Abstract:
Provided are a method, system, and program for identifying overrun conditions in data reception, for example. As a receive buffer approaches capacity, received data packets may be truncated to a smaller size. For example, header information may be saved but payload data discarded. The truncated packets may be used to facilitate sending acknowledgments to trigger resending of lost or dropped packets.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method, system, and program for overrun identification in data transmission. 
   2. Description of the Related Art 
   In a network environment, a network adapter on a host computer, such as an Ethernet controller, Fibre Channel controller, etc., will receive Input/Output (I/O) requests or responses to I/O requests initiated from the host. Often, the host computer operating system includes a device driver to communicate with the network adapter hardware to manage I/O requests to transmit over a network. Data packets received at the network adapter are often stored in an available allocated packet buffer in the host memory. The host computer may implement a protocol to process the packets received by the network adapter that are stored in the packet buffer, and access any I/O commands or data embedded in the packet. 
   For instance, the computer may implement the Transmission Control Protocol (TCP) and Internet Protocol (IP) to decode and extract the payload data in the TCP/IP packets received at the network adapter. IP specifies the format of packets, also called datagrams, and the addressing scheme. TCP is a higher level protocol which establishes a virtual connection between a destination and a source. Another protocol, Remote Direct Memory Access (RDMA) establishes a higher level connection and permits, among other operations, direct placement of data at a specified memory location at the destination. 
   A device driver, application or operating system can utilize significant host processor resources to handle network transmission requests to the network adapter. One technique to reduce the load on the host processor is the use of a TCP/IP Offload Engine (TOE) in which the TCP/IP protocol related operations are implemented in the network adapter hardware as opposed to the device driver or other host software, thereby saving the host processor from having to perform the TCP/IP protocol related operations. The transport protocol operations include packaging data in a TCP/IP packet with a checksum and other information, and unpacking a TCP/IP packet received from over the network to access the payload or data. 
   Another transport protocol operation performed by a TOE may include acknowledging the receipt of packets. Packets may be lost or dropped due to a number of factors including network congestion and overburdened resources of the receiver. If the packet sender does not receive an acknowledgment that a packet has been properly received, the packet sender can resend the packet. In the TCP/IP protocol, for example, if the packet sender does not receive an acknowledgment within a particular time period, it is assumed that the packet has been lost and the unacknowledged packet is resent. 
   Because waiting for the expiration of acknowledgment timers can slow the overall flow of data through a network, additional techniques are often used to detect missing packets and speed up the resending of those missing packets. For example, in the TCP/IP protocol as discussed in the RFC (Request for Comment) 2581—“TCP Congestion Control”, a Fast Retransmit procedure is described which takes advantage of the fact that in the TCP/IP protocol, packets in a message to be sent from a sender to a receiver over a network are typically sequentially ordered and each packet of the message is assigned a unique sequence number. 
   If the receiver receives a packet which is not expected, such as a packet that is out of sequential order, the sequence number of the last correctly received packet of that connection between the sender and receiver is reacknowledged by the receiver. This signals to the sender that either the packet order was changed or that a packet was lost. If the packets were all properly received but somewhat out of sequential order, the receiver can readily reorder the packets into correct sequential order. However, if the receiver acknowledges the same sequence number several times (typically 3 times), then the sender knows pursuant to the protocol that a simple reordering is unlikely and that the packet that followed the last acknowledged sequence number is likely lost. The sender can then resend the lost packet or packets. Various techniques may be used to resend the packets in an efficient manner such as the Fast Recovery algorithm as described in the above referenced 2581—“TCP Congestion Control”. 
   The multiple reacknowledgements of the sequence number of the last correctly received packet of the connection, in accordance with the Fast Retransmit algorithm, acts as a negative acknowledgement, indicating that the subsequent packet of the sequence was lost or dropped. One benefit of the Fast Retransmit algorithm is that the sender can often be informed of a missing packet without waiting for acknowledgement timers to expire. As a consequence, dead time on a connection can often be reduced. 
