CN111245731B - Improved method for protocol independent multicast signaling to pass through BIER - Google Patents

Abstract

The invention relates to a multicast signaling transmission method of an IP network. The application scenario of the invention is that Bit Index Explicit Replication technology (BIER) is locally operated in a large IP network, the rest part of the network operates Protocol Independent Multicast (PIM) Protocol, a Multicast sending terminal and a receiving terminal are distributed in an area isolated by the Bit Index Explicit Replication technology, and a tunnel is established by the Bit Index Explicit Replication technology for intercommunication. The invention establishes the signaling tunnel in the bit index explicit replication technology area to ensure that the protocol independent multicast protocol can operate without perception, and establishes the service tunnel to guide the multicast flow.

Description

Improved method for protocol independent multicast signaling to pass through BIER

Technical Field

The technical field related to the invention is IP data Multicast communication, and particularly relates to a technology for establishing a tunnel by using a Bit Index Explicit Replication (BIER) technology to complete communication of Protocol Independent Multicast (PIM) signaling.

Background

The PIM can work with any unicast routing protocol, is the multicast routing protocol which is most widely applied at present, operates on a multicast router, and is used for establishing and maintaining the multicast routing and correctly and efficiently forwarding multicast data packets. Protocol independent multicast is divided into Dense Mode (DM) and Sparse Mode (SM). SM is an explicit join model, relying on "join messages" and "prune messages" to build multicast trees. PIM establishes a multicast tree to forward data streams, each stream needs to maintain the multicast tree and a stream state, which makes the growth of a multicast table and a multicast state of a network node the most complex and uncontrollable part in a multicast network.

BIER provides a very simplified method to solve the multicast Forwarding problem, each edge device in the BIER domain floods the assigned unique bp (Bit position), all BIER Forwarding devices calculate the shortest path to the edge node using the unicast routing Table to form a Bit Forwarding Table (Bit Forwarding Table), and the data packet will be forwarded and copied hop by hop according to the Bit Forwarding Table to complete the Forwarding of the multicast data stream. The technology eliminates complex multicast protocols and multicast forwarding tables, and has the advantages of simple deployment, rapid convergence, high distribution efficiency and support of ultra-large capacity services.

The IETF research group issued a draft of PIM Signaling Through BIER Core, version 06, on 23.4.2019, which includes the following main contents:

1. PIM 'join/prune' signaling traversing BIER domain: defining boundary nodes of a PIM domain and BIER, defining interfaces of PIM multicast forwarding tables of the boundary nodes, and defining values and use methods of fields of header formats of built and forwarded messages of BIER tunnels;

2. the process of the multicast data stream passing through the BIER domain: the process of multicast data stream reaching domain boundary is defined (from PIM domain into BIER domain, from BIER domain into PIM domain).

In describing implementation of PIM crossing over BIER domain, the signaling layer only defines processing of "join/prune" message of PIM, and does not include complete PIM signaling, including:

1. PIM neighbor maintenance (Hello), the border router receives the neighbor maintenance message of the opposite PIM router to process;

2. a Bootstrap router mechanism, which is an important content of PIMv2, and how a Bootstrap router (BSR) elects through a BIER domain and issues mapping information from a group to a concentration Point (RP);

3. assertion (Assert), processing of assertion messages.

Due to the lack of description above, engineering to implement BIER as a tunneling PIM will face a number of problems.

Disclosure of Invention

Based on the practical problems mentioned in the background, the present invention proposes an improved method to complete the forwarding of BIER as a tunneling process PIM signaling, and the specific method is completed by using the following combination. The method comprises the following steps:

BIER Router and PIM Router neighbor maintenance processing: the BIER router receives the PIM neighbor maintenance message, identifies itself as a region border router (BBR), starts to perform neighbor maintenance, and performs diffusion in the BIER domain on the identity of the BBR;

processing of Bootstrap router mechanism by BIER router: the process comprises three parts, namely BSR election, candidate RP (C-RP) collection and candidate RP notification, wherein a BIER router does not directly participate in a Bootstrap router mechanism, only provides a tunnel mode to transmit a multicast message of Bootstrap to a BBR, a unicast message of Bootstrap depends on IP unicast routing of the whole network, and the BIER router only executes IP unicast forwarding;

processing of assertions by BIER routers: the assertion is divided into the processing of a BIER ingress router (BFIR) and the processing of a BIER egress router (BFER), wherein the BFIR does not process the received assertion message and the BFER detects whether the multicast message is received from an egress interface of the multicast forwarding table, and if the condition is satisfied, the BFER actively sends the assertion message on the egress interface.

