Collision Domain - In POS
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@brianlittlejohn said in Collision Domain - In POS:
On switches you can't have a collision, they are layer 2 devices with queues. Collision domains were a problem back in the day of hubs because 2 devices could send at the same time. Hubs operated on layer 1 and you would split collision domains with a device called a bridge, it would take packets and store and forward them between the collision domains. A switch is just a multiport bridge, each connection on a switch is its own collision domain since the device will store and forward for each segment.
Odds are your issue are a cabling issue, or a bad NIC on the server, or a bad switch/port on switch somewhere.
It also could be a software issue on the server causing the issues.
Right - The reason I was under the impression it's a collision domain issue is there's one Port being used by all of the terminals that connect to the Server, So even if switches that connect the terminal on the front of house act as a bridge, it's still sending all the information back and forth to the terminals on One line..
Maybe I'm not understanding my own thoughts here.
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One port isn't an issue unless you are saturating that one line, also it is all going down to one line when it goes to the server. If you saturate more than the switch can store and forward it drops the frame. It would be odd if that was the case giving the small number of devices running on the network. I would check and make sure the switches connected to each other are both negotiating at the full speed of the switch e.g. gigabit if it is a gigabit switch.
Does the tablet freeze up as well when the other machines do? If so, i would look at the switch in the back as the issue or the line going to the server.
If it is just the front machines, it may be an issue with the line itself, or the first switch in the bar.
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@brianlittlejohn said in Collision Domain - In POS:
One port isn't an issue unless you are saturating that one line, also it is all going down to one line when it goes to the server. If you saturate more than the switch can store and forward it drops the frame. It would be odd if that was the case giving the small number of devices running on the network. I would check and make sure the switches connected to each other are both negotiating at the full speed of the switch e.g. gigabit if it is a gigabit switch.
Does the tablet freeze up as well when the other machines do? If so, i would look at the switch in the back as the issue or the line going to the server.
If it is just the front machines, it may be an issue with the line itself, or the first switch in the bar.
They're Plug and Play Gigabit Switches from Cisco on the front and a plug and play D-link gigabit switch in the back .
Tablet does not freeze up while the other terminals do from my understanding - but it's also routed from the firewall to the port that feeds into the switch..
Just replaced the first switch in the bar a week ago and it didn't help with the issue.
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@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
On switches you can't have a collision, they are layer 2 devices with queues. Collision domains were a problem back in the day of hubs because 2 devices could send at the same time. Hubs operated on layer 1 and you would split collision domains with a device called a bridge, it would take packets and store and forward them between the collision domains. A switch is just a multiport bridge, each connection on a switch is its own collision domain since the device will store and forward for each segment.
Odds are your issue are a cabling issue, or a bad NIC on the server, or a bad switch/port on switch somewhere.
It also could be a software issue on the server causing the issues.
Right - The reason I was under the impression it's a collision domain issue is there's one Port being used by all of the terminals that connect to the Server, So even if switches that connect the terminal on the front of house act as a bridge, it's still sending all the information back and forth to the terminals on One line..
Maybe I'm not understanding my own thoughts here.
Your problem is that you're learning obsolete information. All these Network+, Security+, etc. are filled with information that was relevant in 80's or earlier. Instead of relaying on that, use your brain. Can POS terminals be sending so much data that they saturate 1Gbit network? Or even 100Mbit? Highly unlikely. So faulty hardware or software is your most likely problem.
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@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
One port isn't an issue unless you are saturating that one line, also it is all going down to one line when it goes to the server. If you saturate more than the switch can store and forward it drops the frame. It would be odd if that was the case giving the small number of devices running on the network. I would check and make sure the switches connected to each other are both negotiating at the full speed of the switch e.g. gigabit if it is a gigabit switch.
Does the tablet freeze up as well when the other machines do? If so, i would look at the switch in the back as the issue or the line going to the server.
If it is just the front machines, it may be an issue with the line itself, or the first switch in the bar.
They're Plug and Play Gigabit Switches from Cisco on the front and a plug and play D-link gigabit switch in the back .
Tablet does not freeze up while the other terminals do from my understanding - but it's also routed from the firewall to the port that feeds into the switch..
Just replaced the first switch in the bar a week ago and it didn't help with the issue.
Can you attach network diagram? My brain is hurting today, I don't want to visualize this network in my head, I'd rather see how it looks.
