KR20000046358A - Method for assigning source address of internet protocol packet in router - Google Patents

Abstract

The present invention relates to a method for allocating a source address of an IP packet when transmitting an Internet Protocol (IP) packet of an intranet to the Internet or another intranet.

The method of the present invention comprises the steps of: forming a dynamic address translation (DAT) table comprising an ID for the sub-networks constituting the intranet and a default Internet Protocol (IP) address for Internet access; Obtaining a network ID (NID) from a destination address of a private IP packet to be transmitted; Obtaining a network ID (NID) from a destination IP address read from a dynamic address translation table; A fourth step of comparing the network ID (NID) of the private IP packet obtained in the second step with the network ID (NID) of the dynamic address translation (DAT) table obtained in the third step; A fifth step of allocating a source address of an IP packet to be transmitted to the assigned IP address in the intranet if the comparison result is matched in the fourth step; If the result of the comparison does not match, the next address of the dynamic address translation (DAT) table is read, and after step 3, the source IP address of the IP packet to be transmitted is returned to the default IP address. The step of assigning.

Therefore, according to the present invention, the same LAN system can be a subnetwork of different routing domains, and the same LAN system users can be simultaneously connected to the Internet and an intranet.

Description

Method of allocating source address of an IP packet in a router

The present invention relates to a method for allocating a source address of an IP packet when an Internet Protocol (IP) packet of an intranet is transmitted to the Internet or another intranet (or a subnet of an intranet).

The Internet, which has recently been exploding in usage, is widely known, and is an interworking network that is configured to transparently transmit information between various networks made of various technologies and devices using a protocol set called TCP / IP. .

On the other hand, there is a need to speed up communication with companies or suppliers in order to strengthen their competitiveness, and the intranet is widely used as a way to meet these needs. This intranet is an Internet-related technology that handles all the work in a specific organization such as a company or research institute.It is based on a network using TCP / IP. Is done in a browser. In other words, the Intranet is a concept opposite to the Internet. Unlike an Internet where all hosts communicate and exchange information transparently, the intranet is a system that shares information within a company using technology of the Internet within a company fence.

The Internet and the intranet may be connected through the firewall 130, as shown in FIG. Referring to FIG. 1, the intranet 110 internally restricts access from the outside by the firewall 130, and internally the database system 111, the web browsers 112 and 113, the MIS system 114, and the web server 115. Internet-based office environment, and the Internet 120 accepts their web browsers 122, 123, 125, 126 between a plurality of hosts (121, 124) to communicate transparently through the default IP address to the Internet. Doing.

As the use of the intranet increases, it is necessary to transmit an IP packet of the intranet (hereinafter referred to as a private IP packet) to the Internet or another intranet.In case of transmitting the IP packet to the Internet, the source address of the IP packet is transmitted to the authorized IP. If you set the address and send it to another intranet, you need to set the IP address assigned by the intranet.

However, the conventional address assignment (or translation) method converts an IP packet address of one private IP network (ie, an intranet) into an address belonging to one routing domain. In other words, the conventional technology converts a private IP address into a public IP address when the private IP packet is transmitted to the Internet, and thus, there is a problem in that it cannot support a private IP network that wants to simultaneously access an intranet and the Internet.

Accordingly, the present invention has been proposed to solve the above problems, the Internet that can properly assign the source address according to the destination address in the router routing the packet to be transmitted in the intranet (ie private IP network) The purpose is to provide a method for allocating a source address of a protocol packet.

In order to achieve the above object, the method of the present invention provides a dynamic address translation (DAT) table including an ID for the sub-networks constituting the intranet and a default Internet Protocol (IP) address for Internet access. Forming a first step; Obtaining a network ID (NID) from a destination address of a private IP packet to be transmitted; Obtaining a network ID (NID) from a destination IP address read from the DAT table; A fourth step of comparing the network ID (NID) of the private IP packet obtained in the second step with the network ID (NID) of the dynamic address translation (DAT) table obtained in the third step; A fifth step of allocating a source address of an IP packet to be transmitted to the allocated IP address in the intranet if the comparison result is matched in the fourth step; And if the result of the comparison does not match, read the next address of the DAT table and repeat the third and subsequent steps until the end of the DAT table is reached. It characterized in that it comprises the step of assigning to the default IP address.