The invention has the beneficial effects that: through the combination of the methods, a BIER tunnel connection PIM can be established, so that IP multicast data can pass through the BIER to complete forwarding.

Drawings

FIG. 1 is a topological illustration of neighbor maintenance;

fig. 2 is a topological illustration of assertion message processing.

Detailed Description

The specific implementation mode comprises the following functional units with 3 aspects:

neighbor maintenance for BIER and PIM routers

The BIER router needs to identify the neighbor maintenance message of the PIM router, where the IP header protocol number is 103, the destination IP address of the IP header is 224.0.0.13, and the message with the PIM header type field of 0(Hello) is the PIM neighbor maintenance message.

Taking fig. 1 as an example, neighbor relations are established between 2.0.0.1 and 3.0.0.1, between 2.0.0.2 and 3.0.0.2, between 2.0.0.3 and 3.0.0.3, and between 2.0.0.4 and 3.0.0.4, respectively.

After the BIER router identifies the PIM neighbor maintenance message, a neighbor relation is required to be established with the PIM router, and the PIM neighbor maintenance message is periodically sent to the PIM router. In addition, the user needs to identify the user as a BBR, and identity information is diffused to other BBRs by adopting a BIER forwarding technology, and each BBR in a BIER domain needs to determine the node numbers of the other BBRs. When the PIM router neighbor fails, the adjacent BBR mark is no longer BBR, and the identity information is diffused to other BBRs, so that the non-BBR can not participate in the subsequent BSR election process, and the PIM signaling message transmitted by the BIER tunnel can not be received.

Bootstrap router mechanism for BIER router

The boottrap router mechanism comprises three parts: BSR election, candidate RP (C-RP) collection, candidate RP advertisement.

The BBR needs to identify BSR messages of PIM, IP header protocol number 103, and messages with PIM header type field of 4(BootStrap) as BSR messages. Wherein, the BSR election and the candidate RP notification adopt flooding transmission, the candidate RP collection adopts unicast transmission, the unicast transmission adopts general IP forwarding, and the flooding transmission process needs special treatment.

The BSR election process is that candidate BSRs send BSR messages to flood in the whole PIM domain, and the only BSR is selected according to election rules. Therefore, after receiving the BSR packet in multicast form, the BBR will spread to all other PIM routers connected to the BBR. The method is that a BIER prefix is superposed on the head of an original message, and the BitString field fills in the ID values of all other BBRs and forwards the ID values through a BIER technology. After receiving the message, other BBRs remove the BIER bit prefix, and also need to identify the message as a BSR flooding message and forward the BSR flooding message to the neighboring PIM router.

The candidate RP notification process is that the BSR floods the collected candidate RP information in the entire PIM domain, so that all PIM routers acquire the candidate RP information. The message is in multicast form, so the processing mode of the BBR receiving the message is the same as that of BSR election.

And a Bootstrap router mechanism, wherein the BIER establishes a transmission tunnel for the PIM, and the BIER router does not participate in BSR election and cannot be used as a candidate RP.

Assertion handling for BIER routers

An assertion is a mechanism by which a PIM router selects a forwarding router on a broadcast network. Within the BIER domain, assertions are associated with BIER ingress routers (bfir) and BIER egress routers (bfer).

At the entry boundary of the BIER domain, the bfir does not process the received assertion message.

The bfer, besides performing forwarding processing of the boundary multicast packet specified by IETF, needs to check whether the outgoing interface of the multicast forwarding table receives the multicast packet sent by itself according to a mode specified by the PIM router, and if a data packet conforming to the multicast forwarding table is received on the outgoing interface, sends an assertion message to the outgoing interface to determine which router on the outgoing interface network continues forwarding the multicast packet. The selective forwarding router executes standard PIM assertion rules, and the unselected BIER routers prune the outgoing interface.

