NAPT gateway system with method capable of extending the number of connections

• US 20040098512A1
• Filed: 03/19/2003
• Published: 05/20/2004
• Est. Priority Date: 11/19/2002
• Status: Abandoned Application

• Current Assignee: Institute For Information Industry
• Original Assignee: Institute For Information Industry
• Inventors: Lin, Jyun-Naih
• Application Number:
  US10/390,790
• Publication Number:
  US 20040098512A1
• Time in Patent Office: Days
• US Class Current: 709/249
• CPC Class Codes: H04L 2101/663 Transport layer addresses, e.g. aspects of transmission control protocol [TCP] or user datagram protocol [UDP] ports
• CPC Class Codes: H04L 61/2517 using port numbers
• CPC Class Codes: H04L 61/255 Maintenance or indexing of mapping tables

Abstract

NAPT gateway system with method for extending the number of connections are disclosed. The gateway is located between a private network and the Internet and has a plurality of NAPT tables. When receiving a packet transmitted from the private network to the Internet, the gateway takes the destination IP address of the packet as a hash key for corresponding to a NAPT table of the NAPT tables via a hash function. An item of the NAPT table that conforms to the packet is determined, and the source IP address and the source port of the packet are translated into the legal address of the NAPT gateway and the index of the item, respectively, based on the item.

Claims

1. A method used by a NAPT gateway for extending the number of connections, the gateway being located between a private network and the Internet and having a plurality of NAPT tables, each NAPT table having a plurality of items, each item being provided for storing a connection information of a flow, the method comprising the steps of:

(A) when receiving a packet transmitted from the private network to the Internet, the gateway taking the destination IP address of the packet as a hash key for corresponding to a NAPT table of the NAPT tables via a hash function;

(B) if an item of the NAPT table conforms to the packet, translating the source IP address and the source port of the packet into the legal IP address of the NAPT gateway and the index of the item, respectively, based on the item; and

(C) if no item of the NAPT table conforms to the packet, finding an unused item in the NAPT table for storing connection information of the packet and translating the source IP address and the source port of the packet into the legal IP address of the NAPT gateway and the index of the found item, respectively.

2. The method as claimed in claim 1, wherein, in steps (B) and (C), each of the items in the NAPT table is stored with connection information including source IP address, source port, destination IP address, and destination port of the packet.

3. The method as claimed in claim 2, wherein the index of the item is taken as the source port number after translation.

4. The method as claimed in claim 2, wherein the index of the item plus a constant is taken as the source port number after translation.

5. The method as claimed in claim 3, further comprising the steps of:

(D) when receiving a packet transmitted from the Internet to the private network, the gateway taking the source IP address of the packet as the hash key for corresponding to a NAPT table of the NAPT tables via the hash function; and

(E) taking the destination port number of the packet as an index for accessing a corresponding item of the NAPT table, and if the item conforms to the packet, translating the destination IP address and the destination port of the packet into the original source IP address and source port recorded in the item.

6. The method as claimed in claim 5, wherein, in step (E), the packet is discarded the item does not conform to the packet.

7. A NAPT gateway system capable of extending the number of connections comprising:

a machine coupled to a private network;

at least one machine coupled to the Internet; and

a NAPT gateway located between the private network and the Internet for translating packets transmitted from the machine in the private network to be routed to the machine in the Internet, the NAPT gateway having a plurality of NAPT tables, each NAPT table having a plurality of items, each item being provided for storing a connection information of a flow,

wherein, when receiving a packet transmitted from the private network to the Internet, the gateway takes the destination IP address of the packet as a hash key for corresponding to a NAPT table of the NAPT tables via a hash function, and finds an item of the NAPT table conforming to the packet for translating the source IP address and the source port of the packet into the legal address of the NAPT gateway and an assigned port number, respectively, based on the item.

8. The system as claimed in claim 7, wherein, if no item of the NAPT table conforms to the packet, an unused item in the NAPT table is found for storing connection information of the packet.

9. The system as claimed in claim 8, wherein each of the items in the NAPT table is stored with connection information including source IP address, source port, destination IP address, and destination port of the packet.

10. The system as claimed in claim 9, wherein the NAPT table takes the index of the item as the source port number after translation

11. The system as claimed in claim 9, wherein the NAPT table takes the index of the item plus a constant as the source port number after translation.

12. The system as claimed in claim 10, wherein, when receiving a packet transmitted from the Internet to the private network, the gateway takes the source IP address of the packet as the hash key for corresponding to a NAPT table of the NAPT tables via the hash function and then takes the destination port number of the packet as an index for accessing a corresponding item of the NAPT table, and if the item conforms to the packet, the destination IP address and the destination port of the packet are translated into the original source IP address and source port recorded in the item, otherwise the packet is discarded.