Timing over IP Connection and Transfer of Clock

Document Charter Timing over IP Connection and Transfer of Clock WG (tictoc)
Title Timing over IP Connection and Transfer of Clock
Last updated 2020-03-25
State Approved
WG State Active
IESG Responsible AD Erik Kline
Charter Edit AD Erik Kline
Send notices to (None)


The Timing over IP Connections and Transfer Of Clock (TICTOC) WG is 
  concerned with highly accurate time and frequency distribution over 
  native IP and MPLS-enabled IP Packet Switched Networks (PSNs). While 
  this need arises from a variety of sources (see 
  draft-bryant-tictoc-probstat-01.txt), the application areas of focus for 
  this WG are:
  (1) Network infrastructures with the need for highly accurate time and 
  frequency distribution within well-engineered service provider or 
  enterprise campus networks. On-path support with specialized hardware 
  may be expected to be available at one or more hops on a given path.
  (2) Individual hosts and devices on the public Internet requiring 
  functionality or performance not currently available in NTP. On-path 
  support may be utilized if available, but is not expected. This 
  application brings additional requirements beyond improved accuracy, for 
  example, the traceable and authenticated distribution of UTC time, 
  including correct handling of leap seconds.
  The NTP Working Group is currently standardizing the fourth version of 
  NTP for time distribution over IP networks. The NTP WG has focused its 
  deliverables largely on standardizing the currently deployed NTPv4, 
  while collecting requirements for future extensions. These requirements 
  will transition to the tictoc WG for further development. Meeting those 
  requirements may include revision of the protocol to a new version 
  level. However, in all cases backwards compatibility and coexistence 
  with currently deployed NTPv4 is a paramount concern. An applicability 
  statement will describe the use cases for which any extension of NTP is 
  The IEEE Test and Measurement Society is in the closing stages of 
  standardizing a second version of IEEE1588. This is unofficially known 
  as IEEE1588v2 and is expected to be published as IEEE1588-2008. 
  IEEE1588v2 is emerging as a viable solution for time transfer over 
  service provider and campus Ethernet networks, and for which on-path 
  hardware support is becoming available. IEEE1588v2 specifically 
  encourages other standards organizations to adapt it to their 
  requirements, and provides guidelines for doing so. TICTOC will 
  determine whether a profile for IEEE1588v2 over IP or MPLS-enabled IP 
  networks would be suitable for (1), and if so will produce a profile 
  within the guidelines provided in the IEEE1588v2 specification. An 
  applicability statement will describe the use cases for which any 
  profile of IEEE1588v2 is targeted.
  Time and Frequency distribution is considered by many to be a complex 
  and often esoteric subject area. The WG will develop a modular framework 
  in order to map out components within the solution space, define 
  terminology, and identify common areas of protocol work that can be 
  capitalized upon.
  TICTOC will also consider the co-existence of IEEE1588v2 and NTP in the 
  same network. In doing so, TICTOC will first verify that the data model 
  of NTP can be accommodated by IEEE1588v2 protocol operation and document 
  any deficiencies compared to NTP. If there is a need to map the data 
  models, it will produce a specification for how to utilize IEEE 1588 in 
  a localized region as one portion of an NTP-based system.
  TICTOC protocols will be applicable to a variety of link layer 
  technologies. To get the highest quality time and frequency transfer the 
  user should take advantage of two types of on-path service where they 
  are available: Link based frequency transfer, and hop-by-hop delay 
  correction (for time).  Examples of link based frequency support are 
  SONET/SDH, TDM, Synchronous Ethernet and DSL with timing reference 
  support. The main types of support that can be provided by a network 
  element are boundary clock (where the clock is regenerated at the node 
  in a multistage master slave relationship) and transparent clock where 
  corrections are applied to time transfer packets as they pass through to 
  compensate for the queuing delay, and where known for asymmetry in the 
  link delay.  Transparent clock  (queue delay correction) requires 
  routers to identify a time transfer packet, record the queuing delay, 
  and either apply an on the fly correction to the packet, or to generate 
  a follow-up packet with the necessary time correction information. 
  TICTOC will ensure that any transparent clock design is acceptable in an 
  Internet environment. On-path support is not a given, and TICTOC will 
  investigate methods for automatically discovering when this support is 
  available and when it is not.
  TICTOC will transfer time and frequency over both IP and IP enabled MPLS 
  PSNs.  One of the major users of TICTOC technology is the service 
  provider community, where MPLS enabled IP networks are common. If 
  necessary, TICTOC may take advantage of the path control properties of 
  MPLS and the ability to signal modifications to per packet forwarding 
  The security of time transfer, including the authentication of the time 
  reference is an important consideration and must be designed in from the 
  The ultimate system-level accuracy of time and frequency transfer 
  depends on a number of factors outside the scope of the protocols 
  themselves. Thus, even if it is possible for TICTOC to make a number of 
  improvements at the protocol level to facilitate more accurate time and 
  frequency transfer, it is impossible for the WG to provide system-level 
  accuracy guarantees on its own.
  The TICTOC WG will co-ordinate with the PWE3 and NTP WGs in the IETF, as 
  well as IEEE1588, IEEE 802.1AS and ITU-T SG15 Q13. It is also expected 
  that active individuals in the TICTOC WG will propose the formation of 
  an IRTF RG to study more advanced aspects of time and frequency 
  First phase Objectives:
  - To develop a time and frequency distribution requirements document for 
  the two cases listed above, including coexistence of the two as appropriate.
  - To develop a document defining the modular breakdown of functionality 
  within the solution space.
  - To determine the extent to which these requirements can be satisfied 
  using IEEE1588v2 and NTPv4 within each use case, along with an 
  associated gap analysis for what requirements are not met without 
  adaptation or extension of these protocols.
  - To develop an IEEE1588v2 profile as necessary for time and frequency 
  distribution, with primary focus on (1). This profile will include a MIB 
  module for IEEE1588v2.
  - To develop extensions to NTPv4 as necessary for time and frequency 
  distribution, with primary focus on (2).
  - If required, to develop mechanisms for coexistence of IEEE1588v2 and NTP.
  - To document threat analyses and security mechanisms for all protocols 
  developed by the WG.
  - To document media mappings for link layer technologies of interest.
  Second phase Objectives (requiring re-charter of the WG):
  To propose and document algorithms, protocols and mechanisms for 
  transport, frequency acquisition, ranging, and packet selection/discard, 
  master clock selection, path selection, OAM, synchronization status 
  messaging, performance monitoring, security, and network management.