# MQTT Transmission tag limit

**URL:** <https://forum.inductiveautomation.com/t/mqtt-transmission-tag-limit/82277>\
**Category:** 3rd Party Modules\
**Created:** [November 23, 2023, 5:01am UTC](https://forum.inductiveautomation.com/t/mqtt-transmission-tag-limit/82277 "2023-11-23T05:01:36Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Eric\_White](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@Eric\_White](https://forum.inductiveautomation.com/u/Eric_White)\
**Post date:** [November 23, 2023, 5:01am UTC](https://forum.inductiveautomation.com/t/mqtt-transmission-tag-limit/82277/1 "2023-11-23T05:01:36Z")

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Hi Everyone  
Im setting up MQTT Transmission client to publish data to an AWS IoT Core Broker and seem to be running into a tag limitation.  
Ignition v8.1.33, MQTT Transmission v4.0.18  
When I increase past 105x instances of a UDT which has 5x tags and 1x parameter, my server connection continually drops. According to the logs, it establishes a connection and drops it straight away. No tags are visible on the broker. If i reduce the quantity of UDT's it becomes healthy straight away.  
I'm assuming there will be some level of overhead for the UDT, but I was able to create 1000 memory tags and connect (vs the 105x5=750 tags from the UDT instances).  
Has anyone experienced similar tag count limitations?  
I tried the 'Optimize UDTs' selection on the Transmitter settings with no change.  
Perhaps I need to increase the options in the 'Filtered Properties' section, although it looks like there is a lot there already.  
I saw somewhere on google that SparkPlug B has a limitation of 65535 'tags', but not 100% how that relates to Ignition and its meta data tags (EngUnit, EngHigh, etc)

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**Author:** ![TChenier](https://avatars.discourse-cdn.com/v4/letter/t/d6d6ee/32.png) [@TChenier](https://forum.inductiveautomation.com/u/TChenier)\
**Post date:** [November 23, 2023, 3:11pm UTC](https://forum.inductiveautomation.com/t/mqtt-transmission-tag-limit/82277/2 "2023-11-23T15:11:06Z")

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This is more likely due to AWS IoT Core's message size limitation of 128 KB.  
When a client publishes a message that exceeds the limit, IoT Core will drop the connection.

[https://aws.amazon.com/iot-core/pricing/#:~:text=You%20can%20send%20and%20receive,metered%20in%205%20KB%20increments.](https://aws.amazon.com/iot-core/pricing/#:~:text=You%20can%20send%20and%20receive,metered%20in%205%20KB%20increments.)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/1/61fde9f1930234239669657a02d22cb8ed0f68b3.png)

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**Author:** ![Eric\_White](https://avatars.discourse-cdn.com/v4/letter/e/85e7bf/32.png) [@Eric\_White](https://forum.inductiveautomation.com/u/Eric_White)\
**Post date:** [November 23, 2023, 11:17pm UTC](https://forum.inductiveautomation.com/t/mqtt-transmission-tag-limit/82277/3 "2023-11-23T23:17:10Z")

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Thanks TChenier, I'd guess thats probably it.  
I have updated my Transmitters Sparkplug Settings and seems to be healthy at the moment. I previously used all Group ID, Edge Node ID and Device ID. I have now removed the Device ID. I'm assuming this splits the tags up instead of one large lump of data.  
Thanks!

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**Author:** ![Mitchell\_Dennis](https://avatars.discourse-cdn.com/v4/letter/m/59ef9b/32.png) [@Mitchell\_Dennis](https://forum.inductiveautomation.com/u/Mitchell_Dennis)\
**Post date:** [November 28, 2023, 12:36am UTC](https://forum.inductiveautomation.com/t/mqtt-transmission-tag-limit/82277/4 "2023-11-28T00:36:11Z")

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> I saw somewhere on google that SparkPlug B has a limitation of 65535 'tags', but not 100% how that relates to Ignition and its meta data tags (EngUnit, EngHigh, etc)

I have a transmitter pushing 173566 tags with no problems.