KR100356952B1 - Translation Table Structure Method for Address and Port Translation in Remote Access Server - Google Patents

Abstract

The present invention relates to a method of configuring a translation table for address and port translation in a remote access server that can configure a separate translation table for each host channel of a local network connected to the Internet and allocate a range of global ports.

In the conventional address and port conversion method, the information about the IP address and port is recorded in one conversion table, and the conversion table is sequentially searched to convert the address and port of the received IP packet. There was a time-consuming problem.

According to the present invention, by creating a separate translation table for each host channel of a local network interworking with the Internet through a remote access server and allocating a range of ports, the translation table retrieval time for address and port translation can be shortened during IP packet transmission. Will be.

Description

Translation table structure method for address and port translation in remote access server

The present invention relates to a method of configuring a translation table for address and port translation in a remote access server, and more particularly, to configure a separate translation table for each host channel of a local network connected to the Internet and to allocate a range of ports. A method of configuring a translation table for address and port translation in a remote access server.

The protocol currently in charge of data delivery on the Internet is IPv4. The protocol has a 32-bit addressing scheme and can address each of about 4 billion hosts. However, due to the inefficient allocation of IP addresses, the emergence of the World Wide Web and the development of various services on the Internet, the IP address (Internet Protocol Address) is exponentially needed and the limited IP address is expected to be exhausted. do.

To solve this problem fundamentally, IPv6, a next-generation data transfer protocol having a 128-bit addressing scheme, has been proposed, but the transition from IPv4 to IPv6 is not progressing smoothly. Therefore, a network address translation method has been proposed to address the evolution of IPv6, which requires considerable time and effort, and the IP address depletion problem that occurs when IPv6 is not available in the market.

The network address translation method is used for interworking with a local network using a local IP and a global network (Internet), that is, each host of the local network communicates using the local IP, so that the host of the local network can be used. In order to communicate with hosts in global network, local IP must be converted to global IP by network address translation. The network address translation method creates a translation table in the form of a lookup table and references it.

The network address translation method used conventionally can be divided into two types. The first is Network Address Translation (NAT), which translates the IP address's source address (local IP) into a global IP address, and the second is an IP address and port translation, which translates not only IP addresses but also ports in the TCP layer. Port Translation; NAPT).

In the NAPT method, data flow is distinguished by a 'port' of a transmission control protocol (TCP) or a user datagram protocol (UDP) protocol, so that several local hosts can use a single global IP address simultaneously with different port numbers. The utilization of the address is excellent.

When the translator module is out-going, it records the source's local IP address and port in the conversion table, and when in-coming, it considers the destination's global IP address and port. That is, when outgoing, the translation table is searched by the local IP address and the local port of the source, and when the incoming is searched, the conversion table is searched by the global IP address and the local port of the destination.

1 is a conceptual diagram of a conventional IP address and port translation method.

For example, assume that host A 32 of the local network and X 42 of the global network communicate, and host B 34 of the local network and Y 44 of the global network communicate.

For data flow from host A 32 to host X 42, the global IP address (G) assigned to the local IP address (A) and local port number (100) of the host A 32 as the source, and global The port number 1000 is recorded in the conversion table. In addition, the Network Address Port Translator (NAPT) 20 also uses the local IP address and local IP address of the host B 34 as the source for data flow from the host B 34 to the host Y 44. The global IP address G may be assigned to the port number 200 by changing only the global port number 2000.

At incoming time, if you look up the translation table with destination global IP address G and global port number 2000 to transfer data from host Y 44 to host B 34, the local IP of host B 34 is retrieved. Since only the address and local port number (100) are retrieved, the data flow from host A (32) to host X (42) and data from host B (34) to host Y (44) even with the same global IP address (G). You can distinguish flows.

However, in the conventional address and port conversion method, the information about the IP address and port is recorded in one conversion table, and the table is sequentially searched to convert the address and port of the received IP packet. There was a time-consuming problem.

The present invention is to solve the problems described above, the purpose of which is to configure a conversion table as a global IP address and a global port corresponding to the local IP address and local port of the IP packet, a global port of a certain range for each host channel In order to reduce the retrieval time of the conversion table by configuring the conversion table by allocating a local IP address and a local port corresponding to each global port.

1 is a conceptual diagram of a conventional IP address and port translation method.

2 is a block diagram showing an Internet interworking structure of a local network host through RAS.

3 is a diagram illustrating a configuration of a conversion table according to the present invention.

4 is a flowchart illustrating a conversion table configuration and an IP packet transmission process according to the present invention.

* Description of the symbols for the main parts of the drawings *

200: RAS (Remote Access Server) 210: address and port translation unit

300: host A 400: host B

500: host C

Features of the present invention for achieving the above object, the process of receiving an IP packet from the address and port conversion unit provided in the remote access server to identify the host channel; Determining whether the IP packet is a TCP packet or a UDP packet; Determining whether the SYN flag bit of the TCP header is set in the IP packet when the IP packet is a TCP packet; Allocating a global port and an entry when the SYN flag bit of the TCP header is set as a result of the determination; Adding information about a global IP address, a global port, a local IP address, and a local IP port to the entry; Inserting the entry into a conversion table; Converting a local IP address and a local port into a global IP address and a global port; The present invention provides a method of allocating a port by an address and a port translation function in a remote access server, the method comprising performing a process for transmitting the IP packet to the Internet.

