doc.: ieee 802.11-07/2555r0 submission september 2007 guenael strutt, motorolaslide 1 mesh points...
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September 2007
Guenael Strutt, Motorola
Slide 1
doc.: IEEE 802.11-07/2555r0
Submission
Mesh points that do not forwardDate: 2007-09-17
Name Affiliations Address Phone email Guenael Strutt Motorola 1064 Greenwood
Blvd – Lake Mary, FL 32771 -- USA
+1-407-562-4050
Jarkko Kneckt Nokia Itämerenkatu 11-13 00180 Helsinki Finland
+358504821550
Dee Denteneer Philips HTC 37 5656 AE Eindhoven The Netherlands
+ 33 40 27 46937
Hideyuki Suzuki Sony 5-1-12 Kitashinagawa Shinagawa-ku Tokyo, Japan
+81-3-5448-3175
Authors:
September 2007
Guenael Strutt, Motorola
Slide 2
doc.: IEEE 802.11-07/2555r0
Submission
Abstract
This submission describes a mechanism that allows low complexity devices to join a Mesh network without a full implementation of HWMP
September 2007
Guenael Strutt, Motorola
Slide 3
doc.: IEEE 802.11-07/2555r0
Submission
Background
• Tuesday May 15th discussion resulted in submission of 11-07/732r0 “resolution of LWMP CIDs”
• Result was mostly elimination of LWMPs from the draft
• Null Routing (the path selection protocol [sic] associated with LWMPs) remains!
• Impetus to keep meshes clean (one ID, one protocol, one metric etc.)– Separate beacon? Separate action frame?
– ToDS, FromDS = 1 Mesh Data
September 2007
Guenael Strutt, Motorola
Slide 4
doc.: IEEE 802.11-07/2555r0
Submission
What is this “special” MP supposed to be?
• Impetus for dealing with battery-operated (or energy-efficient) devices:– Concerns over footprint/complexity of full-fledged HWMP
– “Obligation” to participate in path selection• Burden of maintaining forwarding tables (memory)
– “Obligation” to forward frames• Power consumption burden (Tx and CPU)
September 2007
Guenael Strutt, Motorola
Slide 5
doc.: IEEE 802.11-07/2555r0
Submission
Null Path Selection
• Null Path Selection does a disservice to the Mesh in general and to the Mesh Point in particular– Mesh is not cognizant of the MP– MP is not cognizant of the Mesh
• Authors believe Null Path Selection makes mesh operation more complex and that a simple solution is available– Pros of null routing
• No routing implementation required on terminal device
– Cons of null routing• Proprietary implementation of dual-function MP at the junction of two
networks• Proprietary implementation of next hop selection on terminal device• No guarantee of collaboration between terminal device and dual-function
MP!
September 2007
Guenael Strutt, Motorola
Slide 6
doc.: IEEE 802.11-07/2555r0
Submission
Unavoidable fact
• There will be non forwarding devices that send traffic through the mesh– The questions are: who and how?
non 802.11 entity 802.11 STA 802.11 MP
MPP
MP
802.15
MAP
MP
STA
MP
MP
MP
Well documented Undocumented!?Well documented
September 2007
Guenael Strutt, Motorola
Slide 7
doc.: IEEE 802.11-07/2555r0
Submission
Null routing and non forwarding
NR
F
NR
F
F F
NR
NR
NR
FF
F
FNF
NF
NFIndependent links (no path selection)
Real paths (links selected based on an end-to-end metric)
NR: Null RoutingNF: Non-forwarderF: Forwarder
NF
NF
September 2007
Guenael Strutt, Motorola
Slide 8
doc.: IEEE 802.11-07/2555r0
Submission
Proposed changes to the draft
• Add one paragraph explaining the purpose
• Add 5 conditions allowing MPs to ignore IEs/conditions that would “force” them into becoming forwarders– The real problem is that processing IEs “properly” identifies these
MPs as being forwarders from the other MPs’ point of view
Too simple to work?
