How ethernet switch is work?

Thread Starter

Nandish

Joined Nov 28, 2016
3
Hi,

I have seen many videos in youtube regarding Ethernet Switch functionality. I understand that video well. But still i have a query. I have FPGA Based hardware for Power Electronics control application and in that board having Ethernet connectivity. I have successfull in Modbus TCP/IP to interface with HMI for Human Interface. Now i want to connect multiple HMI's and Energy meters through Ethernet Switch creating local network. My FPGA Hardware is act as Server.

My questions is, How the ethernet switch will work when two clients will send request to Server at the same time?

Regards,
Nandish Jasani.
 

andrewmm

Joined Feb 25, 2011
399
Well assume IP V4 here, and a none managed network ( most small ones fall into the category )


The switch, is a self learning unit.

Each and every Ethernet end point, will as you have read, have a unique MAC address.
each and every Ethernet system, as you also know , has a means of assigning every end point on the network a unique IP address.

Each and every packet of data sent over the Ethernet, contains a header, that states which ip its from and which ip its going to.

The switch, starts out with know knowledge of what Ip is on each of its ports,
so initially it sends all packets it receives out to all ports. The switch , mainly by listening to packets, learns which ports which IP addresses should be sent to, and over time, if it receives a packet for a particular Ip address it knows about, only sends out on the port that has that Ip on.

Its not perfect, and there are rules for the switch to keep a track of things, and account for things being disconnected and re added, and rules that allow packets to be broadcast to all ports, or even a sub set of ports, but thats the icing on the cake.
 

panic mode

Joined Oct 10, 2011
1,837
switch simply directs traffic... it will collect packets from both clients and send them all to server. server need to keep track of each connected client and respond to their requests accordingly.
 

WBahn

Joined Mar 31, 2012
25,918
My questions is, How the ethernet switch will work when two clients will send request to Server at the same time?
There's really no such that as "at the same time" in practical terms.

Each port will have some kind of memory, likely a queue, and the controller will pull from the queues, possibly in a round robin fashion. So even if you try get two packets to arrive at exactly the same time, they will end up in a train of packets. More importantly, there is the possibility that the packet that arrived first may actually end up behind a packet that arrived at another port later. Higher level protocols deal with the ordering issue.

Now, if you are talking about a connection in which both clients are using the same transmission medium, then the protocol deals with this by either assigning transmission windows to each device or by detecting collisions when they occur and having both devices randomly backoff and wait to try again. Again, packets can end up out of order.
 

BobaMosfet

Joined Jul 1, 2009
1,121
Hi,

I have seen many videos in youtube regarding Ethernet Switch functionality. I understand that video well. But still i have a query. I have FPGA Based hardware for Power Electronics control application and in that board having Ethernet connectivity. I have successfull in Modbus TCP/IP to interface with HMI for Human Interface. Now i want to connect multiple HMI's and Energy meters through Ethernet Switch creating local network. My FPGA Hardware is act as Server.

My questions is, How the ethernet switch will work when two clients will send request to Server at the same time?

Regards,
Nandish Jasani.
Like the rest of us did:

The TCP/IP Guide: A Comprehensive, Illustrated Internet Protocols Reference 1st Edition
Author: Charles M. Kozierok
ISBN-13: 978-1593270476
ISBN-10: 159327047X
 

eetech00

Joined Jun 8, 2013
1,940
Hi,

I have seen many videos in youtube regarding Ethernet Switch functionality. I understand that video well. But still i have a query. I have FPGA Based hardware for Power Electronics control application and in that board having Ethernet connectivity. I have successfull in Modbus TCP/IP to interface with HMI for Human Interface. Now i want to connect multiple HMI's and Energy meters through Ethernet Switch creating local network. My FPGA Hardware is act as Server.

My questions is, How the ethernet switch will work when two clients will send request to Server at the same time?

Regards,
Nandish Jasani.
study the OSI model to understand how a switch “fits” in structured networks. When asking about ethernet switches, you need to qualify the type of switch.
Todays ethernet switches are multi-layered but fundamentally function at layer 2. As such, they have know no knowledge and do not manipulate IP addresses. The are responsible for forwarding “ethernet frames” and do so by reading the source and destination MAC address contained in ethernet frames.
 
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