AT&T 76450 - Manual (Page 12)

Common Systems Connection Standards AT&T Services, Inc
Date: June 2013
ATT-TP-76450, Issue 15
Copyright © 2013, AT&T . All Rights Reserved.
Page 12
3 Synchronization/Timing Standards
This section addresses the synchronization reference input of the device or system under
consideration, if applicable. Synchronization is not covered in the GR’s associated with NEBS.
Synchronization and synchronization input reference interfaces are documented in Telcordia
GR-1244-CORE and GR-499-CORE.
Issue 14 is a complete revision to section 3, Synchronization/Timing Standards. Network
elements that were traditionally part of the outside plant and cellular base station environments
are now coming under the AT&T TP-76450 interconnection review process. It is understood
that some of these network elements are not designed to traditional wireline CO equipment
standards. It is very helpful if the respondent submits a copy of the equipment supplier’s
documentation for any timing and synchronization requirements of the device under
consideration. In addition, respondents are encouraged to contact the AT&T Common
Systems synchronization SME to discuss the requirements and context of this section.
David Overdorf
email [email protected]
Telephone 770-232-9183
The AT&T Common Systems synchronization SME acknowledges the variability and
complexity of timing solutions that can be present with much of the equipment now being
introduced into the network. Many new systems are based upon router and switch technology
rather than traditional TDM and SONET technology. In addition, there is variability in the timing
requirements based upon the actual deployment mode. It is difficult to capture all the possible
variables in a checklist or questionnaire type document. The AT&T Common Systems
synchronization SME welcomes suggestions for improvements to the contents of section 3.
The original purpose of this section is to determine if the device under consideration has a
synchronization interface to accept external frequency timing references from the Building
Integrated Timing Supply system (BITS), and if so, does the interface meet existing North
American standards for interconnection and timing signal format. If there is a frequency timing
input reference interface, but the interface is not compliant to AT&T standards, the respondent
is asked to identify the proposed method for mitigating the non-compliant interface.
We now see systems that require some sort of timing or synchronization, but are not designed
to interconnect directly to a traditional timing signal generator with a physical twisted pair of
wires. This section now attempts to determine if some non-traditional synchronization solution,
such as a dedicated GPS antenna and receiver, IEEE-1588v2 based Precision Time Protocol
(PTP), or Network Time Protocol (NTP) will be employed. In the case of PTP and NTP
solutions, the respondent is asked for details on timing precision requirements of the device
under consideration.
For the purposes of this section, ‘synchronous interfaces’ shall include DS0 digital, T1, and
SONET. E1 and SDH may be supported in some specific applications, but are not consistent
with North American network standards. Synchronous Ethernet is not currently under