WO2010037291A1 - Routing method and router in hierarchical and sequential address packet network - Google Patents

Abstract

A routing method and router in Hierarchical and Sequential Address Packet Network (HSAPN) is disclosed. In the method, the current router node receives the message to be forwarded and obtains the HSAPN address of the destination router node from the message; the current router node judges whether the HSAPN address of the destination router node and its own HSAPN address are the same; if yes, it ends the routing of the message; if no, it determines, according to routing rules and a routing table, a next-hop directly-connected neighbor router node and routes the message to the next-hop directly-connected neighbor router node.

Description

 Method and router for routing in hierarchical ordered address packet network This application claims a method for establishing a routing table in the hierarchically ordered address packet network submitted to the Chinese Patent Office on September 27, 2008, with the application number 200810216519.8 and the invention name Priority of the Chinese Patent Application, the method of routing, and the entire disclosure of the entire disclosure of which is incorporated herein by reference.

Technical field

 The present invention relates to the field of communications, and in particular, to a method and a router for routing in a Hierarchical and Sequential Address Packet (HSAP) network.

Background technique

 With the development of technology, the telecommunication network has successfully completed the first step from analog technology to digital technology, and the second step of TDM (Time-Division Multiplexing) technology to packet switching technology is underway. ATM (Asynchronous Transfer Mode) packet technology is the representative of this transition phase. However, due to the difficulty of ATM packet technology and the unsuccessful commercial operation, the second step of the TDM technology from packet-switched technology to Telecommunication technology has not been realized. .

 In the early 1990s, the Internet based on IP (Internet Protocol, IP protocol) packet technology was extremely successful due to the application of Web technology, and rapidly expanded into a global network that can compete with the telecommunication network, and gradually turned to telecommunications. Business extension. Therefore, the telecommunication network introduced IP packet technology and loaded all telecommunication services on the IP network, and it is expected to realize the transition from TDM technology to packet technology. However, because the design concept of the Internet is a free and non-profit business model, the Internet based on IP packet technology is a free and open packet network without unified management mechanism, which also causes the Internet to be insecure, untrustworthy, lack of management and The lack of quality of service and other issues, so that many important commercial service networks and data security services and real-time video services with high quality of service requirements cannot be safely loaded onto the public IP network. Therefore, IP packet technology cannot be used. The transition from TDM technology to packet technology.

Therefore, a Hierarchical Ordered Address Packet HSAPN network is proposed. The HSAPN network is a packet network used for telecommunication purposes. It is used to carry all existing telecommunication services and can guarantee the telecommunication services it carries. The same quality of service for telecommunication services. In addition, it can also carry the interconnection The network service provides the same capabilities as the existing Internet, supports all existing Internet services, and can also be used to carry other services that may arise in the future. The HSAPN network adopts hierarchical and orderly coding and hierarchical routing. Therefore, a certain path can be determined according to the address. However, there is no complete routing table establishment method and corresponding routing method in the current HSAPN network. The current routing table needs to provide the whole routing table. The routing information of the router nodes in the network is large, and all of them are implemented by static manual configuration. The configuration is complex and error-prone.

Summary of the invention

 The embodiment of the invention provides a method and a router for routing in an HSAPN network. The router node in the HSAPN network only needs to obtain the link state information of the directly connected neighboring router node, and determine the route according to the link state information of the directly connected neighboring router node. path.

 A method for routing a route in an HSAPN network according to an embodiment of the present invention includes: receiving, by a current router node, a packet that needs to be forwarded, and obtaining an HSAPN address of the destination router node from the packet; Whether the HSAPN address of the destination router node is the same as the HSAPN address of the current router node, and if yes, the routing of the packet is ended. If not, the next hop is determined according to the routing rule and the routing table. Connect to the neighbor router node and route to the next hop directly connected neighbor router node.

 A router in a layered and ordered address HSAPN network, which is further provided by the embodiment of the present invention, includes a receiving unit, configured to receive an advertisement packet sent by a directly connected neighboring router node, where the advertisement packet carries the packet Link state information of the router node; establishing unit: establishing a routing table according to the link state information of the directly connected neighboring router node received by the receiving unit; and selecting a unit, configured to determine the next hop direct connection according to the routing rule and the routing table Neighbor router node, and routes to the next hop directly connected neighbor router node.

