WG Action: Timing over IP Connection and Transfer of Clock (tictoc)

The IESG <iesg@ietf.org> Tue, 11 March 2008 14:26 UTC

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Subject: WG Action: Timing over IP Connection and Transfer of Clock (tictoc)
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Date: Tue, 11 Mar 2008 07:26:03 -0700
Cc: yaakov_s@rad.com, tictoc@ietf.org, stbryant@cisco.com
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A new IETF working group has been formed in the Internet Area.  For
additional information, please contact the Area Directors or the WG

Timing over IP Connection and Transfer of Clock (tictoc)

Last Modified: 2008-02-12

Current Status: Active Working Group

Yaakov Stein <yaakov_s@rad.com>
Stewart Bryant <stbryant@cisco.com> 

Internet Area Directors:
Jari Arkko <jari.arkko@piuha.net>
Mark Townsley <townsley@cisco.com>

Internet Area Advisor:
Mark Townsley <townsley@cisco.com>

Mailing list:
General Discussion: tictoc@ietf.org
To Subscribe: TICTOC-request@ietf.org 
In Body: subscribe your_email_address
Archive: http://www1.ietf.org/mail-archive/web/tictoc

Description of Working Group:

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

- 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

- 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.

Goals and Milestones:

Dates are for documents exiting WG last call, and entering "Publication 
Requested" with the shepherding Area Director.
September 08 - Problem statement
November 08 - Modular Framework documentation
January 09 - Requirements analysis for use cases, including gap analysis 
for NTPv4 and 1588v2
April 09 - 1588v2 profile, if needed
April 09 - NTPv4 extensions, if needed
April 09 - Security document(s)
August 09 - MIB for IEEE 1588v2 profile and NTPv4 extensions (TICTOC MIB)
August 09 - Prioritize second phase deliverables and add milestones or 

Internet Drafts

 1. Problem Statement draft-bryant-tictoc-probstat-01.txt
 2. Modularization Draft draft-stein-tictoc-modules-00.txt
 3. Framework Draft draft-frost-packet-timing-framework-00.txt
 4. RAN Synchronization Requirements draft-zhou-tictoc-ran-sync-req-00.txt
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