LonTalk Protocol Specification - EnerLon

1 LonTalk ProtocolSpecificationVersion @E C H E L O N C O R P O R A T I O N078-0125-01 AEchelon, LON, LONWORKS, Neuron, 3150, LonBuilder, LonTalk , andLonManager are registered trademarks of Echelon , LonMaker, LonSupport, LonUsers, LONews, LONMARKand 3120 are trademarks of Echelon Corporation. Other namesmay be trademarks of their respective brand and product names are trademarks or registeredtrademarks of their respective MAKES AND YOU RECEIVE NO WARRANTIES ORCONDITIONS, EXPRESS, IMPLIED, STATUTORY OR IN ANYCOMMUNICATION WITH YOU, AND ECHELON SPECIFICALLYDISCLAIMS ANY IMPLIED WARRANTY OF MERCHANTABILITYOR FITNESS FOR A PARTICULAR LICENSE IS GRANTED UNDER ANY COPYRIGHT OR PATENT OFECHELON CORPORATION EXCEPT PURSUANT TO A WRITTENLICENSE AGREEMENT WITH ECHELON part of this publication may be reproduced, stored in aretrieval system, or transmitted, in any form or by any means,electronic, mechanical, photocopying, recording, orotherwise, without the prior written permission of No.

2 19550 Printed in the United States of 1994 by Echelon Corporation4015 Miranda AvenuePalo Alto, CA 94304, USAT able of ContentsLonTalk Protocol Specification (Created 1989-1994) Echelon 3 of And AND Protocol . of LonTalk Protocol AND Types and and to the Link to the Physical Detection p-persistent CSMA Overview Channel . Collision Predictive CSMA Transmit Receive Manchester Structuring of the Network . 8 Routing Algorithm CONTROL of ContentsLonTalk Protocol Specification (Created 1989-1994) Echelon 4 of Control Types and Protocol State Send Receive Pool Size and Configuration of of Structure of the Session Types and Timing Protocol Client Protocol Server Protocol and the Role of the Checksum Number Types and Protocol State Between the Offline State and Request - Notification to the Application Notification for Notification for Network MANAGEMENT AND Management and Diagnostics Application 80 Table of ContentsLonTalk Protocol Specification (Created 1989-1994)

3 Echelon 5 of the Network Management Configuration An Application Handling Router Network Management Formats and Respond to Network Variable Group Network Variable Node Standard Network Variable Variable Value Pin Management Escape Clear Group or Subnet Group or Subnet Table Group Subnet Do Not Forward Do Not Forward Types and Transceiver Capacity and Conditions Conditions High A PDU of ContentsLonTalk Protocol Specification (Created 1989-1994) Echelon 6 of 112 This page is intentionally left blankIntroductionLonTalk Protocol Specification (Created 1989-1994) Echelon 7 of 112 1. INTRODUCTION Scope And ObjectivesThe LonTalk Protocol is designed for communication in control networks. Thesenetworks are characterized by short messages (few bytes), very low per node cost,multiple communications media, low bandwidth, low maintenance, multivendorequipment, and low support document provides the Protocol specifications for the LonTalk Protocol (the physical layer Protocol is not limited to any particular communicationsmedium, and thus is defined by any number of transceiver designs that can beconnected to the Neuron Chip).

4 See the Neuron Chip Data Book published byMotorola and Toshiba for details on the interface requirements of thecommunication port. See the LONMARK Layers 1-6 Interoperability Guidelinesfor specifications on standard transceivers. See the LONMARK Application LayerInteroperability Guidelines for specifications on how to design interoperableapplication nodes with the LonTalk Document OverviewFollowing the overview in section 2 and the description of addressing in section 3,the document is structured in a uniform fashion. A chapter is dedicated to eachprotocol layer or sublayer. Each chapter starts with a list of assumptions about theservice provided by the underlying layers. For the sake of completeness, a briefservice description is then included, followed by a detailed Specification of theprotocol.

5 Most of the algorithms are specified in structured English, using a Pascal-like 11 contains a description of the built-in network management capabilitiesof the Protocol . Chapter 12 describes the essential behavioral characteristics of theprotocol. Finally, the syntax of all Protocol Data Units is summarized in and OverviewLonTalk Protocol Specification (Created 1989-1994) Echelon 8 of 112 2. TERMINOLOGY AND P ROTOCOL OVERVIEW TerminologyThe primary objective of this document is to provide a concise yet readable speci-fication of the LonTalk Protocol . For this reason, the notation and terminology isnot as formal as that used in some other Protocol ChannelS&FRepeaterxyBridgeRouterSubnet B, B', ..Subnet A, A', ..Domain ADomain BGatewayconnects two channels (x and y); forwards allpackets from x to y and vice versa, as long asthe packets originated on one of the samedomain(s) as the bridgeBridgeRouterroutes packets to their respective destinations byselectively forwarding from subnet to subnet; aLonTalk router always connects two (sets of)subnets; LonTalk routers may modify the layer 3address fields to prevent packets from looping.

