TCP-Eifel does not touch congestion control but improves TCP performance through enhancing its
error control. By the way, "the Eifel" is the name of a beautiful mountain range in Western Germany :-)

TCP-Eifel has the following three new features:
 

1.  The Eifel Algorithm

• The Internet draft is here.
• The abstract and the  paper describing the algorithm in detail is available here.
• Compile (FreeBSD) with option EIFEL_ALG.
• Thanks to Morten Schläger from the Technical University of Berlin, Germany, the Eifel Algorithm has
  also been implemented for LINUX and NS2. The sources and documentation are available here.

2. The Eifel Retransmission Timer

• The abstract and the paper describing the retransmisssion timer in detail is available here. The model

used in that paper is a Microsoft Excel spread sheet available here (zipped .xls [2.7 Mbytes !!!]).
• Compile (FreeBSD) with options EIFEL_RTO and EIFEL_REXMT.

3. “Retransmit Forever”

• There is no paper on this, yet. The motivation for this feature is the following. "Standard" TCP will

close the connection (Reset) after 12 unsuccessful retransmissions which takes on the order of 9 minutes.
We believe that TCP should not do this. Instead, it should be an application layer decision whether a
connection is to be considered "down" or not. There are certainly some less time-critical applications
(e.g., sitting on wireless sensor devices) which would happily accept longer disconnections. Thus, we
changed the code slightly to make the TCP sender retransmit "forever", i.e., retransmit the oldest
outstanding segment every 64 seconds. This will continue until the application explicitly closes the
connection.
• Compile (FreeBSD) with option EIFEL_FOREVER.

The current version of TCP-Eifel for FreeBSD is 1.1. It was implemented by Reiner Ludwig in the context of 
the ICEBERG Project. A patchfile for FreeBSD 3.2 is available here.

Please report bugs and suggestions to Reiner Ludwig (Reiner.Ludwig@eed.ericsson.se) and
Keith Sklower (sklower@cs.berkeley.edu) who greatly supported the implementation and testing work.
 

Last updated 08/17/2000.