In the embodiment of the present invention, the link state information of the router node directly connected to the neighbor is obtained by transmitting the link state advertisement message between the directly connected neighboring router nodes in the HSAPN network, and only needs to obtain the link state information according to the obtained The link state information of the neighboring router node is directly generated to generate a routing table, and the routing table is searched according to the routing rule to forward the packet. The router node in the HSAPN network only needs to obtain the link state information of the directly connected neighboring router node. That is, the current router node only needs to know how to route to the next hop router node according to the routing rule, and does not need to acquire the chain of the router node of the entire network. The road status information determines the routing path of the entire network, which not only reduces the configuration information of the routing table, but also simplifies the current The complexity of the router node.

DRAWINGS

 1 is a schematic diagram of an HSAPN architecture according to an embodiment of the present invention;

 2 is a schematic diagram of hierarchical hierarchical addressing of an HSAPN network according to an embodiment of the present invention;

 3 is a schematic diagram of a state of an HSAPN network port according to an embodiment of the present invention;

 4 is a schematic diagram of a routing method in an HSAPN according to an embodiment of the present invention;

 5 is a schematic diagram of a data packet routing method in an HSAPN according to an embodiment of the present invention;

 6 is a schematic diagram of a routing method when data packets are forwarded to the downstream in the HSAPN according to the embodiment of the present invention;

 FIG. 7 is a schematic structural diagram of a router in an HSAPN according to an embodiment of the present invention.

detailed description

 The embodiments of the present invention provide a method and a router for routing in an HSAPN network, and a preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings.

 As shown in Figure 1, the HSAPN architecture includes at least one HSAPN network, a plurality of IP networks, an ATM network or an FR (Frame Relay) network, and a plurality of EDs (Edge Devices), each of which is HSAPN. The network also includes at least one ADT (Address Translation Entity). The service network of the HSAPN network may be an IP network, an ATM network, or a FR network. Since the IP network is currently the most widely used network, the following mainly describes the IP network as an example. In the HSAPN architecture shown in Figure 1, the IP network is connected to the HSAPN network through the ED device. All devices and ED devices in the HSAPN network are assigned HSAPN addresses. All devices and ED devices in the IP network are assigned. The mapping between the IP address, HSAPN address and IP address is stored in the address mapping table in the ADT.

 The HSAPN address is addressed in a hierarchical manner according to the carrier and the area. The address is hierarchical and ordered. The HSAPN network can obtain a certain path according to the address. As shown in FIG. 2, the HSAPN network routing system is in the embodiment of the present invention. The HSAPN network system uses four levels as an example. The encoding format and length of each level are in a binary/hexadecimal encoding format, but are not limited thereto. According to the situation, the HSAPN network system can also be divided into five levels, six levels, etc. The encoding format and length of each level are also set according to the situation. It is recommended to use the binary encoding format.

Referring to FIG. 1 and referring to FIG. 2, in the embodiment of the present invention, A, B, C, and D are addressing forms of HSAPN addresses, and A, B, C, and D respectively represent different network layers, that is, A represents Nuclear Heart area (country domain, level 1), B represents the aggregation domain (provincial domain, level 2), C represents the access domain (city-level domain, level 3), and D represents the boundary domain (gateway domain, level 4) ). In the HSAPN network, the network level of the router, that is, the address allocation rule, can be determined according to the HSAPN address. For example: From A1.0.0.0, the router can be known to be in the first-level (top-level) A1 domain, from A1.B2. 0.0 can know that the router is in the secondary A1.B2 domain, from A1.B2.C3.0 can know that the router is in the third-level A1.B2.C3 domain, from A1.B2.C3.D1 can know that the router is in the fourth level (lowest level). For the address ABCD, different levels of router HSAPN network addresses have their corresponding network level address masks, for example: The network level address mask of the core domain address A1.0.0.0 is Fx xxR0.0.0, and the aggregation domain address A1. The network level address mask of B2.0.0 is Fx X xRFxx xRO.O, and the network level address mask of access domain address Al.B2.C3.0 is Fx xxF.FxxxF.Fxx xF.O, boundary domain address A1. The network level address mask for B2.C3.D1 is FRF RF RF xF.

