[Make-wifi-fast] 3g/4g with fq_codel & mobility
loganaden at gmail.com
Tue Nov 22 13:34:27 EST 2016
On Mon, Nov 21, 2016 at 3:27 PM, Jonathan Morton <chromatix99 at gmail.com> wrote:
>> On 21 Nov, 2016, at 13:16, Loganaden Velvindron <loganaden at gmail.com> wrote:
>> I have one of those gl.inet 6416a board. It runs fq_codel on the
>> USB-3g dongle modem interface, and it runs very well at rest.
>> I put it inside a car, and while driving, I notice some induced latency:
>> Can someone who has some understanding of 3g/4g internals shed some
>> light ? Could the 3g/4g modem be buffering due to varying strength of
>> the signal or due to handover in base station ?
> Usually such dongles don’t give direct access to the 3G modem interface. Instead they provide an Ethernet or PPP interface, and do a conversion internally. Ethernet emulation is more common of late, possibly due to the rise of 4G.
> Running fq_codel on such a device without a shaper relies on the buffers in *both* the dongle itself and the driver for the emulated Ethernet device having appropriately sized buffers in aggregate. This is virtually never the case. And that’s just for the upload direction.
> In the download direction you are relying on buffers in the provider’s network and the cell tower. Fq_codel on your own hardware has no effect here.
I think that reducing the buffer size with NCM might be a good start,
particularly with 4G. THere is a lot of work to be done on the
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