   Notwithstanding, there is a continued need in the art to improve the efficiency of data transmission. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
       FIG. 1  illustrates a computing environment in which aspects of the invention are implemented; 
       FIG. 2  illustrates a prior art packet architecture used with embodiments of the invention; 
       FIG. 3  illustrates operations performed to manage a receipt of data by a network adapter in accordance with embodiments of the invention; 
       FIG. 4  illustrates a buffer used by the network adapter in accordance with embodiments of the invention; 
       FIG. 5  illustrates thresholds used in operations performed to manage a receipt of data by the network adapter in accordance with embodiments of the invention; 
       FIG. 6  illustrates a portion of a buffer used by the network adapter in accordance with embodiments of the invention; and 
       FIG. 7  illustrates operations performed to manage processing of received data in accordance with embodiments of the invention.; and 
       FIG. 8  illustrates an architecture that may be used with the described embodiments. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following description, reference is made to the accompanying drawings which form a part hereof and which illustrate several embodiments of the present invention. It is understood that other embodiments may be utilized and structural and operational changes may be made without departing from the scope of the present invention. 
     FIG. 1  illustrates a computing environment in which aspects of the invention may be implemented. A computer  2  includes one or more central processing units (CPU)  4  (only one is shown), a volatile memory  6 , non-volatile storage  8 , an operating system  10 , and a network adapter  12 . An application program  14  further executes in memory  6  and is capable of transmitting and receiving packets from a remote computer. The computer  2  may comprise any computing device known in the art, such as a mainframe, server, personal computer, workstation, laptop, handheld computer, telephony device, network appliance, virtualization device, storage controller, network controller, etc. Any CPU  4  and operating system  10  known in the art may be used. Programs and data in memory  6  may be swapped into storage  8  as part of memory management operations. 
   The network adapter  12  includes a network protocol layer  16  to send and receive network packets to and from remote devices over a network  18 . The network  18  may comprise a Local Area Network (LAN), the Internet, a Wide Area Network (WAN), Storage Area Network (SAN), etc. The embodiments may be configured to transmit data over a wireless network or connection, such as wireless LAN, Bluetooth, etc. In certain embodiments, the network adapter  12  and various protocol layers may implement the Ethernet protocol including Ethernet protocol over unshielded twisted pair cable, token ring protocol, Fibre Channel protocol, Infiniband, Serial Advanced Technology Attachment (SATA), parallel SCSI, serial attached SCSI cable, etc., or any other network communication protocol known in the art. 
   A device driver  20  executes in memory  6  and includes network adapter  12  specific commands to communicate with the network adapter  12  and interface between the operating system  10 , applications  14  and the network adapter  12 . In certain implementations, a network controller of the network adapter  12  includes a packet buffer  21  and a transport offload engine  22  as well as the network protocol layer  16 . The network controller can control other protocol layers including a data link layer and a physical communication layer which includes hardware such as a data transceiver. In an embodiment employing the Ethernet protocol, the data transceiver could be an Ethernet transceiver. 
   In the illustrated embodiment, the network controller of the adapter  12  includes a transport protocol layer as well as a network protocol layer and other protocol layers. For example, the network controller of the adapter  12  implements a TCP/IP offload engine (TOE)  22 , in which transport layer and security operations are performed within the offload engine  22  implemented within the network adapter  12  hardware or firmware, as opposed to the device driver  20 . 
   The network layer  16  handles network communication and stores received TCP/IP packets in the packet buffer  21  prior to being processed by the transport offload engine  22 . The adapter  12  further includes a data link layer which includes two sublayers: the Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking. In the illustrated embodiment, the packet buffer  21  is located in the MAC portion of the network controller. It is appreciated that the buffer  21  may be located in other portions of the network adapter  12  as well as other portions of the computer  2 . 
   The transport offload engine  22  interfaces with the device driver  20 , or operating system  10  or application  14  and performs various transport protocol layer operations on the received packets. The operations include sending to the packet sender acknowledgments of the receipt of packets in accordance with the appropriate protocol. In addition, the engine  22  can process the content of messages included in the packets received at the network adapter  12  that are wrapped in a transport layer, such as TCP and/or IP, the Internet Small Computer System Interface (iSCSI), Fibre Channel SCSI, parallel SCSI transport, or any other transport layer protocol known in the art. The transport offload engine  22  can unpack the payload from the received TCP/IP packet and transfer the data to the device driver  20  to return to the driver  20 , operating system  10  or application  14 . 
   In certain implementations, the network controller and network adapter  12  can further include an RDMA protocol layer as well as the transport protocol layer. For example, the network adapter  12  can implement an RDMA offload engine, in which RDMA layer operations are performed within the offload engines of the RDMA protocol layer implemented within the network adapter  12  hardware, as opposed to the device driver  20 , operating system  10  or applications  14 . In various embodiments, the RMDA offload engines may be a part of the TOE  22  or a separate engine. 
