Experion C300 Direct EtherNet/IP Interface Infi90 Documentation... · motion, and the configuration and management of intelligent field devices. CIP is the protocol language used

Version 1.0 Honeywell Proprietary Jan 2017

Experion C300 Direct EtherNet/IP Interface Specification

Technical Information

EP03-560-500 Release 500

Jan 2017, Version 1.0

Experion C300 Direct EtherNet/IP Interface Specification, EP03-560-500 2

Revision History

Revision Date Description

1.0 Jan, 2017 First document release



Table of Contents

1. Product Introduction ...................................................................................................................................................... 4

1.1. Solution Introduction ................................................................................................................................................. 4

1.2. CIP and Ethernet/IP™ .............................................................................................................................................. 4

1.2.1. CIP - The Actual Protocol ......................................................................................................................................................... 4

1.2.2. EtherNet/IP ............................................................................................................................................................................... 4

1.2.3. ODVA ....................................................................................................................................................................................... 5

1.3. Two Ethernet/IP Solutions ........................................................................................................................................ 6

2. C300 (Direct) Ethernet/IP Solution Overview ................................................................................................................ 7

2.1. Solution Overview ..................................................................................................................................................... 7

2.2. Required Hardware ................................................................................................................................................... 7

2.3. EtherNet/IP Device/Node Types ............................................................................................................................... 8

2.4. [ UDT ] User-defined Data Types - Overview ............................................................................................................ 9

2.5. [ I/O ] Device Blocks - Overview .............................................................................................................................. 10

2.6. Supported [ I/O ] Device Blocks and Devices.......................................................................................................... 12

2.6.1. Summary - I/O Devices Currently Supported ......................................................................................................................... 12

2.6.2. Additional Details on Validated I/O Devices ........................................................................................................................... 13

2.6.3. Adding New I/O Device Types ............................................................................................................................................... 14

3. Important Communication Concepts .......................................................................................................................... 15

3.1. IP Addresses & CIP Connections ........................................................................................................................... 15

3.1.1. Ethernet IP Address ............................................................................................................................................................... 15

3.1.2. CIP Connections..................................................................................................................................................................... 15

3.2. IP Address and CIP Connection Usage .................................................................................................................. 16

4. Ethernet/IP Capacity, Rules, and Specifications ........................................................................................................ 17

4.1. Ethernet/IP Performance and Capacity Limits ........................................................................................................ 17

4.1.1. Connections Summary ........................................................................................................................................................... 18

4.1.2. UDT Data Types Supported by the C300: .............................................................................................................................. 18

5. Model Numbers and Solution Licensing ..................................................................................................................... 19

5.1.1. C300 License.......................................................................................................................................................................... 19

5.1.2. C300 models .......................................................................................................................................................................... 19

5.1.3. Tofino Firewall ........................................................................................................................................................................ 19

5.1.4. Rockwell Stratix 8000 Switch ................................................................................................................................................. 19

5.1.5. Rockwell ETAP ....................................................................................................................................................................... 19



1. Product Introduction

1.1. Solution Introduction

First released with Experion R430, the C300 Direct EtherNet/IP solution provides a cost effective interface to EtherNet/IP

networks and access to data resident in EtherNet/IP compliant devices.

EtherNet/IP allows the user to satisfy a broad spectrum of process control needs using one protocol. Users can choose from

a comprehensive set of different devices types from a large list of vendors.

1.2. CIP and Ethernet/IP™

1.2.1. CIP - The Actual Protocol

The Common Industrial Protocol (CIP™) is a fully networked solution that encompasses a comprehensive suite of messages

and services to fully support a broad spectrum of process needs and applications on one protocol. CIP is a peer to peer

object oriented protocol that provides connections between industrial devices (sensors, actuators, drives, motors, I/O, etc.)

and higher-level devices (controllers). CIP is applicable to factory and process automation control, safety, synchronization,

motion, and the configuration and management of intelligent field devices.

CIP is the protocol language used to enable communication between all nodes on the network. It is physical media and data

link layer independent. This media independence provides the ability to choose the CIP Network best suited for your

application.

