Protocol-independent satellite network multicast method

Abstract

The invention provides a protocol-independent satellite network multicast method, which comprises the following steps of: completing routing convergence of the whole network by adopting an IGP (Internet Group Protocol) unicast routing protocol to obtain a unicast routing table of each satellite, calculating a bit index forwarding table corresponding to each port through the unicast routing table, and realizing multicast flow forwarding according to the bit index forwarding table. According to the invention, the blank of the current satellite network multicast technology is filled, and the bandwidth pressure of the satellite network is relieved; a traditional complex ground internet multicast protocol such as PIM is prevented from being used on a satellite, and bandwidth overhead and processor pressure generated by maintaining a multicast group and a multicast tree are reduced. According to the invention, it is not required to extend IS-IS or OSPFv3 protocol interaction END.BIER and other SID labels, only the bottom layer needs to support the standard IGP protocol, modification of the existing standard protocol is avoided, and the realization difficulty is simplified. The method not only can be applied to an IP-based protocol stack system, but also can be expanded to a protocol stack of a non-IP system as long as a bottom layer supports a dynamic routing protocol, and the scheme has the advantages of being wide in application range and high in expandability.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a protocol-independent satellite network multicast method. Background Art

[0002] In large-scale constellation networks, the demand for multicast in satellite communications is increasingly strong. Due to the dynamic changes in large-scale constellation topology, the multicast technologies commonly used in traditional Internet, such as the Protocol Independent Multicast (PIM) protocol, are relatively complex and have weak scalability. Intermediate nodes need to maintain the multicast status of each stream, introducing additional control signaling in the network. In addition, when the multicast traffic increases, the number of multicast trees in the network will also increase, which not only occupies a large amount of resources, such as memory and CPU, but also has problems such as extended convergence time after network failures. It cannot meet the low latency and high reliability requirements of some services, so it is not conducive to deployment in large-scale satellite networks.

[0003] Therefore, a communication method is needed that can meet the multicast service requirements of large-scale constellations. Summary of the invention

[0004] The present invention aims to solve the problems that traditional multicast protocols are relatively complex, have weak scalability, high network overhead, low reliability, difficult deployment and operation and maintenance, and that the new Bit Index Explicit Replication IPv6 encapsulation (BIERv6) multicast solution cannot fully adapt to the scenario of tight onboard resources. A protocol-independent satellite network multicast method is provided. This method is based on the relatively fixed characteristics of satellite neighbor relationships and is a simplified Bit Index Explicit Replication (S-BIER) algorithm. It can greatly reduce satellite computing complexity and network overhead, and is independent of the network protocol stack structure, filling the demand for multicast services in large-scale constellations.

[0005] The present invention provides a protocol-independent satellite network multicast method, comprising the following steps:

[0006] S1. Allocate addresses for each satellite in the multicast network, and distinguish each satellite by satellite number;

[0007] S2. Define a service multicast string. Each satellite occupies an independent and non-repetitive position in the service multicast string. When a character position in the service multicast string is set to 1, it indicates that the satellite corresponding to the character position needs to receive the service multicast.

[0008] S3, each satellite router runs the IGP protocol and exchanges link state information or routing tables with each other;

[0009] S4. After the whole network routing convergence is completed, each satellite node learns the next hop routing table to reach other satellites in the whole network;

[0010] S5. Each satellite node performs bit mapping on the routing table and generates a bit index forwarding table for each interface. The bit index forwarding table refers to all destination satellites with the current interface as the next hop.

[0011] Determine whether the topology has changed, if yes, return to step S3, if no, go to step S6;

[0012] S6. The multicast source generates a multicast service. The basic header uses the multicast address negotiated on the ground. At least two independent multicast addresses are set for different satellites. Each satellite converts the group member to which the service is to be sent into a service multicast string and carries it in the multicast service extension header.

[0013] S7. After receiving the traffic, each multicast satellite determines whether it is multicast traffic. If not, it forwards it in unicast mode according to the unicast routing table. If yes, it performs port mapping according to the bit index forwarding table, modifies the service multicast string, and continues to forward the multicast traffic to the next hop link. It continues to receive traffic, and a protocol-independent satellite network multicast method is completed.

[0014] The protocol-independent satellite network multicast method described in the present invention is a preferred method. In step S1, it is determined whether the multicast uses the IP protocol system. If so, the address prefix contains the satellite number; if not, each satellite can be mapped to a routing table, and other satellites can infer the satellite identity through the routing table.

