Personal Grid Running at the Edge of Internet *

Transcription

1 Personal Grid Running at the Edge of Internet * Bingchen Li 1, Wei Li 1, Zhiwei Xu 1 1 Institute of Computing Technology, Chinese Academy of Sciences, Beijing, , China {libingchen, liwei, zxu}@ict.ac.cn Web: Abstract. The common Grid systems are running on the backbone of Internet. These high performance computing environment provide a high scalable, high reconstructive Grid services in a C/S mode, while more and more Grid applications require a P2P liked infrastructure for personal intercommunication, resources sharing and collaborative work. Personal Grid, we proposed in VEGA Grid project of ICT, would establish such kind of platform to facilitate the messages transmitting and resources sharing for the end Grid users who are using Grid at the edge of the Internet. The core protocol of Personal Grid gives attentions to security, network bandwidth usage and real time requirements. The Personal Grid running environment is very similar to P2P system; it inherits some advantages of P2P system and enhances some parts for Grid usage such as security protection of mandatory access control. 1 Introduction The Grid system deployed in the backbone of Internet provides a high performance, high scalability and high manageable computing environment, while the users of Grid are at the edge of network. The successful experiments of Peer-to-Peer systems indicate that combining the desktop PCs can also establish a spectacular super computer, whose performance is even much higher than any super computer of the top 500 supercomputers. When we mention the word of Grid, the direct ideal in our mind is a C/S structured system; we also do research on the behavior of servers cooperation in a S/S mode, while care less about the C/C or P2P usage of Grid although a great deal of applications occur pervasively around us. The Personal Grid proposed by us aims at establish a Peer-to-Peer platform for Grid end users who are at the edge of network. Such platform facilitates the communication applications of grid participators and shares the desktop resources at the edge of network. In this article we will not only * This work is supported in part by the National Natural Science Foundation of China (Grant No ), the China Ministry of Science and Technology 863 Program (Grant No. 2002AA104310), and the Chinese Academy of Sciences Oversea Distinguished Scholars Fund (Grant No ).

2 discuss some interesting topics on our research of personal grid, but also illustrate and evaluate the communication platform we implemented firstly in our test-bed. 2 Requirements We list the requirements of Personal Grid in the following two sections. 2.1 Personal intercommunication requirement Mobile phone is substituting the status of fixed phone and being treated as common communication equipment in this century. The booming industry brings considerable society benefit. It presents strong needs for intercommunication in daily society actions. The same phenomena take place in computer world. Prevalence of computer network enables Grid System to be born and widely used. The Grid system connects resources and applications not only in physical layer but also in semantic layer. These connections still rest on the traditional network service pattern client-to-server or server-to-server. The research result of collaborative work indicates that more and more Grid applications require personal intercommunication. Commercial communication software have existed for a long time since the born of computer network such as ICQ and NetMeeting. These systems are not standard-opened and machineindependent, and not satisfied with the OGSA request. The Access Grid establishes a collaborative work environment for group-to-group requirement but not for individual requirement. The Personal Grid of VEGA Grid project will fill the blank of Grid users intercommunication in a peer-to-peer way. The difference between Personal Grid and common Grid is that it is not a server-centric system but a user-centric system and the object of Personal Grid is not resource but human. 2.2 Desktop resources sharing requirement From the surprising result of SETI@Home project and some P2P file sharing system such as Kazaa and BearShare, we found that the desktop resources located at the edge of the Internet is a huge mine for Grid application, while interesting research field of Grid system is still in large-scale storage sharing such as Data Grid. The desktop resource sharing is ignored by public eyes in Grid. In the view of Personal Grid, it is a challenge to integrate distributed, heterogeneous, less available desktop resources into Global Grid system. The key issue of desktop resources sharing is availability. The services such as file sharing service and CPU circles sharing service are not in 24*7 mode. Fault tolerance and redundancy are widely used in this area.