CIP is implemented on various networks as follows…

CompoNet™ ………. CIP on TDMA technology

DeviceNet™ ………. CIP on CAN technology

ControlNet™ ……… CIP on CTDMA technology

EtherNet/IP™….... CIP on ETHERNET technology

1.2.2. EtherNet/IP

Ethernet/IP™ is the name given to the Common Industrial Protocol (CIPTM), as implemented over standard Ethernet (IEEE

802.3 and the TCP/IP UDP protocol suite). Ethernet/IP is a high-level industrial application layer protocol for industrial

automation applications that uses the tools and technologies of traditional Ethernet. Ethernet/IP uses all the transport and

control protocols used in traditional Ethernet including the Transport Control Protocol (TCP), the Internet Protocol (IP) and

the media access and signaling technologies found in off-the-shelf Ethernet interfaces and devices.

EtherNet/IP was introduced in 2001 and today is one of the most developed, proven and complete industrial Ethernet

network solutions available for industrial control and automation solutions. It enables real-time control and data acquisition

for discrete applications, continuous process, safety, drive, motion, and applications requiring high availability. Ethernet/IP is

applicable to factory automation, process automation, and is well suited for both batch and continuous operations.



1.2.3. ODVA

Founded in 1995, ODVA is a global association whose members comprise the world’s leading automation companies.

ODVA’s mission is to advance open, interoperable information and communication technologies in industrial automation.

EtherNet/IPTM and CIPTM are managed by ODVA. ODVA publishes The EtherNet/IP Specification and helps ensure

compliance through conformance testing.

More information is available at the ODVA website….

WWW.ODVA.org



1.3. Two Ethernet/IP Solutions

As of R500 there will be two different C300 EtherNet/IP solutions available, as follows:

1. C300 (Direct) EtherNet/IP solution….. First released with Experion R430…..

a. C300 communicates over FTE level-2 to connect directly to Ethernet/IP networks and devices.

b. This solution can be hosted on C300 models CC-PCNT01 and CC-PCNT02.

c. A Tofino firewall is required between the FTE and EtherNet/IP networks.

d. The C300 (Direct) solution is the subject of this specification document.

2. C300 (EIM) EtherNet/IP solution…. First released with Experion R500…..

a. Solution uses a new Series C EIM (Ethernet Interface Module).

b. C300 communicates through the EIM to access EtherNet/IP Networks and devices.

c. This solution can only be hosted on C300 model CC-PCNT02.

d. EIM solution provides improved specifications and enhanced functionality.

e. The C300 (EIM) solution is covered in specification document EP03-561-500.

Notes:

1. Both solutions are supported with R500 and can coexist on the same Experion Server Cluster and FTE Community.

2. A given C300 can host one or the other solution, but not both. See spec doc EP03-561-500 for more details on the EIM EtherNet/IP solution.



2. C300 (Direct) Ethernet/IP Solution Overview

This section and the remainder of this document will focus on information related to the C300 Direct EtherNet/IP solution.

The EIM EtherNet/IP solution is covered in a separate specification document.

2.1. Solution Overview

Refer to Figure 1. Starting in Experion R430, EtherNet/IP is implemented as a licensed option for the C300 controller. A

single license is required (per C300 or redundant pair) to enable the C300 EtherNet/IP functions and features covered in this

document. C300 Direct Ethernet/IP license model number …. TC-EPLX01

An Ethernet/IP enabled C300 can communicate (over FTE Level-2) with Ethernet/IP compliant devices resident on

Ethernet/IP networks. As shown, the EtherNet/IP network is interfaced to Experion through a Tofino firewall and Stratix 8000

switch. The C300 can accessed data (as data reads and writes) from the connected Ethernet/IP compliant devices. This data

can then be used for control, indication, and historization.

EtherNet/IP topologies supported are Star, Linear Bus, and DLR (Device Level Ring). More details on these topologies can

be found in the Honeywell R500 EtherNet/IP User Guide.

2.2. Required Hardware

The following hardware has been qualified and is mandatory for the solution………

Cisco 2960 or higher

Tofino (Xenon) firewall

Rockwell Stratix 8000 switch

Rockwell 1783-ETAP (used with Device Level Ring topologies)

Figure 1 C300 Direct EtherNet/IP Solution Topology



2.3. EtherNet/IP Device/Node Types

As shown in Figure 4, the Ethernet/IP network hosts Ethernet/IP compliant nodes that connect to the process and perform

process related tasks, control, and provide process level information.

