n of PTP. Some implementations allow the operator to configure either a one-step or two-step clock. How- ever, the accuracy of the timestamp (and consequently the accuracy of the time recovered by the downstream slave) will be better with the method that suits the hardware design and implementa- tion. The PTP node will perform better with one or the other option, SO the network engineer needs to understand what clock method is better suited to their hardware and use that. So, do not treat this value as a configuration item to simply choose based on some other external factor. One aspect that will not be covered in detail is that there are one-step and two-step behavior differ- ences that also apply to transparent clocks. There are a lot of examples in Annex C of IEEE 1588- 2008 showing the interaction between each combination of one-step and two-step clock for master, transparent, and slave. It is enough to understand that there are such things as one-step and two-step TCs, and you know where to go to find more information should you ever need to know more about them. 7.3.1 Peer-to-Peer Versus End-to-End Delay Mechanisms Two mechanisms are used in PTP to measure the propagation delay between PTP ports, and ordin- ary and boundary clocks can be implemented using either mechanism. In general, a network using one of the methods cannot coexist with ports using the other one. The methods are as follows: Delay request-response mechanism: Determines the mean path delay between ports and is more focused on the E2E delay between clocks. It uses the messages Sync, Delay_Req, Delay_Resp and the optional Follow_Up. This method is specified as a default profile in An- nex J.3 of IEEE 1588-2008, and is the same mechanism used in the telecom profiles. Peer-to-peer delay mechanism: Uses the link delay between ports. It is specified as a default profile in Annex J.4 of IEEE 1588-2008 and uses an additional set of Pdelay messages: Pdelay_Req Pdelay_Resp Pdelay_Resp_Follow_Up (if required) This latter mechanism is used in several i