JP2015012573A - Optical network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an ONU subordinate to an OLT to access the OLT even when the OLT is faulty in an optical network system.SOLUTION: An optical network system 1 comprises: a plurality of OLTs (Optical Line Terminals) 3a-3c connected with an optical switching network 4; and a plurality of edge routers 2a-2c that are provided on the Internet 9, make any of the plurality of OLTs 3a-3c subordinate to themselves, and are communicatively connected with the OLT 3. If the edge router 2 detects a fault of its subordinate OLT 3, it encapsulates an IP (Internet Protocol) packet received from the Internet 9 and transmits it to another edge router 2, a rescue node.

Description

  The present invention relates to an optical network system for accessing a backbone network on a station side from a terminal on a subscriber side.

  A PON (Passive Optical Network) system that performs point-to-multipoint communication using an optical fiber transmission line is known as one of access systems that connect a backbone network and a subscriber-side terminal.

FIG. 7 is a diagram illustrating a configuration of an optical network system 1C of a comparative example.
This optical network system 1C is the PON system described above, and a plurality of ONUs (Optical Network Units) 5p, 5q, 5r are connected to an OLT (Optical Line Terminal) 3a via an optical fiber transmission line and an optical coupler 7. It is connected. Further, a plurality of ONUs 5s, 5t, and 5u are connected to the OLT 3b through the optical fiber transmission line and the optical coupler 7. The optical coupler 7 is an optical passive element, and branches one optical fiber.
The ONUs 5p to 5u are optical line terminators installed on the subscriber side, and are connected to a subscriber side terminal (not shown) to convert between optical signals and electrical signals, and multiplex / separate optical signals. Is to do.

The OLTs 3a and 3b are optical terminators installed on the telephone station side (operator side), and are connected to the Internet 9 via a backbone network to convert between optical signals and electrical signals, Multiplexing / separation is performed.
Conventionally, in the optical network system 1C, one OLT 3 provided on the telephone office side supports a maximum of 32 ONUs 5. Since the OLT 3 is a facility in the telephone office and has a low failure probability, the OLT 3 is not multiplexed. For example, when the OLT 3b fails, the ONUs 5s, 5t, and 5u under the control of the OLT 3 are generally not usable until the repair of the OLT 3b is completed.

  In contrast to a passive access network such as the optical network system 1C of the comparative example, Non-Patent Document 1 discloses an optical access network using an active optical switch.

Kazumasa Tokuhashi et al. “A Study on Optical Access Network Using Active Optical Switch”, IEICE Technical Report, IEICE Technical Report, August 1, 2008, 108, 183 (PN2008 14 -24), 49-53

  However, in the event of a facility failure due to a large-scale disaster, the backbone network can continue communication using a plurality of detour routes, but the above-described optical network system is weaker than the backbone network. In other words, in the above-described optical network system, there is a possibility that the multiplexed OLTs may fail simultaneously due to a disaster and cannot be accessed by the subordinate ONUs. Furthermore, there is a possibility that the telephone office building will be damaged by this disaster, making it impossible for the ONU to access it, and there is a possibility that the service for the subscriber will be interrupted for a long period of time.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an optical network system capable of being accessed by an ONU under its control even when an OLT fails.

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided on the Internet and a plurality of OLTs connected to the optical switch network, and can communicate with the OLT under one of the plurality of OLTs. An optical network system comprising a plurality of edge routers connected to the network.

  In this way, according to the present invention, even when the OLT fails, access by the ONU under its control is possible via another edge router that is a relief node.

  According to a second aspect of the present invention, when the edge router detects a failure of a subordinate OLT, the edge router encapsulates an IP packet received from the Internet and transmits the packet to another edge router that is a rescue node. The optical network system according to claim 1 is characterized.

  In this way, according to the present invention, it is possible to encapsulate an IP packet and send it to another edge router that is a rescue node when the OLT fails.

  According to a third aspect of the present invention, when the edge router receives the IP packet encapsulated from the Internet, the edge router transmits the IP packet to the subordinate OLT after decapsulating the IP packet. The optical network system according to claim 2.

  In this way, according to the present invention, the edge router can construct an IP tunnel with another edge router that is a rescue node, and can transmit the original IP packet by detouring.

