# US 12,184,407 B2 · Secured clock synchronization in a packet-compatible network

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- Number: US 12,184,407 B2
- Document ID: US12184407B2
- Status: Granted
- Kind: B2
- Application number: 17/991,356
- Filed: 2022-11-21
- Published: 2023-06-01
- Granted: 2024-12-31
- Earliest claimed: 2021-11-23
- Assignees: Adtran Networks SE
- Applicants: ADVA Optical Networking SE
- Inventors: Michael Rabinovich; Andrew Sergeev; Joo Yeon Cho; Shihuan Zou
- Web page: https://patentgrep.com/patent/US12184407B2

## CPC

- H04J 3/0667: {Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays (arrangements for monitoring round trip delays in packet switching networks H04L43/0864)}
- H04J 3/0644: {External master-clock}
- H04J 3/14: Monitoring arrangements {(for SDH/SONET rings H04J3/085)}
- H04J 3/0673: {using intermediate nodes, e.g. modification of a received timestamp before further transmission to the next packet node, e.g. including internal delay time or residence time into the packet}
- H04L 63/0428: {wherein the data content is protected, e.g. by encrypting or encapsulating the payload}
- H04L 63/126: {the source of the received data}
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

There is provided a technique of securing clock synchronization between master clock node (MCN) and client clock node (CCN). During a cycle of exchanging PTP messages between MCN and CCN, MCN generates an associated paired message for each PTP message generated thereby and informative of t1 or t4 timestamps provided by MCN and sends each paired message to a validation entity (VE) via a secured channel between MCN and VE. When PTP messages traverse transparent clock nodes (TCN) between MCN and CCN, each TCN generates a paired message for each version of PTP message updated thereby and sends each generated paired message to VE via a secured channel between respective TCN and VE. VE uses the received paired messages to provide a validation of the cycle, wherein synchronization-related task(s) (e.g. clock correction by the client clock node, etc.) are provided only subject to successful validation of the cycle by VE.

## Claims

### Claim 1

A method of securing a clock synchronization between a master clock node and a client clock node in a packet-compatible network, the method comprising:
during a cycle of exchanging one or more sequences of Precision Time Protocol (PTP) messages between the master clock node and the client clock node, generating, by the master clock node, a paired message for each PTP message generated thereby and informative of accurate t1 timestamp or of t4 timestamp provided by the master clock node;
sending, by the master clock node, each paired message to a validation entity, wherein the paired messages are sent via a secured channel between the master clock node and the validation entity;
using, by the validation entity, the paired messages to provide a validation of the cycle; and
providing a synchronization-related task subject to successful validation of the cycle by the validation entity.

### Claim 2 (depends on 1)

The method of claim 1, wherein the synchronization-related task is a clock correction provided by the client clock node.

### Claim 3 (depends on 1)

The method of claim 1, wherein the PTP messages are traversing one or more transparent clock nodes between the master clock node and the client clock node, each transparent clock node updating, with its residence time, correction fields in versions of at least part of PTP messages traversing therethrough, the method further comprising:
during the cycle, generating by each of the one or more transparent clock nodes a paired message for each version of PTP message updated thereby and sending each generated paired message to the validation entity, wherein
the paired messages are sent via a secured channel between a respective transparent clock node and the validation entity; and
using, by the validation entity, the paired messages received from the one or more transparent clocks when validating the cycle.

### Claim 4 (depends on 3)

The method of claim 3, wherein each of the one or more transparent clock nodes updates received versions of PTP messages from one of the following combinations of PTP messages: SYNC and DELAY REQUEST PTP messages, SYNC and DELAY RESPONSE PTP messages, FOLLOW UP and DELAY REQUEST PTP messages and FOLLOW UP and DELAY RESPONSE PTP messages.

### Claim 5 (depends on 3)

The method of claim 3, wherein the validation entity is implemented as a part of the client clock node and operatively connected by respective secured channels with the master clock node and each of the one or more transparent clock nodes or the validation entity is implemented as a centralized entity operatively connected with the master clock node, the client clock node and each of the one or more transparent clock nodes by respective secured channels.

### Claim 6 (depends on 3)

The method of claim 3, wherein each of the secured channels is Authenticated Encryption with Associated Data (AEAD) secured channel.

### Claim 7 (depends on 3)

The method of claim 3, wherein the paired messages are copies of respective versions of PTP messages or are derivatives thereof.

### Claim 8 (depends on 3)

The method of claim 3, wherein the master clock node generates the paired messages as copies of respective versions of PTP messages and the one or more transparent clock nodes generate the paired messages as derivatives of respectively updated versions, the derivatives informative of residence time of the respective transparent clock nodes.

