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11 TopBT Topology-Aware BitTorrent Client Shansi Ren 1, Enhua Tan 2, Tian Luo 2, Songqing Chen 3, Lei Guo 4, Xiaodong Zhang 2 1 Microsoft Corporation 2.

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Presentation on theme: "11 TopBT Topology-Aware BitTorrent Client Shansi Ren 1, Enhua Tan 2, Tian Luo 2, Songqing Chen 3, Lei Guo 4, Xiaodong Zhang 2 1 Microsoft Corporation 2."— Presentation transcript:

1 11 TopBT Topology-Aware BitTorrent Client Shansi Ren 1, Enhua Tan 2, Tian Luo 2, Songqing Chen 3, Lei Guo 4, Xiaodong Zhang 2 1 Microsoft Corporation 2 The Ohio State University 3 George Mason University 4 Yahoo! Inc

2 Peer-to-Peer (P2P) Applications and Traffic 2 Popular P2P applications: File sharing: BitTorrent, eDonkey, eMule Voice-over-IP (VoIP): Skype Streaming media: PPLive, PPStream, UUSEE, Joost Online users –6.8 million in August 2004, 9.6 million in August 2005 (BigChampagne) –End of 2009, one BT client alone had 52 million users Traffic volume –73.8% is P2P, and 66.7% of P2P is BitTorrent (IPOQUE, 2007) Source: IPOQUE

3 Peer-to-Peer Overlay and Underlay 3 overlay underlay Logic Layer Physical Layer Lack of communication

4 P2P Overlay and Underlay Mismatch Isolated design: topology was not a design factor Heavy Internet traffic ISP shape P2P traffic due to the inefficiency caused by this mismatch Non-trivial to bridge the gap Some rely on Infrastructure Some cannot retain speed 4 CA OH NYC VA ISP AISP B ISP C ISP D

5 5 I want to share a large file 1.2 Put Torrent-File onto web server Initial Seed TrackerWeb Server 1.3 Register as peer 1.1 Create Torrent-File Torrent File - url of tracker - name: name of file - file length - piece length - file pieces BitTorrent Working Process The file creator that wants to share with others The server that hosts torrent file The server that exchanges peer information

6 6 BitTorrent Working Process Peer 1 Tracker 2.1 Request Torrent-File Web Server 2.3 Randomly send a peer set 2.2 Register as peer 2.4 Open connection 2.7 Send pieces 2.5 Handshake 2.6 Request Requesting Peer Peer n Peer i A seed peer has complete file, and non-seed peers are called leechers.

7 7 BitTorrent Working Process seed swarm leecher my node active set peer set (a)traffic volume comes from active set; (b)active set is statically sized; (c)our research focuses on peer selections for the active set. Peers in active set : unchoked Other peers are choked

8 Issues & Concerns Users want to download fast Internet Service Providers (ISPs) want to minimize generated traffic How can we reduce unnecessary Internet traffic while retaining fast downloading speed? 8 Take topology into consideration during peer selection

9 Previous Client-Based BTs and Their Limits 9 Most existing BT clients adopt a peer selection solely based on downloading rates, and do not consider peer topology: Vuze, uTorrent, BitComet, etc Generates a large amount of unnecessary traffic BitTyrant uses both downloading and uploading rates to select peers (NSDI07) Downloading speed is fast Still generates a lot of unnecessary traffic due to topology-unawareness

10 Infrastructure-Dependent Approaches and Their Limits Recent studies propose to utilize network layer information in BT peer selections for fast download time and reduced traffic: P4P proposes that ISPs provides traffic, routing, and topology information to applications (SIGCOMM08) Relies on ISPs to provide information Relies on ISPs to deploy customized interface ISPs provides information difrerent from BT optimization objectives Ono proposes to utilize Content Distribution Networks (CDNs) to find close peers (SIGCOMM08) Relies on CDNs to provide information Relies on large scale deployment of Ono clients CDN metrics different from BT optimization objectives 10 We propose to build an topology-aware and infrastructure- independent BT system called TopBT.

