Apparatus and methods for determining the correct workstation within a LAN for a LAN modem to route a packet

• US 6,563,824 B1
• Filed: 04/20/1999
• Issued: 05/13/2003
• Est. Priority Date: 04/20/1999
• Status: Expired due to Fees

• Current Assignee: Fres-co System USA, Inc., Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Douglas, C. Paul, Wang, Jyh-Ming J., Bhatia, Rajiv, Brennan, Daniel M, Zhang, Suiling C.
• Primary Examiner(s): Nguyen, Chau
• Assistant Examiner(s): DUONG, DUC T
• Application Number:
  US09/295,155
• Time in Patent Office: 1,484 Days
• Field of Search: 370/351, 370/352, 370/353, 370/354, 370/355, 370/356, 370/389, 370/390, 370/392, 370/400, 370/401, 370/466, 370/473, 370/475
• US Class Current: 370/392
• CPC Class Codes: H04L 61/00 Network arrangements, protocols or services for addressing or naming
• CPC Class Codes: H04L 61/2514 between local and global IP addresses

Abstract

A LAN modem permits unambiguous routing for multiple workstations located on a LAN to each gain access through the LAN modem to any one of a number of different remote servers located on a number of different remote networks using a combination of public port number and public address of the workstation. There are instances where sessions are changed between the same workstation/server. This changing of sessions changes the public port numbers associated with each session, which destroys the above unambiguous routing, since the combination of a public destination IP address and a private destination port number is no longer the same unique value contained in an address translation table of the LAN modem. A four step hierarchical procedure is provided in which the LAN modem determines which workstation the packet is to be routed based upon value of fields stored in the network address translation (NAT) table or value of fields stored in a static table. The NAT table or static table entries are compared to the values of fields stored in the packet header.

Claims

1. A routing method comprising the steps of:

searching for an entry in a NAT table matching a header portion of a received packet and, if found, routing the packet to an appropriate destination;

searching, if the above step is unsuccessful, for an entry in a static table matching the header portion of the received packet, and, if found, routing the packet to the appropriate destination;

searching, if the above steps are unsuccessful, for an entry in the NAT table having an identifier matching the header portion, and, if found, creating a NAT table entry and routing the packet to the appropriate destination; and

identifying, if the above steps are unsuccessful, a profile to which a remote server that.provided the received packet belongs, and, routing the packet to the appropriate destination.

2. The method according to claim 1 wherein the appropriate destination in the identifying step is a designated destination.

3. The method according to claim 1 wherein the first searching step includes the steps of:

comparing, a value stored in a source address field of the header portion of the received packet with a value stored in an ISP/IP address field of an entry stored in the NAT table;

comparing, a value stored in a protocol ID field of the header portion of the received packet with a value stored in a protocol ID field of the entry stored in the NAT table;

comparing, a valued stored in a source port number field of the header portion of the received packet with a value stored in an ISP side/port number field of the entry stored in the NAT table; and

comparing, a value stored in a destination port number field of the header portion of the received packet with a value stored in a LAN side/public port number field of the entry stored in the NAT table.

4. The method according to claim 3 wherein the second searching step includes the steps of:

comparing, a value stored in a protocol ID field of the header portion of the received packet with a value stored in a protocol ID field of each entry contained in the static table; and

comparing a value stored in a destination port number field of the header portion of the received packet with a value stored in a LAN side/port number field stored in the static table.

5. The method according to claim 4 wherein the third searching step includes the step of:

comparing, a value stored in a source IP address field of the header portion of the received packet with a value stored in an ISP side/IP address field of a NAT table entry.

6. The method according to claim 4 wherein the third searching step includes the step of:

comparing, a value stored in a B channel field of a NAT table entry with a B channel on which the received packet arrived.

7. The method according to claim 5 wherein the identifying step includes the steps of:

locating, in a local database, a service provider profile relating to the remote server that provided the received packet; and

identifying, the appropriate destination to which to route the received packet from the service provider profile.

8. The method according to claim 6 wherein the appropriate destination is the busiest destination.

9. The method according to claim 6 wherein the appropriate destination is the destination having the greatest number of applications.