AAA Protocol Evaluation David Mitton
INTERNET-DRAFT Nortel Networks
Category: Informational Michael St.Johns
July 2000 Excite@Home
Stuart Barkley
UUnet
Dave Nelson
Cabletron
Basaraj Patil
Nokia
Mark Stevens
Ellacoya Networks
Barney Wolff
Databus Inc.
Authentication, Authorization, and Accounting:
Protocol Evaluation
draft-ietf-aaa-proto-eval-00.txt
Status of this Memo
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provisions of Section 10 of RFC2026.
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Abstract
This document represents the preliminary findings of the AAA WG panel
evaluating protocols proposed against the AAA Network Access Require-
ments. Due to time constraints this document is not as fully developed
as desired. And may be updated on the working group list.
This document is a draft submission of the Authentication, Authoriza-
tion, and Accounting (AAA) Working Group of the Internet Engineering
Task Force (IETF). Comments should be submitted to the mailing list
aaa-wg@merit.edu.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Chairman's Note . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Members of the Group . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Requirements Validation Process . . . . . . . . . . . . . . . 6
1.4. Proposal Evaluation . . . . . . . . . . . . . . . . . . . . . 7
1.5. Final Recommendations Process. . . . . . . . . . . . . . . . . 7
2. Protocol Proposals . . . . . . . . . . . . . . . . . . . . . . . 8
3. Item Level Composite Compliance. . . . . . . . . . . . . . . . . 8
3.1 General Requirements . . . . . . . . . . . . . . . . . . . . . . 9
3.2 Authentication Requirements . . . . . . . . . . . . . . . . . . 10
3.4 Accounting Requirements
3.5 MOBILE IP Requirements
4. Protocol Evaluation Summaries
4.1. SNMP
4.2. Radius++
4.3. Diameter
4.4. COPS
4.5. Summary Recommendation
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 16
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7. Author's Addresses. . . . . . . . . . . . . . . . . . . . . . . 17
8. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 17
9. Appendix Summary Evaluations
10. Appendix Review of the Requirements
11. Appendix Position Briefs
12. Appendix Meeting Minutes
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1. Introduction
Due to time constraints, this document in it's current form is not as
complete or as well polished as we may wish. This version was rushed to
meet the publication deadline of the June 2000 Pittsburg meeting.
Updated versions may be distributed on the AAA Work Group's mailing
list, prior to the meeting itself.
1.1. Chairman's Note:
This document is the result of 6 weeks of intense work by the panel
listed below. Our mission was to evaluate the various AAA proposals and
provide recommendations to the AAA working group and to the IESG on the
viability of each of the proposals.
The evaluation process had three distinct phases. 1) Validate the AAA
requirements document [AAAReqts] against the base requirements documents
for NASREQ, MOBILEIP and ROAMOPS. 2) Evaluate each of the SNMP,
Radius++, Diameter and COPS proposal claims against the validated
requirements. 3) Provide final recommendations based on side by side
comparison for each proposal on a requirement by requirement basis.
In general, the ONLY information the evaluators were allowed to use
throughout the process was that provided in the source documents (the
requirements document and the proposal) or documents referenced by the
source documents. In other words, if it wasn't written down, it gen-
erally didn't exist. Our cutoff for acceptance of information was 1
June 2000 - any submissions after that time were not considered in the
panel's deliberations.
1.2. Members of the Group
The group was chaired by Michael St.Johns. David Mitton was the docu-
ment editor. Following are the background statements and any conflicits
of interest from them and the rest of the panel.
Michael St. Johns, Excite@Home
I have no known conflicts of interest with respect to the AAA process.
I have neither advocated nor participated in the creation of any of the
submissions. My company is a service company (ISP) and will not be
involved in the manufacture or sale of AAA enabled products. Other
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than my participation as the chair of the AAA evaluation process, I have
not had any contact with the AAA standards process.
David Mitton, Nortel Networks
I have been Nasreq WG co-chair and author of several Nasreq drafts. As
well as, previously contributed to several RADIUS drafts.
I have been a RADIUS NAS implementor and Technical Prime on our Server
products, so know it extremely well. In my current job role I am
involved with Nortel's IP Mobility products, which support Diameter.
I have written a presentation on COPS vs NASreq Requirements for a
Nasreq meeting, but have not implemented it, nor consider myself an
through expert on the subject.
Stuart Barkley, UUnet
I've been working for 5 years at UUNET on various parts of our dialup
network. I have extensive experience with designing, developing and
operating our SNMP based usage data gathering system. I've also been
involved in our radius based authentication and authorization systems in
an advisory position.
I've participated in radius/roamops/nasreq/aaa groups for the past
several years. I'm not an author or contributer on any of the require-
ments or protocol documents being presented although I have been peri-
pherally involved in these working groups.
Dave Nelson, Cabletron
Very active in the RADIUS WG, especially during the early years. No
involvement in the AAA submission. Have not contributed to the develop-
ment of Diameter.
No involvement with SNMPv3 or the AAA submission. David Harrington, a
proponent, works in a different group within my company. We have not
discussed the submission. No involvement with the COPS protocol.
Basavaraj Patil, Nokia
I am a contributor to the AAA requirements document (draft-ietf-
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mobileip-aaa-reqs-03.txt) submitted by the Mobile IP WG. I was a member
of the team that was constituted to capture the Mobile IP requirements
for AAA services.
As part of the co-chairing activity of the Mobile IP WG I have realized
the need for AAA services by Mobile IP and hence closely followed the
work done in the AAA WG, RADIUS, RoamOps and TR45.6.
My present work at Nokia does involve looking at AAA protocols (to some
extent at least) for use in wireless networks. I have also done some
work with AAA protocols such as DIAMETER in my previous job at Nortel
Networks.
Mark Stevens, Ellacoya Networks
I am the co-chair of the IETF RAP working group which is the working
group that has developed the COPS protocol. I have not contributed to
the documents describing how COPS can satisfy AAA requirements.
I participated in early AAA working group meetings, but have not been an
active participant since the group's rechartering. The company that
currently employees me builds devices might benefit from being AAA
enabled.
Barney Wolff, Databus Inc.
I have implemented RADIUS client, proxy and server software, under con-
tract to AT&T. That software is owned by AT&T and I have no financial
interest in it.
I have been a member of the RADIUS WG for several years, and consider
myself an advocate for RADIUS against what I consider unjustified
attacks on it.
I've never worked for any of the companies whose staff have produced any
of the proposals, although I obviously might at some future time.
1.3. Requirements Validation Process
For each of the base requirements documents, the chair assigned a team
member to re-validate the requirement. The process was fairly mechani-
cal; the evaluator looked at what was said in [AAAReqts], and verified
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that the references and supporting text in the basis document supported
the requirement in [AAAReqts] as stated. Where the reference was wrong,
too general, missing or otherwise did not support the requirement, the
evaluator either deleted or downgraded the requirement. The results of
that process were sent to the AAA mailing list and are also included in
this document in the appendixes. The group's used [AAAReqts] as modi-
fied by our validation findings to evaluate the AAA proposals.
1.4. Proposal Evaluation
For each of the four proposals, the chair assigned two panel members to
write evaluation briefs. One member was assigned to write a 'PRO' brief
and could take the most generous interpretation of the proposal; he
could grant benefit of doubt. The other member was assigned to write a
'CON' brief and was required to use the strictest criteria when doing
his evaluation.
Each brief looked at each individual requirement and evaluated how close
the proposal came in meeting that requirement. Each item was scored as
one of an 'F' for failed to meet the requirement, 'P' for partially
meeting the requirement, or 'T' for totally meeting the requirement.
The proposals were scored only on the information presented. This means
that a particular protocol might actually meet the specifics of a
requirement, but if the proposal did not state, describe or reference
how that requirement was met, in might be scored lower.
The panel met by teleconference to discuss each proposal and the PRO and
CON briefs. Each of the briefers discussed the high points of the brief
and gave his summary findings for the proposal. We then discussed each
individual requirement line-by-line as a group. At the conclusion, the
members provided their own line-by-line evaluations which were used to
determine the consensus evaluation for the specific requirement relative
to that proposal. The meeting notes from those teleconferences as well
as the individual briefs are included in the appendixies.
1.5. Final Recommendations Process
The panel met for one last time to compare the results for the four pro-
posals and to ensure we'd used consistent scoring criteria. We did a
requirement by requirement discussion, then a discussion of each of the
protocols.
The final phase was for each member to provide his final summary evalua-
tion for each of the protocols. Each proposal was scored as either Not
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Acceptable, Acceptable Only For Accounting, Acceptable with Engineering
and Fully Acceptable. Where a proposal was acceptable with engineering,
the member indicated whether it would be a small, medium or large
amount.
2. Protocol Proposals
The following proposal documents were submitted to the AAA WG for con-
sideration by the deadline.
- SNMP:
[SNMPComp] "Comparison of SNMPv3 Against AAA Network Access
Requirements", B. Natale, draft-natale-aaa-snmpv3-comp-00.txt
- RADIUS Enhancements:
[RADComp] "Comparison of RADIUS Against AAA Network Access
Requirements", Ekstein, T'Joens, DeVries,
draft-tjoens-aaa-radius-comp-00.txt
[RADExt] "Framework for the extension of the RADIUS(v2) protocol",
T'Joens, Ekstein, DeVries, draft-tjoens-aaa-radius-00.txt
- DIAMETER
[DIAComp] "Comparison of DIAMETER Against AAA Network Access
Requirements", Calhoun, draft-calhoun-aaa-diameter-comp-00.txt
- COPS for AAA:
[COPSComp] "Comparison of COPS Against the AAA NA Requirements",
Khosravi, Durham, Walker, draft-durham-aaa-cops-reqments-00.txt
[COPSAAA] "COPS Usage for AAA", Durham, Khosravi, Weiss, Filename,
draft-durham-aaa-cops-ext-00.txt
3. Item Level Composite Compliance
For each requirement item, the group reviewed the proposal's level of
compliance. Where the proposal was lacking, the evaluators may have
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made supposition on how hard it would be to resolve the problem. The
following shows the combined results for each requirement item.
Key:
T = Total Compliance
P = Partial Compliance
F = Failed Compliance
Where two are shown eg: P/T, there was a tie.
3.1 General Requirements
3.1.1 Scalability - SNMP:P, RADIUS:P, Diameter:T, COPS:T
SNMP was downgraded due to a lack of detail of how the current agent
model would be adapted to a client request based transaction. The
RADIUS proposal did not address the problem adequately. There are open
issues in all proposals with respect to webs of proxies.
3.1.2 Fail-over - SNMP:P, RADIUS:P, Diameter:P, COPS:T/P
The group particularly noted that it didn't not think any protocol did
well in this requirement. Insufficient work has been done to specify
link failure detection and primary server recovery in most submissions.
COPS has some mechanisms but not all. How these mechanisms would work
in a web of proxies has not been addressed.
3.1.3 Mutual Authentication - SNMP:T, RADIUS:T/P, Diameter:T, COPS:T
Many of the submissions missed the point of the requirement. There
should be a way for the peers to authenticate each other, end-to-end, or
user-to-server. However, the group questions who really needs this
feature, and if it could be done at a different level.
Mutual authentication in RADIUS is only between hops.
3.1.4 Transmission Level Security - SNMP:T, RADIUS:P, Diameter:T,
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COPS:T
All protocols have methods of securing the message data.
3.1.5 Data Object Confidentiality - SNMP:P, RADIUS:P, Diameter:T,
COPS:T
This requirement usually comes from third-party situations, such as
access outsourcing.
Diameter and COPS both use CMS formats to secure data objects. The
group is concerned if this method and it's support is perhaps too heavy
weight for NAS and some types of edge systems.
3.1.6 Data Object Integrity - SNMP:F, RADIUS:P, Diameter:T, COPS:T
How to guard the data object from changes was not adequately described
in the SNMP proposal. The RADIUS solution was not very strong either.
3.1.7 Certificate Transport - SNMP:T, RADIUS:T, Diameter:T, COPS:T
All protocols can figure out some way to transport a certificate.
3.1.8 Reliable AAA Transport - SNMP:P, RADIUS:P, Diameter:T, COPS:T
The requirement does not give a definition of "how reliable" it must be.
The SNMP and RADIUS proposals lacked in providing solutions to message
retransmission and recovery.
3.1.9 Run over IPv4 - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.1.10 Run over IPv6 - SNMP:P, RADIUS:T, Diameter:T, COPS:T
The SNMP proposal indicated that this area is still in the experimental
stages.
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3.1.11 Support Proxy and Routing Brokers - SNMP:F, RADIUS:P,
Diameter:T, COPS:P
The SNMP proposal did not address this requirement. COPS claims sup-
port, but does not work through some of the issues. Diameter was the
only protocol that attempted to address this area to a fair extent.
3.1.12 Auditability - SNMP:F, RADIUS:F, Diameter:T, COPS:P
We treated this requirement as something like "non-repudiation". There
is a concern that digital signatures may be too computationally expen-
sive for some equipment, and not well deployed on those platforms.
The SNMP and RADIUS proposals did not attempt to work this requirement.
COPS suggests that a History PIB will help solve this problem but gives
no description.
3.1.13 Shared Secret Not Required - SNMP:P/T, RADIUS:T, Diameter:T,
COPS:T
The requirement is interpreted to mean that any application level secu-
rity can be turned off in the presence of transport level security.
Pretty much every protocol can use an enveloping secure transport that
would allow them not to use an internal secret.
3.1.14 Ability to Carry Service Specific Attributes - SNMP:T, RADIUS:T,
Diameter:T, COPS:T
3.2 Authentication Requirements
3.2.1 NAI Support - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.2.2 CHAP Support - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.2.3 EAP Support - SNMP:T, RADIUS:T, Diameter:T, COPS:T
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3.2.4 PAP/Clear-text Passwords - SNMP:T, RADIUS:T, Diameter:T, COPS:T
The requirement for clear-text passwords comes from one-time-password
systems and hard-token (SecurID) systems.
3.2.5 Reauthentication on demand - SNMP:T, RADIUS:P, Diameter:P, COPS:T
To supply this, the proposal must have asynchronous peer-to-peer cabili-
ties, and there must defined operation for such state changes.
We also distinguished event-driven resuthentication from timer-driven
(or lifetime-driven). Also concerned about how this would work in a
proxy environment.
3.2.6 Authorization w/o Authentication - SNMP:P, RADIUS:T/P, Diameter:T,
COPS:T
This requirement really means authorization with trivia authentications
(e.g. by assertion or knowlege).
3.3 Authorization Requirements
3.3.1 Static and Dynamic IP Addr Assignment - SNMP:P/F, RADIUS:T,
Diameter:T, COPS:T
There is difficulty in interpreting what is static or dynamic with
respect to the viewpoint of the client, server, administrator or user.
3.3.2 RADIUS Gateway Capability - SNMP:P, RADIUS:P, Diameter:T/P,
COPS:P
It was noted that any new cability in a new AAA protocol would not be
able to map directly back to RADIUS. But this is already a problem
within a RADIUS environment.
3.3.3 Reject Capability - SNMP:T/P/F, RADIUS:T, Diameter:T, COPS:P
3.3.4 Preclude Layer 2 Tunneling - SNMP:F, RADIUS:T, Diameter:T, COPS:T
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3.3.5 Reauthorization on Demand - SNMP:P/F, RADIUS:P, Diameter:T/P,
COPS:T
Some evaluators wondered how the server will know that re-authorization
is supposed to be done? Will it interface to something external, or
have sufficent internals?
3.3.6 Support for Access Rules & Filters - SNMP:P, RADIUS:P,
Diameter:P, COPS:T/P
Only the Diameter proposal actually tackled this issue, but the group
felt that the rules as designed were too weak to be useful. There was
also concern about standardizing syntax without defining semantics.
3.3.7 State Reconciliation - SNMP:F, RADIUS:P/F, Diameter:P, COPS:T/P
All of the protocols were weak to non-existent on specifying how this
would be done in a web of proxies situation.
3.3.8 Unsolicited Disconnect - SNMP:T, RADIUS:P, Diameter:T, COPS:T
3.4 Accounting Requirements
3.4.1 Real Time Accounting - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.4.2 Mandatory Compact Encoding - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.4.3 Accounting Record Extensibility - SNMP:T, RADIUS:T, Diameter:T,
COPS:T
3.4.4 Batch Accounting - SNMP:T, RADIUS:F, Diameter:P, COPS:P
Some members of the group are not sure how this fits into the rest of
the AAA protocol, which is primarly real-time and event driven. Would
this be better met with FTP?
