Re: [Detnet] draft-geng-detnet-requirements-bounded-latency-02 revised for comments

[Stewart Bryant <[e-mail]>]

On 26/06/2019 11:20, [e-mail] wrote:
> Colleagues,
> 
>  From a network operator’s point of view I do not want the extra cost of 
> highly accurate clocks in routers so prefer Detnet to work with the 
> current clocks I have in routers. For an exact specification we would 
> have to list the clock specifications in the typical routers that 
> network operators use (it’s not information I have at my fingertips).
> 

Peter,

Ethernet is spec'd at 100ppm and that is what most cheap crystals do, so 
I think that is all you get if you fall back to basics.

However cell sites need 50ppb, and this resulted in so-called syncE at 
that specification. In the mobile backhaul there will also be precision 
time - 1.2us for minimum operation of 5G and circa 200ns for optimum 
operation.

So I think "the clocks I have in routers" is a statement that very much 
depends on where in the network you are, and what the primary 
application of that network domain is.

However, if 5G becomes the dominate network use, as some predict, the 
trend is surely to the pervasive availability of accurate clocks in 
network fragments that need them.

- Stewart