 The embodiments of the present invention are based on the HSAPN network, and the neighboring router nodes in the HSAPN network send advertisement packets to each other to perform neighbor dynamic discovery and link state information acquisition. Each router obtains direct connection with the router node. The link state information of the parent node router, the child node router, and the peer node router dynamically generates a routing table. Of course, the routing table can also be statically configured through manual planning. At the same time, the routing rule can be defined whether the routing table is dynamically generated or the routing table is statically generated. The routing table is searched according to the routing rule to forward data packets.

 Referring to FIG. 4, specifically, the routing method in the HSAPN network provided by the embodiment of the present invention includes:

 101: The neighbor router node dynamically discovers and directly obtains link state information of the neighbor router node;

In an embodiment of the present invention, the HSAPN router node includes at least one port, and the HSAPN router node sends an advertisement packet from all its own ports, and the advertisement message is used for dynamically discovering and advertising link state information of the neighboring router node. In the embodiment of the invention, the advertisement message uses a Hello data packet. If two routers share a common data link and can successfully negotiate with each other some of the parameters specified in their respective Hello data messages, they become direct neighbors. The Hello data packet carries information related to the link state. The specific link state information parameter includes the HSAPN address, the port number, and the network level address mask of the router. The Hello data packet also carries information related to dynamic discovery of the neighbor. Specific neighbor dynamic discovery information parameters include Hello data packets. The information interval of the sending interval, the router invalid time, the neighbor, and the like, wherein the router invalid time refers to the maximum time interval (threshold value) from the start of the sending of the Hello data packet by the local node to the receipt of the response message sent by the peer neighbor. At the maximum time interval, the neighbor establishment failure is considered. The HSAPN router can also calculate the port state information parameters of each port based on the HSAPN address of the neighbor router port and its own HSAPN address carried in the Hello data packet received from the directly connected neighboring router. The port status is used to identify the port. Each port of the router is an uplink port (parent port), a downlink port (child port), or a peer port. The specific calculation method is as follows:

 For example, as shown in FIG. 3, the HSAPN address of the router A is Al.Bl.Cl.O, and there are three ports 1, 2, and 3, and the HSAPN of the router B carried in the Hello data packet received from the port 1 is received. The address A1.B1.0.0, compared with its own HSAPN address Al.Bl.Cl.O, can be judged according to the address allocation rule, A1.B1.0.0 is the parent address of Al.Bl.Cl.O, ie It can be known that port 1 of router A is an uplink port; similarly, according to the HSAPN address A1.B1.C2.0 of router C carried in the Hello data packet received from port 2, and its own HSAPN address Al.Bl. Compared with Cl.O, according to the address allocation rule, it can be judged that A1.B1.C2.0 and Al.Bl.Cl.O are addresses of the same network level, and it can be known that port 2 of router A is a peer port; According to the HSAPN address A1.B1.C1.D1 of the router D carried in the Hello data packet received from the port 3, compared with the HSAPN address Al.Bl.Cl.O of the own, the address allocation rule can be determined according to the address allocation rule. , A1.B1.C1.D1 is the child address of Al.Bl.Cl.O, and it can be known that port 3 of router A is the downlink port.

 The Hello data packet is transmitted only one hop between the neighboring nodes. The status information of the HSAPN router node is only advertised between the neighboring nodes and is not flooded.

 102: Establish a routing table according to link state information of the neighboring router.

 As shown in Table 1, the routing table is established based on the link state information parameters carried in the Hello data packet sent by the directly connected neighbor router node and the calculated port state information parameters. The routing table is established based on the neighbor router HSAPN address in the link and port status information and the port number of the local router connected to it.

The routing table may further include information for setting a priority level to the router nodes in the HSAPN network according to the situation, and is used to identify the priority of the router node routes in the same level (such as primary, secondary, tertiary, and tertiary). In the embodiment of the present invention, the priority level may be determined by using a potential energy level, the potential energy level is high, the priority level is high, the potential energy level is low, and the priority is low, that is, during the forwarding process, According to the message, the packet is preferentially forwarded from the current router node to the peer router node with the high potential level. The potential level can be set uniformly according to the network plan. If the potential energy level is high, it is preferred, the primary route, and the potential energy level is low, and the primary route is faulty, and the secondary route is optional.

Table 1

103: Perform routing of data packets according to routing rules and routing tables.

