Albertson
>> Reply-To: "Enhanced Machine Controller (EMC)"
>>
>> To: "Enhanced Machine Controller (EMC)"
>> Subject: Re: [Emc-users] following along in my what if musings about ther new
>> oramge pi 2e
>>
>> Does anyone here know
On Tue, 25 Oct 2016, Chris Albertson wrote:
> Date: Tue, 25 Oct 2016 22:12:14 -0700
> From: Chris Albertson
> Reply-To: "Enhanced Machine Controller (EMC)"
>
> To: "Enhanced Machine Controller (EMC)"
> Subject: Re: [Emc-users] following alon
So you found a dropped packet on one particular combination of
hardware/software some time ago. Bugs get fixed (and yes, new ones
sometimes introduced.) LinuxCNC has had bugs. Doesn't mean that a PC/RTOS
has no business running a machine. There are no collisions on full duplex
ethernet as its n
On 10/26/2016 01:12 AM, Chris Albertson wrote:
> Does anyone here know of one verified case where a packet was dropped by a
> switch? This just does not happen
>
> Also, if you place a second Ethernet dongle on the Pi, the dongle and the
> built-in port share a serial bus. This is not really an
Real-Time is never defined as "now" you can't have that. Even if I place
a pulse in a wire it takes time to come out the other end. Yes, seriously
the speed of light delay through a cable is easy to measure with modest
equipment. I have an application here at home were I measure and account
f
Does anyone here know of one verified case where a packet was dropped by a
switch? This just does not happen
Also, if you place a second Ethernet dongle on the Pi, the dongle and the
built-in port share a serial bus. This is not really an issue but it you
don't like the idea of a multiplexed bu
> ...
> Initiallly the hm2_eth driver provided no good recovery from dropped packets
> (it would hang for 100s of MS and cause a cascade of linuxcnc errors) but the
> errors occurred so seldomly that they were not a real problem (One test
> system
> had more than a year of uptime 24/7 at a 4 KH
On Tue, 25 Oct 2016, Stephen Dubovsky wrote:
> Date: Tue, 25 Oct 2016 14:40:46 -0400
> From: Stephen Dubovsky
> Reply-To: "Enhanced Machine Controller (EMC)"
>
> To: "Enhanced Machine Controller (EMC)"
> Subject: Re: [Emc-users] following alon
On Tue, 25 Oct 2016 12:33:57 -0600
Charles Buckley wrote:
> I work in an environment at work where we do a lot of video broadcast over
> IP. That is all UDP multicast. Luckily, it is an environment where single
> dropped packet only corrupts that frame and section and is recovered the
> next base
All switches do at least store and forward today. Even the $20 cheap
ones. We use ethernet for real time control in some of our products.
Faster loop time than LinuxCNC. We use raw ethernet frames so that we
don't even need the ethernet stack (no DNS/etc needed either.) We also run
web services
I work in an environment at work where we do a lot of video broadcast over
IP. That is all UDP multicast. Luckily, it is an environment where single
dropped packet only corrupts that frame and section and is recovered the
next base frame (ie, anywhere from 1 to 16 frames).
The reason we use UDP in
On 10/25/2016 01:46 PM, Chris Albertson wrote:
> I hate to say it but, a lot of old wives tales here. What is the
> latency added by a cut through switch? It's the packet header length
> divided by the Ethernet bit rate. If you are worried about this kind
> of stuff them you might as well start
I hate to say it but, a lot of old wives tales here. What is the
latency added by a cut through switch? It's the packet header length
divided by the Ethernet bit rate. If you are worried about this kind
of stuff them you might as well start using shortened cables and wire
because of speed or li
> ...
> A queue is not real time. Real time is *now* not when the queue decides
> to send. Losing packets in a critical environment is not a good thing.
Real time is usually within a certain time span, for example buffer half full
so it must be emptied before full.
> Let's suppose a limit i
Because collisions do happen on modern switches, and using UDP with no
error correction in the protocol would cause those packets involved in a
collision to be dropped. Switches are another layer of complexity,
latency and expense when a dual port NIC is the cheapest and most
reliable way to go
On 10/25/2016 12:52 PM, Chris Albertson wrote:
> Are you still certain you need two Ethernet ports? I can't see why
> you need two on a modern switched network.
>
> On Mon, Oct 24, 2016 at 7:05 PM, Mark Johnsen wrote:
>> On Mon, Oct 24, 2016 at 6:52 PM, Gene Heskett wrote:
>>
>>> 1. someone sai
My guess is that people are reading 20 year old information, using two
ports and
sure enough it works just fine. So they claim "I used two ports and it worked"
so the next person does the same and no one thinks about "why".
