thesis presentation: web-integrated smart city infrastructure

Web-Integrated Smart City InfrastructureA caching proxy for hybrid CoAP-HTTP networks.

Supervisor: Candidate:Prof. Dr. Giovanni Malnati Francesco Corazza

Co-supervisors: Prof. Dr. Stefano Ceri (Politecnico di Milano) Prof. Dr. Friedemann Mattern (ETH Zurich)

Tutor: Dipl.-Ing. Matthias Kovatch (ETH Zurich)

26 November 2012

Web-Integrated Smart City Infrastructure

2

Smart Cities?

Francesco Corazza

Ningbo City, China Taipei , Taiwan


5

• • • • • 1. Smart Cities and Internet:

interconnected worlds

• Wireless Sensor Network (WSN)• Spatially distributed autonomous sensors

• Low bandwidth, lossy, unstable medium

• Low energy, power, processing, faults

• IEEEE 802.15.4 – Low Rate WPAN

• Internet of Things• Proprietary solutions

• IPv6 over Low-power WPAN (6LoWPAN)

• IP as common language• “Things” can access standard web services

• “Things“ can be addressed from Internet

• Application-layer interconnection (Web)

The Internet of Things vision

• • •

Internet of Things

(Trillions of nodes)

Fringe Internet(Billions of

nodes)

Core Internet(Millions of nodes)

Francesco Corazza


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• • • • • 1. Smart Cities and Internet:

RESTfy real world

• Web of Things• Web tools in real world (browser, search)

• Physical/virtual mashups

• REST• Everything is a resource

• Architectural constraints

• Scalability, usability, and accessibility

• HTTP

• Constrained Application Protocol • Designed from a subset of HTTP

• Low overhead (UDP fragmentation)

• Machine to Machine (M2M) applications

Francesco Corazza

Intersection originating the WoT

• • •


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• • • • •

1. Smart Cities and Internet:CoAP (Constrained Application Protocol)

• Features• Async communication (request/response)

• Stateless reliability (confirmable/ack)

• Security (CoAPS)

• Observation (native publish/subscribe)

• Blockwise transfers (stateless large transfers)

• Options• Minimum parsing complexity

• Finite number of identifiers

• Caching• Freshness model

• Validation model

• Proxying

Francesco Corazza

1 802.15.4.5 PHYEthernet PHY

2 802.15.4.5 MAC

Ethernet MAC

3 IP

4 UDPTCP

7 CoAPHTTP

IPv6

6LoWPAN

HTTP vs. CoAP protocol stack

• • •


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• • • • • 2. Web-Integration:

proxy deployment

• Positioning• Server-side

• Client-side

• External

• Server-side proxy✓ Effective TCP/UDP mapping

✓ Caching

✓ Multicast

✓ Traffic queuing and limiting

✗ Scalability

✗ Availability

• Uri-mapping• Homogeneous (intercepting proxy)

• Embedded (reverse proxy)

Francesco Corazza

Forward proxy

Reverse proxy

Intercepting proxy

• • •


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Francesco Corazza

• Reverse proxy

• Embedded uri-mapping

HTTP RequestGET http://proxy.mywsn.com/coap/cnb.mywsn.com/b/tempAccept: application/json

2. Web-Integration:cross-protocol mappings (HTTP to CoAP)

• • •


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Francesco Corazza

• HTTP-CoAP mapping• Split HTTP request uri

• Map Accept header

CoAP RequestType: CONFIRMABLE - Uri-host: cnb.myswn.comCode: GET - Uri-port: 5683Options: - Uri-path: b- Accept: 50 - Uri-path: temp


• • •


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Francesco Corazza

• Piggybacked response

• Mag-Age

CoAP ResponseType: ACKNOWLEDGE Options:Code: 2.05 - Content-Type: 50Payload: {temp: 21.5} - Mag-Age: 60


• • • • • •


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Francesco Corazza

• CoAP-HTTP mapping• Cache-Control

• Content-Type

Http ResponseStatus-Code: 200 OKCache-Control: max-age=60Content-Type: application/json; charset=utf-8Body: {temp: 21.5}


