.  
         [0041]    The term data processing device encompasses any of a variety of devices that are responsive to data and either perform some operation in response to the receipt thereof or modify the data in accordance with internal or external instructions that may be stored separately from the data processing devices or encoded into the structure of the data processing device. The term “method” is generally used to refer to a series of operations performed by a data processing device and, as such, encompasses such terms of art as “routine,” “software,” “program,” “objects,” “functions,” “subroutines,” and “procedures.” 
         [0042]    Unless otherwise noted, the methods recited herein may be enabled in one or more integrated circuits configured to perform the method steps taught herein. The required functional structures for such circuits appear in the description given below. Data processing devices that may be configured to perform the functions of the present invention include those manufactured by such companies as AGILENT and CISCO as well as other manufacturers of networking devices.  
         [0043]    [0043]FIG. 6 is a conceptual block diagram of a switch  600  in accordance with the preferred embodiment of the present invention. It will be appreciated by those of ordinary skill in the relevant arts that the switch  600 , as illustrated in FIG. 6, and the operation thereof as described hereinafter is intended to be generally representative of such systems and that any particular switch may differ significantly from that shown in FIG. 6, particularly in the details of construction and operation. As such, the switch  600  is to be regarded as illustrative and exemplary and not limiting as regards the invention described herein or the claims attached hereto.  
         [0044]    The switch  600  generally comprises a crossbar  602  (also referred to as a “hub”) to which a plurality of ports  602   a  through  602   h  are connected. Each port  602  of the switch  600  generally comprises a link block  606  and a physical block  608  (“PHY”). In perhaps the preferred embodiment the crossbar  602  is a ten port device with two ports being reserved for management functions. FIG. 6 only portrays eight ports  602   a  through  602   h  for clarity of presentation.  
         [0045]    The PHY block  608  primarily serves as a serialize to de-serialize (“SerDes”) device. The link block  406  performs several functions, including the input buffer, receive (“RX”), transmit (“TX”), and flow control. The input virtual lanes (VLs) are physically contained in input buffers (not shown) of the link block  606 . Other functions that may be performed by the link block  606  include: integrity checking, link state and status, error detecting and recording, flow control generation, and output buffering.  
         [0046]    The crossbar  602  is preferably implemented as a sparsely populated data path structure. In essence, the crossbar  602  acts as a distributed MUX for every possible input to each output port. The crossbar  602  is preferably combinatorial, and capable of completing the switching process for one 32-bit word within one 250 MHz system clock period (4.0 ns).  
         [0047]    [0047]FIG. 7 is a block diagram of an InfiniBand switch  700  in accordance with a preferred embodiment of the present invention. More specifically, FIG. 7 is a more detailed view of the switch  600  shown in FIG. 4 providing more detail of the link block  606 . It will be appreciated by those of ordinary skill in the relevant arts that the switch  700 , as illustrated in FIG. 7, and the operation thereof as described hereinafter is intended to be generally representative of such systems and that any particular switch may differ significantly from that shown in FIG. 7, particularly in the details of construction and operation. Further, only those functional elements that have bearing on the present invention have been portrayed so as to focus attention on the salient features of the inventive features. As such, the switch  700  is to be regarded as illustrative and exemplary and not limiting as regards the invention described herein or the claims attached hereto.  
         [0048]    The link block  606  generally comprises a phy-link interface  702  (the “PLI”) connected to a transmit link  704  (the “Tx Link”) and a receive link (the “Rx Link”)  706 . The Rx link  706  outputs to input buffer  708  for transfer of data to the crossbar  702 . A controller  710 , primarily comprising registers, controls the operation of the transmit and receive links  704  and  706 .  
         [0049]    The PLI  702  connects transmitter and receiver portions of the PHY block  604  to the link block  606 &#39;s Tx Link  704  and Rx Link  706 . The receive portion of the PLI  702  realigns the data from the PHY block  604  and detects special characters and strings of characters, such as a start of packet (SOP) indicator, from the received data stream.  
