Patent Description:
Embodiments of the invention relate to, but are not limited to, the field of a multicast network, and more specifically relate to a method of establishing a bidirectional forwarding detection (BFD) session based on bit index explicit replication (BIER), and a bit-forwarding ingress router (BFIR), a bit-forwarding egress router (BFER), a system and a storage medium.

An Internet Protocol (IP) multicast technology implements efficient point-to-multi-point data transmission in an IP network, which can effectively save a bandwidth of the network and reduce a load of the network. Therefore, the IP multicast technology is widely used in real-time data transmission, multimedia conference, data copy, IP Television (IPTV), games and simulation, etc. The multicast technology is generally implemented by using a Protocol Independent Multicast (PIM) protocol (including a Protocol Independent Multicast-Sparse Mode (PIM-SM), a Protocol Independent Multicast-Dense Mode (PIM-DM)) and a Multicast Source Discovery Protocol (MSDP), etc. A common feature of these multicast protocols is to construct a control plane multicast tree, which is used for logically transforming a network plane into a tree, so as to realize point-to-multi-point data forwarding and loop avoidance of multicast forwarding. Intermediate nodes of these multicast routing protocols, which take construction of multicast distribution tree as a core, are required to maintain states of complex multicast forwarding information. With an increasing scale of the network and an increasing traffic of multicast data, this multicast technology is faced with more and more challenges in costs, operation and maintenance. Therefore, a new technology called BIER (bit indexed explicit replication) technology is proposed for constructing a multicast forwarding path.

During packet forwarding, a service may be interrupted due to a device fault. To ensure normal forwarding of a BIER packet, reduce an impact of the device fault on the service, and improve availability of a network, a bit-forwarding router (BFR) node in a BIER network must be able to detect a communication fault with the device as soon as possible, so that measures can be taken in time to ensure that the service can be continued. A BFD mechanism provides a unified detection mechanism for the entire network. It can be used for detecting a fault between two forwarding points. This mechanism enables fast link detection and ensures continuity of the service.

Therefore, for the BIER network, it is necessary to provide a scheme that can realize the <NPL> disclosed that Bit Index Explicit Replication ( BIER ) is an architecture that specifies a solution for the forwarding of multicast data packets. In some scenarios, the resilience should be provided to guarantee the multicast data is protected by a given backup resource and forwarded successfully to the receivers in BIER-specific network. <NPL> disclosed extensions to the Bidirectional Forwarding Detection (BFD) protocol for its use in multipoint and multicast networks. <NPL> disclosed active tail extensions to and updates the Bidirectional Forwarding Detection (BFD) protocol for multipoint networks. <NPL> disclosed ISIS extensions to support multicast forwarding using the Bit Index Explicit Replication (BIER) architecture. <NPL> disclosed that a type-length-value (ILV) for use in the ISIS routing protocol that allows for the proper use of the Bidirectional Forwarding Detection (BFD) protocol. There exist certain scenarios in which ISIS will not react appropriately to a BFD-detected forwarding plane failure without use of either this TLV or some other method.

The invention is defined by the independent claims; the dependent claims define particular embodiments of the invention. The method of establishing a bidirectional forwarding detection (BFD) session based on bit index explicit replication (BIER), and a bit-forwarding ingress router (BFIR), a bit-forwarding egress router (BFER), a system and a storage medium are set out in the appended set of claims.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments of the present application and features therein may be combined with each other in any manner.

Steps shown in the flowcharts of the accompanying drawings may be executed in a computer system that executes computer-executable instructions. In addition, although logical sequences are shown in the flowcharts, in some cases, the steps shown or described may be performed in a sequence other than the sequences shown herein.

