draft-ietf-pana-pana-00.txt   draft-ietf-pana-pana-01.txt 
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Internet Draft D. Forsberg Internet Draft D. Forsberg
Nokia Nokia
Y. Ohba Y. Ohba
Toshiba Toshiba
B. Patil B. Patil
Nokia Nokia
H. Tschofenig H. Tschofenig
Siemens Siemens
A. Yegin A. Yegin
DoCoMo USA Labs DoCoMo USA Labs
Document: draft-ietf-pana-pana-00.txt Document: draft-ietf-pana-pana-01.txt
Expires: September 2003 March 2003 Expires: December 2003 June 2003
Protocol for Carrying Authentication for Network Access (PANA) Protocol for Carrying Authentication for Network Access (PANA)
<draft-ietf-pana-pana-00.txt> <draft-ietf-pana-pana-01.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance This document is an Internet-Draft and is subject to all provisions
with all provisions of Section 10 of RFC2026. of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as at any time. It is inappropriate to use Internet-Drafts as reference
reference material or to cite them other than as "work in progress". material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Expires September 2003 1 The list of Internet-Draft Shadow Directories can be accessed at
PANA March 2003 http://www.ietf.org/shadow.html
Abstract Abstract
This document defines the Protocol for Carrying Authentication for This document defines the Protocol for Carrying Authentication for
Network Access (PANA), a link-layer agnostic transport for Network Access (PANA), a link-layer agnostic transport for
Extensible Authentication Protocol (EAP) to enable network access Extensible Authentication Protocol (EAP) to enable network access
authentication between clients and access networks. PANA can carry authentication between clients and access networks. PANA can carry
any authentication method that can be specified as an EAP method, any authentication method that can be specified as an EAP method,
and can be used on any link that can carry IP. PANA covers the and can be used on any link that can carry IP. PANA covers the
client-to-network access authentication part of an overall secure client-to-network access authentication part of an overall secure
network access framework, which additionally includes other network access framework, which additionally includes other
protocols and mechanisms for service provisioning, access control as protocols and mechanisms for service provisioning, access control as
a result of initial authentication, and accounting. a result of initial authentication, and accounting.
Table of Contents Table of Contents
1 Introduction...................................................2 1 Introduction..................................................3
2 Terminology....................................................3 2 Terminology...................................................4
3 Protocol Overview..............................................4 3 Protocol Overview.............................................5
4 Protocol Details...............................................5 4 Protocol Details..............................................6
5 PANA Security Association Establishment.......................15 4.1 Common Processing Rules.................................6
6 Authentication Method Choice..................................16 4.2 Discovery and Initial Handshake Phase..................10
7 Filter Rule Installation......................................16 4.3 Authentication Phase...................................12
8 Data Traffic Protection.......................................17 4.4 Re-authentication......................................14
9 Message Formats...............................................18 4.5 Termination Phase......................................16
10 Open Issues...................................................18 4.6 Illustration of a Complete Message Sequence............16
11 Security Considerations.......................................18 4.7 Device ID choice.......................................18
12 References....................................................23 4.8 Refresh Interval Negotiation...........................18
13 Acknowledgments...............................................25 4.9 Mobility Handling......................................19
14 Author's Addresses............................................25 4.10 Event Notification...................................19
15 Full Copyright Statement......................................35 4.11 PaC Implications.....................................20
4.12 PAA Implications.....................................20
5 PANA Security Association Establishment......................20
6 Authentication Method Choice.................................21
7 Filter Rule Installation.....................................21
8 Data Traffic Protection......................................22
9 Message Formats..............................................23
9.1 PANA Header............................................23
9.2 AVP Header.............................................24
9.3 PANA Messages..........................................26
9.4 AVPs in PANA...........................................29
9.5 AVP Occurrence Table...................................32
10 Security Considerations...................................33
11 Open Issues...............................................39
12 Acknowledgments...........................................39
13 References................................................39
Change History..................................................42
Appendix A. Adding sequence number to PANA for carrying EAP....43
Full Copyright Statement........................................52
1 Introduction 1 Introduction
Providing secure network access service requires access control Providing secure network access service requires access control
based on the authentication and authorization of the clients and the based on the authentication and authorization of the clients and the
access networks. Initial and subsequent client-to-network access networks. Initial and subsequent client-to-network
authentication provides parameters that are needed to police the authentication provides parameters that are needed to police the
traffic flow through the enforcement points. A protocol is needed to traffic flow through the enforcement points. A protocol is needed to
carry authentication methods between the client and the access carry authentication methods between the client and the access
network. IETF PANA Working Group has been chartered with the goal network. IETF PANA Working Group has been chartered with the goal
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Link-layer authentication mechanisms are used as enablers of secure Link-layer authentication mechanisms are used as enablers of secure
network access. A higher-layer authentication is deemed necessary network access. A higher-layer authentication is deemed necessary
when link-layer authentication mechanisms are either not available when link-layer authentication mechanisms are either not available
for lack of technology or deployment difficulties, or not able to for lack of technology or deployment difficulties, or not able to
meet the overall requirements, or when multi-layer (e.g., link-layer meet the overall requirements, or when multi-layer (e.g., link-layer
and network-layer) authentication is needed. Currently there is no and network-layer) authentication is needed. Currently there is no
standard network-layer solution for authenticating clients for standard network-layer solution for authenticating clients for
network access. In the absence of such a solution, some inadequate network access. In the absence of such a solution, some inadequate
standards-based solutions are deployed or non-standard ad-hoc standards-based solutions are deployed or non-standard ad-hoc
solutions are invented. [USAGE] describes the problem statement in
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PANA March 2003
solutions are invented. [USAGE] Internet-Draft describes the problem
statement in detail.
Scope of this working group is identified as designing a link-layer Scope of this working group is identified as designing a link-layer
agnostic transport for network access authentication methods. PANA agnostic transport for network access authentication methods. PANA
Working Group has identified EAP [RFC2284] as the payload for this Working Group has identified EAP [RFC2284] as the payload for this
protocol and carrier for authentication methods. In other words, protocol and carrier for authentication methods. In other words,
PANA will carry EAP which can carry various authentication methods. PANA will carry EAP which can carry various authentication methods.
By the virtue of enabling transport of EAP above IP, any By the virtue of enabling transport of EAP above IP, any
authentication method that can be carried as an EAP method is authentication method that can be carried as an EAP method is
made available to PANA and hence to any link-layer technology. There made available to PANA and hence to any link-layer technology. There
is a clear division of labor between PANA, EAP and EAP methods. is a clear division of labor between PANA, EAP and EAP methods.
Defining new authentication methods, or deriving/distributing keys Defining new authentication methods, or deriving/distributing keys
is outside the scope of PANA. Providing a secure channel that is outside the scope of PANA. Providing a secure channel that
protects EAP and EAP methods against eavesdropping and spoofing is protects EAP and EAP methods against eavesdropping and spoofing is
not an objective of the PANA design. not an objective of the PANA design.
While PANA is a fundamental part of a complete secure network access While PANA is a fundamental part of a complete secure network access
solution, its responsibility is limited to authentication and solution, its responsibility is limited to authentication and
authorization of the client and the network. Providing access authorization of the client and the network. Providing access
control is outside the scope of PANA. A separate provisioning control is outside the scope of PANA. A separate provisioning
protocol is needed for passing filtering protocol is needed for passing filtering information to access
information to access control nodes in the network. Additionally, control nodes in the network. Additionally, mechanisms to provide
mechanisms to provide data traffic protection in terms of data traffic protection in terms of authentication, integrity and
authentication, integrity and replay protection, and encryption are replay protection, and encryption are outside the scope as well.
outside the scope as well.
Various environments and usage models for PANA are identified in the Various environments and usage models for PANA are identified in the
[USAGE] Internet-Draft. Potential security threats for network-layer [USAGE] Internet-Draft. Potential security threats for network-layer
access authentication protocol is discussed in [THREATS] draft. access authentication protocol is discussed in [THREATS] draft.
These two drafts have been essential in defining the requirements These two drafts have been essential in defining the requirements
[PY+02] on the PANA protocol. Note that some of these requirements [PY+02] on the PANA protocol. Note that some of these requirements
are imposed by the chosen payload, EAP [RFC2284]. are imposed by the chosen payload, EAP [RFC2284].
This Internet-Draft makes an attempt for defining the PANA protocol This Internet-Draft makes an attempt for defining the PANA protocol
based on the other drafts discussed above. Special care has been based on the other drafts discussed above. Special care has been
given to ensure the currently stated scope is observed and to keep given to ensure the currently stated scope is observed and to keep
the protocol as simple as possible. The current state of this draft the protocol as simple as possible. The current state of this draft
is not complete, but it should be regarded as a work in progress. is not complete, but it should be regarded as a work in progress.
The authors made effort to capture the common understanding The authors made effort to capture the common understanding
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choices being made in this draft should not be considered as cast in choices being made in this draft should not be considered as cast in
stone. stone.
2 Terminology 2 Terminology
This section describes some terms introduced in this document: This section describes some terms introduced in this document:
PANA Session: PANA Session:
PANA session is defined as the exchange of messages between the PANA session is defined as the exchange of messages between the
PaC and the PAA to authenticate a user(PaC) for network access. PANA Client (PaC) and the PANA Authentication Agent (PAA) to
If the authentication is unsuccessful, the session is authenticate a user (PaC) for network access. If the
authentication is unsuccessful, the session is terminated. The
Tschofenig (ed.) Expires September 2003 3 session is considered as active until there is a disconnect
PANA March 2003 indication by the PaC or the PAA terminates it.
terminated. The session is considered as active until there is a
disconnect indication by the PaC or the PAA terminates it.
Session Identifier: Session Identifier:
The device identifier is also used as the session identifier. This identifier is used to uniquely identify a PANA session on
This is used for indicating a disconnect or session revocation the PAA and PaC. It is included in PANA messages to bind the
or for charging purposes. message to a specific PANA session.
PANA Disconnect Indication: PANA Disconnect Indication:
PANA session termination with explicit notification from a PaC PANA session termination with explicit notification from a PaC
sent to the PAA. The PDI also includes the session identifier. sent to the PAA. The PDI also includes the session identifier.
PANA Session Revocation: PANA Session Revocation:
PANA session termination with explicit notification sent from PANA session termination with explicit notification sent from
the PAA to the PaC. The PSR includes the session identifier. the PAA to the PaC. The PSR includes the session identifier.
PANA Security Association: PANA Security Association:
The representation of the trust relation between the PaC and the The representation of the trust relation between the PaC and
PAA that is created at the end of the authentication phase the PAA that is created at the end of the authentication phase
(PH2). This security association includes the device identifier (PH2). This security association includes the device identifier
of the peer, and a shared key when available. of the peer, and a shared key when available.
The terms PaC, PAA, EP and Device Identifier can be found in The definition of the terms PANA Client (PaC), PANA Authentication
[PY+02]. Agent (PAA), Enforcement Point (EP) and Device Identifier (DI) can
be found in [PY+02].
3 Protocol Overview 3 Protocol Overview
The PANA protocol involves two functional entities namely the PaC The PANA protocol involves two functional entities namely the PaC
and the PAA. The EP, mentioned in the context with PANA, is a and the PAA. The EP, mentioned in the context with PANA, is a
logical entity. There is, however, the option that the EP is not logical entity. There is, however, the option that the EP is not
physically co-located with the PAA. In case that the PAA and the EP physically co-located with the PAA. In case that the PAA and the EP
are co-located only an API is required instead of a separate are co-located only an API is required instead of a separate
protocol. In the case where the PAA is separated from the EP, a protocol. In the case where the PAA is separated from the EP, a
separate protocol will be used between the PAA and the EP for separate protocol will be used between the PAA and the EP for
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the details are explained in Section 4.2. Although this document the details are explained in Section 4.2. Although this document
describes the interaction with a number of entities and with other describes the interaction with a number of entities and with other
protocol which enable network access authentication; the PANA protocol which enable network access authentication; the PANA
protocol itself is executed between the PaC and the PAA. protocol itself is executed between the PaC and the PAA.
The protocol has three primary functions: The protocol has three primary functions:
1. The PaC discovering the address of the PAA 1. The PaC discovering the address of the PAA
2. The transport of EAP payloads between the PaC and the PAA 2. The transport of EAP payloads between the PaC and the PAA
3. Access authorization by the PAA to the EP [Note that this aspect 3. Access authorization by the PAA to the EP [Note that this aspect
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PANA March 2003
is outside the scope of the PANA protocol.] is outside the scope of the PANA protocol.]
