FAQ Logical Topology

8/3/2019 FAQ Logical Topology

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Topology

1 Introduction

A topology is a (pictorial) description of thestructure and hierarchy of a network, including

the devices and communication paths.The Logical Topologydescribes the configura-tion of an installation from the point of view ofthe communication flow. The PhysicalTopology gives a, mostly simplified,description of the physical layout of thecommunication media and the physicallocation of the KNX Devices.

2 Logical Topology, mediumindependent

The logical topology of a KNX installation is

structured in a Backbone Line, Main Lines and

Lines. This structure is reflected in the Indivi-dual Address of KNX devices.

There is only one single Backbone Line.

Main Lines are hierarchically subordinate tothe Backbone Line. Up to 15 Main Lines maybe defined in an installation. Main Lines maybe numbered from 1 to 15. The Backbone Linehas Main Line number 0. No Main Line mayhave Main Line number 0.

Main Lines may be connected to BackboneLines by means of an optional BackboneCoupler. There may at maximum be oneBackbone Coupler in a Main Line. The Back-bone Coupler belongs to the Main Line, not tothe Backbone Line. A Backbone Coupleralways has Device number 0 and Line number

0.

BbC

ML1

BbC

ML2

BbC

ML3

BbC

ML1

Backbone Line LegendBbC Backbone CouplerML Main Line

Figure 1 - Backbone Line & Main Lines

Lines are hierarchically subordinate to theMain Lines. Up to 15 Lines may be defined perMain Line in an installation. Lines may benumbered from 1 to 15. A Main Line mustalways have Line Number 0. No Line mayhave Line Number 0. Line Numbers are writtenpreceded by the number of the Main Line theLine is connected to.

Examples:

4.9 may be the notation for the Line 9connected to Main Line 4.

Lines may be connected to Main Lines bymeans of a Line Coupler. There may atmaximum be one Line Coupler in a Line. TheLine Coupler belongs to the Line, not to theMain Line. The Line Coupler always has theDevice number 0. No other device may havethe device number 0.

LC

LM.1

LC

LM.2

LC

LM.3

LC

LM.1

Main Line M LegendLC Line Coupler

L Line

Figure 2 - Main Line & Lines

An Area consists of the whole of a Main Linewith subordinate Lines and all connecteddevices. A KNX installation may thereforecount up to 15 Areas. The Area number is the

number of the Main Line it contains. The

Backbone Line with the devices attached to itis not seen as an Area.

A Subnetwork is any part of this topology with

the same Main Line number and the same

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2005.02.25 FAQ001 Logical Topology v050225a.doc

Copyright 1999 - 2005, Konnex Association


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Topology

Line number. The Backbone Line, any MainLine and any Line are Subnetworks.

The KNX End Devices may be connectedanywhere in this topology. Up to 255 KNX End

Devices can be addressed in any Subnetwork.KNX End Devices may be numbered from 1 to255. No KNX End Device may have Devicenumber 0.

Legend

BbC Backbone Coupler

LC Line Coupler

End Device BbC

ML1

BbC

ML2

BbC

ML3

BbC

ML15

LC

L1

LC

L2

LC

L3

LC

L15

LC

L1

LC

L2

LC

L3

LC

L15

Legend

Backbone Line

ML Main Line

L Line

Figure 3 - Backbone Line, Main Lines and Lines

2.1 Hierarchical Structure

The Logical Topology defines a hierarchicalorganisation of the KNX Network: messagesmay only pass from one Subnetwork toanother following a path in the LogicalTopology.

2.2 Individual Address

Every KNX Device (Backbone Coupler, LineCoupler, KNX End Device, ...) must have anIndividual Address. This Individual Address isunique throughout the complete topology. TheIndividual Address of any device is composedas follows:

Bit 15 Bit 0

M M M M L L L L D D D D D D D D

Main Linenumber

Linenumber

Device number

This Individual Address is written as M.L.D

Reserved Individual Addresses:

Device number 0 is reserved for BackboneCouplers and Line Couplers.

NOTE AS A BACKBONE COUPLER IS INSTALLED IN AMAIN LINE, ALSO ITS LINE NUMBER IS 0.

BbC

ML1

BbC

ML2

BbC

ML3

BbC

ML15

LC

L1.1

LC

L1.2

LC

L1.3

LC

L1.15

LC

L15.1

LC

L15.2

LC

L15.3

LC

L15.15

15.15.255

15.15.1

15.15.2

15.15.015.3.0

15.3.255

15.3.1

15.3.2

15.2.255

15.2.1

15.2.2

15.2.0

15.1.255

15.1.1

15.1.2

15.1.0

1.15.255

1.15.1

1.15.2

1.3.255

1.3.1

1.3.2

1.2.255

1.2.1

1.2.2

1.1.255

1.1.1

1.1.2

1.0.255

1.0.1

1.0.2

2.0.255

2.0.1

2.0.2

3.0.255

3.0.1

3.0.2

15.0.255

15.0.1

15.0.2

0.

0.

1

0.

0.

2

0.

0.