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3.4.5 Guaranteed Delivery - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.4.6 Accounting Timestamps - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.4.7 Dynamic Accounting - SNMP:T, RADIUS:T, Diameter:T, COPS:T
3.5 MOBILE IP Requirements
3.5.1 Encoding of MOBILE IP Registration Messages - SNMP:T, RADIUS:T/P,
Diameter:T, COPS:T
3.5.2 Firewall Friendly - SNMP:F, RADIUS:T, Diameter:P, COPS:P
There was considerable discussion about what it means to be "firewall
friendly". It was suggested that not making the firewall look into
packets much beyond the application port number. Protocols such as SNMP
and COPS are at a disadvantage, as you must look far into the packet to
understand the intended operation. DIAMETER will have the disadvantage
of SCTP, which is not well deployed or recognized at the moment.
SNMP and COPS also have the problem that they are used for other types
of operations than just AAA.
Should firewalls have AAA Proxy engines?
We didn't look NAT friendly issues either.
3.5.3 Allocation of Local Home Agent - SNMP:F, RADIUS:P, Diameter:T,
COPS:T
The group is not clear on how this requirement impacts the actual proto-
col. Raj explained it to us, but we mostly took it on faith.
4. Protocol Evaluation Summaries
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4.1. SNMP
SNMP is generally not acceptable as a general AAA protocol. There may
be some utility in its use for accounting, but the amount of engineering
to turn it into a viable A&A protocol argues against further considera-
tion.
4.2. Radius++
Radius++ is not considered acceptable as an AAA protocol. There is a
fairly substantial amount of engineering required to make it meet all
requirements, and that engineering would most likely result in something
close to the functionality of Diameter.
4.3. Diameter
Diameter is considered acceptable as an AAA protocol. There is some
minor engineering required to bring it into complete compliance with the
requirements but well within short term capabilities. Diameter might
also benefit from the inclusion of a broader data model ala COPS.
4.4. COPS
COPS is considered acceptable as an AAA protocol. There is some minor
to medium engineering required to bring it into complete compliance with
the requirements.
4.5. Summary Recommendation
The panel expresses a slight preference for Diameter based on the per-
ception that the work for Diameter is further along than for COPS. How-
ever, using SCTP as the transport mechanism for Diameter places SCTP on
the critical path for Diameter. This may ultimately result in COPS being
a faster approach if SCTP is delayed in any way.
5. Security Considerations
AAA protocols enforce the security of access to the Internet. The
design of these protocols and this evaluation process took many security
requirements as critical issues for evaluation. A candidate protocol
must meet the security requirements as documented, and must be
engineered and reviewed properly as developed and deployed.
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6. References
[AAAReqts] "Criteria for Evaluating AAA Protocols for Network Access",
Aboba, et.al., draft-ietf-aaa-na-reqts-05.txt, April 2000
[AAAComp] "AAA Protocols : Comparison between RADIUS, DIAMETER and
COPS", Ekstein, T'Joens, Sales, Paridaens, draft-ekstein-nasreq-
protcomp-01.txt, Jan 2000
[SNMPComp] "Comparison of SNMPv3 Against AAA Network Access Require-
ments", Natale, draft-natale-aaa-snmpv3-comp-00.txt, June 2000
[RADComp] "Comparison of RADIUS Against AAA Network Access Require-
ments", Ekstein, T'Joens, DeVries draft-tjoens-aaa-radius-comp-
00.txt, May 2000
[RADExt] "Framework for the extension of the RADIUS(v2) protocol",
T'Joens, Ekstein, DeVries, draft-tjoens-aaa-radius-00.txt, June 2000
[DIAComp] "Comparison of DIAMETER Against AAA Network Access Require-
ments ", Calhoun, draft-calhoun-aaa-diameter-comp-00.txt, April 2000
[COPSComp] "Comparison of COPS Against the AAA NA Requirements", Khos-
ravi, Durham, Walker, draft-durham-aaa-cops-reqments-00.txt, May
2000
[COPSAAA] "COPS Usage for AAA", Durham, Khosravi, Weiss, Filename,
draft-durham-aaa-cops-ext-00.txt, Jun-2000
7. Author's Addresses
David Mitton
Nortel Networks
880 Technology Park Drive
Billerica, MA 01821
Phone: 978-288-4570
Email: dmitton@nortelnetworks.com
Michael StJohns
Excite@Home MS 430/3
450 Broadway
Redwood City, CA
Phone: 650-556-5368
Email: stjohns@corp.home.net
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Stuart Barkley
UUNET
F1-1-612
22001 Loudoun County Parkway
Ashburn, VA 20147 US
Phone: 703-886-5645
Email: stuartb@uu.net
David B. Nelson
Enterasys Networks, Inc. (a Cabletron Systems company)
50 Minuteman Road
Andover, MA 01810-1008
Phone: 978-684-1330
Email: dnelson@enterasys.com
Basavaraj Patil
Nokia
6000 Connection Dr.
Irving, TX 75039
Email: Basavaraj.Patil@nokia.com
Mark Stevens
Ellacoya Networks
7 Henry Clay Drive
Merrimack, NH 03054
Phone: 603-577-5544 ext. 325
Email: mstevens@ellacoya.com
Barney Wolff, Pres.
Databus Inc.
15 Victor Drive
Irvington, NY 10533-1919 USA
Phone: 914-591-5677
Email: barney@databus.com
8. Full Copyright Statement
Copyright (C) The Internet Society (July 2000). All Rights Reserved.
This document and translations of it may be copied and furnished to oth-
ers, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and
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distributed, in whole or in part, without restriction of any kind, pro-
vided that the above copyright notice and this paragraph are included on
all such copies and derivative works. However, this document itself may
not be modified in any way, such as by removing the copyright notice or
references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet Stan-
dards process must be followed, or as required to translate it into
languages other than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FIT-
NESS FOR A PARTICULAR PURPOSE."
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9. Appendix Summary Evaluations
Composite Results
SNMP Radius++ Diameter COPS
1.1.1 P P T T
1.1.2 P P P T/P
1.1.3 T T/P T T
1.1.4 T P T T
1.1.5 P P T T
1.1.6 F P T T
1.1.7 T T T T
1.1.8 P P T T
1.1.9 T T T T
1.1.10 P T T T
1.1.11 F P T P
1.1.12 F F T P
1.1.13 P/T T T T
1.1.14 T T T T
1.2.1 T T T T
1.2.2 T T T T
1.2.3 T T T T
1.2.4 T T T T
1.2.5 T P P T
1.2.6 P T/P T T
1.3.1 P/F T T T
1.3.2 P T T/P P
1.3.3 T/P/F T T P
1.3.4 F T T T
1.3.5 P/F P T/P T
1.3.6 P P P T/P
1.3.7 F P/F P T/P
1.3.8 T P T T
1.4.1 T T T T
1.4.2 T T T T
1.4.3 T T T T
1.4.4 T F P P
1.4.5 T T T T
1.4.6 T T T T
1.4.7 T T T T
1.5.1 T T/P T T
1.5.2 F T P P
1.5.3 F P T T
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10. Appendix Review of the Requirements
Comments from the Panel on draft-ietf-aaa-na-reqts-05.txt
5.1 General Requirements
Scalability - In clarification [a], delete "and tens of thousands of
simultaneous requests." This does not appear to be supported by any
of the three base documents.
Transmission level security - [Table] Delete the ROAMOPS "M" and
footnote "6". This appears to be an over generalization of the
roaming protocol requirement not necessarily applicable to AAA.
Data object confidentiality - [Table] Delete the MOBILE IP "S" and
footnote "33". The base document text does not appear to support this
requirement.
Reliable AAA transport mechanism - In clarification [h] delete
everything after the "...packet loss" and replace with a ".". The
requirements listed here are not necessarily supported by the base
document and could be mistakening taken as requirements for the AAA
protocol in their entirety.
Run over IPv4 - [Table] Replace the MOBILE IP footnote "17" with
footnote "33". This appears to be a incorrect reference.
Run over IPv6 - [Table] Replace the MOBILE IP footnote "18" with a
footnote pointing to section 8 of [8]. This appears to be an
incorrect reference.
Auditability - Clarification [j] does not appear to coincide with the
NASREQ meaning of Auditability. Given that NASREQ is the only
protocol with an auditability requirement, this section should be
aligned with that meaning.
Shared secret not required - [Table] General - This section is
misleadingly labeled. Our team has chosen to interpret it as
specified in clarification [k] rather than any of the possible
interpretations of "shared secret not required". We recommend the tag
in the table be replaced with "Dual App and Transport Security Not
Required" or something at least somewhat descriptive of [k]. Delete the
NASREQ "S" and footnote "28" as not supported by the NASREQ document.
Delete the MOBILE IP "O" and footnotes "34" and 39" as not supported
by the MOBILE IP document.
5.2 Authentication Requirements
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NAI Support - [Table] Replace MOBILE IP footnote "38" with "39". This
appears to be a more appropriate reference.
CHAP Support - [Table] Delete MOBILE IP "O" as unsupported.
EAP Support - [Table] Delete MOBILE IP "O" as unsupported.
PAP/Clear-Text Support - [Table] Replace NASREQ footnote "10" with
"26" as being more appropriate. Replace ROAMOPS "B" with "O". The
reference text appears to not explictly ban this and specifically
references clear text for OTP applications. Delete MOBILE IP "O" as
unsupported.
Re-authentication on demand - Clarification [e] appears to go beyond
the requirements in NASREQ and MOBILE IP. [Table] Delete MOBILE IP
footnote "30" as inapplicable.
Authorization Only without Authentication - Clarification [f] does not
include all NASREQ requirements, specifically that unneeded
credentials MUST NOT be required to be filled in. Given that there
are no other base requirements (after deleting the MOBILE IP
requirement) we recommend that clarification [f] be brought in line
with NASREQ. [Table] Delete MOBILE IP "O" and footnote "30". The
referenced text does not appear to support the requirement.
5.3 Authorization Requirements
Static and Dynamic... - Clarification [a] appears to use a
particularly strange definition of static and dynamic addressing.
Recommend clarification here identifying who (e.g. client or server)
thinks address is static/dynamic. [Table] ROAMOPS "M" appears to be a
derived requirement instead of directly called out. The footnote "1"
should be changed to "5" as being more appropriate. A text
clarification should be added to this document indentifying the
derived requirement.
RADIUS Gateway capability - [Table] Delete the MOBILE IP "O" and
footnote "30". The referenced text does not appear to support the
requirement.
Reject capability - [Table] Delete the NASREQ "M" and footnote "12".
The NASREQ document does not appear to require this cability.
Reauthorization on Demand - [Table] Delete the MOBILE IP "S" and
footnotes "30,33" The referenced text does not support this
requirement.
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Support for Access Rules... - Clarification [e] has a overbroad list
of requirements. NASREQ only requires 5-8 on the list, and as The MOBILE IP
requirement is not supported by its references, this clarification
should match NASREQ requirements. [Table] Delete the MOBILE
IP "O" and footnotes "30,37" as not supported.
State Reconciliaton - Clarification [f] should be brought in line with
NASREQ requirements. The clarification imposes overbroad requirements
not required by NASREQ and NASREQ is the only service with
requirements in this area.
5.4 Accounting Requirements
Real-Time accounting - [Table] Replace MOBILE IP footnote [39] with a
footnote pointing to section 3.1 of [3] as being more appropriate.
Mandatory Compact Encoding - [Table] Delete MOBILE IP "M" and footnote
"33" as the reference does not support the requirement.
Accounting Record Extensibility - [Table] Delete NASREQ "M" and
footnote "15" as the reference does not support the requirement.
Accounting Time Stamps - [Table] Delete MOBILE IP "S" and footnote
"30" as they don't support the requirement. Replace MOBILE IP
footnote "40" with a footnote pointing to section 3.1 of [3] as being
more appropriate.
Dynamic Accounting - [Table] Replace the NASREQ footnote "18" with a
footnote pointing to section 8.4.1.5 of [3]. Delete the MOBILE IP "S"
and footnote "30" as the reference does not support the requirement.
Footnote section.
[40] should be pointing to 6.1 of [4].
[41] should be pointing to 6.2.2 of [4].
[45] should be pointing to 6.4 of [4].
[46] should be pointing to 8 of [4].
11. Appendix Position Briefs
11.1. SNMP PRO Evaluation
Evaluation of SNMP AAA Requirements
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PRO Evaluation
Evaluator - Stuart Barkley
Ref [1] is draft-natale-aaa-snmpv3-comp-00.txt, aka 'the document'
Ref [2] is the aaa eval criteria as modified by us, aka 'the requirements'
The document uses T to indicate total compliance, P to indicate partial
compliance and F to indicate no compliance. For each section I've
indicated my grade for the section. If there is a change, I've
indicated that and the grade given by the authors.
1 Per item discussion
1.1 General Requirements
1.1.1 Scalability - Grade T
The document indicates that SNMP can adequately handle that scale from
the requirements document. Since most current uses are ppp connections
and SNMP is already capable of handling the interface table and other
per session tables it is clear that basic capacity exists. Additions to
support other tables and variables scales in a simple linear fashion
with the number of additional variables and protocol interactions.
Regardless of the final selected protocol handling the scaling required
is not a trivial undertaking. SNMP can draw upon existing network
management practices to assist in this implementation.
1.1.2 Fail-over - Grade T
SNMP is of vital importance to the operation of most networks.
Existing infrastructures can handle required failover or other redundant
operations.
1.1.3 Mutual Authentication - Grade T
The use of shared secrets described in the document is a well understood
method of integrity control. Although shared secrets don't necessarily
provide full authentication since other parties may also have the same
secrets, the level of authentication is sufficient for the task at hand.
In many cases the SNMP infrastructure will already exist and shared
secrets should already be properly managed on an operational network. A
failure of the SNMP shared secret approach regardless of the AAA
protocol will likely leave equipment and systems open to substantial
misuse bypassing any more elaborate AAA authentication.
1.1.4 Transmission Level Security - Grade T
SNMPv3 provides many additional security options which were not
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available or were more controversial in previous SNMP versions.
1.1.5 Data Object Confidentiality - New Grade P (from T)
The document discusses SNMPv3 which can provide data confidentially for
data passing over the wire. There is substantial implied AAA
architecture (brokers and proxies) in the requirements that full
conformance is difficult to determine. In particular, the evaluator has
difficulty with the concept of "the target AAA entity for whom the data
is ultimately destined", but will concede that the desired requirement
is only partially met (most especially with the transfer of a PAP
password).
1.1.6 Data Object Integrity - New Grade T (from P)
SNMP has full capabilities that allow the authentication of the data.
Brokers, proxies or other intermediaries in the data chain can verify
the source of the information and determine that the data has not been
tampered with. The document downgrades the grade to P because of
confusion over the integrity checking role of intermediaries.
1.1.7 Certificate Transport - Grade T
The requirements require the capability of transporting certificates but
do not have any specific use for the certificates. The requirements
make assumptions that the protocol selected will be dependent upon
certificates, but this is not necessarily true. SNMP can transport
arbitrary objects and can transport certificates if necessary. The
document indicates some issues with size of certificates and current
maximum practical data sizes, however if the compact encoding
requirement extends to the internal certificate information this should
be less of an issue.
1.1.8 Reliable AAA Transport - New Grade T (from P)
The requirements is stated rather strongly and makes substantial
assumptions of AAA protocol architecture and based upon current
protocols and their failings. SNMP allows for great flexibility in
retransmission schemes depending upon the importance of the data.
1.1.9 Run over IPv4 - Grade T
SNMP has operated in this mode for many years.
1.1.10 Run over IPv6 - New Grade T (from P)
SNMP must support IPv6 for many other systems so support for this should
be possible by the time the requirement becomes effective. The document
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indicates that experimental versions satisfying this requirement are
already in existence.
1.1.11 Support Proxy and Routing Brokers - New Grade T (from P)
The requirements make significant assumptions about the final
architecture. It is well within the capabilities of SNMP to provide
intermediaries which channel data flows between multiple parties. The
document downgrades SNMPs compliance with this requirement due to issues
which are covered more specifically under "Data Object Confidentially"
which the evaluator has downgraded to P.
1.1.12 Auditability - New Grade T (from F)
Data flows inside SNMP are easily auditable by having secondary data
flows established which provide copies of all information to auxiliary
servers. The document grades this as a failure, but this support is
only minor additions within a more fully fleshed out set of data flows.
1.1.13 Shared Secret Not Required - Grade T
Shared secrets are not required by SNMP. They are desirable in many
instances where a lower level does not provide the necessary
capabilities. The document supplies pointers to various security modes
available.
