Why TCP / IP is not use in fieldbus?

Hello everyone.
I'm studying industrial engineering; For a course in industrial communication, I must answer this question:
Why TCP / IP is little or not use in fieldbus? In witch case is TCP/IP protocol use in fieldbus?
Could someone give me a begin of answer?

TCP/IP is in use and is becoming more popular.
you need to look at the many comms. system histories.
Also the many types and stability of the various Fieldbus systems.
The current required at the remote locations
the number of conducters and availability of power.
E/net can not supply remote device power.
The requirements for safety bus systems

Actually there is standard for power over ethernet.

Ethernet in itself is used in many fieldbuses, like ethercat, profinet etc. But TCP is protocol stack, its slow and heavy one. So most do replace it with something else.

So study what TCP/IP actually is, then study few ethernet based fieldbuses and then compare them and advantages over TCP and you should be able to get the answer.

azertyx said:

Hello everyone.
I'm studying industrial engineering; For a course in industrial communication, I must answer this question:
Why TCP / IP is little or not use in fieldbus? In witch case is TCP/IP protocol use in fieldbus?
Could someone give me a begin of answer?

Click to expand...

1. TCP/IP is actually in wide use in fieldbus applications 2. TCP/IP (speaking generically) is not deterministic, which means that there is no guarantee of packets getting from source to destination in a timely fashion. This can be a concern for high-speed applications. For most applications though this detail is not a concern since (a) Ethernet is very very fast and (b) unless you have a huge network determinism is not necessary

thanks for your answers

The latest generation ethernet field buses, such as Profinet, Ethernet/IP and Powerlink, uses TCP/IP in combination with UDP, and special requirements for the network components involved.

One ethernet field bus that does not use and cannot coexist with TCP/IP or UDP is Ethercat.

JesperMP said:

The latest generation ethernet field buses, such as Profinet, Ethernet/IP and Powerlink, uses TCP/IP in combination with UDP, and special requirements for the network components involved.

One ethernet field bus that does not use and cannot coexist with TCP/IP or UDP is Ethercat.

Click to expand...

Ethernet/IP name already suggest it uses different protocol than tcp. I dont have any experience with that so that is just based on the name. Im pretty sure that profinet atleast does not use tcp for all communications, ip it does.

I am currently commisioning a job with, at present, 7 PLCs - the peer to peer network is Ethernet IP. It is really very good. There are another 11 PLCs to be added to the network at a later date.
The PLCs are Omron - I am doing the software for another company in this case. Setting up Ethernet IP communications has been really simple - go online, see all the PLCs, set 30 words to each in the Ethernet IP wizard and jusat download it to the PLCs on the network. I have never found an easier sdetup for a network in my life yet.
It then just works, very fast too.
I have not used it for remote I/O at this point.
Ethercat is on the way for peer to peer as well. At present it is used mainly for motion control due to it's speed. Apparently for peer to peer with PLCs it can be used in a ring topology allowing for redundancy in a wire network - break the ring and all the PLCs can still get to each other from the other direction, This will also allow an Ethernet type wire network to detect where the break occurs. Previously I think this has only been available with fibre.

TCP/IP is good for messaging but....

TCP is very poor at handling I/O. The error correction actually gets in the way because it will retry to send old missed packets rather than retry with new data.

I don't recommend Modbus TCP for I/O. It is too bad there isn't a Modbus UDP.

Messaging should be used for things like changing parameters where the correct data must received. I/O is good for things that change frequently.

Siemens actually sends raw Ethernet packets in ProfiNet. This makes the I/O very fast. The rest of the ProfiNet is big and bloated.

Automation Direct can send raw Ethernet packets too. Back around 2000 AD was just as fast as the PLC5 Ethernet at a fraction of the cost because of the low overhead.

I am impressed with EtherCat. I think it is the best of the bunch for a number of reasons. The biggest is that the slave I/O modules can be implemented very cheaply and this is not possible with Ethernet/IP and NO WAY using ProfiNet.

I have to correct myself.

JesperMP said:

One ethernet field bus that does not use and cannot coexist with TCP/IP or UDP is Ethercat.

Click to expand...

Ethercat can actually coexist with "regular" TCP/IP and UDP devices.
Normally Ethercat uses a time-slice method that takes place within a regular "ethernet frame" to achieve the high throughput.

And, if network segments behind routers has to be reached, Ethercat packs the normal data into a UDP/IP "datagram".