CN107135045B - Substation's adaptive network and its clock synchronous safety method based on difference detection - Google Patents
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- 230000003044 adaptive effect Effects 0.000 title claims abstract description 9
- 230000003287 optical effect Effects 0.000 claims abstract description 72
- 238000004891 communication Methods 0.000 claims abstract description 5
- 238000013475 authorization Methods 0.000 claims description 7
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
- H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
- H04B10/077—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using a supervisory or additional signal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0647—Synchronisation among TDM nodes
- H04J3/065—Synchronisation among TDM nodes using timestamps
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/32—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials
- H04L9/3297—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols including means for verifying the identity or authority of a user of the system or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials involving time stamps, e.g. generation of time stamps
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/0079—Operation or maintenance aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/0079—Operation or maintenance aspects
- H04Q2011/0083—Testing; Monitoring
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Abstract
The invention belongs to intelligent substation technical field of network security more particularly to a kind of substation's adaptive networks and its clock synchronous safety method based on difference detection.Network includes: optical network unit ONU, synchronous optical line terminal OLT and EPON protocol processor；There are two interface states having the same forever by each ONU, using the redundant configuration of active and standby link；EPON protocol processor is communicated by Multi-point Control Protocol with ONU.Method includes: that timestamp is passed to each ONU by EPON protocol processor；Whether two interfaces that OLT compares ONU receive the consistency for the synchronized timestamp that message and message carry within the regulation time difference, if it is not, then there is security threat, clock synchronization is not adjusted；If so, whether OLT detection round-trip delay RTT value difference value is more than defined threshold value, if so, there is security threat, clock synchronization is not adjusted；If being less than threshold value, completes ONU registration and start normal communication.
Description
Technical field
The invention belongs to intelligent substation technical field of network security more particularly to a kind of substations based on difference detection
Adaptive network and its clock synchronous safety method.
Background technique
Intelligent substation adaptive network physical structure and EPON (Ethernet Passive Optical Network,
Ethernet passive optical network) it is identical, and the thought of Tag switching is used in core switch, realize GOOSE, SV and MMS tri-
Net unification.In order to improve network reliability, dual star topology (A, B) network architecture is established, A, B network constitute main-standby mode.Newly
The reliability of type intelligent substation adaptive network plays a significant role the stable operation of entire intelligent substation, especially when
Between synchronization system it is most important.IEEE1588 standard is that Novel intelligent substation system defines accurate clock synchronization protocol PTP,
And realize the time synchronization of substation's submicrosecond precision.But if time synchronization failure, or be destroyed, especially it is
After equipment in system is implanted Rogue program, synchronizes, will make across interval once Rogue program is performed and starts destruction clock
Protect (transformer, bus) out of service because of asynchronous sampling, or even malfunction, so as to cause substation fault.
Summary of the invention
In order to improve the safety of substation network clock, solves Novel intelligent substation communication setting network and attacked
When defense mechanism it is not perfect, cope with man-in-the-middle attack situation, the present invention provide it is a kind of based on difference detection substation it is adaptive
Answer network and its clock synchronous safety method.
Network includes: optical network unit ONU, synchronous optical line terminal OLT and EPON protocol processor；Wherein, Mei Geguang
State having the same, substation network are superfluous using active and standby link forever there are two interface for the interface module of network unit ONU
Remaining configuration mode；Each optical network unit ONU can track the clock source of synchronous optical line terminal OLT；EPON protocol processor
It is communicated by internal Multi-point Control Protocol MPCP with each optical network unit ONU.
