tailieunhanh - Báo cáo hóa học: " Passing Corrupt Data Across Network Layers: An Overview of Recent Developments and Issues"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài:Passing Corrupt Data Across Network Layers: An Overview of Recent Developments and Issues | EURASIP Journal on Applied Signal Processing 2005 2 242-247 2005 Hindawi Publishing Corporation Passing Corrupt Data Across Network Layers An Overview of Recent Developments and Issues Michael Welzl Distributed and Parallel Systems Group Institute of Computer Science University of Innsbruck 6020 Innsbruck Austria Email Received 6 August 2003 Revised 16 June 2004 Recent Internet developments seem to make a point for passing corrupt data from the link to the network layer and above instead of ensuring data integrity with a checksum and ARQ. We give an overview of these efforts the UDP Lite and DCCP protocols and explain which circumstances would justify delivery of erroneous data clearly the missing piece in the puzzle is efficient and meaningful interlayer communication. Keywords and phrases UDP Lite DCCP TCP checksum wireless links link layer ARQ. 1. INTRODUCTION Network layers are a powerful concept of abstraction a programmer of a web browser cannot be aware of lower-layer issues such as routing or even parity control. The ISO OSI model is very valuable as a means to classify mechanisms thereby facilitating communication among network professionals as well as teachers and their students. From a purely technical efficiency oriented perspective however it turns out that strict layering can lead to duplicated functionality checksums in TCP IP and underneath as well as misused TCP over the ATM available bit rate ABR service inefficient if a frame belonging to a large IP packet is lost the whole packet becomes useless or even unusable technology ATM and Internet QoS . The OSI model sometimes seems to contradict the important design principles in a sense they have become commandments for Internet designers called end-to-end arguments which say that functions required by communicating applications can be correctly and completely implemented only with the knowledge and help of the applications themselves 1 . Basically this means that most .