［ Electronic Equipment ］ Communications Equipment

Technologies for Robust Switches(Switching Hubs)
Keywords

Kazushi Ono,
Tatsuya Okuro,
Yasushi Tateishi

Robust switch, Industrial switch, Precision time protocol, Band control

Abstract

If an industrial system supporting our infrastructures is compared to ahuman body, a computer network would be its nervous system. Similar how
healthy people are not aware of the presence of the network of their own central
nervous system in daily life, people are also not aware of the presence of a computer network itself.
When any network fault occurs, such a negative effect will travel over a networkʼs system. As such, the market demands on the reliability of more strict andhigher-level network devices.
In order to offer a suitable product for an industrial computer network, we
proposed a concept of our new network switch as a “robust switch” for industrial
computer network. It features “an operation without stopping switch,” ”no missing data,” and “no data transmission latency.” Based on this concept, we aredeveloping and manufacturing industrial switching hubs.

1 Preface
The duties of an industrial network are that thecontrol data, video data, audio data, and other information can be correctly transmitted without delay. Inorder to maintain operation of these duties, we consider it necessary to realize the following threeitems:( 1) An operation without stopping switch
The operation of network equipment and communication lines must be maintained by 24/7 without causing the performance loss.
( 2 ) No missing data in the communication network
systemIn industrial systems, the network gear will beplaced where external conditions are challenging(negative impact by other devices emitting electromagnetic waves or by temperature.)( 3 ) No data transmission latency
Under the conditions of network communication lines with different communication conditionsin terms of transmission distance, communication
bandwidth, and communication modes, the network
gear shall maintain network communication without
missing data or transmission latency.
We are developing and manufacturing industrial switching hubs that play an important role inindustrial networks. We realized three items in
our industrial switching hub, “MEISWAY SW600”(ʻSW600ʼ hereafter.) This paper introduces the features of these Meiden switching hubs.

2 Securing Real-Time Performance
In addition to the duties imposed on industrialnetworks as deﬁned, Meiden industrial switchinghubs newly introduced a concept of “Security ofReal-time Performance.”
In industrial systems, there are pressing
requirements of “capturing the same phenomenon
around the same time” and “make the target
controlling equipment work under the same realtime performance of other equipment.” For example, a power grid protection system is protected bysimultaneously collecting, at an accuracy of microseconds, the current level data of the key equipment
like substations distributed in the power network.
Also, in order to operate a machining tool line in
Factory Automation (FA) system, it is essential tomake synchronizing time accuracy control.
Conventionally, this kind of information-basedcontrol had been conducted by dedicated machinery for data acquisition and data-based control.
When a network technology called “Precision Time
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15

Protocol (PTP)” is introduced to network devices,
clock-accuracy control can be realized without using
the large-scale dedicated special equipment.

3 Robust Switch
Since 2015, we have been developing a product series of industrial switching hubs with excellent
robustness and toughness to support infrastructure
systems. We have developed such products basedon the concept of a “robust switch” meeting thethree conditions discussed in the Preface. Table 1
shows the outline of a robust switch.
We provide our switching hub as an industrial
application product which differs from ordinary LANproducts. Our products are for network systems forthe mission-critical infrastructures. We aim ourswitching hub to maintain the high level reliability
necessary for such network application. We introduce the technological elements which are requiredin realizing the robust switch concept products.

3.1 Network Redundancy
For industrial network devices, it is important
to maintain network connectivity against the likely
unplanned network outages, so we secured redundancy by making a backup communication line toTable 1 Outline of a Robust Switch

make the communication system redundant andmaintained the connection by swapping.
Fig. 1 shows the function of our Ring Topology
Protocol (RTP) – our high-performance routing system in our switching hub. Our RTP is the revised
version of Rapid Spanning Tree Protocol (RSTP) ina ring topology network.
For the ring topology network, by making adesignated blocking port in advance, it can avoidloops. In case of failures in the communications link,the designated blocking port will be moved to thetroubled spot (bypass) to maintain the communication. Regarding RTP functions in our switching hub,from the early design stage, we worked on shortening the bypassing time (communication break-offtime.) For the latest model, the bypassing process iscompleted in 50ms to 200ms. This is our guaranteed value for maximum 32-node at the largest
system conﬁguration.

3.2 PTP Features
For the system to maintain stable operation, itis preferable to manage and control it under synchronized clocks instead of working under each different clock time.
For example, in tracing the log of communications failures, it is easy to check the time context ofthe data after the occurrence of communications
failures, so long as the time information is synchro-

We show the essential factors in making a “robust switch” as anindustrial switching device.
Method of realization

Measures against Adoption of industrial parts
environment
Adoption of high-reliability(temperature)parts
Measures against Adoption of sulfur-resistantenvironmentparts(anti-corrosion)
Protection and hermeticalsealing of corrosive sections

Securesoundcommunication data(use ofloss-freepackets)

Redundancy(power supply)

Redundancy and maintenance in energized state

Redundancy(lines and communications)

Bypassing function by using
a faster loop circuit bypassing
function (reduction of losstime)
Redundancy of lines (redundant configuration)

Priority control

Secure bandwidth based on
the priority (bandwidthcontrol)

Measures against Low power consumption
environment(temperature)
Stabilization Precise timeof control
protocol

16RTP

Measures against Adoption of anti-noise partsEMC Compliance Anti-noise design (structuraland electrical design)

Adopt IEEE 1588-compliant
devices

MEIDEN REVIEW Series No.177 2019 No.3

Realize by costs

Robustdesign forhardware( Toughdesign)

Items to berealized

DBCA－
Blocking port
default condition＝ Logical block

Diversion by RTP

RTP
Fault occurrence

Realized by the switching function

Contents ofrealization

RTP hub－

D

Move the blocking port
to the faulty port

BAC－The blocking port
movement by RTP: RTP network: Flow of data

Fig. 1

Function of RTP

This diagram shows a ring topology network by RTP and thebehavior of a blocking port moving from the default blocking port
A to the faulty port D.