11 11 Outline of Talk

12 TopBT Design Considerations TopBT actively discovers peer proximities (close neighbors in underlay networks) Routing hops in Autonomous Systems (ASes) Routing hops in links TopBT monitors downloading rates of close neighbors TopBT uses a comprehensive metric that consider both routing proximities and transmission rates 12

13 TopBT System Framework 13 TopBT Components AS-hop Examiner Link-hop Examiner Rate Monitor Peer Selector File Transfer Manager Does NOT require major Internet infrastructure support Does NOT require large deployment of its same type Directly optimize downloading time and traffic

14 14 Host h2 a b b a a C A B d c c b Host h1 Intra-AS routing within AS A Intra-AS routing within AS B AS-Hop and Link-Hop Inter-AS routing between A and B Routing path can be at AS-level or link-level. TopBT discovers both AS-level and link-level path proximities. AS-hop: 1 Link-hop: 5

15 Discovering Path Proximities Standard tools for Probing Connection Paths: (TCP) Ping and Traceroute Calculating Link-Hops and Autonomous System (AS) Hops (path proximity analysis) Handling asymmetric routing paths 15

16 Probing Path with (TCP) Ping 16 destination ping resp TTL Packet initial TTL are predefined values. Link-hop examiner checks response packets TTL value. TCP Ping based on SYN/ACK or RST packets is used to explore more remote hosts. source

17 Calculating Link-Hops 17 ping probe ping results 255 UNIX 255 UNIX 128 Windows NT/2000/XP 128 Windows NT/2000/XP 64 Linux Compaq Tru64 64 Linux Compaq Tru64 32 Windows 95/98/ME 32 Windows 95/98/ME Response Time-To-Live (TTL) value 95% Internet paths Link-hops <= 30 calculated link-hop Initial TTL can be one of these typical values

18 Calculating AS Hops BGP routing tables prefix-AS mapping table traceroute probe traceroute path raw traceroute path processed traceroute path translated AS path de-duped AS path calculated distinct AS hops 18 Public servers (containing routing information) (Border Gateway Protocol) (Built offline)

19 Traceroute Probe Results * * Hop number, IP address, DNS name inr-daedalus-0.CS.Berkeley.EDU soda-cr-1-1-soda-br-6-2 vlan242.inr-202-doecev.Berkeley.EDU gigE6-0-0.inr-666-doecev.Berkeley.EDU ? ? no response from router no DNS name resolution

20 Map IP Path to AS Path * * Traceroute output: (hop number, IP) AS25 AS11423 AS3356 AS1668 AS5662 Berkeley CNN Calren Level3 AOL AS-hop: 5

21 Handling Asymmetric Traceroute Paths AS A AS B AS C AS D Autonomous System (AS) IP traffic Internet source destination Two connected hosts exchange AS-hop information! 21

22 22 Outline of Talk

23 Understanding BT Traffic 23 We use an instrumented client to collect the slice-level peer connection information once everyday for 7 days over over more than 100 Planet-Lab and residential hosts downloading from a number of torrents: NameSize (bytes)peers Game179.0M510 Music97.4M3,015 TV-show348.6M3,821 Ubuntu695.8M933 Torrent File Summary

24 Policies to Select High Quality Peers Traffic-oriented policies Policy of selecting peers in the same AS Policy of selecting peers with the lowest hops Downloading speed-oriented policies Downloading and uploading rates and their ratio TopBT: comprehensive peer selection policy 24

25 Selecting Peers in the same AS 25 Heavy-tail: a few ASes have large # of peers, while the rest have only a few peers A few studies by Karagiiannis et al. (IMC05) and Bindal et al. (ICDCS06) suggest to select peers from the same AS. Most other peers reside in different ASes. The clients own AS does not have enough peers to be selected for fast downloading in most case.