Method includes:
Step 1, intelligent substation network EPON protocol processor timestamp is passed into each optical network unit
ONU；
Whether two interfaces that step 2, synchronous optical line terminal OLT compare optical network unit ONU are received within the regulation time difference
The message arrived, if it is not, then determining clock synchronization, there are security threats, and give a warning, and time clock synchronization is not taken to adjust；If so,
Execute step 3；
It is round-trip in the message that two interfaces that step 3, synchronous optical line terminal OLT detect optical network unit ONU receive
Time delay RTT value determines that there are security threats for clock synchronization, concurrently if two round-trip delay RTT value difference values are more than defined threshold value
It alerts out, and time clock synchronization is not taken to adjust；If two round-trip delay RTT value difference values are less than defined threshold value, complete
Optical network unit ONU is registered and starts normal pass with optical line terminal OLT.
The registration process of the optical network unit ONU includes:
Step 301, optical line terminal OLT send registration discovery frame at a time interval and are broadcast to each optical network unit
ONU, destination address is broadcast logical link indicia LLID, at the beginning of this frame includes discovery window, the big rootlet of window
It is determined according to the farthest optical network unit ONU of distance in system；
After step 302, new optical network unit ONU receive registration discovery frame, clock label field adjusts this based on the received
Then ground clock sends registration request frame, while optical network unit ONU to optical line terminal OLT within the defined windowing time
Delay measurements are carried out by Multi-point Control Protocol MPCP message；
The broadcast transmission registration control after a window receives only one registration request frame of step 303, optical line terminal OLT
Frame processed gives the optical network unit ONU, be included as in the control frame optical network unit ONU distribution logical links label L LID and
Synchronization time, while the MAC Address of logical links label L LID and optical network unit ONU being associated together；
Step 304, optical line terminal OLT then send registed authorization frame to optical network unit ONU, so as to optical line terminal
OLT dispatch optical network unit ONU uplink send time slot, Multi-point Control Protocol MPCP ranging at the same time complete, calculating it is past
Time update will be used for by optical network unit ONU by returning time delay RTT value also；
After step 305, new optical network unit ONU receive registed authorization frame, newly assigned logical links label L LID is replaced
Original logical links label L LID is changed, while sending accreditation verification frame to optical line terminal OLT；
After step 306, optical line terminal OLT receive accreditation verification frame, refresh the logic chain road sign of the optical network unit ONU
Remember LLID, completes the automatic discovery procedure of optical network unit ONU.
The protocol processor is stabbed by internal Multi-point Control Protocol MPCP message passing time.
The timestamp is the timestamp based on IEEE1588 agreement.
The beneficial effects of the present invention are:
By the analysis to EPON clock synchronization system in intelligent substation, for man-in-the-middle attack, propose a kind of new
The side ONU double-PON port difference testing mechanism takes precautions against this challenge model, carries out link delay time emulation to the model proposed
Measurement come verify increased testing mechanism alarm successfully can be provided to attack and terminate the time update.
By round trip delay time RTT, the RTT under man-in-the-middle attack state under comparison normal condition and difference inspection is added
The RTT value of survey mechanism shows that mechanism proposed by the present invention can provide alarm to internuncial attack, and in ONU side not mistuning
Whole clock strengthens the robustness of novel transformer substation network timing synchronization systems.
By round trip delay time RTT, the RTT under man-in-the-middle attack state under comparison normal condition and difference inspection is added
The RTT value of survey mechanism shows that the side ONU testing mechanism of the invention can successfully alert man-in-the-middle attack, terminates the side ONU
Time updates, and strengthens robustness and the safety of novel transformer substation network timing synchronization systems.
Detailed description of the invention
Fig. 1 is normal link RTT schematic diagram.
Fig. 2 is the RTT schematic diagram of man-in-the-middle attack.
Fig. 3 is the RTT effect picture being added after ONU difference testing mechanism.
Specific embodiment
With reference to the accompanying drawing, it elaborates to embodiment.
