Real-Time Protocols
1 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Train Communication Network
IEC 61375-2
Real Time Protocols
Message Services
Real-Time Protocols
2 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
RTP- Message Services
1. General Principles
2. Variables
3. Messages
1. Principle of Message Data communication
5. Software structure
2. Link Layer Interface
4. Transport protocol
3. Networking and Routing
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Varialbles
6. Networking
6. Application Interface
Real-Time Protocols
3 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
TCN Stack
Lin
k
Ph
ys
ica
l N
etw
ork
-in
de
pe
nd
en
t
Pro
toc
ols
periodic
medium access
process data
sporadic
medium access
message data
variables messages
presentation
(session)
presentation
supervisory
access
medium-independent signalling
mechanical and electrical elements
(transport)
(network)
supervisory data
physical signalling
void
Layer 2 interface
Layer 7 interface
Layer 1 interface
urgent less urgent
Layer
Management
physical media
Real-Time Protocols
4 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Functions and Devices
Each vehicle supports a number of standardized functions.
The Train Bus accesses vehicles without knowing their internal structure.
The train bus accesses functions rather than devices .
These functions are implemented by one or several vehicle bus devices, or even by the gateway itself.
vehicle bus
sensor bus
Train Bus
device
air condition
doors
brakes
doors
passenger info
device device device device
sensors/
actors
bus
master
The gateway deduces the device from the function and routes messages.
train-vehicle
gateway
Real-Time Protocols
5 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Client-Server Service
replier
time-out
The Application Interface for Messages provides a "Call with Reply" service
Network Caller Replier
Call_Request
Call_Confirm
Reply_Request
time
Transport Transport
Receive_Request
Receive_Request
Receive_Confirm
Applications communicate among themselves on a Client/Server basis.
Tasks use the same communication scheme:
• within the same processor
• within the same vehicle bus and
• within the Train Communication Network
Real-Time Protocols
6 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Transport Protocol for Messages
train bus
F F F F F
the message transport protocol is executed by the vehicle bus devices
in vehicles without vehicle bus, the message transport protocol
is executed by the train bus node
gateway gateway node vehicle
bus
vehicle bus
the message transport protocol applies also within
the same bus and within the same device.
functions
F F F F F F F F
The Message Transport Protocol runs in each device
The transport protocol ensures a reliable communication from end-to-end between Application Functions.
Real-Time Protocols
7 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Message Data Transmission
Messages are lengthy, but not so urgent data.
They are used e.g. for diagnostics, passenger information, down-loading.
Messages are segmented into packets for transmission.
Data, ackowledgements and control packets form the Message Data .
Message Data are sent upon demand between two process data cycles.
The sender and receivers of Message Data are queues (no buffers):
Bus
data packets
acknowledgements
Application Processes
send queue
receive
queue
Real-Time Protocols
8 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
End-to-end Transport Protocol
WTB segment MVB segment
Porting the MTP to a bus providing connectionless datagrams is easy
link
network
transport
session
presentation
link
network
transport
session
presentation
(router)
application application
link
physical physical physical
Message
Transport
Protocol
link
network
transport
session
presentation
link
network
transport
session
presentation
(router)
application application
link
physical physical physical
MVB segment
Real-Time Protocols
9 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
RTP- Network Layer
1. General Principles
2. Process Data
3. Messages
1. Principle of Messages communication
5. Software structure
2. Link Layer Interface
4. Transport and Session protocol
3. Networking and Routing
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Variables
6. Networking
6. Application Interface
Real-Time Protocols
10 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Packet Routing
Packets are transported in Message Data frames as datagrams which contain the full origin and final address.
The gateway operates as a router : it forwards packets from bus to bus without keeping knowledge of previous packets.
train bus
origin
station final
station
Message Data frame
vehicle bus vehicle bus
source
source
source
destination
destination
net_adr
ne
t_a
dr
ne
t_a
dr
destination
gateway gateway gateway gateway
Real-Time Protocols
11 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Message Data Frames
DD WTB
MVB
8 bits
LLC
8
SD
8
transport data unit
8
MTC
DD
12
typ
e
4
SD
12 8
mo
de
4
link header network
addresses
transport data unit
8
MTC
8 8 8 8
8 8 8 8
final origin
Link Data Unit - common to all busses
size
8
size final origin
Message Data have the same format on the vehicle or on the train bus.
