Patent Application
20140047124
The Trivial File Transfer Protocol (TFTP) is a simple file transfer protocol that is widely used. TFTP can be used to transfer a file to a first TFTP agent from a second TFTP agent. The transfer of the file is initiated by a TFTP request packet (also referred to herein as simply a “request packet”), and can take the form of a read request or a write request. The TFTP agents are often referred to as a TFTP client and TFTP server respectively, where the TFTP client is the agent that sends the TFTP request packet and the TFTP server is the agent that services the TFTP request packet. The details of TFTP are defined in various Internet Engineering Task Force (IETF) Request for Comments (RFC) documents, including RFC 783 (TFTP Protocol (revision 1)), RFC 1350 (TFTP Protocol (revision 2)), RFC 906 (Bootstrap loading using TFTP), RFC 1785 (TFTP Option Negotiation Analysis), RFC 2347 (TFTP Option Extension), RFC 2348 (TFTP Blocksize Option), and RFC 2349 (TFTP Timeout Interval and Transfer Size Options). The TFTP described in such IETF RFC documents is also referred to here as “standard TFTP.”
TFTP requires the TFTP agent that is sending a file to divide the file into a number of equally sized blocks of data, and send each block of data as payload data in a corresponding TFTP data packet (also referred to herein as simply a “data packet”). TFTP also requires that the TFTP agent receiving said file, send an acknowledge packet (also referred to herein as simply an “ACK”) back to the sending TFTP agent for each data packet received. TFTP also requires that the sending TFTP agent, after sending a given packet, wait until an ACK is received from the receiving TFTP agent before sending a subsequent packet. If the sending TFTP agent does not receive an ACK within a 2 second timeout, or receives an ACK with its block number set to the last send block minus 1, the sending TFTP agent re-sends the given packet.
One application of TFTP is in avionic devices. For example, some avionic standards, such as Aeronautical Radio, Incorporated (ARINC) Standard 615A, specify that standard TFTP can be used for loading data from a data loader outside to an aircraft to devices within the aircraft.
One embodiment is directed toward a method of transferring data using a Trivial File Transfer Protocol (TFTP). The method includes initiating transfer of a file from a second TFTP agent to a first TFTP agent based on a TFTP request packet and initiating transfer of data from the first TFTP agent to another device according to a second protocol. The method also includes receiving a first subset of TFTP data packets containing first payload data for the file, extracting the first payload data from the first subset of TFTP data packets, conforming the first payload data to the second protocol, and sending the first payload data to the other device prior to receiving a last TFTP data packet for the file, wherein the first payload data is sent in compliance with the second protocol. The method also includes receiving one or more remaining TFTP data packets containing the remaining payload data for the file, the one or more remaining TFTP data packets including the last TFTP data packet for the file, extracting the remaining payload data from the one or more remaining TFTP data packets, and sending the remaining payload data to the other device.
Understanding that the drawings depict only exemplary embodiments and are not therefore to be considered limiting in scope, the exemplary embodiments will be described with additional specificity and detail through the use of the accompanying drawings, in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the exemplary embodiments.
The ACK requirements of TFTP provide high integrity, but can result in slow data transfer since each data packet must be acknowledged before a subsequent data packet can be sent. This sluggish data transfer can be exacerbated when there is a network connection between the first and second TFTP agents involving multiple hops as can be the case when loading data onto avionic devices.
To transfer a file from the data loading device 102 to the target device 104, a TFTP session is initiated based on a TFTP request packet. In an example, the TFTP session is initiated by the second TFTP agent 110 sending a TFTP write request packet to the first TFTP agent 108. In another example, the TFTP session is initiated by the first TFTP agent 108 sending a TFTP read request packet to the second TFTP agent 110. In either case, once the TFTP session is initiated, the second TFTP agent 110 divides the file up into one or more blocks of data and sends a plurality of data packets containing the data to the first TFTP agent 108 in compliance with TFTP.
