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One of the biggest problems facing the communications industry in terms of 1588v2 deployment for phase, synchronization, and time applications is network asymmetry due to PTP`s inability to compensate for or manage it, and its direct impact on loss of accuracy. The mathematical assumption for calculating the PTP network delay is that the delays in the upstream and downstream paths between the grand master/master clock and the slave/limit clock are the same. Path timeout consists of three types of delay elements: connection timeout, serialization delay, and packet delay variation (POS). Connection timeout and serialization delay are static and potentially asymmetric components. The POS embodies the real variation in packet delay propagation when packets pass through switches and routers. The typical Ethernet switch/router has input and output buffers that communicate via a very fast backplane or switch structure. The main contribution of POS comes from output buffering and queue. If the output subnet is still available to accept packets, the delay variation is small. Heavy traffic can cause increased delay fluctuations due to this output buffering. This POS is the leading cause of IEEE 1588 time errors. IEEE 1588-2008 lists the following features that can be supported by implementations: Clock properties are published in IEEE 1588-2002 synchronization messages and in IEEE 1588-2008 announcement messages.

The current clock master transmits this information at regular intervals. A clock that considers itself a better main clock will transmit this information to trigger a change in the main clock. As soon as the current master detects the best clock, the current master stops transmitting synchronization messages and associated clock properties (announce the messages in the case of IEEE 1588-2008) and the best clock takes over than the master. [10] The BMC algorithm only takes into account the self-declared quality of the clocks and does not take into account the quality of the network connection. [11] Using the BMC algorithm, PTP selects a primary time source for an IEEE 1588 domain and for each network segment in the domain. IEEE 1588 limit clocks are an effective way to reduce packet delay variation. A limit clock executes the PTP protocol and is synchronized with the main clock. The boundary clock, in turn, acts as the main clock for all slaves within the same network.

The Precision Time Protocol (PTP) specified in the IEEE 1588v2 standard is the latest packet-based synchronization technology. Originally designed to provide precise timing for mission-critical industrial automation applications, it now offers the highest level of frequency, phase, and precise time of day for wireless link networks. IEEE 1588 standards describe a hierarchical master-slave architecture for clock distribution. In this architecture, a time distribution system consists of one or more communication media (network segments) and one or more clocks. An ordinary clock is a device with a single network connection and is either the source (master or leader) or the destination (slave or follower) of a synchronization reference. A limit clock has multiple network connections and can synchronize exactly one network segment with another. A synchronization master is selected for each network segment of the system. The root synchronization reference is called a grand master.

[6] The Grand Master transmits synchronization information to the clocks in his network segment. The boundary clocks present in this segment then transmit the exact time to the other segments with which they are also connected. When transmitted over a Carrier Ethernet (CEN) network, 1588v2 requires a dedicated CoS or even a dedicated EVC – with strict requirements for frame loss ratio, frame delay, and delay variation between frames. IEEE 1588-2008, also known as Precision Time Protocol (PTP) v2, is a packet-based two-way communication protocol designed to accurately synchronize clocks with an accuracy of submitted seconds. The PTP standard includes a hierarchical master-slave architecture for clock distribution. Under this architecture, an ordinary clock is a device with a single network interface and is either a master or a slave. A limit clock (BC) is a device with multiple network interfaces. One of them acts as a slave clock and the other as a master. A transparent clock (TC) is a device that measures the time it takes to transmit the PTP message and makes this information available to watches that receive this PTP message. PTP operation is based on the transmission of short messages to determine system properties and transmit time information. To determine the travel time, a delay measurement method is used, which is then used to set the local clocks. IEEE 1588 uses a specific algorithm – the Best Master Clock (BMC) algorithm – to determine which clock is of the highest quality within the network and to create a master/slave hierarchy.

The master periodically sends the current time as a message to the other clocks. According to ieee 1588-2002, broadcasts are sent up to once per second. According to IEEE 1588-2008, up to 10 per second is allowed. IEEE 1588-2002 uses a selection algorithm based on similar properties. Ethernet: Starting with version 2 of the IEEE1588 standard, a native Layer 2 Ethernet implementation has been developed. PTP can use Ethernet as the transport protocol. The well-known Ethernet type for PTP traffic is 0x88F7 PTP messages can use User Datagram Protocol over Internet Protocol (UDP/IP) for transport. IEEE 1588-2002 uses only IPv4[9]:Appendix D transports, but has been extended to include IPv6 in IEEE 1588-2008. [8]: Appendix F In ieee 1588-2002, all PTP messages are sent via multicast messaging, while IEEE 1588-2008 introduced an option for devices to negotiate unicast transmission port by port. [8]: Section 16.1 Multicast transmissions use IP multicast addressing, for which multicast group addresses are defined for IPv4 and IPv6 (see table). [8] : Appendix D and E Urgent event messages (synchronization, Delay_req, Pdelay_Req and Pdelay_Resp) are sent to port number 319. Common messages (advertising, Follow_Up, Delay_Resp, Pdelay_Resp_Follow_Up, management and signaling) use the port number 320.

[8]: Section 6.4 IEEE 1588-2019 adds optional and backward compatible additional features:[5] PTP is used to synchronize the clock of a network client with a server (similar to NTP). However, PTP is mainly used in local networks, with much higher accuracy than NTP (usually from 10 microseconds to 10 nanoseconds). Is specified in IEEE 1588. The limit clock (BC) is specified in versions 1 and 2 of the IEEE 1588 standard. The limit clock feature can be implemented in a switch/router at the edge of a network. A detailed history can be found under www.nist.gov/el/isd/ieee/intro1588.cfm. The original version of PTP, IEEE 1588-2002, was published in 2002. IEEE 1588-2008, also known as PTP version 2, is not backward compatible with the original 2002 version. IEEE 1588-2019 was released in November 2019 and includes backward compatible enhancements to the 2008 release. IEEE 1588-2008 includes a profile concept that defines PTP operating parameters and options. For applications such as telecommunications, energy distribution and audiovisual media, several profiles have been defined. .