Network device, system and method based on multi-link transmission

Abstract

The invention discloses a network device, system and method based on multi-link transmission, and relates to the field of network data transmission, and the network device comprises a multi-link creation module which is used for creating a plurality of independent links; the connection module is used for establishing connection between the network devices; the sending module is used for segmenting to-be-sent data into a plurality of data packets when the data are sent, endowing each data packet with a serial number, and sending all the data packets through each link; and the receiving module is used for splicing the data packets sent by each link according to the serial numbers of the data packets when receiving the data packets sent by all the links to obtain the received data of the link. According to the invention, the communication quality of network equipment can be effectively improved, the network fluctuation is reduced, the overall transmission delay is reduced, and the data transmission reliability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of network data transmission, and in particular to a network device, system and method based on multi-link transmission. Background Art

[0002] There are many existing network data transmission technologies. The more mature data transmission methods include: combined transmission and parallel transmission. During the network data transmission process, network fluctuations may occur. Commonly used network protocols include: IP (Internet Protocol), TCP (Transmission Control Protocol), UDP (User Datagram Protocol), and KCP, which are explained below.

[0003] Combined transmission: It is a data transmission method that combines the bandwidth of multiple channels. The specific steps include:

[0004] At the sending end, the data to be transmitted is divided into multiple parts and transmitted through different channels;

[0005] At the receiving end, the received multiple parts are reassembled together to increase the transmission speed.

[0006] Combined transmission is suitable for data transmission that requires large bandwidth, such as high-definition video, large files, etc.

[0007] Parallel transmission: The data to be transmitted is transmitted in groups on multiple parallel channels at the same time. Multiple data bits are transmitted between devices at the same time. Parallel transmission is only suitable for short distances and occasions that require fast transmission speeds.

[0008] Network fluctuations: When a large number of users use the network at the same time, if the network bandwidth is insufficient, it will lead to increased latency; when the data traffic in the network is too large, if the network equipment has insufficient processing capacity, it will also cause network congestion; if the network routing node fails, the network will also fluctuate.

[0009] IP is the network layer protocol in the TCP / IP system. The purpose of designing IP is to improve the scalability of the network:

[0010] First, it solves Internet problems and realizes the interconnection and interoperability of large-scale, heterogeneous networks;

[0011] The second is to separate the coupling relationship between top-level network applications and underlying network technologies to facilitate the independent development of the two.

[0012] Based on the end-to-end design principle, IP only provides a connectionless, unreliable, best-effort data packet transmission service for the host.

[0013] In practical applications, the IP protocol is generally used together with the TCP protocol and the UDP protocol.

[0014] TCP: A connection-oriented, reliable, byte-stream-based transport layer communication protocol defined by RFC (Request For Comments, a series of numbered documents) 793 of the IETF (Internet Engineering Task Force).

[0015] TCP is designed to fit into a hierarchy of layered protocols that support multi-network applications, where pairs of processes in host computers connected to different but interconnected networks rely on TCP for reliable communications services. TCP assumes that it can get simple, potentially unreliable datagram services from lower-level protocols. In principle, TCP can be applied to a variety of communication systems, from hard-wired connections to packet-switched or circuit-switched networks.

[0016] UDP is a datagram mode that provides packet switching computer communication in a group of interconnected computer network environments. The protocol assumes the use of IP as the underlying protocol and works at the transport layer according to the OSI (Open System Interconnect) model. UDP provides a process for applications to send messages to other programs with minimal protocol mechanisms. The protocol is transaction-oriented and does not guarantee delivery and duplicate protection. The UDP protocol supports multicast, multicast, and broadcast, and can send data packets to multiple network devices at the same time.

[0017] The KCP protocol is a reliable transport layer ARQ (Automatic Repeat Request) protocol. KCP is a fast and reliable protocol that can reduce the average delay by 30% to 40% and the maximum delay by three times at the cost of wasting 10%-20% of the bandwidth compared to TCP. It is a pure algorithm implementation and is not responsible for the sending and receiving of the underlying protocol. The user needs to define the sending method of the underlying data packet and provide it to KCP in the form of callback. KCP generally uses UDP as the underlying sending and receiving protocol.

[0018] With the rapid development of the Internet in recent years, various Internet applications have emerged in large numbers, and remote Internet communications have penetrated into all aspects of people's lives. Some Internet applications have very high requirements for real-time communication, such as telemedicine, remote intervention for autonomous driving, etc. These Internet applications require the information transmission delay to be as low as possible. However, network transmission may experience network fluctuations, causing increased latency in a short period of time, which poses a great challenge to the reliability of these applications.