1.1.14 Ability to Carry Service Specific Attributes - Grade T
SNMP has long had the ability for other parties to create new
unambiguous attributes.
1.2 Authentication Requirements
1.2.1 NAI Support - Grade T
SNMP easily supports this. NAIs were defined to be easily carried in
existing protocols.
1.2.2 CHAP Support - Grade T
SNMP can easily provide objects to pass the necessary information for
CHAP operation.
1.2.3 EAP Support - New Grade T (from P)
SNMP can easily provide objects to pass the necessary information for
EAP operation. As with CHAP or PAP MIB objects can be created to
control this operation thus the upgrade from the document grade.
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1.2.4 PAP/Clear-text Passwords - New Grade P (from T)
SNMP can easily provide objects to pass the necessary information for
PAP operation. The requirement about non-disclosure of clear text
passwords make assumptions about the protocol implementation. The
choice to use clear text passwords is inherently insecure and forced
protocol architecture don't really cover this. This requirement grade
is downgraded to P (partial) because the document does not really
address the confidentially of the data at application proxies.
1.2.5 Reauthorization on demand - Grade T
SNMP can easily provide objects to control this operation.
1.2.6 Authorization w/o Authentication - New Grade T (from T)
The document makes an incorrect interpretation of this requirement.
However, SNMP makes no restriction which prevents to desired
requirements. No actual change of grade is necessary, since both the
actual requirements and the incorrect interpretation are satisfied by
SNMP.
1.3 Authorization Requirements
1.3.1 Static and Dynamic IP Addr Assignment - Grade T
SNMP can easily provide objects to control this operation.
1.3.2 RADIUS Gateway Capability - Grade T
As the document describes, with the addition of any necessary
compatibility variables SNMP can be gatewayed to RADIUS applications.
1.3.3 Reject Capability - Grade T
Any of the active components in the SNMP based structure could decide to
reject and authentication request for any reason. Due to mixing
different levels of requirements the document doesn't attempt to
directly address this, instead indicating that a higher level
application can cause this operation.
1.3.4 Preclude Layer 2 Tunneling - New Grade T (from ?)
Nothing in SNMP explicitly interacts with the selection of any tunneling
mechanisms the client may select. The document author was unclear about
the needs here.
1.3.5 Reauth on Demand - Grade T
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SNMP can easily provide objects to control this operation.
1.3.6 Support for ACLs - Grade T
The document indicates that should it be desired SNMP can provide
objects to control these operations. In addition, active components can
apply substantial further configurable access controls.
1.3.7 State Reconciliation - Grade T
The requirements describe an over broad set of required capabilities.
The document indicates concern over incompatibilities in the
requirements, however SNMP can provide methods to allow active
components to reacquire lost state information. These capabilities
directly interact with scalability concerns and care needs to be taken
when expecting this requirement to be met at the same time as the
scalability requirements.
1.3.8 Unsolicited Disconnect - Grade T
The document indicates that SNMP can easily provide objects to control
this operation.
1.4 Accounting Requirements
1.4.1 Real Time Accounting - Grade T
SNMP can provide this mode of operation. The document outlines methods
both fully within SNMP and using SNMP to interface with other transfer
methods. Many providers already use SNMP for real time notification of
other network events. This capability can directly interact with
scalability concerns and implementation care needs to be taken to make
this properly interact is large scale environments.
1.4.2 Mandatory Compact Encoding - Grade T
The document indicates the possibility of controlling external protocols
to handle data transmissions where the BER encoding of SNMP objects
would be considered excessive. SNMP BER encoded protocol elements are
generally in a fairly compact encoding form compared with text based
forms (as used in some existing radius log file implementations). This
interacts with the general requirement for carrying service specific
attributes and the accounting requirement for extensibility. With
careful MIB design and future work on SNMP payload compression the SNMP
coding overhead can be comparable with other less extensible protocols.
1.4.3 Accounting Record Extensibility - Grade T
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SNMP has a strong tradition of allowing vendor specific data objects to
be transferred.
1.4.4 Batch Accounting - Grade T
There are many methods which a SNMP based system could use for batch
accounting. The document discusses SNMP parameters to control the
batching process and indicates that certain existing MIBs contain
examples of implementation strategies. SNMP log tables can provide
accounting information which can be obtained in many methods not
directly related to real time capabilities. The underlying system
buffering requirements are similar regardless of the protocol used to
transport the information.
1.4.5 Guaranteed Delivery - Grade T
SNMP is very amenable to providing guaranteed delivery. Particularly in
a pull model (versus the often assumed push model) the data gatherer can
absolutely know that all data has been transfered. In the common push
model the data receiver does not know if the originator of the data is
having problems delivering the data.
1.4.6 Accounting Timestamps - Grade T
Timestamps are used for many SNMP based operations. The document points
at the DateAndTime textual convention which is available for use. As
with all environments the timestamps accuracy needs evaluation before
the information should be relied upon.
1.4.7 Dynamic Accounting - Grade T
As long as there is some way to relate multiple records together there
are no problems resolving multiple records for the same session. This
interacts with the scalability requirement and care must be taken when
implementing a system with both of these requirements.
1.5 MOBILE IP Requirements
1.5.1 Encoding of MOBILE IP Registration Messages - Grade T
SNMP can easily provide objects to transfer this information.
1.5.2 Firewall Friendly - New Grade T (from P)
SNMP is already deployed in many operational networks. SNMPv3 addresses
most concerns people had with the operation of previous versions. True
SNMPv3 proxies (as opposed to AAA proxies) should become commonplace
components in firewalls for those organizations which require firewalls.
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1.5.3 Allocation of Local Home Agent - New Grade T (from ?)
SNMP is not concerned with the LHA. This can be under control of the
Local network to meet its needs.
2. Summary Discussion
SNMP appears to meet most stated requirements. The areas where the SNMP
proposal falls short are areas where specific AAA architectures are
envisioned and requirements based upon that architecture are specified.
Scaling of the protocol family is vital to success of a AAA suite. The
SNMP protocol has proved scalable in existing network management and
other high volume data transfer operations. Care needs to be taken in
the design of a large scale system to ensure meeting the desired level
of service, but this is true of any large scale project.
3. General Requirements
SNMP is well understood and already supported in many ISP and other
operational environments. Trust models already exist in many cases and
can be adapted to provide the necessary access controls needed by the
AAA protocols. Important issues with previous versions of SNMP have
been corrected in the current SNMPv3 specification.
The SNMP proposal is silent on the specific data variables and message
types to be implemented. This is largely due to the requirements not
specifying the necessary data elements and the time constraints in
extracting that information from the base document set. Such a data
model is necessary regardless of the ultimate protocol selected.
4. Summary Recommendation
SNMP appears to fully meet all necessary requirements for the full AAA
protocol family.
11.2. SNMP CON Evaluation
Evaluation of SNMP AAA Requirements
CON Evaluation
Evaluator - Michael StJohns
Ref [1] is draft-natale-aaa-snmpv3-comp-00.txt, aka 'the document'
Ref [2] is the aaa eval criteria as modified by us.
The document uses T to indicate total compliance, P to indicate partial
compliance and F to indicate no compliance. For each section I've indicated
my grade for the section. If there is no change, I've indicated that and the
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grade given by the authors.
Section 1 - Per item discussion
1.1 General Requirements
1.1.1 Scalability - Although the document indicates compliance with
the requirement, its unclear how SNMP actually meets those
requirements. The document neither discusses how SNMP will scale,
nor provides applicable references. The argument that there is an
existence proof given the deployed SNMP systems appears to assume
that one manager contacting many agents maps to many agents
(running AAA) contacting one AAA server. A server driven system
has substantially different scaling properties than a client
driven system and SNMP is most definately a server (manager)
driven system. Eval - F
1.1.2 Fail-over - The document indicates the use of application level
time outs to provide this mechanism, rather than the mechanism
being a characteristic of the proposed protocol. The protocol
provides only partial compliance with the requirement. Eval - P
1.1.3 Mutual Authentication - There is some slight handwaving here,
but the protocol's USM mode should be able to support this
requirement. Eval - No Change (T)
1.1.4 Transmission Level Security - The authors should elaborate on
the specific use of the SNMPv3 modes to support these
requirements, but the text is minimally acceptable. Eval - No
Change (T)
1.1.5 Data Object Confidentiality - The authors describe a mechanism
which does not appear to completely meet the requirement. VACM is
a mechanism for an end system (agent) to control access to its
data based on manager characteristics. This mechanism does not
appear to map well to this requirement. Eval - P
1.1.6 Data Object Integrity - There appears to be some handwaving
going on here. Again, SNMP does not appear to be a good match to
this requirement due to at least in part a lack of a proxy
intermediary concept within SNMP. Eval - F
1.1.7 Certificate Transport - The document does indicate compliance,
but notes that optimization might argue for use of specialized
protocols. Eval - No Change (T)
1.1.8 Reliable AAA Transport - The document indicates some confusion
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with the exact extent of this requirement. Given the
modifications suggested by the eval group to the explanatory text
in [2] for the related annotation, the point by point explanatory
text is not required. The document does indicate that the use of
SNMP is irrespective of the underlying transport and the support
of this requirement is related at least partially to the choice of
transport. However, SNMP over UDP - the most common mode for SNMP
- does not meet this requirement. Eval - No Change (P)
1.1.9 Run over IPv4 - While the evaluator agrees that SNMPv3 runs over
V4, the authors need to point to some sort of reference. Eval -
No Change (T)
1.1.10 Run over IPv6 - The document indicates both experimental
implementations and future standardization of SNMPv3 over IPv6.
Eval - No Change (P)
1.1.11 Support Proxy and Routing Brokers - The section of the document
(5.5.3) that, by title, should have the discussion of SNMP proxy
is marked as TBD. The section notes that the inability to
completely comply with the data object confidentiality and
integrity requirements might affect the compliance of this section
and the evaluator agrees. Eval - F
1.1.12 Auditability - The document indicates no compliance with this
requirement. Eval - No Change (F)
1.1.13 Shared Secret Not Required - Slight handwaving here, but SNMPv3
does not necessarily require use of its security services if other
security services are available. However, the interaction with
VACM in the absence of USM is not fully described and may not have
good characteristics related to this requirement. Eval - P
1.1.14 Ability to Carry Service Specific Attributes - SNMP complies
via the use of MIBs. Eval - No Change (T)
1.2 Authentication Requirements
1.2.1 NAI Support - The document indicates that MIB objects can be
created to meet this requirement, but gives no further
information. Eval - P
1.2.2 CHAP Support - The document indicates that MIB objects can be
created to meet this requirement, but gives no further
information. Given the normal CHAP model, its unclear exactly how
this would work. Eval - F
1.2.3 EAP Support - The document notes that EAP payloads can be
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carried as specific MIB objects, but also notes that further
design work would be needed to fully incorporate EAP. Eval - No
Change (P)
1.2.4 PAP/Clear-text Passwords - The document notes the use of MIB
objects to carry the clear text passwords and the protection of
those objects under normal SNMPv3 security mechanisms. Eval - No
Change (T)
1.2.5 Reauthorization on demand - While there's some handwaving here,
its clear that the specific applications can generate the signals
to trigger reauthorization under SNMP. Eval - No Change (T)
1.2.6 Authorization w/o Authentication - The author appears to be
confusing the AAA protocol authorization with the AAA user
authorization and seems to be over generalizing the ability of
SNMP to deal with general AAA user authorization. Eval - F
1.3 Authorization Requirements
1.3.1 Static and Dynamic IP Addr Assignment - The reference to MIB
objects without more definite references or descriptions continues
to be a negative. While the evaluator agrees that MIB objects can
represent addresses, the document needs to at least lead the
reader in the proper direction. Eval - F
1.3.2 RADIUS Gateway Capability - The transport and manipulation of
Radius objects appears to be only a part of what is required.
Eval - P
1.3.3 Reject Capability - Again, a clarification of how SNMP might
accomplish this requirement would be helpful. The overall
document lacks a theory of operation for SNMP in an AAA role that
might have clarified the various approaches. Eval - F
1.3.4 Preclude Layer 2 Tunneling - Document indicates lack of
understanding of this requirement. Eval - F
1.3.5 Reauth on Demand - See response in 1.3.3 above. None of the text
responding to this requirement, nor any other text in the
document, nor any of the references describes the appropriate
framework and theory. Eval - F
1.3.6 Support for ACLs - The response text again references MIB
objects that can be defined to do this job. There is additional
engineering and design needed before this is a done deal. Eval -
P
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1.3.7 State Reconciliation - The text fails to address the basic
question of how to get the various parts of the AAA system back in
sync. Eval - F
1.3.8 Unsolicited Disconnect - Assuming that the NAS is an SNMP agent
for an AAA server acting as an SNMP manager the evaluator
concurs. Eval - No Change (T).
1.4 Accounting Requirements
1.4.1 Real Time Accounting - SNMP Informs could accomplish the
requirements. Eval - No Change (T)
1.4.2 Mandatory Compact Encoding - This is a good and reasonable
response. SNMP can vary the style and type of reported objects to
meet specific needs. Eval - No Change (T).
1.4.3 Accounting Record Extensibility - MIBs are extensible. Eval - No
Change (T)
1.4.4 Batch Accounting - MIBs provide data collection at various
times. Eval - No Change (T)
1.4.5 Guaranteed Delivery - There's some weasel wording here with
respect to what guaranteed means, but the description of
mechanisms does appear to meet the requirements. Eval - No Change (T)
1.4.6 Accounting Timestamps - Accounting records can use the
DateAndTime Textual Convention to mark their times. Eval - No
Change (T)
1.4.7 Dynamic Accounting - The author may have partially missed the
point on this requirement. While the number of records per
session is not of great interest, the delivery may be. The author
should go a little more into depth on this requirement. Eval - No
Change (T)
1.5 MOBILE IP Requirements
1.5.1 Encoding of MOBILE IP Registration Messages - Registration
messages can probably be encoded as SNMP messages. Eval - No
Change (T)
1.5.2 Firewall Friendly - There's a chicken and egg problem with the
response to the requirement in that the author hopes that SNMP as
an AAA protocol will encourage Firewall vendors to make SNMP a
firewall friendly protocol. Eval - F
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1.5.3 Allocation of Local Home Agent - The author disclaims an
understanding of this requirement. Eval - F
2. Summary Discussion
The documents evaluation score was substantially affected by a lack of any
document, reference or text which described a theory of operation for SNMP in
AAA mode. Of substantial concern are the items relating to the AAA server to
server modes and AAA client to server modes and the lack of a map to the SNMP
protocol for those modes.
The evaluator also notes that the scaling issues of SNMP in SNMP agent/manager
mode are in no way indicative of SNMP in AAA client/server mode. This has a
possibility to substantially impair SNMPs use in an AAA role.
However, SNMP may have a reasonable role in the Accounting space.
SNMP appears to map well with existing technology, and with the requirements.
3. General Requirements
SNMP appears to meet the general requirements of an IP capable protocol, but
may not have a proper field of use for all specific requirements.
4. Summary Recommendation
Recommended in Part. SNMP is NOT RECOMMENDED for use as either an
authentication or authorization protocol, but IS RECOMMENDED for use as an
accounting protocol.
11.3. RADIUS+ PRO Evaluation
Evaluation of RADIUS AAA Requirements
PRO Evaluation
Evaluator - Mark Stevens
Ref [1] is draft-tjoens-aaa-radius-comp-00.txt
Ref [2] is draft-tjoens-aaa-radius++-00.txt
Ref [3] is the aaa eval criteria as modified by us.
The documents uses T to indicate total compliance, P to indicate partial
compliance and F to indicate no compliance.
For each section I've indicated my grade for the section. I have
indicated whether or not my evaluation differs from the statements made
with respect to RADIUS++. The evaluation ratings as given below may
differ from the evaluations codified in the document refered to as
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draft-tjoens-aaa-radius-comp-00.txt without any indication.
