Liaison statement
Information about PANA as an applicable protocol for subscriber authentication in DSL networks

IETF PANA working Group liaison to:

Gavin Young, DSL Forum Technical Committee Chair
gyoung@dslforum.org

From:

        Alper Yegin, IETF PANA WG co-chair, alper.yegin@yegin.org
        Basavaraj Patil, ITEF PANA WG co-chair, basavaraj.patil@nsn.com

Date: December 12, 2007

Subject: Information about PANA as an applicable protocol for subscriber
authentication in DSL networks

Dear Gavin,

The PANA (Protocol for carrying Authentication for Network Access) Working
Group in the IETF is chartered to work on defining a link-layer type
independent network access authentication protocol. WG has completed its work
on specifying the PANA protocol and the specification is now in the RFC editors
queue for publication as a proposed standard
(http://ietf.org/internet-drafts/draft-ietf-pana-pana-18.txt).

Earlier this year, the DSL Forum had sent a liaison statement to the IETF
requesting information about a protocol or work in the IETF which would meet
the DSL Forum’s requirements for subscriber authentication in the context of
the evolution of the DSL architecture. DSL Forum’s migration away from PPP
has been identified as one of the candidate deployments for PANA from the early
days of the WG as documented in RFC 4058 (http://ietf.org/rfc/rfc4058.txt).
Additionally, the specific DSLF requirements were discussed at the PANA WG
meeting at IETF70 in Vancouver (Dec 5, 2007) and on the PANA WG mailing list
afterwards. WG believes that PANA is applicable to the current requirements
presented by DSLF. The PANA WG’s analysis is presented below.

We would like to request the DSL Forum’s technical committee to review the
suitability of PANA for addressing your requirements especially in view of the
fact that the protocol is now lined up to be published as a proposed standard
RFC by the IETF.  If you have further questions or need clarifications, please
do not hesitate to contact the PANA WG.

Sincerely,

Alper Yegin (PANA WG co-chair)          Basavaraj Patil (PANA WG co-chair)

IPAuth-1:    Authentication must not depend on the use of any given application,
             eg web browser.
Compliance:  Yes
Explanation: PANA implementation does not rely on other applications.

IPAuth-2:    Must re-use existing SP Authentication infrastructure (use Radius
             Database)  and allow mixed mode operation (eg PPP and IP) on the
             same L3 edge device
Compliance:  Yes
Explanation: PANA does not require any changes on the AAA database. It can
             be used over IP networks that co-exist with PPP networks.

IPAuth-3:    Must offer L3 edge device (BRAS) subscriber policy enforcement
             via pull and push methods, ie L3 edge must be aware of
             authentication status and any subscriber credentials
Compliance:  Yes
Explanation: PANA Authentication Agent (PAA) can be implemented on the BRAS,
             or elsewhere.

IPAuth-4:    Must allow for authorization purposes the use of any additional
             identifiers that may be available, eg MAC address, Option82
             circuit-id.
Compliance:  Yes
Explanation: MAC address is already available on the IP messages that carry
             PANA. PANA does not prevent use of Option 82 with DHCP.

IPAuth-5:    Should allow for subscriber nomadicity and support tracking of
             changes to location.
Compliance:  Yes
Explanation: PANA allows establishing a new session or maintaining the same
             session upon mobility/nomadicity.

IPAuth-6:    Must fit into TR-101 operational model
Compliance:
Explanation: Although we do not see any issues there, IETF does not have the
             expertise to fully evaluate this requirement.

IPAuth-7:    Must support revoking authentication
Compliance:  Yes
Explanation: PANA Termination message is explicitly designed for that purpose.

IPAuth-8:    Must handle L3 CPE device authentication and end-device (PC) user
             based authentication (likely with L2 CPEs in the latter case)
Compliance:  Yes
Explanation: PANA Client (PaC) can be implemented on both CPEs and end-devices.

IPAuth-9:    Should be simple to implement on client (PC or CPE)
Copliance:   Yes
Explanation: Implementation does not require changes to the operating system.
             Open source implementation available.

IPAuth-10:   Must be independent of medium type (eg Fixed Ethernet, Legacy ATM,
             PON, WiFi, WiMax, etc)
Compliance:  Yes
Explanation: This is the original design goal of PANA.

IPAuth-11:   Must not require major re-work for IPv6. None ideally.
Compliance:  Yes
Explanation: Same protocol can be used for both IPv4 and IPv6.

IPAuth-12:   Must be resilient to attacks on the subscriber, eg against
             brute-force challenge attacks, or  spoofing of an authenticator
             edge device
Compliance:  Yes
Explanation: Rate limiting, message validation, message authentication are used
             against such threats.

IPAuth-13:   Must offer authenticator edge device resiliency, eg not be prone to
             DOS authentication attacks
Compliance:  Yes
Explanation: Stateless handshake and rate limiting are used against such
             threats.

IPAuth-14:   Must allow for authentication and download of  subscriber service
             profile before service IP address is assigned
Compliance:  Yes
Explanation: PANA requires an IP address be configured prior to authentication
             (a IPv4/IPv6 link-local, or a short-lease DHCP address), but allows
             the “service IP address� be assigned after authentication.

IPAuth-15:   Must offer an option to re-authenticate periodically or on demand.
Compliance:  Yes
Explanation: Both the client-side and network-side are capable of initiating
             re-authentication.

IPAuth-16:   At an absolute minimum, must provide equivalent or better security
             than PPP CHAP/MD5 does today. Must include the ability to move to
             more secure authentication methods over time.
Compliance:  Yes
Explanation: Supports any EAP method (including CHAP/MD5 equivalent of EAP-MD5).

IPAuth-17:   Should  offer authentication fail/success reason message to
             subscriber from authenticator .
Compliance:  Yes
Explanation: Supports explicit authentication and authorization result codes
             (extensible).

IPAuth-18:   Must allow for multiple authenticated subscribers on same physical
             or logical interface.
Compliance:  Yes
Explanation: PANA Session-ID can demultiplex multiple authenticated sessions
             over the same physical/logical interface.

IPAuth-19:   Must  offer scalable subscriber management, eg not rely on
             subscriber credentials configured on the authenticator Edge
Compliance:  Yes
Explanation: PANA is independent of any backend protocol (RADIUS, Diameter,
             LDAP, etc.) that may or may not be used by the authenticator edge.

IPAuth-20:   Must have a logical path towards standardization
Compliance:  Yes
Explanation: PANA specification is already approved by IESG and currently in
             IETF RFC queue.

IPAuth-21:   Must scale to 10000s of  subscribers per L3 edge device (ie must
             be conservative in use of resources)
Compliance:  Yes
Explanation: See PANA Session Attributes in the spec.