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@marcinozga said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
On switches you can't have a collision, they are layer 2 devices with queues. Collision domains were a problem back in the day of hubs because 2 devices could send at the same time. Hubs operated on layer 1 and you would split collision domains with a device called a bridge, it would take packets and store and forward them between the collision domains. A switch is just a multiport bridge, each connection on a switch is its own collision domain since the device will store and forward for each segment.
Odds are your issue are a cabling issue, or a bad NIC on the server, or a bad switch/port on switch somewhere.
It also could be a software issue on the server causing the issues.
Right - The reason I was under the impression it's a collision domain issue is there's one Port being used by all of the terminals that connect to the Server, So even if switches that connect the terminal on the front of house act as a bridge, it's still sending all the information back and forth to the terminals on One line..
Maybe I'm not understanding my own thoughts here.
Your problem is that you're learning obsolete information. All these Network+, Security+, etc. are filled with information that was relevant in 80's or earlier. Instead of relaying on that, use your brain. Can POS terminals be sending so much data that they saturate 1Gbit network? Or even 100Mbit? Highly unlikely. So faulty hardware or software is your most likely problem.
I dont know why they leave that stuff in there, but, you're right, it's highly unlikely.
gonna have to rethink a few things about the cabling. -
@marcinozga said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
One port isn't an issue unless you are saturating that one line, also it is all going down to one line when it goes to the server. If you saturate more than the switch can store and forward it drops the frame. It would be odd if that was the case giving the small number of devices running on the network. I would check and make sure the switches connected to each other are both negotiating at the full speed of the switch e.g. gigabit if it is a gigabit switch.
Does the tablet freeze up as well when the other machines do? If so, i would look at the switch in the back as the issue or the line going to the server.
If it is just the front machines, it may be an issue with the line itself, or the first switch in the bar.
They're Plug and Play Gigabit Switches from Cisco on the front and a plug and play D-link gigabit switch in the back .
Tablet does not freeze up while the other terminals do from my understanding - but it's also routed from the firewall to the port that feeds into the switch..
Just replaced the first switch in the bar a week ago and it didn't help with the issue.
Can you attack network diagram? My brain is hurting today, I don't want to visualize this network in my head, I'd rather see how it looks.
Give me a few and I'll get one added to the thread.
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@WrCombs said in Collision Domain - In POS:
Just replaced the first switch in the bar a week ago and it didn't help with the issue.
I've seen gigabit switches fail to negotiate speed correctly and had a 10M half duplex link.
Change the port the line from the back to the bar is plugged into on the switches to test out a bad port.
You could also run an iperf test from one of the up front pcs to the server and see what kind of bandwidth you are actually getting to the server.
I would put money on the actual line being damaged somewhere (bad crimp, punchdown)
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@WrCombs said in Collision Domain - In POS:
I'm learning Network+ and during my Videos we came across Collision Domains- Here's why I think this site is using a collision domain:
So just for some terminology.... Ethernet (and wifi) always have a collision domain. But in all modern networks since the advent of switching, the collision domains have only one member so cannot collide with Ethernet.
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@WrCombs said in Collision Domain - In POS:
My thought is The Terminals are sending Packets to the back office to update the trans.log - which is normal- That's what they're supposed to do, but it's all happening at the same time causing collisions on the network.
That's impossible. Collisions cannot exist from lots of traffic on a switches connection.
Collisions can't helped with static items on a conveyor belt, and that's what a switched ethernet setup is.
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@WrCombs said in Collision Domain - In POS:
They are having a huge issue when their busy, and all terminals are in use, where they will start to freeze for a few seconds, its only a problem when they are running more than one terminal on either side of the bar.
If their using 2 terminals on the same side of the bar it runs a little bit faster but there's still a delay.Nothing in a terminal should create even a blip of traffic on a normal network. So while collisions are physical impossible, you are trying to talk about congestion. But there's no way you are getting congestion.
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@WrCombs said in Collision Domain - In POS:
@marcinozga said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
On switches you can't have a collision, they are layer 2 devices with queues. Collision domains were a problem back in the day of hubs because 2 devices could send at the same time. Hubs operated on layer 1 and you would split collision domains with a device called a bridge, it would take packets and store and forward them between the collision domains. A switch is just a multiport bridge, each connection on a switch is its own collision domain since the device will store and forward for each segment.
Odds are your issue are a cabling issue, or a bad NIC on the server, or a bad switch/port on switch somewhere.
