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 2008-03-06
State Approved
WG State Active
IESG Responsible AD Suresh Krishnan
Charter Edit AD (None)
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.