Nowadays digital libraries have become the source of information sharing across the globe in the fields of education, research and knowledge. The full usage of digital libraries will be realized only when anyone can have access to the material from any location. The advantage of multimedia is that people of all ages can understand more clearly by seeing or hearing rather than reading. Considering the exponential growth in various technologies, developing a multimedia digital library in wireless is not an impossible task. Grid computing enables the virtualization of distributed computing and data resources, such as processing network bandwidth and storage capacities to create a single system image, granting user a seamless access to vast IT capabilities. By adopting peer-to-peer (P2P) overlay networks, which are now taking a central position in information systems, the storage space problem can be solved. In this paper, we propose a framework, integrated with Grid and P2P technology to build a wireless digital library. Using this proposed framework, the digital multimedia data can be stored in a cluster built of commodity components and users can access those data from anywhere. Advantage of this framework is, using existing capital investments such as infrastructure and system storage space for storing the multimedia files, increased access to data and collaboration, and balancing workloads among different systems connected in pGrid nodes. Benchmarks used in this framework are, i) file size vs. download time, ii) simultaneous connections, iii) bandwidth utilization, iv) security, v)scalability and vi) robustness.
Keywords-grid computing; peer-to-peer networks; multimedia data; ditial library;
Introduction
Now-a-days, academic libraries contain learning resources in the form of audio and video, which form a significant collection. Time is fast catching up with the world over the traditional forms of collection development techniques and collection maintenance strategies need replacements with the upcoming trends in the profession. The traditional information service options are no longer acceptable and there is a strong demand for newer forms of services which are not so familiar to the libraries. Libraries therefore are now forced to be friendly and familiarized themselves with all relevant and current popular multimedia formats.
Interactive and multimedia learning resources are one of the most rapidly changing and exciting areas of education today. The recent entrants are computer-based training (CBTs) materials/Web-based training (WBTs) materials, especially interactive multimedia programs that run on personal computers. These new technologies offer students, teachers and researchers access to materials as never before. Multimedia can deliver large amounts of information in ways that make it manageable, approachable, and useful. The integration of multimedia programmes into libraries and classrooms promises not only to change the kinds of information available for learning, but also the way in which the learning takes place.
Multimedia data, which is a non-textual knowledge resource and it has problems not only in rendering service to users, but also with its sole dependency on a host of gadgets. The current environment surely in need of latest digital technologies for building wireless multimedia digital libraries. These newer breeds of information services offer lots of power and visibility to libraries and the user community without compromising on their quality and performance. Swift developments in media-related technologies, rapid obsolescence and their redundancy, need for time-to-time media and format migrations, resource intensive maintenance, etc. add to the complexity and complications of these collections.
A peer to peer (or P2P) computer network uses diverse connectivity between participants in a network and the cumulative bandwidth of network participants rather than conventional centralized resources where a relatively low number of servers provide the core value to a service or application. P2P networks are typically used for connecting large nodes via ad hoc connections such networks are useful for many purposes. A pure P2P network does not have the notion of clients or servers but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network. This model of network arrangement differs from the client-server model where communication is usually to and from a central server.
A Grid Computing [1, 2] is a collection of distributed resources that are shared among a group of users. It schedules and coordinates resources to offer a diverse collection of services over a network of connected devices. It has been on the focus, both in research for institution and in industry, one such area of research is storage of large bytes of data and accessing. Grid researchers are also looking at P2P architecture for data storage, as a number of such experimental systems have been proposed and are being developed [3]. The need for massive data storage is not a recent problem and with the massifyed use of large information it has become more relevant not only for large organizations but also for institutions, where they have to maintain large multimedia data files. As a result, valuable expertise has been built, resulting in the actual initiative for building the digital library using P2P and Grid Computing.
The proposed framework serves three main purposes. The first and foremost is in using the latest technology for building an architecture which will address the specific problem of massive storage for the large collection of digital and digitized items. The second purpose is to resemble not only as a traditional library, but also, to be done in accordance with the storage space available and taking into account the limited resources that can be reserved for it. The third purpose is to ease the accessibility of multimedia data from anywhere. The proposed framework uses an interface for operations like browsing, searching, sharing and also with the traditional library services. The main services that this framework is expected to assure are the storage, search, fast retrieval and preservation of digital resources in wireless and in a secured manner.