  In the invention according to claim 4, each OLT realizes one or a plurality of virtual OLTs, and each edge router realizes a virtual router under one of the virtual OLTs, If the virtual router detects a failure of the OLT that realizes a subordinate virtual OLT, the virtual router moves the virtual OLT realized by the OLT to be realized on another OLT, and 2. The optical network system according to claim 1, wherein the connection of the switch network is changed.

  In this way, according to the present invention, the time for transferring the IP packet via the IP tunnel can be omitted, so that the ONU under the control of the failed OLT can access the Internet without overhead.

  According to a fifth aspect of the present invention, the control unit that controls the optical switch network, the plurality of OLTs, and the plurality of edge routers in a centralized manner, and configuration information that relieves a failure of any of the OLTs are stored. The optical network system according to claim 1, further comprising: a network controller including a storage unit configured to perform storage.

  Thus, according to the present invention, the network controller controls the data transfer function of each layer of the optical network system in an integrated manner. As a result, the network controller can quickly recover the optical network system from the failure by minimizing the control delay.

  According to the present invention, even when the OLT is out of order, access by the ONU under its control becomes possible.

1 is a schematic configuration diagram showing an optical network system in a first embodiment. It is a figure which shows the operation | movement at the time of failure occurrence of the optical network system in 1st Embodiment. It is a sequence diagram at the time of normal and failure in the first embodiment. It is a schematic block diagram which shows the optical network system in 2nd Embodiment. It is a figure which shows the time of failure occurrence of the optical network system in 2nd Embodiment. It is a schematic block diagram which shows the optical network system in 3rd Embodiment. It is a schematic block diagram which shows the optical network system of a comparative example.

Next, modes for carrying out the present invention (referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate.
(First embodiment)
FIG. 1 is a schematic configuration diagram showing an optical network system 1 in the first embodiment.
The optical network system 1 includes a plurality of edge routers 2a to 2c, a plurality of OLTs 3a to 3c, an optical switch network 4, and a plurality of ONUs 5p to 5u. Here, since each edge router 2a-2c and each OLT3a-3c are similarly connected and operate | moved similarly, the structure and operation | movement of edge router 2c and OLT3c are demonstrated as a representative.
The edge router 2c is provided on the Internet 9, is connected to a trunk network (not shown), and can communicate with, for example, the external node 8. The edge router 2c is connected to the subordinate OLT 3c so as to be communicable.
The OLT 3c is installed on the telephone office side, is connected to the edge router 2c by an electric cable, and is connected to the ONUs 5p to 5u on the subscriber side via the optical switch network 4.

  The OLT 3 of the comparative example and the ONU 5 were connected point-to-multipoint via the optical coupler 7. However, the optical switch network 4 that connects between the OLT 3 and the ONU 5 of the first embodiment is an optical switch of an N × M complete line group. Here, the N × M complete line group means that N inputs / outputs and M inputs / outputs can be arbitrarily connected. For example, when N OLTs 3 and M ONUs 5 are connected, the optical switch network 4 can communicate by arbitrarily connecting the OLTs 3 and the ONUs 5. As a result, even if one of the OLTs 3 breaks down, it is possible to bypass the failure by communicating with another OLT 3 as a rescue node, so that access by each ONU 5 can be continued.

  If the external node 8 transmits an IP (Internet Protocol) packet to a subscriber terminal (not shown) connected to the ONU 5, the IP packet is received by the edge router 2c and transferred to the OLT 3c. The OLT 3c transmits an IP packet to the ONU 5u via the optical switch network 4. Thereby, the ONU 5u can receive the IP packet from the external node 8.

FIG. 2 is a diagram illustrating an operation when a failure occurs in the optical network system 1 in the first embodiment. The numbers with parentheses indicate the operation order. The same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
(1) The external node 8 transmits an IP packet to a subscriber terminal (not shown) connected to the ONU 5. This IP packet is received by the edge router 2c.

  (2) Since a failure has occurred in the OLT 3c, the edge router 2c encapsulates the IP packet received from the external node 8, sets the destination address in the edge router 2a, and sets the encapsulated IP packet in the edge router 2a. Forward to. Here, the edge router 2a is a rescue node of the edge router 2c. A storage node (not shown) of the edge router 2c stores in advance a relief node when the subordinate OLT 3c fails.