### Claim 9 (depends on 3)

The method of claim 3, wherein the cycle is constituted by multiple sequences of PTP messages and wherein at least one among the master clock node and the one or more transparent clock nodes stores the paired messages generated during the cycle and transmit them all together to the validation entity for the cycle validation.

### Claim 10 (depends on 3)

The method of claim 3, wherein the validation of the cycle comprises validating all accurate t1 timestamps, all t4 timestamps and data in all respective correction fields in PTP messages received by the client clock during the cycle.

### Claim 11 (depends on 10)

The method of claim 10, wherein the validation of the cycle further comprises at least one of: 1) authorizing sources of SYNC PTP messages and, thereby validating t2 timestamps provided by the client clock node in response to reception of the SYNC PTP messages, 2) authorizing the transparent clock nodes as sources of updated versions of PTP messages.

### Claim 12 (depends on 3)

The method of claim 3, wherein each paired message from the one or more transparent clock nodes is generated as a derivative from a respective updated version of PTP message and is informative of a residence time value used for a respective update.

### Claim 13 (depends on 12)

The method of claim 12, wherein the validation of the cycle comprises, for each sequence of PTP messages in the cycle:
comparing an accurate t1 timestamp in a paired message received by the validation entity from the master clock node with an accurate t1 timestamp in a version of PTP message received by the client clock node;
comparing a value in a correction field in the version of PTP message bearing the accurate t1 timestamp and received by the client clock node with a sum of residence time values from all paired messages informative of the accurate t1 timestamp and received by the validation entity from the one or more transparent clock nodes;
comparing a t4 timestamp in a paired message received by the validation entity from the master clock node with a t4 timestamp in a version of PTP message received by the client clock node;
comparing a value in a correction field of the version of DELAY RESPONSE message received by the client clock node with a sum of residence time values from all paired messages informative of t4 or t3 timestamps and received by the validation entity from the one or more transparent clock nodes; and
considering the validation of the cycle as successful when, for each sequence of PTP messages in the cycle, all compared values are equal.

### Claim 14

A master clock node configured to operate in a packet-compatible network comprising a client clock node operatively connected to the master clock node, wherein the master clock node is further configured to:
during a cycle of exchanging one or more sequences of Precision Time Protocol (PTP) messages between the master clock node and the client clock node, generate a paired message for each PTP message generated thereby and informative of accurate t1 timestamp or of t4 timestamp provided by the master clock node;
send each paired message to a validation entity, wherein the paired messages are sent via a secured channel between the master clock node and the validation entity; and
upon successful validation of the cycle by the validation entity, provide a synchronization-related task, wherein the validation is provided with the help of the paired messages.

### Claim 15 (depends on 14)

The master clock node of claim 14 configured to traverse the one or more sequences of PTP messages via one or more transparent clock nodes between the master clock node and the client clock node, each transparent clock node configured to update, with its residence time, correction fields in versions of at least part of PTP messages traversing therethrough.

### Claim 16 (depends on 15)

The master clock node of claim 15 configured to be operatively connected to the validation entity implemented as a part of the client clock node and operatively connected by respective secured channels with each of the one or more transparent clock nodes between the master clock node and the client clock node.

### Claim 17 (depends on 15)

The master clock node of claim 15 configured to be operatively connected to the validation entity implemented as a centralized entity operatively connected with the client clock node and each of the one or more transparent clock nodes by respective secured channels.

### Claim 18

A non-transitory computer-readable medium comprising instructions that, when executed by a master clock node comprising a memory storing a plurality of program components executable by the master clock node operable in a packet-compatible network comprising a client clock node operatively connected to the master clock node, cause the master clock node to:
during a cycle of exchanging one or more sequences of Precision Time Protocol (PTP) messages between the master clock node and the client clock node, generate a paired message for each PTP message generated thereby and informative of accurate t1 timestamp or of t4 timestamp provided by the master clock node;
send each paired message to a validation entity, wherein the paired messages are sent via a secured channel between the master clock node and the validation entity; and
upon successful validation of the cycle by the validation entity, provide a synchronization-related task, wherein the validation is provided with the help of the paired messages.

### Claim 19 (depends on 18)

The non-transitory computer-readable medium of claim 18, wherein the one or more sequences of PTP messages traverse one or more transparent clock nodes between the master clock node and the client clock node, each transparent clock node configured to update, with its residence time, correction fields in versions of at least part of PTP messages traversing therethrough.