问题描述
我最近检阅了本书的"UNIX网络编程，第1卷" 理查兹·史蒂文斯(Richards Stevens)和我发现，除了TCP和UDP，还有第三种传输层标准: SCTP .
I recently checked out the book "UNIX Network Programming, Vol. 1" by Richards Stevens and I found that there is a third transport layer standard besides TCP and UDP: SCTP.
摘要:SCTP是一种传输级协议，它像UDP一样是消息驱动的，但是像TCP一样可靠.这是IBM DeveloperWorks的简短介绍
Summary: SCTP is a transport-level protocol that is message-driven like UDP, but reliable like TCP. Here is a short introduction from IBM DeveloperWorks.
老实说，我以前从未听说过SCTP.我不记得在任何网络书籍中都读过它，或者在我上过的课上都没有听说过它.阅读其他关于SCTP的问题，这表明我并不孤单，缺乏知识.
Honestly, I have never heard of SCTP before. I can't remember reading about it in any networking books or hearing about it in classes I had taken. Reading other stackoverflow questions that mentions SCTP suggests that I'm not alone with this lack of knowledge.
为什么SCTP如此未知?为什么使用率不高?
推荐答案
实际上，SCTP主要用于电信领域.传统上，电信交换机使用SS7( 7号信令系统)互连电信网络中的不同实体. .例如-电信提供商的订户数据库(HLR)，带有交换机(MSC)，订户也已连接(MSC).
Indeed, SCTP is used mostly in the telecom area. Traditionally, telecom switches use SS7 (Signaling System No. 7) to interconnect different entities in the telecom network. For example - the telecom provider's subscriber data base(HLR), with a switch (MSC), the subscriber is connected too (MSC).
电信领域正在朝着更高的速度和更易到达的环境发展.这些变化之一是用一些更加优雅，快速和灵活的基于IP的协议代替SS7协议.
The telecom area is moving to higher speeds and more reachable environment. One of these changes is to replace SS7 protocol by some more elegant, fast and flexible IP-based protocol.
电信领域非常保守. SS7网络在这里已经使用了数十年.这是一个非常可靠且封闭的网络.这意味着普通用户无法访问它.
The telecom area is very conservative. The SS7 network has been used here for decades. It is very a reliable and closed network. This means a regular user has no access to it.
相比之下，IP网络是开放的并且不可靠，如果电信网络至少不能处理SS7所处理的负载，它就不会转换为IP网络.这就是开发SCTP的原因.它尝试:
The IP network, in contrast, is open and not reliable, and telecoms will not convert to it if it won't handle at least the load that SS7 handles. This is why SCTP was developed. It tries:
- 模仿几十年来积累的SS7网络的所有优势.
- 在速度，安全性和冗余性方面创建优于TCP的面向连接的协议
最新版本的Linux已经具有SCTP支持.
The latest releases of Linux already have SCTP support.
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