liulixiang(@liulixiang.info)仅供参考

GTPP: 结构化 DHT网络上的棱台结构

GTPP: General Truncated Pyramid Peer-to-Peer Architecture over Structured DHT Network

Paper InfoGTPP: General Truncated Pyramid Peer-to-Peer

Architecture over Structured DHT NetworksAuthors: Zhonghong Ou, Erkki Harjula, Timo Koskela,

Mika YlianttilaMobile Network Application, August 2009

作者关于GTPP的其它论文 :Ou Z, Harjula E, Ylianttila M (2008) GTPP: General

truncated pyramid architecture over P2PSIP networks. The International Conference on Mobile Technology, Applications & Systems 2008 (Mobility Conference), 10-12 September, Ilan, Taiwan

Ou Z, Zhou J, Harjula E, Ylianttila M (2009) Truncated pyramid peer-to-peer architecture with vertical tunneling model. The Fourth International Workshop on Dependable and Sustainable Peer-to-Peer Systems (DAS-P2P 2009) on CCNC 2009. 10–13, January, in Las Vegas, Nevada.

AgendaIntroduction and MotivationRelated work and taxonomyGTPP architecturePerformance analysis and result analysisDiscussion and future workConclusion

Introduction典型的DHT结构的 P2P查找服务实现 :

Chord, CAN, Pastry, Tapestry, etc.

Key point of DHT based P2P overlay lookup algorithms: they firstly define a metric for the distance of the peer-

peer and pee-key, and then store the key-value pair in the “closest” peer

according to the distance metric defined,get the value of the key in a logarithmic number of hops

扁平结构 (flat architecture): peers of the overlay have the same functionalities and load in routing and maintenance, etc.

Motivation of Hierarchy ArchitectureHierarchical architecture almost always

accompanies the large-scale, complex systemsintra-AS routing(RIP/OSPF) and inter-AS

routing(BGP)

Notable advantages of hierarchical DHT proved by the previous work：fault isolation and securityeffective caching and bandwidth utilizationdeduction in lookup hops and latencyadaptation to the underlying physical networkproviding administration control and autonomymore adaptable to mobile environment

Motivation of GTPP对于分层，原来只关注两层结构 (two-tier

hierarchy)

增加分层是否会带来性能和功能上提升？

层次结构 P2P的典型特点

相关工作基于分层非结构化 P2P的应用： KaZaA 、 Gnutella 、

CAP等super-nodessuper-peer ， non-super-peer

基于DHT的层次结构 P2PH-HA(Horizontal-Hierarchical Architecture水平分

层 )VA(Vertical-Hierarchical Architecture垂直分层 )

FV-HA(Fully全垂直分层结构 )PV-HA(Partially部分垂直分层结构 )

多层：GTPP

分层 P2P系统的分类

GTPPbuilt on the basic functionalities of the

hierarchical DHT :all of the tires utilize the same basic

DHT(Chord)

no optimizationanycast, multicast, mesh-connection, single-

connection, etc.

GTPP结构：组成peerSSOs(sub-sub-overlays)

结构可变（可优化），这里使用 Chord不同 SSO之间不能进行直接查询，需要通过上层的

sub-overlay做代理（ proxy）gateway super-peer

除了顶层 SSO外都有一个 super-peer

GTPP Architecture

Service Lookup Procedure1 、初始 peer发送一个查询请求至它的 gateway

super-peer，然后该 gateway super-peer转发该请求到其自身的 gateway super-peer ，……如此重复知道请求到达顶层 SSO；

2 、在顶层 SSO 的 gateway super-peer处理该请求在本地 SSO使用 DHT算法进行查找，如果找到而来对应资源则返回应答至初始 peer，否则将该请求转发到最接近该资源的下一层 SSO；

3 、以下每一层 SSO重复步骤 2 的操作，直到最底层的 SSO；

4 、如果再最底层 SSO还未查找到相关资源，则按照与查询相反的路径返回失败信息。

Performance Analysis（略）lookup hop count查询跳数

lookup latency查询延迟

traffic distribution(流量分布：查询、维护、更新 )lookupmaintenancerepublish

Performance Analysislookup hop count

n does not affect the expected lookup hop countGTPP has a slightly higher amount of lookup hop countfurther decreased by caching the top-most gateway

super-peerlookup routing latency

the expected lookup routing latency decreases as the value of n increases(the more tiers GTPP has, the shorter latency it can achieve)

2-4 tiers are optimal(can not achieve even better performance just by add the overlay depth)

traffic distribution single peer: GTPP has a clearer and more reasonable way than

flat architecture and 2 to 3 tiers are optimal to keep this benefit

total traffic: significantly increases when depth from 2 to 3 and then significantly increase when the depth varies from 3 to 4

Performance Analysis(Summary)GTPP as a generalized version of PV-HA, has

significantly decreased lookup latency though the expected lookup hop count is slightly larger than flat architecture.

GTPP also shows its advantage in heterogeneous environments as it has a clear and distinct traffic distribution among the peers from different tier of sub-overlay.

As for the maintenance traffic, GTPP still has its advantage compared to flat architecture.

From the perspective of total traffic of the whole overlay network, GTPP has slightly larger traffic than flat architecture. However, when the depth of GTPP is 2 or 3, the added total traffic is still tolerable.

In conclusion, two to three hierarchical tiers are the most suitable for GTPP in most cases.

Result Analysis & Simulate Result( 略 )lookup hop countlookup routing latencytraffic distribution of each single peer from

different tier of sub-overlaytotal traffic of the whole overlay network

Discussion and Future workContent cachingIterative routing vs. Recursive routingChurn effect

Future workperformance of GTPP in the presence of

churnoptimal operating point of the whole

hierarchical overlay networkchange assumption, more realistic

Conclusion: GTPP vs. flat architecture稍多（ slightly）的查询跳数（接近扁平结构）查询延迟显著（ significantly）减少稍多但是更清晰、更合理的流量分布，相对较少

（ slightly）的维护开销对于 GTPP来说 2-3层是最合适的