multiflow

[Bjørn Mork]

Dan Williams <dcbw at redhat.com> writes:

> On Mon, 2019-08-26 at 13:55 +0200, Bjørn Mork wrote:
>> Hello!
>> 
>> The recent PCIe discussion made me realize that it's been a while
>> since
>> I looked at what the USB-IF are up to. From the looks of their
>> website,
>> most of the energy is currently put into making the contents hard to
>> find.
>> 
>> But I did find one document with some relevance: "USB Multiflow
>> Extension for MBIM v1.0" -
>> https://www.usb.org/document-library/usb-multiflow-extension-mobile-broadband-interface-model-v10-and-adopters
>> 
>> This isn't simply adding new MBIM control messages, but is also
>> extending the data transport with the two new types
>> 
>>   - Raw IPv4 or IPv6 Control (signature "IPC" or "ipc")
>>   - Device Service Control (signature "DSC" or "dsc")
>
> Whats the 30-second overview of these types?

They contain control messages related to IP or DS data sessions with
matching session IDs.  So 'IPC\0' contains control messages related to
the 'IPS\0' data session etc.

The only defined control message is MBIM_MULTIFLOW_STATUS with one of
the 3 states

 MBIMMultiFlowStatusOK
 MBIMMultiFlowStatusHighWatermark
 MBIMMultiFlowStatusLowWatermark

and "The number of payload bytes in the queue of the reverse link".

I guess the idea is that you can give e.g. a VoLTE session priority over
an Internet connection, making sure the VoLTE packets are transmitted
first if the session queue is below the low watermark and there is a
congestion on the USB link.

It's probably just as useful as any other QoS stuff...




Bjørn
.