The first data packet sent by the second TFTP agent 110 is sent to the network interface device 106. The network interface device 106 forward the first data packet to the first TFTP agent 108 on the target device 104. After receiving the first data packet, the first TFTP agent 108 sends an ACK to the network interface device 106. The network interface device 106 forwards the ACK to the second TFTP agent 110 on the data loading device 102. The second TFTP agent 110 waits until the ACK is received before sending the second data packet. When the ACK is received, the second TFTP agent sends the second data packet. This process is repeated as many times as necessary to send the entire file from the second TFTP agent 110 to the first TFTP agent 108. As shown, in addition to complying with TFTP communications between the data loading device 102, the network interface device 106, and the target device 104 can involve higher level protocols as well such as User Datagram Protocol (UDP), Internet Protocol (IP), and Ethernet protocol.
The TFTP protocol discussed above results in a latency for each data packet equal to an amount of time to traverse from the second TFTP agent 110 to the network interface device 106, to the first TFTP agent 108, and back again. This can be a significant amount when sending a large file with many data packets. Moreover, the amount of time required to send a file using the above protocol can be further exacerbated by slow network links and/or systems with more than one network hop.
The embodiments described herein provide for a system and method that enables TFTP compliance for the data transfer from a data loading device and reduces the overall time required to transfer the file. In particular, the embodiments provide for a system and method where a first TFTP agent is implemented in an intermediary device in the multi-hop communication path between a data loading device and a target device. The first TFTP agent on the intermediary device can satisfy TFTP with a second TFTP agent on the data loading device. The first TFTP agent can also transfer payload data from the data packets received from the second TFTP agent to the target device prior to receiving all the data packets for the file being transferred. That is, the first TFTP agent does not wait until receiving the entire file before sending data from the file to the target device 104. Instead, the first TFTP agent sends portions of the file in a piecemeal fashion to the target device 104 as the portions are received at the first TFTP agent. Thus, transferring of the file from the first TFTP agent to the target device can commence before the file is completely received at the intermediary device. Moreover, since the first TFTP agent is on the intermediary device, data packets sent by the second TFTP agent only need to wait for acknowledgment from the intermediary device and not the target device. Some embodiments also enable the data received at the intermediary device to be sent to multiple target devices in parallel, resulting in reduced time as compared to performing the process described with reference to
The data loading device 202 includes one or more files to be transferred to the target device 204. As describe herein a “file” can include data of any type (such as a complete or partial application layer file, an image of a disc, or other data) where a single “file” corresponds to all the data to be sent over a given TFTP transfer session. In an example, the data loading device 202 is an avionic data-loader configured to be coupled to devices on an aircraft and configured to communicate with devices on the aircraft using ARINC Standard 615A. The target device 204 is an avionic device on an aircraft. Communications between the data loading device 202 and the target device 204 occur via an intermediary device 206. The example shown in
As mentioned above, one or more files on the data loading device 202 can be transferred to the target device 204. In compliance with ARINC 615A, the data loading device 202 is configured to implement TFTP for transfer of the file(s). To implement a file transfer using TFTP the intermediary device 206 implements a first TFTP agent 208 and the data loading device 202 implements a second TFTP agent 210. To transfer the file from the second (sending) TFTP agent 210 to the first (receiving) TFTP agent 208, a TFTP session is initiated based on a TFTP request packet. In an example, the TFTP session is initiated by the second TFTP agent 210 sending a TFTP write request packet to the first TFTP agent 208. In another example, the TFTP session is initiated by the first TFTP agent 208 sending a TFTP read request packet to the second TFTP agent 210. In either case, once the TFTP session is initiated, the second TFTP agent 210 divides the file up into one or more blocks of data and sends a plurality of data packets containing the data to the first TFTP agent 208 in compliance with TFTP.
