CN111917461B

CN111917461B - MC-PON protection method and device based on DF election mechanism

Info

Publication number: CN111917461B
Application number: CN201910385526.9A
Authority: CN
Inventors: 张立新
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2019-05-09
Filing date: 2019-05-09
Publication date: 2021-12-10
Anticipated expiration: 2039-05-09
Also published as: CN111917461A

Abstract

The invention aims to provide a MC-PON protection method and device based on a DF election mechanism. Two or more OLTs form a redundancy group, one or more MC-PON protection groups are established on the redundancy group, and each OLT in the redundancy group extracts a DF election information unit comprising an identification of the MC-PON protection group, an IP address of an OLT system, a management state of a PON port, an operation state of the PON port and DF priority when sending or receiving an Ethernet segment route; dividing the DF election information unit into corresponding MC-PON protection groups; selecting a DF for the MC-PON protection group; and each OLT of the MC-PON protection group independently operates the DF election algorithm to obtain the DF, and then sets the PON port which belongs to the MC-PON protection group locally into an active state or a standby state according to whether the DF is self. The new MC-PON protection scheme provided by the invention does not need to run an ICCP/LDP protocol, and is compatible with a DC/NFVI network environment.

Description

MC-PON protection method and device based on DF election mechanism

Technical Field

The invention relates to the technical field of Passive Optical Networks (PONs), in particular to a MC-PON (Multi-Chassis PON) protection technology based on a DF (Designated Forwarder) election mechanism.

Background

PON systems, including various systems based on ITU-T (International Telecommunication Union, Telecommunication Standardization Sector) or IEEE (Institute of Electrical and Electronics Engineers) standards, such as GPON (Gigabit-capable Passive Optical Network), XG-PON (10-Gigabit-capable Passive Optical Network), XGs-PON (10-Gigabit-capable Symmetric Passive Optical Network), 1G or 10G EPON (Ethernet Passive Optical Network ), etc., are increasingly used as remote access networks and/or backhaul infrastructure for long-haul wireless access. Such as a remote small-Line Access Multiplexer (DSLAM), a Cable Modem Termination System (CMTS), a Long Term Evolution (LTE) small cell and/or a Wi-Fi hotspot. In these critical PON application scenarios, PON Protection (PON Protection) is an indispensable feature of the overall solution.

For the highest protection level, PON protection can be deployed on a set of redundant OLTs (Optical Line Termination) located at different physical locations, which is called MC-PON protection.

Many critical PON deployment scenarios impose requirements on MC-PON protection. Neither ITU-T nor IEEE have specified solutions for MC-PON protection.

RFC 8024 specifies a standard MC-PON protection solution, i.e., an MC-PON protection solution based on ICCP (Inter-sessions Communication Protocol, RFC 7275). The solution utilizes the ICCP protocol to synchronize the configuration and status information of MC-PON protection applications. However, ICCP is an extension based on the LDP Protocol (Label Distribution Protocol), which requires the use of LDP to transmit ICCP messages. In many deployment scenarios, LDP is undesirable. For example, many Data Centers (DC)) or Network Function Virtualization Infrastructures (NFVI) employ VXLAN (Virtual Extensible Local Area Network) as a basic Network Virtualization Overlay tunneling (Network Virtualization Overlay tunneling) technology, and LDP is generally undesirable in these DC/NFVI environments.

In addition to the standard single-active and all-active Multi-homed redundancy modes specified in RFC 7432, the draft-broadcast-less-evpn-mh-pa describes a port-active Multi-homed redundancy mode that determines the active/standby (active/standby) status of each member Link of an MC-LAG (Multi-Chassis Link Aggregation Group) bundled Link (bundle). However, the solution described by the draft-brissette-bess-evpn-mh-pa does not support the following functions:

1) the DF election result is not influenced by the management and/or operation state of each member link of the MC-LAG binding link;

2) it does not provide a convenient means for the operator to control the priority of each member link.

The draft-ietf-bess-EVPN-pref-DF describes a priority-based, result-controllable EVPN DF election scheme. It adopts the DF election mechanism described in RFC 8584, which is affected by the Attachment Circuit (AC), and takes the AC 'on/off' state as a factor of DF election algorithm.

