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WinPE Boot Images Support › OSIM Tools for Windows PE › sdmpcimg Command (32bit and 64bit Version) › Configure TFTP Blocksize to Improve File Transmission Time

Configure TFTP Blocksize to Improve File Transmission Time

By default, the sdmpcimg command requests1456 data bytes per TFTP packet (blocksize) when initiating a TFTP connection. You can configure the requested TFTP blocksize to improve the transmission time of large files. The requested blocksize is defined in an initialization file sdmpcimg.ini which resides in the same folder as the sdmpcimg binary

Note: Applicable only to Windows PE 2 or Windows PE 3 boot images.

To configure TFTP blockize

  1. Open the initialization file smdpcimg.ini located in the following folder in the Image Prepare System server.:
  2. Increase the blocksize value. Acceptable numbers are from 8 to 65464.

    Increasing the number significantly reduces the transmission time of large files.

  3. Save the file.
  4. Create a boot image or update an existing boot image. For more information about updating boot images, see Update Boot Images.

    The updated initialization file is included in the boot image. By default, the boot server accepts the TFTP blocksize that sdmpcimg requests. However, you can configure the boot server to limit the effective TFTP block size. To do this, follow these steps :

    1. Open configuration policy assigned to the boot server in DSM Explorer.
    2. Navigate to DSM, Scalability Server, OSIM, ManagedPC, Server, and reduce the TFTP specific blocksize limit policy as per the value specified in the smdpcimg.ini file.

      The policy limits the number of TFTP data bytes per packet for connections initialized by sdmpcimg

      Note: PXE firmware, DOS boot images and CA ITCM r11.x or r12 Windows PE boot images are not affected by the parameter TFTP specific blocksize limit. The parameter TFTP blocksize limit can be used to limit the blocksize used with these TFTP clients, see PXE-32: TFTP Open Time-out. DOS boot images and CA ITCM r11.x or r12 Windows PE boot images do not support a TFTP blocksize < 1024.