[0019] At present, in scenarios with high latency requirements, different processing methods can be selected according to the two different requirements of allowing packet loss and requiring reliable transmission:

[0020] (1) In scenarios where latency requirements are high and packet loss is tolerated, the UDP protocol is used, and the application is tolerant of packet loss and disorder.

[0021] (2) In scenarios where latency requirements are high and reliable transmission is required, use the TCP protocol or the KCP protocol.

[0022] However, if the first processing method mentioned above is used, when network fluctuations occur, data packets will be lost or data packet delay will increase, affecting the device interaction experience; if the second processing method mentioned above is used, when network fluctuations occur, the lost data packets will be retransmitted, but packet loss will lead to retransmission, which will inevitably increase the data packet delay. Therefore, neither of the above two processing methods can solve the problem of increased latency caused by the decline in network link communication quality. Summary of the invention

[0023] In view of the defects existing in the prior art, the purpose of the present invention is to provide a network device, system and method based on multi-link transmission, which can effectively improve the communication quality of network equipment, reduce network fluctuations, reduce overall transmission delay, and improve the reliability of data transmission.

[0024] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0025] In a first aspect, the present application provides a network device based on multi-link transmission, including:

[0026] A multi-link creation module is used to: create multiple independent links;

[0027] Connection module: used to establish connections between network devices;

[0028] The sending module is used to: when sending data, divide the data to be sent into multiple data packets, assign a sequence number to each data packet, and send all data packets through each link;

[0029] The receiving module is used to: when receiving data packets sent from all links, splice the data packets sent from each link according to the sequence number of the data packets to obtain the received data of the link.

[0030] Based on the network device described in the first aspect, the connection module is specifically used to:

[0031] Connecting to an external network device, sending a handshake message through multiple links, the handshake message carrying a unique connection identifier; and

[0032] Receive handshake messages sent by external network devices through multiple links, combine multiple links with the same handshake messages into one logical connection, and reply with handshake confirmation;

[0033] After receiving the partial handshake confirmation, it is confirmed that the connection with the external network device is successful.

[0034] In a second aspect, the present application provides a system based on multi-link transmission, including a sending device and a receiving device, all of which have the functions of the network device described in the first aspect:

[0035] The sending device is used to: create multiple independent links and establish connections between network devices; when sending data, divide the data to be sent into multiple data packets, assign a sequence number to each data packet, and send all data packets through each link;

[0036] The receiving device is used to: create multiple independent links and establish connections between network devices; when receiving data packets sent by all links, splice the data packets sent by each link according to the sequence number of the data packets to obtain the received data of the link.

[0037] Based on the system described in the second aspect, the connection between network devices is established, and the specific connection process includes:

[0038] Connecting to an external network device, sending a handshake message through multiple links, the handshake message carrying a unique connection identifier; and

[0039] Receive handshake messages sent by external network devices through multiple links, combine multiple links with the same handshake messages into one logical connection, and reply with handshake confirmation;

[0040] After receiving the partial handshake confirmation, it is confirmed that the connection with the external network device is successful.

[0041] In a third aspect, the present application provides a network device connection method applied in the system described in the second aspect, comprising the following steps:

[0042] The receiving device creates multiple independent link servers, monitors multiple links, and waits for connections;

[0043] The sending device creates multiple independent link clients, connects to multiple links of the receiving device, and sends handshake messages through the multiple links. The handshake messages carry a unique connection identifier.

[0044] The receiving device receives the handshake message sent by the sending device through multiple links, combines the multiple links with the same handshake message into one logical connection, and replies with a handshake confirmation;

[0045] After the sending device receives the partial handshake confirmation, it confirms that the connection with the receiving device is successful.

[0046] In a fourth aspect, the present application provides a multi-link transmission method based on the network device connection method according to the third aspect, comprising the following steps:

[0047] After the sending device is successfully connected to the receiving device, it sends data to the receiving device through multiple links. When sending data, the service data unit SDU is packaged or sub-packaged to generate a protocol data unit PDU. Each PDU is assigned an increasing sequence number, and the PDU also contains a unique connection identifier. The sending device sends the PDU through multiple links;

[0048] After receiving the PDU sent from a certain link, the receiving device extracts the sequence number and the unique connection identifier, obtains the associated logical connection through the unique connection identifier, and passes the PDU to the logical connection for processing; the receiving device receives the PDU from the link with the fastest transmission speed among multiple links;

[0049] The logical connection of the receiving device performs deduplication and sorting after receiving the PDU, and then divides and combines the PDU into SDU, which is then passed to the business layer for processing.