Disclosure of Invention

The invention provides a new MC-PON protection solution, which is an extension of DF election mechanism based on Ethernet Virtual Private Network (Ethernet) Ethernet. The new MC-PON protection scheme provided by the invention does not need to run an ICCP/LDP protocol, and is compatible with a DC/NFVI network environment.

According to an aspect of the present invention, a MC-PON protection method based on a DF election mechanism is provided, wherein two or more OLTs form a redundancy group, one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group includes two or more PON ports belonging to different OLTs;

wherein, on each OLT of the redundancy group, the method comprises the steps of:

when an Ethernet segment route is sent or received, if the DF election extension group attribute of the Ethernet segment route indicates that the Ethernet segment route is used for DF election of MC-PON protection, extracting an identification of an MC-PON protection group and an IP address of an OLT system from the Ethernet segment route and extracting a management state of a PON port, an operation state of the PON port and a DF priority from the DF election extension group attribute to form a DF election information unit;

dividing the DF election information unit into corresponding MC-PON protection groups according to the identification of the MC-PON protection groups;

selecting one DF for the MC-PON protection group according to all DF election information units corresponding to the MC-PON protection group, wherein:

-if the management status of a PON port in only one DF election information element is management enabled and the operational status of the PON port is "on", the OLT corresponding to that DF election information element is selected as the DF;

-if the management status of a PON port in more than one DF election information element is management enabled and the operational status of the PON port is "on", selecting the DF according to its respective DF priority;

-if there is more than one DF election information element selected according to DF priority, continuing to select the DF according to its respective OLT system IP address;

if the DF is the local PON port, setting the PON port which belongs to the MC-PON protection group to be in an active state; and if the PON port is not the DF, setting the PON port which belongs to the MC-PON protection group to be in a standby state.

According to an aspect of the present invention, there is also provided a MC-PON protection device based on a DF election mechanism, wherein two or more OLTs form a redundancy group, one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group includes two or more PON ports belonging to different OLTs;

wherein, the MC-PON protection device is installed on each OLT of the redundancy group, and the MC-PON protection device includes:

an extracting module, configured to, whenever an OLT sends or receives an ethernet segment route, if a DF election extension group attribute of the ethernet segment route indicates that the ethernet segment route is used for DF election for MC-PON protection, extract an identifier of an MC-PON protection group and an OLT system IP address from the ethernet segment route, and extract a management state of a PON port, an operating state of the PON port, and a DF priority from the DF election extension group attribute to form a DF election information unit;

the grouping module is used for dividing the DF election information unit into corresponding MC-PON protection groups according to the identification of the MC-PON protection groups;

an election module, configured to select one DF for the MC-PON protection group according to all DF election information units corresponding to the MC-PON protection group, where:

a setting module, configured to set a PON port that belongs locally to the MC-PON protection group to an active state if the OLT belongs to the DF; and if the OLT belongs to is not the DF, setting the PON port which belongs to the MC-PON protection group to be in a standby state.

According to an aspect of the present invention, there is also provided an OLT for MC-PON protection based on a DF election mechanism, wherein two or more of the OLTs form a redundancy group, and one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group includes two or more PON ports belonging to different OLTs;

on each of the OLTs of the redundancy group, the OLT comprises a processor and a memory, the memory storing a computer program which, when executed by the processor, performs the steps of:

According to an aspect of the present invention, there is also provided a computer program product for an OLT for MC-PON protection based on DF election mechanism, wherein two or more of the OLTs form a redundancy group, and one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group includes two or more PON ports belonging to different OLTs;

when the computer program is executed by each of said OLTs of the redundancy group, the following steps are carried out:

-if the management status of a PON port in only one DF election information element is management enabled and the operational status of the PON port is "on", then the OLT corresponding to that DF election information element is selected as the DF;

According to an aspect of the present invention, there is also provided a computer-readable storage medium in which the above-mentioned computer program product according to an aspect of the present invention is stored, the computer program product being for an OLT for MC-PON protection based on a DF election mechanism.

Compared with the prior art, the invention provides an MC-PON protection solution which is expanded based on an EVPN DF election mechanism specified in RFC 8584, and does not need to operate an ICCP/LDP protocol. Wherein, in order to determine the active/standby state of the member PON ports of the MC-PON protection group, the invention takes the 'on/off' state of each member PON port as a factor in the DF election algorithm, not the 'on/off' state of the AC. That is, in the MC-PON protection scheme of the present invention, DF elections are for ethernet segments rather than EVPN instances.