The EtherNet/P solution allows the C300 to read and write data resident in these process connected nodes. This data can

then be used for control, historization, and the operator HMI.

In terms of data access, the C300 Direct solution divides Ethernet/IP devices into two major categories, as follows:

1. ControlLogix Processors:

– The C300 communicates with the Rockwell ControlLogix processor on a supervisory level.

– The ControlLogix process will have its own dedicated I/O.

– The solution uses UDTs (User-defined Data Types) to communicate (read and write) data between the C300 and the ControlLogix processor.

– Data is transferred using EtherNet/IP (CIP) Explicit Class-3 messaging.

2. Process Connected I/O Devices:

– These device types connect directly to the process and perform some set of process control tasks. Motor starters, drive controllers, and I/O are a few examples.

– C300 directly connects with the device to access process and device data that is used for primary control and logic.

– The solution provides device-specific I/O blocks for each particular vendor device type supported.

– Data is transferred using EtherNet/IP (CIP) Implicit Class-1 messaging.



2.4. [ UDT ] User-defined Data Types - Overview

Refer to Figure 2. UDTs provide an effective and efficient way to read and write data resident in ControlLogix PLCs. UDTs are used for all data transfer between the C300 and ControlLogix processors.

Some Important UDT Characteristics:

The C300 utilizes Class-3 “Explicit” CIP messaging to read and write data resident in ControlLogix processors.

UDT data transfer is intended to support a Supervisory control arrangement between the C300 and ControlLogix processor. In this arrangement, the C300 is the supervisor and the ControlLogix processor is the primary controller.

Along with the typical process data, diagnostic data can also be included in UDTs.

Data transfer rate is determined by the user entered UDT RPI (Requested Packet Interval) setting in milli-seconds.

The UDT is a user defined structure that contains a set of user specified parameters and user defined data types.

Concept: As shown in Figure 2, UDTs are fully defined by the user. Users will create a UDT in the appropriate ControlLogix engineering tool and then create a matching UDT in the Honeywell Control Builder.

For each UDT, the user will determine the following:

UDT Tag name

Number of parameters and parameter names

Parameter data types

Parameter read/write access

UDTs must match exactly on the C300 and ControLogix side

Important! The user should always refer to the ControlLogix documentation to ensure that there are no conflicts between the

C300 and ControlLogix capacity, performance, and specifications that might further limit the UDT solution.

Figure 2 UDT Concept Diagram



2.5. [ I/O ] Device Blocks - Overview

Refer to Figure 3. I/O device blocks are used to access data from process connected devices such as motor starters, drives,

and I/O. This input and output data can then be used by the C300 for primary control and logic strategies.

I/O Device Block Characterizations:

The solution utilizes Class-1 “Implicit” CIP messaging to read and write data resident in process connected I/O such as motor starters, drives, and I/O.

Implicit data transfer is fast and deterministic and well suited to the demands of primary control and logic running in the C300.

Cyclic data transfer rate is determined by the user entered RPI (Requested Packet Interval) setting in milli-seconds.

For each device, the device vendor will create an input and an output assembly. These (vendor determined) assemblies contain parameters that are relevant to the input and output data to be provided by the device. These assemblies are read and written to by the C300 according to the RPI setting.

As supported by each device, device diagnostics may be contained in the assembly.

The parameters contained in these input and output assemblies can be used in Control Modules to create C300 control strategies that use EtherNet/IP resident I/O devices.

In Control Builder, each specific I/O device will have device-specific I/O blocks that are specifically created for that device.

The process of adding new device types requires the creation of new blocks that understand the specific input and output assembly structure for the device to be added.

Note: For complex devices such as motor starters, drive controllers and the like, there is usually one input and one output

assembly per device.

Modular devices like I/O systems usually require an assembly per I/O module. The module type (AI, AO, DI, or DO)

determines if the assembly is of type input or output.

Figure 3 I/O Type Point - Concept Diagram



Figure 4 Two Types of EtherNet/IP Data Transfer



2.6. Supported [ I/O ] Device Blocks and Devices

The device list below represents the devices that have been qualified and are currently supported at the time of the release

of this document. To determine the current list or to request the addition of a new EtherNet/IP compliant device type, contact

your Honeywell representative.