26 Selecting Peers with Lowest Hops 26 with only connected peers with all available peers (>50%) nodes: save (>15%) mean link-hops(>50%) nodes: save (>50%) mean link-hops Significant amount of network traffic can be reduced when selecting close peers to connect with. The client can select peers with the lowest link (or AS) hops Traffic reduction ratio is the difference between the current traffic and the traffic with lowest hop policy, divided by the current traffic slice avg link-hop reduction ratio

27 Downloading Time Oriented Policy 27 Related factors: downloading rate (d-rate), or reciprocal uploading rate (u-rate) Traditionally, unchoke peers with highest d-rate BitTyrant (Piatek et al. NSDI07) consider both d-rate and u-rate unchoke peers with highest d-rate/u-rate Best exploit uploading bandwidth

28 Routing Hop and Speed Relationship 28 #3000 # Downloading rates have no strong correlation with routing hops 2.d-rates and hops are widely distributed (Same hops, different speed)

29 Flash: Unchoking in the Past (1) 29 Downloading Rate (unchoke) (choke) Traditional: Vuze, uTorrent, BitComet Topology-unawareness; Traffic over-consumption

30 30 d-rate/u-rate (unchoke) (choke) BitTyrant (NSDI07) Topology-unawareness; Traffic over-consumption Flash: Unchoking in the Past (2)

31 31 (choke) (unchoke) AS-hops (AS-hops = 0) Same-AS (IMC05): Optimize for a single ISP; Users suffer Flash: Unchoking in the Past (3)

32 32 (choke) (unchoke) hops Lowest Hops (IMC05): Speed is not a priority Flash: Unchoking in the Past (4)

33 Unchoking in TopBT Downloading Rate 1/(# of Hops) (Peers Similar rates but different hops) (Peers Similar hops but different rates)

34 Unchoking in TopBT 1/(# of Hops) Worst Peers Fastest Closest (NOT the best) Best Peers: Fast & Close Downloading Rate

35 Unchoking in TopBT more than enough good peers 1/(# of Hops) Recursive partition Two fastest Two closest + Downloading Rate

36 1/(# of Hops) Downloading Rate Unchoking in TopBT no enough good peers Choose Fastest

37 37 Outline of Talk

38 Experiment Methodology We deploy native BT, BitTyrant, and TopBT clients onto 150+ Planet-Lab (PL) and residential hosts. We use a popular legal torrent that have a large number of non-PL peers. We start native BT, BitTyrant, and TopBT in random order, and repeat the experiments once everyday in 7 days. 38

39 Traffic and Download Time 39 TopBT is slight faster than BitTyrant, and both are 25% faster than native BT 30% TopBT hosts have avg AS-hop 15% less than native BT and BitTyrant TopBT has much lower avg. link-hop than native BT and BitTyrant

40 Probing Delay and Overhead 40 TypeAvgminmax TCP ping0.58 sec0.13 sec7.24 sec Traceroute40 sec18 sec122 sec Probing at background, and does not affect download time TopBT generates a peak number of ping messages in the beginning, and that number quickly drops to a few. Overall, TopBT is light-weight

41 Summary The current BT applications have over-utilized the Internet resources because of the lack of communications between the overlay and the underlay. The issue on how to reduce unnecessary Internet traffic without affecting user perceived downloading time remains challenging. TopBT can achieve fast download time, at the same time reduce Internet traffic. 41

42 42 Outline of Talk

43 Footprint V2.2 – to be relased V2.0 – released on Sep. 04th, 2009 V1.5 – released on Jan. 22nd, 2009 –on Vuze V1.1 – released on Oct. 23rd, 2008 V1.0 – released on Aug. 24th, 2008 –on LH-ABC 43

44 Third-party review TopBT runs faster than uTorrent. Plus, TopBT saves unnecessary BitTorrent traffic that clogs up the Internet, which is great for those who are bandwidth-capped by their ISP. -- sharky, 2009 ( 44

45 45 World Situation

46 Screenshot

47 Screenshot (2)

48 Try it out! Google topbt Check out the first result Homepage Other resources: Sourceforge: binary and source code Wikipedia 48

49 49 Thank you!

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