The Licklider Transport Protocol (LTP) is the “convergence layer” of choice in Interplanetary networks based on Delay-/Disruption-Tolerant architecture. It was designed for long-delay scheduled-intermittent links, offering either a reliable or an unreliable service, with “red” and “green” parts, respectively. The aim of this article is to present multicolor LTP, an LTP version consisting in a series of enhancements of which the most significant are the use of monochrome sessions, the introduction of an additional orange color offering a “notified” service, and the definition of default link colors. After a thorough examination of basic LTP mechanisms for all color variants, this article discusses two scenarios where orange seems particularly appealing: video streaming and optical interplanetary links. Numerical results offer further insight into the complex LTP mechanisms and also highlight the difference between LTP retransmissions and bundle protocol retransmissions, the latter benefitting from routing reprocessing. Multicolor LTP has already been implemented as an interplanetary overlay network (ION) plug-in and its enhancements have been proposed to Consultative Committee for Space Data Systems Space Internetworking Services Delay-/Disruption-Tolerant Networking working group for a possible inclusion in the next version of LTP specifications (LTPv2).

中文翻译：

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多色 Licklider 传输协议：未来星际链路的 LTP 版本


Licklider 传输协议 (LTP) 是基于延迟/中断容忍架构的星际网络中选择的“汇聚层”。它专为长延迟预定间歇链路而设计，提供可靠或不可靠的服务，分别具有“红色”和“绿色”部分。本文的目的是介绍多色 LTP，该 LTP 版本包含一系列增强功能，其中最重要的是单色会话的使用、引入提供“通知”服务的附加橙色以及定义默认链接颜色。在彻底检查了所有颜色变体的基本 LTP 机制后，本文讨论了橙色似乎特别有吸引力的两种场景：视频流和光学星际链路。数值结果提供了对复杂 LTP 机制的进一步了解，并突出了 LTP 重传和捆绑协议重传之间的区别，后者受益于路由重新处理。多色 LTP 已作为星际覆盖网络 (ION) 插件实施，其增强功能已提交给空间数据系统咨询委员会空间互联服务延迟/中断容忍网络工作组，以便可能包含在下一版本中LTP 规范 (LTPv2)。