The Problem with TCP. Overcoming TCP s Drawbacks

Transcription

1 White Paper on managed file transfers How to Optimize File Transfers Increase file transfer speeds in poor performing networks FileCatalyst Page 1 of 6

2 Introduction With the proliferation of the Internet, TCP (Transmission Control Protocol) has undoubtedly become the most widely used networking protocol. TCP provides a very successful means of connecting hosts together over a relatively good network. A good network is defined as a broadband network with low packet loss and low latency. The performance of TCP degrades significantly, however, on congested networks or on networks with high latency. With its FileCatalyst software suite, Unlimi-Tech provides a solution to achieve file transfer speeds that would be unobtainable with TCP. The Problem with TCP Network congestion typically causes buffer overflow of intermediate routers, inducing packet loss. In order to provide reliable data transmission, TCP requires the receiver to acknowledge packets and the transmitter to retransmit any packets that are not acknowledged or have not been acknowledged within a timeout period. Such retransmissions thus reduce the achievable throughput. Similarly, TCP responds to latency and the resulting round trip delay between the transmitter and receiver by throttling back the transmission rate and thus the achievable throughput. The maximum unacknowledged data that can be en route to the receiver is equal to the round trip delay times the end-to-end bandwidth. In its operation, TCP continually estimates this value, setting a TCP window at the transmitter to limit how much data should be sent. The window size is reduced as packet loss is detected and increased as long as communications are successful. A default maximum value for the window size that is not large enough as well as a temporarily reduced window size both limit throughput in the presence of high latency. Overcoming TCP s Drawbacks Some of these issues can be overcome by using UDP (User Datagram Protocol) rather than TCP. UDP squeezes extra performance from an IP network by not implementing some of the features a more heavyweight protocol like TCP offers. For example, UDP is a "connectionless" protocol, that, unlike TCP, does not require the sender and receiver to establish a connection before data is transmitted. By not requiring acknowledgements and retransmissions, UDP can realize throughput levels approaching the endto-end bandwidth. At the same time, however, UDP allows individual Page 2 of 6

3 packets to be dropped without any retransmission and UDP packets to be received in a different order than they were sent. As a result, UDP does not in itself provide reliable data communications. Increasing UDP s Reliability To overcome the lack of reliability of UDP while taking advantage of its high throughput, error correcting techniques can be employed by the application. Such techniques employ retransmitting of data packets without compromising transfer rates significantly. Page 3 of 6

4 FileCatalyst Transfer Engine Advanced file transfer algorithms been developed by Unlimi-Tech Software and embedded into FileCatalyst managed file transfer solution. These codes are algorithms to ensure accurate content delivery over IP networks in the presence of packet loss. The FileCatalyst suite includes a server to send and receive files as well as a number of client-side send and receive applications. FileCatalyst Java Applet: By encapsulating the advantages of Raptor inside a Java applet, Unlimi-Tech provides a solution that can run on any Java-enabled browser without having to install or configure any software on the client s machine. The applet can be preconfigured to automatically connect to a specific server or perform certain tasks. Also, the applet can be customized to look and function as desired by the application. FileCatalyst Hot Folder & Command Line: In this client-side application, the user downloads and installs a scheduler which can be configured to monitor a Hot Folder. To upload a file, the user need only drag and drop the desired file into the Hot Folder, and the file is scheduled for transmission either immediately or at a pre-determined time. FileCatalyst Server: The FileCatalyst Server supports both transmit and receive functions. For example, FileCatalyst client-side applications can send files to this server application running at the destination, where FileCatalyst Server can receive many files simultaneously and perform various post-processing tasks on each of the received files. The benefits of using Java at the client side are:? Operating system independence -- can run on Windows, Linux, or Solaris systems.? Completely Web-based -- does not require any client-side installation of software by the user.? Preconfigured functionality -- the applet can be preconfigured to automatically connect to a specific server or perform certain tasks.? Completely customizable -- the applet can be customized to look and function as desired by the application. Page 4 of 6

5 Usage Scenarios FileCatalyst server and Java clients makes it extremely useful in environments where fast, easy file transfer is an absolute necessity. Unlimi-Tech s product solution dramatically simplifies the processes required to completely and perfectly deliver data over any digital network. This technology is largely immune to network impairments such as packet loss and delay, as illustrated in the example below showing the performance of connections from Los Angeles to various global locations with specific network RTT and loss. The line speed for this test is a T3 (45 mbps.) Los Angeles to Hong Kong London New York File Size [RTT, Loss] 2GB [360, 1%] 2GB [140, 1%] 2GB [70, 1%] Transfer Time TCP/ftp/ HTTP FileCatalyst Savings 17 Hours 28 Minutes 97% 7 Hours 28 Minutes 93% 3 Hours 28 Minutes 84% The gains provided by FileCatalyst over regular TCP-supported file transfer are significant and can be realized over the public Internet, over enterprise networks, over long-distance Wide Area Networks, and over wireless and satellite networks. The technology is inherently scalable, supporting reliable broadcast/multicast data delivery over a range of IP-based communications channels. Page 5 of 6

6 Summarizing the Benefits FileCatalyst end-to-end solution offers a variety of benefits, including:? IP based -- works on any IP based network? Lightweight -- uses very little system resources? Immune to latency -- utilizes UDP to overcome RTT issues? Reliable -- uses advanced algorithms to compensate for packet loss? Improved throughput -- increases file transfer speeds significantly Moreover, FileCatalyst provides a client-side application that requires no special software other than a Java-enabled Web browser to run the solution it does not get much more lightweight than that! Page 6 of 6