The present invention introduces passive optical network technique PON on the basis of intelligent substation network, sets up topological structure letter
The uplink and downlink data transmission of single, reliable double star network structure, PON uses single fiber wavelength-division multiplex technique, can largely subtract
The complexity of few substation's fiber optic network, further increases the reliability of network；Substation communication network based on PTN interchanger
In, in order to further increase substation clock network reliability, using Parallel Redundancy Protocol (PRP) mode of standard, often
There are two interface, state having the same, substation network use the redundant configuration side of active and standby network to a ONU interface module forever
Formula, when PRP operation, the highest master clock of clock source connection is connected respectively on active and standby network core interchanger, when primary
It can be seamlessly switched on standby clock device when clock plant failure, the clock sync message that master clock is sent is selected in active and standby net
Two-way is concurrent on network, active release digging soil formula；Novel intelligent substation EPON system is the system of a time synchronization, each
ONU can track the clock source of OLT.The process of the online registration of ONU is exactly the process of time synchronization.EPON protocol processor passes through
Internal MPCP (Multi-Point Control Protocol, Multi-point Control Protocol) message passes to IEEE1588 timestamp
Each ONU, ONU receive 1588 timestamp post-compensation round-trip delay RTT (Round-Trip Time), when generating the 1588 of ONU
Between stab, the timestamp is synchronous with 1588 clock sources.
The registration process of ONU of the present invention:
(1) (being traditionally arranged to be 1s) transmission registration discovery frame is broadcast to each ONU, destination address to OLT at certain intervals
For broadcast LLID, (complete zero) at the beginning of this frame includes discovery window, while determining window according to the farthest ONU of distance in system
Mouth size (general 20 kilometers are 250 microseconds).
(2) after new ONU receives registration discovery frame, clock label field adjusts local clock based on the received, is then advising
Registration request frame is sent to OLT in the fixed windowing time, while ONU receives MPCP (Multi-Point Control
Protocol, Multi-point Control Protocol) message delay measurements.
(3) for OLT after a window receives only one registration request frame, OLT broadcast transmission registration control frame is given should
ONU, is included as LLID and the synchronization time of ONU distribution in the control frame, while the MAC Address of LLID and ONU being associated in
Together.
(4) OLT then sends registed authorization frame (MPCP ranging is completed, and RTT is calculated) to ONU, and sending at this time is for ONU hair
Bandwidth authorization message is sent, so that the time slot that OLT scheduling ONU uplink is sent, then this MPCP ranging simultaneously are completed, the RTT value of calculating
Also time update will be used for by ONU.
(5) after new ONU receives registed authorization frame, newly assigned LLID is replaced to original LLID, while sending and infusing to OLT
Volume acknowledgement frame.
(6) after OLT receives accreditation verification frame, refresh the LLID of the ONU, then the entire automatic discovery procedure of ONU is just
It completes, normal communication can be started between ONU and OLT.
The present invention uses PRP Parallel Redundancy Protocol renewal time information:
There are two PON mouthfuls of transmitted in parallel data, selectivity to receive for each equipment, exists simultaneously active and standby net to increase network
Reliability.In principle, it is essentially identical (error is in tens nanoseconds) that ONU, which synchronizes 1588 timestamps to get off from double-PON port,.When
In two all normal situations of PON mouthfuls of optical links, as long as ONU arbitrarily tracks 1588 timestamp all the way.After the completion of registration
Normal condition under, ONU receives MPCP message every time can update local zone time and monitor situation of change, and OLT is received every time
MPCP message can all update and monitor the variation of RTT.The timestamp information of the OLT that ONU is carried according to MPCP message, RTT value with
And the timer of the local ONU can calculate and update 1588 time out.
Analyze man-in-the-middle attack mode:
There are intermediate equipments to obtain MPCP the message timestamp information of OLT and OLT clock section at the middle and upper levels for man-in-the-middle attack
Point essential information (IP, MAC etc.), and it is transmitted to the ONU equipment of junior, within the normal clock synchronization period, intermediate equipment intercepts and captures OLT
Time synchronization MPCP message between equipment and ONU equipment, go-between's equipment is equivalent to from clock status OLT, under
Layer ONU is equivalent to master clock state.