The placement of the entities used in PANA largely depend on a The placement of the entities used in PANA largely depend on a
certain architecture. The PAA may optionally interact with a AAA certain architecture. The PAA may optionally interact with a AAA
backend to authenticate the user (PaC). And in the case where the backend to authenticate the user (PaC). And in the case where the
PAA and EP are co-located, step 3 mentioned above may not require a PAA and EP are co-located, step 3 mentioned above may not require a
separate protocol. The figure below illustrates the interactions in separate protocol. Figure 1 illustrates the interactions in a
a simplified manner: simplified manner:
PaC EP PAA AAA PaC EP PAA AAA
--- --- --- --- --- --- --- ---
PAA Discovery PAA Discovery
<---------------------o-----------------> (1) <---------------------o-----------------> (1)
| PANA_REQUEST | PANA_REQUEST
| ----------------------------------------> | ---------------------------------------->
| AAA interaction | AAA interaction
|(2) -----------> |(2) ----------->
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| |
Authorization Authorization
<----------------- (3) <----------------- (3)
Figure 1: PANA Protocol Figure 1: PANA Protocol
The details of each of these aspects of the protocol are described The details of each of these aspects of the protocol are described
in section 4 of this document. PANA supports authentication of a PaC in section 4 of this document. PANA supports authentication of a PaC
using various EAP methods. The EAP method used depends on the level using various EAP methods. The EAP method used depends on the level
of security required for the EAP messaging itself. PANA does not of security required for the EAP messaging itself. PANA does not
secure the data traffic itself. However EAP methods that enable key secure the data traffic itself. However, EAP methods that enable key
exchange may allow other protocols to be bootstrapped for securing exchange may allow other protocols to be bootstrapped for securing
the data traffic. the data traffic.
From a state machine aspect, PANA protocol consists of three phases From a state machine aspect, PANA protocol consists of three phases
1. Discovery and initial handshake phase 1. Discovery and initial handshake phase
2. Authentication phase 2. Authentication phase
3. Termination phase 3. Termination phase
In the first phase, an IP address of PAA is discovered and a PANA In the first phase, an IP address of PAA is discovered and a PANA
session is established between PaC and PAA. EAP messages are session is established between PaC and PAA. EAP messages are
exchanged and a PANA SA is established in the second phase. The exchanged and a PANA SA is established in the second phase. The
established PANA session as well as a PANA SA is deleted in the established PANA session as well as a PANA SA is deleted in the
third phase. third phase.
4 Protocol Details 4 Protocol Details
Throughout the section, we use a notation "MESSAGENAME_ack" to 4.1 Common Processing Rules
represent a message which is used as an acknowledgment to a message
"MESSAGENAME". In actual message formats, the two messages have the
same message type and are distinguished by an acknowledgment flag
(i.e., A-flag) in PANA header.
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PANA March 2003
4.1. Common Processing Rules
4.1.1. Payload Encoding 4.1.1 Payload Encoding
The payload of any PANA message consists of zero or more AVPs The payload of any PANA message consists of zero or more AVPs
(Attribute Value Pairs). Brief description on the AVPs defined in (Attribute Value Pairs). A brief description of the AVPs defined in
this document is listed below. this document is listed below:
- Cookie AVP: contains a random value that is used for making - Cookie AVP: contains a random value that is used for making
initial handshake robust against blind resource consumption DoS initial handshake robust against blind resource consumption DoS
attacks. attacks.
- Data-Protection AVP: contains a flag which indicates if link-layer - Protection-Cap. AVP: contains information which protection should
or network-layer ciphering should be initiated after PANA. be initiated after the PANA exchange (e.g. link-layer or network
layer protection).
- Device-Id AVP: contains a device identifier of the sender of the - Device-Id AVP: contains a device identifier of the sender of the
message. A device identifier is represented as a pair of device message. A device identifier is represented as a pair of device
identifier type and device identifier value. Either a layer-2 identifier type and device identifier value. Either a layer-2
address or an IP address is used for the device identifier value. address or an IP address is used for the device identifier value.
- EAP AVP: contains an EAP PDU. - EAP AVP: contains an EAP PDU.
- MAC AVP: contains a Message Authentication Code that protects a - MAC AVP: contains a Message Authentication Code that protects a
PANA message PDU. PANA message PDU.
- Revocation-Status AVP: contains the reason of session revocation. - Termination-Cause AVP: contains the reason of session termination.
4.1.2. Transport Layer Protocol - Result-Code AVP: contains information about the protocol execution
results.
- Session-Id AVP: contains the session identifier value.
4.1.2 Transport Layer Protocol
PANA uses UDP as its transport layer protocol. The UDP port number PANA uses UDP as its transport layer protocol. The UDP port number
is TBD. All messages except for PANA_discovery are always unicast. is TBD. All messages except for PANA-PAA-Discover are always
PaC MAY use unspecified IP address for communicating with PAA. unicast. PaC MAY use unspecified IP address for communicating with
PAA.
4.1.3. Fragmentation 4.1.3 Fragmentation
PANA does not provide fragmentation of PANA messages. Instead, it PANA does not provide fragmentation of PANA messages. Instead, it
relies on fragmentation provided by EAP methods and IP layer when relies on fragmentation provided by EAP methods and IP layer when
needed. needed.
4.1.4. Sequence Number and Retransmission 4.1.4 Sequence Number and Retransmission
PANA uses sequence numbers to provide ordered delivery of EAP PANA uses sequence numbers to provide ordered delivery of EAP
messages. The design involves use of two sequence numbers to prevent messages. The design involves use of two sequence numbers to prevent
some of the DoS attacks on the sequencing scheme. Every PANA packet some of the DoS attacks on the sequencing scheme. Every PANA packet
include one transmitted sequence number (tseq) and one received include one transmitted sequence number (tseq) and one received
sequence number (rseq) in the PANA header. See Appendix for sequence number (rseq) in the PANA header. See Appendix for
detailed explanation on why two sequence numbers are needed. detailed explanation on why two sequence numbers are needed.
The two sequence number fields have the same length of N (TBD: The two sequence number fields have the same length of N (TBD:
possibly 32) bits and appear in PANA header. tseq starts from possibly 32) bits and appear in PANA header. tseq starts from
initial sequence number (ISN) and is monotonically increased by 1. initial sequence number (ISN) and is monotonically increased by 1.
The serial number arithmetic defined in [RFC1982] is used for The serial number arithmetic defined in [RFC1982] is used for
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PANA March 2003
sequence number operation. The ISNs are exchanged between PaC and sequence number operation. The ISNs are exchanged between PaC and
PAA during the discovery and initial handshake phase (see section PAA during the discovery and initial handshake phase (see section
"Discovery and Initial Handshake Phase"). The rules that govern the "Discovery and Initial Handshake Phase"). The rules that govern the
sequence numbers in other phases are described as follows. sequence numbers in other phases are described as follows.
o When a message is sent, a new sequence number is placed on the o When a message is sent, a new sequence number is placed on the
tseq field of message regardless of whether it is sent as a result tseq field of message regardless of whether it is sent as a result
of retransmission or not. When a message is sent, rseq is copied of retransmission or not. When a message is sent, rseq is copied
from the tseq field of the last accepted message. from the tseq field of the last accepted message.
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Request based on timer. Other PANA layer messages that require a Request based on timer. Other PANA layer messages that require a
response from the communicating peer are retransmitted based on response from the communicating peer are retransmitted based on
timer at PANA-layer until a response is received (in which case the timer at PANA-layer until a response is received (in which case the
retransmission timer is stopped) or the number of retransmission retransmission timer is stopped) or the number of retransmission
reaches the maximum value (in which case the PANA session MUST be reaches the maximum value (in which case the PANA session MUST be
deleted immediately). For PANA-layer retransmission, the deleted immediately). For PANA-layer retransmission, the
retransmission timer SHOULD be calculated as described in [RFC2988] retransmission timer SHOULD be calculated as described in [RFC2988]
to provide congestion control (TBD: default timer and maximum to provide congestion control (TBD: default timer and maximum
retransmission count suggestions). retransmission count suggestions).
4.1.5. Message Authentication Code 4.1.5 PANA Security Association
A PANA SA is created as an attribute of a PANA session when EAP
authentication succeeds with a creation of a Master Session Key
(MSK) [RFC2284bis]. A PANA SA is not created when the PANA
authentication fails or no MSK is produced by any EAP authentication
method. In the case where two EAP authentications are performed in a
sequence in a single PANA authentication, it is possible that two
MSKs are derived. If this happens, the PANA SA MUST be bound to the
MSK derived from the first EAP authentication. When a new MSK is
derived as a result of EAP-based re-authentication, any key derived
from the old MSK MUST be updated to a new one that is derived from
the new MSK.
The created PANA SA is deleted when the corresponding PANA session
is deleted. The lifetime of the PANA SA is the same as the lifetime
of the PANA session for simplicity.
PANA SA attributes as well as PANA session attributes are listed
below:
PANA Session attributes:
- Session-Id
- Device-Id of PaC
- Device-Id of PAA
- Initial tseq of PaC (ISN_pac)
- Initial tseq of PAA (ISN_paa)
- Last transmitted tseq value
- Last received rseq value
- Last transmitted message payload
- Retransmission interval
- Session lifetime
- Protection-Capability
- PANA SA attributes:
+ MSK
+ PANA_MAC_Key
The PANA_MAC_Key is used to integrity protect PANA messages and
derived from the MSK in the following way:
PANA_MAC_KEY = The first N-bit of
HMAC_SHA1(MSK, ISN_pac | ISN_paa | Session-ID)
where the value of N depends on the integrity protection algorithm
in use, i.e., N=128 for HMAC-MD5 and N=160 for HMAC-SHA1.
The length of MSK MUST be N-bit or longer. See section 4.1.6 for
the detailed usage of the PANA_MAC_Key.
4.1.6 Message Authentication Code
A PANA message can contain a MAC (Message Authentication Code) AVP A PANA message can contain a MAC (Message Authentication Code) AVP
for cryptographically protecting the message. for cryptographically protecting the message.
When a MAC AVP is included in a PANA message, the value field of the When a MAC AVP is included in a PANA message, the value field of the
MAC AVP is calculated in the following way: MAC AVP is calculated by using the PANA_MAC_Key in the following
way:
MAC AVP value = PRF(PANA_MAC_Key, PANA_PDU) MAC AVP value = HMAC_SHA1(PANA_MAC_Key, PANA_PDU)
where PANA_PDU is the PANA message including the PANA header, with where PANA_PDU is the PANA message including the PANA header, with
the MAC AVP value field first initialized to 0. The default the MAC AVP value field first initialized to 0.
algorithm used for the PRF function is TBD (possibly HMAC-SHA1).
PANA_MAC_Key MUST be derived from the Master Session Key (MSK) and
thus MUST be a part of the EAP key hierarchy [Ab02]. Detailed
derivation algorithm is TBD.
4.1.6. Message Validity Check 4.1.7 Message Validity Check
When a PANA message is received, the message is considered to be When a PANA message is received, the message is considered to be
invalid at least when one of the following conditions are not met: invalid at least when one of the following conditions are not met:
o Each field in the message header contains a valid value including o Each field in the message header contains a valid value including
sequence number, message length, message type, version number, sequence number, message length, message type, version number,
flags, flags, etc.
etc.
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PANA March 2003
o When a device identifier of the communication peer is bound to the o When a device identifier of the communication peer is bound to the
PANA session, it matches the device identifier carried in MAC and/or PANA session, it matches the device identifier carried in MAC and/or
IP header(s). IP header(s).
o The message type is one of the expected types in the current o The message type is one of the expected types in the current
state. state.
o The message payload contains a valid set of AVPs allowed for the o The message payload contains a valid set of AVPs allowed for the
message type and there is no missing AVP that needs to be included message type and there is no missing AVP that needs to be included
in in the payload.
the payload.
o Each AVP is decoded correctly. o Each AVP is decoded correctly.
o When a MAC AVP is included, the AVP value matches the MAC value o When a MAC AVP is included, the AVP value matches the MAC value
computed computed against the received message.
against the received message.
o When a Device-Id AVP is included, the AVP is valid if the device o When a Device-Id AVP is included, the AVP is valid if the device
identifier type contained in the AVP matches the expected one (this identifier type contained in the AVP matches the expected one (this
check is for PAA only) and the device identifier value contained in check is for PAA only) and the device identifier value contained in
the AVP matches the value extracted from the lower-layer the AVP matches the value extracted from the lower-layer
encapsulation encapsulation header corresponding to the device identifier type
header corresponding to the device identifier type contained in the contained in the AVP.
