Explicit Transport Error Notification (ETEN)
Originally TCP inferred congestion from packet loss and responded by
lowering the congestion window, irrespective of whether the packets
were dropped due to errors or congestion. The inability to distinguish
between these losses can affect the throughput adversely, especially on
paths with high error rates. If the TCP sender can distinguish packets
that are lost due to congestion from ones that are lost due to errors,
a better performance can be achieved. This is because, a higher link
capacity utilization can be achieved by retransmitting errored packets
without reducing the congestion window unnecessarily.
Some approaches have been proposed to distinguish congestion losses
from errors. Also, if explicit congestion notification (ECN) is used,
it may be possible to implicitly determine losses due to errors.
We are evaluating potential enhancements to TCP that are based on
explicit transport error notifications (ETEN) from intermediate routers
and/or end systems. The issues we are currently investigating include:
- bounds on TCP throughput improvements possible from ETEN under ideal
loss information
- actual performance achievable over a range of realistic network
topologies and traffic scenarios with different TCP strains such as
Reno and SACK, via simulations
- propose, and evaluate the performance of, specific ETEN mechanisms for:
- forward vs. backward notifications
- per-packet vs. aggregate error notifications
- assessing current error rate
- ideal TCP behavior on receiving notification
- security aspects including:
- potential vulnerabilities of the proposed mechanisms to distributed
denial-of-service attacks
- operation over encrypted tunnels, VPNs, and MPLS paths, where
intermediate nodes may not be able to determine actual source or
destination addresses and ports to forward notifications
Reports and Documentation
-
Rajesh Krishnan, Mark Allman, Craig Partridge, and
James P.G. Sterbenz, "Explicit Transport Error Notification for Error-Prone
Wireless and Satellite Networks,"
BBN Technical Report No. 8333, BBN Technologies,
February 07, 2002 (revised March 22, 2002).
[Abstract]
[Postscript]
[PDF]
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Rajesh Krishnan, Mark Allman, Craig Partridge, James P.G. Sterbenz,
and William Ivancic, "Explicit Transport Error Notification (ETEN)
for Error-Prone Wireless and Satellite Networks - Summary,"
Earth Science Technology Conference - 2002 , Pasadena, CA, USA,
June 11-13, 2002.
[PDF]
[PDF -- Local Copy]
-
Rajesh Krishnan, James P.G. Sterbenz, Wesley M. Eddy, Craig Partridge,
and Mark Allman, "Explicit Transport Error Notification (ETEN) for
Error-Prone Wireless and Satellite Networks," Pre-print: Accepted
for publication in Elsevier Computer Networks.
[Abstract]
[Postscript]
[PDF]
People Involved