Therefore, the present invention also describes a DF election algorithm for determining the active/standby status of a member PON port of an MC-PON protection group according to the management and operation status of the member PON port and a configurable DF priority without re-operating the ICCP/LDP protocol indispensable in the RFC 8024MC-PON protection solution.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings:

fig. 1 shows a system architecture diagram of an MC-PON protection scheme in a DC/NFVI environment according to an embodiment of the present invention;

fig. 2 shows a schematic diagram of an MC-PON protection scheme based on EVPN DF election;

fig. 3 shows an encoding diagram of an extended EVPN DF election extended community attribute according to one embodiment of the present invention;

fig. 4 shows a flow diagram of a method of implementing MC-PON protection according to an embodiment of the invention;

fig. 5 shows a schematic diagram of an apparatus for implementing MC-PON protection according to an embodiment of the present invention.

The same or similar reference numbers in the drawings identify the same or similar elements.

Detailed Description

Here, it should be noted that the general term PON in the present invention refers to any ITU-T or IEEE based PON technology, including but not limited to GPON, XG-PON, XGS-PON, 1G or 10G EPON, etc. The generic term PON protection includes, but is not limited to, any GPON class B or C protection, or EPON trunk (trunk) or EPON tree (tree) protection.

The present invention is described in further detail below with reference to the attached drawing figures.

Fig. 1 shows a system architecture diagram according to an embodiment of the present invention, which exemplarily shows an MC-PON protection scheme in a DC/NFVI environment. Wherein, the number of active PON links (or PON ports) at any time in each MC-PON Protection Group (MC-PON Protection Group) is not more than 1.

Referring to fig. 1, CE is Customer Edge device, ONU is Optical Network Unit, MAC-VRF is Virtual Routing and Forwarding table for Media Access Control (MAC) addresses, BGP is Border Gateway Protocol, RR is Route Reflector/Route Reflector, VNF is Virtual Network Function/Virtualized Network Function, WAN is Wide Area Network/Wide Area Network, DGW is Data Gateway/Data Center Gateway, and PE is Provider Edge device/operator Edge device.

Where the critical customer edge devices are, for example, remote DSLAMs, CMTSs, LTE mini-cells or business users, etc.

Here, it should be noted that although the traffic on the redundant OLT is shown as EVPN in fig. 1, the MC-PON protection scheme proposed in the present invention is also applicable to other types of traffic, such as EVPN Virtual Private line service (EVPN-vpws) (Virtual Private Wire service), EVPN Integrated Routing and Bridging (Integrated Routing and Bridging), Layer 3Virtual Private Network (L3 VPN), or internet traffic.

Still referring to fig. 1, OLT 1 and OLT 2 form a Redundancy Group (RG) on which one or more MC-PON protection groups can be established. One MC-PON protection group comprises two or more PON ports belonging to different OLTs. Although the protection scheme in fig. 1 is exemplified as GPON class B protection or EPON trunk protection, the solution proposed in the present invention is also applicable to GPON class C protection or EPON tree protection.

On each OLT of the RG, the data that needs to be processed for the complete service protection scheme can be divided into three parts:

(1) configuration and operational data related to upper layer services/applications of all downstream ONUs;

(2) configuration and operational data relating to the PON MAC domains of all downstream ONUs;

(3) MC-PON protects configuration and operational data specific to the application.

Although it is necessary for a complete service protection scheme to correctly process the data of the first and second parts, it is beyond the scope of the present invention to describe a solution for processing these data.

The third part of the data is specific to the MC-PON protection application and the present invention aims to handle the configuration and operational data of this part.

MC-PON protection specific configuration and operational data are as follows:

1) an operator-configurable DF priority (DF Preference) for each member PON port in the MC-PON protection group;

2) management state and operation state of each member PON port in the MC-PON protection group.

All OLTs in the RG each independently select an active PON port of the MC-PON protection group based on the configuration and operational data of these MC-PON protection applications. The selection of the active PON port will be based on an extension to the EVPN DF election mechanism. Here, selecting a PON port in the MC-PON protection group as active state is equivalent to the OLT to which the PON port belongs being selected as the DF of the MC-PON protection group, and vice versa.