It also could be a software issue on the server causing the issues.
Right - The reason I was under the impression it's a collision domain issue is there's one Port being used by all of the terminals that connect to the Server, So even if switches that connect the terminal on the front of house act as a bridge, it's still sending all the information back and forth to the terminals on One line..
Maybe I'm not understanding my own thoughts here.
Your problem is that you're learning obsolete information. All these Network+, Security+, etc. are filled with information that was relevant in 80's or earlier. Instead of relaying on that, use your brain. Can POS terminals be sending so much data that they saturate 1Gbit network? Or even 100Mbit? Highly unlikely. So faulty hardware or software is your most likely problem.
I dont know why they leave that stuff in there, but, you're right, it's highly unlikely.
gonna have to rethink a few things about the cabling.Because it's really important to understand how networks work and why they are the way that they are and how different technologies would work under different conditions. Wifi still works 100% like this, so knowing why it is bad is great. But you need to be aware of where you are applying the knowledge.
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@brianlittlejohn said in Collision Domain - In POS:
On switches you can't have a collision, they are layer 2 devices with queues. Collision domains were a problem back in the day of hubs because 2 devices could send at the same time. Hubs operated on layer 1 and you would split collision domains with a device called a bridge, it would take packets and store and forward them between the collision domains. A switch is just a multiport bridge, each connection on a switch is its own collision domain since the device will store and forward for each segment.
Odds are your issue are a cabling issue, or a bad NIC on the server, or a bad switch/port on switch somewhere.
It also could be a software issue on the server causing the issues.
Worth adding a little colour to this, IMHO...
Not only did a bridge split the collision domains, but a switch is a multiport switch (discussed in another thread.) So moving to "switched Ethernet" as we call it, is when we use zero hubs and use a bridge port for every single device, thereby eliminating all layer 1 devices and taking out all possibilities of collisions.
Originally switches were at the top of your rack and connected many hubs together, so each switch port had its won collision domain of 5-200 devices. But today, we go switch to switch, you can't buy hubs, so the idea of collision domains requires hardware that you can't procure today.
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@marcinozga said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
On switches you can't have a collision, they are layer 2 devices with queues. Collision domains were a problem back in the day of hubs because 2 devices could send at the same time. Hubs operated on layer 1 and you would split collision domains with a device called a bridge, it would take packets and store and forward them between the collision domains. A switch is just a multiport bridge, each connection on a switch is its own collision domain since the device will store and forward for each segment.
Odds are your issue are a cabling issue, or a bad NIC on the server, or a bad switch/port on switch somewhere.
It also could be a software issue on the server causing the issues.
Right - The reason I was under the impression it's a collision domain issue is there's one Port being used by all of the terminals that connect to the Server, So even if switches that connect the terminal on the front of house act as a bridge, it's still sending all the information back and forth to the terminals on One line..
Maybe I'm not understanding my own thoughts here.
Your problem is that you're learning obsolete information. All these Network+, Security+, etc. are filled with information that was relevant in 80's or earlier. Instead of relaying on that, use your brain. Can POS terminals be sending so much data that they saturate 1Gbit network? Or even 100Mbit? Highly unlikely. So faulty hardware or software is your most likely problem.
I've been pretty critical of these certs being obsolete. And generally, I'd agree. But in this case I think understanding Layer 1 devices, especially as they still exist in wireless deployments, is highly worthwhile, even if you can't deploy it in the real world. There are times when theory makes the world easier to understand in the grand scheme.
But yes, common sense says that that itty bitty network traffic can't possible saturate any modern networking gear.
Also, for historical record, in the very early 2000s, hubs were still the standard. Fully switches networks were like 2001 or 2002 that they were more common. In 2004 or so, people were still bragging about having worked on "fully switched Ethernet" instead of having hubs throughout the network, and I was still dealing with customers with hubs deployed well after 2011.
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@WrCombs said in Collision Domain - In POS:
@marcinozga said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
One port isn't an issue unless you are saturating that one line, also it is all going down to one line when it goes to the server. If you saturate more than the switch can store and forward it drops the frame. It would be odd if that was the case giving the small number of devices running on the network. I would check and make sure the switches connected to each other are both negotiating at the full speed of the switch e.g. gigabit if it is a gigabit switch.
Does the tablet freeze up as well when the other machines do? If so, i would look at the switch in the back as the issue or the line going to the server.