1.1 General Requirements
1.1.1 [a] Scalability - In as much as a protocol's scalability can be
measured, the protocol seems to transmit information in a fairly
efficient manner.So, in that the protocol appears not to consume an
inordinate amount of bandwidth relative to the data it is transmitting,
this protocol could be considered scalable. However, the protocol has a
limit in the number of concurrent sessions it can support between
endpoints. Work arounds exist and are in use. Eval - P (no change)
1.1.2 [b] Fail-over - The document indicates the use of application
level time outs to provide this mechanism, rather than the mechanism
being a characteristic of the proposed protocol. The fail-over
requirement indicates that the protocol must provide the mechanism
rather than the application. The inplication is that the application
need not be aware that the fail-over and subsequent correction when it
happens. The application using the RADIUS++ protocol will be involved in
fail-over recovery activities. The protocol layer of the software does
not appear to have the capability built-in. Given the wording of the
requirement: Eval - P (changed from T)
1.1.3 [c] Mutual Authentication - The RADIUS++ protocol provides
shared-secret as a built-in facility for mutual authentication. The
authors of the document suggest the use of IPSec to obtain mutual
authentication functions. The RADIUS++ protocol provides no road blocks
to obtaining mutual authentication between instances of AAA
applications, however the protocol provides no facilities for doing so.
Eval - T (no change)
1.1.4 [d] Transmission Level Security - The RADIUS++ protocol provides
no transmission level security features, nor does it preclude the use of
IPSec to obtain transmission level security. Eval - P (no change)
1.1.5 [e] Data Object Confidentiality - The document describes a
RAIDUS++ message designed to server as an envelope in which encrypted
RADIUS messsages (attributes) may be enclosed. Eval - T (no change)
1.1.6 [f] Data Object Integrity - Using visible signatures, the RADIUS++
protocol appears to meet this requirement. Eval - T (no change)
1.1.7 [g] Certificate Transport - The document indicates compliance
through the use of the CMS-Data Radius Attribute (message). Eval - T
(no change)
1.1.8 [h] Reliable AAA Transport - The document points out that RADIUS++
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can be considered a reliable transport when augmeted with Layer 2
Tunneling Protocol. The protocol itself does not provide reliablility
features. Reliability remains the responsibility of the application or a
augmenting protocol. Eval - P (no change)
1.1.9 [i] Run over IPv4 - Eval - T (no change)
1.1.10 [j]Run over IPv6 - an IPv6 Address data type must be defined.
Eval - T (no change)
1.1.11[k] Support Proxy and Routing Brokers - There is no mechanism for
rerouting requests, but an extension can be made to do so. Eval - T (no
change)
1.1.12 [l] Auditability - The document indicates no compliance with this
requirement. Eval - F (no change)
1.1.13 [m] Shared Secret Not Required - RADIUS++ can be configured to
run with empty shared secret values. Eval - T (no change)
1.1.14 [n] Ability to Carry Service Specific Attributes - Vendor escape
mechanism can be used for this purpose.. Eval - T (no change)
1.2 Authentication Requirements
1.2.1 [a] NAI Support - Eval - T (no change)
1.2.2 [b] CHAP Support - Subject to dictionary attacks. Eval - P
(changed from T)
1.2.3 [c] EAP Support - Eval - T (no change)
1.2.4 [d] PAP/Clear-text Passwords - No end-to-end security, but
potential for encapsulation exists within current paradigm of the
protocol. - Eval -T (no change)
1.2.5 [e] Reauthentication on demand - The RADIUS protocol supports
re-authentication. In case re-authentication is initiated by the user
or AAA client, the AAA client can send a new authentication request.
Re-authentication can beinitiated from the visited or home AAA server by
sending a challenge message to the AAA client. Eval - T (no change)
1.2.6 [f] Authorization w/o Authentication - A new message type can be
created to enable RADIUS++ to support Aw/oA . Eval - T (no change)
1.3 Authorization Requirements
1.3.1[a] Static and Dynamic IP Addr Assignment - Both supported. IPv6
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would require the definition of a new address data type. Eval - P (no
change)
1.3.2 [b] RADIUS Gateway Capability - The transport and manipulation of
RADIUS objects appears to be only a part of what is required.
Reguirement seems to be worded to prclude RADIUS. Eval - P (changed from
T)
1.3.3 [c] Reject Capability - Eval -T
1.3.4 [d] Preclude Layer 2 Tunneling - I do not see a definition in the
AAA eval criteria document. Eval - ?
1.3.5 [e] Reauthorization on Demand - Implementation in the field
demonstrate that extensions to RADIUS can support the desired behaviour.
Re-authentication is currently coupled to re-authorization. Eval - P
(no change)
1.3.6 [f] Support for ACLs - Currently done in the applications behind
the RADIUS end points, not the within the protocol. RADIUS++ could
define additional message types to deal with expanded access control
within new service areas. Eval - P (no change)
1.3.7 [g] State Reconciliation - Eval - F (no change)
1.3.8 [h] Unsolicited Disconnect - RADIUS++ extensions to support. Eval
- T. (no change)
1.4 Accounting Requirements
1.4.1 [a] Real Time Accounting - Eval - T (no change)
1.4.2 [b] Mandatory Compact Encoding - Eval - T (no change)
1.4.3 [c] Accounting Record Extensibility - Eval - T (no change)
1.4.4 [d] Batch Accounting - RADIUS++ offers no new features to support
batch accounting. Eval - F No change)
1.4.5 [e] Guaranteed Delivery - Retransmission algorithm employed. Eval
- T (no change)
1.4.6 [f] Accounting Timestamps - RADIUS++ extensions support
timestamps. Eval - T (no change)
1.4.7 [g] Dynamic Accounting - RADIUS++ extensions to support. Eval - T
(no change)
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1.5 MOBILE IP Requirements
1.5.1 [a] Encoding of MOBILE IP Registration Messages - RADIUS++
extensions can be made to include registration messages as an opaque
payload. Eval - T (no change)
1.5.2 [b] Firewall Friendly - RADIUS is known to be operational in
environments where firewalls acting as a proxy are active. Eval - T (no
change)
1.5.3 [c] Allocation of Local Home Agent -Requirement statement needs
som clarfication and refinement. Eval - F (no change)
2. Summary Discussion
The RADIUS protocol, and its associated extensions, is presently not
fully compliant with the AAA Network Access requirements. However, it
is possible with a small effort to extend present procedures to meet
the requirements as listed in, while maintaining a high level of
interoperability with the wide deployment and installed base of
RADIUS clients and servers.
3. General Requirements
RADIUS++ the protocol and the application meet the majority of the
requirements and can be extended to meet the requirements where
necessary.
4. Summary Recommendation
RADIUS++ as it could be developed would provide a level of backward
compatibility that other protocols cannot achieve. By extending RADIUS
in the simple ways described in the documents listed above, the
transistion from existing RADIUS-based installations to RADIUS++
installations would be easier. Although accounting continues to be
weaker than other approaches, the protocol remains a strong contender
for continued use in the areas of Authorization and Authentication.
11.4. RADIUS+ CON Evaluation
Evaluation of RADIUS++ (sic) AAA Requirements CON Evaluation
Evaluator - David Nelson
Ref [1] is draft-tjoens-aaa-radius-comp-00.txt, a.k.a. 'the document'
Ref [2] is draft-tjoens-aaa-radius-00.txt, a.k.a. 'the protocol'
Ref [3] is the AAA evaluation criteria as modified by us.
Ref [4] is draft-ietf-radius-ext-07.txt.
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Ref [5] is draft-ietf-radius-x509-00.txt. (expired)
Ref [6] is draft-ietf-radius-tunnel-auth-09.txt.
The document uses T to indicate total compliance, P to indicate partial
compliance and F to indicate no compliance.
Evaluator's Note: The document [1] pre-dates the protocol [2]. It is
clear from reading [2], that some of the issues identified as short
comings in [1] are now addressed in [2]. The evaluator has attempted to
take note of these exceptions, where they occur.
Section 1 - Per item discussion
1.1 General Requirements
1.1.1 Scalability - The document [1] indicates partial compliance,
largely in deference to the "tens of thousands of simultaneous
requests" language in [3], that has been deprecated. The issue
of simultaneous requests from a single AAA client is addressed in
[1], indicating that the apparent limitation of 256 uniquely
identifiable outstanding request can be worked around using well
known techniques, such as the source UDP port number of the
request. The document claims "P", and the evaluator concurs.
1.1.2 Fail-over - The document [1] indicates the use of application
level time outs to provide the fail-over mechanism. Since the
AAA protocol is indeed an application-layer protocol, this seems
appropriate. There are significant issues of how to handle fail-
over in a proxy-chain environment that have not been well
addressed, however. The document claims "T", and the evaluator
awards "P".
1.1.3 Mutual Authentication - The document [1] indicates that mutual
authentication exists in the presence of a User-Password or
CHAP-Password attribute in an Access-Request packet or the
Message-Authenticator [4] in any packet. Once again, this
addresses hop-by-hop authentication of RADIUS "peers", but does
not fully address proxy-chain environments, in which trust models
would need to be established. The document further indicates
that strong mutual authentication could be achieved using the
facilities of IPsec. This claim would apply equally to all
potential AAA protocols, and cannot be fairly said to be a
property of the protocol itself. The document claims "T", and
the evaluator awards "F".
1.1.4 Transmission Level Security - The document [1] indicates that
transmission layer security, as defined in [3], is provided in
the protocol, using the mechanisms described in section 1.1.3.
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It should be noted that this requirement is now a SHOULD in [3].
The document claims "P", and the evaluator concurs.
1.1.5 Data Object Confidentiality - The document [1] indicates that
end-to-end confidentiality is not available in RADIUS, but goes on
to say that it could be added. The protocol [2] actually makes an
attempt to specify how this is to be done, in section 4.3.2.2 of
[2], using a CMS-data attribute, based in large part upon RFC 2630.
The evaluator has not, at this time, investigated the applicability
of RFC 2630 to the AAA work. The document claims "F", but in light
of the specifics of the protocol [2], the evaluator awards "P".
1.1.6 Data Object Integrity - The document [1] indicates that
end-to-end integrity is not available in RADIUS, but goes on
to say that it could be added. The protocol [2] actually makes
an attempt to specify how this is to be done, in section 4.3.2.1
of [2], using a CMS-data attribute, based in large part upon RFC
2630. The evaluator has not, at this time, investigated the
applicability of RFC 2630 to the AAA work. The document claims
"F", but in light of the specifics of the protocol [2], the
evaluator awards "P".
1.1.7 Certificate Transport - The document [1] indicates that
certificate transport is not available in RADIUS, but goes on
to say that it could be added. The protocol [2] actually makes
an attempt to specify how this is to be done, in section 4.3.2.3
of [2], using a CMS-data attribute, based in large part upon RFC
2630. The evaluator has not, at this time, investigated the
applicability of RFC 2630 to the AAA work. Other relevant work
in the area of certificate support in RADIUS may be found in an
expired internet draft "RADIUS X.509 Certificate Extensions" [5].
The document claims "F", but in light of the specifics of the
protocol [2], the evaluator awards "P".
1.1.8 Reliable AAA Transport - The document [1] indicates that RADIUS
provides partial compliance with the requirements of the original
AAA requirements document. However, in [3], the requirement has
been simplified to "resilience against packet loss". Once again,
the evaluator finds that the protocol [2] meets this criteria on a
hop-by-hop basis, but fails to effectively address these issues in
a proxy-chain environment. The document claims "P", and the
evaluator awards "F".
1.1.9 Run over IPv4 - RADIUS is widely deployed over IPv4. The
document claims "T", and the evaluator concurs.
1.1.10 Run over IPv6 - The document [1] indicates that adoption of
a limited number of new RADIUS attributes to support IPv6 is
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straightforward. Such discussion has transpired on the RADIUS WG
mailing list, although that WG is in the process of shutting down.
The document claims "P", and the evaluator concurs.
1.1.11 Support Proxy and Routing Brokers - The document [1] indicates
that RADIUS is widely deployed in proxy-chains of RADIUS servers.
This is equivalent to the Proxy Broker case, but the Routing
Broker case is a different requirement. The protocol [2] does not
describe any detail of how a Routing Broker might be accommodated,
although it opens the door by indicating that the RADIUS++ protocol
is peer-to-peer, rather than client/server. The document claims
"P", and the evaluator awards "F".
1.1.12 Auditability - The document [1] indicates no compliance with
this requirement. The document claims "F", and the evaluator
concurs.
1.1.13 Shared Secret Not Required - The document [1] indicates that
RADIUS may effectively skirt the requirement of application-layer
security by using a value of "zero" for the pre-shared secret.
While this is a bit creative, it does seem to meet the requirement.
The document claims "T" and the evaluator concurs.
1.1.14 Ability to Carry Service Specific Attributes - RADIUS has a well
defined Vendor-Specific Attribute, which, when properly used, does
indeed provide for the ability to transport service-specific
attributes. The document claims "T", and the evaluator concurs.
1.2 Authentication Requirements
1.2.1 NAI Support - The document [1] indicates that RADIUS specifies
the NAI as one of the suggested formats for the User-Name
attribute. The document claims "T", and the evaluator agrees.
1.2.2 CHAP Support - CHAP support is widely deployed in RADIUS. The
document claims "T", and the evaluator concurs.
1.2.3 EAP Support - The document [1] indicates that EAP support in
RADIUS is specified in [4]. The document claims "T", and the
evaluator concurs.
1.2.4 PAP/Clear-text Passwords - The document indicates that RADIUS
provides protection of clear-text passwords on a hop-by-hop basis.
The protocol [2] indicates how additional data confidentiality
may be obtained in section 4.3.2.2 of [2], using a CMS-data
attribute, based in large part upon RFC 2630. The evaluator has
not, at this time, investigated the applicability of RFC 2630 to
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the AAA work. The document claims "F", but in light of the
specifics of the protocol [2], the evaluator awards "P".
1.2.5 Reauthentication on demand - The document [1] indicates that
RADIUS may accomplish re-authentication on demand by means of an
Access-Challenge message sent from a server to a client. The
evaluator disagrees that this is likely to work for a given
session once an Access-Accept message has been received by the
client. The document claims "T", and the evaluator awards "F".
1.2.6 Authorization w/o Authentication - This requirement, as
applied to the protocol specification, mandates that non-
necessary authentication credentials not be required in a
request for authorization. The actual decision to provide
authorization in the absence of any authentication resides in
the application (e.g. AAA server). RADIUS does require some form
of credential in request messages. The document [1] claims "F",
and the evaluator concurs.
1.3 Authorization Requirements
1.3.1 Static and Dynamic IP Addr Assignment - The document [1]
indicates that RADIUS can assign IPv4 addresses, and can easily
be extended to assign IPv6 addresses (see section 1.1.10).
Of greater concern, however, is the issue of static vs. dynamic
addresses. If dynamic address has the same meaning as it does
for DHCP, then there are issues of resource management that RADIUS
has traditionally not addressed. The document claims "P", and
the evaluator concurs.
1.3.2 RADIUS Gateway Capability - The document [1] maintains that a
RADIUS++ to RADIUS gateway is pretty much a tautology. The
document claims "T", and the evaluator concurs.
1.3.3 Reject Capability - The document [1] maintains that RADIUS Proxy
Servers, and potentially RADIUS++ Routing Brokers, have the ability
to reject requests based on local policy. The document claims "T"
and the evaluator concurs.
1.3.4 Preclude Layer 2 Tunneling - The document [1] indicates that [6]
defines support for layer two tunneling in RADIUS. The document
claims "T", and the evaluator concurs.
1.3.5 Reauth on Demand - The document [1] indicates that RADIUS provides
this feature by means of the Session-Timeout and Termination-
Action attributes. While this may, in fact, be sufficient to
provide periodic re-authorization, it would not provide re-
authorization on demand. The protocol [2] does not address this
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further. The document claims "P", and the evaluator awards "F".
1.3.6 Support for ACLs - The document [1] describes the attributes in
RADIUS that are used to convey the access controls described in [3].
Certain of these (e.g. QoS) are not currently defined in RADIUS, but
could easily be defined as new RADIUS attributes. The document
claims "P", and the evaluator concurs.
1.3.7 State Reconciliation - The document [1] addresses each of the sub-
items, as listed in the original AAA requirements document. In
reviewing the document against the modified requirements of [3],
there is still an issue with server-initiated state reconciliation
messages. While the protocol [2] makes provision for such messages,
as servers are allowed to initiate protocol dialogs, no detailed
message formats are provided. This is an area that has traditionally
been a short coming of RADIUS. The document claims "P", and the
evaluator awards "F".
1.3.8 Unsolicited Disconnect - Much of the discussion from the previous
section applies to this section. The document [1] claims "F", and
the evaluator concurs.
1.4 Accounting Requirements
1.4.1 Real Time Accounting - RADIUS Accounting is widely deployed and
functions within the definition of real time contained in [3]. The
document [1] claims "T", and the evaluator concurs.
1.4.2 Mandatory Compact Encoding - RADIUS Accounting contains TLVs for
relevant accounting information, each of which is fairly compact.
Note that the term "bloated" in [3] is somewhat subjective. The
document [1] claims "T", and the evaluator concurs.
1.4.3 Accounting Record Extensibility - RADIUS Accounting may be
extended by means of new attributes or by using the Vendor-Specific
attribute. While it has been argued that the existing attribute
number space is too small for the required expansion capabilities,
the protocol [2] addresses this problem in section 3.0, and its
subsections, of [2]. The document [1] claims "T", and the evaluator
concurs.
1.4.4 Batch Accounting - RADIUS has no explicit provisions for batch
accounting, nor does the protocol [2] address how this feature might
be accomplished. The document [1] claims "F", and the evaluator
concurs.
1.4.5 Guaranteed Delivery - RADIUS Accounting is widely deployed and
provides guaranteed delivery within the context of the required
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application-level acknowledgement. The document [1] claims "T",
and the evaluator concurs.
1.4.6 Accounting Timestamps - The document [1] indicates that this
feature is specified in [4] as the Event-Timestamp attribute. The
document claims "T", and the evaluator concurs.
1.4.7 Dynamic Accounting - The document [1] indicates that this
requirement is partially met using the accounting interim update
message as specified in [4]. In addition, there was work in the
RADIUS WG regarding session accounting extensions that has not been
included in [4], i.e. some expired internet drafts. The document
claims "P", and the evaluator concurs.
1.5 MOBILE IP Requirements
1.5.1 Encoding of MOBILE IP Registration Messages - The document [1]
claims "F", and the evaluator concurs.
1.5.2 Firewall Friendly - The document [1] indicates that RADIUS
deployment is know to have occurred in fire-walled environments.
The document claims "T", and the evaluator concurs.
1.5.3 Allocation of Local Home Agent - The document [1] claims "F",
and the evaluator concurs.
2. Summary Discussion
The document [1] and the protocol [2] suffer from having been written in
a short time frame. While the protocol does provide specific guidance
on certain issues, citing other relevant documents, it is not a polished
protocol specification, with detailed packet format diagrams. There is a
pool of prior work upon which the RADIUS++ protocol may draw, in that
many of the concepts of DIAMETER were first postulated as internet
drafts within the RADIUS WG, in an attempt to "improve" the RADIUS
protocol. All of these internet drafts have long since expired,
however.
3. General Requirements
RADIUS++ meets many of the requirements of an AAA protocol, as it is the
current de facto and de jure standard for AAA. There are long-standing
deficiencies in RADIUS, which have been well documented in the RADIUS
and NASREQ WG proceedings. It is technically possible to revamp RADIUS
to solve these problems. One question that will be asked, however, is:
"What significant differences would there be between a finished RADIUS++
protocol and the DIAMETER protocol?".
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4. Summary Recommendation
Recommended in part. What may possibly be learned from this submission
is that it is feasible to have a more RADIUS-compliant
RADIUS-compatibility mode in DIAMETER.
David B. Nelson, Software Engineer V
Enterasys Networks, Inc. (a Cabletron Systems company) 50 Minuteman Road
Andover, MA 01810-1008
(978) 684-1330
dnelson@enterasys.com
11.5. DIAMETER PRO Evaluation
Evaluation of DIAMETER against the AAA Requirements PRO Evaluation
Evaluator - Basavaraj Patil
Ref [1] draft-calhoun-diameter-framework-07.txt
Ref [2] draft-calhoun-diameter-nasreq-03.txt
Ref [3] is the AAA evaluation criteria as modified by us.
Ref [4] draft-calhoun-diameter-accounting-05.txt
Ref [5] draft-calhoun-diameter-mobileip-08.txt
Ref [6] draft-calhoun-diameter-15.txt
Ref [7] draft-calhoun-diameter-strong-crypto-03.txt
Ref [8] draft-calhoun-aaa-diameter-comp-00.txt
The document uses T to indicate total compliance, P to indicate
partial compliance and F to indicate no compliance.
Evaluator's note : The DIAMETER compliance document [8] claims Total
"T" compliance with all the requirements except : - 1.2.5 - 1.5.2
------------------------------------------------------------------------
Section 1 - Per item discussion
1.1 General Requirements
1.1.1 Scalability
DIAMETER is an evolution of RADIUS and has taken into consideration
all the lessons learned over many years that RADIUS has been in
service. The use of SCTP as the transport protocol reduces the need
for multiple proxy servers (Sec 3.1.1 Proxy Support of [1]) as well as
removing the need for application level acks. The use and support of
forwarding and redirect brokers enhances scalability. Evaluator
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concurs with the "T" compliance on this requirement.
1.1.2 Fail-over
Again with the use of SCTP DIAMETER is able to detect disconnect
indications upon which it switches to an alternate server (Sec 4.0
[6]). Also Requests and Responses do not have to follow the same path
and this increases the reliability. Evaluator concurs with the "T"
compliance on this requirement.
1.1.3 Mutual Authentication
The compliance document quotes the use of symmetric transforms for
mutual authentication between the client and server (Sec 7.1 of [6]).
The use of IPSec as an underlying security mechanism and thereby use
the characteristic of IPSec itself to satisfy this requirement is also
quoted. Evaluator concurs with the "T" compliance on this requirement.
1.1.4 Transmission Level Security
Although this requirement has been deprecated by the AAA evaluation
team the document complies with it based on the definition (refering
to hop-by-hop security). Section 7.1 of [6] provides the details of
how this is accomplished in DIAMETER. Evaluator concurs with the "T"
compliance on this requirement.
1.1.5 Data Object Confidentiality
This requirement seems to have come from DIAMETER. Ref [7] explains in
detail the use of Cryptographic Message Sytnatx (CMS) to achieve data
object confidentiality. A CMS-Data AVP is defined in [7]. Evaluator
concurs with the "T" compliance on this requirement.
1.1.6 Data Object Integrity
Using the same argument as above and the hop-by-hop security feature
in the protocol this requirement is completely met by DIAMETER.
Evaluator concurs with the "T" compliance on this requirement.
1.1.7 Certificate Transport
Again with the use of the CMS-Data AVP, objects defined as these types
of attributes allow the transport of certificates. Evaluator concurs
with the "T" compliance on this requirement.
1.1.8 Reliable AAA Transport
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DIAMETER recommends that the protocol be run over SCTP. SCTP provides
the features described for a reliable AAA transport. Although the
compliance is not a perfect fit for the definition of this tag item,
it is close enough and the functionality achieved by using SCTP is the
same. Evaluator concurs with the "T" compliance on this requirement.
1.1.9 Run over IPv4
Is an application layer protocol and does not depend on the underlying
version of IP. Evaluator concurs with the "T" compliance on this
requirement.
1.1.10 Run over IPv6
Is an application layer protocol and does not depend on the underlying
version of IP. Evaluator concurs with the "T" compliance on this
requirement.
1.1.11 Support Proxy and Routing Brokers
Section 3.1.1/2 of the framework document [1] provides an explanation
of how DIAMETER supports proxy and routing brokers. In fact it almost
appears as though the requirement for a routing broker came from
DIAMETER. Evaluator concurs with the "T" compliance on this
requirement.
1.1.12 Auditability
With the use of CMS-Data AVP [7] a trail is created when proxies are
involved in the transaction. This trail can provide auditability.
Evaluator concurs with the "T" compliance on this requirement.
1.1.13 Shared Secret Not Required
With the use of IPSec as the underlying security mechanism, DIAMETER
does not require the use of shared secrets for message authentication.
Evaluator concurs with the "T" compliance on this requirement.
1.1.14 Ability to Carry Service Specific Attributes
The base protocol [6] is defined by DIAMETER and any one else can
define specific extensions on top of it. Other WGs in the IETF can
design an extension on the base protocol with specific attributes and
have them registered by IANA. Evaluator concurs with the "T" compliance
on this requirement.
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------------------------------------------------------------------------
1.2 Authentication Requirements
1.2.1 NAI Support
The base protocol [6] defines an AVP that can be used to support NAIs.
DIAMETER goes one step further by doing Message forwarding based on
destination NAI AVPs. Evaluator concurs with the "T" compliance on this
requirement.
1.2.2 CHAP Support
Reference [2] section 3.0 describes the support for CHAP.
Evaluator concurs with the "T" compliance on this requirement.
1.2.3 EAP Support
Reference [2] section 4.0 describes the support for EAP.
Evaluator concurs with the "T" compliance on this requirement.
1.2.4 PAP/Clear-text Passwords
Reference [2] section 3.1.1.1 describes the support for PAP.
Evaluator concurs with the "T" compliance on this requirement.
1.2.5 Reauthentication on demand
The use of Session-Timeout AVP as the mechanism for reauthentication
is claimed by the compliance document. However no direct references
explaining this in the base protocol [6] document were found.
Evaluator deprecates the compliance on this to a "P"
Note: However this is a trivial issue.
1.2.6 Authorization w/o Authentication
DIAMETER allows requests to be sent without having any authentication
information included. A Request-type AVP is defined in [2] and it can
specify authorization only without containing any authentication.
Evaluator concurs with the "T" compliance on this requirement.
------------------------------------------------------------------------
1.3 Authorization Requirements
1.3.1 Static and Dynamic IP Addr Assignment
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The base protocol includes an AVP for carrying the address. References
[6.2.2 of 2] and [4.5 of 5] provide detailed explanations of how this
can be done. Evaluator concurs with the "T" compliance on this
requirement.
1.3.2 RADIUS Gateway Capability
One of the basic facets of DIAMETER is to support backward
compatibility and act as a RADIUS gateway in certain environments.
Evaluator concurs with the "T" compliance on this requirement.
1.3.3 Reject Capability
Based on the explanation provided in the compliance document for this
requirement evaluator concurs with the "T" compliance on this
requirement.
1.3.4 Preclude Layer 2 Tunneling
Ref [2] defines AVPs supporting L2 tunnels Evaluator concurs with the
"T" compliance on this requirement.
1.3.5 Reauth on Demand
A session timer defined in [6] is used for reauthorization. However
DIAMETER allows reauthorization at any time. Since this is a
peer-to-peer type of protocol any entity can initiate a
reauthorization request. Evaluator concurs with the "T" compliance on
this requirement.
1.3.6 Support for ACLs
DIAMETER defines two methods. One that supports backward compatibility
for RADIUS and another one with the use of a standard AVP with the
filters encoded in it. Evaluator concurs with the "T" compliance on
this requirement.
1.3.7 State Reconciliation
A long explanation on each of the points defined for this tag item in
the requirements document. Evaluator concurs with the "T" compliance
for this requirement.
1.3.8 Unsolicited Disconnect
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The base protocol [6] defines a set of session termination messages
which can be used for unsolicited disconnects. Evaluator concurs with
the "T" compliance on this requirement.
------------------------------------------------------------------------
1.4 Accounting Requirements
1.4.1 Real Time Accounting
Evaluator concurs with the "T" compliance based on explanations in [4].
1.4.2 Mandatory Compact Encoding
Use of Accounting Data Interchange Format (ADIF)-Record-AVP for
compact encoding of accounting data. Evaluator concurs with the "T"
compliance.
1.4.3 Accounting Record Extensibility
ADIF can be extended.
Evaluator concurs with the "T" compliance.
1.4.4 Batch Accounting
Sec 1.2 of [4] provides support for batch accounting.
1.4.5 Guaranteed Delivery
Sections 2.1/2 of [4] describe messages that are used to guarantee
delivery of accounting records. Evaluator concurs with the "T"
compliance.
1.4.6 Accounting Timestamps
Timestamp AVP [6] is present in all accounting messages.
Evaluator concurs with the "T" compliance.
1.4.7 Dynamic Accounting
Interim accounting records equivalent to a call-in-progress can be
sent periodically. Evaluator concurs with the "T" compliance.
------------------------------------------------------------------------
1.5 MOBILE IP Requirements
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1.5.1 Encoding of MOBILE IP Registration Messages
Ref [5] provides details of how DIAMETER can encode MIP messages.
Evaluator concurs with the "T" compliance.
1.5.2 Firewall Friendly
Some handwaving here and a possible way of solving the firewall
problem with a DIAMETER proxy server. Document claims "T", evaluator
deprecates it to a "P" 1.5.3 Allocation of Local Home Agent
DIAMETER can assign a local home agent in a visited network in
conjunction with the FA in that network. Evaluator concurs with the "T"
compliance.
------------------------------------------------------------------------
Summary Recommendation
----------------------
DIAMETER is strongly recommended as the AAA protocol. The experience
gained from RADIUS deployments has been put to good use in the design
of this protocol. It has also been designed with extensibility in mind
thereby allowing different WGs to develop their own specific extension
to satisfy their requirements. With the use of SCTP as the transport
protocol, reliability is built in. Security has been addressed in the
design of the protocol and issues that were discovered in RADIUS have
been fixed. DIAMETER also is a session based protocol which makes it
more scalable. The suppport for forwarding and redirect brokers is well
defined and this greatly improves the scalability aspect of the
protocol.
Lastly the protocol has been implemented by at least a few people and
interop testing done. This in itself is a significant step and a
positive point for DIAMETER to be the AAA protocol.
Basavaraj Patil
Nokia
6000 Connection Dr.
Irving, TX 75039
11.6. DIAMETER CON Evaluation
Diameter CON Brief
Evaluator: Barney Wolff
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Section 1 - Per item discussion
1.1 General Requirements
1.1.1 Scalability - P (was T) The evaluator is concerned with
scalability to the small, not to the large. DIAMETER/SCTP may prove
difficult to retrofit to existing NAS equipment.
1.1.2 Fail-over - P (was T) SCTP gives an indication of peer failure,
but nothing in any DIAMETER or SCTP document the evaluator was able to
find even mentions how or when to switch back to a primary server to
which communication was lost. After a failure, the state machines end
in a CLOSED state and nothing seems to trigger exit from that state. It
was not clear whether a server, on rebooting, would initiate an SCTP
connection to all its configured clients. If not, and in any case when
the communication failure was in the network rather than in the server,
the client must itself, after some interval, attempt to re-establish
communication. But no such guidance is given.
Of course, the requirement itself fails to mention the notion of
returning to a recovered primary. That is a defect in the requirement.
The evaluator has had unfortunate experience with a vendor's RADIUS
implementation that had exactly the defect that it often failed to
notice recovery of the primary.
1.1.3 Mutual Authentication - T
1.1.4 Transmission Level Security - T
1.1.5 Data Object Confidentiality - P (was T). Yes, the CMS data type
is supported. But draft-calhoun-diameter-strong-crypto-03.txt says:
Given that asymmetric transform operations are expensive, DIAMETER
servers MAY wish to use them only when dealing with inter-domain
servers, as shown in Figure 3. This configuration is normally
desirable since DIAMETER entities within a given administrative
domain MAY inherently trust each other. Further, it is desirable to
move this functionality to the edges, since NASes do not necessarily
have the CPU power to perform expensive cryptographic operations.
Given all the fuss that has been made about "end-to-end" confidentiality
(which really means "NAS-to-home_server"), the evaluator finds it absurd
that the proposed solution is acknowledged to be unsuited to the NAS.
1.1.6 Data Object Integrity - P (was T). See above.
1.1.7 Certificate Transport - T
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1.1.8 Reliable AAA Transport - T
1.1.9 Run over IPv4 - T
1.1.10 Run over IPv6 - T
1.1.11 Support Proxy and Routing Brokers - T
1.1.12 Auditability - T (based on our interpretation as non-repudiation,
rather than the definition given in reqts)
1.1.13 Shared Secret Not Required - T
1.1.14 Ability to Carry Service Specific Attributes - T
1.2 Authentication Requirements
1.2.1 NAI Support - T
1.2.2 CHAP Support - T
1.2.3 EAP Support - T
1.2.4 PAP/Clear-text Passwords - T
1.2.5 Reauthentication on demand - P (was T). No mechansim was evident
for the server to demand a reauthentication, based for example on
detection of suspicious behavior by the user. Session-timeout is not
sufficient, as it must be specified at the start.
1.2.6 Authorization w/o Authentication - T
1.3 Authorization Requirements
1.3.1 Static and Dynamic IP Addr Assignment - T
1.3.2 RADIUS Gateway Capability - P (was T). RADIUS has evolved from
the version on which DIAMETER was based. EAP is a notable case where
the convention that the DIAMETER attribute number duplicates the RADIUS
one is violated. No protocol, not even RADIUS++, can claim a T on this.
1.3.3 Reject Capability - T (The evaluator fails to understand how any
AAA protocol could rate anything other than T on this.)