[0015] The protocol-independent satellite network multicast method of the present invention is preferably configured such that in step S1, the address is an IPv6 address, and the address includes a prefix identifier and a host identifier;

[0016] The satellite number is a satellite identity ID represented by at least one bit, and the satellite number is not repeated within the satellite network.

[0017] The protocol-independent satellite network multicast method described in the present invention is, as a preferred method, the address includes a global routing prefix, a subnet ID and an interface ID; the method of embedding the satellite number into the address is: embedding the satellite number into the subnet ID.

[0018] The protocol-independent satellite network multicast method described in the present invention is, as a preferred embodiment, in step S2, the total length of the service multicast string is greater than or equal to the total number of satellites in the constellation, and the length of the service multicast string is an integer multiple of 8.

[0019] The protocol-independent satellite network multicast method described in the present invention is, as a preferred embodiment, in step S2, the length of the service multicast string is greater than or equal to the number of satellites, and 1 bit represents 1 satellite.

[0020] The present invention discloses a protocol-independent satellite network multicast method, as a preferred method, in step S5, the satellite converts the relationship between each routing table and the next-hop interface into the relationship between other satellites in the entire network and the corresponding interface of the next hop, screens out the satellite with the corresponding interface of the next hop as the next hop and sets the corresponding position in the character string of the bit index forwarding table, and after the satellite traverses all routing tables, the bit index forwarding table corresponding to each interface is generated.

[0021] The protocol-independent satellite network multicast method of the present invention is preferably configured such that in step S7, after the multicast satellite receives the multicast traffic, the service multicast string in the multicast service extension header is extracted and ANDed with the bit index forwarding table of each interface;

[0022] Determine whether the result of the AND operation is non-zero. If so, there are multicast members downstream of the current interface. It is necessary to forward a copy of the multicast traffic to the interface with a non-zero result of the AND operation, and make the result of the OR of the service multicast string forwarded by each interface a subset or the same of the service multicast string in the received multicast traffic.

[0023] The present invention discloses a protocol-independent satellite network multicast method. As a preferred method, when forwarding multicast traffic, the satellite modifies the service multicast character string in the multicast service extension header to an AND operation result; if the flag bit corresponding to the local satellite in the service multicast character string is set, the flag bit is set to 0 during forwarding.

[0024] The protocol-independent satellite network multicast method described in the present invention is a preferred method. When the satellite network topology changes, each satellite recalculates the unicast routing table and updates the bit index forwarding table. When subsequent multicast traffic arrives, the traffic is forwarded according to the new bit index forwarding table.

[0025] The present invention is a method for realizing large-scale constellation multicast communication based on S-BIER, belonging to the technical field of satellite mobile communication systems.

[0026] The present invention refers to a new multicast scheme of Bit Index Explicit Replication IPv6 encapsulation (BIERv6) in the next generation technology of Internet IPv6. BIERv6 encapsulates the set of destination nodes of the multicast message in the form of a bit string (BitString) in the message header and sends it. The intermediate nodes do not need to establish a multicast distribution tree and save the flow state for each multicast stream. Data forwarding is completed only according to the bit string in the message header, which reduces the calculation pressure and network overhead. In view of the relatively fixed characteristics of satellite neighbor relationships, the present invention simplifies the BIERv6 mechanism and designs a simplified bit index explicit replication algorithm (Simplified Bit Index Explicit Replication, S-BIER) without the need to exchange labels through the IGP protocol (such as IS-IS). The satellite transponder only needs to calculate the bit index forwarding table according to the unicast routing table to complete the distribution of multicast services. Compared with traditional multicast routing protocols such as PIM, this mechanism greatly reduces the satellite calculation complexity and network overhead, and does not rely on the network protocol stack structure, filling the demand for multicast services in large-scale constellations.

[0027] The basic idea of ​​the present invention is to use the unicast routing protocol to detect the network topology and generate a bit index forwarding table to avoid the satellite from generating additional bandwidth overhead and processor pressure due to the maintenance of multicast groups and multicast trees. Based on the ground BIERv6 concept, the multicast member information is carried in the message header, but there is no need to extend the dynamic routing protocol interaction label, which reduces the pressure of on-board extension protocol and has guiding significance for the development of satellite network multicast protocols.