The first data packet is sent from the second TFTP agent 210 to the first TFTP agent 208 on the intermediary device 206. After receiving the first data packet, the first TFTP agent 208 sends an ACK to the second TFTP agent 210. Upon receiving the ACK at the second TFTP agent 210, the second TFTP agent 210 sends the second data packets to the first TFTP agent 208. If a data packet is not received successfully at the first TFTP agent 208 (e.g., is corrupted), the first TFTP agent 208 can send an ACK to the second TFTP agent 210 where the ACK has its block number set to the last (successfully) received data packet. Upon receiving such an ACK, the second TFTP agent 210 re-sends the data packet that was sent prior to the ACK. This process continues in compliance with TFTP until all blocks of data for the file have been sent. After all the blocks of data for the file have been sent, the second TFTP agent 210 sends a last data packet for the file. The last data packet is defined by TFTP to indicate that all the blocks of data for the file have been transferred. The last data packet contains zeroes as payload data which identifies the data packet as a last data packet. After receiving the last data packet, the first TFTP agent 208 sends an ACK to the second TFTP agent 210 and ends the TFTP session for transferring the file. Upon receiving the ACK, the second TFTP agent 210 also ends the TFTP session for transferring the file. In this way, the file is transferred from the second TFTP agent 210 to the first TFTP agent 208 in compliance with TFTP.
While the TFTP session for transferring the file is active and before the last data packet for the file is received, the first TFTP agent 208 transfers data for the file from the data packets that have been received to the target device 204. As used herein the “last data packet for the file” is a last data packet as defined by TFTP that is sent for the TFTP session to transfer the file. Thus, the first TFTP agent 208 sends data for the file obtained from data packets received during the TFTP session to the target device 204, before receiving all the data for the file and, therefore, before receiving all the data packets for the TFTP session. This transfer of data can occur on a regular basis as subsets of data from the file are received. For example, the first TFTP agent 208 can be configured to, after receiving a subset of data packets from the second TFTP agent 210, extract the payload data from the subset of data packets, conform the payload data to a second protocol for sending to the target device 204, and send the conformed payload data to the target device 204. The first TFTP agent 208 can then repeat these acts on the next subset of data packets received. This process can continue until all the payload data from all the data packets for the file has been sent to the target device 204.
In example, each subset of data packets can include the same number of data packets. In one example, each subset of data packets includes a single data packet. In another example, each subset of data packets includes 10 data packets. Regardless of the number of data packets in a subset, the first TFTP agent 208 can be configured to act on the data packets as a subset in order to send data to the target device 208. In some examples, receiving a completed subset of data packets (e.g., a number of packets that completes the subset) is the trigger in which the first TFTP agent 208 is configured to react to perform the above acts of extracting, conforming, and sending. Thus, the first TFTP agent 208 can receive data packets in compliance with TFTP from the second TFTP agent 210. Upon receiving a completed subset of data packets (e.g., before receiving the next subset of data packets), the first TFTP agent 208 can perform the above acts of extracting, conforming, and sending, and this can be repeated for each completed subset of data packets received. Accordingly, the data for the file can be sent to the target device 204 in a piecemeal fashion as it is received at the first TFTP agent 208. In some examples, the number of data packets in different subsets can differ. In any case, the first TFTP agent 208 is configured to act on data packets for a file before receiving the last data packet for the file to send the payload data from the data packets to the target device 204.
Extracting the protocol data can include removing the payload data from its packet by stripping off all the protocol overhead from TFTP and higher layers such as from UDP, IP, and Ethernet to obtain raw data for the file. As mentioned above, this data can then be conformed to a second protocol for sending to the target device 204. Conforming the data to the second protocol can include re-packaging the data in compliance with the second protocol. The second protocol can be any suitable communication protocol, including TFTP. According, in one example, the data obtained from the data packets is re-packaged and sent to the target device 204 in compliance with TFTP in a different TFTP session from the TFTP session used for transfer of the file from the second TFTP agent 210 to the first TFTP agent 208. In another example, the second protocol can be a simple protocol where limited overhead information is sent to the target device 204 in order to reduce the time required to send the data.
After the first TFTP agent 208 receives the last data packet for the file and ends the TFTP session, the first TFTP agent 208 can perform the above process of extracting, conforming, and sending on the remaining data packets for which this process has not been completed. In this way, the data for the file can be transferred from the first TFTP agent 208 to the target device 204.
In examples including multiple intermediary devices, any of the intermediary devices can be configured with the functionality of the first TFTP agent 208 described herein. In a particular implementation having multiple intermediary devices, the intermediary device that is coupled directly to the data loading device 202 is configured with the functionality of the first TFTP agent 208.