A BIER technology proposes a new multicast technology architecture that does not require construction of multicast distribution tree, as shown in <FIG>. A router that supports the BIER technology is called a BFR, and a multicast forwarding domain composed of BFRs is called a BIER domain. At an edge of the BIER domain, a device that implements BFIR encapsulation of multicast data of a user is called a BFIR, and an edge BFR device that decapsulates a BIER data packet is called a BFER. After being BFIR encapsulated, the multicast data enters the BIER domain, and is forwarded in the BIER domain depending on a header of the BIER. In the BIER domain, each edge BFER is assigned a globally unique bit position, information of each BFER is flooded in the BIER domain by using an IGP, and all bit positions constitute a bit string. Transmission and routing of the data packet in the BIER domain depend on the bit string. After receiving a packet header containing the BIER, the BFR forwards the packet according to the bit string carried in the BIER packet header.

According to a BFD standard definition of RFC5880, a BFD session will be established between two detection points before link detection. Due to the BIER technology being used in a multicast service, a bidirectional detection method of point to multiple-point (P2MP) is needed. Although relevant proposals of the Internet Engineering Task Force (IETF) disclose a BFD related scheme of P2MP in a multicast scenario, they do not involve realizing BFD of the BIER in a control plane.

The embodiments of the present invention provide a method of establishing a BFD session based on BIER, as shown in <FIG>, and the method includes the followings.

In step <NUM>, a BFD session is established by a BFIR.

In step <NUM>, BFD information is advertised to a BFER group by the BFIR based on an IGP.

In step <NUM>, a BFD control packet is transmitted to a BFER by the BFIR, to trigger the BFER to establish the BFD session corresponding to the BFIR.

The BFD information includes: a globally unique discriminator assigned by the BFIR to a multi-point path, and a BIER forwarding table identifier (BIFT-id) and a bit string to which the BFER group belongs.

The BFER group is one or more BFER nodes corresponding to the BIFT-id and the bit string in the BFD information.

The IGP includes one of an Intermediate System to Intermediate System (ISIS) protocol, and an Open Shortest Path First (OSPF) protocol.

When the IGP is the ISIS protocol, the BFIR advertising the BFD information based on the IGP includes: the BFD information is carried by the BFIR in an advertised message based on the ISIS protocol.

The advertised message is an Intermediate System to Intermediate System Hello (ISIS Hello) message, the ISIS Hello message carries a BIER BFD sub-TLV, and the BIER BFD sub-TLV carries the BFD information.

When the IGP is the OSPF protocol, the BFIR advertising the BFD information based on the IGP includes: the BFD information is carried by the BFIR in the advertised message based on the OSPF protocol.

The advertised message is an Open Shortest Path First Hello (OSPF Hello) message, the OSPF Hello message carries the BIER BFD sub-TLV, and the BIER BFD sub-TLV carries the BFD information.

The BIER BFD sub-TLV includes: a Discriminator field, used for representing the globally unique discriminator assigned by the BFIR to the multi-point path; a BIFT-id field, used for representing the BIFT-id to which the BFER group belongs; and a BitString field, used for representing the bit string formed by bit positions of the BFER group.

The BFD control packet carries node information of the BFIR and the globally unique discriminator assigned by the BFIR to the multi-point path.

As shown in <FIG>, the embodiments of the present invention provide another method of establishing a BFD session based on BIER, and including the followings.

In step <NUM>, BFD information advertised by a BFIR based on an IGP is received and stored by a BFER.

In step <NUM>, a BFD session corresponding to the BFIR is established by the BFER according to a BFD control packet and the BFD information, after the BFD control packet transmitted by the BFIR is received by the BFIR.

The BFD information includes a globally unique discriminator assigned by the BFIR to a multi-point path, and a BIFT-id and a bit string to which a BFER group belongs.

Storing the BFD information includes: when the BFER determines that itself is a BFER node corresponding to the BIFT-id and the bit string in the BFD information, the BFD information is stored by the BFER.

The IGP includes one of an ISIS protocol, and an OSPF protocol.

When the IGP is the ISIS protocol, the BFER receiving the BFD information advertised by the BFIR based on the IGP includes: the BFD information carried by the BFIR in a advertised message based on the ISIS protocol is received by the BFER.

The advertised message is an ISIS Hello message, the ISIS Hello message carries a BIER BFD sub-TLV, and the BIER BFD sub-TLV carries the BFD information.

