CN111245731B

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

Info

Publication number: CN111245731B
Application number: CN202010110693.5A
Authority: CN
Inventors: 瞿辉; 王亚昕; 蒋元兵; 袁星勇; 谢文希; 陈量; 王建兵; 罗明阳; 康宗绪; 夏洪君
Original assignee: Chongqing Jinmei Communication Co Ltd
Current assignee: Chongqing Jinmei Communication Co Ltd
Priority date: 2020-02-24
Filing date: 2020-02-24
Publication date: 2021-11-23
Anticipated expiration: 2040-02-24
Also published as: CN111245731A

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. A IP data multicast transmission method, utilize the border router of the explicit duplication technology of bit index to set up the tunnel, make the signalling of PIM router can be transmitted to the PIM router of the far-end transparently, its characteristic is "BIER router and neighbour of PIM router maintain", "Bootstrap router mechanism of BIER router", "assertion of BIER router process" the combination of three functional methods;

function one: neighbor maintenance of the BIER router and the PIM router; after a BIER router identifies a PIM neighbor maintenance message, the BIER router needs to identify itself as a BBR besides establishing a neighbor relation with the PIM router, identity information is diffused to other BBRs by adopting a BIER forwarding technology, each BBR in a BIER domain needs to determine the node numbers of other BBRs, and after the PIM router neighbor fails, the adjacent BBR identifies itself as no BBR any more, and the identity information is diffused to other BBRs;

and a second function: bootstrap router mechanism of BIER router; after receiving the BSR message in the multicast form, the BBR diffuses the BSR message to all other PIM routers connected with the BBR, the method is that a BIER prefix is superposed on the head of the original message, a BitString field fills in ID values of all other BBRs, the ID values are forwarded through BIER technology, after receiving the message, other BBRs remove the BIER bit prefix, and the message also needs to be identified as a BSR flooding message and is forwarded to a neighbor PIM router;

and function III: assertion processing of the BIER router; the bfer needs to check whether the outgoing interface of the multicast forwarding table receives the multicast packet sent by itself according to the mode specified by the PIM router, and if the outgoing interface receives the data packet conforming to the multicast forwarding table, sends an assertion message to the outgoing interface to determine which router on the outgoing interface network continues to forward the multicast packet, selects a forwarding router to execute a standard PIM assertion rule, and prunes the outgoing interface by the unselected BIER router.