AVP.
Invalid messages MUST be discarded in order to provide robustness Invalid messages MUST be discarded in order to provide robustness
against DoS attacks and an unprotected. (TBD: in addition, a against DoS attacks and an unprotected. (TBD: in addition, a
non-acknowledged error notification message MAY be returned to the non-acknowledged error notification message MAY be returned to the
sender.) sender.)
4.2. Discovery and Initial Handshake Phase 4.2 Discovery and Initial Handshake Phase
When a PaC attaches to a network, and knows that it has to discover When a PaC attaches to a network, and knows that it has to discover
PAA for PANA, it can send a PANA_discovery message to a well-known PAA for PANA, it can send a PANA-PAA-Discover message to a well-
link local multicast address (TBD) over UDP. The source address known link local multicast address (TBD) and UDP port (TBD). The
may be unspecified IP address if the PaC has not configured an source address is set to the unspecified IP address if the PaC has
address yet. In all PAA_discovery messages, both tseq and rseq not configured an address yet. PANA PAA discovery assumes that PaC
fields of the header are set to zero (0). PANA PAA discovery and PAA are one hop away from each other. If PaC knows the IP
assumes that PaC and PAA are one hop away from each other. If PaC address of the PAA (some pre-configuration), it can unicast the PANA
knows the IP address of the PAA (some pre-configuration), it can discovery message to that address. PAA answers to the PANA-PAA-
unicast the PANA_discovery message to that address. PAA answers to Discover message with a PANA-Start-Request message.
the PANA_discovery message with a PANA_start message.
When the PAA receives such a request, or upon receiving some lower When the PAA receives such a request, or upon receiving some lower
layer indications of a new PaC, PAA can unicast a PANA_start layer indications of a new PaC, PAA can unicast a PANA-Start-Request
message. The destination address may be unspecified IP address, message. The destination address may be unspecified IP address, but
but the L2 destination would be a unicast address (something for the L2 destination would be a unicast address (something for the
the implementations to deal with). This message announces the PAA implementations to deal with).
to the PaC.
There can be multiple PAAs on the link. The result does not depend There can be multiple PAAs on the link. The result does not depend
on which PAA PaC chooses. By default PaC chooses the PAA that sent on which PAA PaC chooses. By default PaC chooses the PAA that sent
the first response. the first response.
Tschofenig (ed.) Expires September 2003 8
PANA March 2003
PaC may also choose to start sending packets before getting PaC may also choose to start sending packets before getting
authenticated. In that case, the network should detect this and authenticated. In that case, the network should detect this and send
send an unsolicited PANA_start message to PaC. EP is the node that an unsolicited PANA-Start-Request message to PaC. EP is the node
can detect such activity. If EP and PAA are co-located, then an that can detect such activity. If EP and PAA are co-located, then an
internal mechanism (e.g. API) between the EP module and the PAA internal mechanism (e.g. API) between the EP module and the PAA
module on the same host can prompt PAA to start PANA. In case they module on the same host can prompt PAA to start PANA. In case they
are separate, there needs to an explicit message to prompt PAA. are separate, there needs to an explicit message to prompt PAA. Upon
Upon detecting the need to authenticate a client, EP can send a detecting the need to authenticate a client, EP can send a PANA-PAA-
PAC_discovery message to the PAA on behalf of the PaC. This Discover message to the PAA on behalf of the PaC. This message
message carries a device identifier of the PaC in a Device-Id AVP. carries a device identifier of the PaC in a Device-ID AVP. So that,
So that, PAA can send the unsolicited PANA_start message directly the PAA can send the unsolicited PANA-Start-Request message directly
to the PaC. If the link between the EP and PAA is not secure, the to the PaC. If the link between the EP and PAA is not secure, the
PAC_discover message sent from EP to PAA MUST be protected by PANA-PAA-Discover message sent from the EP to the PAA MUST be
using, e.g., IPsec. protected by using.
PANA_start message contains a cookie carried in a Cookie AVP in the A PANA-Start-Request message contains a cookie carried in a Cookie
payload, respectively. The rseq field of the header is set to zero AVP in the payload, respectively. The rseq field of the header is
(0). The tseq field of the header contains the initial sequence set to zero (0). The tseq field of the header contains the initial
number. The cookie is used for preventing the PAA from resource sequence number. The cookie is used for preventing the PAA from
consumption DoS attacks by blind attackers. The cookie is computed resource consumption DoS attacks by blind attackers. The cookie is
in such a way as not to require any saved per-session state to computed in such a way as not to require any saved per-session state
recognize its valid cookie when a particular message sent by the to recognize its valid cookie when a particular message sent by the
PaC in response to the PANA_start message arrives. The exact PaC in response to the PANA-Start-Request message arrives. The
algorithms and syntax used for generating cookies does not affect exact algorithms and syntax used for generating cookies does not
interoperability and hence is not specified here. An example affect interoperability and hence is not specified here. An example
algorithm is described below. algorithm is described below.
Cookie = Cookie =
<secret-version> | HMAC_SHA1( <Device-Id of PaC> | <secret> ) <secret-version> | HMAC_SHA1( <Device-Id of PaC> | <secret> )
where <secret> is a randomly generated secret known only to the where <secret> is a randomly generated secret known only to the
PAA, <secret-version> is an index used for choosing the secret for PAA, <secret-version> is an index used for choosing the secret for
generating the cookie and '|' indicates concatenation. The generating the cookie and '|' indicates concatenation. The secret-
secret-version should be changed frequently enough to prevent version should be changed frequently enough to prevent replay
replay attacks. attacks. The secret key is locally known to the PAA only and valid
for a certain time frame.
When a PaC receives the PANA_start message, it responds with a When a PaC receives the PANA-Start-Request message in response to
PANA_start message. The PANA_start message sent from the PaC the PANA-PAA-Discover message, it responds with a PANA-Start-Answer
contains the initial sequence numbers in the tseq and rseq fields message. The PANA-Start-Answer message contains the initial sequence
of the PANA header, a copy of the received Cookie as the PANA numbers in the tseq and rseq fields of the PANA header, a copy of
payload. the received Cookie as the PANA payload.
When the PAA receives the PANA_start message from the PaC, it When the PAA receives the PANA-Start-Request message from the PaC,
verifies the cookie. The cookie is considered as valid if the it verifies the cookie. The cookie is considered as valid if the
received cookie has the expected value. If the computed cookie is received cookie has the expected value. If the computed cookie is
valid, the protocol enters the authentication phase. Otherwise, it valid, the protocol enters the authentication phase. Otherwise, it
MUST silently discard the received message. MUST silently discard the received message.
PANA_start exchange is needed before entering authentication phase The PANA-Start-Request/Answer exchange is needed before entering
even when the PaC is pre-configured with PAAs IP address and the authentication phase even when the PaC is pre-configured with PAAs
PANA_discover is a unicast message. IP address and the PANA-PAA-Discover message is unicast.
PANA_start message sent from PAA is never retransmitted.
PANA_start message sent from PaC is retransmitted based on timer in
the same manner as other messages retransmitted at PANA-layer.
Tschofenig (ed.) Expires September 2003 9 A PANA-Start-Request message is never retransmitted. A PANA-Start-
PANA March 2003 Answer message is retransmitted based on timer in the same manner as
other messages retransmitted at PANA-layer.
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message
------------------------------------------------------ ------------------------------------------------------
-----> PANA_discover(0,0) -----> PANA-PAA-Discover(0,0)
<----- PANA_start(x,0)[Cookie] <----- PANA-Start-Request(x,0)[Cookie]
-----> PANA_start(y,x)[Cookie] -----> PANA-Start-Answer(x,y)[ Cookie]
(continued to authentication phase) (continued to authentication phase)
(PANA_discover sent by PaC) (PANA-PAA-Discover sent by PaC)
Figure 2: Example Sequence for Discovery and Initial Handshake Phase Figure 2: Example Sequence for Discovery and Initial Handshake Phase
PaC EP PAA Message(tseq,rseq)[AVPs] PaC EP PAA Message
------------------------------------------------------ ------------------------------------------------------
---->o (Data packet arrival or L2 trigger) ---->o (Data packet arrival or L2 trigger)
------> PANA_discover(0,0)[Device-Id] ------> PANA-PAA-Discover(0,0)[Device-Id]
<------------ PANA_start(x,0)[Cookie] <------------ PANA-Start-Request(x,0)[ Cookie]
------------> PANA_start(y,x)[Cookie] ------------> PANA-Start-Answer(y,x)[ Cookie]
(continued to authentication phase) (continued to authentication phase)
(PANA_discover sent by EP) (PANA-PAA-Discover sent by EP)
Figure 3: Example Sequence for Discovery and Initial Handshake Phase Figure 3: Example Sequence for Discovery and Initial Handshake Phase
4.3. Authentication Phase 4.3 Authentication Phase
The main task in authentication phase is to carry EAP messages The main task in authentication phase is to carry EAP messages
between PaC and PAA. All EAP messages except for EAP between PaC and PAA. All EAP messages except for EAP Success/Failure
Success/Failure messages are carried in PANA_auth messages. When an messages are carried in the PANA-Auth-Request/PANA-Auth-Answer
EAP Success/Failure message is sent from a PAA, the message is messages. When an EAP Success/Failure message is sent from a PAA,
carried in PANA_success or PANA_failure messages. PANA_success and the message is carried in the PANA-Bind-Request message. The PANA-
PANA_failure messages are acknowledged with PANA_success_ack and Bind-Request message is acknowledged with a PANA-Bind-Answer. It is
PANA_failure_ack messages, respectively. It is possible to carry possible to carry multiple EAP sequences in a single PANA sequence.
multiple EAP sequences in a single PANA sequence, with using a
PANA_success or a PANA_failure message as a delimiter of each EAP
sequence. An EAP Success or an EAP Failure message is carried in a
PANA_success or a PANA_failure message, respectively.
A single PANA session can enable more than one EAP authentication. A single PANA session can enable more than one EAP authentication.
This is used to satisfy the separate NAP and ISP authentications This is used to satisfy the separate NAP and ISP authentications
scenario. Each EAP authentication is delineated from the subsequent scenario. Each EAP authentication is delineated from the subsequent
one with a PANA_success or PANA_failure message. F-flag in the PANA one. The F-flag in the PANA header indicates if this was the final
header indicates if this was the final authentication from sender's authentication from sender's perspective. If the PAA enables two
perspective. If PAA enables two separate authentication, it should separate authentication, it should not set the F-flag in after the
not set F-flag in the PANA_success or PANA_failure message after the
first EAP method. This indicates PAA's willingness to offer another first EAP method. This indicates PAA's willingness to offer another
authentication method for NAP-ISP separation. PaC can respond with authentication method for NAP-ISP separation. PaC can respond with
a F-flag unset, indicating PaC's willingness to go through a second the F-flag unset, indicating PaC's willingness to go through a
authentication method. PaC can optionally decline by setting the second authentication method. The PaC can optionally decline by
F-flag, and this concludes the PANA authentication. If PAA does not setting the F-flag, and this concludes the PANA authentication. If
offer two levels of authentication, then it sets the F-flag even at the PAA does not offer two levels of authentication, then it sets
the F-flag even at the end of first EAP exchange. In that case the
Tschofenig (ed.) Expires September 2003 10 PaC has no other option but to set the F-flag to mark the end of
PANA March 2003 PANA authentication.
the end of first EAP method. In that case PaC has no other option
but to set the F-flag to mark the end of PANA authentication.
Currently, use of multiple EAP methods in PANA is designed only for Currently, use of multiple EAP methods in PANA is designed only for
NAP-ISP authentication separation. It is not for arbitrary EAP NAP-ISP authentication separation. It is not for arbitrary EAP
method sequencing, or giving PaC another chance when an method sequencing, or giving the PaC another chance when an
authentication method fails. NAP and ISP authentication are authentication method fails. The NAP and ISP authentication are
considered completely independent. Presence or success of one considered completely independent. Presence or success of one
should not effect the other. Making a decision based on the success should not effect the other. Making a decision based on the success
or failure of each authentication is a network policy issue. A or failure of each authentication is a network policy issue. PANA
PANA_success or PANA_failure message is only qualified to signal the signals only the result of the immediately preceding EAP
result of immediately preceding authentication method. authentication method.
