KR20040028046A - Packet transfer method in Multi Protocol Label Switching Network between Non-Multi Protocol Label Switching Network - Google Patents

Abstract

PURPOSE: A method is provided to reduce the size of the header of the multi-protocol label switching(MPLS) network packet passing through the boundary routers. CONSTITUTION: A method comprises a first step of permitting a plurality of boundary routers and a network address converting agent to be linked with each other and generate network address translation(NAT) tables; a second step of removing the label from the header and making a request on the converted address corresponding to the destination address to the network address converting agent, when a first boundary router has received the MPLS packet to pass through a non-MPLS network; a third step of permitting the network address converting agent to search the address matched to the destination address of the MPLS packet by using the NAT table and provide the searched address to the first boundary router; a fourth step of permitting the first boundary router to convert the source and destination addresses of the MPLS packet into the address matched to the non-MPLS network and transmit the converted address to a second boundary router through the non-MPLS network; a fifth step of permitting the second boundary router to make a request on the original address corresponding to the converted address of the source of the MPLS packet to the network address converting agent; a sixth step of permitting the network address converting agent to search the original address by using the NAT table and provide the searched address to the second boundary router; and a seventh step of permitting the second boundary router to substitute the source and destination addresses of the MPLS packet with the original address, adding a label to an IP header, and transmitting the packet with the added label to the final destination address.

Description

Packet transfer method between MPL and non-MPLS network {Packet transfer method in Multi Protocol Label Switching Network between Non-Multi Protocol Label Switching Network}

According to the present invention, a packet of an MPLS network is referred to as a non-MPLS network in a multiprotocol label switching network (MPLS) and a non-multiprotocol label switching network (hereinafter referred to as a non-MPLS network). The present invention relates to a packet forwarding method in a boundary router connecting the MPLS network to a non-MPLS network.

The MPLS network is a proven standard technique for speeding up and managing the traffic flow of a network, and is involved in establishing a specific path for a given packet sequence, and each packet in the MPLS network has a label to enter a router. Has a feature that saves the time it takes to see the address of the node to which the packet should be delivered. Hereinafter, the MPLS network will be briefly described with reference to FIG. 1.

1 is a structure and delivery diagram of a packet in a general MPLS network.

In FIG. 1, one service provider network (N1, MPLS network) includes a plurality of service provider routers 10 and a plurality of service receiving routers that provide services to a plurality of customers belonging to the service provider network N1. (11a to 11c, PE0 to PE2, Provider Edge), a plurality of subscriber receiving routers (12a to 12e, CE0 to CE5, Customer Edge) for delivering services to the subgroup of the lower network, and between each of the PEs It includes a LSR (Label Switching Router, not shown) that locates and inspects a labeled packet and changes its value to deliver the packet along a predetermined path. The CE may be one host or switch or router, and the PE may be a router or the like. In addition, it further includes a host (13a, 13b) connected to the subscriber receiving router.

Hereinafter, throughout the detailed description, the service provider network is described as N, the service provider router as P, the service receiving router as PE, and the subscriber receiving router as CE.

The host 13a connected to the CE1 12a adds the source address and the destination address to the header of the packet to the CE1. When forwarding the packet, the CE1 forwards the packet to PE0 11a, which is the next hop to the destination address.

The source address is 10.1.2.1 (virtual IP in the MPLS network), which is the address of the host connected to CE1, and the destination address is the final destination address of the packet delivered by CE1, which is the host 13b connected to CE5 12e. The address is 10.1.1.1 (virtual IP).

The PE0 11a analyzes the header of the packet received from CE1, determines the LSP (Label Switched Path) connected to the final destination address and the final destination of the packet, and changes the header so that the packet is passed by label switching. Deliver the packet to the next router on the LSP. Like the PE0, a PE that first receives a host packet and delivers the packet to a destination is called an ingress LER (label edge router).

When the header of the packet is changed in the PE0, the label of the CE5 12e as the destination and the router's label to be delivered after the PE0 are identified through the label forwarding table and attached to the back of the IP header. It can be seen that the label corresponding to CE5 in the header of the packet is '12' and the next router is '200'. The label forwarding table is stored for each PE and consists of label information matched to each router and host.