1.3.4 Preclude Layer 2 Tunneling - T
1.3.5 Reauth on Demand - P (was T). As with reauthentication, there is
no evident mechanism for the server to initiate this based on conditions
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subsequent to the start of the session.
1.3.6 Support for ACLs - P (was T). The evaluator finds the Filter-Rule
AVP laughably inadequate to describe filters. For example, how would it
deal with restricting SMTP to a given server, unless all IP options are
forbidden so the IP header length is known? No real NAS could have such
an impoverished filter capability, or it would not survive as a product.
1.3.7 State Reconciliation - P (was T). It is difficult for the
evaluator to understand how this is to work in a multi-administration
situation, or indeed in any proxy situation. Furthermore, SRQ with no
session-id is defined to ask for info on all sessions, not just those
"owned" by the requester.
1.3.8 Unsolicited Disconnect - T
1.4 Accounting Requirements
1.4.1 Real Time Accounting - T
1.4.2 Mandatory Compact Encoding - T
1.4.3 Accounting Record Extensibility - T
1.4.4 Batch Accounting - P (was T). The evaluator suspects that simply
sending multiple accounting records in a single request is not how batch
accounting should or will be done.
1.4.5 Guaranteed Delivery - T
1.4.6 Accounting Timestamps - T (The evaluator notes with amusement
that NTP time cycles in 2036, not 2038 as claimed in the DIAMETER
drafts. It's Unix time that will set the sign bit in 2038.)
1.4.7 Dynamic Accounting - T
1.5 MOBILE IP Requirements
1.5.1 Encoding of MOBILE IP Registration Messages - T
1.5.2 Firewall Friendly - F (was T). Until such time as firewalls are
extended to know about or proxy SCTP, it is very unlikely that SCTP will
be passed. Even then, the convenient feature of being able to send a
request from any port, and get the reply back to that port, means that a
simple port filter will not be sufficient, and statefulness will be
required. Real friendship would require that both source and dest ports
be 1812.
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1.5.3 Allocation of Local Home Agent - T
2. Summary Discussion
In some areas, DIAMETER is not completely thought through. In general,
real effort has gone into satisfying a stupendous range of requirements.
3. General Requirements
DIAMETER certainly fails the KISS test. With SCTP, the drafts add up to
382 pages - well over double the size of RADIUS even with extensions.
The evaluator sympathizes with the political instinct when faced with a
new requirement no matter how bizarre, to say "we can do that" and add
another piece of filagree. But the major places where DIAMETER claims
advantage over RADIUS, namely "end-to-end" confidentiality and resource
management, are just the places where some hard work remains, if the
problems are not indeed intractable.
More specifically, the evaluator sees no indication that specifying the
separate transport protocol provided any advantage to defray the large
increase in complexity. Application acks are still required, and no
benefit from the transport acks was evident to the evaluator. Nor was
there any obvious discussion of why "sequenced in-order" delivery is
required, when AAA requests are typically independent. SCTP offers
out-of-order delivery, but DIAMETER seems to have chosen not to use that
feature.
Whether TLV encoding or ASN.1/BER is superior is a religious question,
but DIAMETER manages to require both, if the "strong" extension is
implemented. The evaluator has a pet peeve with length fields that
include the header, making small length values invalid, but that is a
minor point.
Finally, interoperability would be greatly aided by defining a standard
"dictionary" format by which an implementation could adopt wholesale a
set of attributes, perhaps from another vendor, and at least know how to
display them. That is one of the advantages of MIBs.
4. Summary Recommendation
DIAMETER is clearly close enough to meeting the myriad requirements that
it is an acceptable candidate, though needing some polishing. Whether
the vast increase in complexity is worth the increase in functionality
over RADIUS is debatable.
Barney Wolff
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11.7. COPS PRO Evaluation
Evaluation of COPS AAA Requirements
PRO Evaluation
Evaluator - David Nelson
Ref [1] is draft-durham-aaa-cops-reqments-00.txt, a.k.a. 'the document'
Ref [2] is RFC 2748 a.k.a. 'the protocol'
Ref [3] is the AAA evaluation criteria as modified by us.
Ref [4] is draft-ekstein-aaa-protcomp-00.txt.
Ref [5] is draft-durham-aaa-cops-ext-00.txt.
This document uses T to indicate total compliance, P to indicate partial
compliance and F to indicate no compliance.
Section 1 - Per item discussion
1.1 General Requirements
1.1.1 Scalability - The document [1] claims "T", and the evaluator
concurs.
1.1.2 Fail-over - The document [1] claims "T", and the evaluator
concurs.
1.1.3 Mutual Authentication - The document claims "T", and the
evaluator concurs.
1.1.4 Transmission Level Security - The document [1] indicates that
transmission layer security, as defined in [3], is provided in
the protocol, using the mechanisms described in [2]. It should
be noted that this requirement is now a SHOULD in [3]. The
document claims "T", and the evaluator concurs.
1.1.5 Data Object Confidentiality - The document [1] indicates that
end-to-end confidentiality is provided using a CMS-data attribute,
based in large part upon RFC 2630. The evaluator has not, at this
time, investigated the applicability of RFC 2630 to the AAA work.
The document claims "T", and the evaluator concurs.
1.1.6 Data Object Integrity - The document [1] indicates that data
object integrity is provided using a CMS-data attribute, based in
large part upon RFC 2630. The evaluator has not, at this time,
investigated the applicability of RFC 2630 to the AAA work.
The document claims "T", and the evaluator concurs.
1.1.7 Certificate Transport - The document [1] indicates that
certificate transport is provided using a CMS-data attribute,
based in large part upon RFC 2630 and RFC 1510. The evaluator has
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not, at this time, investigated the applicability of RFC 2630 to
the AAA work. The document claims "T", and the evaluator concurs.
1.1.8 Reliable AAA Transport - The document [1] indicates that COPS
uses TCP, which certainly meets the requirements for a reliable
transport. The document claims "T", and the evaluator concurs.
1.1.9 Run over IPv4 - The document [1] claims "T", and the evaluator
concurs.
1.1.10 Run over IPv6 - The document [1] claims "T", and the evaluator
concurs.
1.1.11 Support Proxy and Routing Brokers - Reasonable detail of proxy
operations is provided in [5]. The document [1] claims "T", and
the evaluator concurs.
1.1.12 Auditability - The document [1] alludes to a History PIB that
would enable auditing without explaining how it would work. The
AAA Extension [5] does not provide additional insight. The
document claims "T", and the evaluator awards "P".
1.1.13 Shared Secret Not Required - The document [1] claims "T" and the
evaluator concurs.
1.1.14 Ability to Carry Service Specific Attributes - The document [1]
claims "T", and the evaluator concurs.
1.2 Authentication Requirements
1.2.1 NAI Support - The document [1] indicates that NAI is to be
supported in the Information Model, but notes that for cases
where certificates are in use, the more restrictive syntax of
RFC 2459 applies. The document claims "T", and the evaluator
awards "P".
1.2.2 CHAP Support - The document claims "T", and the evaluator concurs.
1.2.3 EAP Support - The document claims "T", and the evaluator concurs.
1.2.4 PAP/Clear-text Passwords - The document indicates compliance,
presumably using a CMS-data attribute, based in large part upon
RFC 2630. The evaluator has not, at this time, investigated the
applicability of RFC 2630 to the AAA work. The document claims
"T", and the evaluator concurs.
1.2.5 Reauthentication on demand - The document [1] claims "T", and
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the evaluator concurs.
1.2.6 Authorization w/o Authentication - This requirement, as
applied to the protocol specification, mandates that non-
necessary authentication credentials not be required in a
request for authorization. The actual decision to provide
authorization in the absence of any authentication resides in
the application (e.g. AAA server). The document [1] claims "T",
and the evaluator concurs.
1.3 Authorization Requirements
1.3.1 Static and Dynamic IP Addr Assignment - The document claims
"T", and the evaluator concurs.
1.3.2 RADIUS Gateway Capability - The document [1] claims "T", and in
the absence of any detailed discussion of how this is accomplished,
in either [1] or [5], the evaluator awards "P".
1.3.3 Reject Capability - The document claims [1] "T" and the evaluator
concurs.
1.3.4 Preclude Layer 2 Tunneling - The document [1] claims "T", and in
the absence of any detailed discussion of how this is accomplished,
in either [1] or [5], the evaluator awards "P".
1.3.5 Reauth on Demand - The document [1] claims "T", and the evaluator
concurs.
1.3.6 Support for ACLs - The document [1] "T", and the evaluator concurs.
1.3.7 State Reconciliation - The document [1] "T", and the evaluator
concurs.
1.3.8 Unsolicited Disconnect - The document [1] claims "T", and the
evaluator concurs.
1.4 Accounting Requirements
1.4.1 Real Time Accounting - The document [1] claims "T", and the
evaluator concurs.
1.4.2 Mandatory Compact Encoding - Note that the term "bloated" in [3]
is somewhat subjective. The document [1] claims "T", and the
evaluator concurs.
1.4.3 Accounting Record Extensibility - The document [1] claims "T",
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and the evaluator concurs.
1.4.4 Batch Accounting - The protocol [2] [5] does not address how
in detail this feature might be accomplished. The document [1]
claims "T", and the awards "P".
1.4.5 Guaranteed Delivery - Guaranteed delivery is provided by TCP.
The document [1] claims "T", and the evaluator concurs.
1.4.6 Accounting Timestamps - The document claims "T", and the
evaluator concurs.
1.4.7 Dynamic Accounting - The document claims "T", and the evaluator
concurs.
1.5 MOBILE IP Requirements
1.5.1 Encoding of MOBILE IP Registration Messages - The document [1]
claims "T", and the evaluator concurs.
1.5.2 Firewall Friendly - The document [1] claims "T", and the
evaluator concurs.
1.5.3 Allocation of Local Home Agent - The document [1] claims "T",
and the evaluator concurs.
2. Summary Discussion
It may appear, upon initial inspection, that the evaluator has not lent
a critical eye to the compliance assertions of the document [1]. First,
this memo is a "PRO" brief, and as such reasonable benefit of doubt is
to be given in favor of the protocol submission. Second, there is a
fundamental conceptual issue at play. The COPS-PR model provides a
sufficient set of basic operations and commands, a stateful model, the
ability for either "peer" to initiate certain kinds of requests, as well
as an extensible command set, to be able to support a wide variety of
network and resource management protocols. The details of protocol
specific messages is left to Policy Information Base (PIB) data objects.
Since no AAA PIB has been written, the evacuator can only
(optimistically) assess the inherent capabilities of the base protocol
to accomplish the intended requirements of [3], given a reasonable set
of assumptions about what an AAA PIB might look like.
In some senses, this akin to asserting that a given algorithm can be
correctly implemented in a specific programming language, without
actually providing the code.
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The PIB model used by COPS is a powerful and flexible model. The
protocol document [5] spends a considerable amount of time enumerating
and describing the benefits of this data model, and explaining its roots
in Object Oriented (OO) design methodology. Analogies are made to class
inheritance and class containment, among others. It's always hard to say
bad things about OO.
3. General Requirements
COPS-AAA would appear to meet (totally or partially) all of the
requirements of [3], at least as can be determined without the benefit
of an AAA PIB.
4. Summary Recommendation
Recommended with reservation. Before final acceptance of COPS-AAA,
someone is going to have to write the AAA PIB and evaluate its details.
David B. Nelson, Software Engineer V
Enterasys Networks, Inc. (a Cabletron Systems company)
50 Minuteman Road
Andover, MA 01810-1008
(978) 684-1330
dnelson@enterasys.com
11.8. COPS CON Evaluation
Evaluation of COPS against the AAA Requirements CON Evaluation
Evaluator: David Mitton 7/7/00
The Primary document discussed here is [COPSComp] and the arguments
therein based on the proposal [COPSAAA].
[COPSComp] "Comparison of COPS Against the AAA NA Requirements",
draft-durham-aaa-cops-reqments-00.txt
[COPSAAA] "COPS Usage for AAA", draft-durham-aaa-cops-ext-00.txt
[EksteinProtoComp] "AAA Protocols : Comparison between RADIUS, DIAMETER,
and COPS", draft-ekstein-nasreq-protcomp-01.txt
References: (in order of relevancy)
[COPSBase] "The Common Open Policy Service Protocol", RFC 2748
[COPSFwork] "A Framework for Policy-based Admission Control", RFC 2753
[COPSPR] "COPS Usage for Policy Provisioning",
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draft-ietf-rap-cops-pr-02.txt
[COPSSPPI] "Structure of Policy Provisioning Information (SPPI)",
draft-ietf-rap-cops-sppi-00.txt
[COPSCMS] "COPS Over CMS", draft-jwalker-cops-cms-00.txt
[COPSTLS] "COPS Over TLS", draft-jwalker-cops-tls-00.txt
[COPSGSS] "COPS Extension for GSS-API based Authentication Support",
draft-sgundave-gssauth-cops-00.txt
Other COPS & RSVP RFCs & drafts not listed as not directly relevant.
Compliance: T==Total, P==Partial, F=Failed
-------
Section 1 - Per item discussion
Initial Note: [COPSComp] claims "unconditional compliance" with all
requirements.
1.1 General Requirements
1.1.1 Scalability - P (was T) The evaluator is concerned with
scalability of many always-on TCP connections to a server supporting a
lot of clients, particularly with the heartbeat messages. The claim
that the request handle is "unbounded" sounds fishy.
1.1.2 Fail-over - P (was T)
COPS gives an indication of peer failure, and has mechanisms to restart
state, but there seems to be a bias toward a single state server. COPS
has decided that synchronizing state between multiple hot servers is out
of scope.
Because COPS uses TCP, it is at the mercy of the TCP timers of the
implementation which can be significant. Connection timeout reporting
to the application may be delayed beyond the client authentication
timeouts. Tuning the Keep-Alive message to a tighter period will
increase the session and system overhead.
1.1.3 Mutual Authentication - P (was T) The explanation is sort of for
message object integrity. It does not describe authentication
techniques. The evaluator assumes that COPS peers would authenticate
each other at Client-Open time. But cannot understand how this would
work if proxies are involved.
1.1.4 Transmission Level Security - T
1.1.5 Data Object Confidentiality - T
Seems almost a carbon copy of the Diameter capabilities. This evaluator
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echoes the high overhead concerns of the Diameter evaluator for the CMS
capability. TLS is not mentioned here, but is piled on later.
1.1.6 Data Object Integrity - T See above.
1.1.7 Certificate Transport - T
1.1.8 Reliable AAA Transport - T (maybe P)
COPS meets this requirement as well as any other protocol we've
evaluated. That is it does have one application level ACK. Statements
such as "TCP provides guaranteed delivery" are incorrect. COPS does
attempt to identify outages by using a keep-alive message between TCP
peers.
1.1.9 Run over IPv4 - T
1.1.10 Run over IPv6 - T
1.1.11 Support Proxy and Routing Brokers - P (was T)
How client types are supported forward is not well understood by this
evaluator. Does each client type require the Broker to make a different
client Open request to it's upstream servers? What about routing
brokers?
1.1.12 Auditability - P (was T)
(based on our interpretation as non-repudiation, rather than the
definition given in reqts) The explanation of a History PIB is
incomplete and therefore inconclusive.
1.1.13 Shared Secret Not Required - T
Except this clause in [COPSAAA] 6.2 page 14 "COPS MUST be capable of
supporting TLS"
1.1.14 Ability to Carry Service Specific Attributes - P (was T)
a) COPS only allows a small number of unique objects to be added. 256
Object "classes" or types, with 256 subtypes or versions. Client types
are 16 bits long, where the high bit indicates "enterprise" specific
values. But pertain to a COPS peer-connection session. The client type
seems to just identify the information model for the message. eg. it
will be fixed to one value for AAA.
b) Service specific objects are not the same as Vendor Specific Objects.
They pertain to objects within a client type.
c) The PIB model leads to a different model interoperability. Because
most vendor product differ in some way, each PIB will be different, and
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sharing common provisioning profiles will be a rather difficult mapping
problem on the server.
d) It's not clear the different client types can be mixed or that other
objects definitions can be used from other defined client types. It's
really unclear how the client type of a connection propagates in a proxy
situation.
--------
1.2 Authentication Requirements
1.2.1 NAI Support - T
The requirement that RFC 2459 (X.509 profiles) be met presumes that Auth
servers would not have a mapping or local transformation.
1.2.2 CHAP Support - T
An Information Model is being invoked, which I don't see really fleshed
out anywhere. [COPSAAA] does a bit of handwaving and definitions but
doesn't deliver much meat. Nonetheless, this could be handled ala
RADIUS.
