Doc.: IEEE 802.11-07/2555r0 Submission September 2007 Guenael Strutt, MotorolaSlide 1 Mesh points that do not forward Date: 2007-09-17 Authors:

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

[email protected]

Jarkko Kneckt Nokia Itämerenkatu 11-13 00180 Helsinki Finland

+358504821550

[email protected]

Dee Denteneer Philips HTC 37 5656 AE Eindhoven The Netherlands

+ 33 40 27 46937

[email protected]

Hideyuki Suzuki Sony 5-1-12 Kitashinagawa Shinagawa-ku Tokyo, Japan

+81-3-5448-3175

[email protected]

Authors:

September 2007


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


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


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


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


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


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


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


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


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 C


M Dest. NH M


Bcast PREQ10

Reference MPForwarding MPNF MP

September 2007


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 C


M Dest. NH M


Bcast PREQ Reverse path is established

E E 1

11


Path is not established

September 2007


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 C


M Dest. NH M


E E 1

Bcast PREQ Reverse path is established

C C 1 C C 1

12


not sent

not established

September 2007


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 C


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


September 2007


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 C


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


September 2007


Slide 15

doc.: IEEE 802.11-07/2555r0

Submission

Practical example

A

EC

H

F

ID

B

J

G

K


Mesh Point C


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


September 2007


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


?? ?

September 2007


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


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


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


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


Slide 21

doc.: IEEE 802.11-07/2555r0

Submission

References

• Normative text: 11-07-2556r0

Documents

Doc.: IEEE 802.11-07/2555r0 Submission September 2007 Guenael Strutt, MotorolaSlide 1 Mesh points that do not forward Date: 2007-09-17 Authors: