Connection Control Connectionless data transfer(无连接的传输) Each PDU treated independently -Eg. datagram(数据报) Connection- oriented data transfer(面向连接的传输) Eg. virtual circuit(虚电路) Connection-oriented preferred (even required) for lengthy exchange of data Logical association, or connection, established between entities Three phases occur Connection establishment Data transfer Connection termination May be interrupt and recovery phases to handle errors8/76 Connection Control • Connectionless data transfer(无连接的传输) - Each PDU treated independently - E.g. datagram(数据报) • Connection-oriented data transfer(面向连接的传输) - E.g. virtual circuit(虚电路) • Connection-oriented preferred (even required) for lengthy exchange of data • Logical association, or connection, established between entities • Three phases occur - Connection establishment - Data transfer - Connection termination • May be interrupt and recovery phases to handle errors