 The routing rule provided by the embodiment of the present invention is a routing rule for routing and forwarding of the current HSAPN router node, and each HSAPN router node performs the data packet routing and forwarding according to the HSAPN address of the current router node and the HSAPN address and route of the destination router node. Rules, look up the routing table, and determine the forwarding path.

 If the HSAPN address of the destination router node is the same as the HSAPN address of the current router node, the packet does not need to be routed, that is, the data packet has been delivered to the destination router node.

 If the HSAPN address of the destination router node is different from the HSAPN address of the current router node, but the HSAPN address of the destination router node is the same as the HSAPN address of the current router node, the data packet is sent from the downlink port to the next level. Router node forwarding;

 If the HSAPN address of the destination router node is different from the HSAPN address of the current router node, and the HSAPN address of the destination router node is different from the HSAPN address of the current router node where the data packet is located, the text is up from the uplink port. The primary router node routes or the peer routes in the router node where the current level is located according to the priority level.

 Take the 4-level HSAPN network as an example. Referring to Figure 5, the route of the HSAPN router node at the i-th level (i = l, 2, 3, 4) is as follows:

 103a: The i-th current router node receives the data packet to be forwarded, and the packet header of the data packet carries the HSAPN address of the source router node and the HSAPN address of the destination router node, and the current router node resolves the destination router node. HSAPN address;

103b: Compare the HSAPN address of the destination router node with the HSAPN address of the current router node Whether the addresses are the same, if the same, indicating that the data packet has been routed to the destination router node, the data packet routing process ends, if not, proceed to the next step 103c;

 103c: Compare whether the HSAPN address of the destination router node at the current level (i-th level) is the same as the HSAPN address of the current router node. If they are the same, the downlink port from the current router node is down to the first level (1+1th level) router. Node routing, if different, proceeds to the next step 103d;

 In this step, referring to FIG. 6, routing from the downlink port of the current router node to the next level (1+1th level) router node further includes: determining whether the current router node has only a unique downlink port, and if so, Routing from the only downstream port to the next-level router node. If not, the (1 + 1)-level HSAPN address of the destination address is compared with the HSAPN address of each downlink port, and the HSAPN address with the same comparison result value is corresponding. The downstream port is routed to the next level router node.

 103d: Compare the HSAPN address of the destination router node with the HSAPN address of the current router node at the upper level (i-1 level) of the current level. If the same, the data is based on the potential energy level at the current level. The peer forwarding in the router node is forwarded from the upstream port of the current router node to the upstream router node.

 As shown in FIG. 7, an embodiment of the present invention provides a router in a hierarchical and ordered address network, including:

 The advertisement packet generating unit is configured to generate an advertisement packet, where the advertisement packet is used for the neighbor dynamic discovery and the advertisement of the link state. In the embodiment of the present invention, the advertisement packet uses a Hello data packet; The packet is sent to the directly connected neighboring router node, and the packet may be an advertisement packet or a data packet generated by the advertisement packet generating unit, where the advertisement packet carries the link state information of the own router node, and the data packet The HSAPN address carrying the active router node and the destination router node;

 The receiving unit is configured to receive the packet sent by the directly connected neighboring router node, where the packet may be an advertisement packet or a data packet, and the receiving unit may obtain the link state information of the directly connected neighboring router node from the advertisement packet, Obtain the HSAPN address of the destination router node in the data packet;

 a routing table establishing and storing unit: configured to establish a routing table according to link state information of the directly connected neighboring router node received by the receiving unit, and store the routing table;

The determining unit further includes a first determining unit, a second determining unit, a third determining unit, and a fourth determining unit, wherein The first determining unit is configured to determine, after the current router node receives the data packet, whether the HSAPN address of the destination router node is the same as the HSAPN address of the current router node;

 The second determining unit is configured to determine whether the HSAPN address of the current router node at the current level is the same as the HSAPN address of the current router node;

 The third determining unit is configured to determine whether the HSAPN address of the destination router node is the same as the HSAPN address of the current router node at the current level;

 The fourth determining unit is configured to determine whether the current router node has a unique downlink port.