They are datagrams, which carry the full origin and final address
DD: destination device
SD: source device
LLC: link layer control
MTC: Messsage Transport Control
Message Data carry data packets, acknowledgements and control data.
Real-Time Protocols
12 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Networking Different Busses
2-level hierarchy
I ntelligent stations and sensors/actuators are
attached to the vehicle bus
3-level hierachy
Sensors are attached directly or by a sensor
bus
1-level hierarchy
Equipments are attached to a node-internal
backplane bus which plays the role of a vehicle bus
train level
stations
vehicle bus
sensors & actuators
backplane bus vehicle bus
sensor bus
gateway gateway node
The real-time protocols allow to interconnect different vehicle structures
Real-Time Protocols
13 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network Layer Operation
The network layer is responsible for the routing of packets
(data, acknowledgement and control) through the network
It is connectionless, i.e. it retains no knowledge about previous packets belonging to the same message
Routing is done on the base of two directory tables:
• station directory
• function directory
These directories are set up by the application or by network management.
Routing relies on the network addresses contained in each packet.
The network layer has no protocols (no segmentation / reassembly), but
address calculation is complex.
Real-Time Protocols
14 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Reference Architecture
UP1
UP2
UPf
Agent
me
sse
ng
er
UP1
UP2
UPf
Agent
me
sse
ng
er
UP1
UP2
UPf
Agent
me
sse
ng
er
UP1
UP2
UPf
Agent
me
sse
ng
er
Application
Processes
Train Bus
Ve
hic
le B
us
UP1
UP2
UPf
Agent
me
sse
ng
er
UP1
UP2
UPf
Agent
me
sse
ng
er
UP1
UP2
UPf
Agent
me
sse
ng
er
rou
ter
node node node
station
station
Ve
hic
le B
us
LL
LL LL
LL
LL
LL
L
L
LL
L
L
rou
ter
A station is a (vehicle or train bus) device capable of message communication.
All Application Processes (UPs, Agents) communicate through the Messenger.
link layer
User Processes
Real-Time Protocols
15 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Example of an Actual Configuration
Vehicle Busses
Ve
hic
le B
us
UP1
UP2
UPf
Agent
messenger
rou
ter UP1
UP2
UPf
Agent
me
sse
ng
er
UP1
UP2
UPf
Agent
me
sse
ng
er
rou
ter
#101
#102
#103
#122
#123
#125
#156
#157
#158
0021
0022
0023
0022
0023
0025
56
57
58
Physical Address
#002
0002
#003
0003 #004 (Station Identifier)
#001 #011 #001 node 05 node 06 node 07
0001 0020 56 0020
Station Identifier
repeater
UP1
UPf
Agent
me
sse
ng
er
0004
(physical
address)
Manager
Train Bus
Real-Time Protocols
16 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Reference Gateway
Agent User
Processes
User
Processes User
Processes
Messenger
Message Transport Protocol
application interface AM
Application Processes
WTB physical medium MVB physical medium
Session Layer
Transport Layer
Network Layer
Link Layer
Physical Layer
NodDi
Application Layer
StaDi
A gateway has a router and more than one link layer
Agent = Station Management Agent
( for parametrizing, down-loading, configuration, debugging, performance measurement)
Router LM LM
WTB
Link Layer MVB
Link Layer
FunDi
Real-Time Protocols
17 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: System Point Of View
Train Bus
Node # 01 Node # 03 Node # 02
station
(agent)
#002
station
(agent)
#003
station
(agent)
#020
station
(agent)
#001
station
(agent)
#003
station
(agent & manager)
#100
The System Engineer identifies stations attached to train bus nodes.
The interconnection of the stations is not visible (no, 1, 2,... vehicle busses).
The train bus node counts as one station.
The communicating entities are the Agents and the Managers.
The nodes route the packets through their Station Directory
station
(agent)
#001
Real-Time Protocols
18 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Train Bus Addresses
attended driver's cab
03 04 05 06 07 08 02 01
principal direction of travel
UIC applications address vehicles by their position relative to the head of the train.
The Train Bus operates with nodes addresses, which is the position of a node relative to the master node (address 01)
01
(master) 02 03 05 06 04 07 08
The train inauguration gives each node its position and the direction of the master.
hauled vehicles pushed vehicles
Since a vehicle may have one, two or no operative node, there must exist a mapping between node address and UIC application address.
63
The real-time protocols only rely on the TCN addressing.
