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METHOD TO DETERMINE SYNCHRONOUS ETHERNET CLOCK TREE FOR MANAGEABILITY USING TELEMETRY

IP.com Disclosure Number: IPCOM000252798D
Publication Date: 2018-Feb-12
Document File: 5 page(s) / 83K

Publishing Venue

The IP.com Prior Art Database

Related People

Vineet Kumar Garg: AUTHOR

Abstract

Techniques are presented for determining a synchronous Ethernet clock tree for manageability. Synchronous Ethernet (SyncE) works on the physical layer. ITU – G.8264 defines Ethernet Synchronization Messaging Channel (ESMC) messages, which are used to distributes timing information on the network. Techniques provided herein include (1) a method to trace information about clock path to a particular node (similar to traceroute for data path) and (2) a method to detect physical clock loops in a network.

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Copyright 2018 Cisco Systems, Inc. 1

METHOD TO DETERMINE SYNCHRONOUS ETHERNET CLOCK TREE FOR MANAGEABILITY USING TELEMETRY

AUTHOR:

Vineet Kumar Garg

CISCO SYSTEMS, INC.

ABSTRACT

Techniques are presented for determining a synchronous Ethernet clock tree for

manageability. Synchronous Ethernet (SyncE) works on the physical layer. ITU – G.8264

defines Ethernet Synchronization Messaging Channel (ESMC) messages, which are used

to distributes timing information on the network. Techniques provided herein include (1) a

method to trace information about clock path to a particular node (similar to traceroute for

data path) and (2) a method to detect physical clock loops in a network.

DETAILED DESCRIPTION

Although ITU – G.8264 defines ESMC messages, it does not provide a means to

detect clock loops in a network. An example loop is shown below:

R1(QL_PRC)  R2 (QL_PRC) R3 (QL_PRC) R1(loop).

This is a timing loop, where router R1 gives a clock to downstream router R2, which

gives clock to downstream router R3, and where the last router R3 gives the clock back to

R1. The lack of means to detect physical clock loops could be much more severe,

particularly for troubleshooting, when it involves a topology having multiple rings of

hierarchy, which is very common in a user’s infrastructures.

In a typical network, multiple routers are connected via multiple physical links to

communicate with each other for data or clock information. It may be difficult to know

how the clock information is carried from a clock source to each and every node in the

network simply by examining the physical topology of the network because the clock

topology is a subset of the physical topology. Consider the following simplistic sample

network topology:

A: R1---R2---R3---R4

Copyright 2018 Cisco Systems, Inc. 2

From this simple physical topology, it is not possible to derive a clock tree as it will

depend on a number of factors such as: a clock state of each router, local configurations

and network events. Some possible clock trees in this simple topology may include:

B: R1----R2R3R4;

C: R1R2---R3R4;

D: R1R2R3R4; and

E: R1R2R3R4,

in which the arrows show the clock relationship between two routers.

From a manageability point of view, it may be very difficult to determine the clock

tree at any given point in time. Techniques proposed herein can solve this problem and

provide an operator with an easy way to look up current clock topology from a physical

network topology.

The following are key elements for the proposed solution:

1. SyncE Clock-Identity is an unique identifier defined in a draft

recommendation for ITU G.8264 for enhanced ESMC messages and is dynamically

derived by the clocking infrastructure for a given node. Clock-Identity parameters of

SyncE protocol can be used for topology building process.

2. 4-Tuple (My ClockID, Peer Clock ID, My Interface, is-selelected-clk-

source) - Any node implementing this proposed method needs to maintain 4-tuple

information for...