When an EAP method that is capable of deriving keys is used during When an EAP method that is capable of deriving keys is used during
the authentication phase and the keys are successfully derived, the authentication phase and the keys are successfully derived all
PANA_success, PANA_success_ack, PANA_failure, PANA_failure_ack subsequent PANA messages MUST contain a MAC AVP. The PANA-Bind-
messages MUST contain a MAC AVP. The PANA_success and Request and the PANA-Bind-Answer message exchange is also used for
PANA_success_ack message exchange also is used for binding device binding device identifiers of the PaC and the PAA to the PANA SA.
identifiers of the PaC and PAA to the PANA SA. To achieve this, To achieve this, the PANA-Bind-Request and the PANA-Bind-Answer
PANA_success and PANA_success_ack messages SHOULD contain a device SHOULD contain a device identifier of the PAA and the PaC,
identifier of the PAA and PaC, respectively, in a Device-Id AVP. respectively, in a Device-Id AVP. The PaC MUST use the same type of
The PaC MUST use the same type of device identifier as contained in device identifier as contained in the PANA-Bind-Request message.
the PANA_success message. In this case, the device identifier type The PANA-Bind-Request message MAY also contain a Protection-Capability
contained in the PANA_success message indicates the device AVP to indicate if link-layer or network-layer ciphering should be
identifier type that the PaC needs to use. Validity check on the initiated after PANA. No link layer or network layer specific
device identifier MUST be performed for these messages (see section information is included in the Protection-Capability AVP. When the
"Message Validity Check"). information is preconfigured on the PaC and the PAA this AVP can be
omitted. It is assumed that at least PAA is aware of the security
PANA_success message MAY also contain a Data-Protection AVP to capabilities of the access network. The PANA protocol does not
indicate if link-layer or network-layer ciphering should be specify how the PANA SA and the Protection-Capability AVP will be
initiated after PANA. A bit flag is the only information carried in used to provide per-packet protection for data traffic.
the AVP and it states whether PANA SA will be used with link-layer
ciphers (e.g., WEP) or network-layer ciphers (e.g, IKE and IPsec).
It does not carry any other information specific to ciphering
methods at all. When the information is preconfigured on PaC and
PAA this AVP can be omitted. It is assumed that at least PAA is
aware of the security capabilities of the access network. PANA
protocol does not specify how the PANA SA and the Data-Protection
AVP will be used to provide per-packet protection for data traffic.
PANA_success and PANA_failure messages MUST be retransmitted based
on the retransmission rule described in section "Sequence Number and
Retransmission".
Tschofenig (ed.) Expires September 2003 11 PANA-Bind-Request and PANA-Bind-Answer messages MUST be
PANA March 2003 retransmitted based on the retransmission rule described in Appendix
A.
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------- -------------------------------------------------
(continued from discovery and initial handshake phase) (continued from discovery and initial handshake phase)
<----- PANA_auth(x+1,y)[EAP{Request}] <----- PANA-Auth-Request(x+1,y)[EAP{Request}]
-----> PANA_auth(y+1,x+1)[EAP{Response}] -----> PANA-Auth-Answer(y+1,x+1)[EAP{Response}]
. .
. .
<----- PANA_auth(x+2,y+1)[EAP{Request}] <----- PANA-Auth-Request (x+2,y+1)[EAP{Request}]
-----> PANA_auth(y+2,x+2)[EAP{Response}] -----> PANA-Auth-Answer (y+2,x+2)[EAP{Response}]
<----- PANA_success(x+3,y+2) // F-flag set <----- PANA-Bind-Request(x+3,y+2) // F-flag
[EAP{Success}, Device-Id, Data-Protection, MAC] set
-----> PANA_success_ack(y+3,x+3) [EAP{Success}, Device-Id, Protection-Cap., MAC]
[Device-Id, MAC] // F-flag set -----> PANA-Bind-Answer(y+3,x+3)
[Device-Id, Protection-Cap., MAC] // F-flag set
Figure 4: Example Sequence in Authentication Phase Figure 4: Example Sequence in Authentication Phase
4.4. Re-authentication 4.4 Re-authentication
There are two types of re-authentication supported by PANA. There are two types of re-authentication supported by PANA.
The first type of re-authentication is based on EAP by entering the The first type of re-authentication is based on EAP by entering an
authentication phase. In this case, the discovery and initial authentication phase. In this case, some or all message exchanges
handshake phase MAY be omitted. If there is an established PANA SA, for discovery and initial handshake phase MAY be omitted in the
PANA_auth messages MAY be protected by adding a MAC AVP to each following way. When a PaC initiates EAP-based re-authentication, it
sends a PANA-PAA-Discovery message to the PAA. If the PAA already
has an established PANA session for the PaC with a device identifier
that matches the one extracted from the MAC header and/or IP header
of the PANA-PAA-Discover message, it sends a PANA-Auth-Request
message with the session identifier for that PANA session to start
an authentication phase. When the PAA initiates EAP-based re-
authentication, it sends a PANA-Auth-Request message with the
session identifier for the PaC to enter an authentication phase. In
both cases, the tseq and rseq values are inheritated from the
previous (re-)authentication. For any EAP-based re-authentication,
if there is an established PANA SA, PANA-Auth-Request and PANA-Auth-
Answer messages MAY be protected by adding a MAC AVP to each
message. message.
The second type of re-authentication is based on a single protected The second type of re-authentication is based on a single protected
message exchange without entering the authentication phase. message exchange without entering the authentication phase.
PANA_reauth/PANA_reauth_ack messages are used for this purpose. If PANA-Reauth-Request and PANA-Reauth-Answer messages are used for
there is an established PANA SA, both PaC and PAA can send a this purpose. If there is an established PANA SA, both the PaC and
PANA_reauth message to the communicating peer whenever it needs to the PAA are allowed to send a PANA-Reauth-Request message to the
make sure the availability of the PANA SA on the peer and expect the communicating peer whenever it needs to make sure the availability
peer to return a PANA_reauth_ack message. Both PANA_reauth / of the PANA SA on the peer and expect the peer to return a PANA-
PANA_reauth_ack messages MUST be protected with a MAC AVP. Reauth-Answer message. Both PANA-Reauth-Request/ PANA-Reauth-Answer
messages MUST be protected with a MAC AVP.
Implementations MUST limit the rate of performing re-authentication Implementations MUST limit the rate of performing re-authentication
for both types of re-authentication. for both types of re-authentication.
Tschofenig (ed.) Expires September 2003 12
PANA March 2003
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------------ ------------------------------------------------------
-----> PANA_reauth(q,p)[MAC] -----> PANA-Reauth-Request(q,p)[MAC]
<----- PANA_reauth_ack(p+1,q)[MAC] <----- PANA-Reauth-Answer(p+1,q)[MAC]
Figure 5: Example Sequence for PaC-initiated Re-authentication Figure 5: Example Sequence for PaC-initiated Re-authentication
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------------ ------------------------------------------------------
<----- PANA_reauth(p,q)[MAC] <----- PANA-Reauth-Request(p,q)[MAC]
-----> PANA_reauth_ack(q+1,p)[MAC] -----> PANA-Reauth-Answer(q+1,p)[MAC]
Figure 6: Example Sequence for PAA-initiated Re-authentication Figure 6: Example Sequence for PAA-initiated Re-authentication
4.5. Termination Phase 4.5 Termination Phase
A procedure for explicitly terminating a PANA session can be A procedure for explicitly terminating a PANA session can be
initiated either from PaC (i.e., disconnect indication) or from PAA initiated either from PaC (i.e., disconnect indication) or from PAA
(i.e., session revocation). PANA_disconnect/PANA_disconnect_ack and (i.e., session revocation). The PANA-Termination-Request and the
PANA_revocation/PANA_revocation_ack message exchanges are used for PANA-Termination-Answer message exchanges are used for
disconnect indication and session revocation procedures, disconnect indication and session revocation procedures.
respectively.
A PANA_revocation message contains the reason of revocation in
Revocation-Status AVP. When there is an established PANA SA
established between the PaC and PAA, all messages exchanged during
the termination phase MUST be protected with a MAC AVP. When the
sender of PANA_disconnect or PANA_revocation message receives a
valid acknowledgment, all states maintained for the PANA session
MUST be deleted immediately.
PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------------
-----> PANA_disconnect(q,p)[MAC]
<----- PANA_disconnect_ack(p+1,q)[MAC]
Figure 7: Example Sequence for Disconnect Indication The reason for termination is indicated in the Termination-Cause
AVP. When there is an established PANA SA established between the
PaC and the PAA, all messages exchanged during the termination phase
MUST be protected with a MAC AVP. When the sender of the PANA-
Termination-Request receives a valid acknowledgment, all states
maintained for the PANA session MUST be deleted immediately.
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
------------------------------------------------------ ------------------------------------------------------
<----- PANA_revocation(p,q)[Revocation-Status,MAC] -----> PANA-Termination-Request(q,p)[MAC]
-----> PANA_revocation_ack(q+1,p)[MAC] <----- PANA-Termination-Answer(p+1,q)[MAC]
Figure 8: Example Sequence for Session Revocation
4.6. Illustration of a Complete Message Sequence Figure 7: Example Sequence for Session Termination
A complete PANA message sequence is illustrated in Figure 5.6. The 4.6 Illustration of a Complete Message Sequence
example assumes the following scenario.
Tschofenig (ed.) Expires September 2003 13 A complete PANA message sequence is illustrated in Figure 8. The
PANA March 2003 example assumes the following scenario:
- PaC multicasts PANA_discover message - PaC multicasts PANA-PAA-Discover message
- ISNs used by PAA and PaC are x and y, respectively. - The ISNs used by the PAA and the PaC are x and y, respectively.
- A single EAP sequence is used in authentication phase. - A single EAP sequence is used in authentication phase.
- A single EAP authentication method is used in the EAP sequence. - An EAP authentication method with a single round trip is used in
the EAP sequence.
- The EAP authentication method derives keys. PANA SA is - The EAP authentication method derives keys. The PANA SA is
established based on the keys. established based on the unique and fresh session key provided by
the EAP method.
- After PANA SA is established, all messages are integrity protected - After PANA SA is established, all messages are integrity and
with MAC AVP. replay protected with the MAC AVP.
- Re-authentication based on PANA_reauth/PANA_reauth_ack exchange is - Re-authentication based on the PANA-Reauth-Request/ PANA-Reauth-
performed. Answer exchange is performed.
- PANA session is terminated as a result of disconnect indication - The PANA session is terminated as a result of the PANA-
from PaC. Termination-Request indication from the PaC.
PaC PAA Message(tseq,rseq)[AVPs] PaC PAA Message(tseq,rseq)[AVPs]
----------------------------------------------------- -----------------------------------------------------
// Discovery and initial handshake phase // Discovery and initial handshake phase
-----> PANA_discover(0,0) -----> PANA-PAA-Discover (0,0)
<----- PANA_start(x,0)[Cookie] <----- PANA-Start-Request (x,0)[Cookie]
-----> PANA_start(y,x)[Cookie] -----> PANA-Start-Request-Answer (y,x)[Cookie]
// Authentication phase // Authentication phase
<----- PANA_auth(x+1,y)[EAP] <----- PANA-Auth-Request(x+1,y)[EAP]
-----> PANA_auth(y+1,x+1)[EAP] -----> PANA-Auth-Answer(y+1,x+1)[EAP]
<----- PANA_auth(x+2,y+1)[EAP] <----- PANA-Auth-Request(x+2,y+1)[EAP]
-----> PANA_auth(y+2,x+2)[EAP] -----> PANA-Auth-Answer(y+2,x+2)[EAP]
<----- PANA_success(x+3,y+2) // F-flag set <----- PANA-Bind-Request(x+3,y+2) // F-flag set
[EAP, Device-Id, Data-Protection, MAC] [EAP, Device-Id, Data-Protection, MAC]
-----> PANA_success_ack(y+3,x+3) // F-flag set -----> PANA-Bind-Answer(y+3,x+3) // F-flag set
[Device-Id, MAC] [Device-Id, Data-Protection, MAC]
// Re-authentication // Re-authentication
<----- PANA_reauth(x+4,y+3)[MAC] <----- PANA-Reauth-Request (x+4,y+3)[MAC]
-----> PANA_reauth_ack(y+4,x+4)[MAC] -----> PANA-Reauth-Answer (y+4,x+4)[MAC]
// Termination phase // Termination phase
-----> PANA_disconnect(y+5,x+4)[MAC] -----> PANA-Termination-Request(y+5,x+4)[MAC]
<----- PANA_disconnect_ack(x+5,y+5)[MAC] <----- PANA-Termination-Answer (x+5,y+5)[MAC]
Figure 9: A Complete Message Figure 8: A Complete Message Sequence
4.7. Device ID choice 4.7 Device ID choice
PaC has to pick a device identifier to provide for PANA exchanges. PaC has to pick a device identifier to provide for PANA exchanges.