Real-Time Protocols
19 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Example Of Communication
UP1
UP2
UPf
Agent
me
sse
ng
er
Train Bus
Node # 05 Node # 08 Node # 06
#002
0002
#103
0003
0100
Station
Identifier
#002
0002
#003
0003
#004
0004
#002
0002
#003
0003
#232
0232
0200
Vehicle Bus
(Physical)
Address
#001
LL
Ve
hic
le B
us
Ve
hic
le B
us
Ve
hic
le B
us
Real-Time Protocols
20 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Example of Frame Exchange
Back
0100 0133 08 (05) 133 232
08 05 08 05 133 232
VB
origin
TB
intermediate
0232 0200 (08) 05 133 232
simple routing
0200 0232 05 (08) 232 133
05 08 05 08 232 133
0133 0100 (05) 08 232 133
simple routing
simple routing
Forth
VB
final
simple routing
VB
origin
TB
intermediate
VB
final
physical addresses network addresses
application knows that node #8 is accessed over Station #100
(its gateway)
node #05 inserts its current node address
node #8 routes Station #232 to VB Address 0232 (simple routing)
node #08 checks
its correct TB address
node #05 routes Station #133 to VB address 0133 (simple routing)
Station #232 acknowledges to Station #200.
Real-Time Protocols
21 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Station Directory
Station Link Layer Physical Address
003 MVB1 0003
005 MVB1 0005
103 MVB2 0003
223 Parallel_Bus 203040
The Station Directory in the network layer routes the messages on the base of their station address to the corresponding link layer and device address
Real-Time Protocols
22 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Routing Between Two Vehicle Busses
Train Bus
Vehicle Bus 1
gateway
Two (or more) vehicle busses may be attached to a train bus gateway.
The gateway routes message data according to the network address
from vehicle bus to vehicle bus or from vehicle bus to train bus.
Vehicle Bus 2
device group 1 device group 2
The station identifier must be unique under a given train bus node.
station #001
bus address 0011 bus address 1011
bus address:
#002 #003 #004 #005 #006 #007 #008 #009 station:
0012 0013 0014 0015 0012 0013 1014 1015
Real-Time Protocols
23 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Sensor Bus Configuration
Train Bus
Vehicle Bus
UP1
UP2
UPf
agent
me
sse
nger
rou
ter
agent
#101 agent
#102
agent
#002
UP1
UP2
UPf
agent
me
sse
nger
rou
ter
agent
#003
agent
#100
Sensor Bus
StaDi
Station
#004
Station
#001
StaDi
Real-Time Protocols
24 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Sensor Bus Path
Train Bus
Ve
hic
le B
us
me
sse
nger
UP1
UP2
UPf
agent
me
sse
nger
rou
ter
Sensor Bus
Station #206
Station Identifier
0200
#202
0202
Station Identifier
VB address
Node # 08
#294 4
Station Identifier
SB address #292
2 #293
3
1
station link device
#294 SB 4 SB
VB
0206
0202
0204
#002
0002
#103
0003
#133
0133
0100
Station Identifier
VB address
Node # 05
Ve
hic
le B
us
StaDi
StaDi
station link device
#206 VB 206
#294 VB 206
Station Directory
UP1
UP2
UPf
agent Node # 05
rou
ter
Real-Time Protocols
25 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: User Point Of View
F3 F2 F1 F3 F2 F1 F3 F2 F1
Train Bus
Node # 01 Node # t Node # 02
The user sees functions attached to nodes.
The node itself is not a function - but the node device can implement functions
Real-Time Protocols
26 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Function Architecture
UP1
UP2
UPf
agent
me
sse
nger
Application
Processes
Train Bus
UP1
UP2
UPf
agent
me
sse
nger
rou
ter UP1
UP2
UPf
agent
me
sse
nger
rou
ter UP1
UP2
UPf
agent
me
sse
nger
UP
#101 UP
#102
UP1
UP2
UPf
agent
me
sse
nger
rou
ter
UP
#100
Sensor Bus
FunDi
UP1
UP2
UPf
agent
me
sse
nger
FunDi
FunDi
UP1
UP2
UPf
agent
me
sse
nger
FunDi
Fun
Di
Fun
Di
Fun
Di
The communicating entities are functions in the different stations
Ve
hic
le B
us
Real-Time Protocols
27 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Function Directory
Function Station
2 003
5 104
7 0 (local)
12 30
Station Link Layer Physical Address
003 MVB1 0003
005 MVB1 0005
103 local 0
223 Parallel_Bus 203040
Function Directory
Station Directory
The Function Directory maps the function to the corresponding station
Real-Time Protocols
28 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Address Kinds
Physical Address: identifies a device on a bus - can be a broadcast address.
gateways have more than one physical address
each frame carries the source and destination address.
