1. Proactive Mesh Networks (ProM)
May 2005
Proactive Mesh Networks (ProM)
Date:
Authors:
Name
Company
Address
Phone
Bing Zhang
National Institute of Information and Communications Technology
3-5 Hikaridai, Seika-cho, Soraku-gun, Kyoto, Japan
Oyunchimeg Shagdar
ATR Adaptive Communication Research Laboratories
2-2-2 Hikaridai, Seika-cho, Soraku-gun, Kyoto, Japan
Suhua Tang
Youiti Kado
Oki Electric Industry Co., Ltd.
2-5-7 Honmachi, Chuo-ku, Osaka, Japan
Masanori Nozaki
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2. Outline A proactive layer-2 routing protocol QoS support
May 2005
Outline
A proactive layer-2 routing protocol
Accommodating legacy STA associated with Mesh AP
Topology discovery
WDS unicast/broadcast
QoS support
Load balancing mechanism
Delay based priority control
Multiple radios with distributed channel assignment
Conclusion

3. Proactive Routing Protocol for Mesh Networks (ProM)
May 2005
Proactive Routing Protocol for Mesh Networks (ProM)

4. Architecture - Network Model -
May 2005
Architecture - Network Model -
Connecting Mesh Points based on proactive protocol
Efficiently accommodating Legacy STA associated with Mesh AP
・・・ a(5.2GHz)
・・・ b/g(2.4GHz) MP
Mesh AP
Router
Mesh AP
Server
Mesh Portal
Legacy STA
MP: Mesh Point
Mesh AP
Legacy STA

5. Local Topology Discovery - Hello Message Exchange -
May 2005
Local Topology Discovery - Hello Message Exchange -
Periodically exchanging Hello frame
Advertising 1-hop neighbor information
Upon receiving the Hello frame from neighbors
Checking the link status with 1-hop neighbors
Acquiring the 2-hop neighbor information
MP-A
MP-B FC Du DA
MAC:FF SA
MAC:A
1-hop Neighbor
MAC Address list
FCS
MP-A adds MP list from MP-B that is not included in its 1-hop MP list, into 2-hop MP list.
MP-B adds MP list from MP-A that is not included in its 1-hop MP list, into 2-hop MP list.
Hello frame from MP-A FC Du DA
MAC:FF SA
MAC:B
1-hop Neighbor
MAC Address list
FCS
Hello frame from MP-B
RA: Receiver Address
TA: Transmitter Address
DA: Destination Address
SA: Source Address
WDS Frame FC Du RA TA DA SA
Data
FCS

6. Local Topology Discovery - MPR Selection -
May 2005
Local Topology Discovery - MPR Selection -
MP determines the OLSR-based MPR (Multipoint Relay) set from its 1-hop neighbors.
MP advertises its MPR information in the periodic HELLO messages.
1-hop neighbor
MP-A
2-hop neighbor
MPR of MP-A

7. Topology Discovery - ASAT & TC Messages -
May 2005
Topology Discovery - ASAT & TC Messages -
Mesh AP generates an ASAT (Associated Station Address Table) message which records a MAC address table of legacy STA associated with it.
MP generates a TC (Topology Control) message which includes the links to all MPs of its MPR selector set.
ASAT
Leagacy STAs
Mesh AP-A
Mesh AP-C
MP-B TC

8. Topology Discovery - ASAT & TC Message Forwarding -
May 2005
Topology Discovery - ASAT & TC Message Forwarding -
MPR forwards the ASAT & TC messages from its MPR selectors.
Flooding ASAT & TC messages to all MPs in the network to construct the route to all of MPs and legacy STAs
Mesh
AP-A
MP-B
(MPR)
MP-C FC Du DA
MAC:FF SA
MAC:A
ASAT
SN, MAC:A
FCS FC Du DA
MAC:FF SA
MAC:B
ASAT
SN, MAC:A
FCS
ASAT frame from Mesh AP-A
ASAT frame from Mesh MP-B
(1)
Mesh AP-A broadcasts the ASAT frames
(2)
MP-B retransmitted the ASAT frame by replacing SA with MAC:B
MP-B
(MPR)
MP-A
MP-C FC Du DA
MAC:FF SA
MAC:A
advertised
link set
FCS FC Du DA
MAC:FF SA
MAC:B
advertised
link set
FCS
TC frame from MP-A
TC frame from MP-B
(1)
MP-A broadcasts the TC frames
(2)
MP-B retransmitted the TC frame by replacing SA with MAC:B