To select the DF of an MC-PON protection group from a set of redundant OLTs, each OLT issues one ethernet segment Route (EVPN Route type 4), along with one ES-Import RT extended community attribute (ES-Import Route Target (RT) extended community) and one DF Election extended community attribute (DF Election extended community).

The values of Ethernet Segment Identifiers (ESI) of all the OLTs for Ethernet Segment routes issued by the same MC-PON protection group must be the same. In the invention, the Ethernet segment is synonymous with the MC-PON protection group, and the ESI is also synonymous with the identification of the MC-PON protection group.

Each OLT in the RG must install an ingress RT filter to receive ethernet segment routes issued by other OLTs in the RG. The RT value of the input RT filter is the same as the RT value of the ES-Import RT extended community attribute.

draft-ietf-less-evpn-pref-DF § 3 the DF priority field is defined in the DF election extended community attribute, which field is reused by the present invention. In addition, in order to support the management and the running state issue of the member PON port, the present invention proposes to define two new DF Election capability bits (DF Election capabilities bits) in the bitmap field of the DF Election extended community attribute.

In order to indicate that the Ethernet segment route is used for MC-PON protection application, the invention also defines a new DF Election Algorithm (DF electric Algorithm) value.

The following describes the extension of the MC-PON protection to the DF election extension community attribute and the DF election algorithm proposed by the present invention in detail.

Fig. 2 shows a schematic diagram of MC-PON protection scheme based on EVPN DF election.

RFC 8584 § 2.2 defines the EVPN DF election extended community attributes. The invention defines a new DF election algorithm value and two new DF election capability bits in the EVPN DF election extended community attribute.

The newly defined DF Election Algorithm values and DF Election capability bits may be configured locally on each involved OLT as vendor specific features or distributed by IANA (Internet Assigned Numbers Authority) in the "DF Alg (abbreviation of DF Algorithm)" and "DF Election Capabilities (DF Election Capabilities)" sub-registries of the Border Gateway Protocol (BGP) extended community attributes registry. In the context of the present invention, the new DF election algorithm value is denoted MC _ PON _ PROTECTION, and the two new DF election capability bits are denoted PA and PO, respectively. Encoding of extended EVPN DF election extended community attributes supporting new DF election algorithm values MC _ PON _ PROTECTION and new DF election capability bits PA and PO is shown in fig. 3.

Here, according to RFC 8584 and draft-ietf-less-evpn-pref-DF, DF Alg values 0,1,2 have been assigned, so the new DF election algorithm value (DF Alg value) MC _ PON _ PROTECTION should be an integer greater than 2. The new DF Alg value may be a vendor private value or an IANA assigned public value.

In fig. 3, the D bit and a bit in the bitmap field are defined in draft-ietf-less-evpn-pref-df and RFC 8584, respectively. For completeness, fig. 3 shows these two bits. The A bit is irrelevant to the MC-PON protection scheme, and the D bit is optional in the MC-PON protection scheme. Although the MC-PON protection scheme does not directly use D bits, it can provide some characteristic improvements by issuing a resilient/Non-resilient capability of the OLT.

The following continues with the discussion of the PA bits and PO bits.

The PA bit and PO bit are newly defined by the present invention: the former encodes the management state of the PON port, and the latter encodes the operation state of the PON port. They may be placed in any unallocated bit position of the bitmap field, and the positions shown in fig. 3 are exemplary only and should not be construed as any limitation of the present invention.

The values of the PA bit and PO bit and their meaning are as follows:

significance of PA value

0 PON port is managed and enabled

1 PON Port managed disabled

Meaning of PO value

0 PON port is in 'on' state

(PON Port without physical layer or MAC layer failure)

1 PON port is in 'off' state

(PON Port has physical layer or MAC layer failure)

Fig. 4 shows a flow chart of a method according to an embodiment of the present invention, which particularly shows a process of implementing MC-PON protection.

Referring to fig. 1 and 4, two or more OLTs form an RG, and one or more MC-PON protection groups are established on the RG. Each MC-PON protection group comprises two or more PON ports belonging to different OLTs. In an MC-PON protection group, no more than one PON port is active at any one time; specifically, in an MC-PON protection group, only the PON ports on the OLT selected as the DF are in an active state, and the PON ports on the OLTs other than the DF are in an inactive state.