Monitoring & control data
ServerMissing important data
IoT data

Machine site

NetworkMonitoring & control data
Analysis server
IoT data

Monitoring room

Discard the data at
a good timing due
to the excess ofbandwidth

Images Audio Waveforms
Machine site

Fig. 2

State of Discarded Packets Caused by Excess of Bandwidth

In a network, bandwidth may overﬂow momentarily and the network may discard important data. By time-dividing the network using thetime synchronization function, the bandwidth can therefore, be completely separated and important data can be prevented from being
discarded.

nized. In a system where scheduled management isstrict, stable system operation is possible if theclock time of each equipment is synchronized. Our
PTP features are as itemized below.
( 1) The PTP works as a standard clock or terminalclock.
( 2 ) Accuracy of synchronism is kept within ±200ns(via the PTP-compliant switching hub).
( 3 ) Clock time synchronization will be completed
within 60 seconds after the power supply is ON.
( 4 ) Pulse signal output is generated at a predetermined period.
( 5 ) Anomaly detection will be notiﬁed when thespeciﬁed accuracy cannot be maintained.
( 6 ) The present status of synchronism is notiﬁed.

3.3 Bandwidth Control Function
With the trend of various types of data going
through the industrial network, prioritization is madeagainst each data type. Formerly, we mostly managed the control data but from now on, real-timedata of video, audio, and Internet of Things (IoT) will
be on the network.
In order to handle such various data, it isessential to add a bandwidth control function to“secure the important data by ensuring the bookedbandwidth at the synchronized clock time.” Conventional bandwidth control technique depended on
performance of dedicated network device withswitching engine but from now on, as our future
option, we are also working on to adopt PTP asmentioned above as per IEEE 802.1 Time-SensitiveFig. 3

SW600

This is a gigabit layer-2 switch conforming to the B-402 electricalstandards of The Japan Electric Association (Digital Protection
Relays and Protection Equipment.) It is replaceable as a successor machine for the SW500.

Networking (TSN). In this IEEE 802.1 TSN, it applies
PTP and is a method to secure the bandwidth
just like Time-Division Multiplexing (TDM) method.
Fig. 2 shows the state of Discarded Packets Caused
by Excess of Bandwidth.

4 Commercialization of RobustSwitches
We adopted a new switching engine for ourrobust switching hub products. We released theSW600 with new switching engine in February
2015. Fig. 3 shows an external appearance of theSW600. This product is a successor model ofour previous industrial switching hub, “MEISWAYSW500” (ʻSW500ʼ hereafter.) Our SW600 was designed to serve as a platform of robust switches with
new-generation switching engines. Table 2 shows
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Table 2 Transmission Specifications of SW600

Table 3 Environmental Specifications of SW600

Maximum 16 ports of 10/100/1000BASE-T and maximum 6 optical ports of 100BASE-FX or 1000BASE-LX can be installed.

The top panel of this product is free from ventilation holes andthe operating temperature range is −20 to 55℃. Compared with
the SW500, the power consumption is reduced by 30% and thetotal mass is approximately 30% less.

ItemTransmission specification

Switching mode

Store and forward

Switch capacity

13.7Gbps
2.66Gbps (for full duplex/full port
100Mbps)

Transmission system

1000 Connector used: LCBASE- SMF applicable
LX
10km and long distance (40km)
applicable
Error output terminal

1 contact

MAC address capacity

8000 pcs.

Flow control
VLAN

Environmental
specification

Type

UT226/＊＊＊A(＊＊＊changeable with typedescription)

Power connector

3P inlet type (AC)/3P terminal block (DC)Input power voltage range

AC85〜242V
47〜63Hz/DC80〜143V

Power consumption (in operation)

25W or less

Operating temperature range−20〜55℃Full-duplex/half-duplex

Port10/100/1000
16 ports (4 ports for optical ports andconfig- BASE-T
combo ports)
uration
6 optical 100
Connector used: SCports
BASE- Multi-Mode Fiber (MMF ) applicableMax.
FX
Single-Mode Fiber (SMF ) applicable

Isolation voltage (Source primary – AC 2000V for 1 minute
FG or SG)Insulation resistance (Sourceprimary – FG or SG)

DC 500V 5MΩ or above

IEEE 802.3x (full duplex)
Back pressure (half duplex)

Power noise immunity

Impulse noise
2kV, 50ns/1μs

IEEE 802.1Q conforming tag and port
base VLAN

MassApprox. 4kg

External dimensions

W255 × H88 × D250mm(protruded parts excluded)

Applicable standards

B-402 Standards-compliant(except inrush current)

Error packet filteringfunction

Short packet, long packet, FCS error
packet, symbol error packet

Network control

SNMPv1 (conforming to RFC1157),
MIB Ⅱ

Network operationtelnet・http・ICMP・IP

Storm prevention

Revocation enabled by setting forbroadcast, multicast, and address
unknown packet

Serial console port

By round connector conforming toEIA/TIA-232-E

Setup saving, writing,firmware updating

Via Web (http) or serial port

transmission speciﬁcations of SW600 and Table 3
shows environmental speciﬁcations of SW600. (Theprecise time protocol function is optional. The function of bandwidth control will be provided in thefuture.)

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Item

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5 Postscript
As an industrial network device in support ofgood network connection of industrial infrastructure,
we will provide our switching hub products withhigh-level functions as previously mentioned. In
doing so, we will keep providing network devices
which realizes higher reliability.
・All product and company names mentioned in this paper are
the trademarks and/or service marks of their respective owners.