• • •


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• • • • • 2. Web-Integration:

caching

• Response code (≠ HTTP)• 2.05, cache

• 2.03, update

• 2.0x, invalidate

• Update max-age• Time passed in cache

• max_age = original_max_age - cache_age

Francesco Corazza

• • •


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• • • • • 3. Design the proxy:

components

• Californium• Rapid prototyping in backend

• Layered architecture

• Apache HttpCore• Minimal memory footprint

• Non-blocking I/O

• Apache HttpClient• Uses HttpCore internally

• 1xx & 3xx codes managed

• Built-in security

• Google Guava Cache• Used in production by Google

• 286.000 tests

Francesco Corazza

• • •


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integration (Californium architecture)

• Layered architecture• Chain of Responsibility

• Single thread model

• Limited to clients and servers

• Pitfalls• Synchronized responses

• Blocking UDP thread

• Missing client abstraction

• Missing server abstraction

Francesco Corazza

Resources

Abstractions

Layers

Communicator

Endpoint

Resource

UDPLayer

TransferLayer

Variable Layers

⟳

• • •


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integration (proxying)

• Encapsulations• Forwarding resources (client)

• Stacks (servers)

• Multi-thread model• Concurrent responses

• Resource thread-safeness

• Non-blocking UDP thread

• Communicator• Two message flows

• Thread-safeness

• Endpoint• Avoid HTTP in CoAP servers

• Encapsulate cache

Francesco Corazza

Servers

Resources

Abstractions

Resource

HTTP Resource

CoAP StackHTTP Stack

CoAP Resource

Proxy Endpoint

Proxy Communicator

⟳⟳⟳⟳

⟳⟳⟳

• • •


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Resources

Abstractions

Servers HTTP StackCoAP Stack

Proxy Communicator

Proxy Endpoint

HTTP Client

CoAP ClientResource

3. Design the proxy:final architecture

Francesco Corazza

HTTP Translator

HTTP Translator

Cache

• • •


• • • • • 4. Evaluation:

performance assessment

• Emulation• Proxy JVM limitation

• CoAP Server Virtualization

• Test client• Pre-compiled requests

• Random distribution of requests

• Normal distribution of resources

• Average of several “runs”

• Produced data• Raw RTT distributions

• RTT/throughput trends

• CDF for RTT

Francesco Corazza

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0 100 200 300 400 500 600 700 800 900 10000

50

100

150

200

250

300

350

400100 requests/s

200 requests/s

400 requests/s

600 requests/s

• • •

Request number

Avera

ge R

ound T

rip T

ime (

ms)


4. Evaluation:performance assessment (CoAP-to-HTTP proxying)

Francesco Corazza

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0 100 200 300 400 500 6000

0.2

0.4

0.6

0.8

1

100 Kbit/s w/ cache 400 Kbit/s w/ cache

100 Kbit/s w/o cache 400 Kbit/s w/o cache

0 50 100 150 200 250 300 350 400 4500

50100150200250300350

Tests w/o cachingTests w/ caching

• • •

Produced throughput (Kbit/s)

Average Round Trip Time (ms)

Avera

ge R

TT (

ms)

Cum

ula

tive D

ensi

ty F

.


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• • • • • 4. Evaluation:

hybrid mashup

Francesco Corazza

• • •

HTTP to CoAPParaimpu control Panel

Twits containing temperatures


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• • • • • Conclusions

• Smart city• Mashup as leading paradigm in the WoT

• Scalability through physical locality

• Chains of proxies

• Lesson learnt• Design for extensibility

• Interoperability through standards

• Cheat sheet for overlapping specifications

• Future work• Standardization process

• Intercepting proxy

• Secure proxy (HTTPS-CoAPS mapping)

Francesco Corazza

0

1000

2000

3000

4000

5000

6000

7000K Lines added

K Unchanged Lines

CoAP draft evolution


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Thank you for the attention

Francesco Corazza

thesis presentation: web-integrated smart city infrastructure

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