Man-in-the-middle attack node can be sent to the temporal information value of ONU by changing, and carry out any change and send MPCP message
To the time of ONU, and then manipulate the value of link RTT, this also mean that attacker can arbitrarily manipulate ONU node it is real-time when
Clock, the ONU clock node equipment can be made gradually to deviate the real-time clock of OLT node device can not without being found failure, failure
It is found also be switched standby clock network, it is inconsistent to be likely to result in active and standby network instruction, in turn results in clock more
New confusion.
The present invention increases difference testing mechanism in the side ONU:
Step 1: detection MPCP message receives the time difference.Each ONU equipment is parallel there are two PON mouthfuls, and comparing ONU twoport is
The no MPCP message that (settable) receives simultaneously within the regulation time difference, if main PON mouthfuls receives MPCP message and prepare to update RTT
When value calibration local zone time, do not receive what MPCP message or the message received carried for spare PON mouthfuls within the regulation time difference
1588 synchronized timestamps are inconsistent, then determining clock synchronization, there are security threats, and give a warning, and time clock synchronization is not taken to adjust.
Step 2: the RTT value in detection MPCP message.After first step detection, if ONU twoport is providing in the time difference simultaneously
The MPCP message received, increased testing mechanism then compare the RTT value in ONU double-PON port message, under normal circumstances double-PON port
The delay time of link only had for tens nanoseconds, when two RTT value difference values are more than defined threshold value (settable), determined that clock synchronization is deposited
It in security threat, and gives a warning, and time clock synchronization is not taken to adjust.
Testing mechanism of the invention is emulated:
(1) when being added without detection
1. building model to the clock synchronization of OLT and ONU, normal link RTT value such as Fig. 1 is measured under normal running status,
Shown, in figure, abscissa is time shaft, and ordinate is time delay, setting threshold value be 200 nanoseconds situation under, link when
Prolong and do not generate alarm in normal range, the side ONU carries out time update.
2. in major network all the way, there are in the state of man-in-the-middle attack, show that the clock synchronization of major network is normal nothing in OLT sidelinks
Link failure, would not also be switched to another way time system, go-between change send MPCP message to lower layer ONU when
Between and round-trip delay RTT value, and cause the clock synchronization failure of clock.As shown in Fig. 2, time delay increase to 200 more than nanosecond will not
Link failure and alarm are generated, and the side ONU carries out time update, makes system failure risk.
(2) when the side ONU testing mechanism is added
Detection the side ONU double-PON port whether within the regulation time difference simultaneously receive MPCP message, if having met, then detect
Whether the RTT difference that double-PON port respectively receives meets the detection threshold of setting.As shown in figure 3, the difference for the RTT that double-PON port receives
It is excessive, not within normal threshold value (it is assumed that being set as 100 nanoseconds), then alarming mechanism is generated, the side ONU terminates the time more
Newly.
Conclusion
By round trip delay time RTT, the RTT under man-in-the-middle attack state under comparison normal condition and difference inspection is added
The RTT value of survey mechanism shows that the side ONU testing mechanism of the invention can successfully alert man-in-the-middle attack, terminates the side ONU
Time updates, and strengthens the robustness of novel transformer substation network timing synchronization systems.
Above-described embodiment is merely preferred embodiments of the present invention, but protection scope of the present invention is not limited to
This, anyone skilled in the art in the technical scope disclosed by the present invention, the variation that can readily occur in or replaces
It changes, should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of claim
Subject to enclosing.
