全称：Serial Line Address Resolution Protocol。

简单的说，就是串口链路上用来检测邻居的协议，定义在HDLC上，Cisco私有。

wikipedia的说明：

The Cisco HDLC extensions also include the definition of SLARP or the Serial Line Address Resolution Protocol (ARP). SLARP is used to provide dynamic address assignment between two endpoints across a serial line, a keep-alive mechanism for ensuring the availability of a given link, and finally a method for determining link health.

The keep-alive mechanism works in a request/response fashion between the two serial line endpoints. Sequence numbers carried inside the SLARP frames are incremented for each keep-alive sent, and as such the health of the link can be determined by each endpoint by keeping track of the sequence. If a certain count of sequence numbers is missed, the keep-alive frames are deemed to be lost, and an alert is pushed up through higher layer protocols to say that the frame has most likely been lost.