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Mesh points that do not forward

Mesh points that do not forward. Authors:. Date: 2007-09-17. Abstract. This submission describes a mechanism that allows low complexity devices to join a Mesh network without a full implementation of HWMP. Background.

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Mesh points that do not forward

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  1. Mesh points that do not forward Authors: Date: 2007-09-17 Guenael Strutt, Motorola

  2. Abstract This submission describes a mechanism that allows low complexity devices to join a Mesh network without a full implementation of HWMP Guenael Strutt, Motorola

  3. 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 Guenael Strutt, Motorola

  4. 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) Guenael Strutt, Motorola

  5. 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! Guenael Strutt, Motorola

  6. Unavoidable fact • There will be non forwarding devices that send traffic through the mesh • The questions are: who and how? MP MP MP MAP MP MPP STA MP 802.15 non 802.11 entity 802.11 STA 802.11 MP Well documented Well documented Undocumented!? Guenael Strutt, Motorola

  7. Null routing and non forwarding F F NR NF Independent links (no path selection) F F F F NR NF F F NR NF NR NF NR: Null Routing NF: Non-forwarder F: Forwarder NF NR Real paths (links selected based on an end-to-end metric) Guenael Strutt, Motorola

  8. 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? Guenael Strutt, Motorola

  9. Practical example G F H Mesh Point E Mesh Point C Dest. NH M Dest. NH M A J C Mesh Point A Mesh Point B E Dest. NH M Dest. NH M B K D I Reference MP Forwarding MP NF MP 9 Guenael Strutt, Motorola

  10. Bcast PREQ Practical example G • MP E wishes to communicate with MP A F H Mesh Point E Mesh Point C Dest. NH M Dest. NH M A J C Mesh Point A Mesh Point B E Dest. NH M Dest. NH M B K D I Reference MP Forwarding MP NF MP 10 Guenael Strutt, Motorola

  11. Practical example G • Receiving MPs establish a path to the source F H Mesh Point E Mesh Point C Dest. NH M Dest. NH M E E 1 A J C Mesh Point A Mesh Point B E Dest. NH M Dest. NH M B Path is not established K D I Reference MP Forwarding MP NF MP Bcast PREQ Reverse path is established 11 Guenael Strutt, Motorola

  12. Practical example G • Other MPs propagate the path request • Paths are established selectively F H Mesh Point E Mesh Point C Dest. NH M Dest. NH M E E 1 A J C Mesh Point A Mesh Point B E Dest. NH M Dest. NH M C C 1 C C 1 B not sent not established K D I Reference MP Forwarding MP NF MP Bcast PREQ Reverse path is established 12 Guenael Strutt, Motorola

  13. A A 1 E C 2 Ucast PREP Forward path is established Practical example G • Once the destination is found, the forward path is created F H Mesh Point E Mesh Point C Dest. NH M Dest. NH M E E 1 A J C Mesh Point A Mesh Point B E Dest. NH M Dest. NH M C C 1 C C 1 B K D I Reference MP Forwarding MP NF MP 13 Guenael Strutt, Motorola

  14. C C 1 A C 2 Ucast PREP Forward path is established Practical example G • Once the destination is found, the forward path is created F H Mesh Point E Mesh Point C Dest. NH M Dest. NH M E E 1 A A A 1 J C Mesh Point A Mesh Point B E Dest. NH M Dest. NH M C C 1 C C 1 B E C 2 K D I Reference MP Forwarding MP NF MP 14 Guenael Strutt, Motorola

  15. Practical example G • Eventually, bidirectional paths are formed F H Mesh Point E Mesh Point C Dest. NH M Dest. NH M C C 1 E E 1 A A C 2 A A 1 J C Mesh Point A Mesh Point B E Dest. NH M Dest. NH M C C 1 C C 1 B E C 2 K D I Reference MP Forwarding MP NF MP 15 Guenael Strutt, Motorola

  16. What if MP E is a Null Routing entity? G • 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 F H A ? ? ? J C E B K D I Reference MP Forwarding MP NF MP 16 Guenael Strutt, Motorola

  17. Conditions for generating HWMP IEs Guenael Strutt, Motorola

  18. MP responsibilities Guenael Strutt, Motorola

  19. Terminology • Heard in TGs: • “Leaf node” • “Mesh station” • “Non forwarding MP” • “Parasitic MP” • “Selfish MP” • “Terminal MP” • “Lightweight” • “Low complexity” Guenael Strutt, Motorola

  20. Conclusion • The Mesh Point that does not forward only performs the following: • Send a PREQ to whichever destination it would like to establish a path with • 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 • 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 • Keep track of its own sequence number • Keep track of the sequence number of its destinations (within the constraints of step 3.) • Store a next hop, a metric, a lifetime, a sequence number for each of its destinations (within the constraints of step 3.) Guenael Strutt, Motorola

  21. References • Normative text: 11-07-2556r0 Guenael Strutt, Motorola

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