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

Configure the conversion table as a local IP address and a local port corresponding to the global IP address and global port of the IP packet, and allocate a range of global ports for each channel connected to the host, and then the local IP address and local corresponding to each global port. Configure the translation table by assigning ports.

In particular, a remote access server (hereinafter referred to as RAS), which allows remote computers to connect to each other by dial-up, X.25, or null modem cable, is connected to the Internet. If yes, dial-up networking users can access the Internet via RAS.

RAS also provides access to existing LAN environments through Dial-Up Networking. Computers dialed through RAS can run in the same environment as if they were directly connected to an existing LAN.

2 is a diagram illustrating an Internet interworking structure of a local network host through RAS.

The plurality of local network hosts 300, 400, and 500 interworking with the Internet through the RAS 200 have one channel connected to the RAS 200, and each channel may have a plurality of global ports. Local network hosts 300, 400, and 500 have their own local IP addresses, but they are considered to have one global IP address when viewed from outside the local network.

The IP packet transmitted to the RAS through the Internet is converted into a local IP address and a local port in the address and port conversion unit 210 provided in the RAS and transmitted to the corresponding host.

In this case, since the maximum number of PPP (Point to Point Protocol) hosts receiving the Internet service by the RAS is already determined, a conversion table for limiting and assigning a global port range for each channel connecting the RAS and each PPP host is configured. It is preferable.

3 is a diagram illustrating a configuration of a conversion table according to the present invention.

In the example shown in FIG. 3, for convenience of description, it is assumed that a host of a generation local network has one global IP address (100.10.10.20).

Configure a conversion table, but configure one conversion table for each channel connecting each host and RAS, and assign a global port of a certain range to each channel. For example, 20000 to 20299 global ports are allocated to channel A, 20300 to 20599 global ports are allocated to channel B, and 20610 to 20909 global ports are allocated to channel C.

Since one local network host has one local IP address, all local IP addresses are the same on one translation table, but in the case of local ports, they correspond 1: 1 with the global port. It has a port number.

4 is a flowchart illustrating a conversion table configuration and an IP packet transmission process according to the present invention.

Since only TCP packets and UDP packets have port information, when TCP packets or UDP packets are transmitted and received through the Internet, address and port information are added to a translation table existing for each host channel.

When receiving the IP packet transmitted from the host of the local network in the RAS (S41), first check the host channel transmitting the IP packet (S42), and then determine whether the IP packet is a TCP packet or a UDP packet (S43). ).

As a result of the determination, when the IP packet is a TCP packet, a SYN flag bit (SYN flag bit, hereinafter referred to as 'SYN') of the TCP header is set in the IP packet to determine whether a call is currently established. SET), and if the SYN is set, assigns a global port and an entry (S45), and assigns a global IP address, a global port, a local IP address, and a local IP address to the entry. Information such as a port is added (S46). Then, the entry is inserted into the conversion table (S47), NATP processing for converting the local IP address and port into a global IP address and port is performed (S48), and the processing for transmitting the IP packet to the Internet is performed. (S49).

However, if the SYN of the TCP header is not set in the IP packet, it means that information on the IP address and port has already been recorded in the translation table. Therefore, address and port translation processing is performed using the existing translation table. (S51).

In step S43, if it is determined that the received IP packet is a UDP packet, it is first determined whether address and port information for the IP packet exists in a conversion table (S50). If the information exists, the process of converting the address and port using the existing translation table (S51). If the information does not exist in the translation table, the process of S45 for allocating a global port and entry. Configure the conversion table by doing

Although the present invention has been described in detail only with respect to the above-described embodiments, it will be apparent to those skilled in the art that modifications or variations can be made within the spirit and scope of the present invention, and such modifications or changes are within the scope of the claims Will belong.

As described above, the present invention creates a separate translation table for each host channel of a local network interworking with the Internet through a remote access server and allocates a range of ports, thereby retrieving the translation table for address and port translation during IP packet transmission. It can shorten.

Claims (3)

Confirming a host channel by receiving an IP packet from an address and port conversion unit provided in a remote access server; Determining whether the IP packet is a TCP packet or a UDP packet; Determining whether the SYN flag bit of the TCP header is set in the IP packet when the IP packet is a TCP packet; Allocating a global port and an entry when the SYN flag bit of the TCP header is set as a result of the determination; Adding information about a global IP address, a global port, a local IP address, and a local IP port to the entry; Inserting the entry into a conversion table; Converting a local IP address and a local port into a global IP address and a global port; A method of allocating a port by an address and port translation function in a remote access server, comprising: performing a process for transmitting the IP packet to the Internet The method of claim 1, As a result of determining whether the SYN flag bit of the TCP header is set in the IP packet, If the SYN flag bit is not set, converting a local IP address and a local port into a global IP address and a global port by retrieving an existing translation table. How to Configure Translation Tables for Windows. The method of claim 1, Determining whether the IP packet is a TCP packet or a UDP packet, and when the IP packet is a UDP packet, determining whether information on an IP address and a port for the UDP packet exists in a conversion table; If the determination result exists in the conversion table, retrieving an existing conversion table and converting the local IP address and the local port into a global IP address and a global port; Allocating a global port and an entry if not present in the translation table; Adding information about a global IP address, a global port, a local IP address, and a local IP port to the entry; Inserting the entry into a conversion table; Converting a local IP address and a local port into a global IP address and a global port; And a process for transmitting the IP packet to the Internet.