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How Ethernet becomes industrial
Prof. Bernard Jouga - Supélec, Rennes – [email protected]
Workshop : Ethernet as a fieldbusGenève – Friday 28th September 2001
Friday 28th September 2001
CERN Workshop Ethernet 2
You said Ethernet…Ethernet offers A level 1 specification : cabling systems,
physical layer… in several versions A level 2 specification : Medium Access
Control… in several versions
So many differences between vintage Ethernetand future Ethernet !
Friday 28th September 2001
CERN Workshop Ethernet 3
… What do you mean ?
Ethernet doesn’t offer A complete stack up to applications, neither for the
office nor for the plant ! One standard solution for determinism and QoS
issues (not yet ?) One standard solution for connecting in industrial
environment (not yet ?) One standard solution for redundancy
management A satisfying solution for accurate stations
synchronization
As many Ethernet solutions as network vendors ?
Friday 28th September 2001
CERN Workshop Ethernet 4
The everlasting confusion
"I need Ethernet if I need a network ableto support TCP/IP applications"
Friday 28th September 2001
CERN Workshop Ethernet 5
AgendaDeterminism and Qos with Ethernet "Vintage" Ethernet Switched Ethernet
Which QoS implementation ?
An overview of vendors proposals Fieldbus interconnection with Ethernet/TCP/IP Fieldbus protocols over Ethernet/TCP/IP IDA proposal
Just one word about securityWhat are the real cost parametersConclusion
Friday 28th September 2001
CERN Workshop Ethernet 6
Vintage Ethernet
Frame broadcasting Along coaxial cables (10 BAS 5, 10 BAS 2) Through multiports hubs (10 BAS T, 100 BAS T)
Collision occurrences Function of the network size, the traffic load,
the average frame size 20% traffic load : 0,1% collisions 40% traffic load : 5% collisions
Non deterministic packet loss and packet delays
Friday 28th September 2001
CERN Workshop Ethernet 7
Switched Ethernet
10 Mbps, 100 Mbps, 1 Gbps 10 Gbps in the labs !
Frame switching on dedicated ports On the fly / Store and forward Half duplex /Full duplex
Friday 28th September 2001
CERN Workshop Ethernet 8
Level 2Back Pressure
Operates in half duplex mode A saturated port sends jam patterns (busy
indicator) to the connected equipment, enforcing the station to Listen Before Talk
No traffic discrimination
STOP
Friday 28th September 2001
CERN Workshop Ethernet 9
Level 2802.3x Flow Control
Operates in full duplex mode A saturated port sends PAUSE packets
to the connected equipment No traffic discrimination
PAUSE
Friday 28th September 2001
CERN Workshop Ethernet 10
Level 2802.1p CoS
Operates in half or full duplex modes IEEE 802.1Q defines the general architecture for Virtual
LANs and the VLAN protocol. IEEE 802.1p defines Classes of Services
Not supported by end-stations adaptersMost switches will not manage the 8 Cos (2 or 4)
Friday 28th September 2001
CERN Workshop Ethernet 11
Level 3DiffServ
Differenciated Services End points managed Uses IPv4 ToS or IPv6 priority field 64 possible levels Needs for adequate switches/routers
and adapted applications
Friday 28th September 2001
CERN Workshop Ethernet 12
TCP/IPIntServ
Integrated Services Routers managed Based on application identification
(IPv4 sockets or IPv6 Data Flow Id) 3 levels of services Uses RSVP Resource reserVation
Protocol to mark a path of reserved ressources for an application flow
Friday 28th September 2001
CERN Workshop Ethernet 13
Conclusion on QoS Management
So many strategies to avoidor minimize packets loss
IEEE 802.1p : a transient solution ? DiffServ bind to IPv6 deployment ? No future for IntServ ? Products are just coming on the
market
Friday 28th September 2001
CERN Workshop Ethernet 14
Switched Ethernet:a case study (1/2)
6 stations, cyclically generating realtime 200 bytes packets, "tagged" high priority
100 Mbps full duplex links One store & forward switch with an average 10 s
nominal latency Coexistence with low priority traffic
Compute the worst case total latency for a RT packet
Ethernet Switch
Station Station Station StationStationStation
Friday 28th September 2001
CERN Workshop Ethernet 15
Switched Ethernet:a case study (2/2)
16 s store & forward 10 s nominal switch latency 122 s flushing (the station can be at
this moment transmitting a low priority max size frame)
80 s queue emptying (5 RT packets already in queue)
TOTAL = 228 s
Friday 28th September 2001
CERN Workshop Ethernet 16
Transmission delays
Yet an another issue ! In complex architectures, end-to-end
delays may be lengthened by Gateways Proxys …
An argument for small/average size network domains
Friday 28th September 2001
CERN Workshop Ethernet 17
AgendaDeterminism and Qos with Ethernet "Vintage" Ethernet Switched Ethernet
Which QoS implementation ?
An overview of vendors proposals Fieldbus interconnection with Ethernet/TCP/IP Fieldbus protocols over Ethernet/TCP/IP IDA proposal
Just one word about securityWhat are the real cost parametersConclusion
Friday 28th September 2001
CERN Workshop Ethernet 18
Vendors proposalfirst scheme (1/2)
"I offer solutions to interconnect my fieldbus and Ethernet"
A good idea … Profinet (Siemens) WorldFIP …
Friday 28th September 2001
CERN Workshop Ethernet 19
Vendors proposalfirst scheme (2/2)
But not so simple… Can I support IP applications on the fieldbus,
without disturbing real time traffic ? Can I forward fieldbus protocol messages
through Ethernet segments ? Can I have an integrated solution for the
networks management ? Delays introduced by proxies and gateway
The vendor must offer a complete solution !
