tailieunhanh - sams teach yourself tcp ip in 24 hours phần 9

Dòng Transmission Control Protocol (SCTP ), được mô tả trong RFC 2000 và các văn bản sau đó, là một hướng kết nối giao thức vận chuyển (và do đó tương tự như TCP), nhưng, như UDP, SCTP là định hướng thông điệp. SCTP cũng cung cấp khả năng để | 344 HOUR 19 Streaming and Casting Stream Control Transmission Protocol SCTP which is described in RFC 2000 and later documents is a connection-oriented transport protocol and thus more similar to TCP but like UDP SCTP is more message-oriented. SCTP also offers the capability to maintain several message streams in parallel through a single connection. Datagram Congestion Control Protocol DCCP which is described in RFC 4340 also borrows features from both TCP and UDP. DCCP is connection-oriented like TCP with fast but unreliable delivery like UDP . Both SCTP and DCCP perform something called congestion control. As you can see by the name DCCP is especially interested in providing a congestion control mechanism. Congestion control is a means for reducing the kinds of retransmission issues associated with TCP and providing more efficient use of the bandwidth. Algorithms used by the protocol adjust the characteristics of the data flow to optimize throughput and reduce the number of retransmitted packets. Implementations of SCTP and DCCP are available now. SCTP has been around for a little longer and is perhaps better known to developers but DCCP shows promise. Multimedia Links You don t have to surf far to find video and audio images embedded in web pages. Click a link to hear a sound watch video or listen to a vocal track. You might be wondering what is actually happening with you click that link. The answer of course depends on where the link goes. Many multimedia links are simply files. As you learned earlier in Hour 17 HTTP HTML and the World Wide Web an a tag with an HREF attribute is a reference to another resource. In previous examples that resource was a web page. However the reference can point to any type of file as long as the browser knows how to interpret the file s contents. Modern browsers can handle many different types of file formats. On Windows systems the file extension the part of the filename after the period such as .doc .gif or .avi tells the .