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USENIX Tenth System Administration Conference (LISA '96)

IP Multiplexing by Transparent Port-Address Translator

Heon Y. Yeom, Jungsoo Ha, and Ilhwan Kim
Seoul National University


There are certain occasions when we want to have more than one computers using a single IP address. One notable case is when we use firewalls for security reasons or when we use private IP addresses and still want to provide global IP connection. Since the computers behind the firewall or using private IP addresses do not have unique IP addresses, they can not participate in global IP network. However, we still want to provide them some means so that they can be used as if they have real IP addresses.

Another example is when we have more than one server and want to make them appear to be just one server. With the proliferation of WWW, popular WWW servers tend to be overloaded and we need a mechanism to balance the load to several servers when needed. One solution being adopted is address translation by DNS (Domain Name Service). IP reuse using network address translator (NAT) is proposed in [TE93] and standardized by RFC1631. For load balancing of the WWW servers, a round robin distribution scheme using DNS is proposed and is used at NCSA [KBM94]. However, as pointed out from the literature, these schemes are based on DNS and there are several shortcomings. We propose a novel technique to perform address translation without a DNS. Our technique is based on the idea that any internet connection is uniquely identified by the socket pair . By using a address translating bridge, we can provide computers with phony IP addresses real IP connection. The performance of our scheme is investigated using a prototype and the test results show that there is very little overhead in using our scheme.

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