Azure IoT Edge - Device To Cloud message size error

Hi Kishan,

Thank you for your questions, let me try to help:

1. The larger size of the message for IoT Hub is 4KB as you can see in this link: https://zcusa.951200.xyz/en-us/azure/iot-hub/iot-hub-devguide-quotas-throttling?wt.mc_id=AZ-MVP-5003638
2. As you write the code for send the message, you have the responsibility to break the message size to feet the IoT Hub limits
3. One solution is use the Azure Blob Storage on IoT Edge, to store the larger messages, and then just send the object key in the IoT Hub message. This link has more information https://zcusa.951200.xyz/en-us/azure/iot-edge/how-to-store-data-blob?wt.mc_id=AZ-MVP-5003638&view=iotedge-1.5
4. Probably you are talking about this article (https://zcusa.951200.xyz/en-us/azure/iot-hub/iot-hub-devguide-quotas-throttling?wt.mc_id=AZ-MVP-5003638#throttling-details) and the limit for each unit is 160kb per second per unit.

I hope this could help.

Walter

Hello Kishan,

welcome to this moderated Azure community forum.

The maximum size of one message is 256KB.

The term 'message' could be confusing because Microsoft mentions counting messages per day for the maximum throughput.

The maximum throughput is counted in chunks of 4KB (of 0.5 KB for the free tier) so a 256KB message is essentially 64 chunks.

A 6KB message is counted as 2 chunks.

Technically you could send more if you use compression.

The alternatives to send larger messages mentioned by @Walter Coan are valid alternatives.

so:

1. Will a higher tier allow for a larger size? No. Maximum size is 256KB.
2. Would not an edge module break it down to smaller chunks before sending up? or Yes, but the chunks is just for the message count administration. The maximum size stays 256KB.
3. Is there a solution / recommendation to break down a message which IoT Hub can put back on the cloud side? Compression increases the possible message size. You need to send the message in multiple parts yourself (eg. with a correlation ID and part number)
4. I saw another article which said that if we send a large message, the daily limits will be considered based on 4KB chunks. Does that mean a 256KB message will be considered as 65 thousand message rather than a single message when accounted against the daily limits of the tier? 256 devices by 4 is 64 chunks thus 64 'messages' are counted for the daily quota. So, larger message require more units for a given tier.

What I have seen with customers is that a subset of the telemetry is sent to the cloud for remote monitoring via filtering/aggregation on the edge. If all messages are needed in the cloud, separate (custom) logic is used to collect batches of messages (say 10.000 messages or 10 minutes of messages) and send them over a separate channel (eg. the blob storage solution on the edge).

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