This paper is divided into 4 sections, Section 2 depicts the proposed framework for digital library, Section 3 explains the components in it, Section 4 briefs the design details, Section 5 reveals the experimental results done and the last section concludes the paper.
proposed architecture
The aim of proposed framework is to provide a manageable transparent layer for storing and accessing large amounts of multimedia data. Figure 1 depicts system architecture of the proposed framework. Framework contains 5 layers, i) Network fabric layer which lays the foundation stone for communication between heterogeneous peers / nodes, ii) P2P middleware (JXTA) layer, which controls the peers connected, iii) Grid middleware (Globus) layer, controlling the transfer of files and takes care of data storage, iv) layer 4 shows the components of proposed framework and v) layer 5 sample end user node, with services such as sharing, browsing, searching and downloading the multimedia data.
The high level interfaces (Layer 5) interact with lower abstractions (Layer 4), throughout the process. Layer 5 describes the responsibilities for providing graphical interfaces for a pGrid node formation, data storing, browsing and downloading for users. Layer 4 contains the building blocks of the proposed system, it has Digital Library Access Interface (DLAI), Integrated System Management (ISM), Data Retrieve Management (DRM) and pGrid Node Management (PNM). Layer 3 describes the interaction done by the grid middleware[4, 5] interfaces with proposed framework components (Layer 4) for downloading the multimedia files, i.e. transport and data storage, Layer 2 using P2P middleware which collects, connects and maintains all pGrid nodes in the network. Layer 1 form the network communication between heterogeneous peers.
Figure 1: System Architecture
Layer 3 plays a vital role in the proposed framework and it incorporates the grid architecture in two ways: transfer and data storage. Transfer of multimedia data among pGrid nodes is done using UDT protocol. UDT is a UDP-based approach and is accounted to be the only UDP-based protocol that applies a congestion control algorithm targeting shared networks. It is an emerging application level protocol with affirm for user configurable control algorithms and extended powerful APIs. UDT is a transport protocol with its acquired reliability control and flow/congestion control constructed above UDP. UDT allows both reliable data streaming service quite similar to TCP and partial reliable messaging. Applications use UDT socket to transfer their data, which is passed to the UDP socket. Figure 2 shows that UDT is in the application layer above UDP. Application exchanges its data through UDT socket, which then uses UDP socket to send or receive the data. Memory copy is bypassed between UDT socket and UDP socket, in order to reduce processing time. Application can also provide a customized control system (CC).
Figure 2: UDT in the Layer Architecture.
The proposed framework uses P2P and make use of P2P middleware called Juxtapose or JXTA, which is a direct network computing platform invented for Peer-to-Peer (P2P) computing by the way of providing the basic building blocks and services required to enable the JXTA protocols regularize the manner in which peers: i) discover one another, ii) self-organize into peer groups, iii) advertise and discover network resources and iv) monitor one another. JXTA is an open-source behavior to develop and implement a set of traditional peer-to-peer (p2p) protocols. JXTA consists of six protocols that support core P2P operations, such as peer discovery, organization, identification and messaging. JXTA is independent of the programming language, operating system, network topology and underlying communication protocol. The JXTA protocol implementations have tolerated a series of changes aimed at improving their performance, scalability, and reliability.
system components
The proposed system components are divided into 4 layers, Digital Library Access Interface (DLAI), Integrated System Management (ISM), Data Retrieve Management (DRM) and pGrid Node Monitorization (PNM). These are the types of operations that users are allowed to do, according to their functions. In each of these layers, there exist sub-layers according to the type of tasks allowed to the users.
A. Digital Library Access Interface (DLAI)
The proposed system can be abstracted into different levels from several viewing angles. Firstly, the whole concept of wireless digital library can be broken down into peer grid nodes and multimedia data. Secondly, actions can be from groups, users, and can be further divided into basic operations finally operations can be taken to objects in different abstraction levels of the system. This unit can be accessed both by the system administrator and other users. It has several operations on digital data, such as store, browse, copy, and retrieve.
B. Integrated System Management (ISM)
The Integrated System Management operation contains sub-layers such as Node Configuration and User Operations. The system administrator is responsible for performing these tasks, concerning "pGrid Nodes" and "Users".
The Node Configuration sub-layer is where the pGrid node configurations are done. Nodes configurations are taken care of by P2P technology called JXTA, which does the job of discovering peers and their neighbors. Each peer is an authenticated peer. When the user runs the system the peer will be added and shown in other peer list.
In the User Operations, the user can do several operations related to the system users. The User Operations are Share and Retrieve.