In this version of the specification, device ID is considered to be In this version of the specification, device ID is considered to be
Tschofenig (ed.) Expires September 2003 14
PANA March 2003
fixed. Future versions might enable changing it during a PANA fixed. Future versions might enable changing it during a PANA
session. session.
A PaC will configure an IP address before PANA if it can. It might A PaC will configure an IP address before PANA if it can. It might
either have a pre-configured IP address, or have to obtain one via either have a pre-configured IP address, or have to obtain one via
dynamic methods such as DHCP or stateless address autoconfiguration. dynamic methods such as DHCP or stateless address autoconfiguration.
Dynamic methods may or may not succeed depending on the local Dynamic methods may or may not succeed depending on the local
security policy. In networks where the PaCs need to use PANA prior security policy. In networks where the PaCs need to use PANA prior
to address configuration, EPs will detect the PaCs attempt to get IP to address configuration, EPs will detect the PaCs attempt to get IP
address and help PAA to initiate authentication. address and help PAA to initiate authentication.
skipping to change at line 772 skipping to change at page 18, line 31
DI at any time. The only case an IP address should be used as DI at any time. The only case an IP address should be used as
device ID is when IPsec will be used for protecting data traffic device ID is when IPsec will be used for protecting data traffic
after initial authentication. Any other time a link-layer address after initial authentication. Any other time a link-layer address
can be used by both PAA and PaC as device ID. It is assumed that PAA can be used by both PAA and PaC as device ID. It is assumed that PAA
knows the security mechanisms being provided or required on the knows the security mechanisms being provided or required on the
access network (e.g., physical security, link-layer ciphers prior to access network (e.g., physical security, link-layer ciphers prior to
PANA, link-layer ciphers enabled after PANA, IPsec). When IPsec is PANA, link-layer ciphers enabled after PANA, IPsec). When IPsec is
the choice of data ciphering, PAA should provide its IP address as the choice of data ciphering, PAA should provide its IP address as
device ID, and expect the PaC to provide its IP address if it has device ID, and expect the PaC to provide its IP address if it has
one. In all other cases, link-layer addresses can be provided from one. In all other cases, link-layer addresses can be provided from
both sides. [TBD: can we allow IP address allocation after PANA and both sides.
still be able to use IPsec?]
4.8. PaC Implications When IPsec ciphering is used but the PaC uses an unspecified IP
address in the authentication phase, it MUST use its MAC address for
the device identifier until the PaC is configured with a specified
IP address that is used for IPsec ciphering. Once such a specified
IP address is configured, the PaC MUST update the device identifier
registered on the PAA from the MAC address to the IP address by
initiating a PANA-Reauth-Request/PANA-Reauth-Answer exchange in
which the IP address of the PaC is contained in the Device-Id AVP
contained in the PANA-Reauth-Request message sent from the PaC.
4.8 Refresh Interval Negotiation
The authentication phase also determines the PANA session lifetime
when authorization succeeds. The Session-Lifetime AVP (to be
defined, Code XXX) is used to determine the valid lifetime of PANA
session. This AVP MUST NOT be included in any message other than the
PANA-Bind-Request and PANA-Bind-Anser message. It MUST be ignored
when received in other messages or the authorization result is a
failure.
This AVP carries the maximum session lifetime offered by the network
when included in the PANA-Bind-Request sent by the PAA. If it is
omitted, or contains the value 0xFFFFFFFF, this means the session
lifetime is infinity. This AVP carries the requested session
lifetime when it is sent by the PaC. If requested session lifetime
is greater than the offered lifetime, then it is ignored and the
offered lifetime becomes the session lifetime. The requested
lifetime becomes the session lifetime if it is less than or equal to
the offered lifetime. The PaC MUST perform a PANA authentication (by
sending a PANA-Auth-Request andnot a PANA-Reauth-Request) before the
session lifetime expires. Failure to do so yields in PaC losing
network access.
4.9 Mobility Handling
If PaC wants to resume an ongoing PANA session after connecting to
another link in the same access network, it can send the unexpired
PANA session id in its PANA-Start-Request message. In the absence of
session id AVP in this message, PAA can assume this is a fresh
session and assigns a new session ID in the first PANA-Auth-Request
message.
If PAA receives a session id in the PANA-Start-Request message, and
it is configured to enable fast re-authentication, it SHOULD
retrieve the PANA SA from the previous PAA of the PaC. Determining
the previous PAA of the PaC by using the PANA session id is outside
the scope of this protocol. A possible solution is to embed thePAA
identifier into the message. Furthermore, the mechanism required to
retrieve the PANA SA from the previous PAA is outside the scope of
PANA protocol. Seamoby Context Transfer Protocol [CTP] might be
useful here.
If the PAA is not configured to enable fast re-authentication, or
can not retrieve the PANA SA, or the PANA SA has expired, the PAA
MUST send the PANA-Start-Request message with a new session id and
let the PANA exchange take its usual course. Otherwise, PAA MUST
continue the PANA session with a PANA_Reauth exchange (rather than
PANA_Auth exchange which, in most of the times, means full
authentication). Device ID AVPs MUST be included in this exchange to
bind the new DIs to the PANA SA.
TBD: This is a proposal and requires further thoughts.
4.10 Event Notification
Upon detecting the need to authenticate a client, EP can send a
trigger message to the PAA on behalf of the PaC. This can be one of
the messages provided by the PAA-to-EP protocol, or, in the absence
of such a facility, PANA-PAA_Discover can be used as well. This
message MUST carry the device identifier of the PaC. So that, the
PAA can send the unsolicited PANA-Start-Request message directly to
the PaC. If the link between the EP and PAA is not physically
secured, this message sent from EP to PAA MUST be cryptographically
protected (e.g., by using IPsec).
4.11 PaC Implications
- PaC state machine. [TBD] - PaC state machine. [TBD]
4.9. PAA Implications 4.12 PAA Implications
- PAA state machine. [TBD] - PAA state machine. [TBD]
5 PANA Security Association Establishment 5 PANA Security Association Establishment
When PANA is used over an already established secure channel, such When PANA is used over an already established secure channel, such
as physically secured wires or ciphered link-layers, we can as physically secured wires or ciphered link-layers, we can
reasonably assume that man-in-the-middle attack or service theft is reasonably assume that man-in-the-middle attack or service theft is
not possible [THREATS]. not possible [THREATS].
skipping to change at line 802 skipping to change at page 20, line 37
identifier that is used during the authentication needs to be identifier that is used during the authentication needs to be
verified at the end of the authentication to prevent service theft verified at the end of the authentication to prevent service theft
and DoS attacks. Additionally, a free loader should be prevented and DoS attacks. Additionally, a free loader should be prevented
from spoofing data packets by using the device identifier of an from spoofing data packets by using the device identifier of an
already authorized legitimate client. Both of these requirements already authorized legitimate client. Both of these requirements
necessitate generation of a security association between the necessitate generation of a security association between the
PaC and the PAA at the end of the authentication. This can only be PaC and the PAA at the end of the authentication. This can only be
done when the authentication method used can generate cryptographic done when the authentication method used can generate cryptographic
keys. Use of secret keys can prevent attacks which would otherwise keys. Use of secret keys can prevent attacks which would otherwise
be very easy to launch by eavesdropping on and spoofing traffic over be very easy to launch by eavesdropping on and spoofing traffic over
a insecure links. an insecure link.
Tschofenig (ed.) Expires September 2003 15
PANA March 2003
PANA relies on EAP and the EAP methods to provide a session key in PANA relies on EAP and the EAP methods to provide a session key in
order to establish a PANA security association. An example of such a order to establish a PANA security association. An example of such a
method is EAP-TLS [EAPTLS], whereas EAP-MD5 [RFC2284] is an example method is EAP-TLS [EAPTLS], whereas EAP-MD5 [RFC2284] is an example
of a method that cannot create such keying material. The choice of of a method that cannot create such keying material. The choice of
EAP method becomes important, as already discussed in the next EAP method becomes important, as already discussed in the next
section. section.
This keying material is already used within PANA during the final This keying material is already used within PANA during the final
handshake. This handshake ensures that the device identifier that is handshake. This handshake ensures that the device identifier that is
skipping to change at line 841 skipping to change at page 21, line 24
the network. the network.
The authentication method choice is a function of the underlying The authentication method choice is a function of the underlying
security of the network (e.g., physically secured, shared link, security of the network (e.g., physically secured, shared link,
etc.). It is the responsibility of the user and the network operator etc.). It is the responsibility of the user and the network operator
to pick the right method for authentication. PANA carries EAP to pick the right method for authentication. PANA carries EAP
regardless of the EAP method used. It is outside the scope of PANA regardless of the EAP method used. It is outside the scope of PANA
to mandate, recommend, or limit use of any authentication methods. to mandate, recommend, or limit use of any authentication methods.
PANA cannot increase the strength of a weak authentication method to PANA cannot increase the strength of a weak authentication method to
make it suitable for an insecure environment. There are some EAP- make it suitable for an insecure environment. There are some EAP-
based approaches to achieve this goal [PEAP][TTLS]. PANA based approaches to achieve this goal (see [PEAP],[TTLS],[EAP-
can carry these EAP encapsulating methods but it does not concern IKEv2]). PANA can carry these EAP encapsulating methods but it does
itself with how they achieve protection for the weak methods (i.e., not concern itself with how they achieve protection for the weak
their EAP method payloads). methods (i.e., their EAP method payloads).
7 Filter Rule Installation 7 Filter Rule Installation
PANA protocol provides client authentication and authorization PANA protocol provides client authentication and authorization
functionality for securing network access. The other component of a functionality for securing network access. The other component of a
complete solution is the access control which ensures that only complete solution is the access control which ensures that only
authenticated and authorized clients can gain access to the network. authenticated and authorized clients can gain access to the network.
PANA enables access control by identifying legitimate clients and PANA enables access control by identifying legitimate clients and
generating filtering information for access control mechanisms. generating filtering information for access control mechanisms.
Getting this filtering information to the EPs (enforcement points) Getting this filtering information to the EPs (Enforcement Points)
and performing filtering are outside the scope of PANA. and performing filtering are outside the scope of PANA.
Access control can be achieved by placing EPs in the network for Access control can be achieved by placing EPs in the network for
policing the traffic flow. EPs should prevent data traffic from and policing the traffic flow. EPs should prevent data traffic from and
to any unauthorized client unless it's PANA traffic. When a client to any unauthorized client unless it's PANA traffic. When a client
is authenticated and authorized, PAA should notify EP(s) and ask for is authenticated and authorized, PAA should notify EP(s) and ask for
Tschofenig (ed.) Expires September 2003 16
PANA March 2003
changing filtering rules to allow traffic for a recently authorized changing filtering rules to allow traffic for a recently authorized
client. There needs to be a protocol between PAA and EP(s) when client. There needs to be a protocol between PAA and EP(s) when
these entities are not co-located. PANA Working Group will not be these entities are not co-located. PANA Working Group will not be
defining a new protocol for this interaction. Instead, it will defining a new protocol for this interaction. Instead, it will
(preferably) identify one of the existing protocols that can fit the (preferably) identify one of the existing protocols that can fit the
requirements. Possible candidates include but not limited to COPS, requirements. Possible candidates include but not limited to COPS,
SNMP, DIAMETER. This task is similar to what MIDCOM Working Group is SNMP, DIAMETER. This task is similar to what MIDCOM Working Group is
trying to achieve, therefore some of the MIDCOM's output might be trying to achieve, therefore some of the MIDCOM's output might be
useful here. useful here.
skipping to change at line 919 skipping to change at page 22, line 49
protection is required but link-layer ciphering capability is not protection is required but link-layer ciphering capability is not
available. Note that a simple shared secret generated by an EAP available. Note that a simple shared secret generated by an EAP
method is not readily usable by IPsec for authentication and method is not readily usable by IPsec for authentication and
encryption of IP packets. Fresh and unique session key derived from encryption of IP packets. Fresh and unique session key derived from
the EAP method is still insufficient to produce an IPsec SA since the EAP method is still insufficient to produce an IPsec SA since
both traffic selectors and other IPsec SA parameters are missing. both traffic selectors and other IPsec SA parameters are missing.