Claims (4)
1. a kind of time synchronization safety method of substation's adaptive network based on difference detection, the adaptive net of substation
Network includes: optical network unit ONU, synchronous optical line terminal OLT and EPON protocol processor；Wherein, each optical network unit ONU
Interface module there are two interface state having the same forever, substation network uses the redundant configuration mode of active and standby link；
Each optical network unit ONU can track the clock source of synchronous optical line terminal OLT；EPON protocol processor passes through internal multiple spot
Control protocol MPCP is communicated with each optical network unit ONU, which is characterized in that the time synchronization safety method includes:
Step 1, intelligent substation network EPON protocol processor timestamp is passed into each optical network unit ONU；
What whether two interfaces that step 2, synchronous optical line terminal OLT compare optical network unit ONU received within the regulation time difference
Message, if it is not, then determining clock synchronization, there are security threats, and give a warning, and time clock synchronization is not taken to adjust；If so, executing
Step 3；
The round-trip delay in message that two interfaces that step 3, synchronous optical line terminal OLT detect optical network unit ONU receive
RTT value determines that there are security threat, concurrent respondings for clock synchronization if two round-trip delay RTT value difference values are more than defined threshold value
It accuses, and time clock synchronization is not taken to adjust；If two round-trip delay RTT value difference values are less than defined threshold value, light net is completed
Network unit ONU is registered and starts normal communication with optical line terminal OLT.
2. method according to claim 1, which is characterized in that the registration process of the optical network unit ONU includes:
Step 301, optical line terminal OLT send registration discovery frame at a time interval and are broadcast to each optical network unit ONU,
Its destination address is broadcast logical link indicia LLID, and at the beginning of this frame includes discovery window, the size of window is according to being
Distance farthest optical network unit ONU determines in system；
After step 302, new optical network unit ONU receive registration discovery frame, when the adjustment of clock label field is local based on the received
Then clock sends registration request frame to optical line terminal OLT within the defined windowing time, while optical network unit ONU receives
The delay measurements of Multi-point Control Protocol MPCP message；
Step 303, the optical line terminal OLT broadcast transmission after a window receives only one registration request frame register control frame
The optical network unit ONU is given, is included as logical links label L LID and the synchronization of optical network unit ONU distribution in the control frame
Time, while the MAC Address of logical links label L LID and optical network unit ONU being associated together；
Step 304, optical line terminal OLT then send registed authorization frame to optical network unit ONU, so as to optical line terminal OLT
Dispatch optical network unit ONU uplink send time slot, Multi-point Control Protocol MPCP ranging at the same time complete, calculating it is round-trip when
Time update will be used for by optical network unit ONU by prolonging RTT value also；
After step 305, new optical network unit ONU receive registed authorization frame, newly assigned logical links label L LID is replaced former
The logical links label L LID come, while accreditation verification frame is sent to optical line terminal OLT；
After step 306, optical line terminal OLT receive accreditation verification frame, refresh the logical links label of the optical network unit ONU
LLID completes the automatic discovery procedure of optical network unit ONU.
3. method according to claim 1, which is characterized in that the EPON protocol processor passes through internal Multi-point Control Protocol
MPCP message passing time stamp.
4. method according to claim 1, which is characterized in that the timestamp is the timestamp based on IEEE1588 agreement.
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| CN113727218B (en) * | 2020-05-25 | 2023-03-31 | 中国电信股份有限公司 | Method for setting length of static window and related equipment |
| CN111787013B (en) * | 2020-07-03 | 2022-02-25 | 中国电子科技集团公司第三十研究所 | Attack monitoring device and method of optical fiber time synchronization system |
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| CN101888268B (en) * | 2009-05-14 | 2013-09-11 | 中兴通讯股份有限公司 | Method and device for realizing backbone optical fiber protection in Ethernet passive optical network |
| CN102006136A (en) * | 2010-12-17 | 2011-04-06 | 武汉邮电科学研究院 | Method and device for improving clock synchronization precision in EPON |
| CN102368691B (en) * | 2011-09-23 | 2014-07-02 | 烽火通信科技股份有限公司 | Optical link protection switching realizing method in Ethernet passive optical network system |
| CN202634436U (en) * | 2012-03-22 | 2012-12-26 | 绍兴电力局 | Passive optical network communication system with uplink and downlink ports possessing complete self-healing protection function |
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