September 2011
5
V1.44
Copyright © 2011 Adept Systems, Inc. and Control Network Solutions Ltd All Rights Reserved.
1. Overview
1.1. Introduction
The eNodeIV, Grouter4 (GR4) router supports two open standard protocols, namely ANSI/EIA
709.1 and ANSI/EIA 852. Both the ANSI/EIA 709.1 and ANSI/EIA 852 are defined by the
Consumer Electronics Association Technology & Standards R7.1 HCS1 Subcommittee. For more
details seethe standards as 709.1 and 852. The 709.1 is also known by its trademarked name, LonTalk®. A
709.1 network is also commonly referred to as a Local Operating Network or LON. This
document will use 709.1 network and LON interchangeably.
The 852 protocol acts as the transport service to convey 709.1 messages over
Internet Protocol
(IP) networks. This technique of using another protocol (i.e. 852) to transport a message over
an alternate media is often referred to as
tunnelling
. In 852 parlance the tunnelled protocol is a
Component Network
(CN) protocol. The 852 protocol is a generic tunnelling protocol and is not
limited to 709.1. However, a particular implementation of the 852 protocol may only support
the tunnelling of a single CN protocol. The tunnelled CN messages have no information or
awareness of the tunnelling process. Although some of the figures in this document use CN or
CN/IP to represent a component network or component network to internet protocol
connection, the only CN currently supported by the eNodeIV device is 709.1
A component network protocol is often called a field bus due to its use for machine to machine
networking and control in the
field
. This document, however, will only use the term component
network or CN.
852 not only provides the vehicle to transport ANSI 709.1 messages across IP, but it also
provides management of these connections or routes. A logical grouping of 852 devices that
exchange packets is called an 852 channel. One may think of an 852 channel as a kind of
virtual
LAN
on an IP network.
An eNodeIV device forwards 709.1 packets to or from an IP channel (using an Ethernet or WiFi
transceiver) and a CN channel (using twisted pair FT-10 or RS-485 transceivers). The eNodeIV
device has a presence on, or physical connection to, both channels. The router takes 709.1
messages from the component network, wraps them in an 852 packet and sends them over the
IP network. The eNodeIV device also receives 852 packets on its IP interface, un-wraps them
and puts the 709.1 messages on the CN channel. The virtual 852 channel looks like a CN channel
to CN nodes. The IP element is transparent. This enables a flat network and is more easily
managed and scaled than using CN to IP interfaces that do not hide the IP element from the CN
nodes. The important thing is not what the CN to IP device is called but how transparent it
makes the IP network appear to the CN nodes.
Network connection devices can operate at different layers of particular networks protocol
stack. 709.1 is an OSI 7 Layer type protocol. Whereas, the Internet Protocol has only 4 layers.
(See Figure 1.1 for a diagram of the different layers of the two protocols.)