2.6.1. Summary - I/O Devices Currently Supported

EIP Device Use Embedded

(Note-1) Requires Import

(Note-2)

1738 ArmorPoint I/O Typical I/O √

1732E ArmorBlock I/O Typical I/O √

E3 Solid State Overload Relay Motor control 2-states Start/Stop

√

E3 + Solid State Overload Relay Motor control 3-states Stop/State-1/State-2

√

PF 755 Drive Command motor direction and speed

√

PF 753 Drive Command motor direction and speed

√

E300 Smart Relay Motor control 3-states Stop/State-1/State-2

√

Note-1: These device blocks are embedded and loaded with the Experion software. No additional steps are required to use these block types.

Note-2: These device blocks are not loaded with the Experion software. They must be downloaded from the Honeywell website and then manually imported by the user.



2.6.2. Additional Details on Validated I/O Devices

The following provides additional information about the devices validated for the EtherNet/IP solution.

Rockwell Armor Point I/O:

Module Type Channels Signal Type

1738-AENT Adaptor N/A N/A

1738-IB4DM12 DI 4 Sinking 24 Vdc

1738-IB8M12 DI 8 Sinking 24 Vdc

1738-OB2EPM12 DO 2 24 Vdc

1738-OB8EM12 DO 8 24 Vdc

1738-OA2M12AC3 DO 2 120V ac, 220V ac

1738-OE2CM12 AO 2 (4-20 ma)

1738-OE4CM12 AO 4 (4-20 ma)

1738-IE2CM12 AI 2 (4-20 ma)

1738-IE4CM12 AI 4 (4-20 ma)

1738-IT2IM12 AI 2 TC, Milli-volt

1738-IR2M12 AI 2 RTD, resistance

Rockwell Armor Block I/O:

Module Type Channels Signal Type

1732E-IB16M12DR DI 16 with diagnostics

1732E-IF4M12R AI 4 High Level Current/voltage

1732E-OF4M12R AO 4 High Level Current/voltage

1732E-IT4IM12R AI 4 T/C, MV

1732E-IR4IM12R AI 4 RTD, resistance



Rockwell Drives and Overload Relays:

Device Notes/Comments

Rockwell E3 overload relay:

Provides two states (Start/Stop)

E3+ overload relay:

Provides three states, (fwd/stop/rev)

or (hi-spd/stop/low-spd)

Commonly used to control motors.

These devices are actually DeviceNet devices. The use of these

devices requires the Rockwell 193-DNENCATR EtherNet/IP to

DeviceNet Adapter.

Rockwell Power Flex 753 Drive Commonly used for motor control and motor speed

Rockwell Power Flex 755 Drive Commonly used for motor control and motor speed

Rockwell Power E300 Overload relay Commonly used to control motors. Three state possible.

2.6.3. Adding New I/O Device Types

The device list above represents the devices that have been qualified and are currently supported at the time of the release

of this document. To determine the current list or to request the addition of a new EtherNet/IP compliant device type, contact

your Honeywell representative



3. Important Communication Concepts

3.1. IP Addresses & CIP Connections

To completely understand the specifications later in this document, it is important that you understand the concept of an IP

address and the concept of a CIP (Common Industrial Protocol) connection. Each is covered in more detail below.

3.1.1. Ethernet IP Address

As mentioned earlier in this document, Ethernet/IP is CIP (Common Industrial Protocol) over Ethernet. As such, each node

on an Ethernet/IP network is identified by a unique user defined IP address.

The IP address has the following format:

### . ### . ### . ###

Where the first three number sets or octets (### . ### . ###) identify the subnet that the device belongs to and the last three

numbers (###) are referred to as the node index number. The node index is used to identify each unique node on a

particular Ethernet/IP network subnet.

Each node on the Ethernet/IP network subnet must have a unique index number. This is the essential method to identify and

communicate with an Ethernet/IP node.

3.1.2. CIP Connections

The C300 communicates with individual Ethernet/IP nodes using the assigned IP address. The C300 also forms one or more

CIP connections (depending on the device type) to transfer (read and write) data to and from the Ethernet/IP node.

There are two CIP connection types used with the solution, as follows:

Class 1 (Implicit) connections:

Is also often referred to as “I/O” and is utilized for data that is time-critical in nature.

C300 uses these connections for data access for I/O devices such as motor starters, drives, and I/O.