[0050] Based on the multi-link transmission method described in the fourth aspect, the following steps are also included:

[0051] When the receiving device wants to send data, it finds multiple associated connections through the unique connection identifier of the logical connection and sends the data to the sending device through these connections.

[0052] Based on the multi-link transmission method described in the fourth aspect, the following steps are also included:

[0053] After receiving the data, the receiving device replies with an ACK to confirm receipt through each connection; after receiving the ACK, the sending device clears the sending queue of each connection and removes expired sent data.

[0054] Based on the multi-link transmission method described in the fourth aspect, the following steps are also included:

[0055] If there is no data transmission between the sending device and the receiving device for a long time, heartbeat packets will be sent to each other.

[0056] Based on the multi-link transmission method described in the fourth aspect, the following steps are also included:

[0057] When either the sending device or the receiving device wants to disconnect, it sends a disconnect message to each link and then disconnects each link; after the other party receives the disconnect message, it also disconnects each link.

[0058] Compared with the prior art, the advantages of the present invention are:

[0059] (1) The present invention equips interconnected devices with multiple independent links for communication and uses multiple links for redundant transmission. Even if network fluctuations occur simultaneously on multiple links, as long as one link is transmitting normally, network communication between interconnected devices can proceed normally, thus avoiding the degradation of overall communication quality caused by network jitter of a single link, effectively improving the communication quality of network devices, reducing network fluctuations, and reducing overall transmission delay.

[0060] (2) The present invention uses data link redundancy to avoid the situation where network fluctuations in a single data link cause increased data transmission delays in network devices. Multiple independent links are used for data transmission. Increased data transmission delays occur only when network fluctuations occur in all data links at the same time. Compared with transmission using a single data link, redundant transmission using multiple links has higher reliability.

[0061] (3) The technical solution of the present invention is scalable and can be used not only for traditional network protocols but also for various private network protocols and new communication methods to be introduced in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0063] Figure 1 This is an architecture diagram of a network device based on multi-link transmission in an embodiment of the present invention;

[0064] Figure 2 is a flow chart of a network device connection method according to an embodiment of the present invention;

[0065] Figure 3 The figure is a flow chart of a multi-link-based data transmission method in an embodiment of the present invention. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0067] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0068] Embodiment 1: Network device based on multi-link transmission

[0069] See also Figure 1 As shown, in order to solve the problem of increased latency caused by decreased communication quality of network links, an embodiment of the present invention provides a network device based on multi-link transmission, including:

[0070] A multi-link creation module is used to: create multiple independent links;

[0071] Connection module: used to establish connections between network devices;

[0072] The sending module is used to: when sending data, divide the data to be sent into multiple data packets, assign a sequence number to each data packet, and send all data packets through each link;

[0073] The receiving module is used to: when receiving data packets sent from all links, splice the data packets sent from each link according to the sequence number of the data packets to obtain the received data of the link.

[0074] The above connection module is specifically used for:

[0075] Connecting to an external network device, sending a handshake message through multiple links, the handshake message carrying a unique connection identifier; and

[0076] Receive handshake messages sent by external network devices through multiple links, combine multiple links with the same handshake messages into one logical connection, and reply with handshake confirmation;

[0077] After receiving the partial handshake confirmation, it is confirmed that the connection with the external network device is successful.

[0078] Embodiment 2: System based on multi-link transmission

[0079] Based on the above network device, an embodiment of the present invention provides a system based on multi-link transmission, including a sending device and a receiving device, all of which have the functions of the above network device, wherein:

[0080] The sending device is used to: create multiple independent links and establish connections between network devices; when sending data, divide the data to be sent into multiple data packets, assign a sequence number to each data packet, and send all data packets through each link;

[0081] The receiving device is used to: create multiple independent links and establish connections between network devices; when receiving data packets sent by all links, splice the data packets sent by each link according to the sequence number of the data packets to obtain the received data of the link.

[0082] The above-mentioned connection between network devices is established, and the specific connection process includes:

[0083] Connecting to an external network device, sending a handshake message through multiple links, the handshake message carrying a unique connection identifier; and

[0084] Receive handshake messages sent by external network devices through multiple links, combine multiple links with the same handshake messages into one logical connection, and reply with handshake confirmation;

[0085] After receiving the partial handshake confirmation, it is confirmed that the connection with the external network device is successful.

