[Bluez-users] MTU and MRU for Bluetooth

[Bluez-users] MTU and MRU for Bluetooth

[Florian]

Hi

some suggestions for suitable values for MTU / MRU when using pppd and PAP?

Florian



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Re: [Bluez-users] MTU and MRU for Bluetooth

[Marcel Holtmann]

Hi Florian,

> some suggestions for suitable values for MTU / MRU when using pppd and PAP?

are these values not related to the upper protocols like TCP/IP? The
underlaying RFCOMM protocol is a stream, so you don't have a MTU.

Regards

Marcel




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Re: [Bluez-users] MTU and MRU for Bluetooth

[Nicholas A. Preyss]

On  0, Marcel Holtmann <marcel@holtmann.org> wrote:
>> some suggestions for suitable values for MTU / MRU when using pppd and PAP?
> 
> are these values not related to the upper protocols like TCP/IP? The
> underlaying RFCOMM protocol is a stream, so you don't have a MTU.

I think, he wants a MTU size that doesn't lead to fragmentation on the
carrying transport medium. I think this doesn't make much sense due to
the "short" packets of bluetooth, and the fact that L2CAP packets can be
up to 2^16 bytes large.

nicholas


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Re: [Bluez-users] MTU and MRU for Bluetooth

[Marcel Holtmann]

Hi Nicholas,

> I think, he wants a MTU size that doesn't lead to fragmentation on the
> carrying transport medium. I think this doesn't make much sense due to
> the "short" packets of bluetooth, and the fact that L2CAP packets can be
> up to 2^16 bytes large.

actually there is no proof that choosing a different MTU on the L2CAP
level gives you any performance improvements. However a too small MTU
decreases the performance and this is why we are using 1024 even if 672
is the default MTU. Some time ago we discussed this and until now nobody
really proofed that a different MTU is better or that we should make the
L2CAP MTU for RFCOMM configurable, because some upper layer will improve
if we do so. Proof it to me and we will see ;)

Regards

Marcel




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