With Implicit Messaging you establish an association (a “CIP connection”) between two devices and produce the Implicit Messages according to a predetermined trigger mechanism, typically at a specified packet rate.

The devices both know and agree on the data formats they will use (i.e., the format is “implied”).

Class 3 (Explicit) connections:

In general has a request/reply (or client/server) nature.

The C300 solution uses these connections specifically for data transfer with the ControLogix processors using UDTs.

Explicit messages include a description of their meaning (expressed explicitly), so the transmission is less

efficient, but very flexible.

In CIP terms, with Explicit Messaging you request a service of a particular object, e.g., a read or a write service.

Compared to Implicit messaging, transmission is less efficient, but very flexible in terms of what can be accessed.



3.2. IP Address and CIP Connection Usage

The table below is provided to help with the concept of IP address and CIP connection usage by node type.

As shown in the table below, in most cases you use one IP address and one CIP connection per Ethernet/IP node. However,

there are cases where you will use one IP address and multiple CIP connections. One example would be standard I/O

subsystem where the headend (gateway module) is assigned the IP address and each individual I/O module would use one

CIP connection.

As shown in the table, all of the Power Flex drives use 1 IP address and only requires 1 CIP connection to transfer all input

and output data related to the device. However, ArmorPoint I/O with the consolidation option set to OFF would consume 1 IP

address and 1 CIP connection for every I/O module on the backplane.

The I/O consolidation option allows you to consolidate (group) several I/O modules into one grouping so all data is returned

using one CIP connection. However, this would also require you to set a common RPI (Requested Packet Interval) for the

entire group of I/O modules.

It is important to identify the IP and CIP connection requirements for a given device type to ensure you stay within the

connection limits provided later in specification section of this document.

For more details on this subject refer to the Ethernet/IP User’s Guide

IP Address and CIP Connection usage table by node type supported by the solution:

EIP Device

CIP

Connection

Type

IP Address Usage Connection Usage

PF 753 and PF 755 Implicit Class-1

1 per Node 1 per Node (includes input & output data)

E3, E3+, and E300 Implicit Class-1

1 per Node 1 per Node (includes input & output data)

ArmorBlock I/O Implicit Class-1

1 per I/O module/block 1 per I/O module/block

ArmorPoint I/O (consolidation option OFF)

Implicit Class-1

1 per I/O chassis/adaptor 1 per I/O module

ArmorPoint I/O (consolidation option ON)

Implicit Class-1

1 per I/O chassis/adaptor 1 per consolidated/module grouping. 1 or more modules can be in a group.

ControlLogix Explicit Class-3

1 per ControlLogix 1 per ControlLogix



4. Ethernet/IP Capacity, Rules, and Specifications

4.1. Ethernet/IP Performance and Capacity Limits

Description Limit Units

Maximum number of FTE Nodes per FTE Community when using the C300 direct Ethernet/IP solution1

200 FTE Nodes

Maximum number of non-FTE Nodes per FTE Community when using the C300 direct Ethernet/IP solution2

200 Non-FTE Nodes

Maximum number of TCP IP and CIP connections per C300 available to access ControlLogix PLCs and Ethernet/IP devices3

TCP IP (address) connections per C300…………………………….

CIP connections available per C300 …………………………………

Note: See section 4.1.1 for more details.

70

70

IP Addresses

CIP Connections

Limits for UDT (User-defined Data Type) Points

Maximum number of ControlLogix processors per C300 that can be connected for UDT point access4

4 ControlLogix Processors/C300

Maximum UDTs per C300 65 UDTs

Maximum number of parameters per UDT 64 Parameters5

UDT - Maximum data size for input/reads 480 Bytes per UDT

UDT - Maximum data size for output/writes 256 Bytes per output

Maximum number of UDT parameter writes pending at any given time

65 Per C300

NOTES:

1. Limit applies as soon as one C300 (in the FTE community) is configured to support this EtherNet/IP solution.

2. This IP address resource is used for all Ethernet/IP nodes/devices, ControlLogix connections, and any other non-FTE node in the community. This will further limit the C300 max of 70 connections.

3. Although any one C300 can support up to 70 TCP IP addresses, the total IP addresses across all C300s in the community is limited by the maximum non-FTE IP address limitation (200).

4. Every C300 can connect to up to 4 ControlLogix processors max. Each connection will consume 1 non-FTE IP address. It will also consume 1 IP address against the C300 maximum of 70.

