Capwap Mailing List: RE: Broadcast/Multicast packet flow

[Nakhjiri Madjid-MNAKHJI1 (Madjid.Nakhjiri]

If this procedure is what we envision for 802.11 data handling, then the AP is 
responsible
for handling the encryption/ decryption of over the air packets. Now, if such a 
heavy operation is done at the AP, why not handle the traffic right there and 
then, why
encapsulte it to AR?
I am not quite sure if I buy the antenna diversity argument that
 Marcus brought up at the meeting. 
That would only be useful, if the standards allow a STA send packets
to multiple APs on the same frequency. CDMA soft handover procedure works 
because the
adjacent base station frequencies are the same, I thought WLAN has a serious 
frequency
planning schema.
In the same way I am hesitant, if encapsulating packets to AR, allows the AR to 
know RSSIs (I am not sure what 802.11K or the RRM group is up to). 
Policy enforcment also should be done right when the packets hit the network, if
the AP can handle encryption, it can definitely handle security policy and it 
should be able to handle a few token bucket filters as well.

Puzzled,

Madjid

-----Original Message-----
From: Pat R. Calhoun [mailto:pcalhoun [at] airespace.com]
Sent: Tuesday, July 22, 2003 8:02 AM
To: rkp [at] intotoinc.com; lwapp [at] frascone.com
Subject: RE: [Lwapp] Broadcast/Multicast packet flow


sounds right.

PatC
-----Original Message-----
From:   Rama krishna prasad [mailto:rkp [at] intotoinc.com]
Sent:   Mon 7/21/2003 8:47 PM
To:     lwapp [at] frascone.com
Cc:     
Subject:        [Lwapp] Broadcast/Multicast packet flow
Hi,
          I am trying to understand the packet flow between wireless stations
          and AR with several APs in between. Appreciate your feedback.
          
          Assumptions:
               Only Layer2 wireless switching with 802.1x key management and
               authentication in this deployment.
               Given SSID (network) is supported by multiple APs.

          Unicast traffic between wireless station1 to wireless station 2 
belonging to
              the same AP and SSID:
                  - AP receives the packet from station 1.
                  - AP de-ciphers it.
                  - Since it is data packet, it encapsulates with LWAPP header 
and 
                         apply any security on the packet and send it over to 
AR.
                  -  AR de-capsulate and removes LWAPP header/802.11 header and 
validates
                        whether this station is successfully authenticated or 
not.
                  - Then it finds out that this packet has to go same AP, based 
on the destination
                     MAC address in 802.3 packet. AR encapsulates the packet 
with 802.11 
                     and LWAPP header and applies any security needed between 
AR and AP.
                 -   AP receives it, decapsulates the LWAPP header.
                 -   AP encrypts the packet with TKIP RC4/RSN unicast key and 
passes it onto the
                       destination station.

           Unicast traffic between wireless stations 1 of AP 1 TO wireless 
station 2 of AP 2 and
                    stations belong to same SSID.
                   - AP1 receives the 802.11 encapsulated 802.3 packet from 
wireless station 1.
                   - AP1 de-cipher it using unicast cipher key.
                   - AP1 encapsulates the 802.11 packet with LWAPP header and 
sends over to the AR.
                          It applies ciphering/authentication based on AR-AP 
security.
                   - AR receives the packet and validates the authentication of 
the station.
                   - AR finds out this destination MAC address belongs to some 
other AP and sends
                        the packet to that AP after encapsulating with 802.11 
and LWAPP headers.
                   - AP2 receives the packet and applies any unicast ciphering 
and sends the packet to
                      destination station.

           Broadcast traffic from a wireless station to all stations of that 
network (SSID):
                  -  Corresponding AP receives the broadcast packet from the 
station.
                  -   It decrypts using global cipher key.
                  -   Passes this packet onto AR after encapsulating with LWAPP.
                  -   AR receives the packet and validates it.
                  -  AR now should find out all APs corresponding to the same 
SSID.
                  -   For each AP
                           AR encapsulates the packet with 802.11 and LWAPP 
header
                              and send it over to the AP.
                           AP decapsulates the LWAPP header and applies global 
cipher key and sends
                                the packet to air.
               
          Is that the flow envisages as part of LWAPP?
 Thanks
 Rama Krishna Prasad
 Intoto Software (India) Pvt Ltd.


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