doc.: ieee 802.11-07/0358r0 submission march 2007 zhao and walker, intel corpslide 1 thoughts on...
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March 2007
Zhao and Walker, Intel Corp
Slide 1
doc.: IEEE 802.11-07/0358r0
Submission
Thoughts on Peer Capacity
Date: 2007-03-15
Name Company Address Phone email
Meiyuan Zhao Intel Corporation RNB-6-61, 2200 Mission College Blvd, Santa Clara, CA 95052
+1-408-653-5517 [email protected]
Jesse Walker Intel Corporation JF3-206, 2111 N.E. 25th Avenue, Hillsboro, OR 97124
+1-503-712-1849 [email protected]
Authors:
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March 2007
Zhao and Walker, Intel Corp
Slide 2
doc.: IEEE 802.11-07/0358r0
Submission
Abstract
This present discusses the issues with “Peer Capacity” field and its implications to PLM and routing
March 2007
Zhao and Walker, Intel Corp
Slide 3
doc.: IEEE 802.11-07/0358r0
Submission
Comments on Peer Capacity
• General comments: CIDs 2299, 4336, 471, 1158, 1918, 7, 337, 2130, 2132, 3954
• Security comments: CID 5860
• Issues– What’s the meaning of peer capacity or peer link available field?
– Suggest peer link establishment protocol handles the usage of it
– Can it be removed completely?
March 2007
Zhao and Walker, Intel Corp
Slide 4
doc.: IEEE 802.11-07/0358r0
Submission
General Usage
• Peer Capacity is used to control the maximum number of peer links allowed by the MP
• The MP– Announce peer capacity in beacons/probe responses
– Set the value to (capacity - # current peer links)
• The neighboring MP– Decide to initiate the peer link management protocol if the “mesh
capacity” field is non-zero in the received beacons/probe responses
March 2007
Zhao and Walker, Intel Corp
Slide 5
doc.: IEEE 802.11-07/0358r0
Submission
Basic Problem: Unrealiable Announcement
MP A
Peer Capacity = 2
MP BPeer Link Open
MP A
Peer Capacity = 0
MP BPeer Link Open
Peer Capacity = 0
Peer Capacity = 2
March 2007
Zhao and Walker, Intel Corp
Slide 6
doc.: IEEE 802.11-07/0358r0
Submission
Concerns
• Beacon is an unreliable announcement for making decision on PLM protocol initiation
• Protocol can fail (and delayed) when peer capacity > 0
• Protocol could succeed when peer capacity = 0
• In addition, the peer capacity field is the utility enabling DoS
• Question:– Does “peer capacity” field serve the purpose?
– Can we remove this field?
– Should there be a capacity limit at all?
March 2007
Zhao and Walker, Intel Corp
Slide 7
doc.: IEEE 802.11-07/0358r0
Submission
Further Implication: Delayed Procedure
• If MP A is still capable of respond– Either silently discard the
request
– Or send Peer Link Close to reject
• If MP A is not capable of respond (e.g., not allowed to generate more FSM)– Have to silently ignore the
request
MP A
Peer Capacity = 0Peer Link Open
Ignore?Peer Link Close?
March 2007
Zhao and Walker, Intel Corp
Slide 8
doc.: IEEE 802.11-07/0358r0
Submission
Further Implication: Cycles
MP A Peer Capacity = 1
MP C MP B
Peer Capacity = 1
Peer Capacity = 1
• MPs should have at least one spare link instance to reject link establishment requests
• More robust to support simultaneous attempts
• Example:– Resource supports 10 link
instances
– MP uses 9 (established and pending)
– MP reserves 1 link instance to send “peer link close”
March 2007
Zhao and Walker, Intel Corp
Slide 9
doc.: IEEE 802.11-07/0358r0
Submission
Even More: Network Partition• Connected network of n MPs ≥ n-1 links
• Hard to use local operation (e.g., peer capacity) to control the global network topology
• Implications– Tree-based routing vulnerable to
topology changes
– MPs should be able to support at least 2 links
– Peer Link Establishment be aware of tree topology?• Either allow RANN without link
• Or remember previous RANN?
• Policy violation? Feasibility? Complexity?
AB
Root
March 2007
Zhao and Walker, Intel Corp
Slide 10
doc.: IEEE 802.11-07/0358r0
Submission
Implications
• Suggest several system requirements– Each MP supports at least two peer links
– Each MP supports at least one spare link instance to reject Peer Link Open requests
– Mesh supports at least n-1 peer links
• For global view of routing– Need more understanding of PLE implications to routing
– Construct PLM and routing interaction?• New link metric: routing connectivity
– Modify tree-based routing?
• Should MPs simply just support n–1 links, where n = number of MPs in the mesh?
March 2007
Zhao and Walker, Intel Corp
Slide 11
doc.: IEEE 802.11-07/0358r0
Submission
Conclusions
• “Peer Capacity” field is less useful than we thought
• Inefficiency in PLM and routing– Due to lack of system requirements
– Global view of network topology (routing topology)
• Call for more discussions on peer capacity– Necessary?
– System requirements?
– Routing implication?
– Interaction between routing and PLM