[RndTbl] Looking for PTP aware switch

Adam Thompson athompso at athompso.net
Mon Dec 2 12:39:18 CST 2019

On 2019-12-02 11:42, Gerald Brandt wrote:
> Hi,
> I'm looking for an IEEE 1588v2/PTP aware switch. Looking around, I've
> found several ruggadized ones and a couple in office types. I only
> need something for use in office, and something with 16 or 24 GigE
> ports would work.
> The ones I've found are pretty expensive, considering we would need 4 
> of them.

Yes, PTP support is generally limited to Enterprise / Industrial / ISP 
grade equipment.  Some of which can be found used, if you're willing to 
go that route.

Otherwise, have a look at:

and this fellow's experience, which seems to mirror yours:

I can tell you from direct experience that the two lists I linked above 
are FAR from comprehensive.  You can, with a bit of work, find pages 
like this: 
from each major vendor.

An alternative is to use a cheap server (Atom-based is fine) with two 
server-class NICs in it, and run a PTP bridge, see below.

Also, if there's a straight layer-2 path from the end station that 
consumes PTP time, to the Grandmaster, the intermediate switches DO NOT 
have to be PTP boundary clocks.  The PTP protocol can compensate for 
non-PTP transparent switches/bridges between the consumer and the 
Grandmaster.  You can lose a small amount of accuracy (sub-millisecond) 
but that's still good enough for many/most scenarios.  NOTE: this is not 
a guarantee; YMMV; circumstances may vary.

Where you would need a Boundary Clock is, for example, to retransmit PTP 
time onto a different VLAN than you received it on.  This is, AFAICT, 
why PTP-capable switches exist... you'll note that most PTP-capable 
products are high-end because they're actually *routing* switches, and 
the L2 path to the Grandmaster is broken when you cross a router hop.  
That's where a cheap server can come in handy, it can rebroadcast PTP 
time received on one VLAN onto others.  Again, you'll lose accuracy & 
precision simultaneously (no more 5ns sync!) but you'll get something.

Finally, the $64,000 question would be why you need to use PTP in the 
first place?  Properly configured NTP can keep (non-Windows) systems in 
sync to within about 3msec on a LAN, including local router hops.  The 

I'm pushing to get PTP capability at MBIX, but that's because I already 
happen to run mostly PTP-capable gear, it doesn't add much to MBIX's 
cost, so hey why not!  MBIX members wouldn't be required to get 
PTP-capable equipment: if this happens, I think it would just be a thing 
that's magically available on the IX fabric if your gear knows how to 
listen for it.  I think.


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