   Thus, an application  14  transmitting messages over an RDMA connection can transmit the message through the device driver  20  and the RDMA protocol layer of the network adapter  12 . The data of the message can be sent to the transport protocol layer of the engine  22  to be packaged in a TCP/IP packet. The transport protocol layer can further encrypt the packet before transmitting it over the network  18  through the network protocol layer  16 . 
   The memory  6  further includes file objects  24 , which also may be referred to as socket objects, which include information on a connection to a remote computer over the network  18 . The application  14  uses the information in the file object  24  to identify the connection. The application  14  would use the file object  24  to communicate with a remote system. The file object  24  may indicate the local port or socket that will be used to communicate with a remote system, a local network (IP) address of the computer  2  in which the application  14  executes, how much data has been sent and received by the application  14 , and the remote port and network address, e.g., IP address, with which the application  14  communicates. Context information  26  comprises a data structure including information the device driver  20 , operating system  10  or application  14  maintains to manage requests sent to the network adapter  12  as described below. 
     FIG. 2  illustrates a format of a network packet  50  received at the network adapter  12 . The network packet  50  is implemented in a format understood by the network protocol  14 , such as the IP protocol. The network packet  150  may include an Ethernet frame that would include additional Ethernet components, such as a header and error checking code (not shown). 
   A transport packet  52  is included in the network packet  50 . The transport packet  52  is capable of being processed by the engine  22  in accordance with a transport protocol such as the TCP protocol. The packet  52  may be processed by other layers in accordance with other protocols including Internet Small Computer System Interface (iSCSI) protocol, Fibre Channel SCSI, parallel SCSI transport, etc. The transport packet  52  includes payload data  54  as well as other transport layer fields, such as a header and an error checking code. Included in the header of each packet is the packet sequence number. The payload data  52  includes the underlying content being transmitted, e.g., commands, status and/or data. The driver  20 , operating system  10  or an application  14  may include a layer, such as a SCSI driver or layer, to process the content of the payload data  54  and access any status, commands and/or data therein. 
   Packets may be lost during transmission from a sender to a receiver of a particular connection due to network congestion or equipment failure at one or more points in the network path from the sender to the receiver. Furthermore, packets may be dropped by the receiver should one or more resources of the receiver become over burdened such that all of the incoming packets cannot be properly processed. As previously mentioned, data retransmission algorithms such as the Fast Retransmit algorithm provide for the receiver to send a duplicate acknowledgment of the last properly received packet in sequence when an out of sequence or otherwise unexpected packet is received. This duplicate acknowledgment signals to the sender that the subsequent packet may have been lost or dropped and should be resent if a sufficient number of duplicate acknowledgments are received. 
   However, it is appreciated herein that circumstances may arise in which loss of packets does not trigger data retransmission algorithms such as the Fast Retransmit algorithm. As a consequence, the sender may be caused to await the expiration of an acknowledgment timer prior resending the lost packets. 
   More specifically, events may cause not just a single packet to be lost or dropped but whole strings of packets forming a message segment can often be lost at a time. For example, if a network controller is lacking a required resource such as bus bandwidth or a host buffer, all received packets are likely to be dropped. Moreover, if a sufficiently large number of packets are dropped, the data sender may be caused to withhold sending any additional packets to the receiver until the acknowledgment timer of the sender has expired. If the sender is inhibited from sending additional packets, the receiver can be inhibited from sending duplicate acknowledgments which trigger the fast retransmit algorithm. 
   For example, various protocols such as the TCP/IP protocol employ a variety of techniques in an attempt to reduce network congestion and provide for a more fair utilization of network resources. One such technique is to impose upon the data sender a “send window” such as the “TCP send window” which limits the amount of data which the sender can send without receiving an acknowledgment of the proper receipt of previously sent data. Thus, once the data sender has reached the limit imposed by a TCP send window, the sender may not permitted by the connection protocol to send additional data until it receives additional acknowledgments from the connection receiver. 
   If a data sender has reached such a limit, and the unacknowledged data previously sent by the data sender is lost or dropped, it is appreciated herein that the sender may not receive any further acknowledgments from the receiver because the sent packets were lost or dropped and the sender is inhibited from sending any additional packets to the receiver. Conversely, if the receiver does not receive any additional packets following the loss of the string of packets, the receiver will not be triggered, in accordance with the Fast Retransmit algorithm, to send any duplicate acknowledgments to signal the data sender that packets were dropped. Lacking the receipt of the duplicate acknowledgments from the receiver, the data sender may not be notified of the loss of the packets until the expiration of the acknowledgment timer. As a consequence, the purpose of the fast retransmit algorithm may not be achieved in such situations. 