The packet forwarded by PE0 is forwarded to the next router on one preset LSP, and the router that receives the packet is changed to the label included in the header, that is, the label of the router to be forwarded to the next router. By the label switching operation performed by the router on the LSP, the packet is delivered to the PE2 11c.

The PE2 11c analyzes the header information of the received packet, determines the next destination to be delivered, and then delivers the packet to the CE5 12e. Like this PE2, the PE that delivers the packet to the final destination is called an egress LER.

As described above, in the MPLS network, the MPLS packet can be delivered to another destination by label switching.

However, when the packet transmitted through the MPLS network goes to the destination via the non-MPLS network as well as the MPLS network as described above, the method of encapsulating the label into the header as in the MPLS network is not applied in other networks. Therefore, there is a problem that the structure and delivery method of the packet is incompatible.

In order to solve the above problems, conventionally, when delivering a packet to a non-MPLS network, the method as shown in FIG.

2 is a diagram illustrating the structure and delivery of a packet in an IP encapsulation scheme in an MPLS network and a non-MPLS network according to a conventional method.

In FIG. 2, PE1 (21a, hereinafter referred to as a border PE such as a border PE) located at the boundary between an MPLS network and a non-MPLS network is a representative IP address of a router that accommodates a destination host and a router that accommodates a source host. Replace the representative IP address with the label of the next hop. Through such a label, packet header information can be decoded in an IP based router.

That is, when the host 23a connected to CE1 22a attaches the source address and the destination address to the header of the packet as shown in FIG. 2, the CE1 delivers the packet to PE1 21a as the next hop. The source address is 147.6.72.64, the IP address of the host connected to CE1, and the final destination address is 163.239.1.17, the IP address of the host connected to CE9 (22i).

The PE1 21a recognizes the label of the destination CE9 22i and the label of the next hop PE1 through a label forwarding table and attaches it to the back of the IP header.

As described above, the packet delivered by PE1 is delivered to routers 20b and P2 on one preset LSP, and P2 20b receiving the packet is a label included in a header, that is, routers 21c and PE3 of the next hop. ) And change it to the next hop, PE3 (21c). Packets are delivered by label switching performed by these routers on the LSP.

The PE3 21c is a boundary router connecting the N1 network and the N2 network. The PE3 analyzes the header of the received packet, and instead of the label of the next hop, the IP of the PE5 21e which is the boundary router between the N2 network and the N3 network to go to the N3 network to which its own address and the final destination CE9 (22i) belong. Add an IP header containing the address to make an IP packet and pass it to N2 network.

As shown in the drawing, the packet is delivered to PE5 via P3 (20c), P4 (20d), P5 (20e), and PE4 (21d) of N2 network, which is a non-MPLS network, using IP header information. do.

After receiving the packet, PE5 removes the IP header added from PE3, and then finds the label of the next hop, P6 (20f), in the label forwarding table and adds it to the packet to get to the final destination, CE9. Delivered to P6, delivered to CE9 via PE621f, and delivered to host 23b, the final destination.

This conventional method adds an IP header to an MPLS packet received from an MPLS network and delivers it to another network via a non-MPLS network, but the router receiving the packet adds its own address and destination address to the IP header. Since there is a need to increase the size of the packet, there is a problem that greatly degrades the performance of the network.

An object of the present invention for solving the problems of the prior art as described above is that the edge routers connecting the MPLS network and the non-MPLS network provide NAT table information to the network address translation agent, so that the edge router provides address information of another network. The present invention provides a method of transmitting a packet received by referring to a NAT table of a network address translation agent to another network without increasing the header size.

1 is a diagram illustrating a structure and delivery of a packet in a general MPLS network;

2 is a diagram illustrating the structure and delivery of a packet of an IP encapsulation scheme in an MPLS network and a non-MPLS network according to a conventional method;

3 is a diagram illustrating the structure and delivery of packets in an MPLS network and a non-MPLS network according to the present invention;

4 is an exemplary diagram of a NAT table in FIG. 3;

5 is an exemplary diagram of a routing table in FIG. 3;

6 is a flow chart illustrating a packet forwarding in FIG. 3;

7 is a NAT table generation diagram in a border router according to the present invention.