5. For arrayed parameters, each array element shall count as one against the 64 parameter maximum.



4.1.1. Connections Summary

To transfer input and output data to and from the C300, each EtherNet/IP device will consume both TCP IP (Address) and

CIP connections. The table below summarizes the usage of these resources per device type currently qualified for use with

the solution.

Note that as new devices (not listed in the table) are integrated, this aspect of the solution will need to be determined.

Device Number of TCP IP

connections/addresses per device

Number of CIP connections per device

Notes

E3 and E3+ Relays 1 … per device 1… per device Provides input and output data

E300 Relay 1… per device 1… per device Provides input and output data

PF 753 and 755 Drives 1… per device 1… per device Provides input and output data

ArmorPoint I/O 1… To connect to the I/O

Adaptor module

1… For every I/O module

(Note-1)

Each CIP connection provides the module input or output data

ArmorBlock I/O 1… per device 1… per device

ControlLogix PLC 1… per CLx processor 1… per CLx processor Provide all UDT data from the connected CLx processor.

Note-1: The ArmorPoint I/O provides a feature referred to as “Consolidation”. This feature allows the user to group (or consolidate) a number of like I/O modules so they only consume 1 CIP connection per I/O grouping. This can help to conserve CIP connections against the C300 limit. Refer to the EtherNet/IP User Guide for more details.

4.1.2. UDT Data Types Supported by the C300:

Data Type Read/Write? Description

BOOLEAN R & W 1 –byte… Logical Boolean with values TRUE and FALSE

INT8 R & W 8–bit integer



FLOAT32 R & W 32–bit floating point

STRING Read only STRING value is read from the CLx processor.

Note: String write to CLx is not supported in R430 or R431



5. Model Numbers and Solution Licensing

5.1.1. C300 License

One license per C300 (or redundant pair) is required. Model Number TC-EPLX01

5.1.2. C300 models

The C300 Direct Ethernet/IP solution is supported by C300 models CC-PCNT01 and CC-PCNT02.

5.1.3. Tofino Firewall

A Tofino Xenon SA (Security Appliance) must be used to isolate the FTE network from the Ethernet/IP network.

To order, contact your local Belden Authorized Distributor.

To locate your nearest distributor, contact Belden at:

1-855-400-9071

Or [email protected]

Request Belden part number: TofinoXe-02-00-T1-T1-T-DD-Z9-0001-TA-T-firmware revision

5.1.4. Rockwell Stratix 8000 Switch

The Stratix 8000 switch with IOS firmware is used for connecting the EtherNet/IP-compatible I/O devices and the

ControlLogix PLC to the C300 controllers.

For more information about Stratix 8000, refer to the R500 EtherNet/IP User Guide.

5.1.5. Rockwell ETAP

The 1783-ETAP is qualified for use with DLR (Device Level Ring) Topologies.

For more information

To learn more about Honeywell’s products or

solutions visit our website

www.honeywellprocess.com or contact your

Honeywell account manager.

Automation & Control Solutions

Process Solutions

Honeywell

1250 West Sam Houston Parkway South

Houston, TX 77042

Honeywell House, Arlington Business Park,

Bracknell, Berkshire, England RG12 1EB UK

Shanghai City Centre, 100 Junyi Road

Shanghai, China 20051

www.honeywellprocess.com

Experion® is a registered trademark of Honeywell International Inc.

All other products and brand names shown are trademarks of their respective owners.

This document contains Honeywell proprietary information. It is published for the sole usage of Honeywell Process Solutions’

customers and prospective customers worldwide. Information contained herein is to be used solely for the purpose submitted, and

no part of this document or its contents shall be reproduced, published, or disclosed to a third party without the express

permission of Honeywell International Inc.

While this information is presented in good faith and believed to be accurate, Honeywell disclaims the implied warranties of

merchantability and fitness for a particular purpose and makes no express warranties except as may be stated in its written

agreement with and for its customer.

In no event is Honeywell liable to anyone for any indirect, special or consequential damages. The information and specifications in

this document are subject to change without notice.

EP03-560-500 Jan 2017 © 2014 Honeywell International Inc.

Documents

Experion C300 Direct EtherNet/IP Interface Infi90 Documentation... · motion, and the configuration and management of intelligent field devices. CIP is the protocol language used