     FIG. 3  shows operations of a network adapter such as the network adapter  12  which can explicitly identify to a data sender which packets have been dropped, even where relatively large numbers of packets are dropped at a time. In this embodiment, the network protocol layer  16  receives (block  100 ) a packet from the network  18  and determines (block  102 ) whether the buffer  21  is filled beyond a particular “fullness” threshold. The packet buffer  21  is schematically shown in  FIG. 4 . A bar graph depicting the degree to which the buffer  21  is filled at any one particular time is depicted in  FIG. 5  and is represented as a percentage of total capacity of the buffer  21  for storing packets received from the network  18 . A cross-hatched portion  104  of the bar graph represents that portion of the buffer  21  which has been filled with data packets received from the network  16 . Thus, the length of the portion  104  as indicated at  105  represents the stored data level of the buffer  21 . The remaining portion  106  of the bar graph represents the remaining capacity of the buffer  21  which has not yet been filled with data packets from the network. 
   The bar graph of  FIG. 5  also indicates at  108  a “fullness threshold.” In the example of  FIG. 5 , the buffer  21  has been filled to a level  105  below that of the fullness threshold  108 . As long as the filled level  105  remains below the fullness threshold  108 , the network adapter  12  will continue to store (block  110 ,  FIG. 3 ) the entire packet received from the network  18  into the buffer  21 .  FIG. 4  shows an example of a full packet  112  stored in the buffer  21 . 
   The fullness threshold  108  may be used to provide an early indication that the buffer  21  is likely to run out of room to store data packets from the network  18 . Once the buffer  21  runs out of storage space, any further received data packets are likely to be dropped. As long as the transport offload engine  22  can pull and process data packets from the buffer  21  at a rate which is the same or faster than the network protocol layer  16  stores data packets into the buffer  21 , the filled level  105  of the buffer  21  should remain below the fullness threshold  108 . However, if the network protocol layer  16  stores data packets into the buffer  21  at a rate faster than the transport offload engine  22  can process the data packets, the filled level  105  can begin to rise. 
   The rate at which the transport offload engine  22  processes data packets may be lower than the rate at which the network protocol layer  16  stores the data packets from the network  18  due to a number of factors. For example, the amount of data sent to the network adapter  12  from the network  18  may increase significantly. Also, resources needed by the transport offload engine  22  to process the data packets may become more scarce. For example, the bandwidth of the bus or busses available to connect the transport offload engine  22  to the rest of the host memory  6  or data storage  8  of the host computer  2  may narrow. 
   Once the filled level  105  exceeds (block  102 ) the fullness threshold  108 , the network adapter  12  rather than storing the received data packets in full, can, in accordance with one embodiment, begin to truncate the received data packets, mark the truncated packets as truncated, and store (block  114 ) the remaining, truncated portion into the buffer  21 . For example, in truncating the received data packets, the header information may be retained and the payload data discarded. As a consequence, the truncated data packet may be substantially reduced in size as compared to the full data packet as received. If a packet is received that does not have header information useful for generating acknowledgments, that packet could be discarded rather than truncated in this example. 
   Each additional packet received (block  116 ) from the network  18 , will be stored (block  114 ) in truncated form in the buffer  21  as long as it is determined (block  118 ) that the filled level  105  exceeds a “normal operation” threshold  120  ( FIG. 5 ). As explained in greater detail below, storing truncated data packets rather than full data packets when the fullness threshold  108  is exceeded can facilitate, for example, rapid retransmittal of dropped packets. 
     FIG. 4  indicates a portion  130  (an enlargement of which is shown in  FIG. 6 ) in which packet headers  132  are stored rather than full packets  112 . In this example, the buffer  21  is a 256K byte FIFO (first-in-first-out) buffer and the fullness threshold  108  may be set to indicate that the buffer  21  has 4 K bytes of FIFO space remaining. In some applications, two full size packets  112  can consume the remaining 4 K bytes of FIFO storage. In the illustrated embodiment, the amount of storage space consumed by a packet truncated down to the header information, for example, can be reduced substantially, such as to about 60 bytes, for example. Thus, in the remaining 4 K bytes of storage space, many more truncated packets, such as about 68 truncated packets for example, can be stored in the space which as few as two full packets may have otherwise occupied. As a consequence, these packets which would have otherwise likely been dropped entirely, can be stored in a truncated form to facilitate early retransmission as described below. 