September 2007
Guenael Strutt, Motorola
Slide 9
doc.: IEEE 802.11-07/2555r0
Submission
Practical example
A
EC
H
F
ID
B
J
G
K Reference MPForwarding MPNF MP
Mesh Point EDest. NH
Mesh Point C
Mesh Point A Mesh Point B
M Dest. NH M
Dest. NH M Dest. NH M
9
September 2007
Guenael Strutt, Motorola
Slide 10
doc.: IEEE 802.11-07/2555r0
Submission
Practical example
A
EC
H
F
ID
B
J
G
K
• MP E wishes to communicate with MP A
Mesh Point EDest. NH
Mesh Point C
Mesh Point A Mesh Point B
M Dest. NH M
Dest. NH M Dest. NH M
Bcast PREQ10
Reference MPForwarding MPNF MP
September 2007
Guenael Strutt, Motorola
Slide 11
doc.: IEEE 802.11-07/2555r0
Submission
Practical example
A
EC
H
F
ID
B
J
G
K
• Receiving MPs establish a path to the source
Mesh Point EDest. NH
Mesh Point C
Mesh Point A Mesh Point B
M Dest. NH M
Dest. NH M Dest. NH M
Bcast PREQ Reverse path is established
E E 1
11
Reference MPForwarding MPNF MP
Path is not established
September 2007
Guenael Strutt, Motorola
Slide 12
doc.: IEEE 802.11-07/2555r0
Submission
Practical example
A
EC
H
F
ID
B
J
G
K
• Other MPs propagate the path request
• Paths are established selectively
Mesh Point EDest. NH
Mesh Point C
Mesh Point A Mesh Point B
M Dest. NH M
Dest. NH M Dest. NH M
E E 1
Bcast PREQ Reverse path is established
C C 1 C C 1
12
Reference MPForwarding MPNF MP
not sent
not established
September 2007
Guenael Strutt, Motorola
Slide 13
doc.: IEEE 802.11-07/2555r0
Submission
Practical example
A
EC
H
F
ID
B
J
G
K
• Once the destination is found, the forward path is created
Mesh Point EDest. NH
Mesh Point C
Mesh Point A Mesh Point B
M Dest. NH M
Dest. NH M Dest. NH M
E E 1
C C 1 C C 1
Forward path is established
A A 1
Ucast PREP
E C 2
13
Reference MPForwarding MPNF MP
September 2007
Guenael Strutt, Motorola
Slide 14
doc.: IEEE 802.11-07/2555r0
Submission
Practical example
A
EC
H
F
ID
B
J
G
K
• Once the destination is found, the forward path is created
Mesh Point EDest. NH
Mesh Point C
Mesh Point A Mesh Point B
M Dest. NH M
Dest. NH M Dest. NH M
E E 1
C C 1 C C 1
A A 1
E C 2
Ucast PREP Forward path is established
A C 2
C C 1
14
Reference MPForwarding MPNF MP
September 2007
Guenael Strutt, Motorola
Slide 15
doc.: IEEE 802.11-07/2555r0
Submission
Practical example
A
EC
H
F
ID
B
J
G
K
Mesh Point EDest. NH
Mesh Point C
Mesh Point A Mesh Point B
M Dest. NH M
Dest. NH M Dest. NH M
E E 1
C C 1 C C 1
A A 1
E C 2
• Eventually, bidirectional paths are formed
A C 2
C C 1
15
Reference MPForwarding MPNF MP
September 2007
Guenael Strutt, Motorola
Slide 16
doc.: IEEE 802.11-07/2555r0
Submission
What if MP E is a Null Routing entity?
A
EC
H
F
ID
B
J
G
K
• E will select an MP to send its traffic to
• C, H and J do not know how to tell E how good their path is
• E has to establish a peer link with C, H or J—although it does not implement their primary path selection protocol
16
Reference MPForwarding MPNF MP
?? ?
September 2007
Guenael Strutt, Motorola
Slide 17
doc.: IEEE 802.11-07/2555r0
Submission
Conditions for generating HWMP IEs
MP Terminal MP
PREQ
Case A: Original Transmission (Path Discovery)
Case B: Original Transmission (Path Maintenance)
Case C: Root Path Confirmation
Case D1: PREQ Forwarding (no PREP generation)
Case D2: PREQ Forwarding (PREP generation as intermediate MP)
Case E: Proactive PREQ (original transmission)
PREP
Case A: Original transmission
Case B: PREP Propagation
Case C: Intermediate reply
Case D: Gratuitous PREP
PERRCase A: Original transmission
Case B: PERR propagation
RANNCase A: Original transmission
Case B: Forwarding
September 2007
Guenael Strutt, Motorola
Slide 18
doc.: IEEE 802.11-07/2555r0
Submission
MP responsibilitiesMP Terminal MP
PREQ
1. Record (if dest)
2. Update forwarding information (if dest)
3. Initiate RREP (if dest)
4. Proxy (if dest)
5. Intermediate reply
6. Reply and forward
7. Precursor list
PREP
1. Record (if orig)
2. Record dependents
3. Propagate
4. Record proxy at originator (if orig)
5. Record proxy at intermediate node
6. Update precursors
PERR
1. Update records
2. Update route
3. Transmit RERR
RANN
1. Propagate
2. Establish path
3. Record
September 2007
Guenael Strutt, Motorola
Slide 19
doc.: IEEE 802.11-07/2555r0
Submission
Terminology
• Heard in TGs:– “Leaf node”
– “Mesh station”
– “Non forwarding MP”
– “Parasitic MP”
– “Selfish MP”
– “Terminal MP”
– “Lightweight”
– “Low complexity”
September 2007
Guenael Strutt, Motorola
Slide 20
doc.: IEEE 802.11-07/2555r0
Submission
Conclusion
• The Mesh Point that does not forward only performs the following:1. Send a PREQ to whichever destination it would like to establish a path
with2. Process PREPs that are specifically addressed to itself (as a consequence
of step 1.)• Select the PREP with the best metric and the correct sequence number
3. Respond to PREQs that specifically address the terminal MP (or its proxies) as a destination (within implementation limits)• Sometimes the response will based on the value of the path selection metric
4. Keep track of its own sequence number5. Keep track of the sequence number of its destinations (within the
constraints of step 3.)6. Store a next hop, a metric, a lifetime, a sequence number for each of its
destinations (within the constraints of step 3.)
September 2007
Guenael Strutt, Motorola
Slide 21
doc.: IEEE 802.11-07/2555r0
Submission
References
• Normative text: 11-07-2556r0