Traffic Control

Pedro Estrela pedro.estrela at inesc.pt
Thu Dec 12 11:56:13 EST 2002


hello,
a) The client to client packets on the same AP cell are sent directly to
each other, not passing through the AP at all. It is sufficient for the
destination STA to be in range to receive the packet.

b) if option "ap_bridge_packets == 1" is set, then all received packets on
the AP destinated to another client associated to this AP are sent directly
to the interface on the driver, not passing through TC. this also happens
for Layer2 broadcast and multicast packets. Howerver, currently AFAIK this
facility is not used because point A (see above) causes all traffic to go
_direct_ between stations. Maybe this could be used to extend the coverage
of an AP cell, by enabling client to speak trough the AP (for example: "A"
does not see "B", but both see "AP", so they could speak at hight speed
trough "AP"), but i don't thing that this is implemented, .

c) the remaining packets are those between diferent AP cells, normally for
using bridging & WDS for stations on same subnet. I'm do not know if the
bridge interfaces can be used for TC operation, but somebody on this list
could.

d) for the packets that goes to diferent subnets pass the AP until they
reach the subnet's router, which normally will not be the AP. The only
exception is when the AP is the sole router of the subnet, but that defeats
roaming and scalability.

---------

I am currenltly investigating on IP Mobility coupled with IP QoS Support on
micro-mobility cenarios, and it was this exact problem that i've tryed to
solve 2 years ago. For this, i've designed a micro-mobility protocol called
TIMIP that enables roaming of any IP terminal inside a domain between APs,
which are IP routers.

Using this protocol, all existing IP tecnologies can be used on the 802.11
interface of the APs (because they are _always_ routers). Using this, i was
able to implement the Diffserv techology for managing downlink troughtput
passing to the wireless interface. Another feature is that the TIMIP routing
forces all packts to pass trough the AP, to solve the "A" problem (client to
client direct on the same cell, see above).

I anyone needs further details on my work or 802.11 for this problem, feel
free to ask...

Pedro Estrela

----- Original Message -----
From: "Simon Waters" <Simon at wretched.demon.co.uk>
To: <hostap at shmoo.com>
Sent: Thursday, December 12, 2002 10:58 AM
Subject: Traffic Control


> Pretty basic question to start with...
>
> When using hostap as an Access Point, will client to client IP
> packets on the same subnet (and interface) go through the layers
> that allow Linux tc to regulate bandwidth usage?
>
> I assume some layer 2 stuff definitely won't hit this code, if
> only the administrative traffic. Is there a packet by packet
> description of what is happening anywhere, or must I master the
> source code?






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