Thesis Presentation: Web-Integrated Smart City Infrastructure

Web-Integrated
Smart City Infrastructure
A 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 Zürich)
Tutor:
Dipl.-Ing. Matthias Kovatch (ETH Zürich)

26 November 2012

Web-Integrated Smart City Infrastructure Francesco Corazza

Smart Cities?

Ningbo City, China Taipei , Taiwan

2


•
1. Smart Cities and Internet: •
•
interconnected worlds •
•
• Wireless Sensor Network (WSN) The Internet of Things vision
• Spatially distributed autonomous sensors Internet of Things
• Low bandwidth, lossy, unstable medium (Trillions of nodes)

• Low energy, power, processing, faults
• IEEEE 802.15.4 – Low Rate WPAN
Fringe Internet
• Internet of Things (Billions of nodes)

• Proprietary solutions
Core Internet
• IPv6 over Low-power WPAN (6LoWPAN) (Millions of nodes)

• IP as common language
• “Things” can access standard web services
• “Things“ can be addressed from Internet
• Application-layer interconnection (Web)

5


•
•
RESTfy real world •
•
• Web of Things
• Web tools in real world (browser, search) Intersection originating the WoT
• 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

7


•
•
CoAP (Constrained Application Protocol) •
•
• Features
• Async communication (request/response) HTTP vs. CoAP protocol stack

• Stateless reliability (confirmable/ack)
7 HTTP CoAP
• Security (CoAPS)
• Observation (native publish/subscribe) 4 TCP UDP
• Blockwise transfers (stateless large transfers)
IPv6
• Options 3 IP
6LoWPAN
• Minimum parsing complexity
• Finite number of identifiers 2 Ethernet MAC 802.15.4.5 MAC

• Caching
1 Ethernet PHY 802.15.4.5 PHY
• Freshness model
• Validation model

• Proxying

9


•
2. Web-Integration: •
•
proxy deployment •
•
Forward proxy

• Positioning
• Server-side
• Client-side
• External
Reverse proxy
• Server-side proxy
✓ Effective TCP/UDP mapping
✓ Caching
✓ Multicast
✓ Traffic queuing and limiting
✗ Scalability
✗ Availability
Intercepting proxy

• Uri-mapping
• Homogeneous (intercepting proxy)
• Embedded (reverse proxy)

11


•
•
cross-protocol mappings (HTTP to CoAP)

• Reverse proxy HTTP Request
GET http://proxy.mywsn.com/coap/cnb.mywsn.com/b/temp
Accept: application/json
• Embedded uri-mapping

Constrained Network
Proxy
coap://proxy.mywsn.com Building CNB
HTTP Client http://proxy.mywsn.com
http://httpnode.example.com 2001:620:8:35db::1f Room A
170.1.52.200 2001:620:8:35C1::xxx

5683
Room B
80

Border Router CoAP Server
Internet 2001:620:8:101f::1 coap://cnb.mywsn.com/b/temp
2001:620:8:101f::64

13


•
•
CoAP Request
• HTTP-CoAP mapping Type: CONFIRMABLE - Uri-host: cnb.myswn.com
• Split HTTP request uri Code: GET - Uri-port: 5683
Options: - Uri-path: b
• Map Accept header
- Accept: 50 - Uri-path: temp

Constrained Network
Proxy
170.1.52.200 2001:620:8:35C1::xxx

5683
Room B
80

2001:620:8:101f::64

14


•
•
CoAP Response
• Piggybacked response Type: ACKNOWLEDGE Options:
Code: 2.05 - Content-Type: 50
• Mag-Age Payload: {temp: 21.5} - Mag-Age: 60

Constrained Network
Proxy
170.1.52.200 2001:620:8:35C1::xxx

5683
Room B
80

2001:620:8:101f::64

15


•
•
Http Response
• CoAP-HTTP mapping Status-Code: 200 OK
• Cache-Control Cache-Control: max-age=60
Content-Type: application/json; charset=utf-8
• Content-Type
Body: {temp: 21.5}

Constrained Network
Proxy
170.1.52.200 2001:620:8:35C1::xxx

5683
Room B
80

2001:620:8:101f::64

16


•
•
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

19


•
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

22


•
•
integration (Californium architecture) •
•
• Layered architecture Resources
• Chain of Responsibility Resource
• Single thread model
• Limited to clients and servers Endpoint
• Pitfalls
• Synchronized responses
Abstractions
• Blocking UDP thread
Communicator
• Missing client abstraction
• Missing server abstraction
TransferLayer

Variable Layers

Layers ⟳ UDPLayer

23


•
•
integration (proxying) •
•
• Encapsulations Resources
• Forwarding resources (client) Resource
• Stacks (servers)

• Multi-thread model CoAP Resource HTTP Resource
• Concurrent responses
• Resource thread-safeness ⟳⟳⟳ Proxy Endpoint
• Non-blocking UDP thread

• Communicator Abstractions
• Two message flows
• Thread-safeness Proxy Communicator
• Endpoint
• Avoid HTTP in CoAP servers ⟳⟳⟳ HTTP Stack CoAP Stack ⟳
• Encapsulate cache
Servers

25


•
•
final architecture

Resources HTTP Client
HTTP Translator
CoAP Client
Resource
Cache

Abstractions Proxy Endpoint

Proxy Communicator

HTTP Translator
CoAP Stack
HTTP Stack
Servers
26


•
4. Evaluation: •
•
performance assessment •
•
400
100 requests/s

Average Round Trip Time (ms)
• Emulation
350 200 requests/s
• Proxy JVM limitation
400 requests/s
• CoAP Server Virtualization 300
600 requests/s
• Test client 250
• Pre-compiled requests
• Random distribution of requests 200
• Normal distribution of resources
150
• Average of several “runs”

• Produced data 100

• Raw RTT distributions
50
• RTT/throughput trends
• CDF for RTT 0
0 200 400 600 800 1000
Request number

27


•
4. Evaluation: •
•
performance assessment (CoAP-to-HTTP proxying)
350
Tests w/o caching
Average RTT (ms)

300
250 Tests w/ caching
200
150
100
50
0
0 50 100 150 200 250 300 350 400 450
Produced throughput (Kbit/s)

1
Cumulative Density F.

0.8
0.6
0.4
100 Kbit/s w/ cache 400 Kbit/s w/ cache
0.2
100 Kbit/s w/o cache 400 Kbit/s w/o cache
0
0 100 200 300 400 500 600
Average Round Trip Time (ms)

28


•
4. Evaluation: •
•
hybrid mashup •
•
Paraimpu control Panel HTTP to CoAP

Twits containing temperatures

33


•
•
Conclusions •
•
•
CoAP draft evolution
• Smart city 7
• Mashup as leading paradigm in the WoT K Lines added
• Scalability through physical locality
6 K Unchanged Lines
• Chains of proxies

• Lesson learnt 5
• Design for extensibility
• Interoperability through standards 4
• Cheat sheet for overlapping specifications
3
• Future work
• Standardization process
2
• Intercepting proxy
• Secure proxy (HTTPS-CoAPS mapping)
1

0

35


Thank you for the attention

36

Thesis Presentation: Web-Integrated Smart City Infrastructure

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