※ Explanation of code about main part of drawing ※

30a to 30f: service provider router

31a to 31f: service acceptance routers

32a to 32i: subscriber accept router

33a, 33b: host

34: NAT agent

In order to achieve the above object, the present invention stores an MPLS network including a plurality of CEs and a plurality of PEs, a non-MPLS network, a plurality of boundary routers located at the boundary between the MPLS network and the non-MPLS network, and NAT table information. A packet forwarding method in a mixed MPLS network and a non-MPLS network using a network address translation agent, wherein, when the first edge router receives the MPLS packet through the non-MPLS network, the header label is removed and the network is removed. A first step of requesting a translation address corresponding to a destination address from an address translation agent, and the network address translation agent finds a translation address matching the destination address of the MPLS packet using the NAT table to the first border router. Providing a second step, and the first boundary router converts the source and destination addresses of the MPLS packet into a translation address corresponding to a non-MPLS network. A third step of delivering to the second border router via the spare MPLS network; and a fourth request of the network address translation agent for a source address corresponding to the translation address of the source address of the MPLS packet by the second border router; Step 5, wherein the network address translation agent finds a source address matching the translation address of the source address using the NAT table, and provides the source address to the second border router; And replacing a source and a destination address with a source address, adding a label to the IP header, and delivering the final destination address.

Hereinafter, a packet forwarding method between an MPLS network and a non-MPLS network according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram illustrating the structure and delivery of packets in an MPLS network and a non-MPLS network according to the present invention.

In FIG. 3, networks N1 and N3 are MPLS networks, and network N2 is a non-MPLS network. The first MPLS network N1 includes two service provider routers P1 30a and P2 30b, a plurality of service receiving routers PE1 to PE3 31a to 31c, and a plurality of subscriber routers CE1 to CE4. 32a to 32d) and a plurality of general routers (not shown) located between respective PEs to form an LSP between the routers. The CE1 32a includes a host 33a at the bottom.

The second MPLS network N3 includes a server provider router P6 (30f), a plurality of service receiving routers (PE5 (31e) and a PE6 (31f)), and a plurality of subscriber receiving routers (CE7 to CE9 (32g to). 32i)) and general routers (not shown) forming the LSP. In addition, the CE9 includes a host 33b at the bottom.

In addition, the non-MPLS network N2 is an IP-based network and includes a service provider router (P3 to P5 (30c to 30e), a plurality of subscriber receiving routers (PE3 (31c), PE4 (31d)) and a plurality of subscriber routers. (CE5 (32e), CE6 (32f)) and general routers (not shown) forming the LSP.

In the host 33a below the CE1 32a belonging to the MPLS network N1, the process of transferring the packet in the MPLS network N1 to another MPLS network N3 via the non-MPLS network N2 is performed. The process of transferring the MPLS packet to the host 33b under the CE9 32i belonging to another MPLS network will be described in detail.

In FIG. 3, source hosts 33a connected to CE1 32a of MPLS network N1 have a subnet mask of 147.6.72.0/25, and destination hosts connected to CE9 32i of another MPLS network N3. 33b has a subnet mask of 163.239.1.0/24.

When the source host generates an IP packet having a header of a source address and a destination address [147.6.72.64, 163.239.1.17], and delivers the packet to the destination host, the packet is forwarded to CE1, its receiving router. CE1 forwards it to the next hop, PE1 31a.

The PE1 receiving the IP packet reads the header of the received packet to determine the final destination 33b of the packet and the LSP connected to the final destination, and uses CE9 (32i) as a destination router using the label forwarding table stored in the PE1. A header for the prefix address (12 in the header of the packet), followed by a label for the next hop (100 in the header of the packet) to the next hop (P2, 30b). Creates and delivers MPLS packet with header of [100, 12, 147.6.72.64, 163.239.1.17].

The P2 30b receiving the MPLS packet transfers the received MPLS packet to the next hop (PE3, 31c) on the LSP preset by the label switching operation of P2. [200, 12, 147.6.72.64, 163.239.1.17] Create and deliver an MPLS packet with a header. The label of the packet is switched by the router so that the packet transmitted from the source host 33a is delivered to PE3 located at the boundary of the non-MPLS network.

