Cloud Computing Concepts - Peer to peer systems- Napster - Gnutella
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The document outlines the evolution and architecture of peer-to-peer (P2P) systems, highlighting significant examples such as Napster and Gnutella. It discusses the operational mechanics of these systems, including file sharing methods, server roles, and challenges faced like congestion and copyright issues. Additionally, it mentions advancements toward more structured P2P systems like Chord, aiming to improve efficiency and scalability.
![P2P Systems: Lecture A : Introduction2
• [6/99] Shawn Fanning (freshman Northeastern University) releases
Napster online music service
• [12/99] RIAA sues Napster, asking $100K per download
• [3/00] 25% University of Wisconsin traffic Napster, many universities ban it
• [00] 60M users
• [2/01] US Federal Appeals Court: users violating copyright laws, Napster is abetting this
• [9/01] Napster decides to run paid service, pay % to songwriters and music companies
• [Today] Napster protocol is open, people free to develop OpenNap clients and servers
http://opennap.sourceforge.net
• Gnutella: http://www.limewire.com (deprecated)
• Peer-to-peer working groups: http://p2p.internet2.edu](https://image.slidesharecdn.com/p2psystems-180211085905/85/Cloud-Computing-Concepts-Peer-to-peer-systems-Napster-Gnutella-3-320.jpg)
![• Eliminate the servers
• Client machines search and retrieve amongst
themselves
• Clients act as servers too, called servents
• [3/00] release by AOL, immediately withdrawn, but 88K users by 3/03
• Original design underwent several modifications
P2P Systems: Lecture C : Gnutella10](https://image.slidesharecdn.com/p2psystems-180211085905/85/Cloud-Computing-Concepts-Peer-to-peer-systems-Napster-Gnutella-13-320.jpg)
Cloud Computing Concepts - Peer to peer systems- Napster - Gnutella
- 1. Indanil Gupta (Indy) With: P2P Systems Lecture A: Introduction
- 2. P2P Systems: Lecture A : Introduction1 1-First distributed systems that seriously focused on scalability with respect to number of nodes 2-P2P techniques abound in cloud computing systems 3-Key-value stores (e.g., Cassandra, Riak, Voldemort) use Chord p2p hashing
- 3. P2P Systems: Lecture A : Introduction2 • [6/99] Shawn Fanning (freshman Northeastern University) releases Napster online music service • [12/99] RIAA sues Napster, asking $100K per download • [3/00] 25% University of Wisconsin traffic Napster, many universities ban it • [00] 60M users • [2/01] US Federal Appeals Court: users violating copyright laws, Napster is abetting this • [9/01] Napster decides to run paid service, pay % to songwriters and music companies • [Today] Napster protocol is open, people free to develop OpenNap clients and servers http://opennap.sourceforge.net • Gnutella: http://www.limewire.com (deprecated) • Peer-to-peer working groups: http://p2p.internet2.edu
- 4. P2P Systems: Lecture A : Introduction3 • Widely-deployed P2P Systems: 1. Napster 2. Gnutella 3. Fasttrack (Kazaa, Kazaalite, Grokster) 4. BitTorrent • P2P Systems with Provable Properties: 1. Chord 2. Pastry 3. Kelips
- 5. Indanil Gupta (Indy) With: P2P Systems Lecture B: Napster
- 6. P2P Systems: Lecture B : Napster4 S S S P P P P P P Store a directory, i.e., filenames with peer pointers napster.com Servers Client machines (“Peers”) Store their own files File name PennyLane.mp3 The Beatles @ 128.84.92.23:1006 Info about
- 7. Client • Connect to a Napster server • Upload list of music files that you want to share • Server maintains list of <filename, ip_address, portnum> tuples. Server stores no files. P2P Systems: Lecture B : Napster5
- 8. Client (contd.) Search • Send server keywords to search with • (Server searches its list with the keywords) • Server returns a list of hosts–<ip_address, portnum> tuples–to client • Client pings each host in the list to find transfer rates • Client fetches file from best host All communication uses TCP (Transmission Control Protocol) • Reliable and ordered networking protocol P2P Systems: Lecture B : Napster6
- 9. S S S P P P P P P napster.com Servers 2. All servers search their lists (ternary tree algorithm) 5. Download from best host 1. Query 3. Response 4. Ping candidates Client machines (“Peers”) Store their own files Store peer pointers for all files P2P Systems: Lecture B : Napster7
- 10. Can be used for any p2p system • Send an http request to well-known url for that P2P service-http://www.myp2pservice.com • Message routed (after lookup in DNS=Domain Name System) to introducer, a well known server that keeps track of some recently joined nodes in p2p system • Introducer initializes new peers’ neighbor table P2P Systems: Lecture B : Napster8
- 11. • Centralized server a source of congestion • Centralized server single point of failure • No security: plaintext messages and passwds • Napster.com declared to be responsible for users ’ copyright violation • “Indirect infringement” • Next system: Gnutella P2P Systems: Lecture B : Napster9
- 12. Indanil Gupta (Indy) With: P2P Systems Lecture C: Gnutella
- 13. • Eliminate the servers • Client machines search and retrieve amongst themselves • Clients act as servers too, called servents • [3/00] release by AOL, immediately withdrawn, but 88K users by 3/03 • Original design underwent several modifications P2P Systems: Lecture C : Gnutella10
- 14. P2P Systems: Lecture C : Gnutella11 P P P P P P P Servents (“Peers”) Connected in an overlay graph (== each link is an implicit Internet path) Also store “peer pointers” Store their own files
- 15. P2P Systems: Lecture C : Gnutella12 • Gnutella routes different messages within the overlay graph • Gnutella protocol has 5 main message types • Query (search) • QueryHit (response to query) • Ping (to probe network for other peers) • Pong (reply to ping, contains address of another peer) • Push (used to initiate file transfer) • We’ll go into the message structure and protocol now • All fields except IP address are in little-endian format • Ox12345678 stored as 0×78 in lowest address byte, then 0×56 in next higher address, and so on.