1 is a view illustrating an intranet and the Internet;

2 is a configuration example of a network to which the present invention can be applied;

3 is a format of an Internet Protocol (IP) packet,

4 is an example of the decimal representation of an Internet IP address,

5 is a format according to the class of the Internet IP address,

6 is a flowchart of a source address allocation method according to the present invention.

* Explanation of symbols for main parts of the drawings

110: intranet 111: DBMS

112,114,122,123,125,126: web browser

114: MIS 115: Web Server

120: Internet 121,124: Host

210: Internet 220,230: Enterprise network

240: subnet 245: router

250: network

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a configuration example of a network to which the present invention can be applied, and FIG. 3 is a format of an Internet protocol packet.

Referring to FIG. 2, a plurality of enterprise networks (intranets 220 and 230), the Internet 210, and a subnet 240 are connected through a communication network (WAN) 250, and a router 245 is connected to the subnet 240. Each enterprise network 220 and 230 is connected and forms an intranet. The router 245 transmits the private IP packet to be transmitted to the network designated by the destination address.

As shown in FIG. 3, an IP packet transmitted from the Internet or an intranet has a length of 4 bytes (32 bits) horizontally and a length of a predetermined length, and is classified into a header and data. The header of an IP packet consists of version, Internet header length (IHL), service type, total length, identifier, flag, fragment offset, lifetime, protocol, header checksum, source address, destination address, option + padding, and data.

The version indicates the version number as 4 bits and the Internet header length IHL indicates the header length of the 32 bit word as 4 bits. The service type is 8 bits and defines reliability, priority, delay, and throughput. The full length is the length of the entire data unit, including the header in octets. The identifier is 16 bits, which defines the datagram along with the source address, the destination address, and the user protocol. The fragment offset indicates where the fragment belongs within the datagram. Indicates. The lifetime is measured by gateway absorption, and the protocol refers to the next level of protocol that accepts data fields at the destination.

The source and destination addresses are 32 bits each, coded in bits to define the network and the stations within the specified network. As shown in FIG. 4, the address format is converted to decimal by one byte, and then read and displayed by dividing by ".", Which is represented by "203.235.129.6" in FIG. Each IP address consists of a pair of {network id (NID), host id}, where the network ID (NID) is an identifier for the network, and the host ID is a network and host designation. The number of bits used in FIG. 5 is as shown in FIG. 5 according to the class of the IP address.

Referring to FIG. 5, IP addresses are classified into 5 grades of A, B, C, D, and E according to the first few bits (1 to 5 bits). That is, if the first bit of the IP address is '0', it is an IP address of class A. In this case, the first 1 byte is used for the network ID and the remaining 3 bytes are used for the host ID. Therefore, there are 128 class A networks from 0.x.x.x to 127.x.x.x, and each class A network address can have about 16 million hosts. If the first two bits of the IP address are "10", it is a class B address, where the first two bytes are the network ID and the remaining two bytes are used for the host ID. Thus, there are about 1600 network class B addresses from 128.0.x.x to 192.255.0.0, each of which can have 65,534 hosts.

If the first three bits of the IP address are "110", the first three bytes are used for the network ID and the remaining one byte is used for the host ID, with about 2 million C-class networks ranging from 193.0.0.x to 223.255.255.255. There are addresses, each of which can have 254 hosts. If the first 4 bits of the IP address are "1110", it is for multicast as a class D address. If the first 5 bits of the IP address is "11110", it is an undefined address as an E class address.

Some of these IP addresses are pre-assigned for special purposes, where 0 is reserved for the default route, 127 is reserved for the loopback address, and host IDs are assigned to all network addresses. "0" points to the network itself, and a host ID of 1 is used for broadcast.

In order to connect an institution's network to the Internet, a default IP address must be assigned. The IP address is managed in the InterNIC (Network Information Center) under the Internet Assigned Numbers Authority (IANA).