When the IGP is the OSPF protocol, the BFER receiving the BFD information advertised by the BFIR based on the IGP includes: the BFD information carried by the BFIR in the advertised message based on the OSPF protocol is received by the BFER.

The advertised message is an OSPF Hello message, the OSPF Hello message carries the BIER BFD sub-TLV, and the BIER BFD sub-TLV carries the BFD information.

Establishing the BFD session corresponding to the BFIR according to the BFD control packet and the BFD information includes: a BFER node parses the BFD control packet after receiving the BFD control packet; and when the node information of the BFIR and the discriminator carried in the BFD control packet are consistent with the stored BFD information, the BFD session corresponding to the BFER node is established.

The embodiments of the present invention provide another method of establishing a BFD session based on BIER. As shown in <FIG>, the method includes the followings.

In step <NUM>, a BFIR node initiates a BIER BFD process to establish a BFD session.

In step <NUM>, the BFIR node uses an IGP protocol to advertise BIER BFD information.

For example, an ISIS or OSPF protocol is used to advertise the BIER BFD information. An advertised message may carry a BIER BFD sub-TLV, and parameters carried by the BIER BFD sub-TLV include a globally unique discriminator assigned by the BFIR to a multi-point path and a BIFT-id and a bit string to which a BFER group to be notified belongs.

To be specific, IGP-Traffic Engineering (IGP-TE) may be extended, and bootstrap information of the BIER BFD, i.e., BFD information may be notified based on an OSPF or ISIS protocol. The BFD information includes the globally unique discriminator assigned to the multi-point path by a first node of a BFIR network, and information of the BIFT-id and the bit string of a last node with which the first node expects to establish the BFD session and link detection. When the BIER BFD information is notified through the ISIS protocol to establish the BFD session, for example, a new BIER BFD sub-TLV may be carried in the advertised message, and the sub-TLV is used for carrying the BFD information. When the BIER BFD information is notified through the OSPF protocol to establish the BFD session, the new BIER BFD sub-TLV may be carried in the advertised message, and the sub-TLV is used for carrying the BFD information.

A purpose of advertising is to advertise the BFD information to a BFER group. This BFER group is all BFERs (which are one or more BFERs) with which the BFIR expects to establish the BFD session.

In step <NUM>, after receiving the advertised message, the BFER node stores the BIER BFD information.

It is may be determined by the BFER node whether itself is included in BFER nodes to be notified according to the BIFT-id and the bit string in the received BFD information. When it is determined that itself is included in the BFER nodes to be notified, and the BFER determines that itself is a BFER node corresponding to the BIFT-id and the bit string in the BFD information, the BFER node stores the received BFD information.

In step <NUM>, the BFIR node transmits a BFD control packet to the BFER node.

The BFD control packet is a multi-point control packet, and the BFIR node may transmit the BFD control packet to all BFER nodes that are expected to establish the BFD session.

The control packet carries node information of the BFIR and the globally unique discriminator assigned by the BFIR to the multi-point path.

In step <NUM>, after receiving the BFD control packet, the BFER node parses the BFD control packet, and establishes the BFD session corresponding to the BFIR node in response to the node information of the BFIR and the discriminator carried in the BFD control packet being consistent with the stored BFD information.

According to the technical scheme provided in this implementation, the IGP protocol is used to advertise the BFD information in the BIER network to realize the establishment of the BIER BFD session, thereby completing a BIER bidirectional path detection mechanism.

The embodiments of the invention extend the ISIS protocol and provide a new BIER BFD sub-TLV used for carrying the BFD information, and a format of the BIER BFD sub-TLV is shown in <FIG>.

Type: Type may be assigned a value TBD1 indicating that the TLV is a BIER BFD sub-TLV of the ISIS protocol, and may be <NUM> bits.

Length: Length indicates a length of the TLV, and may be <NUM> bits.

Discriminator: Discriminator indicates a globally unique discriminator assigned by a BFIR to a multi-point path, and may be <NUM> bits.

RESERVED: a reserved field may be <NUM> bits.

BIFT-id: BIFT-id indicates a BIFT-id to which a BFER group to be notified belongs, and may be <NUM> bits.