C. Data Retrieve Management (DRM)
Data Retrieve Management incorporates data grid Architecture, which integrates data storage devices and data management services. Various Grid middleware's are available to implement Grid environment like Globus, Legion, and Unicore etc. Globus being widely used and portable on open source systems, Globus Toolkit is adopted in our framework. It provides solutions such as security, resource management, data management and information service. The storage system is a basic data grid component and supports various file systems [6]. Data access service is a set up of a mechanism for accessing, managing and transferring data in the storage system [7]. Resource Management a part in data grid architecture is responsible for storage system, networks and other data grid resources. It assures end-to-end efficiency, technical assessment of the efficiency test, as well as crucial resources. Grid Security Infrastructure [8] provides environment authorization and certification mechanism to a large number of users.
D. pGrid Node Monitorization (PNM)
The Monitorization is done over a pGrid node. It is very useful to analyze node performance and behaviors along the time and setup the needed alarms. The main goal is to prevent system failures by warning the administrator and provide information to the users that the node is not available. It presents information about the actual state of the peers.
design details
Figure 3 depicts the general system structure of the proposed framework. The system provides user interfaces to access the digital library from anywhere. There are two interface steps between the high level user interface toolkit and the low level function. The first step is the user related data interface which checks whether the user is an authenticated person. Then the user is asked to enter the key (generated by the system) and sets a username and password for his pGrid node. Second step is the function call control interface. This interface does the job of finding the entire neighbor pGrid nodes and lists it in the user screen. The pGrid nodes are the basic components of storing data and also basic units of resource discovering entity.
There are different operations which can be taken to different objects; the smallest basic object is the digital object. The digital object description gives out the details of a multimedia data for instance. The multimedia data object description includes object id, size, name, data located, full path node with IP address and username who executed the operation.
The pGrid node is not only the component of the storage volume from the view point of digital library abstraction, but also it is the basic unit of computing grid environment for storing operations, as well as the basic unit of grid computational information and resource discovering entity. The MDS [9] in pGrid node provides resource information and the framework utilizes the MDS computational resource information such as host full domain name and IP address.
To every action, when the operation is finished the operation execution information (multimedia data file accessed, size, etc) will be recorded into the job information statistics database. This is done by the statistic module, which collects time benchmarks in different places of procession and updates the statistic database which is maintained in a text file in every local pGrid node. Other than the above text file there are i) data object description file which contains the details of the multimedia data and ii) grid node description file which contains the details of nodes.
Figure 3: Proposed System Structure
A. Implementation Base
In order to provide stable and different operations for the system, several functions are called.
The first function wmdl_add_data which adds a multimedia data file in the peer grid node and the user assigns a relative search key for it. The wmdl_search_data is a function which does the job of searching or querying for a particular data. The user will type a relevant search key and then the system will find to display it in the peer grid node search list with details.
The wmdl_browse is an operation, which updates the file list available in all available peer grid nodes in the network and displays it in the browse list with peer grid node name. The operation wmdl_cp is also a low level operation, which just simply copies a data between two remote nodes.
The operation wmdl_rm is for removing data from a peer grid node. This operation can be initiated by the user and can remove data only from the node. The WMDL system makes a copy of the data in some other remote node by calling the wmdl_backup operation. In this function, first the node in which the data is located is identified and then the data is moved to a temporary delete directory and it is placed in a remote node, and the status is updated as deleted in data object description file. All of these procedures are submitted as remote jobs to grid system and they take place in remote nodes.
The function wmdl_download provides the programming interface to the globus fundamental service; the wmdl_download provides two different interfaces for remote file transfer and copy. The operation wmdl_shutdown is a function for physically taking a node out of the system. When a node is to be shut down and taken out of the system all the multimedia data located in that node need to be reloaded to other nodes to guarantee the data integration.
experiments & results
The proposed framework is experimented on a network adopting only P2P and with Grid computing technology. For P2P networks, it uses TCP as its base for transferring data between peers. In case of Grid computing, transfer protocol used for transferring data is UDT. As UDT is a connection-oriented duplex protocol, it supports both reliable data streaming and partial reliable messaging. UDT entity has two parts: the sender and the receiver. The sender is dependable for data packet receiving, timer expiration detection, control packet sending and receiving. All data and control packets in both directions are exchanged between a pair of UDP ports.
