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
Abstract
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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