(3) When receiving the encapsulated IP packet, the edge router 2a restores the original IP packet by decapsulation and transfers it to the subordinate OLT 3a. As a result, an IP tunnel is established between the edge router 2c and the edge router 2a. The original IP packet can be detoured and transmitted via this IP tunnel.
(4) The OLT 3a converts the IP packet from an electric signal to an optical signal and transfers it to the ONU 5u via the optical switch network 4. When the OLT 3c fails, the optical switch network 4 connects the OLT 3a, which is a predetermined relief node, and the ONU 5u.
As a result, even if the OLT 3c fails, access by the ONU 5u becomes possible by repairing another OLT 3a.

FIG. 3 is a sequence diagram at the time of normality and failure in the first embodiment.
Sequences Q10 to Q12 show normal operation. When the external node 8 generates an IP packet and sets the address of a subscriber terminal (not shown) connected to the ONU 5u as the destination address of the header of the IP packet, the communication sequence starts.
In sequence Q10, the external node 8 transmits this IP packet. The transmitted IP packet is received by the edge router 2c.
In sequence Q11, the edge router 2c transfers this IP packet to the subordinate OLT 3c.
In the sequence Q12, the OLT 3c converts this IP packet from an electric signal to an optical signal and transfers it to the ONU 5u via the optical switch network 4. Thereby, the ONU 5u can receive the IP packet from the external node 8.

Sequences Q20 to Q21 show the operation when a failure occurs.
In the sequence Q20, the OLT 3c detects that a failure has occurred in itself.
In sequence Q21, the OLT 3c notifies the upper edge router 2c that a failure has occurred in itself. Thereby, the edge router 2c can detect that a failure has occurred in the OLT 3c.
The edge router 2c may detect a failure of the OLT 3c by periodically monitoring the state of the OLT 3c.

Sequences Q30 to Q35 show operations at the time of failure. When the external node 8 generates an IP packet and sets the address of a subscriber terminal (not shown) connected to the ONU 5u as the destination address of the header of the IP packet, the communication sequence starts.
In sequence Q30, the external node 8 transmits this IP packet. The transmitted IP packet is received by the edge router 2c.
In sequence Q31, the edge router 2c encapsulates the IP packet and sets the address of the edge router 2a as the destination address.
In sequence Q32, the edge router 2c transfers the encapsulated IP packet to the edge router 2a.
In sequence Q33, the edge router 2a decapsulates the encapsulated IP packet and takes out the original IP packet.
In sequence Q34, the edge router 2a transfers this IP packet to the subordinate OLT 3a.
In sequence Q35, the OLT 3a converts the IP packet from an electric signal to an optical signal and transfers it to the ONU 5u via the optical switch network 4. As a result, the ONU 5u can receive the IP packet from the external node 8 despite the failure of the OLT 3c.

(Effects of the first embodiment)
The first embodiment described above has the following effects (A) and (B).

(A) All the other OLTs 3 connected to the optical switch network 4 and the edge router 2 under the control of those OLTs 3 can be the relief nodes. Therefore, even when two or more OLTs 3 fail simultaneously due to triple or more multiplexing, access by the ONU 5 becomes possible.

(B) By connecting the OLT 3 accommodated in a different telephone station to the optical switch network 4, even if the OLT 3 of a certain telephone station breaks down due to a large-scale disaster, other telephones The OLT 3 accommodated in the station and connected to the optical switch network 4 can be relieved and the access by the ONU 5 can be continued.

(Second Embodiment)
Recent technology trends include node device virtualization and processing device virtualization technology. A router virtualized on a physical router is called a virtual router. Even if there is one physical router, a plurality of virtual routers with virtually different IP addresses can be realized and used as a plurality of routers. A server virtualized on a physical server is called a virtual server. Similarly, even if there is only one physical server, a plurality of virtual servers with virtually different IP addresses are realized, It can be used as a server.
In the second embodiment, the virtual router 21 is virtualized on the edge router 2 and realized. Furthermore, even if there is one OLT 3, a plurality of virtual OLTs 31 having virtually different IP addresses are realized.

