Anil Reddy explained why a nationwide timing and frequency backup service should be made available to counter GNSS vulnerabilities at ITSF 2023.

1. National plan for distribution
of time and frequency
Anil K Reddy, AVP APAC, areddy@oscilloquartz.com, Oscilloquartz SA
ITSF 2023

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Objective:
• The Department of Telecommunications (DoT) INDIA, aims to enhance the security and resilience of
licensed telecom networks by establishing a robust national timing reference.
• Address the vulnerability of Global Navigation Satellite Systems (GNSS) as a source of time reference
and enable traceability of telecom users.
Proposal:
• Setting up time source centers (TSC) across the country to create a geographically distributed time
reference infrastructure and standardize time references in licensed telecom networks.
• The National Physical Laboratory's UTC(NPLI) and NavIC’s PNT service will serve as authorized sources
of time.
Introduction

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A. Time reference
• The concept of time reference for synchronization
encompasses:
✓ Frequency synchronization
✓ Phase Synchronization
✓ Time Synchronization
Time reference in telecom network and services
B. Indian Standard Time (IST)
• CSIR-NPL is responsible for the maintenance and
dissemination of Indian Time and for keeping it
traceable to the Coordinated Universal Time (UTC).
• CSIR-NPL generate IST, which is UTC(NPLI) plus
5:30 hours, using a bank of cesium clocks and
hydrogen masers.
• UTC (NPLI) time reference further distributed to the
TSC/NTSP location using TWSTFT/FOC/NavIC etc.
• TSC/NTSP will further distribute the Frequency/phase
reference through dedicated link to LSPs and NTP
Time reference to LSP/Public and Private organization
using public internet using URL
•

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C. Tracing requirement for licensed service providers
• Services covered:
• Access Services, Internet Services, NLD, ILD, GMPCS, PMRTS, VSAT, MSS-R, IPLC services etc.
• Licensee obligation:
• Tracing facilities for any malicious communications emanating from the network.
• Maintain user logs for services accessed such as mail, telnet, http etc.
• Restrict unknown users from accessing the services
• Implement uniform IST time zone synchronization to ensure traceability of the users
Time reference in telecom network and services cont.
Significance in telecom services
• Real time services – IPTV, VoIP, multimedia, multiplayer
gaming etc.
• Network operation, performance monitoring, network fault
diagnostics, billing and CDR generation, etc.
• Time synchronization is needed for various RAN technology
services like – WiMAX, W-CDMA, LTE-TDD, 5G, etc.
D. Time synchronization requirements of telecommunication systems
Significance in national security
• Immunity from cyberattack by using time reference from
authorized time distribution centers
• Mitigate the GNSS vulnerability by implementing terrestrial-
based time distribution network
• Ensure uniformity by using IST time reference on all network
elements

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Commonly available time references
1. GNSS timing signal
▪ Pros:
▪ Easily available
▪ Easy to deploy
▪ Commercially viable
▪ Cons:
▪ Single point of failure
▪ No redundancy supported
▪ Vulnerable to external factors like jamming, spoofing,
climatic conditions, etc.
▪ Private time reference only to those who own the GPS
clock
2. Time from internet
▪ Pros:
▪ Easily available
▪ Easy to deploy
▪ No commercial involved
▪ Cons:
▪ Need to be connected to internet always
▪ Accuracy limited to milliseconds level only
▪ Not reliable
▪ Not viable for mission-critical applications
▪ The above methods does not provide a common time reference across the country
▪ Traceability becomes difficult during forensic investigation
▪ No authenticity of time
To overcome these challenges and to enable a common time reference across the country traceable to the UTC(NPLI), the
government has decided to build a fully resilient, secured and trusted time reference for all private and public use

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• CSIR-NPL is responsible for
providing the official time
reference for India, which is
Indian Standard Time (UTC
(NPLI)).
• Time source centers
(TSCs) will be established
to distribute this time
reference signal to licensed
service providers (LSPs)
through various protocols
and interfaces
• The TSCs will provide an
accurate and reliable time
reference signal, which can
be traced back to UTC
(NPLI).
Architecture for distribution of time reference signal