Link Identifier: In a gateway, link layers are identified by their address (e.g. 1,2)
Network Address:
Each frame carries the origin and final network address
Link Service Access Point Only one default LSAP is used in TCN (unused).
Application Address: system/user
individual/group
node
station or function
next station
The application process identifies the remote application process through its network address.
All other addresses are deduced from this one. 1 bit
1 bit
6 bits
8 bits
8 bits
The network address is the concadenation node + (station or function)
Real-Time Protocols
29 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Address Calculation
16-bit Function Address
1 = System (Station)
train bus node next station (device) function (user process)
(1/255) Function Identifier 0 0/1 node
0 = individual
1 = group
1 (1/254) Station Identifier node
0 = User (Function)
16-bit Station Address
Application Address
Station
Link and Physical Address
Function
Directory
Station
Directory
station (agent)
Real-Time Protocols
30 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Message Consistency and WTB Topography
if a topography change occurs while a message is transmitted,
the remaining packets may be delivered to the wrong node.
if a topography change occurs between a call and a reply message,
the reply message may be delivered to the wrong node.
To this effect, each WTB node maintains a topography counter, which is incremented each time the topography of the WTB changes.
This misaddressing will be detected in most cases.
When nodes swap their addresses, undetectable situations may occur.
All packets of a message exchanged over the vehicle bus carry the topography counter in place of the local node address (which is redundant).
If a station detects that topography changed, it cancels only that conversation.
When topography changes, each WTB node signals its messenger,
which cancels all ongoing message data communication over the WTB and flushes the queues of the WTB link layer.
Transport level:
Session level:
Real-Time Protocols
31 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Impact of Topography Change on Communication
A topography change cancels indistinctly all conversations over the WTB.
It would not be necessary to cancel conversations between nodes which
did not change their addresses.
However, it is not possible to guarantee that the topography change did not affect the addresses of either partner.
Even if no node address changed, it is not possible to guarantee that the reason why this address was chosen still holds.
Even if the node address and function did not change, the application mapping may not anymore be correct, since it was based on some dynamic property of the node which changed in between (e.g. attended driver seat).
Therefore, communication must be cancelled indistinctly when the transport
protocol becomes unable to guarantee correct delivery in all cases.
Real-Time Protocols
32 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Network: Inclusion of Topography Counter
Train Bus
08 CR 00
Final Node Origin Node
X X
LTC5 CC 08 X X
08 DT LTC5 X X
LTC5 AK 08 X X
LTC8 CR 05
FN ON
X X
05 CC LTC8 X X
LTC8 DT 05 X X
05 AK LTC8 X X
consumer
station
"producer"
Node # 05 "consumer"
node # 08 Node # 06
Ve
hic
le B
us
FN ON
producer
station
LTC5
FN ON
LTC8 Local
Topography
Counter
The gateway substitutes the topography counter in place of the node address
Ve
hic
le B
us
Real-Time Protocols
33 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Transport and Session Protocol
1. General Principles
2. Variables
3. Messages
1. Principle of Messages communication
5. Software structure
2. Link Layer Interface
4. Transport and Session Protocol
3. Networking and Routing
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Variables
6. Networking
6. Application Interface
Real-Time Protocols
34 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Transport: Message Transport Protocol
The MTP opens a connection for each call message and
closes it after the reply message has been received.
It uses in each direction a sliding window protocol with a window size of 1…7
and positive acknowledgement (negative is also possible)
The frame and window size are negotiated at connection opening.
The origin and destination addresses uniquely identify the connection.
A connection reference prevents duplication of messages.
It is half-duplex (call and reply cannot take place at the same time)
A caller reference pairs messages in a multi-tasking station.