When the PE3 31c receives the MPLS packet from the P2, the PE3 31c refers to a NAT table (Network Address Translation Table) of the network address translation agent 34 for a destination address among the header information of the received MPLS packet, Determine that the destination is via a non-MPLS network.

Accordingly, the header of the MPLS packet is unlabeled, the source address of the MPLS packet header is replaced with 10.1.1.64, which is a translation address of the source address by referring to the NAT table owned by the MPLS packet, and the NAT agent is replaced with the destination address of the MPLS packet. Return the corresponding translation address 20.1.1.17 and replace it with the destination address, and then apply NAT to the next hop (P3, 30c) of PE5 (31e) of the non-MPLS network (N2) of [10.1.1.64, 20.1.1.17]. Pass the packet with the header.

The translation addresses of the NAT tables of PE3 and PE5, which are boundary routers between the different networks, have a certain prefix provided by a network address translation agent. The PE3 and PE5 communicate with each other to exchange routing information and prefix information. In addition, address information belonging to another network is requested by the network address translation agent and returned.

In accordance with the above exchange of address information, boundary routers use the prefix to perform a routing operation to a forwarding destination of a packet. Due to the operation of the router, the PE3 may determine the header information of the packet transmitted from the P2, remove the label, and replace the source / destination address with the translation address.

The NAT-applied packet transmitted by the PE3 is delivered to the PE5 31e via P3 to P5 (30c to 30e) belonging to the non-MPLS network.

The PE5 checks the received packet to see if it is an MPLS packet, and if it is a NAT-applied packet transmitted from another MPLS network via a non-MPLS network, the PE5 uses its NAT table as a destination address in the header of the NAT converted packet. Reference is read as an IP address, the source address is requested by the network address translation agent, returned, read as an IP address, and converted into a source address (147.6.72.64, 163.239.1.17). Then, the label 12 for the destination address and the label 300 of the next hop to be passed to the destination address are attached to the header of the NAT converted packet in the form of MPLS packet header [300, 12, 147.6.72.64, 163.239 .1.17] and transfer to the relevant LSP.

The MPLS packet is delivered by the router on the corresponding LSP to a packet having a header [147.6.72.64, 163.239.1.17] in the original packet form to the PE6 (31f) which is the destination PE, and the PE6 is attached to the information contained in the packet header. The MPLS packet is forwarded to CE9 32i. Finally, the destination host 33b receives the original packet.

4 is an exemplary diagram of NAT tables stored in PE3, PE5, and a network address translation agent in FIG. The fields of the NAT table of the PE3, PE5 and the network address translation agent are composed of a source address and a translation address thereof.

Referring to FIG. 3, boundary PEs PE3 and PE5 located at the interface between the MPLS network and the non-MPLS network generate a NAT table using the routing table shown in FIG. 3, and generate a NAT table for each network. After creating, pass NAT table information to the network address translation agent.

FIG. 5 is an exemplary diagram of a routing table stored in the boundary PEs PE3 and PE5 in FIG. 3.

As shown in FIG. 5, the routing table stored in each boundary PE has to go through the source address of the plurality of PEs, CEs, Ps (certified IP addresses) and the protocols to which the address information is transmitted, and the routing to the addresses. Information about the next hops to be included.

6 is a flowchart illustrating a packet processing in FIG. 3.

In FIG. 6, each router exchanges registration information with other routers belonging to the same network, and among the routers, boundary routers connecting the MPLS network and the non-MPLS network convert network registration information from their NAT table. Deliver to agent. (S600)

The network address translation agent stores the registration information of the border routers in its NAT table.

After completing the initialization operation of step S600, the boundary router reads whether it is an MPLS packet with header information of the received packet (S601).

If the received packet is an MPLS packet, the boundary router reads the destination address by referring to the NAT table of the network address translation agent and its NAT table, and reads whether the MPLS packet passes through the non-MPLS network (S602).

If the border router has to deliver the MPLS packet via a non-MPLS network, remove the label of the MPLS packet. Then, the network address translation agent requests a translation address of the destination address of the MPLS packet header and returns it, replaces the source address with the translation address by referring to its own NAT table, and replaces the destination address with the returned translation address. Convert to NAT-applied packets (S603 to S605).

