This document specifies the TCP Authentication Option (TCP-AO), which
obsoletes the TCP MD5 Signature option of RFC-2385 (TCP MD5). TCP-AO
specifies the use of stronger Message Authentication Codes (MACs),
protects against replays even for long-lived TCP connections, and
provides more details on the association of security with TCP
connections than TCP MD5. TCP-AO is compatible with either static
master key tuple (MKT) configuration or an external, out-of-band MKT
management mechanism; in either case, TCP-AO also protects
connections when using the same MKT across repeated instances of a
connection, using traffic keys derived from the MKT, and coordinates
MKT changes between endpoints. The result is intended to support
current infrastructure uses of TCP MD5, such as to protect long-lived
connections (as used, e.g., in BGP and LDP), and to support a larger
set of MACs with minimal other system and operational changes. TCP-AO
uses a different option identifier than TCP MD5, even though TCP-AO
and TCP MD5 are never permitted to be used simultaneously. TCP-AO
supports IPv6, and is fully compatible with the proposed requirements
for the replacement of TCP MD5.
Working Group Summary
There was some initial controversy on this work due to the prior rushed
deployment of a similar mechanism which had not been reviewed by the
The WG's decision to build an incompatible mechanism was not unanimous,
with strong initial resistance from one of the implementers of the prior
solution, however other implementors of that solution did come out in
support of the WG's product during the course of its evolution.
Several widely-deployed implementations exist of a pre-WG protocol
which is not compatible with the WG's protocol, but very similar both
functionally and on the wire. Some vendors have expressed strong
support for implementing the WG's product. At one point, a Linux
implementation was being pursued of the WG draft, though its status
with regard to the current document is unknown.
Wesley Eddy (Wesley.M.Eddy@nasa.gov) is the document shepherd. Lars
Eggert (firstname.lastname@example.org) reviewed the document for the IESG.