255

1.15.01.3.01.2.01.1.0

1.0.0 2.0.0 3.0.0 15.0.0

Legend


LC Line Coupler

End Device

Legend

Backbone Line

ML Main Line

L Line

Figure 4: Logical Topology reflected in the Individual Addresses





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Topology

Examples:

4.9.12 may be the Individual Address for any KNX End Device.

4.9.0 is the Individual Address of the Line Coupler that couples Line 4.9 to Main Line 4.

LC

7.0.0 is the Individual Address of the Backbone Coupler coupling Main Line 7 to the

Backbone Line.

3 Media in the Logical Topology

The Subnetwork is the smallest part of theLogical Topology that shall be implementedwith one single Physical Layer type. It is notallowed to split up a Subnetwork into differentPhysical Layer types.

A Domain is is that part of the LogicalTopology over which the data signals of onePhysical Layer type propagate, possibly with

resending with identical characteristics butwithout changing the message contents andwith respect of the Logical Topology.

The smallest possible Domain therefore is aSubnetwork. A larger Domain may encloseone or more united Subnetworks.

Closed Media are these Physical Layer Typeson which the message signals propagatealong the medium in a controllable way.

EXAMPLE TWISTED PAIR

Open Media are these Physical Layer Types

on which the message signals do not follow awirelike physical medium

EXAMPLE POWERLINE, RADIO FREQUENCY

In open media, it may be impossible to phy-sically separate:

a) Subnetworks

In this case, the Backbone Couplers andLine Couplers are optional. Lines maythen be connected to Main Lines withouta Line Coupler and Main Lines may beconnected to the Backbone Line without aBackbone Coupler.

b) Domains

If in 2 Domains identical transmissioncharacteristics are used, messages passundetected from one Domain to another.

To allow separating Subnetworks andDomains and thus respect the LogicalTopology, the Link Layers of open media limittheir communication by using a DomainAddress. This Domain Address separatesbetween Domains in one KNX Network andbetween different KNX Networks. The DomainAddress is an unstructured 16-bit number.

Every Domain has an own unique DomainAddress within an installation.

Domain Address 0000h is reserved for cross-media broadcast communication.

L1

LC

L2

LC

L3

LC

L15

LC

L1

LC

L2

LC

L3

LC

L15

Domain Address0x1F2A

Domain Address0x2431

BbC

ML1

BbC

ML2

BbC

ML3

BbC

ML15

Domain Address0x242C

Domain Address

0x1011

Legend


LC Line Coupler

End Device

Legend

Backbone Line

ML Main Line

L Line

Figure 5 - Examples of Domains and Domain Addresses





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Topology

3.1 Message Routing

To allow in principle for connection orientedcommunication between any two devices in a

KNX installation, possibly connected to dif-ferent media with none or more, possiblydifferent media in-between, the IndividualAddress must be unique throughout all usedmedia.

If neighbouring Subnetworks are connected toeach other via a Line- or Backbone-Coupler- this is mandatory a Media Coupler in case ofcoupling different media - this coupler shallfilter the messages in both directions.Thisrouting is a functionality of the Network Layerin the Coupler.

The filtering is based on the destination ad-dress field and for open media additionally onthe Domain Address-field in the message.

The following cases are possible:

1. Destination Address = Group Address

The routing is in this case based on a routingtable containing information which groupaddressed messages shall be passed.

2. Destination Address = Individual Address

The routing is in this case based on acomparison between the coupler's own

Individual Address and the destinationaddress.

3. Destination Address = Broadcast

Closed media: messages are alwayspassed in both directions

Open media: messages are passed ornot based on the Domain Address

a) Domain Address 0x0000

The Media Coupler does not passthe message to the other medium.

b) Domain Address = 0x0000The Media Coupler passes themessage to the other medium.

4 Notes

Lines may also be connected directly to the

Backbone Line. This is however notrecommended.

4.1 Twisted Pair

For KNX Twisted Pair media, ElectricalSegments are defined. An ElectricalSegment is a part of a Subnetwork that iselectrically uninterrupted. If in an ElectricalSegment the Twisted Pair is short-circuited,no communication is possible in thatElectrical Segment.

NOTE FOR POWERLINE, IF WE TAKE THE SAMEDEFINITION OF ELECTRICAL SEGMENT AS PART OF THEPHYSICAL MEDIUM THAT IS ELECTRICALLYUNINTERRUPTED, AN ELECTRICAL SEGMENT MAY ASWELL ENCOMPASS MORE THAN ONE LINE.

The Electrical Segment is part of thePhysical Topology of the KNX Network, notof the Logical Topology. In KNX TP1, up to4 Electrical Segments may be connectedusing 3 Repeaters.

NOTE REPEATERS CAN EXTEND THE RANGE OF ASUBNETWORK IN KNX TP1-64. IN KNX TP1-256 THEYARE NOT NECESSARY.

A Subnetwork may exist of at least one, toup to four electrical segments. Everyelectrical segment may be powered by oneor two Power Supply Units.

Disclaimer

This document is provided by the Konnex Association as is. It has no normative value and shall not be used forany product development. This document has not been subject to the approval process within KonnexAssociation. No guarantee is given that this document is complete and up-to-date.




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