From Newsgroup: uk.comp.sys.mac

I have a Mac Mini connected to my router by Ethernet and running OS
10.15.7 I have noticed the data lights flashing occasionally when no information ought to be passing but I have always assumed this is just
some sort of handshake.

This evening I noticed that a large amount of data seemed to be
streaming continuously through, when there was definitely no need for
it. Pulling the Ethernet plug out of the Mini stopped it. I tried
shutting down Firefox, as I assumed one of the webpages was doing
something I hadn't agreed to - but this didn't stop it.

As far as I know, there is no other program running, so it must be the
Mini's OS which is passing all this data. Theredoesn't seem to be a
reason for it to do anything like that, so how can I stop it without disconnecting Ethernet ?

A further note: the Ethernet is shared with a Beige Mac G3 and pages can
be sent from this to the printer about 10 times faster when the Mini is disconneted, even when it doesn't appear to be sending any data.
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

In article <1rsc77l.cgennej0v0j4N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

As far as I know, there is no other program running, so it must be the
Mini's OS which is passing all this data. Theredoesn't seem to be a
reason for it to do anything like that, so how can I stop it without >disconnecting Ethernet ?

There's so much random stuff going on on a Mac these days that it's
hard to tell what's causing the problem. Activity Monitor has a
Network tab that may be helpful.

A further note: the Ethernet is shared with a Beige Mac G3 and pages can
be sent from this to the printer about 10 times faster when the Mini is >disconneted, even when it doesn't appear to be sending any data.

Shared in what sense? Wired to a switch? Wireless?

-- Richard
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:

In article <1rsc77l.cgennej0v0j4N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

[...]

A further note: the Ethernet is shared with a Beige Mac G3 and pages can
be sent from this to the printer about 10 times faster when the Mini is >disconneted, even when it doesn't appear to be sending any data.

Shared in what sense? Wired to a switch? Wireless?

Wired to a switch (or hub?).
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

I have a Mac Mini connected to my router by Ethernet and running OS
10.15.7 I have noticed the data lights flashing occasionally when no information ought to be passing but I have always assumed this is just
some sort of handshake.

This evening I noticed that a large amount of data seemed to be
streaming continuously through, when there was definitely no need for
it. Pulling the Ethernet plug out of the Mini stopped it. I tried
shutting down Firefox, as I assumed one of the webpages was doing
something I hadn't agreed to - but this didn't stop it.

IrCOd say thatrCOs fairly normal. IrCOve previously used a couple of usb-Ethernet
dongles, with the lights on them, and they flashed pretty continuously when connected. That was on the old MacBook Pro, and also on my IPad Pro, when
IrCOd mounted it on the desktop stand.

As far as I know, there is no other program running, so it must be the
Mini's OS which is passing all this data. Theredoesn't seem to be a
reason for it to do anything like that, so how can I stop it without disconnecting Ethernet ?

ThererCOs plenty of stuff going on in the background, and as you say, some handshakes too probably.

Of course IrCOm expecting it myself, my setup is using extensive iCloud data, and a lot of home networking going on too.

Even then, I suspect thererCOs things like Bonjour looking for any devices, printers, other Macs and such like.

I think your only chance is to monitor the stream, and maybe try
firewalling it perhaps (donrCOt know, itrCOs just a thought). Can you run any of the Objective-See stuff, he has some decent tools there that might help, although I suspect your OSs are too old. Lulu and Netiquette there might be
a good start.

https://objective-see.org/tools.html

A further note: the Ethernet is shared with a Beige Mac G3 and pages can
be sent from this to the printer about 10 times faster when the Mini is disconneted, even when it doesn't appear to be sending any data.

Maybe one of the devices is dropping the speed of the hub/switch. I know
some do drop to the speed of the slowest device connected to it. Perhaps a dodgy cable, or a fault in an Ethernet port? Try a new cable, or perhaps
just try a different port in the switch. That might possibly be triggering
a continuous handshake process.

