Shepherd writeup

As required by RFC 4858, this is the current template for the Document 
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?

This document is intended to be an Informational RFC that describes the TACACS+ protocol the way it is implemented _today_.  This is an important point.  This document is not intending to change TACACS+ or address the security issues inherent within it.  It is setting the stage for enhancing the security of TACACS+, but it is only aimed at adding referential context on how TACACS+ is implemented currently.  As such Informational is the right status for this document.

The IESG should keep in mind that many operators use TACACS+ today, therefore documenting how it works is useful.  This is especially true given the desire of the authors to extend the protocol to address the security flaws in something that is so ubiquitous.

The intended Informational status is clearly mentioned in the header.

(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:

Technical Summary

  TACACS+ provides Device Administration for routers, network access
  servers and other networked computing devices via one or more
  centralized servers.  This document describes the protocol that is
  used by TACACS+.  In particular, this document describes the TACACS+ protocol the way it is   
  currently implemented and does not attempt to modify any of its inherent security issues.

Working Group Summary

  Initially, this document described both the current TACACS+ protocol implementation plus extensions to allow for T+ over TLS.  The working group though this muddied the water too much, and it was desired to first document the TACACS+ protocol as it stands today as an informational document.  Once that document was ratified, a new document would be submitted for properly securing TACACS+ with TLS.

There was broad WG support for documenting TACACS+ as it is widely used and implemented in the industry.  However, there were some procedural issues with how this document evolved.  One WG member was particular vocal, initially in his objection to adding another AAA protocol, but then on how the document authorship was handled.  As mentioned, the WG saw value in documenting this given its ubiquity.  But the authorship of the document could have been handled better.

The problems included:

* The authors were slow to respond to comments initially
* The authors did no summarize changes revision-over-revision of the document
* A large amount of text was contributed by a working group member, but that member was not acknowledged in the text
* Some comments went a long while without being addressed

By the end of the process, all of these items had been addressed and author response had increased and improved.

Additionally, a section was added to the document to attempt to mitigate some of the known security issues by offering some best practices in terms of deployment.  These practices do not alter the protocol itself but can help mitigate potential security issues.

Finally, a call for implementations was done to confirm that known implementations in the wild adhere to this.  Numerous vendors and clients responded including Cisco, Huawei, Aviatnet, and FreeRADIUS that indicate their implementation adheres to this document with varying levels of support of various protocol options.

Document Quality

  It is strongly believed this document adequately and completely describes the TACACS+ protocol as it exists today.  See above with respect to known implementations that adhere to this document.


  The document shepherd is Joe Clarke and the associated AD is Ignas Bogdonas.

(3) Briefly describe the review of this document that was performed by
the Document Shepherd.  If this version of the document is not ready
for publication, please explain why the document is being forwarded to
the IESG.

I have read this document and commented on it to the authors and WG.  I feel it is ready to go to the IESG.

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?

I feel this document has been fully reviewed and has had multiple comments and corrections.

(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
took place.

Obviously, security is going to be a sticking point.  But as I have mentioned above, the intent is to define the protocol as it exists currently.  It is known that there are security issues.  The document describes those and offers some suggestions to mitigate.  IESG members should keep this in mind.  The ultimate goal is to improve the security of TACACS+ in a new document to be defined after this one completes.

A deeper security review only insofar as any leading practices that might be missing may be warranted.  While the protocol itself cannot be modified, anything that could help one mitigate known issues with TACACS+ have been listed, and it might be desirable to list other steps as well.

(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
concerns here.

I have no concerns with the document at this point.

(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.

Yes, all authors have stated there is no known IPR.  I have not seen any contributors state that there is IPR on this draft.

(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR


(9) How solid is the WG consensus behind this document? Does it 
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it?   

This document has reached consensus after much consternation from certain WG members.  Those members have provided substantive comments and have helped increase the integrity of this document.

(10) Has anyone threatened an appeal or otherwise indicated extreme 
discontent? If so, please summarise the areas of conflict in separate
email messages to the Responsible Area Director. (It should be in a
separate email because this questionnaire is publicly available.) 

I will send a separate email.

(11) Identify any ID nits the Document Shepherd has found in this
document. (See and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be

The IDNITS have been mostly cleared up.  There is one error flagged in that this document references PAP [RFC1334], which was obsoleted by CHAP.  However, PAP is actually valid since we are truly documenting the way TACACS+ protocol works today.  (Ultimately, the desire is to have a new draft that makes usage of PAP moot as TLS is intended.)

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.


(13) Have all references within this document been identified as
either normative or informative?

Not yet.

(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?


(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in 
the Last Call procedure. 


(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.


(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).

There are no IANA considerations.

(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.


(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.