[0086] The embodiment of the present invention assumes that all network devices participating in the communication have multi-link capabilities, and each data link provides a function similar to the UDP protocol for sending and receiving data packets.

[0087] The network device mentioned in the embodiment of the present invention has a network module inside, and can create multiple independent network links. Each network link provides a message sending mechanism similar to UDP and only supports unicast.

[0088] The network links do not interfere with each other, that is, the network fluctuation of each network link is an independent event.

[0089] In order to achieve two-way communication, there is at least one link that can send data and at least one link that can receive data. When more than one link can send and receive data, the reliability of the network can be improved.

[0090] Embodiment 3: Network device connection method

[0091] The embodiment of the present invention assumes that each network link can send and receive data, and takes unidirectional data transmission as an example for detailed description. The sending device can create a client, and the receiving device can create a server.

[0092] See also Figure 2 As shown, an embodiment of the present invention provides a network device connection method applied in the above-mentioned system based on multi-link transmission, comprising the following steps:

[0093] Step 101: The receiving device creates a server end of multiple independent links, monitors multiple links, and waits for the client to connect;

[0094] Step 102: The sending device is connected to multiple links of the receiving device, and sends a handshake message through the multiple links. The handshake message carries a unique connection identifier, and waits for handshake confirmation.

[0095] Step 103: The receiving device receives the handshake message sent by the sending device from multiple links of the client, combines multiple links with the same handshake message into one logical connection, and replies with a handshake confirmation;

[0096] Step 104: After the sending device receives the partial handshake confirmation, it can be confirmed that the sending device is successfully connected to the receiving device.

[0097] Embodiment 4: Multi-link transmission method

[0098] See also Figure 3 As shown, an embodiment of the present invention further provides a multi-link transmission method based on the above network device connection method, comprising the following steps:

[0099] Step 201: After the sending device is successfully connected to the receiving device, data is sent to the receiving device through multiple links. When sending data, the SDU (Service Data Unit) is packaged or sub-packaged to generate a PDU (Protocol Data Unit). The purpose of package combination is to reduce the number of transmissions, and the purpose of sub-package is to ensure that the length of the PDU meets the MTU (Maximum Transmission Unit) limit of each link. Each PDU is assigned an increasing sequence number, and the PDU also contains a unique connection identifier. The sending device sends the PDU through multiple links;

[0100] Step 202: After receiving the PDU sent from a certain link, the receiving device extracts the sequence number and the unique connection identifier, obtains the associated logical connection through the unique connection identifier, and transmits the PDU to the logical connection for processing; the receiving device receives the PDU from the link with the fastest transmission among multiple links. If the fastest link changes due to network jitter, the receiving device will always receive data from the link with the fastest transmission among multiple links;

[0101] Step 203: After receiving the PDU, the logical connection of the receiving device performs deduplication and sorting, and divides and combines the PDU into SDUs, and passes them upward to the service layer for processing.

[0102] In practical applications, it is important to note that:

[0103] (1) When the receiving device needs to send data, it can find multiple associated connections through the unique connection identifier of the logical connection and send data to the sending device through these connections;

[0104] (2) After receiving the data, the receiving device replies with an ACK (acknowledgement of receipt) through each connection. After receiving the ACK, the sending device clears the sending queue of each connection and removes the expired sent data.

[0105] (3) During the transmission process of the sending device, some links may be disconnected, and these links can be reconnected;

[0106] (4) If no data is received for a long time, the connection of each link can be considered disconnected. If each link of the logical connection is disconnected, the logical connection can be considered disconnected.

[0107] (5) If there is no data transmission between the sending device and the receiving device for a long time, heartbeat packets can be sent to each other;

[0108] (6) When either the sending device or the receiving device needs to disconnect, it sends a disconnect message to each link and then disconnects each link. After the other party receives the disconnect message, it also disconnects each link.

[0109] (7) If the service allows packet loss, after receiving the data packets, duplicate and expired data packets can be removed.

[0110] (8) If the service requires reliable transmission, both parties need to maintain the send and receive windows, and multiple data links reply ACK to confirm receipt; KCP can also be connected over multiple links to achieve reliable transmission.

[0111] The embodiments of the present invention can avoid the degradation of communication quality caused by the jitter of a single link network by establishing multiple independent links for communication, and ensure the communication quality by link redundancy, which can effectively improve the communication quality of network devices, reduce network fluctuations, and reduce the overall transmission time. The reliability of communication can be increased by adding more data links between network devices.

