NTP Roles - Peers and Stratum Levels

Richard_M

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Hi there.

Currently ploughing thorough a book on Red Hat Certified System Administrator - Red Hat Enterprise Linux 8 - Training and Exam Preparation Guide (EX200) by Asghar Ghori. I'm on Chapter 18, page 417,418, covering NTP, and I'm stuck on what seems to be conflicting information, but is probably because I'm missing something. (Attached are two pages highlighted)

Put simply my understanding is a Time Reference is Stratum 0, a Primary NTP Server is Stratum 1, and a Secondary NTP Server is Stratum 2. NTP Peers can only exist if they share the same Stratum Levels. However the book also states that Primary and Secondary Servers can be peers of each other - which seems logically impossible given peers are supposed to share the same Stratum Level?

Thanks for any help,

Richard
 

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wizardfromoz

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G'day Richard and welcome to linux.org :)

Not sure whether this is best situated here or in Redhat, I'll mull it over.

Meanwhile I will ping one of our Redhat gurus, @f33dm3bits and he may have some valuable input, he will likely respond according to his timezone.

Good luck

Chris Turner
wizardfromoz
 

f33dm3bits

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@wizardfromoz ntp is not redhat specific but it's available on all distributions and oses.

I haven't done anything with ntp in a long time, I'd have to look it up somewhere, I'll see what I can find and remember later today or tomorrow.
 
Last edited:

Richard_M

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Reply from author suggesting it may be a mistake to suggest Primary and Secondary servers can be peers of each other.

Summary of my Understanding:

NTP Time Servers: Primary is Stratum 1, Secondary is Stratum 2 (due to network hop)

A typical architecture would involve 3 servers within a Stratum Layer (to enable them to achieve consensus between two in event of failure/error of one) - this achieved by peering within that layer

Hence often:
- 3 Primary NTP Servers, peer connections between them (in addition to their individual Time Clock sources)
- 3 Secondary NTP Servers, peer connections between them (?), taking the client loading, albeit with a slight degradation in time quality (Stratum 2)
 

f33dm3bits

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Since you got a reply from the author I can assume you have your answer?
 

Richard_M

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Not sure the etiquette on this. I feel I can work with my knowledge gained, so it can be closed on that basis. But if someone has more knowledge can they still contribute to the post. Cheers
 
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