For the DF election mechanism of the present invention, which is performed for each MC-PON PROTECTION group, when an OLT in the RG sends or receives an ethernet segment route, if the value of the DF Alg field carried by the DF election extended community attribute along with the ethernet segment route is MC _ PON _ PROTECTION, the DF election algorithm of the present invention will be performed to select DF for one MC-PON PROTECTION group. The MC-PON protection group for which DF is selected is also referred to as the DF election group when the DF election algorithm is invoked.

With continued reference to fig. 4, for each OLT in the RG, in step S1, when an OLT sends out or receives an ethernet segment route every time it indicates DF election for MC-PON protection along with the DF election extended community attribute of the ethernet segment route, the identity of the MC-PON protection group, the OLT system IP address, and the management state of the PON port, the operation state of the PON port, and the DF priority are extracted from the ethernet segment route to constitute a DF election information element. Therefore, the DF election information element includes an identification of the MC-PON protection group, an OLT system IP address, a management state of the PON port, an operation state of the PON port, and a DF priority.

When an OLT in the RG sends or receives an ethernet segment route, if the DF election algorithm value (DF Alg value) carried along with the DF election extended community attribute of the ethernet segment route is MC _ PON _ PROTECTION, the OLT must invoke the DF election algorithm for MC-PON PROTECTION described in the present invention to process the ethernet segment route.

The OLT extracts a DF election information element from each originating or received ethernet segment route and the accompanying DF election extension community attributes. Each DF election information element may be represented as a five-tuple, such as < identification of MC-PON protection group, OLT system IP address, management status of PON port, operation status of PON port, DF priority >. Since the identifier of the MC-PON protection group is represented by ESI, the management state of the PON port is represented by PA, the operation state of the PON port is represented by PO, and the DF election information element may be further represented as five-tuple < ESI, OLT system IP address, PA, PO, DF priority >.

When an MC-PON protection group (GPON class B/class C protection or EPON trunk/EPON tree protection) is configured on an RG composed of a plurality of OLTs, the same MC-PON protection group identification value must be configured on all OLTs of the MC-PON protection group. The MC-PON protection group identity is globally unique, and may be encoded in the ESI format specified in RFC 7432 § 5, for example, and published using the ESI field in ethernet segment routing (EVPN route type 4). ESI of type 0 or type 5 can be used to encode the MC-PON protection group identification.

The OLT system IP Address is extracted from the Originating Router's IP Address field of the ethernet segment route, which may be a 4-byte IPv4 Address or a 16-byte IPv6 Address. However, in a particular DF election group, all of the OLT system IP addresses of the quintuple must be all IPv4 addresses or all IPv6 addresses, but not mixed IPv4 and IPv6 addresses.

Each OLT in the RG issues an ethernet segment route along with ES-Import RT extended community attributes and DF election extended community attributes to announce its DF candidates qualifying at the DF election group identified by the ESI value.

And the OLT constructs a unique ES-Import RT extended community attribute for each MC-PON protection group and installs a corresponding input RT filter, wherein the RT value of the input RT filter is the same as that of the constructed ES-Import RT extended community attribute.

The OLT also constructs the DF election extended community attribute as shown in fig. 3, where: the DF Alg field contains an MC _ PON _ PROTECTION value, PA bit and PO bit indicate the current management state and the operation state of the OLT local PON port in the MC-PON PROTECTION group, respectively, and the DF priority field carries a DF priority value configured by the operator of the OLT local PON port in the MC-PON PROTECTION group.

Whenever the OLT receives/sends out one ethernet segment route, it will invoke DF algorithm specific procedures to handle the received/sent out ethernet segment route. The ethernet segment route is published along with the DF election extension group attribute of DF Alg ═ MC PON _ PROTECTION. The particular process having the capability to handle this ethernet segment route must be able to handle the DF election extended community attribute format as shown in fig. 3 and must support the DF election algorithm as described in the following step S3 of the present invention.

In step S2, the OLT divides the DF election information unit into corresponding MC-PON protection groups according to the identifier of the MC-PON protection group in the DF election information unit.

Since the ESI values of the ethernet segment routes sent by the same MC-PON protection group are all the same, the ESI can be used to identify the MC-PON protection group, that is, the ESI will be used as the identification of the MC-PON protection group. Thus, based on the ESI values, the OLT may partition all five tuples into each DF election group. In a particular DF election set, all quintuples have the same ESI value.