If it is just the front machines, it may be an issue with the line itself, or the first switch in the bar.
They're Plug and Play Gigabit Switches from Cisco on the front and a plug and play D-link gigabit switch in the back .
Tablet does not freeze up while the other terminals do from my understanding - but it's also routed from the firewall to the port that feeds into the switch..
Just replaced the first switch in the bar a week ago and it didn't help with the issue.
Can you attack network diagram? My brain is hurting today, I don't want to visualize this network in my head, I'd rather see how it looks.
Give me a few and I'll get one added to the thread.
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@WrCombs said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
@marcinozga said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
@brianlittlejohn said in Collision Domain - In POS:
One port isn't an issue unless you are saturating that one line, also it is all going down to one line when it goes to the server. If you saturate more than the switch can store and forward it drops the frame. It would be odd if that was the case giving the small number of devices running on the network. I would check and make sure the switches connected to each other are both negotiating at the full speed of the switch e.g. gigabit if it is a gigabit switch.
Does the tablet freeze up as well when the other machines do? If so, i would look at the switch in the back as the issue or the line going to the server.
If it is just the front machines, it may be an issue with the line itself, or the first switch in the bar.
They're Plug and Play Gigabit Switches from Cisco on the front and a plug and play D-link gigabit switch in the back .
Tablet does not freeze up while the other terminals do from my understanding - but it's also routed from the firewall to the port that feeds into the switch..
Just replaced the first switch in the bar a week ago and it didn't help with the issue.
Can you attack network diagram? My brain is hurting today, I don't want to visualize this network in my head, I'd rather see how it looks.
Give me a few and I'll get one added to the thread.
this is the Diagram I came up with based on the equipment and the setup. Hopefully gives a rough understanding of what I'm saying -
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So it's not a collision Domain because their Obsolete in wired networks due to switches -
I'm not sure what else could be causing the issue other than bad cabling/ Bad terminals/ Bad switches.
May be worth replacing the other bar switch and changing out the Cabling under the bar. -
@WrCombs said in Collision Domain - In POS:
So it's not a collision Domain because their Obsolete in wired networks due to switches -
I'm not sure what else could be causing the issue other than bad cabling/ Bad terminals/ Bad switches.
May be worth replacing the other bar switch and changing out the Cabling under the bar.So start with the basics and see what you can track down. If you are getting congestion or bad switches / cabling, you'd expect to see it even with a ping. Ping from device to device and see if you ever get latency or drops. If not, likely it's not a networking thing.
Can you describe the freezing? Like if you do X which devices freeze. And if you do Y, these other devices freeze.
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@scottalanmiller said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
So it's not a collision Domain because their Obsolete in wired networks due to switches -
I'm not sure what else could be causing the issue other than bad cabling/ Bad terminals/ Bad switches.
May be worth replacing the other bar switch and changing out the Cabling under the bar.So start with the basics and see what you can track down. If you are getting congestion or bad switches / cabling, you'd expect to see it even with a ping. Ping from device to device and see if you ever get latency or drops. If not, likely it's not a networking thing.
Can you describe the freezing? Like if you do X which devices freeze. And if you do Y, these other devices freeze.
Only information I have is " when we're Busy, and we try to order items on the terminals they run slow and freeze up. then it comes back then it shows up. the delay is anywhere from 15 seconds to 2 minutes"
Nothing specific when it comes to what their doing on the terminals. -
@WrCombs said in Collision Domain - In POS:
@scottalanmiller said in Collision Domain - In POS:
@WrCombs said in Collision Domain - In POS:
So it's not a collision Domain because their Obsolete in wired networks due to switches -
I'm not sure what else could be causing the issue other than bad cabling/ Bad terminals/ Bad switches.
May be worth replacing the other bar switch and changing out the Cabling under the bar.So start with the basics and see what you can track down. If you are getting congestion or bad switches / cabling, you'd expect to see it even with a ping. Ping from device to device and see if you ever get latency or drops. If not, likely it's not a networking thing.
Can you describe the freezing? Like if you do X which devices freeze. And if you do Y, these other devices freeze.
Only information I have is " when we're Busy, and we try to order items on the terminals they run slow and freeze up. then it comes back then it shows up. the delay is anywhere from 15 seconds to 2 minutes"
Nothing specific when it comes to what their doing on the terminals.Any reason that there is a network suspicion then, why not suspect the server?
