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Motivation: Why Unstructured?

Motivation: Why Unstructured?. Not all searches for user-IDs search by last name, first name Find a relay for media session by AS number, locality etc (DHT sol: ReDiR – effectively a kludge) Key word searches (DHT sol: inverted index – does not scale)

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Motivation: Why Unstructured?

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  1. Motivation: Why Unstructured? • Not all searches for user-IDs • search by last name, first name • Find a relay for media session • by AS number, locality etc (DHT sol: ReDiR – effectively a kludge) • Key word searches (DHT sol: inverted index – does not scale) • Range searches (DHT sol: prefix hash trees – scalable?) • Find all podcasts in New York, in my neighborhood • Random walks have been implemented on top of DHTs (useful to find overlays) • Debunking some myths about structured and unstructured overlayshttp://research.microsoft.com/~antr/MS/myths.pdf • Cannot dispense all research in unstructured systems

  2. Unstructured P2P Networks • Differences from DHTs • Resource-ID • Limited flooding (parallel requests – typically iterative) • Explicit load balancing • need information about other nodes link capacity, machine characteristics • Routing • cannot route based on peer-IDs • Common mechanisms between DHT and unstructured overlays • Connection management • Loop detection • Security • NAT traversal • Bootstrap

  3. Unstructured and RELOAD • Routing mechanisms • symmetric routing • works in unstructured • copies of same request can arrive at an intermediate node (flooding) • disambiguate using Via list? • iterative routing • need more than one peer in response • the next hop information should contain machine / link characteristics • client routing – see next slide

  4. Chord peer-id=x SIP=sipX peer-id=y SIP=sipy • STORE • H(sipY) and destination list X-Y on • FETCH • DHT 1) FETCH( H(sipY) ) 2) FETCH( X ) • unstructured? client peer-id=z

  5. Unstructured and RELOAD • Explicit load balancing • Peers need information about the ‘capacity’ of other peers and ‘size’ of the resources they are storing before issuing a STORE request • capacity: link capacity, memory, CPU utilization, user activity • Do not have to define a priori. Ensure that encoding is flexible enough to support it for a particular unstructured overlay. • Ability to define nested objects

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