In step S3, the OLT selects a DF for the MC-PON protection group according to all DF election information units corresponding to the MC-PON protection group, where:

-if the management status of the PON port in only one DF election information element is management enabled and the operational status of the PON port is "on", the OLT corresponding to that DF election information element is selected as DF;

-selecting a DF according to its respective DF priority if the management status of a PON port in more than one of the DF election information elements is management enabled and the operational status of the PON port is "on";

-if there is more than one DF election information element selected according to DF priority, continuing to select DF according to its respective OLT system IP address.

In addition, consider the case of a DF that may not hit. For example, if the management state of the PON port of none of the DF election information elements corresponding to the MC-PON protection group is management enabled and the operation state of the PON port is "on", then there is no selected DF.

Specifically, in each DF election group, the OLT elects one DF or no DF election after running the following DF election algorithm. The DF election algorithm may be performed by three rounds of elections:

election round 1: check PA and PO values for all quintuple in a DF election set

All quintuples with PA 0 and PO 0 (i.e. PON ports are management enabled and the operational status is "on") win.

If no such quintuple exists, there is no DF in the DF electing set. This election is over.

If only one quintuple wins, this quintuple yields the DF of the DF election set.

This election is over.

If more than one quintuple wins, all winning quintuples will go to the second round of election.

Election round 2: checking the DF precedence values of all quintuple in the DF election group that won round 1 election

All quintuples with the highest DF priority values win.

This election is over.

If more than one quintuple wins, all winning quintuples will go to round 3 elections.

Election round 3: checking the value of the OLT system IP address of all quintuple winning the election round 2 in the DF election group

All quintuples with the smallest OLT system IP address value win.

Regardless of whether the number of winning quintuple is 1 orIs any other number, all winning quintuple has the same OLT system IP address value, thereby generating the unique DF for that DF election group. And finishing the election.

Wherein, in round 3 elections, multiple quintuples may have the same minimum OLT system IP address value. These five tuples come from multiple ethernet segment routes from the same OLT.

Further, depending on the operator's policy, it may be that the OLT with the lowest DF priority value wins, or that the OLT with the largest OLT system IP address value wins.

After the DF election algorithms are respectively run, all OLTs in the DF election group should independently elect the same DF, or if no PON port in the MC-PON protection group is enabled by management and the running state is "on", there is no DF.

In step S4, the OLT compares the IP address of the DF with its own IP address to determine whether or not it is the DF of the MC-PON protection group. If the OLT is the DF of the MC-PON protection group, setting the PON port which belongs to the MC-PON protection group locally to be in an active state; and if the OLT is not the DF of the MC-PON protection group, setting the PON port which locally belongs to the MC-PON protection group to be in a standby state.

Here, each OLT in the DF election group independently elects a DF, and all the elected DFs should be the same. Accordingly, each OLT compares the DF with its own IP address to determine whether it is the DF of the DF election group and sets the PON port locally belonging to the MC-PON protection group to an active state or a standby state accordingly.

On each OLT, the PON MAC domain and upper layer services/applications related to the active/standby state of the PON port should be notified of the PON protection switching event and call the appropriate routines accordingly. These routines are not within the scope of the present invention.

Whenever the management status, the operation status or the DF priority value of a PON port belonging to the MC-PON protection group on an OLT changes, the OLT must immediately issue a new ethernet segment route and ES-inport RT extended community attribute and DF election extended community attribute to trigger DF reselection. For each new ethernet segment route, which corresponds to all OLTs in the MC-PON protection group, including the OLT that sent the new ethernet segment route, the DF election algorithm of the present invention must be run again to reselect the current DF.

Fig. 5 shows a schematic diagram of an apparatus according to an embodiment of the present invention, in which an OLT 500 in the present invention is specifically shown.

Referring to fig. 1 and 5, two or more OLTs form a redundancy group, and one or more MC-PON protection groups are established on the redundancy group, where each MC-PON protection group includes two or more PON ports belonging to different OLTs.

With continued reference to fig. 5, each OLT 500 of the redundancy group is provided with an MC-PON protection device 50, and the MC-PON protection device 50 further includes an extraction module 51, a grouping module 52, an election module 53 and a setting module 54.

