communication protocol

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Thread Starter

Shoaib Nizami

Allen Bradley is using the Ethernet/IP where almost all other DCS vendors are using TCP/IP, where both offers the same advantages. so why Allen Bradley is sticking to the different standard, so how it is better than the other one. Anyone has clue?
 
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Allen-Bradley is using the same Internet Protocol (IP) standards as everyone else, and TCP/IP is only a means of transferring raw data, similar to the way a telephone allows a conversation with someone in a different location.

All of the DCS manufacuturers must add a higher level "application layer" protocol on top of IP for any meaninful exchange of data. In the telephone analogy above, the language being spoken is the application layer protocol.

Ethernet/IP is an application layer protocol, and is carried over both UDP/IP and TCP/IP transport layers -- UDP for time sensitive "implicit" messages such as I/O updates, and TCP for "explicit" messages and uploading/downloading of parameters, setpoints, programs.

Paul...
 
AB's name "Ethernet/IP" means "Ethernet Industrial Protocol". It's just their brand name for their application protocol. The name is intended to confuse people, and it looks like they've succeeded.

There are three main Ethernet industrial protocols. AB uses Ethernet/IP (EIP), Siemens uses Profinet, and most others use Modbus/TCP. All three are more or less equivalent for most normal applications, although some offer features for special applications that others don't. There are some other minor protocols as well (Ethercat, Powerlink/Ethernet, etc.), but they aren't as common.

All use TCP/IP and/or UDP/IP. Some also use their own proprietary transport protocols for special applications. AB EIP is probably more properly thought of as a collection of different protocols sold under a common brand name, rather than as an actual single protocol (Profinet is the same). You won't get a straight answer from AB as to how this collection of protocols actually works because that information only gets licensed out to selected partners in a very controlled manner (the same is true for Profinet).

Modbus/TCP is a single protocol that runs on top of TCP/IP. There is also a UDP version of the protocol that some people use, but that isn't covered by the Modbus standard (the difference is very minor though). The Modbus/TCP specs are open and can be downloaded from modbus.org.

As for why everyone doesn't just use a common open protocol, well once they've got you as a customer, you didn't think they were going to make it easy for you to use stuff from their competitors now, did you?
 
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