dpd

ipsec sa ike sa 重新建立需要按照规定的时间或者达到指定的流量才会重新建立，此时中途如果一端的隧道中断，另一端可能无法感知，导致***流量不通。 使用dpd技术 相当于心跳报文，当指定周期无法收到对端的dpd报文，删除ipsec相关隧道，重新发起隧道协商，可以减少***隧道中断时间 注意： 1、实践过程中发现 a端配置dpd，b端不配置，导致a端发出的dpd报文无法得到响应，产生dpd failure ，重新发起隧道协商，但是b端认为*** 隧道正常，隧道状态up，导致*** 网络不通，此时需要2端都开启dpd 检测，或者2端都关闭dpd检测

I'm writing a routine to convert between BCD (4 bits per decimal digit) and Densely Packed Decimal (DPD) (10 bits per 3 decimal digits). DPD is further documented (with the suggestion for software to use lookup-tables) on Mike Cowlishaw's web site . This routine only ever requires the lower 16 bit of the registers it uses, yet for shorter instruction encoding I have used 32 bit instructions wherever possible. Is a speed penalty associated with code like: mov data,%eax # high 16 bit of data are cleared ... shl %al shr %eax or and $0x888,%edi # = 0000 a000 e000 i000 imul $0x0490,%di # = aei0