Specifically, when an OLT 500 sends or receives an ethernet segment route, if the DF election extension group attribute along with the ethernet segment route indicates DF election for MC-PON protection, the extracting module 51 extracts the identification of the MC-PON protection group, the OLT system IP address, and the management status of the PON port, the operating status of the PON port, and the DF priority from the ethernet segment route to form a DF election information unit. Therefore, the DF election information element includes an identification of the MC-PON protection group, an OLT system IP address, a management state of the PON port, an operation state of the PON port, and a DF priority.

When OLT 500 in RG sends or receives an ethernet segment route, if DF election algorithm value (DF Alg value) carried along with DF election extended community attribute of the ethernet segment route is MC _ PON _ PROTECTION, MC-PON PROTECTION device 50 must invoke DF election for MC-PON PROTECTION described in this invention to process the ethernet segment route.

The extraction module 51 extracts a DF election information element from each outgoing or incoming ethernet segment route and the accompanying DF election extension community attributes. Each DF election information element may be represented as a five-tuple, such as < identification of MC-PON protection group, OLT system IP address, management status of PON port, operation status of PON port, DF priority >. Since the identifier of the MC-PON protection group is represented by ESI, the management state of the PON port is represented by PA, the operation state of the PON port is represented by PO, and the DF election information element may be further represented as five-tuple < ESI, OLT system IP address, PA, PO, DF priority >.

The MC-PON protection device 50 constructs a unique ES-Import extended community attribute for each MC-PON protection group and installs a corresponding input RT filter whose RT value is the same as that of the constructed ES-Import extended community attribute.

MC-PON protection device 50 also constructs the DF election extended community attribute as shown in fig. 3, where: the DF Alg field contains an MC _ PON _ PROTECTION value, PA bit and PO bit indicate the current management state and the operation state of the OLT local PON port in the MC-PON PROTECTION group, respectively, and the DF priority field carries a DF priority value configured by the operator of the OLT local PON port in the MC-PON PROTECTION group.

Whenever OLT 500 receives/sends out an ethernet segment route, MC-PON protection device 50 will invoke DF algorithm specific procedures to handle the received/sent out ethernet segment route. The ethernet segment route is published along with the DF election extension group attribute of DF Alg ═ MC PON _ PROTECTION. The particular process with which this ethernet segment route is handled must be able to handle the DF election extended community attribute format as shown in fig. 3 and must support the DF election algorithm as described below in the present invention.

The grouping module 52 divides the DF election information unit into corresponding MC-PON protection groups according to the identity of the MC-PON protection group in the DF election information unit.

Since the ESI values of the ethernet segment routes sent by the same MC-PON protection group are all the same, the ESI can be used to identify the MC-PON protection group, that is, the ESI will be used as the identification of the MC-PON protection group. Thus, based on the ESI values, grouping module 52 may partition all five-tuples into DF elections. In a particular DF election set, all quintuples have the same ESI value.

The election device 53 selects one DF for the MC-PON protection group according to all DF election information units corresponding to the MC-PON protection group, where:

Specifically, in each DF election group, election module 53 elects one DF or no DF election after running the following DF election algorithm. The DF election algorithm may be performed by three rounds of elections:

election round 1: check PA and PO values for all quintuple in a DF election set

If only one quintuple wins, this quintuple yields the DF of the DF election set. This election is over.

All quintuples with the highest DF priority values win.

All quintuples with the smallest OLT system IP address value win.

Regardless of whether the number of winning quintuple is 1 or any other number, all winning quintuples have the same OLT system IP address value, resulting in a unique DF for the DF election set. And finishing the election.

The setting module 54 compares the IP address of the DF with the IP address of the OLT to determine whether the OLT is the DF of the MC-PON protection group: if the OLT is the DF of the MC-PON protection group, setting the PON port which belongs to the MC-PON protection group locally to be in an active state; and if the OLT is not the DF of the MC-PON protection group, setting the PON port which locally belongs to the MC-PON protection group to be in a standby state.

Here, each OLT in the DF election group independently elects a DF, and all the elected DFs should be the same. Accordingly, each OLT compares the DF with its own IP address to determine whether it is the DF of the DF election group itself, and sets the PON port locally belonging to the MC-PON protection group to an active state or a standby state accordingly.