3 3 Relation work From the previous discuss about the aims of Personal Grid, We find that the running environment and the key issues of Personal Grid are quite similar to P2P system. The Personal Grid inherits some advantages of P2P system and enhances some components for Grid usage. We list some features that we inherited from P2P system and some special requirement of Grid usage. Scalability Self-Organization Cost of ownership Fault Resilience Ad-Hoc Connectivity Interoperability Special requirement of Grid system: 1. Authentication The organizer of Personal Grid is Grid Community. It provides authentication service for community members. 2. Delegation To establish intercommunication between different Grid Communities, the communities act the role of service delegation. 3. Enhanced Security P2P system has security protection mechanism for every communication channel, but it is not satisfied for Grid usage, because the real-name user is the main part while anonymous user is only allowed in a limited field controlled by mandatory access control of Grid Community. Comparing Personal Grid with P2P system we find these differences between them: firstly, Personal Grid depends on the services provided by Grid Community and also be controlled by it while the main aim of P2P system is to minimize the role of server; secondly, the anonymity is the main characteristic of P2P system while Grid system requires real-name authentication for security consideration; thirdly, Personal Grid provides a platform for Grid usage and supports developing work based on this architecture. But the word of P2P means a connection mode only, they are not based on a standard protocol or same architecture. 4 The architecture of Personal Grid 4.2 The platform of Personal Grid The Personal Grid platform includes two main parts: intercommunication and sharing. It is based on the Grid Community Service. The architecture is as following figure:

4 Files Media Mail Message CPU Circles Intercommunity and resources sharing platform Community Service Grid Community Community Service Grid Community Fig. 1 The architecture of Personal Grid This platform considers three factors of data stream. Security requirement. For some kinds of Personal Grid application such as talk and Grid mail, message contents need to be protected. In Personal Grid system, we use public key authentication system to protect the communication channel. Every client keeps the public key of Grid Community, and the Community Server also keeps the client s public key. Comparing to P2P system, no listen port is needed in Personal Grid client side. Every session between two clients uses a random and temporary port. Real-time requirement. Real-time media stream is a main part of intercommunication. Its network bandwidth occupation rate is higher than that of any other protocol. For home and office usage, RTP protocol based on UDP is used in unicast and multicast mode. In Internet environment, another RTP protocol adaptor, which is based on TCP protocol, has been used because of proxy service of Grid Communication. Response-time requirement. Large quantity data transmission through Grid Community server is unreasonable, but the content sharing is dominated by the mandatory access control deployed on the server side. To balance these two requirements, in our implementation, the server controls the control stream instead of data stream, which runs in a P2P mode. 4.2 The protocol stack of Personal Grid

5 As we mentioned above, the platform of Personal Grid includes intercommunication and resources sharing. In the resources sharing platform, the protocol works in an order-preserving mode. The two recognizable ends keep the session semantic. The resources sharing mechanism of Personal Grid is a three-dimension resources space. The first dimension is resource type, the second is the items of this type and the last dimension is reserved for special usage of individual resources such as access control. The following picture illustrates a desktop resources sharing hierarchy under Personal Grid platform. Resources Sharing Platform Files Camera Fig. 2 Resources sharing in Personal Grid MyFile1 MyFile2 Vfw: 1 Access List Empty Boolean Used In the intercommunication platform, the input and output data are in an out-oforder mode because of the indetermination messages incoming sequence. The following figure illustrates the protocol stack of input and output stream: Intercommunication Platform ID1 ID2 ID3 ID4 Input Stream Deliver Timer1 Timer2 Timer3 Timer4 Waiting List Fig. 3 The protocol stack Dialog Talk Message Grid Mail Resisted Application Incoming packages Stack Output Stream Package 1 Package 2 Package N Output Stack Synchronized sequence