On the other hand, every host on the Internet is assigned a unique IP address, which needs to be given a meaningful name that is easier to remember than to remember and use these IP addresses. However, since an actual computer uses an IP address for communication, a mapping between a name and an IP address is necessary. For this purpose, a hierarchical domain name system is used. According to the domain name system, "203.235.129.9" described above is referred to as "h2o.hansol.co.kr".

6 is a flowchart of a method for allocating a source address according to the present invention. In the embodiment of the present invention, when a packet is transmitted from subnet 1 to the Internet or another subnet, the router reports the destination address of the private IP packet and the IP packet. Shows how to assign a source address.

In the method according to the present invention, a dynamic address translation (DAT) table is used for address translation. When converting a private IP address into a default IP address, the method is used together with an existing table (NAT or PAT). Here, "NAT" converts a private IP address into a one-to-one default IP address, and DAT selects one default IP address to be assigned to a private IP packet when there are multiple default IP addresses for address translation. Play a role.

As such, the operation address translation (DAT) table used in the present invention is shown in Table 1 below.

Destination IP Address Subnet mask Default IP address NSP port 165.133.0.0 255.255.0.0 165.133.50.5 xxx-xxxx-xxx .. .. .. .. default 255.255.0.0 120.150.8.9 yyy-xxxx-yyy

In Table 1, a destination IP address represents a destination to which an IP packet is to be transmitted, and a subnet mask is a mask value for extracting only a network ID (NID) from the destination IP address, and a default IP address of a private IP packet to go to the corresponding destination address is shown. Source address value. The NSP port represents the port to actually send the IP packet.

Referring to FIG. 6, in step 601, the LAN table is determined to determine whether the received private IP packet is an IP packet to be transmitted to the WAN. If it is determined in step 601 that the packet is to be transmitted to the WAN, a network ID is obtained by covering the submask from the destination IP address of the IP packet in step 602. That is, as described above, since the address is composed of the network ID and the host ID, only the network ID is obtained by covering the sub mask.

In step 603, a network ID is obtained by masking the IP address read from the DAT table. In step 604, the network ID obtained from the destination address of the IP packet is compared with the network ID obtained from the destination address of the DAT table.

If the comparison result is matched in step 604, in step 605, the source address of the private IP packet to be transmitted to the IP address allocated in the intranet is converted and transmitted to the NSP port. If it does not match in step 604, it is determined whether it is the end of the DAT table in step 606. If it is not the last time, the next IP address is read from the DAT table in step 607, and then the process goes to step 603.

If the determination result in step 606 is the last, since the packet goes to the Internet, the process proceeds to step 608, assigns a default IP address to the IP address to be transmitted, and then transmits it to the Internet.

As such, the present invention determines the default IP address to be used as the source IP address according to the destination IP address of the private IP packet. In other words, if the destination IP address of the private IP packet is the IP address of the server belonging to the intranet, the default IP address assigned by the intranet for translation of the source address of the private IP packet according to the present invention is used, and the destination of the private IP packet is used. If the IP address is a server on the Internet, the default IP address assigned by "ISP" is used for source address translation of the private IP packet.

As described above, according to the present invention, when a LAN using a private IP address is joined to two or more "NSPs", the same LAN system can be a subnetwork of a different routing domain and the same LAN system. This has the effect of allowing users to access the Internet and intranets at the same time.

Claims (2)

A first step of forming a dynamic address translation (DAT) table comprising an ID for the sub-networks constituting the intranet and a default Internet Protocol (IP) address for Internet access; Obtaining a network ID (NID) from a destination address of a private IP packet to be transmitted; Obtaining a network ID (NID) from a destination IP address read from the DAT table; A fourth step of comparing the network ID (NID) of the private IP packet obtained in the second step with the network ID (NID) of the dynamic address translation (DAT) table obtained in the third step; A fifth step of allocating a source address of an IP packet to be transmitted to the allocated IP address in the intranet if the comparison result is matched in the fourth step; And If the result of the comparison does not match, the next address of the DAT table is read, and after the third step, the source address of the IP packet to be transmitted is reached when the end of the DAT table is reached. A source address allocation method for Internet protocol packets in a router comprising assigning to a default IP address. 2. The method of claim 1, wherein the dynamic address translation table includes a destination IP address, a subnet mask, a default IP address, and an NSP port item.