[0028] The present invention relates to a method for implementing a protocol-independent satellite network multicast solution. The main steps include: (1) allocating addresses to each satellite in the multicast network, wherein each satellite is distinguished by a satellite number, and the address prefix includes the satellite number; (2) defining a service multicast string, wherein the length of the string can be set, wherein each satellite occupies an independent and non-repetitive position in the multicast string, and when certain positions in the service multicast string are set to 1, it indicates that the satellites corresponding to these positions need to receive a copy of the content; (3) based on step (2), each satellite router runs an IGP protocol and exchanges link status information or routing tables with each other; (4) after the whole network routing convergence is completed through step (3), each satellite node can learn the next-hop routing table to reach other satellites in the whole network; (5) each satellite node performs bit mapping on the routing table generated in step (4), and Each port generates a bit index forwarding table, which refers to all destination satellites with this interface as the next hop; (6) The multicast source generates multicast services. The basic header uses the multicast address negotiated on the ground. For different satellites, multiple independent multicast addresses can be set. Each satellite converts the group member to which the service is to be sent into a service multicast string and carries it in the multicast service extension header; (7) After each multicast satellite receives the traffic, it performs port mapping according to the bit index forwarding table, modifies the service multicast string, and continues to forward the traffic to the next hop link; (8) When the satellite network topology changes, each satellite recalculates the unicast routing table and updates the bit index forwarding table. When subsequent multicast traffic arrives, it forwards the traffic according to the new bit index forwarding table. This method innovatively proposes an on-board multicast solution, fills the gap in the current satellite network multicast technology, and alleviates the bandwidth pressure of the satellite network. Compared with the traditional ground PIM multicast routing protocol, this method avoids the use of complex multicast protocols such as PIM on the satellite, and reduces the bandwidth overhead and processor pressure caused by maintaining multicast groups and multicast trees. Compared with the terrestrial next-generation network BIERv6 solution, this method does not need to extend the IS-IS or OSPFv3 protocol interaction END.BIER and other SID tags, and only requires the underlying layer to support the standard IGP protocol, avoiding modifications to existing standard protocols and simplifying the implementation difficulty. In addition, this method can not only be applied to IP-based protocol stack systems, but can also be extended to non-IP system protocol stacks, as long as the underlying layer supports dynamic routing protocols, which has the advantages of wide application range and strong scalability.

[0029] The present invention has the following advantages:

[0030] (1) The present invention innovatively proposes an on-board multicast solution, which fills the gap in the current satellite network multicast technology and alleviates the bandwidth pressure of the satellite network.

[0031] (2) The present invention avoids using traditional complex multicast protocols of the terrestrial Internet such as PIM on the satellite, thereby reducing bandwidth overhead and processor pressure caused by maintaining multicast groups and multicast trees.

[0032] (3) Compared with the terrestrial next-generation network BIERv6 solution, the present invention does not need to extend the IS-IS or OSPFv3 protocol interaction END.BIER and other SID tags, and only requires the underlying layer to support the standard IGP protocol, thus avoiding modifications to the existing standard protocol and simplifying the implementation difficulty.

[0033] (4) The present invention can be applied not only to IP-based protocol stack systems, but also to protocol stacks of non-IP systems, as long as the underlying layer supports dynamic routing protocols. This solution has the advantages of wide applicability and strong scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a flow chart of a protocol-independent satellite network multicast method. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] Example 1

[0037] like Figure 1 As shown, a protocol-independent satellite network multicast method, the technical solution of the present invention: provides a method for implementing a satellite network multicast solution based on S-BIER. The IGP unicast routing protocol is used to complete the routing convergence of the entire network to obtain the unicast routing table of each satellite, and the bit index forwarding table corresponding to each port is calculated through the unicast routing table. According to the bit index forwarding table, multicast traffic forwarding is realized.

[0038] The specific steps are as follows:

[0039] (1) Allocate an address to each satellite in the multicast network. Each satellite is identified by a satellite number, and the address prefix contains the satellite number.

[0040] (2) Define a service multicast string. The length of the string can be set. Each satellite occupies an independent and non-repetitive position in the multicast string. When certain positions in the service multicast string are set to 1, it means that the satellites corresponding to these positions need to receive a copy of the content.