Friday 28th September 2001
CERN Workshop Ethernet 20
Vendors proposalssecond scheme (1/3)
"I take my classic Fieldbus protocol and carry it on Ethernet with TCP or UDP"
A good idea … Modbus/TCP (Schneider) Ethernet/IP (Rockwell, IAONA) HSE (Fieldbus Foundation) WorldFIP EtherFIP …
Friday 28th September 2001
CERN Workshop Ethernet 21
Vendors proposalssecond scheme (2/3)
But not so simple… TCP/IP protocol stack is designed for
Client/server application, not for 1 producer/N Consumers exchanges
Needs switched Ethernet to insure determinism Needs QoS management if mixed traffic with
other IP applications is needed How manage full redundancy if needed ? How manage station synchronization if needed
?
The protocol encapsulation specification is not
enough !
Friday 28th September 2001
CERN Workshop Ethernet 22
Vendors proposalssecond scheme (3/3)
For sure not the cheapest solution ! Needs for industrial packaged Ethernet
products Needs engineering skill if hard real
time constraints
What is the value added for the end user ?
All this stuff doesn't make the initial fieldbus protocol better !
Friday 28th September 2001
CERN Workshop Ethernet 23
IDA proposal (1/2)
Interface for Distributed Automation NDDS, Network Data Delivery Service
Middleware Covering OSI layers 4 to 7 Producer/Consumer Model Broadcast and Multicast Adapted to real time traffic
Friday 28th September 2001
CERN Workshop Ethernet 24
IDA Proposal (2/2)
EthernetIP
TCPUDP
SN
MP (T)F
TP S
MT
P HTT
PND
DS
ParametrizationEventAlarm Download DiagnosticsProcess
Image
IDA Object Model
Syst
em
M
anagem
en
t
Programming Interface
Friday 28th September 2001
CERN Workshop Ethernet 25
Conclusion on Proposals
Various solutions… For various uses ? Most of them not yet mature What future for IEEE 1451 ?
Friday 28th September 2001
CERN Workshop Ethernet 26
AgendaDeterminism and Qos with Ethernet "Vintage" Ethernet Switched Ethernet
Which QoS implementation ?
An overview of vendors proposals Fieldbus interconnection with Ethernet/TCP/IP Fieldbus protocols over Ethernet/TCP/IP IDA proposal
Just one word about securityWhat are the real cost parametersConclusion
Friday 28th September 2001
CERN Workshop Ethernet 27
Security IssuesDo not mistake Ethernet and Internet ! Consider the plant floor network as an Intranet Networks manufacturers & designers have the
know-how There are solutions to secure private IP networks (I hope that) plant floor networks (will) make use of
them
Do not mistake Security and safety ! Fieldbus manufacturers have the know-how Mechanisms used to provide safety in classic
fieldbus have to be implemented in Ethernet solutions
Friday 28th September 2001
CERN Workshop Ethernet 28
AgendaDeterminism and Qos with Ethernet "Vintage" Ethernet Switched Ethernet
Which QoS implementation ?
An overview of vendors proposals Fieldbus interconnection with Ethernet/TCP/IP Fieldbus protocols over Ethernet/TCP/IP IDA proposal
Just one word about securityWhat are the real cost parametersConclusion
Friday 28th September 2001
CERN Workshop Ethernet 29
Cost parameters (1/3)
Engineering costs Components standardization Well-known design rules
Equipement costs Off-the-shelf components / Customs
components Proprietary protocols / open standards
Installation costs Number of different networks Number of cabling systems
Friday 28th September 2001
CERN Workshop Ethernet 30
Cost parameters (2/3)Commissioning costs Operators training System testing Proven technology & solid design
Maintenance costs Various components resellers Automatic discovery of new components Avaibility of remote configuration & testing
devices
Friday 28th September 2001
CERN Workshop Ethernet 31
Cost parameters (3/3)
Operating costs Minimization of operating HMIs Automatic cold & warm start
Evolution Costs
Friday 28th September 2001
CERN Workshop Ethernet 32
AgendaDeterminism and Qos with Ethernet "Vintage" Ethernet Switched Ethernet
Which QoS implementation ?
An overview of vendors proposals Fieldbus interconnection with Ethernet/TCP/IP Fieldbus protocols over Ethernet/TCP/IP IDA proposal
Just one word about securityWhat are the real cost parametersConclusion
Friday 28th September 2001
CERN Workshop Ethernet 33
So, Why Ethernet ?Alternative vs. The "Fieldbus War" ? Guarantee of durability Multiple vendors could decrease costs
Seamless data paths From the plant-floor to the office For controllers, PLCs and ERP Systems
One network type One technical expertise A global network management
Friday 28th September 2001
CERN Workshop Ethernet 34
One Network fits all : an utopia ?
The market today : proprietary solutions Specific network hardware Specific protocols More or less compatible devices Vendors differences based on technical
performances
A challenge for setting a new market ? COTS network hardware One standard protocol for RT applications A large range of Ethernet devices Vendors differences based on value added services A new space for systems integrators ?