6 The output sequence is a synchronized array. The sending process of every package is atomic. The server side processes data control package only because of the requirement of response time. The input stream has a more complex structure than that of the output stream. It works in a group of threads and a wait list. Each registered application launches up a thread, each thread contains a vector of running items. There are two kinds of incoming packages delivered by this stream; the incoming messages and responses from the server. If the package type is incoming message, the stream distributes it to the registered application thread; otherwise, it wakes up the wait object in the wait list by its unique ID. For example, when UserA send a dialog request to UserB, he builds an invite form, sends it to the output stream and gets a message ID from system time call. A wait object is inserted into input stream wait list and the timer is set to 30 seconds for waiting. The community server receives this package and distributes the content to UserB. Community server will return processing result (success or failure) to the sender. 5 Implementation of Personal Grid 5.1 Grid Community and its service Grid Community is the basic Personal Grid organization unit in VEGA Grid project. It likes hub for each client. The control stream and messages are dominated by the hub, but the data streams such as media stream and file data block are transmitted in P2P mode. The subjects of Personal Grid are community users. We define the user identity as following format: user@community, for example Darwin@ict.ac.cn. The resources locations such as files are defined as following format: Pgfile://user@community/dir/dirs/filename. The Community resolves the real location of a user. The file owner resolves the subdirectories. The basic community services includes: 1. Authorization Personal Grid is a real-name world. The services of community provides to assured users, although some public information such as advertisement is opened for anonymous user. 2. Delegation Messages and data transmitting cross communities require delegation service. The intercommunication between Grid Communities comprises two layers of trust relationship: first, the user is authorized by his community; second, his community is trusted by the target community. If these two conditions are satisfied, the target community can accept the messages coming from the user. 3. Proxy The following picture illustrates why the proxy services are so important in the Personal Grid environment.

7 Fig. 4 Various nodes reside at the edge of Internet At the edge of Internet, so many computers reside behind a firewall or NAT gateway server. An important work in P2P world is to establish available connection through some relay nodes. The Grid Community performs the relay work in Personal Grid. Another issue is that the server would be the bottleneck of the whole system. To decrease the data communication load, two orient-opposite connection attempts are performed at the beginning. The extreme instance is that all nodes are behind different NAT gateways or firewalls. 4. Grid mail and message. When some broadcast messages and mails, the receiver may not be online, this service storages the content for receiver. This is the only offline service in Personal Grid. 5.2 Applications In the test-bed of Personal Grid, we implemented talk, message, visual dialog, and media presenter based on the communication platform. File sharing is the main application in our resources sharing platform. Compare to commercial software of instant message, videoconference and Videoon-Demand, our intercommunication platform realized all applications working under an opened standard protocol. It has no compatible problem, Personal Grid user can select his or her favorite applications even develop a new application on our platform. The following pictures illustrates our intercommunication tools of our test-bed: Picture 1. The Visual dialog of Personal Grid

8 Picture.2 The Personal Grid client app Picture. 3 Chat of Personal Grid 6 Conclusion and future work Personal Grid as a part of our VEGA Grid project introduces some P2P advantages into Grid system for the first time, and solved intercommunication and resources sharing among Grid end users who resided at the edge of Internet successfully. These two platforms of Personal Grid not only realized the common requirement of communication requirement, but also enabled developing work. More applications will be developed and deployed on demand of intercommunication and resources sharing. In the future we will improve the file and device sharing mechanism for other Grid applications of VEGA Grid project. The stream media tools will be import to GSML tool suit. 7. References 1. Z. Xu and W. Li Research on Vega Grid Architecture, Journal of Computer Research and Development Vol 39, No 8, pp A. Reinefeld, F. Schintke Concepts and Technologies for a Worldwide Grid Infrastructure, Euro-Par 2002 Parallel Processing, Springer LNCS 2400, pp D. S. Milojicic, V. Kalogeraki, R. Lukose Peer-to-Peer Computing, HP Laboratories Palo Alto HPL March 8 th, I. Foster, C. Kesselman, S. Tuecke The Anatomy of the Grid Enabling Scalable Virtual Organizations, International of High Performance Computing Applications, 2001, 15(3): pp I. Foster, C. Kesselman, J. M. Nick, S. Tuecke, The Physiology of the Grid An Open Grid Services Architecture for Distributed Systems Integration. Grid Service Infrastructure WG, Global Grid Forum, June 22, J. Apgar, A. Grimshaw, S. Harris, M. Humphrey, A. Nguyen-Tuong, Secure Grid Naming Protocol (SGNP): Draft Specification for Review and Comment, Global Grid Forum, 5 February L. Childers, T. Disz, R. Olson, Access Grid: Immersive Group-to-Group Collaborative Visualization Computer Science Department University of Chicago 8. SETI@Home current total statistics,