IrCOve got nothing more than that really, just some things IrCOd try myself. Otherwise it sounds fairly normal to me. Apart from the speed issue.
--
Andy H
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

Andy H <thewildrover@icloud.com> wrote:

[...]

Even then, I suspect thererCOs things like Bonjour looking for any devices, printers, other Macs and such like.

The irony is that the Mini won't connect to any of the other devices, I
have to communicate between the two machines by e-mail or USB stick. It identifies that the printer is connected but won't send anything to it.
(The printer uses PostScript, so it should be compatible with most
computers.)

[...]

Maybe one of the devices is dropping the speed of the hub/switch. I know
some do drop to the speed of the slowest device connected to it.

The hub lights flash less frequently with long gaps between flashes.
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

In article <1rscco1.1awc4mz1mbru5bN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

A further note: the Ethernet is shared with a Beige Mac G3 and pages can
be sent from this to the printer about 10 times faster when the Mini is
disconneted, even when it doesn't appear to be sending any data.

Shared in what sense? Wired to a switch? Wireless?

Wired to a switch (or hub?).

If it's really a hub, I've no idea how they handle the combination of
speeds. What ethernet speed do the Macs report when both or singly
connected? (Under Settings / Network / Ethernet / Details /
Hardware on a recent Mac).

-- Richard
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

Andy H <thewildrover@icloud.com> wrote:

[...]

Even then, I suspect there|o-C-Os things like Bonjour looking for any devices,
printers, other Macs and such like.

The irony is that the Mini won't connect to any of the other devices, I
have to communicate between the two machines by e-mail or USB stick. It identifies that the printer is connected but won't send anything to it.
(The printer uses PostScript, so it should be compatible with most computers.)

[...]

Maybe one of the devices is dropping the speed of the hub/switch. I know
some do drop to the speed of the slowest device connected to it.

The hub lights flash less frequently with long gaps between flashes.

Ok, maybe just try cable or port swapping? ItrCOs a bit of a guess, but itrCOs surprising how often problems are just down to a dicky cable.

Otherwise, I guess, as others have said, yourCOve got to start digging into logs and data.

However, I always start with the easiest, and cheapest, things to try first
- such as swap the cables - even between the two devices there, if the
problem remains, then itrCOs not that, if it moves to the other device, then
a good chance it is. Then try another switch/hub port. Check software
settings - are they all using the same setup? (Network settings, Privacy settings, Sharing settings, Firewall settings for a start - try comparing
each device).

Not sure about older OSs, but if you can, perhaps try resetting the Network settings and start again, even the old PRAM reset at startup. Try running
in rCySaferCO mode, it might indicate a software issue if it works okay in that.

But do one thing at a time, so you know what fixed it!

TheyrCOre just things to try that cost nothing, other than some time -
although it could be worth it to save the faffing about you have now! ;-)
--
Andy H
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

Richard Tobin wrote:

[snip]

Wired to a switch (or hub?).

If it's really a hub, I've no idea how they handle the combination of
speeds. What ethernet speed do the Macs report when both or singly connected? (Under Settings / Network / Ethernet / Details /
Hardware on a recent Mac).

I don't think hubs exist any more. They implement the same protocol as
thick Ethernet (10base5) i.e. CSMA/CD which only works at one speed (10 Mbits/sec). Some hubs carried a BNC connector for Thin Ethernet
(10base2).

Early switches only operated at 10MBits/sec but they all work by store-and-forward, which means that packets are received on one port,
stored, and sent out of one or all the others according to the table of
MAC address to physical ports that the device learns.
--
Graham J
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

On 21/03/2026 20:41, Richard Tobin wrote:

In article<1rsc77l.cgennej0v0j4N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham<liz@poppyrecords.invalid.invalid> wrote:

As far as I know, there is no other program running, so it must be the
Mini's OS which is passing all this data. Theredoesn't seem to be a
reason for it to do anything like that, so how can I stop it without
disconnecting Ethernet ?