   In the illustrated embodiment, the normal operation threshold  120  is set substantially below that of the fullness threshold  108 . It is appreciated that these thresholds may be set at a variety of levels, depending upon the application. Moreover, the fullness threshold  108  can be set equal to that of the normal operation threshold  120  to simply the logic operations. 
     FIG. 7  shows operations of a network adapter such as the network adapter  12  which could include a connection protocol layer including a transport offload engine  22 , in processing the data packets which were received by the network protocol layer  16  from the network  18  and stored in the buffer  21 . The adapter  12  obtains (block  150 ) a data packet from the buffer  21  and determines (block  152 ) whether the packet has been marked as truncated in a manner similar to that described above in connection with  FIG. 3 . If not, the network adapter  12  processes (block  154 ) the data packet in the usual fashion. 
   As previously mentioned, this normal processing may include decoding and extracting the payload data in the packets and sending an acknowledgement to the data sender in accordance with the appropriate protocol. For example, in the Fast Retransmit procedure, if the data packet being processed is the next packet in sequence for a particular connection, the sequence number of that packet is acknowledged back to the sender. However, if the receiver receives a packet which is not expected, such as a packet that is out of sequential order, the sequence number of the last correctly received packet of that connection between the sender and receiver is reacknowledged by the receiver. This signals to the sender that either the packet order was changed or that a packet was lost. 
   The data packets received by the network adapter  12  during any one interval may be from several different connections between the network adapter  12  and one or more senders in the network  18 . Hence, the data packets stored in the buffer  21  may each be a part of one or more different flows of packets between the network adapter  12  and one or more different senders. Hence, when acknowledging a received packet, the network adapter  12  determines to which flow of packets the received packet belongs and whether the sequence number of the received packet is the expected sequence number of that particular flow. If expected, the received packet is acknowledged. If unexpected, the last correctly received packet of that flow of packets between the sender and receiver is reacknowledged by the receiver. 
   If it is determined (block  152 ) that the data packet is truncated, an integrity test (block  156 ) may be performed on the truncated data packet. Such an integrity test may include for example, one or more of TCP, IP header checksums, and an Ethernet CRC (cyclic redundancy check). If the truncated data packet does not pass the integrity test, the truncated packet may be discarded (block  158 ). 
   If the truncated data packet does pass the integrity test (block  156 ), the network adapter can examine the header information of the truncated data packet to determine to which flow the received truncated data packet belongs and the sequence number of that received truncated data packet within the identified flow. Using this header information, the network adapter may send a duplicate acknowledgement (block  160 ) of the last correctly received full packet of that flow between the sender and the network adapter  12 . This process is continued with the network adapter obtaining (block  150 ) another packet from the buffer  21 , determining (block  152 ) whether the packet was truncated, testing (block  156 ) the truncated packet and sending a duplicate acknowledgement (block  160 ) of the last correctly received full packet of that connection between the sender and the network adapter  12 . 
   It is appreciated that by truncating the received data packets when it appears that the capacity of the receive buffer  21  may be shortly exceeded, the header information for a number of packets may be preserved which could otherwise be lost because there is insufficient room in the receiver buffer  21  to store full data packets. This header information may be used to generate reacknowledgments to trigger a fast retransmit procedure. Thus, these reacknowledgments may be useful in various circumstances such as for example, when the sender is inhibited from sending additional data packets because, for example, the sender&#39;s send window has been reached. As a result, the likelihood that a sufficient number of reacknowledgments can be generated to trigger a fast retransmit for a particular flow, can be improved. Moreover, by truncating the data packets to store primarily the packet header information, a relatively large number of truncated packets can be stored in a relatively small space. Hence, truncated packets may be successfully stored for a number of different data flows as indicated as flow 1 , flow 2  . . . etc in  FIG. 6 . Thus, the likelihood that a sufficient number of reacknowledgments can be generated to trigger a fast retransmit for more than one flow, can be improved as well. 
   Additional Embodiment Details 
   The described techniques for processing received data in a network adapter or network interface card may be implemented as a method, apparatus or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. The term “article of manufacture” as used herein refers to code or logic implemented in hardware logic (e.g., an integrated circuit chip, Programmable Gate Array (PGA), Application Specific Integrated Circuit (ASIC), etc.) or a computer readable medium, such as magnetic storage medium (e.g., hard disk drives, floppy disks, tape, etc.), optical storage (CD-ROMs, optical disks, etc.), volatile and non-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.). Code in the computer readable medium is accessed and executed by a processor. The code in which preferred embodiments are implemented may further be accessible through a transmission media or from a file server over a network. In such cases, the article of manufacture in which the code is implemented may comprise a transmission media, such as a network transmission line, wireless transmission media, signals propagating through space, radio waves, infrared signals, etc. Thus, the “article of manufacture” may comprise the medium in which the code is embodied. Additionally, the “article of manufacture” may comprise a combination of hardware and software components in which the code is embodied, processed, and executed. Of course, those skilled in the art will recognize that many modifications may be made to this configuration without departing from the scope of the present invention, and that the article of manufacture may comprise any information bearing medium known in the art. 