For example, in fig. 2, bfir 3.0.0.1 would receive assertion messages of 2.0.0.1 and 2.0.0.2, which are not processed. The bfers 3.0.0.2 and 3.0.0.4 will execute the forwarding rules of PIM and will send assertion messages to determine who to forward a particular (source, group) multicast stream.

Claims (1)

Translated fromChinese

1.一种IP数据组播传输方法，利用比特索引显式复制技术的边界路由器建立隧道，使得PIM路由器的信令可以透明传输到远端PIM路由器，其特征为“BIER路由器与PIM路由器的邻居维护”、“BIER路由器的Bootstrap路由器机制”、“BIER路由器的断言处理”三个功能方法的组合；1. a kind of IP data multicast transmission method, utilizes the border router of bit index explicit duplication technology to set up tunnel, makes the signaling of PIM router can be transparently transmitted to remote PIM router, it is characterized in that " the neighbor of BIER router and PIM router. A combination of three functional methods: "Maintenance", "Bootstrap router mechanism of BIER router", and "Assertion processing of BIER router";功能一：BIER路由器与PIM路由器的邻居维护；具体方法为BIER路由器识别出PIM邻居维护报文后，除了和PIM路由器建立邻居关系之外还需要标识自己为BBR，并采用BIER转发技术将身份信息扩散到其他BBR，BIER域内每个BBR均需明确其他BBR的节点号，当PIM路由器邻居失效后，邻接BBR标识自己不再是BBR，并将身份信息扩散到其他BBR；Function 1: Neighbor maintenance between the BIER router and the PIM router; the specific method is that after the BIER router identifies the PIM neighbor maintenance message, in addition to establishing a neighbor relationship with the PIM router, it also needs to identify itself as a BBR, and use the BIER forwarding technology to transfer the identity information. To spread to other BBRs, each BBR in the BIER domain needs to specify the node numbers of other BBRs. When the PIM router neighbor fails, the adjacent BBR identifies itself as no longer a BBR, and spreads the identity information to other BBRs;功能二：BIER路由器的Bootstrap路由器机制；BBR收到组播形式的BSR报文后将扩散到其它所有的BBR连接的PIM路由器，方法是在原始报文的头部叠加BIER前缀，BitString字段填写其它所有BBR的ID值，通过BIER技术转发，其它BBR收到此报文后，去除BIER比特前缀，同样需要识别此报文为BSR泛洪报文，并转发给邻居PIM路由器；Function 2: Bootstrap router mechanism of BIER router; after BBR receives multicast BSR message, it will spread to all other PIM routers connected to BBR by superimposing BIER prefix on the header of original message, and fill in other bits in BitString field. The ID values of all BBRs are forwarded through the BIER technology. After other BBRs receive this packet, they remove the BIER bit prefix, and also need to identify this packet as a BSR flooding packet and forward it to the neighboring PIM router;功能三：BIER路由器的断言处理；bfer执行IETF规定的边界组播报文转发处理之外，需要按照PIM路由器规定的方式检查组播转发表的外出接口是否收到自己发送的组播包，如果在外出接口上收到符合组播转发表的数据包，则向该外出接口发送断言消息，以确定外出接口网络上哪台路由器继续转发该组播包，选择转发路由器执行标准的PIM断言规则，未被选择到的BIER路由器剪枝掉该出接口。Function 3: Assertion processing of the BIER router; in addition to performing the forwarding processing of boundary multicast packets specified by IETF, bfer needs to check whether the outbound interface of the multicast forwarding table receives the multicast packets sent by itself according to the method specified by the PIM router. If a data packet that conforms to the multicast forwarding table is received on the outgoing interface, an assertion message is sent to the outgoing interface to determine which router on the outgoing interface network continues to forward the multicast packet, and the forwarding router is selected to implement the standard PIM assertion rules. The BIER router that is not selected will prune the outgoing interface.

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