If the MPLS packet is received through the non-MPLS network, the packet is transferred to the next hop without changing the header value (S612).

The border router forwards the NAT-applied packet to the next hop, and the next hop forwards the packet to another border router via hops belonging to a non-MPLS network (S606 and S607).

When the border router receives the NAT-applied packet of step S607 or receives a non-MPLS packet, the border router refers to the network address translation agent and its NAT table to read whether the received packet has been translated (S608). )

When the border router receives a NAT translated packet, it requests the source address of the translated source address from the network address translation agent and returns it. Subsequently, the translated destination address is replaced with the source address by referring to its own NAT table, and the converted source address is replaced with the original IP address returned. In addition, a label is added to the header converted into an IP packet to convert and generate the MPLS packet. (S609 to S611)

If the edge router does not receive a NAT-applied packet, that is, receives an IP packet, it adds only a label to the header of the IP packet (S611).

The boundary router delivers the generated MPLS packet to the next hop and delivers the MPLS packet to the router to which the final destination belongs via other hops of the MPLS network (S613).

The final router removes only the label from the header of the MPLS packet and delivers it to the final destination in the form of an original packet (S614).

7 is a flowchart illustrating a NAT table generation in a boundary PE according to the present invention. Since the NAT table generation process of FIG. 7 is the same in all boundary PEs, only a process of generating a NAT table in one boundary PE will be described.

In FIG. 7, when one network (hereinafter, referred to as a service provider network) connected to another network is registered, the boundary PE connecting the service provider network and another service provider network receives a representative prefix of the translation address from the network address translation agent. Request and receive it. (S700 ~ S701)

The boundary PE received the representative prefix reads a routing table owned by the representative prefix and selects one of the addresses delivered by the Internet Group Protocol (IGP) from the contents recorded in the routing table (S702).

The boundary PE that selects the one address determines the translation address for the edge router by creating unique addresses as many as the number of hosts of the edge router (CE) in the prefix of the translation address.

After determining the translation address, the boundary PE creates and inserts a record in its NAT table to record the address selected in step S702 in the source address field, and then converts the translation address determined in step S603 to correspond to the translation address field. (S704 ~ S705)

In steps S703 to S704, a method of determining and assigning a translation address for a source address is as follows. The boundary PE is allocated to the representative prefix of the translation address as many as the number of hosts of the addresses selected in the routing table. At this time, it does not conflict with an existing translation address recorded in the network address translation agent.

After the boundary PE records the source address and the translation address in its NAT table, the boundary PE transfers the information (record) of its NAT table to the network address translation agent (S706).

The network address translation agent receiving the information of the NAT table of the boundary PE adds and records records of the NAT table of the boundary PE to its NAT table (S707).

After that, when a packet having a source address and a destination address is delivered to the boundary PE, the boundary PE refers to its NAT table and the NAT table of the network address translation agent and forwards the packet to the next hop (router) to the destination. To be delivered.

Through the above process, a NAT table is generated in all boundary PEs connecting the MPLS network and the non-MPLS network, and the operation is performed. The generated NAT table is stored in each boundary PE and simultaneously transferred to the network address translation agent. It is also stored by the network address translation agent. Each boundary PE maintains a translation address for its source address in the NAT table, and the network address translation agent stores translation address information for all source addresses in the NAT table.

Referring to FIG. 3, a case of PE3 31c, which is a boundary PE belonging to the MPLS network N1 having a process of generating the NAT table and transmitting the same to the NAT agent, will be described as an example.

When the MPLS network N1, which is a service provider network, is registered in connection with the non-MPLS network N2 and the MPLS network N3, which are other service provider networks, the PE3 31c requests a representative prefix from a NAT agent to the NAT agent. A representative prefix of 10.0.0.0/8 is allocated from 34, and the PE3 selects a random IP address based on its own routing table.

When the PE selects an arbitrary address 147.6.67.0/25, PE3 writes 147.6.67.0/25 to the source address of the NAT table and assigns 10.1.1.0/25 as the translation address for this address. Record this translation address in the translation address field of the NAT table.