[0041] (3) Based on step (2), each satellite router runs the IGP protocol to exchange link state information or routing tables with each other;

[0042] (4) After the whole network routing convergence is completed through step (3), each satellite node can learn the next hop routing table to reach other satellites in the whole network;

[0043] (5) Each satellite node bit-maps the routing table generated in step (4) and generates a bit-indexed forwarding table for each port, which refers to all destination satellites with the interface as the next hop;

[0044] (6) The multicast source generates a multicast service. The basic header uses the multicast address negotiated on the ground. Multiple independent multicast addresses can be set for different satellites. Each satellite converts the group members to which the service is to be sent into into a service multicast string and carries it in the multicast service extension header.

[0045] (7) After receiving the traffic, each multicast satellite performs port mapping according to the bit index forwarding table, modifies the service multicast string, and continues to forward the traffic to the next hop link;

[0046] (8) When the satellite network topology changes, each satellite recalculates the unicast routing table and updates the bit index forwarding table. When subsequent multicast traffic arrives, it forwards the traffic according to the new bit index forwarding table.

[0047] Processing flow such as Figure 1 As shown, the specific implementation is as follows:

[0048] (1) Allocate addresses to each satellite in the multicast network. Each satellite is distinguished by its satellite number. If the IP protocol system is used, the address prefix contains the satellite number. If a non-IP system is used, each satellite can be mapped to a routing table, and other satellites can infer the satellite identity through the routing table.

[0049] In this embodiment, the satellite number is a satellite identity ID represented by a number of bits, that is, a satellite ID, which is unique within the satellite network.

[0050] Address refers to the IPv6 address, and also refers to the broad address that includes the prefix identifier and the host identifier. Taking the IPv6 address as an example, its structure is shown in the following table:

[0051]

[0052] Global routing prefix: assigned to an organization by a provider, usually at least 48 bits

[0053] Subnet ID: Organizations can use subnet ID to build local networks, usually up to the 64th bit;

[0054] Interface ID: Interface ID, used to identify a Host (device);

[0055] Prefix length: The bit length used by IPv6 for routing addressing, including the global routing prefix and subnet ID;

[0056] Satellite number embedded in address: The satellite number is embedded in the subnet ID. It can be a part of the subnet ID or equal to the subnet ID. In this way, routing addressing is equivalent to addressing the satellite. Given the satellite number, the satellite address can also be mapped and routing can be performed.

[0057] (2) Define a service multicast string. The length of the string can be set. Each satellite occupies an independent and non-repetitive position in the multicast string. When certain positions in the service multicast string are set to 1, it means that the satellites corresponding to these positions need to receive a copy of the content. The total length of the multicast string should be greater than the total number of satellites in the constellation.

[0058] The service multicast string is a string of bits representing the satellite identity, and its length is the same as the number of satellites. For example, if there are satellites 1 to 8 in the satellite network, 8 bits can be agreed in advance to represent the meaning of each bit in the bit string, as shown in the following table:

[0059] bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0

[0060] (3) Based on step (2), each satellite router runs the IGP protocol to exchange link state information or routing tables with each other;

[0061] (4) After the whole network routing convergence is completed through step (3), each satellite node can learn the next hop routing table to reach other satellites in the whole network;

[0062] (5) Each satellite node performs bit mapping on the routing table generated in step (4) and generates a bit index forwarding table for each port, which refers to all destination satellites with the interface as the next hop. Specifically, the satellite converts the relationship between each routing table and the next hop interface into the relationship between other satellites in the entire network and the corresponding interface of the next hop, selects the satellite with the interface as the next hop, and sets the corresponding position in the bit index forwarding table string. After the satellite traverses all routing tables, the bit index forwarding table corresponding to each interface is generated.

[0063] (6) The multicast source generates a multicast service. The basic header uses the multicast address negotiated on the ground. Multiple independent multicast addresses can be set for different satellites. Each satellite converts the group members to which the service is to be sent into into a service multicast string and carries it in the multicast service extension header.

[0064] (7) After receiving the traffic, each multicast satellite first determines the traffic type. If it is unicast traffic, it forwards it according to the unicast routing table. If it is multicast traffic, it extracts the service multicast string in the extended header and performs an AND operation with the bit index forwarding table of each interface. If the result is non-zero, it indicates that there is a multicast member downstream of the interface and a copy of the multicast traffic needs to be forwarded to the interface. At the same time, to avoid repeated transmission of multicast traffic in the network, the satellite needs to modify the service multicast string in the extended header to the result of the AND operation when forwarding the traffic. If the flag bit corresponding to the satellite in the service multicast string is set, it should be set to 0 when forwarding, to ensure that the OR result of the multicast service string forwarded from each interface is a subset of or the same as the service multicast string in the received multicast traffic.