 a selecting unit, configured to search the routing table according to the routing rule, determine a next hop directly connected neighbor router node, and perform routing to the next hop direct neighbor router node, where the method further includes a first selecting unit, a second selection unit, a third selection unit, and a fourth selection unit, wherein the first selection unit is configured to: when the first determination unit determines that the result is yes (the destination router node

When the HSAPN address is the same as the HSAPN address of the current router node, the local processing is performed to end the routing of the data packet. When the first judgment unit determines that the result is no (the HSAPN address of the destination router node and the HSAPN address of the current router node are not When the same), the second determining unit is enabled;

 The second selecting unit is configured to select to enable the third determining unit or the fourth determining unit according to the determining result of the second determining unit, that is, when the determining result of the second determining unit is yes (the destination router node is at the current level of the HSAPN address and current When the HSAPN address of the router node is the same, the second selection unit selects to enable the third determining unit, and when the second determining unit determines No (the destination router node is different from the HSAPN address of the current router node in the current level) The second selection unit selects to enable the fourth determining unit;

 The third selecting unit is configured to: when the third determining unit determines that the HSAPN address of the destination router node is the same as the HSAPN address of the current router node at the current level of the current level, select the peer router node to forward the datagram according to the potential energy level. For example, when the third determining unit determines No (the HSAPN address of the destination router node is different from the HSAPN address of the current router node at the current level), the uplink port from the current router is selected to be routed to the first-level router node;

The fourth selecting unit is configured to: when the fourth determining unit determines that it is (having a unique downlink port), select to route from a unique downlink port, and when the fourth determining unit determines to be no (having multiple downlink ports), select The downlink port that is the same as the (i + 1)-level HSAPN address of the destination address is routed to the next-level router node. A person skilled in the art may understand that all or part of the steps in the method of implementing the above embodiments may be completed by a program to instruct a related forwarding plane, and the program may be stored in a computer readable storage medium, and the storage medium may be ROM/RAM, disk or CD, etc.

