MTU agree size on peers

RE: MTU agree size on peers

SwRa — Thu, 03 Oct 2024 13:27:12 GMT

Hi Jithin,

Have you the configured the CONFIG_BT_BUF_ACL_RX_SIZE value in both the appcore and netcore image.? The buffer size must also be configured in the network core image to match the host settings. We have often been using ATT MTU of 247 as max MTU size because it aligns with the max. radio packet length (251), but larger MTUs are supported, and we do that in the throughput sample. Please do compare the setting in your applications against the settings used in our throughput sample: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/samples/bluetooth/throughput/README.html

Best Regards,

Swathy

RE: MTU agree size on peers

Jithin A — Wed, 25 Sep 2024 09:22:01 GMT

Hi,

Why I always getting notified about engineer assigned.

Am I asking any wrong question here? Can anyone please guide me correctly.

RE: MTU agree size on peers

Jithin A — Fri, 30 Aug 2024 06:15:30 GMT

Hi, any update on this.

Can anyone please suggest how can I increase the MTU size on the peripheral end and also it should support on the central device.

RE: MTU agree size on peers

Jithin A — Fri, 23 Aug 2024 11:59:33 GMT

Hi SwRa,

Thank you for the reply

[quote userid="107732" url="~/f/nordic-q-a/113428/mtu-agree-size-on-peers/499536"]The maximum MTU size supported by nRF5340 is 247 bytes. [/quote]

If so, how come RX size is agreed to 512?

[quote userid="107732" url="~/f/nordic-q-a/113428/mtu-agree-size-on-peers/499536"]However, the final decision is made by the central device.[/quote]

This answers my q2, thank you.

[quote userid="107732" url="~/f/nordic-q-a/113428/mtu-agree-size-on-peers/499536"]Could you let me know what you are trying to achieve with higher mtu values.?[/quote]

We need to support DFU, and we cannot use the DFU GATT service because of some security reasons. It takes a lot of time to transfer ~400KB with MTU being 247 bytes. If we can have large MTU we can reduce the DFU download time and also save power.

This is very time consuming for our application.

[quote userid="107732" url="~/f/nordic-q-a/113428/mtu-agree-size-on-peers/499536"]Is both the peripheral and central based on Nordic SoC.?[/quote]

No, Central is basically mobile device.

Can you please suggest any solution to increase the MTU size?

RE: MTU agree size on peers

SwRa — Fri, 23 Aug 2024 11:42:28 GMT

Hi Jithin,

Sorry for the delay..

The maximum MTU size supported by nRF5340 is 247 bytes. This is set by the configuration CONFIG_BT_L2CAP_TX_MTU=247.The MTU (Maximum Transmission Unit) size in a Bluetooth Low Energy (BLE) connection is determined by both the central and peripheral devices. However, the final decision is made by the central device.

Could you let me know what you are trying to achieve with higher mtu values.? Is both the peripheral and central based on Nordic SoC.? You could take a look at this blog post for a better understanding: Building a Bluetooth application on nRF Connect SDK - Part 3 Optimizing the connection

Regards,

Swathy

RE: MTU agree size on peers

Jithin A — Fri, 09 Aug 2024 06:48:39 GMT

Hi,

Anyone can you please explain how the MTU size are handled in NRF5340.

Thank you in advance.

RE: MTU agree size on peers

Jithin A — Mon, 29 Jul 2024 06:49:18 GMT

Hi,

Any update on this.

Can anyone please explain me how MTU size effect on data exchanges over BLE.

And I want to have same TX and RX size, we have some large data transfers to and from so, the above makes our peripheral looks slow when sending data to the mobile application (central)