9. Example of Unicast Routing
May 2005
Example of Unicast Routing
STA1 sends a data frame of infra-mode to Mesh-AP1.
Mesh-AP1
learn STA2’s association to Mesh-AP3 from its ASAT.
transform STA1’s data frame into a WDS frame.
send the WDS frame to Mesh-AP (RA : Mesh-AP2, TA : Mesh-AP1, SA : STA1, DA : STA2)
Mesh-AP2
forward the WDS frame to Mesh-AP3.(RA : Mesh-AP3, TA : Mesh-AP2, SA : STA1, DA : STA2)
Mesh-AP3
de-transform the WDS frame into the data frame of infra-mode.
forward the data frame to STA2.
Mesh-AP1
Mesh-AP2
Mesh-AP3
(2)
(3)
(1)
(4)
STA1
STA2

10. Example of Broadcast Routing
May 2005
Example of Broadcast Routing
STA1 sends a data frame to Mesh-AP1. (DA : broadcast address)
Mesh-AP1
transform STA1’s data frame into a WDS frame.
broadcast the WDS frame to Mesh-APs.
(RA : broadcast address, TA : Mesh-AP1, SA : STA1, DA : broadcast address)
broadcast the data frame to the associated STAs.
MPR Mesh-APs broadcast the WDS frame.
(RA : broadcast address, TA : own address, SA : STA1, DA : broadcast address)
Mesh-APs
de-transform the WDS frame into the original data frame.
broadcast to the associated STAs.
Mesh-AP1
Mesh-AP2
Mesh-AP3
(2)
(3)
(1)
(2)
(4)
(4)
STA1
STA2
STA3
STA4

11. QoS Support Supporting multi-path routing for load balancing
May 2005
QoS Support
Supporting multi-path routing for load balancing
Every flow tends to choose the same minimum hop route. As a result, some MPs are heavily loaded.
Introducing a flow based multi-path routing to distribute the traffic over the whole networks.
Supporting delay based priority control
Many applications (Voice, Video, etc.) are delay sensitive.
Introducing an end-to-end delay based priority control scheme to reduce the Maximum delay for real time traffics.

12. Load Balancing - Problem Specification -
May 2005
Load Balancing - Problem Specification -
Why load balancing using multiple paths is required
MPs usually use only a path to each destination.
Traffics to the same destination run down into a single path.
It is desirable to balance the load using multiple paths.
Routing Table with Multiple Paths
Path Index DA RA p1 7 3 p2 4
heavy 5 8 3 1 p1 7 2 4 9 p2 6

13. Load Balancing - Related Schemes -
May 2005
Load Balancing - Related Schemes -
Existing Scheduling Schemes
MPs randomly select an RA (= next-hop MP) for each packet destined to the same DA.
Routing Table with Multiple Paths
Path Index DA RA p1 7 3 p2 4 5 8 3 1
Merit
Easy to implement.
Demerit
It causes out-of-order frame delivery. 7 2 4 9 6

14. Load Balancing - Pseudo Flow Based Scheme -
May 2005
Load Balancing - Pseudo Flow Based Scheme -
Pseudo flow :
Type 1 : Identified by DA and SA
Type 2 : Identified by DA and TA (= previous-hop MP)
MPs generate a pseudo flow table.
MPs determine next-hop MP for each pseudo flow based on the current load condition.
Merits
Utilizing WDS header Info.
A pseudo flow’s path is stable.
Packets is kept in order.
Demerit
Cross grained.
Pseudo Flow Table [type 1] 5 8
Flow Index DA SA RA f1 7 8 3 f2 9 4 3 1 f1 f1 7
Pseudo Flow Table [type 2] f2
Flow Index DA TA RA f1 7 1 3 f2 2 4 2 4 9 f2 6

