[Make-wifi-fast] [bbr-dev] Aggregating without bloating - hard times for tcp and wifi

[Bob McMahon]

I don't know Qualcomm's offerings but here are some from Broadcom.

https://www.broadcom.com/products/wireless/wireless-lan-infrastructure/bcm67263

The BCM4916 forwarding plane is done with a network processor and doesn't
run Linux.  Linux may be used to build the forwarding tables and this is
standard "merchant silicon" forwarding approcch, let some CPU/stack build
the topology tables and then realize the packet forwarding in
(programmable) hardware.

https://docs.broadcom.com/doc/4916-PB1XX

Bob

On Tue, Nov 22, 2022 at 12:28 PM Bob McMahon <bob.mcmahon at broadcom.com>
wrote:

> Some main purposes of the WiFi CPU is 802.3 to 802.11 L2 translational
> bridging and handling 802.11 protocols for things like association. Most
> forwarded packets don't hit the main CPU anymore. This first sw to hw
> transition occurred decades ago with real internet routers (equipment that
> run IGPs and BGP) which started as software in the early 90s and then moved
> to hardware. The same engineering has been happening for home gateways or
> WiFi APs bridging wired to wireless.
>
> Bob
>
> On Tue, Nov 22, 2022 at 12:16 PM David Lang <david at lang.hm> wrote:
>
>> sorry, when I was saying 'the cpu', I was meaning the main one running
>> linux,
>> not something that's part of the wifi chipset.
>>
>> I would be very surprised if the wifi chipset is doing any packet
>> routing, as
>> opposed to just sending the packets to the main processor.
>>
>> Remember, the common case isn't forwarding from one wifi device to
>> another, it's
>> moving between wifi devices and the wired uplink.
>>
>> David Lang
>>
>> On Tue, 22 Nov 2022, Bob McMahon wrote:
>>
>> > An AP's radio complex may have a CPU but that doesn't mean it is the
>> > standard linux stack as most think of it. Many consider this as part of
>> > "firmware" which can be Linux, a Linux derivative or other.  Also, there
>> > are some levels of wired/wireless forwarding plane integration done at
>> the
>> > hardware level that many might be surprised by.
>> >
>> > Bob
>> >
>> > On Tue, Nov 22, 2022 at 12:03 PM David Lang <david at lang.hm> wrote:
>> >
>> >> On Tue, 22 Nov 2022, Bob McMahon via Make-wifi-fast wrote:
>> >>
>> >>> Finally, many (most?) APs are forwarding and feeding packets at at the
>> >>> hardware level so not sure that the linux stack matters as much for
>> an AP
>> >>> based analysis, particularly when considering multi user
>> transmissions,
>> >>> i.e. multiple WiFi clients are active and sharing TXOPs.
>> >>
>> >> APs forward packets within the switch at the hardware level, but the
>> >> radios have
>> >> to go through the CPU, so any wired <-> wireless needs to go through
>> the
>> >> CPU,
>> >> and I would be incredibly surprised if the wifi chips did wireless <->
>> >> wireless
>> >> routing at the hardware level.
>> >>
>> >> David Lang
>> >>
>> >
>> >
>>
>

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