Real-Time Protocols
35 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Transport: Frame Exchange in one Direction
Transport
DATA (0)
ACK (1)
DATA (1)
DATA ( last)
ACK (last)
ACK (2)
Transport Session
(Consumer)
alive
time-out
connect
time-out
ack
time-out
late acks
Connect Request
Connect Confirm
i
k
k
k
v
v
v
Session
(Producer)
sm_message_ind
sm_connect.ind
tm_message.req
sm_message.cnf v
Connection
Transfer
Disconnection
Network
sm_connect.cnf
A transport exchange consists of three phases: connection, transfer and disconnection
In this example, the transfer takes place with a window size of 1
Real-Time Protocols
36 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Session: Call And Reply Over A Network
Vehicle
Bus Train
Bus Vehicle
Bus application
process application
process
time
messenger
messenger
connect
request
connect confirm
data
ack
route
r
route
r
Reply_request
messenger
messenger
connect
request
connect confirm
data
ack ro
ute
r
route
r replier
time-out
Call
Phase
Reply
Phase
Receive_confirm
Call_confirm Reply_confirm
connect
data
connect
data
Call_request Receive_request
server
works
Real-Time Protocols
37 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Software Structure
1. General Principles
2. Variables
3. Message Data
1. Principle of Message Data communication
5. Software structure
2. Link Layer Interface
4. Transport and Session Layer
3. Networking and Routing
1. Principle of cyclic Process Data broadcast
2. Traffic Stores principle and implementation
3. Process Variables and Datasets
4. Software structure
5. Application Layer Interface for Process Variables
6. Networking
6. Application Interface
Real-Time Protocols
38 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Software: Message Software Structure
network
MAA
MLA MLA
transport
network
MAA
MLA MLA
transport
network
MAA
MLA MLA
transport
Application
Process 1
Link 2
Application
Process 2 Application
Process 3 Application
Process n
Bus 1 Bus 2
Application
Message
Interface
Link Interface
Messenger
Process
Instances Network Layer
Transport Layer
AMA AMA AMA AMA
Link Processes for router station only Link 1
Function Directory
Applications access the network through the Application-Message Interface (AMI)
This interface supports multiple simultaneous calls and replies
MLA MLA
LMA LMA
Session Layer
Station Directory
Real-Time Protocols
39 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Software Interfaces
Messenger
Link Layer Kern
el
Physical Layer
Interface
Physical Layer
Process Data Interface
Message Data
Interface
Porting of the TCN software to different platforms is eased by well-defined interfaces between the communication software and the application, the kernel and the link layer.
The bus-specific link layer also has a defined interface to the physical layer.
Application
Real-Time Protocols
40 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Processor Interface Library (PIL)
The Messenger relies on services of the kernel
(e.g. memory allocation, timers, task wake-up)
To ease portability, the kernel services are defined in an interface module, the Processor Interface Library (PIL).
The PIL provides a set of basic functions as any commercial kernel (e.g. VRTX, WinWorks) can deliver.
Writing the PIL module is part of the porting process. In many cases, the PIL modules consists only of a redefinition of existing functions.
Real-Time Protocols
41 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
PIL Functions
Block copy pi_copy8, pi_copy16
Interrupt Control pi_disable, pi_enable disables/enables all interrupts pi_call_hw_int software trap
Dynamic Memory pi_alloc, pi_free allocate memory block, free it.
Queues: pi_create_queue create queue, define priority pi_accept_queue check if a mesages is in the queu pi_send_queue insert a message in the queue pi_receive_queue suspend until message or time-out
Semaphores pi_create_semaphore create semaphore, define priority pi_inquiry_semaphore check semaphore value pi_pend_semaphore decrement sema, suspend if 0. pi_post_semaphore increment semaphore
Tasks pi_create/delete_task not part of PIL pi_lock_taks begin critical section pi_unlock_taks end critical section
Time-outs pi_create_time-out define function to call pi_enable_time-out enable a time-out and specify value pi_disable_time-out disable time-out pi_delete_time-out delete time-out
Real-Time Protocols
42 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
AMI Procedures
Caller Interface
am_call_request
am_call_confirm
am_call_cancel
sends a call message
called on arrival of the reply message (or error)
cancel this call
Replier Interface
am_bind_replier
am_unbind_replier
am_receive_request
announces the service to the messenger
retires the service
expresses readyness to receive
am_receive_confirm called on arrival of a call message
am_reply_request sends the reply message
am_reply_confirm terminates the reply
am_receive_cancel cancels a receive or an unconfirmed reply
Directories (network layer access)
am_directory_insert inserts an entry in the directory
am_directory_remove removes an entry in the directory
Real-Time Protocols
43 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK
Real-Time Protocols
44 IEC Train Communication Network IEC 61375 - Clause 2
1999 December, HK