[0112] Although the use of multiple independent links for transmission will increase hardware and communication costs, in some very critical business scenarios, the increase in costs can be tolerated to ensure communication quality.

[0113] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the advantages or disadvantages of the embodiments.

[0114] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0115] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0116] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; the “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0117] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0118] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0119] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A network device based on multi-link transmission, characterized in that: include: A multi-link creation module is used to: create multiple independent links; Connect the module: Used to: establish connections between network devices; The sending module is used to: when sending data, divide the data to be sent into multiple data packets, assign a sequence number to each data packet, and send all data packets through each link; The receiving module is used to: when receiving data packets sent from all links, splice the data packets sent from each link according to the sequence number of the data packets to obtain the received data of the link.

2. The network device according to claim 1, characterized in that: The connection module is specifically used for: Connecting to an external network device, sending a handshake message through multiple links, the handshake message carrying a unique connection identifier; and Receive handshake messages sent by external network devices through multiple links, combine multiple links with the same handshake messages into one logical connection, and reply with handshake confirmation; After receiving the partial handshake confirmation, it is confirmed that the connection with the external network device is successful.

3. A system based on multi-link transmission, comprising a sending device and a receiving device, characterized in that: All sending devices and receiving devices have the functions of the network device described in claim 1: The sending device is used to: create multiple independent links and establish connections between network devices; when sending data, divide the data to be sent into multiple data packets, assign a sequence number to each data packet, and send all data packets through each link; The receiving device is used to: create multiple independent links and establish connections between network devices; when receiving data packets sent by all links, splice the data packets sent by each link according to the sequence number of the data packets to obtain the received data of the link.

4. The system according to claim 3, characterized in that: The specific connection process of establishing a connection between network devices includes: Connecting to an external network device, sending a handshake message through multiple links, the handshake message carrying a unique connection identifier; and Receive handshake messages sent by external network devices through multiple links, combine multiple links with the same handshake messages into one logical connection, and reply with handshake confirmation; After receiving the partial handshake confirmation, it is confirmed that the connection with the external network device is successful.

5. A network device connection method used in the system of claim 3, characterized in that: The following steps are involved: The receiving device creates multiple independent link servers, monitors multiple links, and waits for connections; The sending device creates multiple independent link clients, connects to multiple links of the receiving device, and sends handshake messages through the multiple links. The handshake messages carry a unique connection identifier. The receiving device receives the handshake message sent by the sending device through multiple links, combines the multiple links with the same handshake message into one logical connection, and replies with a handshake confirmation; After the sending device receives the partial handshake confirmation, it confirms that the connection with the receiving device is successful.

6. A multi-link transmission method based on the network device connection method of claim 5, characterized in that: The following steps are involved: After the sending device is successfully connected to the receiving device, it sends data to the receiving device through multiple links. When sending data, the service data unit SDU is packaged or sub-packaged to generate a protocol data unit PDU. Each PDU is assigned an increasing sequence number, and the PDU also contains a unique connection identifier. The sending device sends the PDU through multiple links; After receiving the PDU sent from a certain link, the receiving device extracts the sequence number and the unique connection identifier, obtains the associated logical connection through the unique connection identifier, and passes the PDU to the logical connection for processing; the receiving device receives the PDU from the link with the fastest transmission speed among multiple links; The logical connection of the receiving device performs deduplication and sorting after receiving the PDU, and then divides and combines the PDU into SDU, which is then passed to the business layer for processing.

7. The multi-link transmission method according to claim 6, characterized in that: The following steps are also included: When the receiving device wants to send data, it finds multiple associated connections through the unique connection identifier of the logical connection and sends the data to the sending device through these connections.

8. The multi-link transmission method according to claim 7, characterized in that: The following steps are also included: After receiving the data, the receiving device replies with an ACK to confirm receipt through each connection; after receiving the ACK, the sending device clears the sending queue of each connection and removes expired sent data.

9. The multi-link transmission method according to claim 7, characterized in that: The following steps are also included: If there is no data transmission between the sending device and the receiving device for a long time, heartbeat packets will be sent to each other.

10. The multi-link transmission method according to claim 7, characterized in that: The following steps are also included: When either the sending device or the receiving device wants to disconnect, it sends a disconnect message to each link and then disconnects each link; after the other party receives the disconnect message, it also disconnects each link.

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