Many machines will have two entries in the local name server. The DNS server must examine the source address of the request and decide which entry to use. If the source address matches the well-known internal network number, it passes the internal address of the domain name. Otherwise, the name server passes the external address. An EASS server is required to manage the sharing of the external addresses, i.e., to allocate and de-allocate external addresses to the machines which do not have permanent external addresses.
Many hosts do an inverse lookup of incoming connections.
Therefore, it is desirable the entry in the DNS server be updated whenever a new external address is allocated. This will also allow an machine which currently has a temporary external address to be called by other machines. The updating of the entry in the DNS server can be done more easily if the EASS server and DNS server are co-located. Acknowledgements We would like to thank J. K. Reynolds for the network statistics, and V. Cerf, C. Topolcic, K. McCloghrie, R. Ullmann and K. Carlberg for their useful comments and discussion. May 1992 Security Considerations Security issues are not discussed in this memo.