The shared secret can be used in conjunction with a key management The shared secret can be used in conjunction with a key management
protocol like IKE [RFC2409] to turn a simple shared secret into the protocol like IKE [RFC2409] to turn a simple shared secret into the
required IPsec SA. The details of this mechanism is outside the required IPsec SA. The details of this mechanism is outside the
scope of PANA protocol, and it can be outlined in a separate scope of PANA protocol, and it can be outlined in a separate
Tschofenig (ed.) Expires September 2003 17
PANA March 2003
Internet-Draft. PANA provides bootstrapping functionality for such a Internet-Draft. PANA provides bootstrapping functionality for such a
mechanism by carrying EAP methods that can generate initial keying mechanism by carrying EAP methods that can generate initial keying
material. material.
Using network-layer ciphers should be regarded as a substitute for Using network-layer ciphers should be regarded as a substitute for
link-layer ciphers when the latter is not available. IKE involves link-layer ciphers when the latter is not available. IKE involves
several message exchanges which can incur additional delay in several message exchanges which can incur additional delay in
getting basic IP connectivity for a mobile device. Such a latency is getting basic IP connectivity for a mobile device. Such a latency is
inevitable when there is no other alternative and this level of inevitable when there is no other alternative and this level of
protection is required. Network-layer ciphering can also be used in protection is required. Network-layer ciphering can also be used in
addition to link-layer ciphering if the added benefits outweigh its addition to link-layer ciphering if the added benefits outweigh its
cost to the user and the network. cost to the user and the network.
9 Message Formats 9 Message Formats
Bits and bytes on the wire... This section defines message formats for PANA protocol.
10 Open Issues 9.1 PANA Header
The following list describes some open issues for PANA: A summary of the PANA header format is shown below. The fields are
transmitted in network byte order.
- Should the PANA protocol provide downgrade protection? 0 1 2 3
- How extensible or flexible should the device identifier be? 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- Should the PANA protocol support a modify message to be able to +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
alter state? This would, for example, be useful in case of IP | Version | Message Length |
address change without mobility (e.g. in IPv6 for privacy reasons). +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- The PANA SA needs a session key and either this session key is | Flags | Message Type |
derived from the EAP method as part of the EAP key derivation +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
framework or within PANA. | Transmitted Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Received Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVPs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-
11 Security Considerations Version
This Version field MUST be set to 1 to indicate PANA Version 1.
Message Length
The Message Length field is three octets and indicates the
length of the PANA message including the header fields.
Flags
The Flags field is eight bits. The following bits are assigned:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|R r r r F r r r|
+-+-+-+-+-+-+-+-+
R(equest)
- If set, the message is a request. If cleared,
the message is an answer.
F(inish)
- F-flag in the PANA header indicates if this was
the final authentication from sender's
perspective. If PAA enables two separate
authentication, it should not set F-flag in the
PANA-Bind-Request message after the first EAP
method.
r(eserved)
- these flag bits are reserved for future use,
and MUST be set to zero, and ignored by the
receiver.
Message Type
The Message Type field is three octets, and is used in order to
communicate the message type with the message. The 24-bit
address space is managed by IANA [IANAWEB].
Transmitted Sequence Number
The Transmitted Sequence Number field contains the monotonically
increasing 32 bit sequence number that the message sender
increments every time a new packet is sent.
Received Sequence Number
The Received Sequence Number field contains the 32 bit
transmitted sequence number that the peer has last received.
AVPs
AVPs are a method of encapsulating information relevant to the
PANA message. See section 9.2 for more information on AVPs.
9.2 AVP Header
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Flags | AVP Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Id (opt) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+-+-+-+-+
AVP Code
The AVP Code, combined with the Vendor-Id field, identifies the
attribute uniquely. AVP numbers are allocated by IANA [IANAWEB].
AVP Flags
The AVP Flags field is eight bits. The following bits are
assigned:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|V M r r r r r r|
+-+-+-+-+-+-+-+-+
M(andatory)
- The 'M' Bit, known as the Mandatory bit,
indicates whether support of the AVP is
required.
V(endor)
- The 'V' bit, known as the Vendor-Specific bit,
indicates whether the optional Vendor-Id field
is present in the AVP header.
r(eserved)
- these flag bits are reserved for future use,
and MUST be set to zero, and ignored by the
receiver.
AVP Length
The AVP Length field is three octets, and indicates the number
of octets in this AVP including the AVP Code, AVP Length, AVP
Flags, and the AVP data.
Vendor-Id
The Vendor-Id field is present if the 'V' bit is set in the AVP
Flags field. The optional four-octet Vendor-Id field contains
the uniquely assigned id value, encoded in network byte order.
Any vendor wishing to implement a vendor-specific PANA AVP MUST
use their own Vendor-Id along with their privately managed AVP
address space, guaranteeing that they will not collide with any
other vendor's vendor-specific AVP(s), nor with future IETF
applications.
Data
The Data field is zero or more octets and contains information
specific to the Attribute. The format and length of the Data
field is determined by the AVP Code and AVP Length fields.
9.3 PANA Messages
Figure 9lists all PANA messages defined in this document
Message Direction: PaC---PAA
----------------------------------
PANA-PAA-Discover -------->
PANA-Start-Request <--------
PANA-Start-Answer -------->
PANA-Auth-Request <--------
PANA-Auth-Answer -------->
PANA-Bind-Request <--------
PANA-Bind-Answer -------->
PANA-Reauth-Request <------->
PANA-Reauth-Answer <------->
PANA-Termination-Request <------->
PANA-Termination-Answer <------->
PANA-Error <------->
Figure 9: PANA Message Overview
Additionally the EP can also send a PANA-PAA-Discover message to the
PAA.
9.3.1 Message specifications
Every PANA message MUST include a corresponding ABNF
[RFC2234] specification found in [DIAMETER]. Note that PANA
messages have a different header format compared to Diameter.
Example:
message ::= < PANA-Header: <Message type>,
[REQ], [FIN]
* [ AVP ]
9.3.2 PANA-PAA-Discover (PDI)
The PANA-PAA-Discover (PDI) message is used to discover the address
of PAA(s). Both sequence numbers in this message are set to zero
(0). If the EP detects a new PaC and sends the PANA-PAA-Discover to
the PAA, it MUST include the Device-Id of the PaC.
PANA-PAA-Discover ::= < PANA-Header: 1 >
0*1 < Device-Id >
* [ AVP ]
9.3.3 PANA-Start-Request (PSR)
PANA-Start-Request (PSR) is sent by the PAA to the PaC. The PAA sets
the transmission sequence number to an initial random value. The
received sequence number is set to zero (0).
PANA-Start-Request ::= < PANA-Header: 2, REQ >
[ Cookie ]
* [ AVP ]
9.3.4 PANA-Start-Answer (PSA)
PANA-Start-Answer (PSA) is sent by the PaC to the PAA in response to
a PANA-Start-Request message. The PANA_start message transmission
sequence number field is copied to the received sequence number
field. The
transmission sequence number is set to initial random value.
PANA-Start-Answer ::= < PANA-Header: 3 >
[ Cookie ]
* [ AVP ]
9.3.5 PANA-Auth-Request (PAR)
PANA-Auth-Request (PAR) is sent by the PAA to the PaC.
PANA-Auth-Request ::= < PANA-Header: 4, REQ >
< Session-Id >
< EAP-Payload >
* [ AVP ]
0*1 < MAC >
9.3.6 PANA-Auth-Answer (PAN)
PANA-Auth-Answer (PAN) is sent by the PaC to the PAA in response to
a PANA-Auth-Request message.
PANA-Auth-Answer ::= < PANA-Header: 5 >
< Session-Id >
< EAP-Payload >
* [ AVP ]
0*1 < MAC >
9.3.7 PANA-Bind-Request (PBR)
PANA-Bind-Request (PBR) is sent by the PAA to the PaC.
PANA-Bind-Request ::= < PANA-Header: 6, REQ, [FIN] >
< Session-Id >
< Device-Id >
{ EAP-Payload }
{ Result-Code }
[ Protection-Capability ]
* [ AVP ]
0*1 < MAC >
9.3.8 PANA-Bind-Answer (PBA)
PANA-Bind-Answer (PBA) is sent by the PaC to the PAA in response to
a PANA-Result-Request message.
PANA-Bind-Answer ::= < PANA-Header: 7, [FIN] >
< Session-Id >
< Device-Id >
* [ AVP ]
0*1 < MAC >
9.3.9 PANA-Reauth-Request (PRAR)
PANA-Reauth-Request (PRAR) is either sent by the PaC or the PAA.
PANA-Reauth-Request ::= < PANA-Header: 8, REQ >
< Session-Id >
< Device-Id >
* [ AVP ]
0*1 < MAC >
9.3.10 PANA-Reauth-Answer (PRAA)
PANA-Reauth-Answer (PRAA) is sent in response to a
PANA-Reauth-Request.
PANA-Reauth-Answer ::= < PANA-Header: 9 >
< Session-Id >
< Device-Id >
* [ AVP ]
0*1 < MAC >
9.3.11 PANA-Termination-Request (PTR)
PANA-Termination-Request (PTR) is sent either by the PaC or the PAA.
PANA-Termination-Request ::= < PANA-Header: 10, REQ >
< Session-Id >
< Termination-Cause >
* [ AVP ]
0*1 < MAC >
9.3.12 PANA-Termination-Answer (PTA)
PANA-Termination-Answer (PTA) is sent either by the PaC or the PAA
in response to PANA-Termination-Request.
PANA-Termination-Answer ::= < PANA-Header: 11 >
< Session-Id >
* [ AVP ]
0*1 < MAC >
9.3.13 PANA-Error
PANA-Error is sent either by the PaC or the PAA.
TBD
9.4 AVPs in PANA
Some of the used AVPs are defined in this document and some of them
are defined in other documents like [DIAMETER]. PANA proposes to
use the same name space with the Diameter spec. For temporary
allocation, PANA uses AVP type numbers starting from 1024.
9.4.1 MAC AVP
The first octet (8 bits) of the MAC (Code 1024) AVP data contains
the MAC algorithm type. Rest of the AVP data payload contains the
MAC encoded in network byte order. The Algorithm 8 bit name space
is managed by IANA [IANAWEB]. The AVP length varies depending on
the used algorithm.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm | MAC...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Algorithm
1 HMAC-MD5 (16 bytes)
2 HMAC-SHA1 (20 bytes)
MAC
The Message Authentication Code is encoded in network byte
order.
9.4.2 Device-Id AVP
The first octet (8 bits) of the Device-Id (Code 1025) AVP data
contains the device type. Rest of the AVP data payload contains
the device data. The content and format of data (including byte
and bit ordering) is expected to be specified in specific
documents. For instance, [IPv6-ETHER].
UNKNOWN 0
IPV4_ADDRESS 1
IPV6_ADDRESS 2
L2_ADDRESS 3
For type 1 (IPv4 address), data size is 32 bits and for type 2
(IPv6 address), data size is 128 bits.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Data... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
9.4.3 Session-Id AVP
Session-Id AVP (Code 1026) has an opaque data field, which is
assigned by the PAA. All messages pertaining to a specific PANA
Session MUST include only one Session-Id AVP and the same value
MUST be used throughout the lifetime of a session. When present,
the Session-Id SHOULD appear immediately following the PANA header.
The Session-Id MUST be globally and eternally unique, as it is
meant to identify a PANA Session without reference to any
other information, and may be needed to correlate historical
authentication information with accounting information.
The Session-Id AVP MAY use Diameter [DIAMETER] message
formatting. In this case the AVP code is 263.
9.4.4 Cookie AVP
The Cookie AVP (Code 1027) is of type OctetString. The data is
opaque and the exact content is outside the scope of this protocol.
9.4.5 Protection-Capability AVP
The Protection-Capability AVP (Code 1028) is of type Unsigned32.
