END-TO-END ARGUMENTS IN SYSTEM DESIGN J.H. Salter, D.P. Reed and D.D. Clark Presented by Sui-Yu Wang

Introduction A design principle that helps guide placement of functions among the modules of a distributed computer system, the “end-to-end argument” Functions placed at low levels of a system may be redundant or of little value when compared with the cost of providing them at low level Functions should be moved upward in a layered system

End-to-end Argument The function in question can completely and correctly be implemented only with the knowledge and help of the application standing at the end points of the communication system.

Example: Care File Transfer The file transfer program at host A calls the file system to read the file from the disk and make it disk-format independent The file transfer program ask the data communication system to transfer the file using some protocol that needs to split the file into packets The data communication network moves the packets from A to B The data communication programs removes the packets from the data communication protocol and hands the data to the file transfer program at host B The file transfer program ask the file system to write the received data on the disk of host B

Solutions Brute force End-to-end check and retry Improve data transmission reliability

Performance Aspects Unreliable communication makes the overall performance suffer Over reliable communication eats up the bandwidth The end-to-end check of the file transfer application must still be implemented no matter how reliable the communication system is

Other Example of the End-to-end arguments Delivery guarantees Secure transmission of data Duplicate message suppression Guaranteeing FIFO message delivery Transaction management

Conclusion The end-to-end argument is a guideline to help the application and protocol design