RFC 2075 (rfc2075) - Page 1 of 5
IP Echo Host Service
Alternative Format: Original Text Document
Network Working Group C. Partridge
Request for Comments: 2075 BBN
Category: Experimental January 1997
IP Echo Host Service
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. This memo does not specify an Internet standard of any
kind. Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Abstract
This memo describes how to implement an IP echo host. IP echo hosts
send back IP datagrams after exchanging the source and destination IP
addresses. The effect is that datagrams sent to the echo host are
sent back to the source, as if they originated at the echo host.
Introduction
An IP echo host returns IP datagrams to their original source host,
with the IP source and destination addresses reversed, so that the
returning datagram appears to be coming from the echo host to the
original source. IP echo hosts are tremendously useful for debugging
applications and protocols. They allow researchers to create looped
back conversations across the Internet, exposing their traffic to all
the vagaries of Internet behavior (congestion, cross traffic,
variable round-trip times and the like) without having to distribute
prototype software to a large number of test machines.
IP echo hosts were heavily used on the Internet in the late 1970s and
early 1980s to debug various Internet transport and application
protocols. But, for reasons unclear, at the current date there are
no echo hosts on the Internet and few people are even aware of the
concept. The goal of this memo is to document the concept in the
hopes it will be revived.
Implementation Details
While the basic idea of a echo host is simple, there are a few
implementation details that require attention. This section
describes those implementation details. The presentation works from
the simplest to most difficult issues.
Partridge Experimental