   In the described embodiments, the transport offload engine was described as performing various transport layer operations in accordance with the TCP/IP Protocol. In alternative embodiments, data may be transmitted from a remote host to the host using other protocols. As such, a communication protocol offload engine such as the transport offload engine  22  would perform some or all of those transmission operations including fragmented data reassembly or data payload extraction in accordance with such other transmission protocols. 
   In the described embodiments, certain operations were described as being performed by the device driver  20  and transport offload engine  22 . In alterative embodiments, operations described as performed by the device driver  20  may be performed by the transport offload engine  22 , and vice versa. In the described implementations, the transport protocol layer was implemented in the network adapter  12  hardware which includes logic circuitry separate from the central processing unit or units  4  of the host computer  2 . In alternative implementations, portions of the transport protocol layer may be implemented in the device driver or host memory  6 . 
   In the described embodiments, various protocol layers and operations of those protocol layers were described. The operations of each of the various protocol layers may be implemented in hardware, firmware, drivers, operating systems, applications or other software, in whole or in part, alone or in various combinations thereof. 
   In certain implementations, the device driver and network adapter embodiments may be included in a computer system including a storage controller, such as a SCSI, Integrated Drive Electronics (IDE), Redundant Array of Independent Disk (RAID), etc., controller, that manages access to a non-volatile storage device, such as a magnetic disk drive, tape media, optical disk, etc. Such computer systems often include a desktop, workstation, server, mainframe, laptop, handheld computer, etc. In alternative implementations, the network adapter embodiments may be included in a system that does not include a storage controller, such as certain hubs and switches. 
   In certain implementations, the network adapter may be configured to transmit data across a cable connected to a port on the network adapter. Alternatively, the network adapter embodiments may be configured to transmit data over a wireless network or connection, such as wireless LAN, Bluetooth, etc. 
   The illustrated logic of  FIGS. 3 and 7  shows certain events occurring in a certain order. In alternative embodiments, certain operations may be performed in a different order, modified or removed. Moreover, steps may be added to the above described logic and still conform to the described embodiments. Further, operations described herein may occur sequentially or certain operations may be processed in parallel. Yet further, operations may be performed by a single processing unit or by distributed processing units. 
   In certain implementations, the buffer  21  used by the network adapter  12  was described as being separate from the host memory  6  and being physically located in the adapter  12 . In other embodiments, the buffer  21  may be a part of the host memory  6  or a part of other controller circuits on a separate card or on a motherboard. 
     FIG. 8  illustrates one implementation of a computer architecture  300  of the network components, such as the hosts and storage devices shown in  FIG. 1 . The architecture  300  may include a processor  302  (e.g., a microprocessor), a memory  304  (e.g., a volatile memory device), and storage  306  (e.g., a non-volatile storage, such as magnetic disk drives, optical disk drives, a tape drive, etc.). The storage  306  may comprise an internal storage device or an attached or network accessible storage. Programs in the storage  306  are loaded into the memory  304  and executed by the processor  302  in a manner known in the art. The architecture further includes a network card  308  to enable communication with a network, such as an Ethernet, a Fibre Channel Arbitrated Loop, etc. Further, the architecture may, in certain embodiments, include a video controller  309  to render information on a display monitor, where the video controller  309  may be implemented on a video card or integrated on integrated circuit components mounted on the motherboard. As discussed, certain of the network devices may have multiple network cards. An input device  310  is used to provide user input to the processor  302 , and may include a keyboard, mouse, pen-stylus, microphone, touch sensitive display screen, or any other activation or input mechanism known in the art. An output device  312  is capable of rendering information transmitted from the processor  302 , or other component, such as a display monitor, printer, storage, etc. 
   The network adapter  12 ,  308  may be implemented on a network card, such as a Peripheral Component Interconnect (PCI) card or some other I/O card, or on integrated circuit components mounted on the motherboard. 
   The foregoing description of various embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.