BitString: BitString may be lengthened, and indicates a bit string formed by bit positions of the BFER group to be notified.

The BIER BFD sub-TLV may be carried in a first message advertised by the BFIR based on the ISIS protocol. The first message may be an ISIS Hello message, etc. To be specific, the BIER BFD sub-TLV may be carried in an ISIS Capability type length value (Capability TLV) or other objects in the ISIS Hello message.

The embodiments of the invention extend the OSPF protocol and provide a new BIER BFD sub-TLV used for carrying the BFD information, and a format of the BIER BFD sub-TLV is shown in <FIG>.

Type: Type may be assigned a value TBD2 indicating that the TLV is a BIER BFD sub-TLV of the OSPF protocol, and may be <NUM> bits.

The BIER BFD sub-TLV may be carried in a second message advertised by the BFIR based on the OSPF protocol. The second message may be an OSPF Hello message, etc. To be specific, the BIER BFD sub-TLV may be carried in a Router Information Link State Advertisement (LSA) or other objects in the OSPF Hello message.

Based on the BIER domain shown in <FIG>, the embodiments of the present invention provide another method of establishing a BFD session based on BIER. In this implementation, parameters of the BIER domain are configured as: BIFT-id=<NUM>, a bit position (BP) of a BFIR1 is <NUM>, a BP of a BFIR2 is <NUM>, BPs of three BFRs are <NUM>, <NUM> and <NUM> respectively, a BP of a BFER1 is <NUM>, and a BP of a BFER2 is <NUM>. The BFIR1 transmits a multicast service to the BFER1 and the BFER2 through the BIER domain.

As shown in <FIG>, the method includes the followings.

In step <NUM>, the BFIR1 node initiates a BIER BFD process to establish a BFD session.

A type of the session is MultipointHead, an establishment mode is set to an on-demand mode, and a role is set to an active mode.

In step <NUM>, the BFIR1 node initiates an ISIS protocol to advertise BIER BFD information.

To be specific, an ISIS Capability TLV may be carried in an ISIS Hello message, and a BIER BFD sub-TLV may be carried in the ISIS Capability TLV. Parameters carried in the BIER BFD sub-TLV include: Discriminator =<NUM> of the BFIR1 node, and BIFT-id =<NUM> and BitString=<NUM>, to which the BFER1 and BFER2 nodes to be notified belong.

In step <NUM>, after receiving the advertised message, the BFER1 and BFER2 nodes store the BFD information.

In step <NUM>, the BFIR1 node transmits a BFD control packet to the BFER1 and BFER2 nodes.

The control packet carries a globally unique discriminator assigned by the BFIR to a multi-point path.

In step <NUM>, after receiving the BFD control packet, the BFER1 and BFER2 nodes parse the packet and establish BFD sessions corresponding to the BFIR1.

The types of the sessions are MultipointTail, the establishment mode is set to an asynchronous mode, and the role is set to a passive mode. The establishments of the BIER BFD sessions are completed.

According to the technical scheme provided in this implementation, the ISIS protocol is used to notify the BIER BFD information to realize the establishments of the BIER BFD sessions, thereby realizing BFD of the BIER.

Based on the BIER domain shown in <FIG>, the embodiments of the present invention provide a method of establishing a BFD session based on BIER. In this implementation, parameters of the BIER domain are configured as: BIFT-id=<NUM>, a bit position (BP) of a BFIR1 is <NUM>, a BP of a BFIR2 is <NUM>, BPs of three BFRs are <NUM>, <NUM> and <NUM> respectively, a BP of a BFER1 is <NUM>, and a BP of a BFER2 is <NUM>. The BFIR1 transmits a multicast service to the BFER1 and the BFER2 through the BIER domain.

In step <NUM>, the BFIR1 node initiates an OSPF protocol to advertise BIER BFD information.

To be specific, a Router Information LSA may be carried in an OSPF Hello message, and a BIER BFD sub-TLV may be carried in the Router Information LSA. Parameters carried in the BIER BFD sub-TLV include: Discriminator =<NUM> of the BFIR1 node, and BIFT-id =<NUM> and BitString=<NUM>, to which the BFER1 and BFER2 nodes to be notified belong.