FIG. 4 is a schematic configuration diagram showing an optical network system 1A in the second embodiment.
The optical network system 1A includes a plurality of edge routers 2a to 2c, a plurality of OLTs 3a to 3c, an optical switch network 4, and a plurality of ONUs 5p to 5u. Here, since each edge router 2a-2c and each OLT3a-3c are similarly connected and operate | moved similarly, the structure and operation | movement of edge router 2c and OLT3c are demonstrated as a representative.
The edge router 2c is connected to the Internet 9 via a trunk network (not shown) and can communicate with the external node 8, for example. The edge router 2c is connected to the subordinate OLT 3c. The edge router 2c further realizes a virtual router 21c having virtually different IP addresses. The virtual router 21 c can move freely on the physical edge router 2 in the Internet 9.
The OLT 3c is installed on the telephone office side, is connected to the edge router 2c by an electric cable, and is connected to the ONUs 5p to 5u on the subscriber side via the optical switch network 4. The OLT 3c realizes a virtual OLT 31c having virtually different IP addresses. The virtual OLT 31c can move freely on another physical OLT 3.

  In the second embodiment, if the external node 8 transmits an IP packet to a subscriber terminal (not shown) connected to the ONU 5, the IP packet is transmitted to the virtual router 21c realized by the edge router 2c. And transferred to the virtual OLT 31c. The virtual OLT 31c transmits an IP packet to the ONU 5u via the optical switch network 4. Thereby, the ONU 5u can receive the IP packet from the external node 8.

FIG. 5 is a diagram illustrating a time when a failure occurs in the optical network system 1A according to the second embodiment.
As shown in FIG. 5, a failure has occurred in the OLT 3c. If the virtual router 21c detects a failure of the OLT 3c, the virtual router 21c moves to the physical edge router 2a, and further moves the virtual OLT 31c to the physical OLT 3a subordinate to the edge router 2a.
Since the address information given to the virtual router 21c is the same as that shown in FIG. 4, the IP packet transmitted by the external node 8 is automatically transferred to the virtual router 21c.
As in the first embodiment, the optical switch network 4 transfers an IP packet from the physical OLT 3a to the ONU 5u. As a result, the ONU 5u can access the Internet 9 without being interrupted.

(Effect of 2nd Embodiment)
The second embodiment described above has the following effects (C) and (D).

(C) Even if the physical OLT 3 fails, each ONU 5 can continue communication smoothly without going through the IP tunnel, and can access the Internet 9 without overhead.

(D) In the optical network system 1A according to the second embodiment, even when the physical edge router 2c fails, the virtual router 21c is moved to the other edge routers 2a and 2b, so that the ONU 5u Can continue communication smoothly.

(Third embodiment)
FIG. 6 is a schematic configuration diagram showing an optical network system 1B in the third embodiment. The same elements as those in the optical network system 1A according to the second embodiment shown in FIG.
In the third embodiment, all of the edge routers 2a to 2c, the OLTs 3a to 3c, and the optical switch network 4 are realized by SDN (Software Defined Network).
The optical network system 1B of the third embodiment has the same configuration as that of the optical network system 1A of the second embodiment, and is described as an SDN-network controller 6 (in FIG. 6, “SDN-NW controller”). SDN router controller 63, SDN-OLT controller 64, and SDN optical switch controller 65.

  Each switch body (not shown) constituting the optical switch network 4 has a simple data transfer function, and the SDN optical switch controller 65 controls the data transfer path and conditions.

In the OLT 3 hierarchy, the physical OLTs 3a to 3c have a simple data transfer function, and the SDN-OLT controller 64 operates virtual OLTs 31a to 31c on the OLTs 3a to 3c to transfer data. Control the route and conditions of
In the layer of the edge router 2, the physical edge routers 2a to 2c have a simple IP packet transfer function, and the SDN router controller 63 has virtual routers 21a to 21c on the edge routers 2a to 2c. To control the data transfer route and conditions.

The SDN-network controller 6 controls the SDN router controller 63, the SDN-OLT controller 64, and the SDN optical switch controller 65 in cooperation with each other.
The SDN-network controller 6 includes a control unit 61 and a storage unit 62. The storage unit 62 stores network configuration information 621-1 to 621-3 corresponding to an assumed failure.

  When the control unit 61 receives a failure signal of any OLT 3, the control unit 61 operates the virtual OLT 31 realized by the failed OLT 3 in the OLT 3 that is the repair node, and sets the failed OLT 3 in the edge router 2 that is the repair node. The virtual router 21 under control is operated, the optical switch network 4 is further controlled, and failover for automatically selecting another route is performed.