There's so much random stuff going on on a Mac these days that it's
hard to tell what's causing the problem. Activity Monitor has a
Network tab that may be helpful.

There is also "Little Snitch". <https://www.obdev.at/products/littlesnitch/index.html>

It costs money but the free trial should run for long enough for you to
to work out what is happening.
--
Bruce Horrocks
Hampshire, England
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:

In article <1rscco1.1awc4mz1mbru5bN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

A further note: the Ethernet is shared with a Beige Mac G3 and pages can >> >be sent from this to the printer about 10 times faster when the Mini is >> >disconneted, even when it doesn't appear to be sending any data.

Shared in what sense? Wired to a switch? Wireless?

Wired to a switch (or hub?).

If it's really a hub, I've no idea how they handle the combination of
speeds.

It is a Miri 10T/B with a Canon Postscript printer, a HP LaseJet 6mp
printer (via an Asanto adaptor), a Beige G3 (OS8.6), a MacMini (OS
10.15.7), an Ethernet cable to the router in an adjacent room and an
Ethernet cable to another 'hub' in another part of the house (with other
G2s connected but not currently switched on).

What ethernet speed do the Macs report when both or singly
connected? (Under Settings / Network / Ethernet / Details /
Hardware on a recent Mac).

I don't know because I haven't looked into how they report speeds and
the pathway you describe isn't available on either of my machines.
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

On 23 Mar 2026 at 10:54:19rC>pm GMT, "Bruce" <07.013@scorecrow.com> wrote:

On 21/03/2026 20:41, Richard Tobin wrote:

In article<1rsc77l.cgennej0v0j4N%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham<liz@poppyrecords.invalid.invalid> wrote:

As far as I know, there is no other program running, so it must be the
Mini's OS which is passing all this data. Theredoesn't seem to be a
reason for it to do anything like that, so how can I stop it without
disconnecting Ethernet ?

There's so much random stuff going on on a Mac these days that it's
hard to tell what's causing the problem. Activity Monitor has a
Network tab that may be helpful.

There is also "Little Snitch". <https://www.obdev.at/products/littlesnitch/index.html>

It costs money but the free trial should run for long enough for you to
to work out what is happening.

There's also Tiny Shield (cheaper), Radio Silence (much cheaper) or Lulu (free).
--
Cheers ... Mark
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

In article <1rsgvit.vjcnxjo9ol8uN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

It is a Miri 10T/B

That sounds like a 10Mb/s combined coax / twisted pair device, which
would be limited to 1/100 the speed of any Mac made in the last 15
years or so. Even your G3 is 10 times faster than that.

-- Richard
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:

In article <1rsgvit.vjcnxjo9ol8uN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

It is a Miri 10T/B

That sounds like a 10Mb/s combined coax / twisted pair device, which
would be limited to 1/100 the speed of any Mac made in the last 15
years or so. Even your G3 is 10 times faster than that.

When it works properly, it is as fast as I need. (Yes, it does have a
BNC connector for co-ax.)

I have found that re-booting it occasionally will increase the speed.
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

On 24/03/2026 12:17, Liz Tuddenham wrote:

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:

In article <1rsgvit.vjcnxjo9ol8uN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

It is a Miri 10T/B

That sounds like a 10Mb/s combined coax / twisted pair device, which
would be limited to 1/100 the speed of any Mac made in the last 15
years or so. Even your G3 is 10 times faster than that.

When it works properly, it is as fast as I need. (Yes, it does have a
BNC connector for co-ax.)

Do you have anything that is coax, or are all your devices rj45 connectors?

I have found that re-booting it occasionally will increase the speed.

I am guessing that this really is a hub, not a switch, so everything is
forced down to 10Mb/s and the network is broadcast, not switched. To me
it sounds like the mini is a tad unhappy going this slow so is flooding
the network trying to get things to talk to it with the resultant
clashes that then kill everything. So no mystery data stream, rather a broadcast storm.

