CISCO_PTP_MIB moduleΒΆ

Data Classes

Enum Classes

CISCO_PTP_MIB

Revision: 2011-01-28

The MIB module for PTPv2 (IEEE1588 - 2008)

Overview of PTPv2 (IEEE 1588-2008)

This IEEE standard defines a protocol enabling precise synchronization of clocks in measurement and control systems implemented with packet-based networks, the IEEE Standard PTPv2 1588 (2008). This MIB does not address the standard IEEE 1588 (2002). The protocol is applicable to network elements communicating using IP. The protocol enables heterogeneous systems that include clocks of various inherent precision, resolution, and stability to synchronize to a grandmaster clock. The protocol supports system-wide synchronization accuracy in the sub-microsecond range with minimal network and local clock computing resources. The standard uses UDP/IP. It includes formal mechanisms for message extensions, higher sampling rates, correction for asymmetry, a clock type to reduce error accumulation in large topologies, and specifications on how to incorporate the resulting additional data into the synchronization protocol. The standard defines conformance and management capability also.

MIB description

This MIB is to support the Precision Timing Protocol (PTP) feature of Cisco System devices.

Acronyms:

ARB arbitrary BMC best master clock CAN Controller Area Network CP Communication Profile

[according to IEC 61784-1:200710]
CPF Communication Profile Family
[according to IEC 61784-1:2007]

DS Differentiated Service E2E End-to-End E2ETC End-to-End Transparent Clock EUI Extended Unique Identifier. FFO Fractional Frequency Offset GPS Global Positioning System IANA Internet Assigned Numbers Authority ICV Integrity Check Value ID Identification IPv4 Internet Protocol version 4 IPv6 Internet Protocol version 6 JD Julian Date JDN Julian Day Number MAC Media Access Control

[according to IEEE Std 802.3-2005]

MJD Modified Julian Day NIST National Institute of Standards and

Technology (see www.nist.gov)
NTP Network Time Protocol (see IETF RFC 1305
[B7])
OUI Organizational Unique Identifier(allocated

by the IEEE)

P2P Peer-to-Peer P2PTC Peer-To-Peer Transparent Clock PHY physical layer [according to IEEE Std
802.3-2005]
POSIX Portable Operating System Interface
(see ISO/IEC 9945:2003)

PPS Pulse per Second PTP Precision Time Protocol SA Security Associations SNTP Simple Network Time Protocol SOF Start of Frame TAI International Atomic Time TC Traffic Class TC Transparent Clock TLV Type, Length, Value [according to IEEE Std

802.1AB]
ToD Time of Day Synchronization ToS Type of Service UCMM UnConnect Message Manager UDP/IP User Datagram Protocol UTC Coordinated Universal Time
References:
[1] Precision clock synchronization protocol for networked

measurement and control systems - IEC 61588 IEEE 1588(tm) Edition 2.0 2009-02

Definitions from [1] section 3.1

Accuracy: The mean of the time or frequency error between the clock under test and a perfect reference clock, over an ensemble of measurements. Stability is a measure of how the mean varies with respect to variables such as time, temperature, and so on.

The precision is a measure of the deviation of the error from the mean.

Atomic process: A process is atomic if the values of all inputs to the process are not permitted to change until all of the results of the process are instantiated, and the outputs of the process are not visible to other processes until the processing of each output is complete.

Boundary clock: A clock that has multiple Precision Time Protocol(PTP) ports in a domain and maintains the timescale used in the domain. It may serve as the source of time, i.e., be a master clock, and may synchronize to another clock, i.e., be a slave clock.

Boundary node clock: A clock that has multiple Precision Time Protocol(PTP) ports in a domain and maintains the timescale used in the domain. It differs from the boundary clock in that the clock roles can change.

Clock: A node participating in the Precision Time Protocol (PTP) that is capable of providing a measurement of the passage of time since a defined epoch.

Domain: A logical grouping of clocks that synchronize to each other using the protocol, but that are not necessarily synchronized to clocks in another domain.

End-to-end transparent clock: A transparent clock that supports the use of the end-to-end delay measurement mechanism between slave clocks and the master clock. Each node must measure the residence time of PTP event messages and accumulate it in Correction Field.

Epoch: The origin of a timescale.

Event: An abstraction of the mechanism by which signals or conditions are generated and represented.

Foreign master: An ordinary or boundary clock sending Announce messages to another clock that is not the current master recognized by the other clock.

Grandmaster clock: Within a domain, a clock that is the ultimate source of time for clock synchronization using the protocol.

Holdover: A clock previously synchronized/syntonized to another clock (normally a primary reference or a master clock) but now free-running based on its own internal oscillator, whose frequency is being adjusted using data acquired while it had been synchronized/syntonized to the other clock. It is said to be in holdover or in the holdover mode, as long as it is within its accuracy requirements.

Link: A network segment between two Precision Time Protocol ports supporting the peer delay mechanism of this standard. The peer delay mechanism is designed to measure the propagation time over such a link.

Management node: A device that configures and monitors clocks.

Master clock: In the context of a single Precision Time Protocol communication path, a clock that is the source of time to which all other clocks on that path synchronize.

Message timestamp point: A point within a Precision Time Protocol event message serving as a reference point in the message. A timestamp is defined by the instant a message timestamp point passes the reference plane of a clock.

