Large File Transfer Using Multicast and P2p for Error Checking and Correction

File transfer applications are considered the second largest source of data on networks after e-mail. Users of the Internet or other online services use them commonly. They find a server with the desired information and use a file transfer protocol to download the file(s). Similarly, users of corporate networks need to transfer files back and forth using a file transfer protocol. This paper discusses how we can combine the StarBurst Multicast File Transfer Protocol (MFTP) with Peer to Peer (P2P) protocol to create a more reliable multicast protocol for transfer large files.

Using regular client-server or even peer-to-peer file transfer protocols is not efficient when distributing big files over the network from a single source to multiple receivers. Therefore, bandwidth usage and data storage reading from multicast networking can enhance transferring a series of big files to many different recipients. Section I begins with a brief overview of Multicast and P2P networks

The multicast is a mechanism used to support group communication applications such as audio and video conferencing, multi-party games and content distribution. IP multicast is used to transmit IP datagrams from one source to multiple destinations in a LAN or WAN. With IP multicast, a copy of the information sent by applications to a group address can reach all the receivers who are part of that group as shown in Figure 1.

The multicast technology operates lesser bandwidth as it deals with a group of receivers. IP multicast routing protocols use a large, heterogeneous network such as the Internet to deliver datagrams from one source to multiple of destinations efficiently.

P2P is a type of network communication in which two peers (end users) are allowed to share files and data without passing through a server and both workstations have equivalent capabilities and responsibilities as shown in Figure 2.

P2P is a type of network that is completely different from client/server architectures as shown in Figure 3. In P2P network, peers are computer systems connected to each other via the Internet [2], while in client/server architectures many computers are dedicated to serving the others.

The process begins with a user running a peer-to-peer file-sharing software (for example, µTorrent) on his computer and sending out a request for the file he wants to download then. The file can be located through the file-sharing software querying other computers connected to the Internet and running the software. When the desired file is found on a computer's hard drive, it can be downloaded. Others using the file-sharing software can get the file(s) they want from your computer's hard drive as well.

It is true that the file-transfer load is distributed among the peers (computers) exchanging files, yet others searching and transferring files from someone's computer can cause bottlenecks. Moreover, what limits the number of computers the software can search for the requested file is a leeching user who downloads files and immediately disconnects. So, some people cannot get files from his system.

Section II of the paper deals with the StarBurst Multicast File Transfer Protocol (MFTP), its components and how it works, and it contains the possible drawbacks of the MFTP. Section III provides the proposed solution to avoid the drawbacks of the MFTP. Section IV shows a comparison between the proposed solution and the Torrent. Some conclusions and future work are given in Section V.

The new starburst MFTP (Multicast File Transfer Protocol) and product line based on it have been developed by Starburst communications. This protocol operates over UDP in the TCP/IP protocol suite [4]. Three basic entities are defined in the starburst MFTP protocol. These are the frame, known as a link layer entity and has the same meaning for starburst MFTP as for other protocols, the block consisting usually of hundreds or even thousands of frames and a pass, which consists of the transmission of the whole file on the first pass, and missing pieces on subsequent passes.

How Does The StarBurst MFTP Works? As the transmission of the file begins, the StarBurst MFTP continues to transmit the blocks until the file is transmitted entirely and it does not stop after each block to wait for acknowledgment as shown in Figure 4.

Then, it sends another “Pass" consisting of only those frames that are acknowledged negatively as shown in Figure 5. A third or fourth pass may be required to complete error-free transmission to all clients. A lot of pressure on the server to send all the negatively acknowledged blocks. And the number of Passes could very high for large file transfer (more on network traffics).

The idea is to combines multicast and P2P for large file transfer and use the P2P networking for error checking and correction. Rather than retransmits those frames that were negatively acknowledged, each recipient seeks the missing frames from the others recipients. (similar to bit torrent protocol).

The first pass will not be different from the StarBurst Multicast File Transfer Protocol (MFTP)m the blocks will be transmitted continuously without waiting for any acknowledgment as shown in Figure 6.

The difference will be in the later passes; each recipient will seek any missing frames from the other recipients as shown in Figure 7.

A special case may occur when one or more than one frames are missing from all the recipients. In this case, each recipient sends a negative acknowledgment for the missing frame/s. Then the sender will retransmit only the missing frame/s as shown in Figure 8.

By using the Peer to Peer (P2P) protocol, we can reduce the pressure on the server. Also, reduce the number of retransmitting the missing frame/s by the server.

The proposed idea may look similar to the Torrent in the way it works. Studies indicated that BitTorrent was responsible for an impressive 35% of all Internet traffic [7]. This value could be reduced by using a reliable multicast protocol instead of using the Torrent. Table 1 identifies some similarities and the differences between the Torrent and the proposed idea.

By combining the StarBurst Multicast File Transfer Protocol (MFTP) with Peer to Peer (P2P) protocol, we can create a more reliable multicast protocol to transfer large files by using P2P for error checking and correction. This is also could solve the problems of the Torrent Protocol. Further research can be done in the future to evaluate and validate the proposed idea.