If you don't have any coax devices I would buy an 8 port ethernet switch (around -u20). This will almost certainly fix things all by itself, but
if not, the port lights on the switch will tell you what is involved in
the network chat.
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

David Sankey <David.Sankey@stfc.ac.uk> wrote:

On 24/03/2026 12:17, Liz Tuddenham wrote:

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:

In article <1rsgvit.vjcnxjo9ol8uN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

It is a Miri 10T/B

That sounds like a 10Mb/s combined coax / twisted pair device, which
would be limited to 1/100 the speed of any Mac made in the last 15
years or so. Even your G3 is 10 times faster than that.

When it works properly, it is as fast as I need. (Yes, it does have a
BNC connector for co-ax.)

Do you have anything that is coax, or are all your devices rj45 connectors?

Nothing connected to the co-ax connector

I have found that re-booting it occasionally will increase the speed.

I am guessing that this really is a hub, not a switch, so everything is forced down to 10Mb/s and the network is broadcast, not switched. To me
it sounds like the mini is a tad unhappy going this slow so is flooding
the network trying to get things to talk to it with the resultant
clashes that then kill everything. So no mystery data stream, rather a broadcast storm.

That sounds like a good explanation - although the yellow light, which indicates data clashes, rarely operates.

If you don't have any coax devices I would buy an 8 port ethernet switch (around -u20). This will almost certainly fix things all by itself, but
if not, the port lights on the switch will tell you what is involved in
the network chat.

I may have one somewhere in the junk box but the current installation is
a bit physically 'permanant', so I am reluctant to mess about with it.
--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
--- Synchronet 3.21f-Linux NewsLink 1.2

From Newsgroup: uk.comp.sys.mac

On 25/03/2026 08:43, Liz Tuddenham wrote:

David Sankey <David.Sankey@stfc.ac.uk> wrote:

On 24/03/2026 12:17, Liz Tuddenham wrote:

Richard Tobin <richard@cogsci.ed.ac.uk> wrote:

In article <1rsgvit.vjcnxjo9ol8uN%liz@poppyrecords.invalid.invalid>,
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

It is a Miri 10T/B

That sounds like a 10Mb/s combined coax / twisted pair device, which
would be limited to 1/100 the speed of any Mac made in the last 15
years or so. Even your G3 is 10 times faster than that.

When it works properly, it is as fast as I need. (Yes, it does have a
BNC connector for co-ax.)

Do you have anything that is coax, or are all your devices rj45 connectors?

Nothing connected to the co-ax connector

I have found that re-booting it occasionally will increase the speed.

I am guessing that this really is a hub, not a switch, so everything is
forced down to 10Mb/s and the network is broadcast, not switched. To me
it sounds like the mini is a tad unhappy going this slow so is flooding
the network trying to get things to talk to it with the resultant
clashes that then kill everything. So no mystery data stream, rather a
broadcast storm.

That sounds like a good explanation - although the yellow light, which indicates data clashes, rarely operates.

That just means collisions aren't occurring, but as it's a shared
channel, there is no bandwidth available as the thrashing goes on. Have
a peek at <https://en.wikipedia.org/wiki/Carrier-sense_multiple_access_with_collision_detection>

Rather than rebooting, you might just try unplugging and replugging the ethernet cable on the mini (either end of the cable) as this will force
a reset of that link.

If you don't have any coax devices I would buy an 8 port ethernet switch
(around |e-u20). This will almost certainly fix things all by itself, but >> if not, the port lights on the switch will tell you what is involved in
the network chat.

I may have one somewhere in the junk box but the current installation is
a bit physically 'permanant', so I am reluctant to mess about with it.

Your call, but this is the first thing that I would change here. Hubs
really are history!
--- Synchronet 3.21f-Linux NewsLink 1.2