Brocade: Landmark Routing on Overlay Networks

1
Brocade Landmark Routing
on Overlay Networks

• To P2P or not to P2P?
• http//www.cs.berkeley.edu/duan/prjs/cs262/
• CS262A Fall 2001
• Yitao Duan and Ling Huang
• duan_at_cs.berkeley.edu, hlion_at_newton.berkeley.edu

2
Motivation

• Problems with existing P2P Network
• Constrained by the theoretical approach adopted,
  nodes are treated uniformly1, 2, 3, 4
• Routing algorithms are decoupled from underlying
  topology and node capability
• Result inefficient routing
• Reality Nodes are not born equal
• Bandwidth, Connectivity, Storage, Processing
  Power.
• Administrative Constraints

3
Brocade Discrimination Justified

• A philosophy A system is more efficient when it
  is organized e.g., IP routing on Internet
• Respect the differences and take advantage of
  those that are more powerful Supernodes!
• Fast/well-connected/situated near network access
  points
• Supernodes have better knowledge of underlying
  network characteristics. Benefit from
  aggregation.
• Construct a hierarchy out of flat network

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Brocade Architecture
5

• Overlay nodes are grouped by their supernodes
  Cover Set
• Supernodes treat their overlay nodes as objects
  that they possess
• Routing on Brocade gt Object Location. Use your
  favorite
• mechanism Tapestry1, CAN3, Chord2,
  Pastry4
• Message filtering only send inter-domain
  messages to Brocade.

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Case Study - Brocade On Tapestry

• Tapestry A novel wide-area fault-tolerant
  location and routing infrastructure1
• Construction
• Gateway routers or machines close by as
  supernodes
• Existing connections among supernodes as Brocade
  links
• Routing object location Tapestry style
• Each supernode advertises the IDs of overlay
  nodes in its cover set as IDs of objects it
  stores.
• Destinations supernode can be found using
  Tapestrys object location mechanism
• Remaining issue How to get onto Brocade?

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Get onto the Super Highway

• Naïve Brocade Tapestry routing unchanged.
  Message gets onto the Brocade overlay if a
  supernode is encountered on its route.
• Advantage simple, no modification to ordinary
  nodes.
• Disadvantage possibility of hitting a supernode
  in Tapestry routing small.
• IP Snooping Brocade Supernodes snoop IP packets
  to intercept Tapestry messages.
• Advantage
• No modification to ordinary nodes.
• High possibility of encountering supernodes
  because supernodes are situated near the edge of
  local networks.
• Disadvantage Difficult to implement

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• Directed Brocade Each overlay node keep info
  about
• its supernode and decides by its own whether
  to send a
• message to supernode directly.
• Feasible only local information required
• Decision Engine

• A small cache storing most frequently used nodes
  in its cover set will do the trick.
• Query locality will make hit rate high
• Consequences of mistakes arent expensive

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Simulation Results
Fig 1. Hops Based RDP
Fig 2. Aggregate bandwidth used
per message
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Optimizing Object Location on Brocade

• Routing latency could be high if latencies on
  Brocade links are high and object
• location on Brocade is not optimized(Fig 3)
• Optimization Bloom Filter - Membership query
  and group ID problem

Fig 3. Weighted latency RDP w/o
optimization Fig 4. Weighted latency RDP with
Bloom Filter Brocade link latency/Ordinary link
latency 8 1
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Conclusion and Future work

• Brocade powerful idea that can achieve near
  optimal performance
• General enough to be applied to other (P2P)
  networks
• Future research
• Study the effect of different supernodes
  selection and distribution
• Further optimization of object location on
  Brocade overlay
• Latent Brocade
• Brocade benefits from aggregation of info
• Bias some nodes in the network so they will be
  favored by others while selecting route - an
  implicit Brocade

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References

• 1 ZHAO, B. Y., KUBIATOWICZ, J. D., AND JOSEPH,
  A. D. Tapestry An infrastructure for
  fault-tolerant wide-area location and routing.
  Tech. Rep. UCB/CSD-01-1141, University of
  California at Berkeley, Computer Science
  Division, April 2001.
• 2 STOICA, I., MORRIS, R., KARGER, D.,
  KAASHOEK, M. F., AND BALAKRISHNAN, H. Chord A
  scalable peer-to-peer lookup service for internet
  applications. In Proceedings of SIGCOMM
  (August2001), ACM.
• 3 RATNASAMY, S., FRANCIS, P., HANDLEY, M.,
  KARP, R., AND SCHENKER, S. A scalable
  content-addressable network. In Proceedings of
  SIGCOMM (August 2001), ACM.
• 4 ROWSTRON, A., AND DRUSCHEL, P. Pastry
  Scalable, distributed object location and routing
  for large-scale peer-to-peer systems. In
  Proceedings of IFIP/ACM Middleware 2001 (November
  2001).
• 5 TSUCHIYA, P. F. The landmark hierarchy A new
  hierarchy for routing in very large networks.
  Computer Communication Review 18, 4 (August
  1988), 3542.