The AVP data is used as a collection of flags for different data
protection capability indications. Below is a list of specified
data protection capabilities:
0 UNKNOWN
1 L2_PROTECTION
2 IPSEC_PROTECTION
9.4.6 Termination-Cause AVP
The Termination-Cause AVP is defined in [DIAMETER].
LOGOUT 1 (PaC -> PAA)
The user initiated a disconnect
(SERVICE_NOT_PROVIDED 2 (PAA -> PaC))
This value is used when the user disconnected
prior to the receipt of the authorization answer
message.
BAD_ANSWER 3 (PaC -> PAA)
This value indicates that the authorization answer
received by the access device was not processed
successfully.
ADMINISTRATIVE 4 (PAA -> Pac)
The user was not granted access, or was
disconnected, due to administrative reasons,
such as the receipt of a Abort-Session-Request
message.
(LINK_BROKEN 5)
The communication to the user was abruptly
disconnected.
AUTH_EXPIRED 6 (PAA -> PaC)
The user's access was terminated since its
authorized session time has expired.
(USER_MOVED 7) (PaC -> PAA)
The user is receiving services from another
access device. (See issue16).
SESSION_TIMEOUT 8 (PAA -> PaC)
The user's session has timed out, and service
has been terminated.
9.4.7 Result-Code AVP
The Result-Code AVP is defined in [DIAMETER].
SUCCESS 2001
COMMAND_UNSUPPORTED 3001
UNABLE_TO_DELIVER 3002
REALM_NOT_SERVED 3003
TOO_BUSY 3004
INVALID_HDR_BITS 3008
INVALID_AVP_BITS 3009
AUTHENTICATION_REJECTED 4001
AVP_UNSUPPORTED 5001
UNKNOWN_SESSION_ID 5002
AUTHORIZATION_REJECTED 5003
INVALID_AVP_VALUE 5004
MISSING_AVP 5005
RESOURCES_EXCEEDED 5006
AVP_OCCURS_TOO_MANY_TIMES 5009
UNSUPPORTED_VERSION 5011
INVALID_AVP_LENGTH 5014
INVALID_MESSAGE_LENGTH 5015
9.4.8 EAP-Payload AVP
The EAP-Payload AVP is defined in [DIAMETER-EAP].
9.5 AVP Occurrence Table
The following tables lists the AVPs used in this document, and
specifies in which PANA messages they MAY, or MAY NOT be present.
The table uses the following symbols:
0 The AVP MUST NOT be present in the message.
0+ Zero or more instances of the AVP MAY be present in the
message.
0-1 Zero or one instance of the AVP MAY be present in the
message. It is considered an error if there are more than
one instance of the AVP.
1 One instance of the AVP MUST be present in the message.
1+ At least one instance of the AVP MUST be present in the
message.
+-----------------------------------------+
| Message |
| Type |
+-----+-----+-----+-----+-----+-----+-----+
Attribute Name | PSR | PSA | PAR | PAN | PBR | PBA | PDI |
--------------------+-----+-----+-----+-----+-----+-----+-----+
Result-Code | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
Session-Id | 0 | 0 | 1 | 1 | 1 | 1 | 0 |
Termination-Cause | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
EAP-Payload | 0 | 0 | 1 | 1 | 1 | 0 | 0 |
MAC | 0 | 0 | 0-1 | 0-1 | 0-1 | 0-1 | 0 |
Device-Id | 0 | 0 | 0 | 0 | 1+ | 1+ | 0-1 |
Cookie | 0-1 | 0-1 | 0 | 0 | 0 | 0 | 0 |
Protection-Cap. | 0 | 0 | 0 | 0 | 0-1 | 0 | 0 |
--------------------+-----+-----+-----+-----+-----+-----+-----+
+-------------------------+
| Message |
| Type |
+------+------+-----+-----+
Attribute Name | PRAR | PRAA | PTR | PTA |
--------------------+------+------+-----+-----+
Result-Code | 0 | 0 | 0 | 0 |
Session-Id | 1 | 1 | 1 | 1 |
Termination-Cause | 0 | 0 | 1 | 0 |
EAP-Payload | 0-1 | 0-1 | 0 | 0 |
MAC | 0-1 | 0-1 | 0-1 | 0-1 |
Device-Id | 1+ | 1+ | 0 | 0 |
Cookie | 0 | 0 | 0 | 0 |
Protection-Cap. | 0 | 0 | 0 | 0 |
--------------------+------+------+-----+-----+
Figure 10: AVP Occurrence Table
10 Security Considerations
The PANA protocol provides ordered delivery for EAP messages. If an The PANA protocol provides ordered delivery for EAP messages. If an
EAP method that provides session keys is used, a PANA SA is created. EAP method that provides session keys is used, a PANA SA is created.
The EAP Success/Failure message is one of the signaling messages The EAP Success/Failure message is one of the signaling messages
which is integrity protected with this PANA SA. The PANA protocol which is integrity protected with this PANA SA. The PANA protocol
does not provide security protection for the initial EAP message does not provide security protection for the initial EAP message
exchange. Integrity protection can only be provided after the PANA exchange. Integrity protection can only be provided after the PANA
SA has been established. Thus, PANA re-authentication, revocation SA has been established. Thus, PANA re-authentication, revocation
and disconnect notifications can be authenticated, integrity and and disconnect notifications can be authenticated, integrity and
replay protected. In certain environments (e.g. on a shared link) replay protected. In certain environments (e.g. on a shared link)
the EAP method selection is an important issue. the EAP method selection is an important issue.
skipping to change at line 978 skipping to change at page 34, line 27
the PaC and the PAA (typically referred as the PANA protocol). the PaC and the PAA (typically referred as the PANA protocol).
The PANA itself consists of a sequence of steps which are executed The PANA itself consists of a sequence of steps which are executed
to complete the network access authentication procedure. Some of to complete the network access authentication procedure. Some of
these steps are optional. these steps are optional.
The following execution steps have been identified as being relevant The following execution steps have been identified as being relevant
for PANA. They security considerations will be discussed in detail for PANA. They security considerations will be discussed in detail
subsequently. subsequently.
Tschofenig (ed.) Expires September 2003 18
PANA March 2003
a) Discovery message exchange a) Discovery message exchange
In general it is difficult to prevent a vulnerabilities of the In general it is difficult to prevent a vulnerabilities of the
discovery protocol since the initial discovery are unsecured. To discovery protocol since the initial discovery are unsecured. To
prevent very basic attacks an adversary should not be able to cause prevent very basic attacks an adversary should not be able to cause
state creation with discovery messages at the PAA. This is prevented state creation with discovery messages at the PAA. This is prevented
by re-using a cookie concept (see [RFC2522]) which allows the by re-using a cookie concept (see [RFC2522]) which allows the
responder to be stateless in the first message exchange. Because of responder to be stateless in the first message exchange. Because of
the architectural assumptions made in PANA (i.e. the PAA is the on the architectural assumptions made in PANA (i.e. the PAA is the on
the same link as the PaC) the return-routability concept does not the same link as the PaC) the return-routability concept does not
provide additional protection. Hence it is difficult to prevent this provide additional protection. Hence it is difficult to prevent this
threat entirely. Furthermore it is not possible to shift heavy threat entirely. Furthermore it is not possible to shift heavy
cryptographic operations to the PaC at the first few messages since cryptographic operations to the PaC at the first few messages since
the computational effort depends on the EAP method. The usage of the computational effort depends on the EAP method. The usage of
client-puzzles as introduced by P. Nikander et. al. in [AN+00] is client-puzzles as introduced by [JB99] is under investigation.
under investigation.
Resistance against blind DoS attacks (i.e. attacks by off-path Resistance against blind DoS attacks (i.e. attacks by off-path
adversaries) is achieved with sequence numbers and cookies. adversaries) is achieved with sequence numbers and cookies.
Since PAA and PaC are one IP hop away from each other, PANA messages Since PAA and PaC are one IP hop away from each other, PANA messages
can be filtered whenever messages arrive at interfaces where they can be filtered whenever messages arrive at interfaces where they
are not expected. are not expected.
b) EAP over PANA message exchange b) EAP over PANA message exchange
The EAP derived session key is used to create a PANA security The EAP derived session key is used to create a PANA security
association. Since the execution of an EAP method might require a association. Since the execution of an EAP method might require a
large number of roundtrips and no other session key is available it large number of roundtrips and no other session key is available it
is not possible to secure the EAP message exchange itself. Hence an is not possible to secure the EAP message exchange itself. Hence an
adversary can both eavesdrop the EAP messages and is also able to adversary can both eavesdrop the EAP messages and is also able to
inject arbitrary messages which might confuse both the PaC and the inject arbitrary messages which might confuse both the PaC and the
PAA. The threats caused by this ability heavily depend on the EAP PAA. The threats caused by this ability heavily depend on the EAP
state machine. Since especially the PAA is not allowed to discard state machine. Since especially the PAA is not allowed to discard
packets and packets have to be stored or forwarded to an AAA packets and packets have to be stored or forwarded to an AAA
infrastructure some risk of DoS attacks exists. infrastructure some risk of DoS attacks exists.
skipping to change at line 1032 skipping to change at page 35, line 29
allows the adversary to learn the identity of the PaC. In such a allows the adversary to learn the identity of the PaC. In such a
case a privacy problem is prevalent. case a privacy problem is prevalent.
To prevent these threats Section 6 suggests using proper EAP methods To prevent these threats Section 6 suggests using proper EAP methods
for particular environments. Depending on the usage environment an for particular environments. Depending on the usage environment an
EAP authentication has to be used for example which supports user EAP authentication has to be used for example which supports user
identity confidentiality, protection against dictionary attacks and identity confidentiality, protection against dictionary attacks and
session key establishment. It is therefore the responsibility of the session key establishment. It is therefore the responsibility of the
network operators and end users to choose the proper EAP method. network operators and end users to choose the proper EAP method.
Tschofenig (ed.) Expires September 2003 19
PANA March 2003
PANA does not protect the EAP method exchange, but provides ordered PANA does not protect the EAP method exchange, but provides ordered
delivery with sequence numbers. Sequence numbers and cookies delivery with sequence numbers. Sequence numbers and cookies
provide resistance against blind DoS attacks. provide resistance against blind DoS attacks.
c) PANA SA establishment c) PANA SA establishment
Once the EAP message authentication is finished a fresh and unique Once the EAP message authentication is finished a fresh and unique
session key is available to the PaC and the PAA. This assumes that session key is available to the PaC and the PAA. This assumes that
the EAP method allows session key derivation and that the generated the EAP method allows session key derivation and that the generated
session key has a good quality. For further discussion about the session key has a good quality. For further discussion about the
skipping to change at line 1089 skipping to change at page 36, line 34
If an entity (PAA or PaC) looses its state (especially the current If an entity (PAA or PaC) looses its state (especially the current
sequence number) then the entire PANA protocol has to be restarted. sequence number) then the entire PANA protocol has to be restarted.
No re-synchronization procedure is provided. No re-synchronization procedure is provided.
The lifetime of the PANA SA has to be bound to the refresh interval The lifetime of the PANA SA has to be bound to the refresh interval
with an additional tolerance period. To provide fast re- with an additional tolerance period. To provide fast re-
authentication a separate security association (e.g. one stored at authentication a separate security association (e.g. one stored at
the local AAA server) should be used. By fast re-authentication we the local AAA server) should be used. By fast re-authentication we
mean a new PANA protocol execution which does not involve the entire mean a new PANA protocol execution which does not involve the entire
AAA communication. The ability to trigger such a protocol execution AAA communication. The ability to trigger such a protocol execution
Tschofenig (ed.) Expires September 2003 20
PANA March 2003
depends on the given EAP method and on the policy of the local depends on the given EAP method and on the policy of the local
network requesting authentication. network requesting authentication.
d) Enabling weak legacy authentication methods in insecure networks d) Enabling weak legacy authentication methods in insecure networks
Some of the authentication methods are not strong enough to be used Some of the authentication methods are not strong enough to be used
in insecure networks where attackers can easily eavesdrop and spoof in insecure networks where attackers can easily eavesdrop and spoof
on the link. They may not be able to produce much needed keying on the link. They may not be able to produce much needed keying
material either. An example would be using EAP-MD5 over wireless material either. An example would be using EAP-MD5 over wireless
links. Use of such legacy methods can be enabled by carrying them links. Use of such legacy methods can be enabled by carrying them
over a secure channel. There are EAP methods which are specifically over a secure channel. There are EAP methods which are specifically
designed for this purpose, such as EAP-TTLS [TTLS] and PEAP [PEAP]. designed for this purpose, such as EAP-TTLS [TTLS],PEAP [PEAP] or
PANA can carry these EAP tunneling methods which can carry the EAP-IKEv2 [EAP-IKEv2]. PANA can carry these EAP tunneling methods
legacy methods. PANA does not do anything special for this case. The which can carry the legacy methods. PANA does not do anything
EAP tunneling method will have to produce keying material for PANA special for this case. The EAP tunneling method will have to produce
SA when needed. There are certain MitM vulnerabilities with keying material for PANA SA when needed. There are certain MitM
tunneling EAP methods [MITM]. Solving these problems are outside vulnerabilities with tunneling EAP methods [MITM]. Solving these
the scope of PANA. problems is outside the scope of PANA. The compound authentication
problem described in [PL+03] is likely to be solved in EAP itself
rather than in PANA.
e) Preventing downgrading attacks e) Preventing downgrading attacks
EAP supports a number of different EAP methods for authentication EAP supports a number of different EAP methods for authentication
and therefore it might be required to agree on a specific mechanism. and therefore it might be required to agree on a specific mechanism.
