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Recommendations for Transport-Protocol Port Randomization
RFC 6056

Approval announcement
Draft of message to be sent after approval:


From: The IESG <>
To: IETF-Announce <>
Cc: Internet Architecture Board <>,
    RFC Editor <>
Subject: Protocol Action: 'Transport Protocol Port Randomization Recommendations' to BCP

The IESG has approved the following document:
- 'Transport Protocol Port Randomization Recommendations'
  <draft-ietf-tsvwg-port-randomization-09.txt> as a BCP

This document is the product of the Transport Area Working Group.

The IESG contact person is Lars Eggert.

A URL of this Internet Draft is:

Ballot Text

Technical Summary

Recently, awareness has been raised about a number of "blind" attacks
that can be performed against the Transmission Control Protocol
(TCP) and similar protocols.  These attacks rely on the attacker's
ability to guess or know the five-tuple (Protocol, Source Address,
Destination Address, Source Port, Destination Port) that identifies
the transport protocol instance to be attacked.  This document
describes a number of simple and efficient methods for the selection
of the client port number, such that the possibility of an attacker
guessing the exact value is reduced.  While this is not a replacement
for cryptographic methods for protecting the transport-protocol
instance, the described port number obfuscation algorithms provide
improved security/obfuscation with very little effort and without
any key management overhead.

Working Group Summary

Understanding that 'strong' consensus is nearly impossible in an open 
area WG such as TSVWG, with 5-6 sub-groups within this WG divided 
along technology focuses -- there is unwavering consensus in the WG 
amongst interested parties to publish this document. It has been 
reviewed by several people in the WG last call. Comments raised have 
been addressed.

Document Quality

Several stacks implement different port randomization techniques. The
techniques that this document describes include the ones implemented
by FreeBSD, Linux, NetBSD, OpenBSD and OpenSolaris.


James Polk ( is the document Shepherd. Lars Eggert
( is the responsible Area Director.

RFC Editor Note