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Licklider Transmission Protocol is a point to point protocol for the use in deep space links. ==Design== LTP is designed to run directly over a data link layer (such as e.g. AOS), but it can also run on the User Datagram Protocol (UDP), e.g. if used in a sensor network, in a private network (where bandwidth contestation isn’t an issue), and for software debug purposes. Therefore, it does not address issues like routing or congestion control. It was originally designed to support “long-haul” transmission in an interplanetary network; its design is based on experiences with the CCSDS File Delivery Protocol (CFDP). LTP is commonly seen as the standard underlying convergence layer protocol for the Bundle Protocol ((RFC 5050 )), supporting a wide selection of networks. Developed for space communication however, its features are: * reliable data transport for important data (such as a file header) * unreliable data transport for less important data (such as image pixels—a defunct pixel can be overcome) * no negotiation exchange due to potentially higher round trip times and to avoid link underutilisation * energy efficiency, as it will only send if a link is available and distinguishes between important and unimportant data * timers work together with communication schedules and can be suspended whenever a scheduled link outage occurs * needs to be informed about link layer availability, round-trip time and communication schedule, basically requiring a management information base (MIB). LTP is highly stateful. * unidirectional sessions, circumvents high round-trip times or inability of peer to transmit. The application divides its data to send into two parts (however, either part may have a size of 0): * a ''red'' part: It contains data that has to be transported reliable, has to be acknowledged by the receiver, and has to be held available until acknowledged. This could, e.g., be a header that contains important information to decode the following data, and whose corruption would render all following data useless. * a ''green'' part. It contains data that does not require to be transported in a reliable fashion. Since reception of this data will not be acknowledged, it can be discarded after being sent out. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Licklider Transmission Protocol」の詳細全文を読む スポンサード リンク
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