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在CCITT1980年黄皮书中,首次提出的7号信令系统被说明为“一种国际性的标准化通用共路信令(CCS)系统,这种系统:最适合具有程控交换机的数字电信网;能满足现在和将来具有呼叫控制、遥控、网络数据库接入及管理和维护信令的电信网中,处理机间事务处理信息传递(电路和非电路相关)的要求;提供可靠的方法,保证按正确的顺序无丢失或重复地传送信息。”于是该系统包括一个三级消息传递部分(MTP—用于无连接的消息传递)、一个电话用户部分(用于模拟呼叫的建立和控制)、一个数据用户部分(用于模拟电路交换数据)和一个与OSI七层模型有“模糊”关系的四级结构模型。在1984年红皮书中,MTP大大完善了(尤其在拥塞控制方面)增加了一个新的功能级来提供附加的传递功能度(信令连接控制部分或SCCP);一个ISDN用户部分向数字设备提供呼叫控制;并对结构模型进行了“调整”。今后的努力集中于端到端ISDN信令的兼容性(SS7和D通路规程的协调)、非电路相关的处理能力(例如网络数据库的相互作用)、一个完善的操作和维护应用部分(OMAP)、以及一个与OSI模型更正式的结构关系。
In the 2007 CCITT Handbook, the first proposed signaling system No. 7 was described as “an internationally standardized common-channel signaling system (CCS) that is best suited for digital telecom networks with PBXs; Meeting the requirements of current and future telecommunication networks for call handling, remote control, network database access, and management and maintenance signaling, handling inter-machine transaction information transfer (circuit and non-circuit related) requirements; and providing reliable methods of ensuring that the correct ”The system then consists of a Level 3 messaging section (MTP - for connectionless messaging), a telephony user section (for simulating call setup and control), a The data user part (used to simulate circuit-switched data) and a four-level structural model that has a “fuzzy” relationship with the OSI seven-layer model. In the 1984 Redbook, MTP greatly improved (especially in congestion control) by adding a new functional level to provide additional delivery functionality (signaling connection control part or SCCP); an ISDN subscriber part to provide a call to a digital device Control; and “adjustment ” to the structural model. Future efforts will focus on the compatibility of end-to-end ISDN signaling (coordination of SS7 and D-path procedures), non-circuit-related processing capabilities such as network database interactions, a well-established Operation and Maintenance Application Part (OMAP) , And a more formal structural relationship with the OSI model.