15. Delay Based Priority Control - Problem Specification -
May 2005
Delay Based Priority Control - Problem Specification -
Existing QoS schemes :
the same traffic class (ex. Voice)
= the same priority
End-to-end delay increases with number of hops, congestion and so on!
Small number of hops:
Allowed delay: 50ms; Actual delay: 20ms
Large number of hops :
Allowed delay: 50ms
Actual delay: 80ms 6 3
, Allowed delay: 50ms
Small number of hops: packets reach
their destinations with time to spare
Large number of hops: packet might not
be able to meet the delay requirement 5 2 4 1
Delay based priority control scheme should be considered!
, Allowed delay: 50ms

16. Delay based Priority Control - Proposed Schemes -
May 2005
Delay based Priority Control - Proposed Schemes -
Intermediate nodes dynamically prioritize packets based on their delay requirement and the actual delay characteristics.
the same traffic class　 　the same delay requirement
the actual delay varies with the number of hops and congestion.
Prioritizing mechanism based on
number of hops
time stamp
congestion at intermediate nodes

17. May 2005
Delay based Priority Control - Prioritizing mechanism based on number of hops -
Allowed delay: 50ms Actual delay : 40ms
Allowed delay: 50ms Actual delay : 40ms
Intermediate MPs prioritize packets based on number of hops
Number of hops is learnt from the routing table.
Larger number of hops : higher priority
Forward packets based on their priority level 6 3 2 5 4 1
Routing table
Dest
Number of hops 3 1 6
Priority level: higher

18. Multiple Radios - Distributed Channel Assignment (CA) -
May 2005
Multiple Radios - Distributed Channel Assignment (CA) -
Premise
Multiple interfaces/radios, multiple channels
Basic principle for CA
Least used channel first
Features of proposed scheme
Minimizing co-channel interference
Auto configuration of the mesh network
Guarantee connectivity
Both ends of a link share the common channel
IF0
IF1 C B D A

19. Basic Steps - CA for a Single Link -
May 2005
Basic Steps - CA for a Single Link -
IF0
IF1 C B A D
Initiating Mesh-AP(A)
S1: Get the common channels (send Request message)
S3: Check CA condition and select the least used channel
S4: Assign the channel to the link (send Reserve message)
S6: Actually set the channel
S7: Update channel usage and forward CA message (GlobalCA)
Responding Mesh-AP(B)
S2: Answer with RequestReply, containing the available channels
S5: Answer with ReserveReply
S8: Update CA sequence number and continue CA

20. Example with Distributed Channel Assignment
May 2005
Example with Distributed Channel Assignment 1 3 2 6 10 11 13 4 5 9 7 8 14 15 12 16
Mesh AP1
Mesh AP2
Before CA 1 3 6 10 11 13 12 5 2 4 7 8 9 14 16 15
After CA

21. CA for Newly Joined Mesh AP
May 2005
CA for Newly Joined Mesh AP 1 3 6 2 4 7 17 10 5 9 8 18 14 15 16 12 13 11
Procedures for New Mesh AP
(Mesh-AP-17, 18)
Mesh-AP-17,18
monitor the default channel.
passively scan other channels.
select the least used channel.
send Reserve message to the desired neighbor.
Neighbors respond by sending a Reply.
Mesh-AP17 and 18 newly joining 17 18 7 4 14 8 2 1 15 9 5 3 16 12 10 6 13 11
After CA

22. Conclusions A proactive routing protocol QoS support Multiple radios
May 2005
Conclusions
A proactive routing protocol
Accommodating the legacy STA associated with Mesh AP
Optimizing the amount of link-state information
Supporting unicast and broadcast
QoS support
Flow based load balancing
Alleviating out-of-order frame delivery
Delay based priority control
Prioritizing mechanism based on number of hops
Multiple radios
Assignning the channels with a distributed scheme