Load Sharing using IP Network Address Translation (LSNAT) (RFC2391)
Original Publication Date: 1998-Aug-01
Included in the Prior Art Database: 2019-Feb-15
Internet Society Requests For Comment (RFCs)
P. Srisuresh: AUTHOR [+1]
In this document, we extend the use of NATs to offer Load share feature, where session load can be distributed across a pool of servers, instead of directing to a single server. This memo provides information for the Internet community. It does not specify an Internet standard of any kind.
Network Working Group P. Srisuresh Request for Comments: 2391 Lucent Technologies Category: Informational D. Gan Juniper Networks, Inc. August 1998
Load Sharing using IP Network Address Translation (LSNAT)
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document combines the idea of address translation described in RFC 1631 with real-time load share algorithms to introduce Load Share Network Address Translators(or, simply LSNATs). LSNATs would transparently offload network load on a single server and distribute the load across a pool of servers.
Network Address Translators (NATs) translate IP addresses in a datagram, transparent to end nodes, while routing the datagram. NATs have traditionally been been used to allow private network domains to connect to Global networks using as few as one globally unique IP address. In this document, we extend the use of NATs to offer Load share feature, where session load can be distributed across a pool of servers, instead of directing to a single server. Load sharing is beneficial to service providers and system administrators alike in grappling with scalability of servers with increasing session load.
Traditionally, Network Address Translators, or simply NATs were used to connect private network domains to globally unique public domain IP networks. Applications originate in private domains and NATs would transparently translate datagrams belonging to these applications in
Srisuresh & Gan Informational [Page 1]
RFC 2391 LSNAT August 1998
either direction. This document combines the characteristic of transparent address translation with real-time load share algorithms to introduce Load Share Network Address Translators.
The problem of Load sharing or Load balancing is not new and goes back many years. A variety of techniques were applied to address the problem. Some very ad-hoc and platform specific and some employing clever schemes to reorder DNS resource records. REF  uses DNS zone transfer program in name servers to periodically shuffle the order of resource records for server nodes based on a pre-determined load balancing algorithm. The problem with this approach is that reordering time periods can be very large on the order of minutes and does not reflect real-time load variations on the servers. Secondly, all hosts in the server pool are assumed to have equal capability to offer all services. This may not often be the case. In addition, there may be requirement to support load balancing for a few specific services only. The load share approach outlined in this document addresses both these concerns and offers a solution that does not require changes to clients or servers and one that can be tailored to individual services or for all services.
For the remind...