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• TSC will have input reference
as below
• CISR-NPL
• RRSL or TSC
• NavIC (S and L5 band)
• Input reference at TSC will be
provided to PTP GM for further
processing and distribution to
the LSPs
• LSP will set up the transmission
medium to the TSC for fetching
timing information
Setting up of time source centers (TSC)
Time Source Center

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• The TWSTFT technique utilizes a telecommunications
geostationary satellite to compare clocks located in two
different positions, i.e., at receiving and emitting stations
• Clock at CSIR-NPL and TSC are simultaneously compared
using the satellite’s transponder links.
Dissemination of time reference from CSIR-NPL to TSCs
▪ Two-way satellite time and frequency
transfer (TWSTFT):
▪ Carrying UTC (NPLI) through optical
connectivity
• The time reference from CISR-NPL location will be
carried over dark fiber using Bi-Di SFPs till the TSC
• Bi-Di SFPs uses single fiber and reduces the asymmetry
introduced in the PTP links
• Optical timing channel (OTC) will be deployed for
carrying PTP over DWDM network for TSC input
reference from CISR-NPL

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• The CVGNSS method will be used to transfer time from CSIR-
NPL site to TSC by comparing the clocks of CSIR-NPL PRC
and TSC-PRC
Dissemination of time reference from CSIR-NPL to TSCs cont.
▪ Common view of Global Navigational
Satellite System (CVGNSS)
▪ Using satellite system (NavIC)
• UTC(NPLI) time reference is embedded
in the navigation signal which is
broadcast by the NavIC
• The NavIC receiver at time source center
will receive the UTC (NPLI) time
reference via NavIC satellite

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• LSP has to set up their own dedicated and secure link to
receive the Time reference signals from TSC.
• LSP shall set up PTP GM/T-BC/T-TC in their network to take
time reference as input and further distribute in the network
• LSP shall synchronize all network elements of their network
only with the time reference signal from TSC
Dissemination of time reference signal from TSC to LSP
▪ Distribution of time reference signal using
PTP protocol
▪ Accessing Indian standard time reference
signal through NavIC
• LSPs may use NavIC receivers for UTC (NPLI) time reference in
the network
• LSPs must employ anti-spoofing and anti-jamming techniques in
NavIC receivers to mitigate the GNSS threats
• LSPs to ensure implementation of terrestrial-based time
distribution mechanism as backup solution to mitigate single point
of failure of NavIC receiver

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• NTP out of TSC is Stratum 1.
• Class A ISP shall set up NTP server as
Stratum 2
• Class A ISP can distribute time
reference further to Class B ISP
• Class B ISP can take time reference
directly from TSC
• LSP shall synchronize all network
elements of their network with the closest
NTP servers
Dissemination of time reference signal from TSC to LSP cont.
▪ Distribution of time reference signal using NTP protocol

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A. General guidelines
• LSP shall use only time reference provided by CISR-NPL
via TSC and restrict any use of public time sources.
• LSP has to set up their own dedicated and secure link to
receive the Time reference signals from TSC.
• Time reference clock of all network elements of LSP must
trace back to UTC(NPLI).
• NTP out of TSC is Stratum 1.
• Class A ISP shall set up NTP Server as Stratum 2.
• Class A ISP can distribute time reference further to Class B ISP
• Class B ISP can take time reference directly from TSC
• The various logs maintained by Licensed service providers
using NTP Server should have a time resolution of 1
second.
• The LSP’s retailers may configure their servers and
computers to access NTP out time reference signal from
TSC through public internet using URL.
Guidelines - resilient, security and reliability
B. Security and reliability guidelines
• TSC should be fully redundant to avoid any single
point of failure.
• Each TSC would have input UTC(NPLI) time
reference from CSIR NPL (Primary) and another
TSC/RRSL (secondary) for redundancy.
• TSC should use equipment from trusted sources as
per National Security Directive on
Telecommunication(NSDTS).
• LSP must employ anti-spoofing and anti-jamming
techniques in NavIC receivers to mitigate GNSS
threat
• LSP must use terrestrial-based time distribution in
addition to NavIC time reference signal.
• Physical and cybersecurity of TSC and NOC must
be ensured as deemed fit for critical infrastructure.

13. Thank you