[0065] (8) When the satellite network topology changes, each satellite recalculates the unicast routing table and updates the bit index forwarding table of each interface. When subsequent multicast traffic arrives, the traffic is forwarded according to the new bit index forwarding table.

[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A protocol-independent satellite network multicast method, characterized in that: The following steps are involved: S1. Allocate addresses for each satellite in the multicast network, and distinguish each satellite by satellite number; S2. Define a service multicast string, where each satellite occupies an independent and non-repetitive position in the service multicast string. When a character position in the service multicast string is set to 1, it indicates that the satellite corresponding to the character position needs to receive the service multicast. S3, each satellite router runs the IGP protocol and exchanges link state information or routing tables with each other; S4. After the whole network routing convergence is completed, each satellite node learns the next hop routing table to reach other satellites in the whole network; S5. Each satellite node performs bit mapping on the routing table and generates a bit index forwarding table for each interface, wherein the bit index forwarding table refers to all destination satellites with the current interface as the next hop; Determine whether the topology has changed, if yes, return to step S3, if no, go to step S6; S6. The multicast source generates a multicast service. The basic header uses the multicast address negotiated on the ground. At least two independent multicast addresses are set for different satellites. Each satellite converts the group member to which the service is to be sent into the service multicast string and carries it in the multicast service extension header. S7, after receiving the traffic, each multicast satellite determines whether it is multicast traffic. If not, it forwards it in unicast mode according to the unicast routing table; If yes, port mapping is performed according to the bit index forwarding table, the service multicast string is modified, and the multicast traffic continues to be forwarded to the next hop link; the traffic continues to be received, and a protocol-independent satellite network multicast method is completed.

2. The protocol-independent satellite network multicast method according to claim 1, characterized in that: In step S1, it is determined whether the multicast uses the IP protocol system. If yes, the address prefix contains the satellite number; if not, each satellite can be mapped to a routing table, and other satellites can infer the satellite identity through the routing table.

3. The protocol-independent satellite network multicast method according to claim 1, characterized in that: In step S1, the address is an IPv6 address, and the address includes a prefix identifier and a host identifier; The satellite number is a satellite identity ID represented by at least one bit, and the satellite number is not repeated within the satellite network.

4. The protocol-independent satellite network multicast method according to claim 3, characterized in that: The address includes a global routing prefix, a subnet ID and an interface ID; the method for embedding the satellite number into the address is: embedding the satellite number into the subnet ID.

5. The protocol-independent satellite network multicast method according to claim 1, characterized in that: In step S2, the total length of the service multicast string is greater than or equal to the total number of satellites in the constellation, and the length of the service multicast string is an integer multiple of 8.

6. The protocol-independent satellite network multicast method according to claim 5, characterized in that: In step S2, the length of the service multicast string is greater than or equal to the number of satellites, and 1 bit represents 1 satellite.

7. The protocol-independent satellite network multicast method according to claim 1, characterized in that: In step S5, the satellite converts the relationship between each routing table and the next-hop interface into the relationship between other satellites in the entire network and the corresponding interface of the next hop, screens out the satellite with the corresponding interface of the next hop as the next hop and sets the corresponding position in the string of the bit index forwarding table. After the satellite traverses all routing tables, the bit index forwarding table corresponding to each interface is generated.

8. The protocol-independent satellite network multicast method according to claim 1, characterized in that: In step S7, after the multicast satellite receives the multicast traffic, it extracts the service multicast string in the multicast service extension header and performs an AND operation with the bit index forwarding table of each interface; Determine whether the result of the AND operation is non-zero. If so, there are multicast members downstream of the current interface, and it is necessary to forward a copy of the multicast traffic to the interface with a non-zero result of the AND operation, and make the result of the OR of the service multicast string forwarded by each interface a subset of or the same as the service multicast string in the received multicast traffic.

9. The protocol-independent satellite network multicast method according to claim 8, characterized in that: When forwarding the multicast traffic, the satellite modifies the service multicast character string in the multicast service extension header to an AND operation result; if the flag bit corresponding to the satellite in the service multicast character string is set, the flag bit is set to 0 during forwarding.

10. The protocol-independent satellite network multicast method according to claim 1, characterized in that: When the satellite network topology changes, each satellite recalculates the unicast routing table and updates the bit index forwarding table. When the multicast traffic arrives subsequently, the traffic is forwarded according to the new bit index forwarding table.

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