Brocade Landmark Routing on Overlay Networks To P
Brocade: Landmark Routing on Overlay Networks To P 2 P or not to P 2 P? http: //www. cs. berkeley. edu/~duan/prjs/cs 262/ CS 262 A Fall 2001 Yitao Duan and Ling Huang duan@cs. berkeley. edu, hlion@newton. berkeley. edu
Motivation • Problems with existing P 2 P Network – – – • Constrained by theoretical approach adopted, nodes are treated uniformly[1, 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
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
Brocade Architecture Brocade Original Route Brocade Route AS-3 AS-1 S D AS-2 P 2 P Network
• Overlay nodes are grouped by their supernodes – Cover Set • Supernodes treat their overlay nodes as objects that they possess • Routing on Brocade => Object Location. Use your favorite mechanism: Tapestry[1], CAN[3], Chord[2], Pastry[4] … • Message filtering: only send inter-domain messages to Brocade.
Case Study - Brocade On Tapestry • Tapestry: A novel wide-area fault-tolerant location and routing infrastructure[1] • 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”. – Destination’s supernode can be found using Tapestry’s object location mechanism • Remaining issue: How to get onto Brocade?
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
• 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. Destination is in my cover set? No Send to supernode Yes Ordinary Tapestry Routing • Query locality will make hit rate high • Consequences of mistakes aren’t expensive
Simulation Results Fig 1. Hops Based RDP Fig 2. Aggregate bandwidth used per message
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
Conclusion and Future work • Brocade: powerful idea that can achieve near optimal performance • General enough to be applied to other (P 2 P) 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
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 (August 2001), 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), 35– 42.
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