Device Management Update network traffic

Device Management Update requires a connection between the Update service and the device to be successful. The device and service exchange a number of messages during this process. The network traffic can be split into these categories:

1. Messages exchanged during device startup.
2. Messages exchanged during the update:
   • Update process initialization.
   • Image download. The size and number of messages in this category depend on the configured maximum transmission unit (MTU) size.
     • Change the value of SN_COAP_MAX_BLOCKWISE_PAYLOAD_SIZE to change the MTU.
     • See advanced Client configuration for more information.
   • Update completion.
3. Messages exchanged after the device restarts.

Example:

This summary is for a 512-byte MTU configuration:

1. Device startup messages

   Device to service: 425 bytes.

   Service to device: 335 bytes.

2. Update process

   • Initialization

     Device to service: 363 bytes.

     Service to device: 771 bytes.

   • Image download

     Device to service: 180 bytes multiplied by the number of blocks.

     Service to device: 4 bytes plus (42 plus MTU), multiplied by the number of blocks.

   • Update completion

     Device to service: 180 bytes.

     Service to device: 159 bytes.

3. Messages after device restart

   Device to service: 553 bytes

   Service to device: 392 bytes

Total

Device to service: 1,521 bytes plus 180 bytes, multiplied by the number of blocks.

Service to Device: 1,657 bytes plus (4 bytes plus [42 plus MTU], multiplied by the number of blocks).

For a 512KB image, and 1,024-byte MTU configuration (200 blocks):

Device to service: 93,681 bytes. Service to device: 547,453 bytes.