When L2CAP channels are moved from one Controller to another data can be lost. Also, some applications require a residual （殘留的;殘余的）error rate much smaller than some Controllers can deliver. L2CAP provides error checks and retransmissions of L2CAP PDUs. The error checking in L2CAP protects against errors due to Controllers falsely（虛偽，不實(shí)地） accepting packets that contain errors but pass Controller-based integrity checks. L2CAP error checking and retransmission also protect against loss of packets due to flushing by the Controller. The error control works in conjunction with（與...協(xié)力 ）flow control in the sense that（也就是說(shuō)） the flow control mechanism will throttle （調(diào)節(jié)）retransmissions as well as first transmissions
1.l2cap 提供了錯(cuò)誤檢查和重傳l2cap pdus.
這種錯(cuò)誤檢查是為了對(duì)抗固件接收了那些通過(guò)了控制器的crc劫窒，hec檢查的負(fù)負(fù)得正的錯(cuò)誤包.
2.重傳也用于保護(hù)由于控制機(jī)flush引起的丟包
（實(shí)際controller也有很多其他原因?qū)е聛G包，如檢查到l2cap len 因?yàn)樨?fù)負(fù)得正超過(guò)正常數(shù)據(jù)包大小酥诽，而遭到丟棄捻撑；如因?yàn)榭刂破髯陨韇uffer管理原因造成丟包；如沒(méi)有及時(shí)收取hw的內(nèi)存數(shù)據(jù)而hw ack對(duì)方后立即使用該buffer）
3.the error control 和flow control的協(xié)作也就是流程控制機(jī)制將會(huì)調(diào)節(jié)重傳就好像是第一次傳輸一樣.