 The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

Claims

Rights request  A method for layering an ordered address grouping route in an HSAPN network, comprising:  The current router node receives the packet to be forwarded, and obtains the HSAPN address of the destination router node from the packet;  Determining whether the HSAPN address of the destination router node is the same as the HSAPN address of the current router node,  If the HSAPN address of the destination router node is the same as the HSAPN address of the current router node, the routing of the packet is ended.  If the destination router node has an HSAPN address with the current router node If the HSAPN addresses are different, the next hop directly connected neighbor router node is determined according to the routing rule and the routing table, and the packet is routed to the next hop directly connected neighbor router node.  2. The method of routing in an HSAPN network according to claim 1, further comprising:  Discovering neighbors and obtaining link state information of directly connected neighbor router nodes;  And establishing the routing table according to link state information of the directly connected neighbor router node.  The method for routing in an HSAPN network according to claim 2, wherein the discovering the neighbor and obtaining the link state information of the directly connected neighboring router node includes:  The current router node discovers the neighbor by directly transmitting the advertisement packet sent by the neighboring router node, and obtains the link state information of the directly connected neighbor router node.  The method of routing in an HSAPN network according to claim 3, wherein the current router node discovers a neighbor by directly transmitting an advertisement message sent by the neighboring router node, and acquires a directly connected neighbor router node. After the link status information, it also includes:  Obtaining, by the current router node, an HSAPN address of the directly connected neighboring router node according to link state information of the directly connected neighboring router node, by using an HSAPN address of the current router node and an HSAPN address of the directly connected neighboring router node Comparing, calculating port state information parameters of the current router node. The method for routing a route in an HSAPN network according to claim 4, wherein the calculating a port state information parameter of the current router node is specifically: If the HSAPN address of the current router node is the parent address of the HSAPN address of the directly connected neighboring router node, the current router node receives the port of the advertisement message sent by the directly connected neighboring router node as a downlink port;  If the HSAPN address of the current router node is a peer address of the HSAPN address of the directly connected neighboring router node, the current router node receives the port of the notification message sent by the directly connected neighboring router node as a peer Port  If the HSAPN address of the current router node is a child address of the HSAPN address of the directly connected neighboring router node, the current router node receives the port of the advertisement message sent by the directly connected neighboring router node as an uplink port.  The method of routing in the HSAPN network according to claim 2, wherein the routing table further includes priority information of the router node in the HSAPN network, and the priority level is identified by a potential energy level.  The method of routing in an HSAPN network according to claim 1, wherein the determining, according to the routing rule and the routing table, determining a next hop direct neighbor router node, and forwarding the packet to the next Skip directly to neighbor router nodes for routing, including:  Further determining whether the destination router node has the same HSAPN address of the current level as the HSAPN address of the current router node;  If the destination router node has the same HSAPN address of the current level as the HSAPN address of the current router node, routing the message from the downlink port to the next-level router node; if the destination router node is at the current level The HSAPN address is different from the HSAPN address of the current router node, and the 4艮 text is routed from the uplink port to the first-level router node, or is routed in the current-level router node according to the priority level.  The method of routing the HSAPN network according to claim 7, wherein the routing the packet from the downlink port to the next-level router node comprises:  Further determining whether the current router node has only a unique downlink port;  If there is only a unique downlink port, routing from the unique downlink port to the next-level router node; If there is not only a unique downlink port, the HSAPN address of the destination router node is compared with the HSAPN address of each downlink port of the current router node in the next-level HSAPN address. The downlink port corresponding to the HSAPN address with the same result value is routed to the next-level router node. The method of routing in an HSAPN network according to claim 7, wherein the message is routed from an uplink port to a first-level router node, or is routed in a current-level router node according to a priority level, Specifically include:  Further determining an HSAPN address of the destination router node and the current router node Whether the HSAPN address of the HSAPN address is the same as the HSAPN address of the upper level of the current level;  If the HSAPN address of the destination router node is the same as the HSAPN address of the current router node in the upper level of the current level, the packet is forwarded in the current level router node according to the priority level;  If the destination router node has an HSAPN address with the current router node The HSAPN address is different from the HSAPN address of the upper level of the current level, and the message is forwarded from the uplink port of the current router node to the first-level router node.  A router in a hierarchically-ordered address HSAPN network, comprising: a receiving unit, configured to receive a packet sent by a directly connected neighboring router node, where the packet includes an advertisement packet and a data packet, Obtaining link state information of the directly connected neighbor router node from the advertisement packet;  a routing table establishing and storing unit, configured to establish a routing table according to the link state information of the directly connected neighboring router node acquired by the receiving unit, and store the routing table;  And a selecting unit, configured to determine, according to the routing rule and the routing table, a next hop direct neighbor router node, and route the received data to the next hop directly connected neighbor router node.  The router in the HSAPN network of claim 10, wherein the router further comprises:  An advertisement packet generating unit, configured to generate an advertisement packet;  a sending unit, configured to send a packet to the directly connected neighboring router node, where the packet is a data packet or an advertisement packet generated by the advertisement packet generating unit, where the advertisement packet carries the router node itself Link state information, the data packet carries the HSAPN address of the destination router node; The receiving unit is further configured to obtain an HSAPN address of the destination router node from the received data packet. The router in the HSAPN network according to claim 11, wherein the router further comprises: a determining unit, wherein the determining unit comprises a first determining unit, a second determining unit, a third determining unit, and a fourth Judging unit, wherein  The first determining unit is configured to determine, after the router node receives the data packet, whether the HSAPN address of the destination router node is the same as the HSAPN address of the router node; Determining whether the destination router node has the same HSAPN address at the current level as the HSAPN address of the router node;  The third determining unit is configured to determine whether an HSAPN address of the destination router node is the same as an HSAPN address of the router node at a higher level of the current level;  The fourth determining unit is configured to determine whether the router node has a unique downlink port. The router in the HSAPN network according to claim 12, wherein the router further comprises: a selecting unit, wherein the selecting unit comprises a first selecting unit, a second selecting unit, a third selecting unit, and a fourth Select unit, where  The first selecting unit is configured to enable the second determining unit when the first determining unit determines that the result is negative;  The second selecting unit is configured to select to enable the third determining unit or the fourth determining unit according to the determining result of the second determining unit;  The third selecting unit is configured to: when the third determining unit determines to be YES, select a peer router node to forward the data according to the priority level, and when the third determining unit determines to be no, select the current router. The uplink port is routed to the upper-level router node;  And the fourth selecting unit is configured to: when the fourth determining unit determines to be no, select a downlink port that is the same as the HSAPN address of the destination router node in the next level of the current level to the next-level router node.