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RFC 3127

 
 
 

Authentication, Authorization, and Accounting: Protocol Evaluation

Part 2 of 3, p. 21 to 55
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Appendix C - Position Briefs

C.1 SNMP PRO Evaluation

   Evaluation of SNMP AAA Requirements
   PRO Evaluation
   Evaluator - Stuart Barkley

   Ref [1] is "Comparison of SNMPv3 Against AAA Network Access
   Requirements", 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

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   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
   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.

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   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 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.

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   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.

   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.

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   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

   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

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   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

   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.

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   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.

   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.

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   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.

C.2 SNMP CON Evaluation

   Evaluation of SNMP AAA Requirements
   CON Evaluation
   Evaluator - Michael StJohns

   Ref [1] is "Comparison of SNMPv3 Against AAA Network Access
   Requirements", 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 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 definitely 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

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   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
   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

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   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
   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

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   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

   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)

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   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

   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.

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   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.

C.3 RADIUS+ PRO Evaluation

   Evaluation of RADIUS AAA Requirements PRO Evaluation

   Evaluator - Mark Stevens

   Ref [1] is "Comparison of RADIUS Against AAA Network Access
   Requirements"
   Ref [2] is "Framework for the extension of the RADIUS(v2) protocol"
   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 referred to
   as, "Comparison of RADIUS Against AAA Network Access Requirements"
   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 implication 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)

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   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.

   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 messages (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++ can be considered a reliable transport when augmented with
   Layer 2 Tunneling Protocol.  The protocol itself does not provide
   reliability 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)

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   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 be initiated 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 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.
   Requirement seems to be worded to preclude 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 - ?

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   1.3.5 [e] Reauthorization on Demand - Implementation in the field
   demonstrate that extensions to RADIUS can support the desired
   behavior.  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)

   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
   some clarification and refinement.  Eval - F (no change)

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   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 transition 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.

C.4 RADIUS+ CON Evaluation

   Evaluation of RADIUS++ (sic) AAA Requirements CON Evaluation
   Evaluator - David Nelson

   Ref [1] is "Comparison of RADIUS Against AAA Network Access
   Requirements", a.k.a. 'the document'
   Ref [2] is "Framework for the extension of the RADIUS(v2) protocol",
   a.k.a. 'the protocol'
   Ref [3] is the AAA evaluation criteria as modified by us.
   Ref [4] is RFC 2869.
   Ref [5] is an expired work in progress "RADIUS X.509 Certificate
   Extensions".
   Ref [6] is RFC 2868

   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.

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   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.  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".

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   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 work in progress, "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
   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".

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   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 [1] "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 [1] "T", and the
   evaluator concurs.

   1.2.4 PAP/Clear-text Passwords - The document [1] 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
   the AAA work.  The document claims [1] "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

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   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
   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

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   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
   application-level acknowledgment.  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 [1] "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 works in progress.  The document
   claims [1] "P", and the evaluator concurs.

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   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 works in progress within the RADIUS WG, in an
   attempt to "improve" the RADIUS protocol.  All of these works in
   progress 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?".

   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.

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C.5 Diameter PRO Evaluation

   Evaluation of Diameter against the AAA Requirements
   PRO Evaluation
   Evaluator - Basavaraj Patil

   Ref [1] is "Diameter Framework Document".
   Ref [2] is "Diameter NASREQ Extensions".
   Ref [3] is the AAA evaluation criteria as modified by us.
   Ref [4] is "Diameter Accounting Extensions".
   Ref [5] is "Diameter Mobile IP Extensions".
   Ref [6] is "Diameter Base Protocol".
   Ref [7] is "Diameter Strong Security Extension".
   Ref [8] is "Comparison of Diameter Against AAA Network Access
   Requirements".

   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
   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.

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   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 characteristics 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 (referring
   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 Syntax (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

   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.

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   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.

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   1.3 Authorization Requirements

   1.3.1 Static and Dynamic IP Addr Assignment

   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.

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   1.3.8 Unsolicited Disconnect

   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.

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   1.5 MOBILE IP Requirements

   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"

   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 support 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.

C.6 Diameter CON Evaluation

   Evaluation of Diameter against the AAA Requirements
   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 the work in progress, "Diameter Strong
   Security Extension", 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.

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   1.1.6 Data Object Integrity - P (was T).  See above.

   1.1.7 Certificate Transport - T

   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 mechanism 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.)

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   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 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

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   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.

   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 filigree.  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.

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   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.



(page 55 continued on part 3)

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