On Mon, Oct 24, 2016 at 7:42 PM, Stephen Dubovsky wrote:
> Why would UDP
On 10/25/2016 12:16 PM, Nicklas Karlsson wrote:
>> True dat. But why take the chance and not use a direct connection with
>> a cross-over cable? Typical UDP traffic in a switched LAN is fairly
>> fast but not necessarily totally reliable. And over the years I've seen
>> plenty of collisions on a
Are you still certain you need two Ethernet ports? I can't see why
you need two on a modern switched network.
On Mon, Oct 24, 2016 at 7:05 PM, Mark Johnsen wrote:
> On Mon, Oct 24, 2016 at 6:52 PM, Gene Heskett wrote:
>
>> 1. someone said the 7i92H needs its own dedicated ethernet port,
>> pre
> True dat. But why take the chance and not use a direct connection with
> a cross-over cable? Typical UDP traffic in a switched LAN is fairly
> fast but not necessarily totally reliable. And over the years I've seen
> plenty of collisions on a switched network for both TCP and UDP. The
> d
On 10/25/2016 11:26 AM, Przemek Klosowski wrote:
> On Mon, Oct 24, 2016 at 10:42 PM, Stephen Dubovsky
> wrote:
>> Why would UDP need resends on a shared ethernet port? There are no
>> collisions on a full-duplex port & switch (which is pretty much ALL of them
>> now-a-days.) Passive hubs went t
On Mon, Oct 24, 2016 at 11:18 PM, Chris Albertson
wrote:
> Let's say we have two computers and each is sending UDP packets to two
> different Mesa cards. I can't see how those packets would ever be on
> the same physical cable, assuming a switched network. Each computer
> has its own cable to
On Mon, Oct 24, 2016 at 10:42 PM, Stephen Dubovsky wrote:
> Why would UDP need resends on a shared ethernet port? There are no
> collisions on a full-duplex port & switch (which is pretty much ALL of them
> now-a-days.) Passive hubs went the way of the dodo.
Of course, but you are assuming an i
On 10/25/2016 10:18 AM, Stephen Dubovsky wrote:
> Im fully aware UDP doesn't resend. But there are no collisions on modern
> ethernet LANs. No more reason a UDP packet would be corrupted going
> through a (shared) switch as a direct connection.
True dat. But why take the chance and not use a di
Im fully aware UDP doesn't resend. But there are no collisions on modern
ethernet LANs. No more reason a UDP packet would be corrupted going
through a (shared) switch as a direct connection.
On Tue, Oct 25, 2016 at 8:23 AM, Mark wrote:
> On 10/24/2016 10:42 PM, Stephen Dubovsky wrote:
> > Why
On 10/24/2016 10:42 PM, Stephen Dubovsky wrote:
> Why would UDP need resends on a shared ethernet port? There are no
> collisions on a full-duplex port & switch (which is pretty much ALL of them
> now-a-days.) Passive hubs went the way of the dodo.
UDP won't, and can't do resends. Unlike TCP th
The 7i90hd might work for you. It uses SPI, not Ethernet. SPI is
about as fast as Ethernet
I am trying to figure out how a UDP packet might get "walked on" in a
modern Ethernet network. Back in the days of un-switched networks
that used either 10BaseT hubs (hubs not switches) or that used coa
Why would UDP need resends on a shared ethernet port? There are no
collisions on a full-duplex port & switch (which is pretty much ALL of them
now-a-days.) Passive hubs went the way of the dodo.
On Mon, Oct 24, 2016 at 10:22 PM, Gene Heskett wrote:
> On Monday 24 October 2016 22:05:47 Mark Jo
It absolutely requires its own ethernet port, no router either. That's
because it's a realtime device and having to arbitrate would only make
unpredictable latency/jitter.
Like others are saying, the link for accessing your LAN probably won't
even suffer if you use wifi and a USB2.0.
I just us
On Monday 24 October 2016 22:05:47 Mark Johnsen wrote:
> On Mon, Oct 24, 2016 at 6:52 PM, Gene Heskett
wrote:
> > Greetings guys; I hope everyone has arrived back home without
> > incidents involving bent sheet metal or worse.
> >
> > 1. someone said the 7i92H needs its own dedicated ethernet po
On Mon, Oct 24, 2016 at 6:52 PM, Gene Heskett wrote:
> Greetings guys; I hope everyone has arrived back home without incidents
> involving bent sheet metal or worse.
>
> 1. someone said the 7i92H needs its own dedicated ethernet port,
> presumably because udp patckets are not subject to any attem
Greetings guys; I hope everyone has arrived back home without incidents
involving bent sheet metal or worse.
1. someone said the 7i92H needs its own dedicated ethernet port,
presumably because udp patckets are not subject to any attempts at error
correction resends if other traffic walks on a u
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