Whenever the management status, the operation status, or the DF priority value of a PON port of an OLT that belongs to the MC-PON protection group locally changes, the MC-PON protection device 50 of the OLT must issue a new ethernet segment route and the ES-Import RT extended community attribute and the DF election extended community attribute to trigger DF reselection. For each new ethernet segment route, which corresponds to all OLTs in the MC-PON protection group, including the OLT that sent the new ethernet segment route, the DF election algorithm of the present invention must be run again to reselect the current DF.

It should be noted that the present invention may be implemented in software and/or in a combination of software and hardware, for example, as an Application Specific Integrated Circuit (ASIC), a general purpose computer or any other similar hardware device. In one embodiment, the software program of the present invention may be executed by a processor to implement the steps or functions described above. Also, the software programs (including associated data structures) of the present invention can be stored in a computer readable recording medium, such as RAM memory, magnetic or optical drive or diskette and the like. Further, some of the steps or functions of the present invention may be implemented in hardware, for example, as circuitry that cooperates with the processor to perform various steps or functions.

In addition, some of the present invention can be applied as a computer program product, such as computer program instructions, which when executed by a computer, can invoke or provide the method and/or technical solution according to the present invention through the operation of the computer. Program instructions which invoke the methods of the present invention may be stored on a fixed or removable recording medium and/or transmitted via a data stream on a broadcast or other signal-bearing medium and/or stored within a working memory of a computer device operating in accordance with the program instructions. An embodiment according to the invention herein comprises an apparatus comprising a memory for storing computer program instructions and a processor for executing the program instructions, wherein the computer program instructions, when executed by the processor, trigger the apparatus to perform a method and/or solution according to embodiments of the invention as described above.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural. A plurality of units or means recited in the system claims may also be implemented by one unit or means in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.

Claims

1. A multi-chassis passive optical network (MC-PON) protection method based on a Designated Forwarder (DF) election mechanism is disclosed, wherein two or more Optical Line Terminals (OLT) form a redundancy group, one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group comprises two or more PON ports which belong to different OLTs;

2. The method of claim 1, wherein if the management status of a PON port in none of the DF election information elements is management-enabled and the operational status of the PON port is "on", then there is no DF elected.

3. The method of claim 1, wherein the OLT system IP address in each DF election information element corresponding to one MC-PON protection group is an IPv4 address or an IPv6 address.

4. The method of claim 1, wherein said DF election information element is expressed in one five-tuple < MC-PON protection group identification, OLT system IP address, PON port management status, PON port operation status, DF priority >.

5. The method of claim 1, wherein Ethernet Segment Identifiers (ESI) values for ethernet segment routes issued for the same MC-PON protection group are the same.

6. The method of claim 1, wherein the ethernet segment routes issued by other OLTs in the redundancy group are received through an ingress Route Target (RT) filter having the same RT value as that of an ethernet segment-ingress (ES-Import) RT extended community attribute.

7. The method of any of claims 1 to 6, wherein the DF election extended community attribute carries a specific DF election algorithm value to indicate the DF election of the Ethernet segment route for MC-PON protection.

8. A MC-PON protection device based on DF election mechanism, wherein two or more OLTs form a redundancy group, one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group comprises two or more PON ports belonging to different OLTs;

9. A MC-PON protection device according to claim 8, wherein if the management status of a PON port in none of the DF election information elements is management enabled and the operational status of the PON port is "on", then there is no DF elected.

10. An MC-PON protection device according to claim 8, wherein the DF election information element is represented by a five-tuple < MC-PON protection group identity, OLT system IP address, PON port management status, PON port operation status, DF priority >.

11. An MC-PON protection device according to any one of claims 8 to 10, wherein the DF election extended community attribute carries a specific DF election algorithm value to indicate DF elections for MC-PON protection by the ethernet segment routing.

12. An OLT for MC-PON protection based on DF election mechanism, wherein two or more OLTs form a redundancy group, one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group comprises two or more PON ports belonging to different OLTs;

13. A computer-readable storage medium in which a computer program is stored, when the computer program is executed by an OLT for MC-PON protection based on a DF election mechanism, wherein two or more of the OLTs form a redundancy group, and one or more MC-PON protection groups are established on the redundancy group, and each MC-PON protection group includes two or more PON ports belonging to different OLTs;

at each of the OLTs of the redundancy group, the following operations are performed: