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doc.: IEEE /0278r5 Submission March 2008 Javier Cardona et al. Slide 3 Background The origin of this problem is summarized in IEEE Std TM-2007: wireless distribution system (WDS): (...) This standard describes such a frame format, but does not describe how such a mechanism or frame format would be used. The Wi-Fi Alliance is also silent about the use of the WDS frame format.
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doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.
Avoiding Interactions with Lazy-WDS Equipment
Name Affiliation Address Phonee-mail
Javier Cardona +1 415 974 6770
14082223713
978-288-4566
613-763-5827
+49-241-802-5829
Microsoft Corp. +1 425 7064351
cozybit Inc. 165 Jessie St., San Francisco, CA 94105
Raja BanerjeaSandesh GoelRonak Chokshi
Marvell Semiconductor
5488 Marvell Lane, Santa Clara, CA 94087
{rajab,sgoel,rchokshi}@marvell.com
Bilel Jamoussi Bob Withrow
Nortel Networks 600 Technology ParkBillerica, MA 01821
{jamoussi,bwithrow}@marvell.com
Osama Aboul-Magd
Nortel Networks 3500 Carling AvenueOttawa, ONT, CanadaK2H-8E9
Guido Hiertz Philips ComNets, Chair of Communication Networks, RWTH Aachen University, Kopernikusstr. 16, 52074 Aachen, Germany
Thomas Kuehnel One Microsoft Way, Redmond, WA 98052
Date: 2008-03-15
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 2
Abstract
Mesh multicast traffic will trigger unwanted responses on Access Points that implement Lazy-WDS. A frame format change is proposed that will avoid these interactions and make a more efficient use of the 802.11 header address fields.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 3
BackgroundThe origin of this problem is summarized in IEEE Std 802.11TM-2007:
3.170 wireless distribution system (WDS): (...) This standard describes such a frame format, but does not describe how such a mechanism or frame format would be used.
The Wi-Fi Alliance is also silent about the use of the WDS frame format.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 4
Background
So vendors had to get creative. There are two ways APs use WDS frames:
• Static WDS configuration– Network managers manually enter a list of WDS-peers
• Dynamic WDS configuration (most commonly known as Lazy-WDS)– Access Points automatically "discover" WDS peers.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 5
What triggers automatic peer discovery?
• We've empirically established that some Lazy-WDS Access Points will assign WDS-peer status to any STA that transmits a multicast WDS frame (i.e if bit8, 1st octet of the Receiver Address is set).
• Ah, and this is regardless of the value of the protected bit in the frame control header.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 6
The birth of a WDS-peer link
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 7
How does that affect 802.11s?
• Resolution 11-07/799r6 established that mesh will use WDS frame format. This means that each MP that forwards a broadcast/multicast frame in the vicinity of a Lazy-WDS AP will be treated as a WDS-peer.
• There is a large deployed population of Lazy-WDS Access Points... being in the vicinity of one is not hard.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 8
So?
Mesh Points in range of Lazy-WDS APs will cause two serious problems: spurious traffic and DDoS attack on the AP.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 9
Spurious Traffic
• Lazy-APs will retransmit all multicast traffic in the BSS to each and every MP in range.
• The AP does not consider the Mesh Sequence number to limit broadcast flooding.
• N MPs in range -> Each multicast frame is retransmitted N times by the AP.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 10
Spurious Traffic
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 11
Spurious Traffic
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 12
Distributed Denial of Service Attack
• Apparently Lazy-WDS APs were designed to support only a small number of WDS peer links.
• A large number of MPs near a Lazy-WDS AP will carry out a DDoS attack on the Access Point.
• Service to the BSS will be disrupted.
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 13
Distributed Denial of Service Attack
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 14
Because of these problems we propose...
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 15
Broadcast and Multicast Packet Transmission According to Draft 1.09
• Broadcast mesh packets are transmitted using 4 address frame formats with Address 1 as either unicast or broadcast/multicast.
• If Address 1 is unicast there is no issue.
• However if Address 1 is broadcast then…
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 16
Broadcast and Multicast Packet Transmission According to Draft 1.09
11A.5.5.3.1 At Source MPs For non Proxied entriesAddress 1 = Broadcast or MulticastAddress 2 = Source MP MAC addressAddress 3 = Broadcast or MulticastAddress 4 = Source MP MAC Address
From Proxied entitiesAddress 1 = Broadcast or MulticastAddress 2 = Source MP MAC addressAddress 3 = Broadcast or MulticastAddress 4 = Source MP MAC AddressAE: Add 5 = Broadcast or MulticastAE:Addr 6 = Address of Proxied entity
11A.5.5.3.2 At Intermediate and destination MPsFor non Proxied entriesAddress 1 = Broadcast or MulticastAddress 2 = Intermediate MP MAC addressAddress 3 = Broadcast or MulticastAddress 4 = Source MP MAC Address
From Proxied entitiesAddress 1 = Broadcast or MulticastAddress 2 = Intermediate MP MAC addressAddress 3 = Broadcast or MulticastAddress 4 = Source MP MAC AddressAE:Addr 5 = Broadcast or MulticastAE:Addr 6 = Address of Proxied entity
Observations• A lot of redundant fields• Broadcast/multicast address repeated 2 times in non-proxied case• Broadcast/multicast address repeated 3 times in proxied case
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 17
Broadcast and Multicast Packet Transmission According to Draft 1.09
MPs
MP1
MP2
MP3
Address 1 = Broadcast or MulticastAddress 2 = MPs MAC AddrAddress 3 = Broadcast or MulticastAddress 4 = MPs MAC AddressSQ1
Address 1 = Broadcast or MulticastAddress 2 = MPs MAC AddrAddress 3 = Broadcast or MulticastAddress 4 = MPs MAC AddressSQ1
Address 1 = Broadcast or MulticastAddress 2 = MP1 MAC AddrAddress 3 = Broadcast or MulticastAddress 4 = MPs MAC AddressSQ1
Address 1 = Broadcast or MulticastAddress 2 = MP2 MAC AddrAddress 3 = Broadcast or MulticastAddress 4 = MPs MAC AddressSQ1
Determines duplicate Packet based on <MPs, SQ1>
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 18
Broadcast and Multicast Packet Transmission According to Draft 1.09
MPs1MPi1
MPi2
MP3
Address 1 = Broadcast or MulticastAddress 2 = MPs1 MAC AddrAddress 3 = Broadcast or MulticastAddress 4 = MPs1 MAC AddressAE:Addr 5 =Broadcast or MulticastAE:Addr 6= SSQ1
Address 1 = Broadcast or MulticastAddress 2 = MPi1 MAC AddrAddress 3 = Broadcast or MulticastAddress 4 = MPs1 MAC AddressAE:Addr 5 =Broadcast or MulticastAE:Addr 6 = SSQ1
Address 1 = Broadcast or MulticastAddress 2 = MPi2 MAC AddrAddress 3 = Broadcast or MulticastAddress 4 = MPs2 MAC AddressAE:Addr 5 =Broadcast or MulticastAE:Addr 6 = SSQ1
S
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 19
Broadcast and Multicast Packet Transmission Proposed Solution
11A.5.5.3.1 At Source MPs For non Proxied entriesAddress 1 = Broadcast or MulticastAddress 2 = Source MP MAC addressAddress 3 = Source MP MAC Address
From Proxied entitiesAddress 1 = Broadcast or MulticastAddress 2 = Source MP MAC addressAddress 3 = Source MP MAC addressAE:Addr 4 = Address of Proxied entity
11A.5.5.3.2 At Intermediate MPsFor non Proxied entriesAddress 1 = Broadcast or MulticastAddress 2 = Intermediate MP MAC addressAddress 3 = Source MP MAC Address
From Proxied entitiesAddress 1 = Broadcast or MulticastAddress 2 = Intermediate MP MAC addressAddress 3 = Source MP MAC AddressAE:Add 4 = Address of Proxied entity
• Use 3 address formats for all non-proxied broadcast/multicast data frames• Use AE=01 to carry proxied entity in proxied broadcast/multicast frame• Addr1, Addr2, Addr3 are TA, RA and SA respectively• From DS = 1, To DS = 0• Addr4 is proxied entity when AE=01
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 20
Broadcast and Multicast Packet Transmission Proposed Solution
MPs
MP1
MP2
MP3
Address 1 = Broadcast or MulticastAddress 2 = MPs MAC AddrAddress 3 = MPs MAC AddressSQ1
Address 1 = Broadcast or MulticastAddress 2 = MPs MAC AddrAddress 3 = MPs MAC AddressSQ1
Address 1 = Broadcast or MulticastAddress 2 = MP1 MAC AddrAddress 3 = MPs MAC AddressSQ1
Address 1 = Broadcast or MulticastAddress 2 = MP2 MAC AddrAddress 3 = MPs MAC AddressSQ1
Determines duplicate Packet based on <MPs, SQ1>
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 21
Broadcast and Multicast PacketTransmission Proposed Solution
MPs1MPi1
MPi2
MP3
Addr4 is proxied entity when AE=01Address 1 = Broadcast or MulticastAddress 2 = MPs1 MAC AddrAddress 3 = MPs1 MAC AddrAE:Addr 4 = SSQ1
Addr4 is proxied entity when AE=01Address 1 = Broadcast or MulticastAddress 2 = MPi1 MAC AddrAddress 3 = MPs1 MAC AddressAE:Addr 4 = SSQ1
Addr4 is proxied entity when AE=01Address 1 = Broadcast or MulticastAddress 2 = MPi2 MAC AddrAddress 3 = MPs2 MAC AddressAE:Addr 4 = SSQ1
Use <MPs,SQ> to determine duplicate packets.
MPs2
S
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 22
Changes Required1. Modify 11.A.5.5.3.1 and 11.A.5.5.3.2 to describe transmission of 3 address broadcast and
multicast data frames2. Modify Table s2 to allow AE=01 for broadcast/multicast data frames as well
doc.: IEEE 802.11-08/0278r5
Submission
March 2008
Javier Cardona et al.Slide 23
Straw Poll
Would you support the proposed modifications to mesh broadcast frames as presented in this submission?
1) Yes 2) No 3) DK/DC
