http://en.wikipedia.org/wiki/Stream_Control_Transmission_Protocol
因为TCP的一些限制而出现了SCTP，
TCP provides both reliable data transfer and strict order-of-transmission delivery of data. Some applications need reliable transfer without sequence maintenance, while others would be satisfied with partial ordering of the data. In both of these cases, the head-of-line blocking offered by TCP causes unnecessary delay. 提供能够灵活拆分组装的TCP
The stream-oriented nature of TCP is often an inconvenience. Applications must add their own record marking to delineate their messages, and must make explicit use of the push facility to ensure that a complete message is transferred in a reasonable time. 基于stream的不如基于消息的用起来简单
The limited scope of TCP sockets complicates the task of providing highly-available data transfer capability using multi-homedhosts. 自动容错支持的不好，比如我给一批IP都可以服务请求，一个坏了其他自动接入，当前TCP要靠外部工具来完成
TCP is relatively vulnerable to denial-of-service attacks, such as SYN attacks. 易受攻击
所以SCTP的feature就是跟上面的问题一一对应：
Multihoming support in which one or both endpoints of a connection can consist of more than one IP address, enabling transparent fail-over between redundant network paths. 多个IP可以绑定，自动容错
Delivery of chunks within independent streams eliminate unnecessary head-of-line blocking, as opposed to TCP byte-stream delivery. 多路stream，不用排队
Path selection and monitoring select a primary data transmission path and test the connectivity of the transmission path. 选择一条最好的路径，TCP是没有的，只能靠IP自己调优了
Validation and acknowledgment mechanisms protect against flooding attacks and provide notification of duplicated or missing data chunks.
Improved error detection suitable for Ethernet jumbo frames. 验证更多了，四次捂手