Figure 4: UDT protocol Architecture
Figure 2 demonstrates the operation when a UDT Entity A sends multimedia file to another UDT entity B. The file is transferred from A's sender to B's receiver, whereas control information about that file is exchanged between the two receivers. Table 1 shows that UDT's features for bulk data transfer and streaming data processing. TCP cannot be used for this type of processing because it has two problems. First, the link has to be wiped out to employ the full bandwidth. Second, when two TCP streams start at the similar time, the stream with longer RTT will be famished due to the RTT bias problem, thus, the data analysis process will have to wait at the slower data stream. UDT, moreover, supports multi streaming i.e. streaming video to many clients. It can also allow selective streaming for each client when required, while TCP cannot send data at a fixed rate, and in UDP most of the data reliability control work has to be handled by the application.
Table 1: UDT Services/Features
Services/Features
UDT
TCP
UDP
Connection-oriented
Yes
Yes
No
Full duplex
Yes
Yes
Yes
Reliable Data Transfer
Yes
Yes
No
Partial-reliable data transfer/message
Yes
No
No
Flow Control
Yes
Yes
No
Congestion Control
Yes
Yes
No
Selective ACKs
Yes
Optional
No
Multi streaming
Dependent
Yes
No
Multi homing
Yes
No
No
We experimented the framework using these benchmarks, i) file size vs. download time, ii) simultaneous connections, iii) bandwidth utilization, iv) security, v)scalability and vi) robustness. Table 2 shows the benchmark results for our framework when incorporated in P2P only and with Grid. From Table 2, it can be seen, file size matters in P2P network, as it uses TCP for transfer and hence speed is normal when compared to using P2P and with Grid as it uses UDT protocol. Bandwidth utilization depends on number of connections i.e. number of peers connected in the network which indirectly employs in Simultaneous connections.
Table 2: Process Benchmarks
Benchmarks
P2P
P2P with Grid
File Size vs. Download Time
Normal speed as it uses TCP
Increased speed as it uses UDT
Simultaneous Connections
Supports, but increase in download time
Supports and minimal increase in download time
Bandwidth Utilization
Normal
Good
Security
Authentication provided by JXTA
Uses GSI
Scalability
Supports
More Scalable
Robustness
Limited Support
Supports
Apart from the above benchmarks, we obtained the download time taken in P2P networks and with Grid. Table 3 and 4 tabulates the total time taken for retrieving a multimedia data when using P2P and with Grid technology respectively. Figure 5 shows the plotted results for retrieval time against time for P2P and with Grid. From the figure it is clear that, the proposed framework gives less retrieval time when compared to using only P2P. The steep decrease in retrieval time in the proposed framework is because of using UDT which is incorporated in grid architecture and used with P2P.
Table 3: Time taken for Retrieving Multimedia Data using P2P Technology
Size [MB]
P2P
Packet Rate [sec]
Link Capacity [Mbits/sec]
Rate
[Mbits/sec]
Time Taken
[sec]
1
773
851
2.884
4.1
10
973
1185
6.656
13.7
25
1125
1590
8.604
25.5
50
962
2413
5.398
83.9
75
976
1476
8.264
76.8
90
1111
1030
10.012
75.7
150
1321
1290
8.707
153.5
Table 4: Time taken for Retrieving Multimedia Data using P2P and Grid Technology
Size [MB]
P2P with Grid
Packet Rate [sec]
Link Capacity [Mbits/sec]
Rate
[Mbits/sec]
Time Taken
[sec]
1
1259
4315
5.388
1.68
10
3373
5221
13.444
6.30
25
3919
5114
22.717
8.87
50
5044
5395
25.521
15.62
75
5294
5529
24.99
24.56
90
5487
5789
26.226
28.31
150
6056
6190
27.902
45.48
Figure 5: Comparing retrieval time for P2P and with Grid.
conclusion
The proposed framework for storing large bytes of data across the network and accessing it from anywhere, works efficiently with the integration of Grid Computing and P2P technology. As its commodity components, act as key components and assure a very good price and performance compromise. In this paper, the proposed framework pertaining to the discovery and dissemination of data (multimedia) in an institution or organization, when the resource management is to be considered, is experimented and the results are tabulated. From the results and benchmarks, the proposed framework works well and attains efficient state when incorporated with Grid Computing and P2P technology. As every system lags in some point, our framework, lacks in when more number of simultaneous connections, increase which results in reduced bandwidth utilization and increased retrieval time, we are working on to optimize the results obtained and to solve the above said problems.
