Mutation Routing 1

Mutation Routing

Kamin Whitehouse

BLAM Workshop, UCLA

11/8/03

Mutation Routing 3

Outline

• The problem

• Previous approaches

• Mutation Routing – Overview and Demo– Algorithm

• Analysis

• Future Work

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Mobile-to-Mobile Routing

• Stationary nodes

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• Two or more mobile objects

• Groups with unique leader for each object

• Must maintain communication between leaders as the objects move– i.e. mobile-group to

mobile-group routing

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Why is this hard?

• Source must know where destination is, but dest keeps moving

• Could dest just send source its location?– No! Source keeps moving also.– (One way to solve the problem is to have a

solution to the problem)

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Application: PEG

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Application: Ubicomp

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Assumptions

• Assume a dense network

• Assume homogenous nodes ??

• Assume ‘socket’ type of communication

• Always a clean hand-off between leaders

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Outline

• The problem: mobile to mobile routing

• Previous approaches

• Mutation Routing – Overview and Demo– Algorithm

• Analysis

• Future Work

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Routing Mini-Demo

• Any-to-one global broadcast

• Any-to-mobile ??

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Berkeley Landmark Routing

• Crumb-trail allows landmark to forward to mobile– Avoids repeated re-broadcast

• Questions: Bandwidth? Scalable?

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PARC Constrained Broadcast

• Receiver generates gradient; sender uses constrained broadcast– Robust to link/node failures, costs extra messages

• Question: Bandwidth? Energy?

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• Broadcast channel-> collisions

• Scales w/ network size

• #Msgs is high

1. Goal: high-bandwidth

1. Goal: scalable

1. Goal: energy-efficient

Problems

Latency??

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Outline

• The problem: mobile to mobile routing

• Previous approaches

• Mutation Routing – Overview and Demo– Algorithm

• Analysis

• Future Work

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Mutation Routing

• Follow destinations

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Mutation Routing

• Follow destinations• Follow sources

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Mutation Routing

• Follow destinations• Follow sources• Cut corners

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Mutation Routing

• Follow destinations• Follow sources• Cut corners• Cut loops

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Mutation Routing

• Follow destinations• Follow sources• Cut corners• Cut loops• Drop redundant

“baby-steps”

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Mutation Routing

• Follow destinations• Follow sources• Cut corners• Cut loops• Drop redundant

“baby-steps”• Replace dead nodes

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XXX

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Mutation Routing

• Follow destinations• Follow sources• Cut corners• Cut loops• Drop redundant

“baby-steps”• Replace dead nodes• New nodes join route to shorten it

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Mutation Routing 22

Mutation Routing

• 7 behaviors

• 2 simple protocols– Pruning– Recruiting

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Lawnmower Effect

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Outline

• The problem: mobile to mobile routing

• Previous approaches

• Mutation Routing – Overview and Demo– Algorithm (the 2 protocols)

• Analysis

• Future Work

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Preface• Router defined as node with both a child

and parent (strong definition)• Special Cases:

– Source: child=self– Destination: parent=broadcast address

• All messages have 3 extra fields ( 5 bytes)– ID– Child ID– Cost = child->cost + 1

80 03 40 02 01 00 00 00 22 02 33 02 33 02 17 00 56

1 2 3

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Protocol 1: Pruning

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Protocol 1: Pruning• When two nodes a and b hear each other and

cost(A)-cost(B) > 1, shortcut!– Ie: parent(B) := a

• To ensure symmetric links, protocol:– B sends message as normal– A overhears B’s message, becomes a SHORTCUT

by setting child field to B– B overhears A’s message, takes the shortcut by

setting parent to A– Next time B sends, will go to A, who will forward– If A does not get next message from B, (i.e. B did not

take the shortcut) A sets child back to old child (asymmetric link)

• Notice that shortcutting takes no extra messages

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Protocol 2: Recruiting

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Protocol 2: Recruiting

• When a node wants to join the route, first becomes a RECRUIT:=node trying to acquire a parent

• To ensure symmetric links, protocol:– Recruit sets parent to any likely candidate, sets cost to minimum

cost it would like to be, and child to self– Sends message to parent– If parent (or any other node) becomes a shortcut (i.e. sets child

to recruit’s ID), recruit also becomes shortcut and sets child to node it wants to have as child

• Note that recruiting does require an extra message, but will never be used unless that message is necessary anyway

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Recruitment Routing

• Mobile Destinations - pruning

• Mobile Sources - recruiting

• Cut corners - pruning

• Cut loops - pruning

• Drop “baby steps”- pruning

• Replace dead nodes – both

• New nodes join route to shorten it – both

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Outline

• The problem: mobile to mobile routing

• Previous approaches

• Recruitment Routing – Overview and Demo– Algorithm

• Analysis

• Future Work

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Analysis

• Properties:– Robust to asymmetric links– Robust to lossy links– Guarantee of consistent route

• Performance– Message cost– State cost

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Asymmetric Links

• Recruitment Routing is robust to asymmetric links

• Proof:– Discovery finds only symmetric links– Shortcutting preserves symmetric links– Recruiting preserves symmetric links– By induction…

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Lossy Links• Shortcutting:

– Since A and B are on the same route, they both know when the other should be sending.

– This allows silent link-quality estimation (at the cost of quick shortcuts)

– State can be maintained (because this is a static network) to expediate future shortcuts.

• Recruiting– Silent link-quality estimation is impossible– In presence of lossy links, all recruiting can be

suppressed except that supported by known bi-directional reliable links.

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Guarantee of Delivery

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Guarantee of Delivery

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Guarantee of Delivery

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Guarantee of Delivery

• All parents are on route at all times– All parents and children on initial route are on

the route, by definition– Node only change parents to nodes on the

route– If a parent leaves the route while a parent, it is

because child is not on route either, so it doesn’t matter

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Message Cost

• Shortcutting costs one message per routed packet

• Recruiting is done without any message cost for– Mobile-source following– Node replacement

• Recruiting costs multiple messages when non-routing nodes try to shortcut

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Space Cost

• Each node maintains state of each router within communication range– ID– Parent– Child– Cost

• Total of 7 bytes per neighbor/route• Should not have much more than 3

neighbors per route, i.e. 21 bytes per route

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Summary & Conclusion

Mutation Routing– Pruning– Recruiting

1. Near optimal bandwidth

2. Only 21 bytes of state per destination

3. Unbounded sub-optimal latency/energy

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Future Work

• Source Tracking

• Destination Tracking

• Local Optimizations

• Local Repairs

• Global Optimizations

• Global Repairs

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Routing Results

• Delivery Rate:

• # Messages

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15cm/sec 100cm/sec 200cm/sec

Tree

Broadcast

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15cm/sec 100cm/sec 200cm/sec

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Broadcast