6 (Application) Gatewayinterconnects networks at their highest protocollayers (often two different protocols); twoLonTalk domains can be connected through anapplication & Forward Repeatermay repeat on the same channel or mayconnect two channels; generates duplicates;multiple repeaters may cause packet set of nodes accessible through the same layer2 Protocol ; a routing abstraction for a channel; LonTalk Protocol subnets are limited to 127 nodesTable Basic TerminologyTerminology and OverviewLonTalk Protocol Specification (Created 1989-1994) Echelon 9 of 112 Table introduces the basic terminology employed throughout the of it is commonly used and the terms have the same meaning in both thegeneral and the LonTalk context. However, there are subtle differences. Forexample, bridges in general do selective forwarding based on the layer 2 destinationaddress.

7 There are no layer 2 addresses in the LonTalk Protocol , so LonTalk bridgesforward all packets, as long as the Domain address in the packet matches a Domainof which the bridge is a member. Routers, in general, perform network addressmodification so that two protocols with the same transport layer but differentnetwork layers can be connected to form a single logical network. LonTalk routersperform network address modification on packets that might otherwise loop, buttypically they only examine the network address fields and selectively forwardpackets based on the layer 3 address LonTalk Protocol layering is described using the standard OSI terminology, asshown in figure N protocolentitylayer N protocolentityFigure Protocol TerminologyThe Protocol Data Unit (PDU) abbreviations used throughout this document are.

8 MPDUMAC Protocol Data Unit, or frameLPDULink Protocol Data Unit, or frameNPDU Network Protocol Data Unit, or packetTPDUT ransport Protocol Data Unit, or a message/ackSPDUS ession Protocol Data Unit, or request/responseNMPDUN etwork Management Protocol Data UnitDPDUD iagnostic Protocol Data UnitAPDUA pplication Protocol Data Overview of LonTalk Protocol LayeringLonTalk Protocol layering consists of the layers shown in table At each layerwithin the table there is a description of the services provided within that layer is described and OverviewLonTalk Protocol Specification (Created 1989-1994) Echelon 10 of 112 Multiple Physical Layer protocols and data encoding methods are used in LonTalksystems. Each encoding scheme is media dependent. For example, differentialManchester encoding is used on twisted pair, both FSK modulation and a modifieddirect sequence spread spectrum system is used on the power line, FSK modulationis used on RF, order to deal with a variety of media in the potential absence of collision detec-tion, the MAC (Medium Access Control) sublayer employs a collision avoidancealgorithm called Predictive p-persistent CSMA (Carrier Sense, Multiple Access).

9 Fora number of reasons, including simplicity and compatibility with the multicastprotocol, the Link layer supports a simple connection-less service. Its functions arelimited to framing, frame encoding, and error detection, with no error recovery Layerframing, data encoding, CRC error checkingMAC Sublayerpredictive p-persistent CSMA: collision avoidance; optional priority and collision detectionNetwork Layerconnection-less, domain-wide broadcast, no segmentation,loop-free topology, learning routersPhysical Layermultiple-media, medium-specific protocols ( , spread-spectrum)Transaction Control Sublayercommon ordering and duplicate detectionSession Layerrequest-response serviceApplication & Presentation LayersTransport Layeracknowledged and unacknowledged unicast and multicastAuthenticationserverLAYERS 6, 7:LAYER 5:LAYER 4:LAYER 3:LAYER 2:LAYER 1:Network Management:network management RPC, diagnosticsApplication.

10 Network variable exchange,application-specific RPC, LonTalk Protocol LayeringTerminology and OverviewLonTalk Protocol Specification (Created 1989-1994) Echelon 11 of 112 The Network layer handles packet delivery within a single domain, with no provi-sions for inter-domain communication. The Network service is connection-less,unacknowledged, and supports neither segmentation nor re-assembly of routing algorithms employed by the network layer to learn the topologyassumes a tree-like network topology; routers with configured tables may operateon topologies with physical loops, as long as the communication paths are logicallytree-like. In this configuration, a packet may never appear more than once at therouter on the side on which the packet originated. The unicast routing algorithmuses learning for minimal overhead and no additional routing traffic.