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

Submission date 2007-12-12
From IETF PANA WG (Alper Yegin)
To DSL Forum (
Response contact,
Technical contact,
Purpose For information
Attachments (None)
IETF PANA working Group liaison to:

Gavin Young, DSL Forum Technical Committee Chair


	Alper Yegin, IETF PANA WG co-chair,
	Basavaraj Patil, ITEF PANA WG co-chair,

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

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 ( 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


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

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

IPAuth-2:    Must re-use existing SP Authentication infrastructure (use
             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
             be used over IP networks that co-exist with PPP networks.

IPAuth-3:    Must offer L3 edge device (BRAS) subscriber policy
             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
             or elsewhere.

IPAuth-4:    Must allow for authorization purposes the use of any
             identifiers that may be available, eg MAC address,
Compliance:  Yes	
Explanation: MAC address is already available on the IP messages that
             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
             session upon mobility/nomadicity.

IPAuth-6:    Must fit into TR-101 operational model
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

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

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

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

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

IPAuth-16:   At an absolute minimum, must provide equivalent or better
             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

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

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

IPAuth-19:   Must  offer scalable subscriber management, eg not rely on

             subscriber credentials configured on the authenticator
Compliance:  Yes
Explanation: PANA is independent of any backend protocol (RADIUS,
             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.