The instructions 304-1 on the data loader device 202 and the instructions 304-2 on the intermediary device 206 include UDP/IP instructions 314. The UDP/IP instructions 314 implements the UDP/IP suite of protocols and enables application-layer instructions 315 to communicate over the communication medium 312 using the UDP/IP suite of protocols. The UDP/IP instructions 314 also include respective TFTP instructions 316-1, 316-2. The TFTP instructions 316-1 on the data loader device 202 is configured to implement the second TFTP agent 210 as described here and the TFTP instructions 316-2 on the intermediary device 206 is configured to implement the first TFTP agent 208 as describe here. In general, the TFTP instructions 316-1, 316-2 includes standard TFTP functionality 318 that implements standard TFTP as described above with respect to
Although the TFTP instructions 316-1, 316-2 is logically considered to be a part of the UDP/IP instructions 314, at least a part of the TFTP instructions 316-1, 316-2 can be integrated directly into an item of instructions that is otherwise considered to reside outside of the UDP/IP instructions 314 (for example, application layer instructions 315). Also at least a part of the TFTP instructions 316-1, 316-2 can be implemented as a library (or other similar mechanism) that other instructions (for example, application-layer instructions 315) can link to in order to use the TFTP instructions 316-1, 316-2.
The instructions 304-3 on the target device 204 can include second communication protocol instructions 322 that are configured to implement the second communication protocol for transfer of data from the intermediary device 206 to the target device 204. The instructions 304-2 on the intermediary device 206 can also be configured to implement the second communication protocol to transfer data received during a TFTP session from the data loading device 202 to the target device 204.
In an example, each of the target devices 204 communicates with the intermediary device 206 using the same communication protocol. In such an example, the first TFTP agent 208 can conform the extracted data according to said same communication protocol and send a copy of the conformed to each target device 204. In another example, one or more disparate communication protocols can be used for different target devices 204 and the intermediary device 206 creates multiple copies of the extracted data conforms each copy of the extracted data in compliance with a communication protocol used by one or more of the target devices 204 before sending to correspondingly conformed data to each target device 204.
If the target device 206 does not receive the expected data, the target device 204 can send a NAK back to the first TFTP agent 208 on the intermediary device 206. The network device 502 can obtain the NAK from the target device 204 and forward the NAK to the intermediary device 206. Upon receiving the NAK, the first TFTP agent 208 can take action to re-send the expected data to the target device 204. In an example, the intermediary device 206 temporarily stores some or all of the payload data extracted from the data packets in the media 306 or in the memory 308. To re-send the expected data to the target device, the first TFTP agent 208 can retrieve the expected data from temporary storage in media 306 or memory 308, conform the expected data to the second communication protocol, and send the expected data to the target device 204. In some implementations of such an example, the first TFTP agent 208 can temporarily store all payload data that has been extracted and has not been successfully received at the target device 204. That is, the first TFTP agent 208 can temporarily store all payload data that has been extracted, and continually remove from the temporary storage any payload data that has been successfully received at the target device 204. The first TFTP agent 208 can determine if given payload data has been successfully received based on an ACK received from the target device 204 or the lack of a NAK received at the target device 204 (for example, if no NAK is received at the first TFTP agent 208 within a period of time after sending the data or within a period of time after sending subsequent data). In other implementations, the first TFTP agent 208 can temporarily store all payload data extracted until all the payload data has been successfully received at the target device 204. In another example, instead of temporarily storing the extracted payload data, the first TFTP agent 208 can, after receiving all the data blocks for the file from the second TFTP agent 210 and ending that TFTP session. Initiate another transfer of the file by sending a read-request for the file to the data loading device 202. Upon receiving data blocks for the file, the first TFTP agent 208 can re-send all the payload data or only the portions of the payload data not successfully received by the target device 204. Any of the above methods for re-sending data to the target device 204 can be extended to include multiple target devices 204.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiments shown. In particular, although system 200, 400, 500, and 600 have been illustrated as distinct systems, it should be understood that any and all of the features described with respect to systems 400, 500, and 600 can be incorporated into system 200.