After determining the source address and the translation address, PE3 records the addresses in a record of its NAT table.

If PE3 selects another source address in the routing table, 61.78.53.17/28, records this address in the source address field of the NAT table, assigns 10.1.1.128/28 as the translation address for this address, and then Record in the translation address field of the NAT table.

As mentioned above, PE3 communicates with other routers through IGP, completes the NAT table after learning about all IP addresses, and delivers the information of its NAT table to the NAT agent.

Although the present invention has been described above based on the preferred embodiments, these examples are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all such changes, modifications or adjustments.

As described above, according to the present invention, the network address translation agent stores the information of the boundary routers connecting the MPLS network and the non-MPLS network in its NAT table, and the boundary router uses the NAT table information of itself and the network address translation agent. By replacing the source / destination address of the MPLS packet header received from the MPLS network with the NAT-translated address, and passing it to the other MPLS network via the routers of the non-MPLS network, the size of the header of the MPLS packet passing through the boundary routers is reduced. It works.

Claims (5)

MPLS network including a plurality of CEs and a plurality of PEs connected to each host of the user side, a non-MPLS network, a plurality of boundary routers located at the boundary between the MPLS network and the non-MPLS network, and the plurality of boundary routers via a non-MPLS network. In a packet forwarding method in a network in which an MPLS network and a non-MPLS network using a network address translation agent that provides address information can be mixed, A first step of the plurality of border routers and the network address translation agent interworking with each other to generate their own NAT tables; When the first border router receives the MPLS packet through the non-MPLS network, removing a label of the header and requesting a translation address corresponding to a destination address from the network address translation agent; A third step of the network address translation agent finding a translation address matching the destination address of the MPLS packet by using the NAT table and providing it to the first border router; A fourth step of the first boundary router converting the source and destination addresses of the MPLS packet into a translation address corresponding to the non-MPLS network and transmitting the converted address to a second border router via the non-MPLS network; Requesting, by the second border router, the network address translation agent for a source address corresponding to a translation address of the source address of the MPLS packet; A sixth step of the network address translation agent finding a source address matching the translation address of the source address using the NAT table and providing the source address to the second border router; And And a seventh step in which the second boundary router replaces the source and destination addresses of the MPLS packet with a source address, adds a label to the IP header, and delivers the final destination address to the MPLS network. Packet forwarding method. The method according to claim 1, NAT table of the plurality of border routers, And a mapping table for source addresses of all hosts in the MPLS network to which the host belongs and a translation address corresponding to the source addresses. The method according to claim 2, NAT table of the network address translation agent, And a NAT table in which all NAT table information stored in each of all the edge routers is collected. The method according to claim 1, The first step, Requesting, by each edge router, a representative prefix for a translation address from the network address translation agent; Providing, by the network address translation agent, representative prefixes for different translation addresses to the respective boundary routers; Generating, by each of the edge routers, a translation address corresponding to a source address of hosts belonging to the MPLS network to which the boundary routers belong by using a representative prefix provided from the network address translation agent and storing the translation address in a NAT table; And generating, by the network address translation agent, NAT table information of each of the boundary routers to generate its own NAT table. On your computer, A first step in which a plurality of border routers and network address translation agents cooperate with each other to generate their own NAT tables; When the first border router receives the MPLS packet through the non-MPLS network, removing a label of the header and requesting a translation address corresponding to a destination address from the network address translation agent; A third step of the network address translation agent finding a translation address matching the destination address of the MPLS packet by using the NAT table and providing it to the first border router; A fourth step of the first boundary router converting the source and destination addresses of the MPLS packet into a translation address corresponding to the non-MPLS network and transmitting the converted address to a second border router via the non-MPLS network; Requesting, by the second border router, the network address translation agent for a source address corresponding to a translation address of the source address of the MPLS packet; A sixth step of the network address translation agent finding a source address matching the translation address of the source address using the NAT table and providing the source address to the second border router; And A computer-readable program having a program capable of executing the seventh step of replacing, by the second boundary router, the source and destination addresses of the MPLS packet with a source address and adding a label to the IP header to a final destination address. Record carrier.