According to the technical scheme provided in this implementation, the OSPF protocol is used to notify the BIER BFD information to realize the establishments of the BIER BFD sessions, thereby realizing BFD of the BIER.

The embodiments of the present invention provide a BFIR, as shown in <FIG>, including the followings.

An establishing unit, used for establishing a BFD session.

A flooding unit, used for advertising BFD information to a BFER group based on an IGP.

A transmitting unit, used for transmitting a BFD control packet to a BFER, to trigger the BFER to establish the BFD session corresponding to the BFIR.

The BFD information includes: a globally unique discriminator assigned by the BFIR to a multi-point path, and a BIFT-id and a bit string to which the BFER group belongs.

The flooding unit is specifically used for, when the IGP is the ISIS protocol, carrying the BFD information in an advertised message based on the ISIS protocol.

The flooding unit is specifically used for, when the IGP is the OSPF protocol, carrying the BFD information in the advertised message based on the OSPF protocol.

The embodiments of the present invention provide a BFER, as shown in <FIG>, including the followings.

A receiving unit, used for receiving BFD information advertised by a BFIR based on an IGP.

A storing unit, used for storing the BFD information.

An establishing unit, used for establishing a BFD session corresponding to the BFIR according to a BFD control packet and the BFD information, after receiving the BFD control packet transmitted by the BFIR.

The storing unit is specifically used for, when the BFER determines that itself is a BFER node corresponding to the BIFT-id and the bit string in the BFD information, storing the BFD information.

The receiving unit is specifically used for, when the IGP is the ISIS protocol, receiving the BFD information carried by the BFIR in an advertised message based on the ISIS protocol.

The receiving unit is specifically used for, when the IGP is the OSPF protocol, receiving the BFD information carried by the BFIR in the advertised message based on the OSPF protocol.

The establishing unit is specifically used for parsing the BFD control packet after receiving the BFD control packet; and when the node information of the BFIR and the discriminator carried in the BFD control packet are consistent with the stored BFD information, establishing the BFD session corresponding to the BFER node.

The embodiments of the present invention provide a system of establishing a BFD session based on BIER, as shown in <FIG>.

The BIER is used for establishing the BFD session, advertising BFD information to a BFER group based on an IGP, and transmitting a BFD control packet to the BFER.

The BFER is used for receiving the BFD information advertised by the BFIR based on the IGP, storing the BFD information, and establishing the BFD session corresponding to the BFIR according to the BFD control packet and the BFD information, after receiving the BFD control packet transmitted by the BFIR.

The embodiments of the present invention further provide a BFIR, including a memory, a processor and a computer program stored on the memory and capable of being executed by the processor. When the computer program is executed by the processor, any one of the above-mentioned methods of establishing the BFD session executed by the BFIR is realized.

The embodiments of the present invention further provide a BFER, including a memory, a processor and a computer program stored on the memory and capable of being executed by the processor. When the computer program is executed by the processor, any one of the above-mentioned methods of establishing the BFD session executed by the BFER is realized.

The embodiments of the present invention further provide a computer-readable storage medium storing an information processing program thereon. When the information processing program is executed by a processor, steps of any one of the above-mentioned methods of establishing the BFD session are realized.

Claim 1:
A method of establishing a bidirectional forwarding detection, BFD, session based on bit index explicit replication, BIER, comprising:
creating (<NUM>), by a bit-forwarding ingress router, BFIR, the BFD session;
advertising (<NUM>), by the BFIR, BFD information to a bit-forwarding egress router, BFER, group based on an Interior Gateway Protocol, IGP; and
sending (<NUM>), by the BFIR, a BFD control packet to the BFER group, to trigger the BFER group to establish the BFD session corresponding to the BFIR;
wherein the BFD information comprises: a globally
unique discriminator assigned by the BFIR to a
multi-point path, a BIER forwarding table identifier, BIFT-id, and a bit string to which the BFER group belongs.