PPWEB: A Peer-to-Peer Approach for Web Surfing On the Go Ling-Jyh Chen, Ting-Kai Huang Institute of Information Science, Academia Sinica, Taiwan Guang Yang Nokia Research Center, Palo Alto, US

Motivation Web surfing is part of our life. How can we surf the Web when we cannot directly access the web pages? No connections Censorship Mobile devices are hugely popular. How can we browse the Web when we are on the go? Cellular Wi-Fi Hotspots

Previous Solutions Offline-based approaches Cache-based approaches Gnu Wget Wwwoffle Well-known web browsers Cache-based approaches Push based (Aalto ‘04, Costa-Montenegro ‘02, Spangler ‘97) Pull based (Jiang ’98a, Jiang ’98b, Padmanabhan ‘96) Infostation-based approaches Mobile Hotspots (Ho ‘04) Thedu (Balasubramanian ‘07) offline-based的方法，主要是事先將網頁下載至本地的存儲空間中 暫存器輔助類的方法則會去去猜測使用者可能會想要瀏覽的網頁，並且由程式本身主動從網路上下載回來 業者推播(push mode)模式，如[6] [13] [23]，或者是 程式主動索取 固定式資訊站為基礎類的方法是利用架設好的資訊站來扮演網際網路和行動網路(mobile network)中間的橋樑

Previous Solutions (Drawbacks) Offline-based manually download web documents limited number of web pages Cache-based Tremendous storage overhead You still need a data plan to surf. Infostation-based Dedicated Infostations needed Single point of failure

Assumptions We Make All peers collaborate. All peers have local connectivity WiFi, Bluetooth, etc. All peers are mobile. Some peers have Internet access.

What We Propose: Scenario 1 Internet HTTP Gateway Peer: A peer who can access the Internet directly

What We Propose: Scenario 2a Gateway Peer (B) Vanilla Peer (A): Peer that cannot access Internet directly

What We Propose: Scenario 2b Vanilla Peer (A) Vanilla Peer (B)

B gets A’s request B is a GP Y N B and A are connected B has the requested web content Y N Y N Direct forwarding The request has been relayed H times B and A are connected N N Collaborative forwarding Y Y Indirect Forwarding Do nothing Request Forwarding

Direct Forwarding vs. Indirect Forwarding B has complete content =>Direct Forwarding algorithm B may only have partial content =>Indirect Forwarding algorithm Further passing the request message using Request Forwarding algorithm

Cooperative Forwarding Algorithm Increase the packet delivery ratio and decrease the request response time HEC-PF Hybrid Erasure Coding Algorithm (H-EC) Probabilistic Forwarding Algorithm Erasure codes increase error tolerance. Extra caching increases hit ratio in the future (esp. for popular pages).

Evaluations Evaluate the performance of PPWEB scheme against Mobile Hotspots scheme Service ratio and traffic overhead DTNSIM: Java-based simulator Real wireless traces UCSD (campus trace) iMote (Infocom ‘05)

The Properties of two network scenarios Trace Name iMote UCSD Device PDA Network Type Bluetooth WiFi Duration (days) 3 77 Devices Participating 274 273 Number of Contacts 28,217 195,364 Avg # Contacts/pair/day 0.25148 0.06834

Parameter Settings Number of VPs: Number of requests: 20% of the other peers Number of requests: first 10% of simulation time with a Poisson rate of 1800 sec/request. The HTTP requests: top 500 requested web pages, campus proxy server of NTU, Apr.-Sept. 2006. Traffic: iMote 15 request 44 peers UCSD 370request 44 peers

Scenario 1: UCSD γ= 20% γ= 60% iMote之所以會讓improve變大，是因為imote的internal node 和external node的差別。 Ucsd的每個node的contact次數類次的話，就不會有這樣的問題。

Scenario 2: iMote γ= 20% γ= 60% 坐標的說明 一波一波是因為會議的作息 R愈大，service ratio隨之成長

Traffic Overhead γ PPWeb Mobile Hotspots Normalized Overhead iMote 20% 4,298 1,423 3.02 40% 3,986 1,591 2.50 60% 3,938 1,694 2.15 UCSD 211,604 65,723 3.22 189,702 64,858 2.92 163,883 62,663 2.62 Replication factor of erasure coding = 2 Aggressive forwarding phase of the HEC-PF: make one more copy The upper bound of the traffic overhead : 2*2=4

Summary PPWEB is a peer-to-peer solution to enable mobile web surfing. No constant Internet access is required. No dedicated servers are required. It implements a Collaborative Forwarding algorithm that takes advantage of opportunistic encounters.

Thank You! 20