1.2.3 EAP Support - P (was T)
Again with the non-existent Information Model. To do EAP, this
evaluator thinks another Request or Decision type is needed here to
indicate to proxys that an extended message exchange is in progress.
1.2.4 PAP/Clear-text Passwords - T
1.2.5 Reauthentication on demand - T
1.2.6 Authorization w/o Authentication - T
The comment "Please note: with existing algorithms, any authorization
scheme not based on prior authentication is meaningless" is meaningless
out of application context.
--------
1.3 Authorization Requirements
1.3.1 Static and Dynamic IP Addr Assignment - T
1.3.2 RADIUS Gateway Capability - P (was T).
It would be interesting to see RADIUS attributes wrapped in some COPS
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"Information Model".
1.3.3 Reject Capability - T
1.3.4 Preclude Layer 2 Tunneling - T
More work for the "Information Model" author!
1.3.5 Reauthorization on Demand - T
1.3.6 Support for Access Rules & Filters - P (was T)
Yet more work for the "Information Model" author, including some design
issues which alluded the RADIUS and Diameter designers. At least an
attempt was made in Diameter. There is nothing here.
1.3.7 State Reconciliation - P (was T).
It is difficult for the evaluator to understand how well the COPS
mechanisms work in a multi-administration situation, or in any proxy
situation. Multi-server coordination, if allowed, seems to be lacking a
description.
1.3.8 Unsolicited Disconnect - T
------
1.4 Accounting Requirements
1.4.1 Real Time Accounting - T
1.4.2 Mandatory Compact Encoding - T
This evaluator does not believe that ADIF is a compact format. But does
believe that the Information Model author can design a PIB with
accounting statistics that will satisfy this requirement.
1.4.3 Accounting Record Extensibility - P (was T)
By defining a vendor/device specific PIB for additional elements.
1.4.4 Batch Accounting - P (was T)
Offered description does not seem to match the requirement.
1.4.5 Guaranteed Delivery - P (was T)
TCP does NOT "guarantee delivery", only application Acks can do that. If
these acks can be generated similar to the description here, then this
requirement is met.
1.4.6 Accounting Timestamps - T
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Another item for the "Information Model" author.
1.4.7 Dynamic Accounting - T
Event and interim accounting can be supported.
-------
1.5 MOBILE IP Requirements
1.5.1 Encoding of MOBILE IP Registration Messages - P (was T)
Yet more work for the "Information Model" author. Hope he can handle it.
1.5.2 Firewall Friendly - P (was T)
I guess. Because it uses TCP and can be identified by known connection
port. But there is an issue with respect to the impact level of mixed
COPS traffic coming through a common firewall port.
1.5.3 Allocation of Local Home Agent - P (was T)
Just add another element to that "Information Model" definition.
-------
2. Summary Discussion
COPS was designed to do some things similar to what we want and be
somewhat flexible, but with a totally different set of assumptions on
how many clients and requests would be funnelled through the
infrastructure and the acceptable overhead. This evaluator is not sure
that it scales well to the fast evolving access market where every
product doesn't implement a small set of common features, but a large
set of overlapping ones.
3. General Requirements
COPS started out with small and easily met set of design goals for RSVP
and DiffServe, and is evolving as a new hammer to hit other nails
[COPSPR]. As COPS implementors get more operational experience, it is
interesting to see more reliability fixes/features quickly get patched
in.
Understanding COPS requires that you read a number RFCs and drafts which
do not readily integrate well together. Each application of COPS has
spawned a number of drafts. It's not clear if one wants to or can
implement a single COPS server that can service AAA and other
application clients
The COPS authors seem to overly believe in the goodness of TCP, and rely
on it to solve all their transport problems, with concessions to
application keep-alive messages to probe the connection status and
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sequence numbers to prevent replay attacks. This evaluator believes this
type of approach may work for many networks but really doesn't scale
well in larger configurations. End-to-end application acks are the only
guaranteed delivery solution, particularly where distributed state is
involved.
COPS falls into an in between place on encoding. It has small number of
simple data object blobs which are concatenated ala RADIUS/Diameter TLVs
to form a flexible message layout. However, they attempt to limit the
number of objects by making them arbitrarily complex ala SNMP MIBs, and
defining yet another data structuring language for these PIBs. There is
a lot of computer science style grandstanding in [COPSAAA] Section 1.2,
but no translation into how a set of data objects can be used to meet
these wonderful features in operation. (or even if we needed them)
This will be the crux of the interoperability issue. RADIUS
implementations interoperate because they at least, understand a common
set of functional attributes from the RFCs. And vendor extent ions can
be simply customized in as needed via dictionaries. If PIB definitions
are needed for every piece and version of access equipment, before you
can use it, then the bar for ease of configuration and use has been
raised quite high.
Support for PIB definition and vendor extensions will be on the same
order as MIB integration in SNMP management products and put the
supposed complexity of Diameter to shame.
4. Summary Recommendation
COPS has a structure that could be made to serve as a AAA protocol,
perhaps by just copying the features of RADIUS and Diameter into it.
The author of [COPSAAA] and [COPSComp] has not done the whole job yet
and some of the missing pieces are vexing even for those already in the
field.
While some of the synergy with other COPS services is attractive, this
evaluator is concerned about the liabilities of combining AAA services
with the new emerging COPS applications in a single server entity will
introduce more complexity than needed and opportunities to have progress
pulled into other rat-holes. (eg. Policy Frameworks)
---------------------------------------------------------------
David Mitton ESN: 248-4570
Advisor, Nortel Networks 978-288-4570 Direct
ServiceWare, IP Mobility 978-288-3030 FAX
Billerica, MA 01821 dmitton@nortelnetworks.com
---
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12. Appendix Meeting Notes
12.1. Minutes of 22-Jun-2000 Teleconference
Date: Wed, 21 Jun 2000 10:34:05 -0400
From: Mark Stevens <markstevens@lucent.com>
Reply-To: markstevens@lucent.com
Organization: Lucent Technologies
Subject: Meeting Notes
Mike,
Here are my meeting notes. Add your vote tallies to the bottom and
I think we have minutes. -Mark
Arguments for and against SNMP as an AAA protocol were given. Stuart
Barkley gave a summary of the pro argument. Mike St. Johns gave a
summary of the con argument.
Dave Nelson asked for "instructions to the jury" in an effort to
determine what evidence could and could not be used in making decisions.
The AAA evaluation criteria is weak in some areas and in others it
appears to be written with what might be interpretered as undue
influence from the NASREQ working group.
Mike St. Johns offered that we must restrict ourselves to considering
only the evidence provided in the compliance documents and any
supporting documents to which they may refer.
In summary: AAA evaluation criteria document, AAA evaluation criteria
source documents, protocol response documents and reference documents.
The question as to what the group should do with malformed requirements
came up. The consensus seemed to be that we would use the requirements
as adjusted in our last meeting where the requirements made no sense.
The floor was then given to Stuart Barkley for the pro SNMP argument.
Highlights:
* In most areas the requirements are met by SNMP.
* Confidentiality and Certificate transport mechanisms may be weak,
but workable.
* With regard to Authentication, every technique can be supported
although support for PAP or cleartext passwords is weak.
* With regard to Authorization, there is nothing in the requirements
that cannot be supported.
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* Accounting everything supported, although there is no specific
consideration for compact encoding. SNMP not as bloated as ASCII or
XML based encoding schemes. Requirement for compact encoding weakly
indicated in requirements anyway. Server-specific attributes
needed, but compact encoding preclude w/o tradeoffs.
* With regard to mobile IP requirement, everything works well,
although firewall friendliness is a judgment call.
* Proxy mechanisms of SNMPv3 mitigates problems w/ firewalls.
* Scalability is ok.
* Overall, meets most requirements and shortfalls are minor.
* In some cases requirements seemed to expressed in a manner that
"stacks" the odds against SNMP.
* SNMP is deployed everywhere already.
* The protocol has a well-understood behaviour despite the tedium of
MIB definition, so it has the advantage of not requiring the
creation of a new infrastructure.
* AAA response document is silent on architecture and MIB definition,
but there is too much work to do at this stage of evaluation. Not
having done the MIB definitions and architecture is not a
limitation of the protocol.
* SNMP is a good candidate.
Mike St. Johns took the floor to give a summary of the con arguement.
* Neither the requirements, core documents nor response document
specify the mechanism of operation.
* Liberties were taken in the assertion that the server to server
interaction requirements were met.
* The scaling arguments are weak.
* Fail-over arguments are weak.
* Security aspects work well with the manager/server paradigm, but
not well in bidirectional interactions among peers.
* The authentication requirements not understood by authors of the
response document.
* SNMP is just data moving protocol.
* Message formats not specified.
* What is the method for supporting authentication? Storing the
information is handled, but what do the nodes do with it?
* The protocol certainly shined in the area of meeting accounting
requirements.
* Although SNMP could certainly play a role in the accounting space,
it is unusable in the areas of Authorization and Athentication.
* The response document does not address how the problem will be
solved.
* It does not address the scalability isssues that may arise in the
transition from a manager-agent mode of operation to a
client-server model.
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The group then examined each requirement against SNMP in a line-by-line
exercise. In cases where there was sufficient dissent from the rating
assigned by the reviewer (Mike St. Johns) the group tallied a vote and
the results of the voting are shown below.
12.2. Minutes of 27-Jun-2000 Teleconference
Return-Path: <owner-aaateam@ops.ietf.org>
From: Basavaraj.Patil@nokia.com
Message-ID: <7B5C0390ACE7D211BC9C0008C7EABA2BCD51CA@daeis07nok>
To: aaateam@ops.ietf.org
Subject: Minutes of teleconference held on 6/27/00 - RADIUS++ evaluation
Date: Tue, 27 Jun 2000 23:27:08 -0500
Logistics:
----------
Attendees - All (Mike St. John, Dave Mitton, Dave Nelson, Mark Stevens,
Barney Wolff, Stuart Barkley, Steven Crain, Basavaraj Patil)
Minutes recorded by : Basavaraj Patil
Evaluation of RADIUS++ AAA Requirements
Pro : Mark Stevens
Con : Dave Nelson
- Question raised on if all meetings held so far have been
recorded. Last week's meeting was recorded by Mark. Previous
meetings have been recorded by Mike. All of these minutes should be
available in the archive.
- Dave Nelson mentioned that Pat Calhoun has responded on the AAA WG
mailing list to the changes made to the requirements document by the
evaluation team. Pat's response includes arguments for inclusion of
some of the requirements that were deleted by the eval team.
Mike concluded that we can reinstate these requirements after
reviewing Pat's comments in detail and the RFCs referenced. The
intent is to take Pat's comments/document and review it between now
and next Thursday (July 6th) and integrate the comments based on the
findings at that time.
Voting Procedure for evaluation : No voting during the discussion. All
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votes MUST be submitted to Mike by COB, June 28th, 00.
- Dave Nelson's summary of the Con statement for RADIUS++.
Overview of the points on which the evaluator disagrees with the
compliance statement.
Conclusion from Dave : Not recommended (Details in the con statement).
Q: Is it possible to use it for accounting?
A: Authentication and Authorization could be separated, but Accounting
is the weak link in this protocol and hence is not suitable.
- Mark Steven's summary of the Pro statment
Agreed with most of the observations made by Dave Nelson. The
biggest thing going for it is that it has been running in this
environment for a while and it does meet most of the requirements in
the document. Transition will be easy and backwards compatibility is
a key plus point.
Point-by-point Discussion:
--------------------------
General (1.1):
--------------
1.1.1 Scalability
BW - There is no actual limit on the number of outstanding requests. The
protocol itself does not limit the number.
DN - Simultaneous requests is not the same as outstanding requests.
Discussion of workarounds that have been implemented to overcome this
problem.
1.1.2 Fail-over
DN - This is an application layer protocol and uses application level
time-outs to provide fail-over solutions. Analogy and discussion on the
use of round-trip-timer in TCP.
Example of how robust a network can be based on a machine at MIT that
was decommissioned and a new one with the same name installed in the
network.
Discussion of environments where proxies for primary, secondary amd
tertiaries exist and the possible effect of flooding messages in the
event of a fail-over detection.
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1.1.3 Mutual Authentication
No Discussion. Accepted as stated.
1.1.4 Transmission level security
This requirement was deleted from the list by the evaluation team. It
was deleted because it is an overgeneralization of Roam Ops.
DN - There is a concern regarding what this really means. Referred to
what Pat is saying about this on the list and the need for it to be
reinstated.
Suggestion to change the tag in the requirements document to hop-by-hop
security.
Does the Roamops group use transmission level security to imply
hop-by-hop security?
1.1.5 Data Object Confidentiality
Mike explained the concept of Cryptographic Message Syntax (CMS -
RFC2630). There are some issues regarding the use of CMS at an end
point. Symmetric or Asymmetric keys can be used.
There does not seem to be a problem with the suggested usage of CMS in
RADIUS++.
1.1.6/7 Data Object Integrity/Certificate Transport
No discussion. (I guess everyone concurs with the statement in the
compliance document and the reviewers comments).
1.1.8 Reliable AAA Transport
BW - Radius provides reliability at the application layer by doing
retransmissions. So why is there a need for a reliable AAA transport
protocol?
- Is it packet loss that the protocol needs to be concerned about?
DN - This requirement is tied to the failover issue. Explanation of the
negative impact of retransmissions in a network, especially in the case
of a web of proxies.
Conclusion is that this requirement deals with packet loss.
1.1.9/10 Run over IPv4/6
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Running over IPv6 should be a trivial issue.
1.1.11 Support Proxy and Routing Brokers
- Discussion on what this requirement means and analogy to DNS servers
in a network.
- RADIUS can be extended to support this requirement and from the
compliance document this does not appear to be fully cooked yet.
1.1.12 Auditability
No Discussion
1.1.13 Shared Secret Not Required
This seems to be a trivial issue to be addressed in RADIUS++.
1.1.14 Ability to carry Service Specific Attributes
No Discussion
Authentication Requirements:
----------------------------
1.2.1 NAI Support
Trivial - Total compliance.
1.2.2 CHAP Support
Comment : RADIUS support of CHAP could be better and the response needs
to be encrypted.
1.2.3/4 EAP/PAP
No Discussion
1.2.5 Reauthentication on Demand
DN - Document claims that the server can reauthenticate by issung an
Access-challenge. There is a change to the state machine and the
suggested solution is too simplistic. Also backwards compatibility would
be an issue.
1.2.6 Authorization w/o Authentication
DN - This is trivial to fix, but this is not mentioned in the compliance
document.
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Authorization Requirements:
---------------------------
1.3.1 Static and Dynamic IP Addr assignment
- RADIUS does not rise to the demands of being a resource manager
- RADIUS assigns an address and it stays assigned for the session. There
is no concept of leasing.
1.3.2 RADIUS Gateway Capability
This is a requirement written that is not applicable to RADIUS itself.
1.3.3/4/5/6/7/8
Call dropped. Somebody else needs to fill in here. (Mike ????)
Accounting Requirements:
------------------------
1.4.1 Real time accounting
No dissent. No discussion
1.4.2 Mandatory compact encoding
Comment made regarding ASN.1 and XML in this context
1.4.3 Accounting Record Extensibility
No discussion
1.4.4 Batch Accounting
No specific wording in the document to show how this can be done. Basically it is real time accounting without the real time constraint.
It may be a trivial issue.
1.4.5/6 Guaranteed Delivery/Accounting Timestamps
No Discussion
1.4.7 Dynamic Accounting
There is ongoing discussion in the AAA WG on this requirement. The
RADIUS WG is also discussing this (comment). The idea here is to be
able to send the equivalent of a phonecall in progress type of messages.
Mobile IP Requirements:
-----------------------
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1.5.1 Encoding of Mobile IP Reg. Messages
May be trivial. Discussion on what this requirement really is. Is it
just the ability to carry the reg. message as payload? Does the AAA
protocol have to delve into the reg. message and behave differently.
1.5.2 Firewall Friendly
No Discussion
1.5.3 Allocation of Local Home Agents
This concept needs to be clarified as the author writing the compliance
statement did not understand it either.
-Basavaraj Patil
If you notice anything that I recorded here as something misinterpreted,
please feel free to make corrections.
12.3. Minutes of 29-Jun-2000 Teleconference
Subject: Minutes of teleconference held on 6/29/00 - DIAMETER evaluation
Message-ID:
<Pine.SUN.4.21.0006291448500.2294-100000@iadserve0.iad.eng.us.uu.net>
Sender: owner-aaateam@ops.ietf.org
Attendees: Mike St. John, Dave Mitton, Dave Nelson, Barney Wolff,
Stuart Barkley, Steven Crain, Basavaraj Patil.
