Donwload of OSIM OS Image with TFTP is very slow

Products

• CA Client Automation - IT Client Manager
• CA Client Automation

Issue/Introduction

During installation of OS on a machine using a OSIM job, the download of OS Image is taking very long time.
Is it possible to increase the download speed ?

Environment

Client Automation - All Versions

Cause

By default TFTP is using a block size of 1456 bytes.

The maximum block size for TFTP is 65464 bytes
See RFC 2348 : TFTP Blocksize Option

The number of octets in a block, specified in ASCII.  Valid values range between "8" and "65464" octets, inclusive. The blocksize refers to the number of data octets; it does not include the four octets of TFTP header.

Resolution

It is possible to increase the TFTP blocksize from 1456 to 65464 for OS Image download

See : Configure TFTP Blocksize to Improve File Transmission Time

 

Example for WinPE 10 x64 Boot Image :

1- Update the file C:\Program Files (x86)\CA\DSM\osimips\os-template\updates\winpe10x64\amd64\ca-osim\sdmpcimg.ini file with : 

blocksize = 65464

 

2- Create a new Boot Image (or update an existing Boot Image) to take in account this new setting

3- Use this new Boot Image to deploy OS. OS download file is done with TFTP blocksize = 65464

 

 

Remarks :

- The configured blocksize is stored in file boot.wim.

With following command we could see which blocksize value is stored in the Boot Image :

cd "C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\dosboot"
findstr /S /I /c:"blocksize = " *

Example :

In winpe1064.2, blocksize is 1456
In winpe1064b.2, blocksize is 65464


- The configured blocksize is for OS Image download. The boot image download is still done using TFTP blocksize 1468 or1456
Example :
File C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\dosboot\winpe1064.2\bootx64.efi is downloaded with blocksize = 1468

260326-07:35:04.3930222L|007684|000001a4|sdmpcworke|sdmpcworker     |npc_tftp_session.cpp|000847|INFO   | TFTP session: Acknowledged blocksize: blksize = 1468
260326-07:35:04.3945613L|007684|000001a4|sdmpcworke|sdmpcworker     |npc_tftp_file.cpp   |000335|INFO   | Successfully opened file C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\dosboot\winpe1064.2\bootx64.efi for reading

File C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\dosboot\winpe1064.2\sources\boot.wim is downloaded with blocksize = 1456

260326-07:35:10.0943417L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_session.cpp|000847|INFO   | TFTP session: Acknowledged blocksize: blksize = 1456
260326-07:35:10.0949419L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_file.cpp   |000335|INFO   | Successfully opened file C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\dosboot\winpe1064.2\sources\boot.wim for readin

Additional Information

Here is an example with a OS Image size = 8 104 281 Bytes (WIN11.caz)

 

With TFTP BlockSize = 65464 the download of file WIN11.caz is taking 20 minutes 43 seconds

260326-07:11:56.7838599L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_session.cpp|000847|INFO   | TFTP session: Acknowledged blocksize: caxblksize = 65464
260326-07:11:56.7861296L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_file.cpp   |000335|INFO   | Successfully opened file C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\WIN11\WIN11\WIN11.caz for reading
260326-07:32:39.1398919L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_file.cpp   |000357|INFO   | Successfully closed file C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\WIN11\WIN11\WIN11.caz

 

With TFTP BlockSize = 1456 the download is taking 1 hour 44 minutes 27 seconds

260326-07:40:06.4356133L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_session.cpp|000847|INFO   | TFTP session: Acknowledged blocksize: caxblksize = 1456
260326-07:40:06.4439370L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_file.cpp   |000335|INFO   | Successfully opened file C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\WIN11\WIN11\WIN11.caz for reading
260326-09:24:23.6612892L|007684|00002750|sdmpcworke|sdmpcworker     |npc_tftp_file.cpp   |000357|INFO   | Successfully closed file C:\Program Files (x86)\CA\DSM\Server\SDBS\var\managedpc\images\WIN11\WIN11\WIN11.caz