(Effect of the third embodiment)
The third embodiment described above has the following effect (E).

(E) The SDN-network controller 6 controls the data transfer function of each layer of the optical network system 1B in an integrated manner. As a result, the SDN-network controller 6 can quickly recover the optical network system 1B from the failure by minimizing the control delay.

(Modification)
The present invention is not limited to the above-described embodiment, and can be modified without departing from the spirit of the present invention. For example, there are the following (a) to (e).

(A) In 2nd Embodiment, operation | movement when physical OLT3c fails is shown. However, the present invention is not limited to this. For example, when the physical edge router 2c fails, the virtual OLT 31c moves to the other physical OLT 3, and the virtual router realized on the failed edge router 2c. 21c may be moved to another physical edge router 2. Thereby, even if the failure of the edge router 2 occurs, the ONU 5u can access the Internet 9 without being disconnected.

(B) In the second embodiment, virtual routers 21 are realized on all edge routers 2. However, the present invention is not limited to this. When a failure of any OLT 3 is detected, the operation of the edge router 2 under the control of the OLT 3 is stopped, and the virtual router having the same attribute information as the edge router 2 that has stopped the operation is stopped. The router 21 may be realized on another edge router 2. As a result, it is possible to operate without overhead due to virtualization during normal times, and communication can be continued by the virtual router 21 when failure is detected.

(C) In the second embodiment, the virtual OLT 31 is realized on all the OLTs 3. However, the present invention is not limited to this. When a failure of any OLT 3 is detected, the operation of the OLT 3 is stopped, and a virtual OLT 31 having the same attribute information as the OLT 3 that stopped the operation is realized on the other OLT 3 May be. As a result, it is possible to operate without overhead due to virtualization during normal times, and communication can be continued by the virtual OLT 31 when failure is detected.

(D) In the first and second embodiments, the optical switch network 4 is an N × M complete line group switch. However, the present invention is not limited to this, and the optical switch network 4 only needs to be connectable between each ONU 5 and at least two OLTs 3 even if they are incomplete line group switches. Thus, even when the OLT 3 communicating with the ONU 5 fails, the communication can be continued by bypassing the failed OLT 3 by switching to another connectable OLT 3 for communication.

(E) In the third embodiment, an optical network system 1C in which the SDN-network controller 6 controls the optical network system 1A in the second embodiment in an integrated manner is disclosed. However, the present invention is not limited to this, and the optical network system 1 similar to that of the first embodiment may be configured so that the SDN-network controller 6 performs overall control.

1, 1A, 1B, 1C Optical network system 2, 2a-2c Edge router 21, 21a-21c Virtual router (virtual edge router)
3,3a-3c OLT
31, 31a-31c Virtual OLT
4 Optical switch network 5, 5p-5u ONU
6 SDN-Network Controller (Network Controller)
61 Control Unit 62 Storage Unit 621-1 to 621-3 Configuration Information 63 SDN Router Controller 64 SDN-OLT Controller 65 SDN Optical Switch Controller 7 Optical Coupler 8 External Node 9 Internet

Claims (5)

Multiple OLTs (Optical Line Terminals) connected to the optical switch network,
A plurality of edge routers provided on the Internet and connected to the OLT so as to be communicable with one of the plurality of OLTs;
An optical network system characterized by comprising: If the edge router detects a failure of the subordinate OLT, it encapsulates the IP packet received from the Internet and sends it to another edge router that is a rescue node.
The optical network system according to claim 1. When the edge router receives the IP packet encapsulated from the Internet, the edge router decapsulates the IP packet and then transmits it to the subordinate OLT.
The optical network system according to claim 2. Each OLT implements one or more virtual OLTs,
Each of the edge routers realizes a virtual router under one of the virtual OLTs,
If the virtual router detects a failure of the OLT that realizes a subordinate virtual OLT, the virtual router moves the virtual OLT realized by the OLT to be realized on another OLT, and Change the switch network connection,
The optical network system according to claim 1. A control unit that collectively controls the optical switch network, the plurality of OLTs, and the plurality of edge routers;
A storage unit for storing configuration information for relieving any of the OLT failures;
A network controller comprising:
The optical network system according to claim 1.

Images