- 16. P2P Systems: Lecture C : Gnutella13 Descriptor ID Payload Descriptor TTL Hops Payload Length PayloadDescriptor Header 0 15 16 17 18 22 ID of this search transaction Type of payload 0×00 Ping 0×01 Pong 0×40 Push 0×80 Query 0×81 Queryhit Decremented at each hop, Message dropped when ttl=0 ttl_initial usually 7 to 10 Incremented at each hop Number of bytes of message following this header
- 17. P2P Systems: Lecture C : Gnutella14 Minimum speed Search criteria (keywords) Query (0×80) 0 1 Payload Format in Gnutella Query Message
- 18. P2P Systems: Lecture C : Gnutella15 Query’s flooded out, ttl-restricted, forwarded only once P P P P P P P TTL= 2
- 19. P2P Systems: Lecture C : Gnutella16 • To avoid duplicate transmissions, each peer maintains a list of recently received messages. • Query forwarded to all neighbors except peer from which received. • Each Query (identified by DescriptorID) forwarded only once. • QueryHit routed back only to peer from which Query received. with same DescriptorID. • Duplicates with same DescriptorID and Payload descriptor (msg type) are dropped. • QueryHit with DescriptorID for which Query not seen is dropped.
- 20. P2P Systems: Lecture C : Gnutella17 •Requestor chooses “best” QueryHit responder Initiates HTTP request directly to responder’s ip+port GET /get/<File Index>/<File Name>/HTTP/1.0rn Connection: Keep-Alivern Range: bytes=0-rn User-Agent: Gnutellarn rn • Responder then replies with file packets after this message: HTTP 200 OKrn Server: Gnutellarn Content-type:application/binaryrn Content-length: 1024 rn rn
- 21. P2P Systems: Lecture C : Gnutella18 HTTP is the file transfer protocol. Why? • Because it’s standard, well-debugged, and widely used. • Why the “range” field in the GET request? • To support partial file transfers. • What if responder is behind firewall that disallows incoming connections?
- 22. P2P Systems: Lecture C : Gnutella19 • Responder establishes a TCP connection at ip_address, port specified. Sends GIV <File Index>:<Servent Identifier>/<File Name>nn • Requestor then sends GET to responder (as before) and file is transferred as explained earlier • What if requestor is behind firewall too? • Gnutella gives up • Can you think of an alternative solution?
- 23. P2P Systems: Lecture C : Gnutella20 Ping (0×00) no payload Pong (0×01) Port ip_address. Num. files shared. Num. KB shared • Peers initiate Ping’s periodically • Ping’s flooded out like Query’s, Pong’s routed along reverse path like QueryHit’s • To keep neighbor lists fresh in spite of peers joining, leaving and failing
- 24. P2P Systems: Lecture C : Gnutella21 • No servers • Peers/servents maintain “neighbors,” this forms an overlay graph • Peers store their own files • Queries flooded out, ttl restricted • QueryHit (replies) reverse path routed • Supports file transfer through firewalls • Periodic ping-pong to continuously refresh neighbor lists • List size specified by user at peer: heterogeneity means some peers may have more neighbors
- 25. P2P Systems: Lecture C : Gnutella22 • Ping/Pong constituted 50% traffic • Solution: Multiplex, cache and reduce frequency of pings/pongs • Repeated searches with same keywords • Solution: Cache Query, QueryHit messages • Modem-connected hosts do not have enough bandwidth for passing Gnutella traffic • Solution: use a central server to act as proxy for such peers • Another solution: FastTrack System (soon)
- 26. P2P Systems: Lecture C : Gnutella23 • Large number of freeloaders • 70% of users in 2000 were freeloaders • Only download files, never upload own files • Flooding causes excessive traffic • Is there some way of maintaining meta-information about peers that leads to more intelligent routing? • Structured peer-to-peer systems e.g., Chord System (coming up soon)