         [0050]    The Rx Link  706  accepts packet data from the PLI  702 , performs combinational error checking in accordance with the preferred embodiment of the present invention, and upon successful completion of the checks passes the data on to a the input buffer  708  for transfer to the crossbar  602 . The Tx Link  704  sends data packets that are ready to transfer from the Hub  602  to the PHY block  604 , through the PLI  702 . In doing so, the Tx Link  704  realigns the data, adds the placeholder for the start/end packet control characters, and calculates and inserts the VCRC field. In addition to data packets, the Tx Link  504  also accepts and transmits flow control link packets from a flow control state machine (not shown).  
         [0051]    [0051]FIG. 8 is a block diagram of combinational error circuitry  800  in an InfiniBand switch in accordance with a preferred embodiment of the present invention. FIG. 3 also serves to describe the data flow in the present invention thereby, illuminating a preferred method of the present invention. The combinational checks are initiated when a start of packet delimiter is received by the packet status logic  802 . Either a start of link packet or the start of a data packet will initiate combinational checks in accordance with a preferred embodiment of the present invention. The packet status logic  802  keeps track of the packet type, word count, and start/end delimiters.  
         [0052]    Once a start of packet delimiter is received, packet data will begin to arrive in the form of 32-bit words. Fields that are required for the combinational checks are stored in packet field registers  804 . In FIG. 8, several such registers are portrayed, e.g. VL (virtual lane: 0-7), LVER (link layer version), LNH (link next header—used for GRH VL 15 check), DLID (destination LIP), PktLen (packet length), Operand (a link packet check field), ICRC (cyclic redundancy check), VCRC, TVer (transport layer version), and IPVers (IP version). As noted above the fields that are required to be checked are well defined by the IBA Specification, however, the present invention facilitates additional checks not mandated by the IBA Specification, such as the TVER and IPVERs. The fields to be striped are preferably identified by simple bit/word counting.  
         [0053]    At the appropriate points in the data stream the comparison logic  806  performs a comparison between the values stored in the registers  804  and comparison values. The appropriate point to perform each comparison may be made based on, for example: the word count maintained by the packet status logic  802 ; the entry of data into the appropriate registers; or data sent by other blocks, such as an end of packet indication from the packet status logic  802 . Packet field selection logic  808  controls the read and write enables to and from the registers  804 , preferably based on packet word counts.  
         [0054]    The comparison values may be either IBA specified values or derived values. An example of a IBA specified value is LVER (link layer version). An example of a derived value is the packet length that is calculated by the packet status logic counting the length of the packet as it arrives. Certain values needed for the comparisons performed by the comparison logic  806  may be stored in registers  810 . In the example shown in FIG. 8, OpVl (Operational Virtual Lanes indicating the number of virtual lanes on the port), MTU (maximum transfer unit) and buffer space are shown. In general these values are supplied from functional blocks external to the combinational error circuitry  800 .  
         [0055]    When the comparison logic  806  determines the presence of an error state, an error flag is set in error flag logic  812 . The error flag logic  812  accumulates any and all error flags set by the comparison logic  806  until a n end of packet delimiter is received from the packet status logic  802 . It is to be noted that it may prove more efficient for the packet delimiters to be passed to the error flag logic indirectly, such as through the packet field selection logic  808 . Once an end of packet delimiter has been received and all checks have been performed, a full set of error flags is then sent to the error count/register block  814 . The error count/register block  814  prioritizes the error flags based on the IBA specification.  
         [0056]    The errors are also transmitted to the input buffer  708  (see FIG. 7). If the errors occur early in the packet transmission, while the entirety of the received packet is still in the input buffer  708 , the input buffer  708  can simply discard the packet. If the packet has an error but cannot be discarded, the packet is truncated (shortened) by the input buffer  708 , and marked as a bad packet.  
         [0057]    The present invention enables error checking to be performed without requiring storage of an entire packet. Further, the present invention performs error checking during packet reception. Finally, the present invention enables maintains error precedence as required by the IBA specification.  
         [0058]    Although an embodiment of the present invention has been shown and described, it will be appreciated by those skilled in the art that changes may be made in such embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.