网络通信 ch17 传输协议.ppt

网络通信_ch17_传输协议Bilingual munications网络通信(For Master Students in the Department of Electronic Engineering)Chapter 17 Transport Protocols
Instructor: Dr. Tianshuang Qiu
School of the Electronic and Information Engineering
Fall of 2009
1
OSI与TCP/IP协议的关系
2
Introduction
The transport protocol provides an end-to-end data transfer service that shields upper layer protocols from the details of the intervening(work works. A transport protocol can be either connection oriented, such as TCP (Transmission control protocol), or connectionless, such as UDP (User datagram protocol).
If the underlying(work or work service is unreliable, such as with the use of IP, then a connection-oriented transport protocol es plex. The basic cause of plexity is the need to deal with the relatively large and variable delays experienced between end systems. These large, variable plicate(使复杂)the flow control and error control techniques.
TCP uses a credit-based(基于信用量)flow and error control technique that is somewhat different from the sliding-window flow control found in and HDLC. In essence, TCP separates acknowledgements from the management of the size of the sliding window.
Although the TCP credit-based mechanism was designed for end-to-end flow control, it is also used to assist in work congestion control. When a TCP entity detects the presence of congestion in the , it reduces the flow of data onto the until it detects an easing(缓解)in congestion.
3
传输层协议与其它协议的关系
In a protocol architecture, the transport protocol sits above work or work layer,which work related services, and just below application and other upper-level protocols.
The transport protocol provides services to transport service (TS) users, such as FTP (File Transfer Protocol ), SMTP (Simple Mail Transfer Protocol ), and . The local transport municates with some remote transport entity, using the services of some lower layer, such as the protocol. The general service provided by a transport protocol is the end-to-end transpor