Multicast communication: A communication model in which each Precision Time Protocol message sent from any PTP port is capable of being received and processed by all PTP ports on the same PTP communication path.

Node: A device that can issue or receive Precision Time Protocol communications on a network.

One-step clock: A clock that provides time information using a single event message.

On-pass support: Indicates that each node in the synchronization chain from master to slave can support IEEE-1588.

Ordinary clock: A clock that has a single Precision Time Protocol port in a domain and maintains the timescale used in the domain. It may serve as a source of time, i.e., be a master clock, or may synchronize to another clock, i.e., be a slave clock.

Parent clock: The master clock to which a clock is synchronized.

Peer-to-peer transparent clock: A transparent clock that, in addition to providing Precision Time Protocol event transit time information, also provides corrections for the propagation delay of the link connected to the port receiving the PTP event message. In the presence of peer-to-peer transparent clocks, delay measurements between slave clocks and the master clock are performed using the peer-to-peer delay measurement mechanism.

Phase change rate: The observed rate of change in the measured time with respect to the reference time. The phase change rate is equal to the fractional frequency offset between the measured frequency and the reference frequency.

PortNumber: An index identifying a specific Precision Time Protocol port on a PTP node.

Primary reference: A source of time and or frequency that is traceable to international standards.

Profile: The set of allowed Precision Time Protocol features applicable to a device.

Precision Time Protocol communication: Information used in the operation of the protocol, transmitted in a PTP message over a PTP communication path.

Precision Time Protocol communication path: The signaling path portion of a particular network enabling direct communication among ordinary and boundary clocks.

Precision Time Protocol node: PTP ordinary, boundary, or transparent clock or a device that generates or parses PTP messages.

Precision Time Protocol port: A logical access point of a clock for PTP communications to the communications network.

Recognized standard time source: A recognized standard time source is a source external to Precision Time Protocol that provides time and/or frequency as appropriate that is traceable to the international standards laboratories maintaining clocks that form the basis for the International Atomic Time and Universal Coordinated Time timescales. Examples of these are Global Positioning System, NTP, and National Institute of Standards and Technology (NIST) timeservers.

Requestor: The port implementing the peer-to-peer delay mechanism that initiates the mechanism by sending a Pdelay_Req message.

Responder: The port responding to the receipt of a Pdelay_Req message as part of the operation of the peer-to-peer delay mechanism.

Synchronized clocks: Two clocks are synchronized to a specified uncertainty if they have the same epoch and their measurements of the time of a single event at an arbitrary time differ by no more than that uncertainty.

Syntonized clocks: Two clocks are syntonized if the duration of the second is the same on both, which means the time as measured by each advances at the same rate. They may or may not share the same epoch.

Time of Day:

Timeout: A mechanism for terminating requested activity that, at least from the requester’s perspective, does not complete within the specified time.

Timescale: A linear measure of time from an epoch.

Traceability: A property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties.

Translation device: A boundary clock or, in some cases, a transparent clock that translates the protocol messages between regions implementing different transport and messaging protocols, between different versions of IEEE Std 1588-2008/IEC 61588:2009, or different Precision Time Protocol profiles.

transparent clock: A device that measures the time taken for a Precision Time Protocol event message to transit the device and provides this information to clocks receiving this PTP event message.

Two-step clock: A clock that provides time information using the combination of an event message and a subsequent general message.

The below table specifies the object formats of the various textual conventions used.

Data type mapping Textual Convention SYNTAX ——————– —————— ——————— 5.3.2 TimeInterval ClockTimeInterval OCTET STRING(SIZE(1..255)) 5.3.3 Timestamp ClockTimestamp OCTET STRING(SIZE(6)) 5.3.4 ClockIdentity ClockIdentity OCTET STRING(SIZE(1..255)) 5.3.5 PortIdentity ClockPortNumber INTEGER(1..65535) 5.3.7 ClockQuality ClockQualityClassType

Simple master-slave hierarchy [1] section 6.6.2.4

  • Ordinary -
  • Clock(1) -
  • GrandMaster -
——-M——-

——-S——————————- - Boundary - - Clock(1) - ————–M——————M—–

2 3 | |

—–S—— ——-S—————— - Ordinary - - Boundary - - Clock(2) - - Clock(2) - ———— —–M————-M——

4 5 | |

—–S—— —–S—— - Ordinary - - Ordinary - - Clock(3) - - Clock(4) - ———— ————

Grandmaster

Boundary Clock(0-N) Ordinary Clocks(0-N) Ordinary Clocks(0-N)

Relationship cardinality
PTP system 1 : N PTP Clock PTP Clock 1 : 1 Domain PTP Clock 1 : N PTP Ports PTP Port N : N Physical Port (interface in IF-MIB)

Transparent clock diagram from section 6.7.1.3 of [1]

Boundary clock - 1
Boundary clock - 1 |

+– A –+ B | |

+———————+ | | Ordinary clock - 1| | +———————+ |

+————–+ | End-to-end | | Ordinary |——————| transparent clock- | | clock 1-1 | | 1 - 1 | +————–+ +———————-+




+————–+ | End-to-end | | Ordinary |——————| transparent clock- | | clock 1-2 | | 1 - 2 | +————–+ +———————-+

The MIB refers to the sections of the IEEE 1588 standard for reference. Throughout the MIB various secions from the standard are referenced