Missing: Mark Stevens.
Minutes recorded by: Stuart Barkley
Evaluation of DIAMETER AAA Requirements
Advocates:
----------
Pro: Basavaraj Patil
Con: Barney Wolff
Summary discussion:
-------------------
PRO summary (Basavaraj Patil):
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session based
lightweight base + extensions
has implementation experience
based upon radius
fixes specific problems with radius,
interoperates with radius
looks like requirements are written for diameter
CON summary (Barney Wolff):
meets most needs, designed with requirements in mind
issues:
scalability in small devices (strong crypto specifically)
failover (need guidance on failover recovery procedures)
Data object confidentiality has been expressed as very important,
diameter glosses over it referring to rfc2630, cost to run on NAS
device
ACL: filter style syntax seems inadequate
state reconciliation: difficult over global multiple administrative
domains
batch accounting: implementation doesn't meet intended need
firewall friendly: until firewalls support SCTP will be failure
summary:
very close
concerns:
size and complexity
needs almost all extensions to actually support needs
separation of SCTP and data (as per iesg suggestion?)
application vs transport acks
Point-by-point Discussion:
--------------------------
General (1.1):
--------------
1.1.1 Scalability
Handles large number of requests
SCTP reduces proxy needs (how? what is justification for this
statement?)
Scalability in large
1.1.2 Fail-over
Recovery from SCTP failure needs discussion (Note to DM: Include in
D. Mitton, et.al. Informational [Page 75]
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final document considerations)
1.1.3 Mutual Authentication
No Discussion
1.1.4 Transmission level security
No Discussion
1.1.5/6 Data Object Confidentiality/Data Object Integrity
Crypto in NAS
NAS needs knowledge of when to use crypto
One Time Passwords (Note to DM: Include in final document
considerations)
1.1.7 Certificate Transport
No Discussion
1.1.8 Reliable AAA Transport
No Discussion
1.1.9/10 Run over IPv4/6
No Discussion
1.1.11 Support Proxy and Routing Brokers
No Discussion
1.1.12 Auditability
No Discussion
1.1.13 Shared Secret Not Required
No Discussion
1.1.14 Ability to carry Service Specific Attributes
No Discussion
Authentication Requirements:
----------------------------
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1.2.1 NAI Support
No Discussion
1.2.2 CHAP Support
No Discussion
1.2.3/4 EAP/PAP
No Discussion
1.2.5 Reauthentication on Demand
No Discussion
1.2.6 Authorization w/o Authentication
No Discussion
Authorization Requirements:
---------------------------
1.3.1 Static and Dynamic IP Addr assignment
No Discussion
1.3.2 RADIUS Gateway Capability
Protocol requirement or implementation/application requirement?
Which RADIUS versions are to be supported? Which subset? (Note to
DM: Include in final document considerations)
1.3.3 Reject Capability
No Discussion
1.3.4 Preclude L2TP
No Discussion
1.3.5 Reauthorize on demand
Raj to look at this again
1.3.6 Support for ACLs
Standardizes syntax not semantics.
Standardizes semantics in NASREQ extension, but is very weak
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1.3.7 State reconciliation
Appears to be weak in that server must "query the world" to restore
its state
Just in time reconciliation
Simultaneous usage limitations
More discussion needed
1.3.8 Unsolicited disconnect
No Discussion
Accounting Requirements:
------------------------
1.4.1 Real time accounting
No Discussion
1.4.2 Mandatory compact encoding
Is ADIF compact?
Is ADIF UTF-8 compatible?
1.4.3 Accounting Record Extensibility
No Discussion
1.4.4 Batch Accounting
DIAMETER okay for small batches. Specification doesn't seem
suitable for large batch transfers (100,000+ records)
1.4.5 Guaranteed Delivery
No Discussion
1.4.6 Accounting Timestamps
No Discussion
1.4.7 Dynamic Accounting
No Discussion
Mobile IP Requirements:
-----------------------
D. Mitton, et.al. Informational [Page 78]
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1.5.1 Encoding of Mobile IP Reg. Messages
Taken of faith
1.5.2 Firewall Friendly
Issues with SCTP being supported initially through firewalls
1.5.3 Allocation of Local Home Agents
Still lack of understanding of the AAA protocol requirements here
(versus just being a roaming attribute)
Overall summary:
----------------
Diameter seems to meet most requirements and is a likely candidate to
support AAA requirements.
Other matters:
--------------
Votes on Diameter should be in by Sunday evening. Same format as
before. Mike will tally up as both majority and average votes.
Should different requirements have different weight?
Possibility of SNMP reconsideration as per ADs? To close off our task
in timeframe allocated, should not reopen submissions or discussions.
Could cause to drag on for long time causing us to miss our July 15
date.
Possibility of needing a few extra days to finish report due to editing
and review needs of the group. Mike to ask ADs to consider slight time
extension possibility.
"No discussion" means that the topic was mentioned but there we no
objections/issues raised on that requirement being met.
-Stuart
These are based upon my notes. Please send any corrections to the list.
12.4. Minutes of 06-Jul-2000 Teleconference
Return-Path: <owner-aaateam@ops.ietf.org>
D. Mitton, et.al. Informational [Page 79]
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From: Barney Wolff <barney@databus.com>
To: aaateam@ops.ietf.org
Date: Fri, 7 Jul 2000 15:31 EDT
Subject: Minutes - 7/6/00
Minutes of AAA-Team Telecon 7/6/00
Pro review of COPS - Dave Nelson
Likes the object model.
No apparent showstoppers.
Will resend review with typos corrected.
Con review of COPS - Dave Mitton
Architecture is mostly there.
Strong dependency on info model, sceptical of object model.
Problem with info model in multi-vendor, multi-administration
environment.
How does server speak to multiple client flavors?
Will resend review with typos corrected.
Comment by Mike StJ "replace SNMP with COPS" - :) I think.
Per-Item discussion
1.1.1 Scalability - concern re always-on TCP. Direction to DM - add
general issue of number of connections.
1.1.2 Failover - No hot backup, but true of all protocols. (ie, no
explicit mention of server-server protocol that might keep a backup
server in sync so it could take over instantly.) 1.1.3 Mutual
Authentication - perhaps relies on TLS. Draft does not otherwise
support this.
1.1.8 Reliable AAA Transport - TCP + appl heartbeat.
1.1.11 Proxy & Routing Brokers - client-type interaction with proxy is
questionable. (In later discussion, it appears client-type is a field
in the request, and perhaps all AAA is one type, so may not be an
issue.) 1.1.13 Shared secret not req'd - runs over TLS, no multiple
levels of security.
1.2.1 NAI Support - some uncertainty on the impact of RFC 2459 (X.509
profiles) on this - may restrict NAI in some way?
1.2.3 EAP Support - multi-pass handshake needs work.
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1.2.6 Authorization without Authentication - Mike comments the
requirement is broken. BW comment (post-meeting) - the requirement
appears intended specifically to chastise RADIUS for requiring User-Name
and some sort of password in an Access-Request, even if it's sent
pre-connect, on receipt of DNIS, for example. Sure it's silly, but does
it really matter whether an attribute is absent or filled with "NONE"?
This was just nasty sniping at RADIUS on somebody's part, imho.
1.3.2 RADIUS Gateway - skepticism was expressed.
1.3.4 !Preclude L2 Tunnels - too much handwaving.
1.3.6 Access Rules - lots of work needed.
1.3.7 State Reconciliation - multi-server coordination is an issue.
1.4.4 Batch Accounting - for small batches, perhaps.
1.4.5 Guaranteed Delivery - application acks are an area of mystery.
1.5.2 Firewall-Friendly - COPS like any Swiss-Army-Knife protocol (SNMP)
requires the firewall to look inside the packets, because passing AAA
may be allowed but not other protocol uses. So it would be a big help,
for both COPS and SNMP, to define a different port for its AAA
application.
Updated briefs and votes are due by Sunday. Some discussion of the
structure of the final document. Next meeting is Tuesday, with
"hangers-on".
Reminder - we are supposed to be reacting to Pat Calhoun's reaction to
our requirement comments, via email, to be finished on or before
Tuesday.
Barney
12.5. Minutes of 11-Jul-2000 Teleconference
Return-Path: <owner-aaateam@ops.ietf.org>
Message-ID: <6BE5C54C541BD211830B0000F84AA009F12038@and-exc2.ctron.com>
From: "Nelson, David" <dnelson@enterasys.com>
To: "'aaateam@ops.ietf.org'" <aaateam@ops.ietf.org>
Cc: "Mitton, David " <dmitton@americasm06.nt.com>
Subject: Minutes of 7/11/00
Date: Tue, 11 Jul 2000 17:49:09 -0400
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Sender: owner-aaateam@ops.ietf.org
Present: Mike, Bernard, Paul, Bert, Raj, Dave N., Dave M., Barney,
Stuart, Mark
Mike St. Johns set the ground rules.
An item by item review of the summary results was held.
1.1.1 Question as to why SNMP and RADIUS++ are "P"? There are issues
regarding scaling of retries in a web of proxies (multi-layer proxy;
primary, secondary tertiary servers at each level).
1.1.2 No protocol did very well. [Document Editor - take special note
of this issue.] Similar issues as above, e.g. web of proxies. Recovery
of state from a previously failed primary server?
1.1.3 Question as to how serious is the need for this requirement?
May be some legitimate requirements from Mobile IP. Is this requirement
an AAA-level issue?
1.1.4 Called hop-by-hop or transmission level?
1.1.5 Most protocols evaluated used CMS to meet this requirement.
Question as to applicability of CMS for NASes and other edge devices?
[Document Editor - take special note of this issue.] There is a
requirement for object by object confidentiality. consider three-party
scenarios.
1.1.6 Question as to why SNMP did not rate the same as for item 1.1.5?
The evaluation is based on what was contained in the submission
documents, rather than capabilities of the protocol itself. Too much
hand waving.
1.1.7 No comments.
1.1.8 Question as to meaning of "reliable"? Discussion of transport
protocols was deferred to later in the meeting.
1.1.9 No comments.
1.1.10 SNMP received "P" because of hand waving in the submission
documents.
1.1.11 SNMP received "F" because this section of the submission
document indicated "t.b.d.". DIAMETER was the only protocol submission
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to completely address this item.
1.1.12 We treated this requirement as "non-repudiation". There is a
concern that digital signatures are computationally expensive and are
not globally available. COPS has more work to do on this item.
1.1.13 Question that "no shared secrets" should be interpreted to mean
that an alternative key management mechanism is available? We treated
this as meaning that application-layer security could be turned off in
deference to transport layer security. There had been discussion of the
use of IKE in the AAA protocol.
1.1.14 No comments.
1.2.1 No comments.
1.2.2 No comments.
1.2.3 No comments.
1.2.4 Is there a need for a clear-text "password" for service such as
OTP, SecurID, et. al.? It was noted that all plain passwords are
exposed in clear-text at the NAS or other edge device, which is no more
inherently trustworthy than any AAA server or proxy.
1.2.5 We distinguished event-driven reauthentication from timer-driven
(or lifetime-driven). How is this requirement to be met in a proxy
environment?
1.2.6 We asserted that this requirement is an oxymoron.
1.3.1 We had difficulty in determining what "static" meant, and from
which reference point it was measured.
1.3.2 We agreed that NAIs could be handled, possibly with some
restrictions.
1.3.3 No comment.
1.3.4 The SNMP submission documents contained significant hand waving.
1.3.5 Similar comments as to item 1.2.5. The question was raised as
to how the server knows when to send this request? [Document Editor -
take special note of this item.]
1.3.6 We found that the notation in DIAMETER was weak, and of a least
common denominator nature. In general, there was concern about
achieving interoperability when the syntax was standardized but the
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semantics were not. This area needs further work. [Document Editor -
take special notice of this item.]
1.3.7 Question as to how this requirement is achieved via proxies?
[Document Editor - take special notice of this item.]
1.4.1 No comment.
1.4.2 No comment.
1.4.3 No comment.
1.4.4 There was significant skepticism regarding batch accounting as
part of the AAA protocol. How large are the "batches"? Should this
requirement be met using FTP or something similar?
1.4.5 No comment.
1.4.6 No comment.
1.4.7 No comment.
1.5.1 No comment.
1.5.2 There was some discussion of what constitutes firewall friendly.
It was suggested that the firewall didn't want to look into packets much
past the application protocol address (e.g. UDP or TCP port number).
Protocols such as SNMP and COPS that have usage other than AAA are at a
disadvantage, since the firewall must look deep into the application PDU
to determine the intended purpose of the packet. DIAMETER suffers from
reliance of SCTP, which is not widely deployed or widely recognized by
firewalls. Should firewalls also be AAA proxy engines? Has this issue
anything to do with interoperability with NAT? [Document Editor - take
special note of this item.]
1.5.3 We had some confusion as to what the requirement actually was.
Raj seemed to be able to explain it, but the rest of us had to take it
on faith.
A poll was taken on overall acceptability of each of the protocols
submitted, for requirements conformance.
Raj
DIAMETER Acceptable
RADIUS++ Acceptable with Engineering (large effort)
COPS Acceptable with Engineering (small effort)
SNMP Acceptable for Accounting
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Dave N.
SNMP Acceptable for Accounting
RADIUS++ Unacceptable (would end up being like DIAMETER)
COPS Acceptable with Engineering (small effort)
DIAMETER Acceptable
Dave M.
SNMP Acceptable for Accounting
RADIUS++ Unacceptable
DIAMETER Acceptable with Engineering (small effort)
COPS Acceptable with Engineering (medium effort)
Barney
SNMP Acceptable with Engineering (large effort)
RADIUS++ Acceptable with Engineering (medium effort)
COPS Acceptable with Engineering (medium effort)
DIAMETER Acceptable with Engineering (small effort)
Stuart
SNMP Acceptable with Engineering (medium effort)
RADIUS++ Unacceptable
DIAMETER Acceptable with Engineering (small effort)
COPS Acceptable with Engineering (medium effort)
Mark
RADIUS++ Unacceptable
SNMP Acceptable for Accounting
COPS Acceptable with Engineering (small effort)
DIAMETER Acceptable with Engineering (small effort)
Mike
SNMP Concern about overhead of SNMPv3 security.
RADIUS++ Would end up looking like DIAMETER.
COPS Needs small to medium engineering effort. Unclear that we
can separate the AAA functions such as to solve the firewall issues.
DIAMETER Preferred protocol. Has a better set of protocol
interactions than does COPS. COPS has a better data model than does
DIAMETER.
A general wrap-up discussion was held.
It was considered important that as much of the thought processes and
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rationales be placed in the final report as is feasible. Mike St. John
will work with Dave Mitton on the ID. We really need to meet the IETF
July 14 submission deadline, even if we have to issue an update on the
AAA WG mailing list. All agreed that the process went fairly well. In
future evaluations of this nature, it would be well for the evaluators
to follow the requirements documents closely, for the submitters to
create accurate and complete conformance documents, and to allow a
"re-spin" cycle to correct errors and omissions in the requirements
documents and conformance documents.
A discussion of the transport protocol was held.
The issue with transport is congestion control. There has been a
problem with streams-oriented applications over TCP. The IESG is
increasingly sensitive to this issue in new protocols. It was noted
that AAA was a transaction-oriented application. Other request-response
applications, such as DNS, seem to scale welt to Internet-scale using
simple application-level retries and UDP transport. TCP has problems
with head-of-line blocking, especially when multiple sessions are using
a single TCP connection. AAA typically will send 3 or 4 iterations and
then indicate a failure to the upper layers. It won't continue
retransmissions in the face of congestion, like TCP. It was noted that
bulk data transfer may not best be implemented in the AAA protocol.
Concern was voiced that SCTP is not a widely implemented protocol. AAA
will implement congestion control by limiting the number of outstanding
requests. Some RADIUS implementations send lots of traffic when they
encounter misconfigured shared secrets, but this is likely caused by a
lack of proper error recovery. DIAMETER, as currently drafted, relies
on SCTP. Can AAA run over UDP? The IESG didn't say "no"; their issue
is addressing congestion control.
As always, corrections, and additions to the minutes are welcome.
David B. Nelson, Software Engineer V
Enterasys Networks, Inc. (a Cabletron Systems company)
50 Minuteman Road
Andover, MA 01810-1008
(978) 684-1330
dnelson@enterasys.com
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