An unprotected negotiation mechanism is supported in EAP and a An unprotected negotiation mechanism is supported in EAP and a
secure negotiation procedure for the GSS-API methods. The support of secure negotiation procedure for the GSS-API methods. The support of
the GSS-API as an EAP method is described in [AS02]. A protected the GSS-API as an EAP method is described in [AS02]. A protected
negotiation is supported by the GSS-API with RFC 2478 [RFC2478]. If negotiation is supported by the GSS-API with RFC 2478 [RFC2478]. If
desired, such a protection can also be offered by PANA by repeating desired, such a protection can also be offered by PANA by repeating
the list of supported EAP methods protected with the PANA SA. This the list of supported EAP methods protected with the PANA SA. This
type of protection is similar to the protected negotiation described type of protection is similar to the protected negotiation described
in [RFC3329]. in [RFC3329].
This issue requires further investigation especially since the EAP This issue requires further investigation especially since the EAP
protocol runs in most cases different endpoints than the PANA protocol is executed between different endpoints than the PANA
protocol. protocol.
f) Device Identifier exchange f) Device Identifier exchange
As part of the authorization procedure a Device Identifier has to be As part of the authorization procedure a Device Identifier has to be
installed at the EP by the PAA. The PaC provides the Device installed at the EP by the PAA. The PaC provides the Device
Identifier information to the PAA secured with the PANA SA. Section Identifier information to the PAA secured with the PANA SA. Section
6.2.4 of [THREATS] describes a threat where an adversary modifies 6.2.4 of [THREATS] describes a threat where an adversary modifies
the Device Identifier to gain unauthorized access to the network. the Device Identifier to gain unauthorized access to the network.
The installation of the Device Identifier at the EP (independently The installation of the Device Identifier at the EP (independently
whether the EP is co-located with the PAA or not) has to be whether the EP is co-located with the PAA or not) has to be
accomplished in a secure manner. These threats are, however, not accomplished in a secure manner. These threats are, however, not
part of the PANA protocol itself since the protocol is not PANA part of the PANA protocol itself since the protocol is not PANA
specific. specific.
g) Triggering a data protection protocol g) Triggering a data protection protocol
Recent activities in the EAP working group try to create a common Recent activities in the EAP working group try to create a common
framework for key derivation which is described in [Ab02]. This framework for key derivation which is described in [Ab02]. This
Tschofenig (ed.) Expires September 2003 21
PANA March 2003
framework is also relevant for PANA in various ways. First, a PANA framework is also relevant for PANA in various ways. First, a PANA
security association needs to be created. Additionally it might be security association needs to be created. Additionally it might be
necessary to trigger a protocol which allows link layer and network necessary to trigger a protocol which allows link layer and network
layer data protection to be established. As an example see Section 1 layer data protection to be established. As an example see Section 1
of [Ab02] with [802.11i] and [802.11] as an example. Furthermore, a of [Ab02] with [802.11i] and [802.11] as an example. Furthermore, a
derived session key might help to create the pre-requisites for derived session key might help to create the pre-requisites for
network layer protection (for example IPsec). network layer protection (for example IPsec).
As motivated in Section 6.4 of [THREATS] it might be necessary to As motivated in Section 6.4 of [THREATS] it might be necessary to
establish either a link layer or a network layer protection to establish either a link layer or a network layer protection to
skipping to change at line 1192 skipping to change at page 38, line 34
An additional motivation for detecting a disconnected end host is An additional motivation for detecting a disconnected end host is
the ability to release resources (i.e. garbage collection). The PAA the ability to release resources (i.e. garbage collection). The PAA
can remove per-session state information including installed can remove per-session state information including installed
security association, packet filters etc. security association, packet filters etc.
Different procedures can be used for disconnect indication. PANA Different procedures can be used for disconnect indication. PANA
cannot assume link layer disconnect indication. Hence this cannot assume link layer disconnect indication. Hence this
functionality has to be provided at a higher layer. With this functionality has to be provided at a higher layer. With this
version of the draft we suggest to apply the soft-state principle version of the draft we suggest to apply the soft-state principle
found at other protocols (such as RSVP [RFC2205]). Soft-state means found at other protocols (such as RSVP). Soft-state means that
that session state is kept alive as long as refresh messages refresh session state is kept alive as long as refresh messages refresh the
the state. If no new refresh messages are provided then the state state. If no new refresh messages are provided then the state
automatically times out and resources are released. This process automatically times out and resources are released. This process
includes stopping accounting procedures. includes stopping accounting procedures.
Based on the different environments where PANA could be used it is Based on the different environments where PANA could be used it is
difficult to fix a refresh interval. Hence a default refresh difficult to fix a refresh interval. Hence a default refresh
interval of 30 seconds is suggested. Additionally there is the interval of 30 seconds is suggested. Additionally there is the
possibility to negotiation this interval once the PANA security possibility to negotiation this interval once the PANA security
association is established. A policy at the PAA and the PaC would association is established. A policy at the PAA and the PaC would
ensure that the refresh interval is selected with a value which is ensure that the refresh interval is selected with a value which is
either too high or too low. There is certainly a tradeoff between either too high or too low. There is certainly a tradeoff between
Tschofenig (ed.) Expires September 2003 22
PANA March 2003
the refresh interval and the bandwidth consumption. To reduce the the refresh interval and the bandwidth consumption. To reduce the
bandwidth consumption a small PANA message consisting only of a bandwidth consumption a small PANA message consisting only of a
session identifier and the Integrity object is used. The session session identifier and the Integrity object is used. The session
identifier refers to the state that has to be refreshed. Some identifier refers to the state that has to be refreshed. Some
environments do not need PANA refresh messages to detect orphan environments do not need PANA refresh messages to detect orphan
states. For these environments the refresh interval should be set to states. For these environments the refresh interval should be set to
zero which effectively disables the usage of refresh messages. In zero which effectively disables the usage of refresh messages. In
case of IPsec protection a dead-peer mechanism can be used to detect case of IPsec protection a dead-peer mechanism can be used to detect
inactivity (see [HBR03]). inactivity (see [HBR03]).
skipping to change at line 1237 skipping to change at page 39, line 26
The PANA protocol supports the ability for both the PaC and the PAA The PANA protocol supports the ability for both the PaC and the PAA
to transmit a tear-down message. This message causes state removal, to transmit a tear-down message. This message causes state removal,
a stop of the accounting procedure and removes the installed packet a stop of the accounting procedure and removes the installed packet
filters. filters.
It is obvious that such a message must be protected to prevent an It is obvious that such a message must be protected to prevent an
adversary from deleting state information and thereby causing denial adversary from deleting state information and thereby causing denial
of service attacks. of service attacks.
12 References 11 Open Issues
A list of open issues is maintained at
http://danforsberg.info:8080/pana-issues/.
12 Acknowledgments
We would like to thank all members of the PANA working group for
their comments to this document.
13 References
[802.11] I. S. 802.11-1997, "Information technology - [802.11] I. S. 802.11-1997, "Information technology -
telecommunications and information exchange between systems - local telecommunications and information exchange between systems - local
and metropolitan area networks - specific requirements part 11: and metropolitan area networks - specific requirements part 11:
Wireless lan medium access control (mac) and physical layer (phy) Wireless lan medium access control (mac) and physical layer (phy)
specifications," tech. rep., 1997. specifications," tech. rep., 1997.
[RFC2522] P. Karn and W. Simpson, "Photuris: Session-key management [RFC2522] P. Karn and W. Simpson, "Photuris: Session-key management
protocol," RFC 2522, Internet Engineering Task Force, Mar. 1999. protocol," RFC 2522, March 1999.
[PEAP] H. Andersson, S. Josefsson, G. Zorn, et al. , "Protected
extensible authentication protocol (PEAP)," Internet Draft, Internet
Engineering Task Force, Feb. 2002. Work in progress.
[Ab02] B. Aboba, "The EAP session key problem," Internet Draft, [Ab02] B. Aboba and D. Simon: "EAP Keying Framework", Internet
Internet Engineering Task Force, Feb. 2002. Work in progress. Draft, Internet Engineering Task Force, March, 2003, Work in
progress.
[802.11i] I. D. 802.11i/D2, "Draft supplement to standard for [802.11i] I. D. 802.11i/D2, "Draft supplement to standard for
telecommunications and information exchange between systems - telecommunications and information exchange between systems -
lan/man specific requirements - part 11: Wireless medium access lan/man specific requirements - part 11: Wireless medium access
control (mac) and physical layer (phy) specifications: Specification control (mac) and physical layer (phy) specifications: Specification
for enhanced security," tech. rep., 2001. for enhanced security," tech. rep., 2001.
[AS02] Aboba, B., Simon, D.: "EAP GSS Authentication Protocol", [AS02] Aboba, B., Simon, D.: "EAP GSS Authentication Protocol",
<draft-aboba-pppext-eapgss-12.txt>, (work in progress), April, 2002. Internet Draft, Internet Engineering Task Force, April, 2002, Work
in progress.
Tschofenig (ed.) Expires September 2003 23
PANA March 2003
[CFB02] P. Calhoun, S. Farrell, and W. Bulley, "Diameter CMS [CFB02] P. Calhoun, S. Farrell, and W. Bulley: "Diameter CMS
security application," Internet Draft, Internet Engineering Task Security Application," Internet Draft, Internet Engineering Task
Force, Mar. 2002. Work in progress. Force, Mar. 2002, Work in progress.
[RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible [RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible
Authentication Protocol (EAP)", RFC 2284, March 1998. Authentication Protocol (EAP)", RFC 2284, March 1998.
[RFC2716] Aboba, B., and D. Simon, "PPP EAP TLS Authentication
Protocol", RFC 2716, October 1999.
[HBR03] G. Huang, S. Beaulieu, and D. Rochefort, "A traffic-based [HBR03] G. Huang, S. Beaulieu, and D. Rochefort, "A traffic-based
method of detecting dead ike peers," internet draft, Internet method of detecting dead ike peers", Internet Draft, Internet
Engineering Task Force, 2003. Work in progress. Engineering Task Force, 2003, Work in progress.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998. (IKE)", RFC 2409, November 1998.
[IKEv2] Kaufman, C.: "Internet Key Exchange (IKEv2) Protocol", [MITM] N. Asokan, V. Niemi, and K. Nyberg: "Man-in-the-middle in
<draft-ietf-ipsec-ikev2-05.txt>, (work in progress), February, 2003. tunnelled authentication", In the Proceedings of the 11th
International Workshop on Security Protocols, Cambridge, UK, April
[MITM] N. Asokan, V. Niemi, and K. Nyberg, "Man-in-the-middle in 2003. To be published in the Springer-Verlag LNCS series.
tunneled authentication," in http://eprint.iacr.org/2002/163/ ,
2002.
[PANATLS] Y. Ohba, S. Baba, and S. Das, "Pana over tls," Internet
Draft, Internet Engineering Task Force, 2002. Work in progress.
[PEAP] H. Andersson, S. Josefsson, G. Zorn, et al. , "Protected
[PIC] Y. Sheffer, H. Krawczyk, and B. Aboba, "PIC, a pre-IKE [PEAP] A. Palekar, D. Simon, G. Zorn and S. Josefsson: "Protected
credential provisioning protocol," Internet Draft, Internet EAP Protocol (PEAP)", Internet Draft, Internet Engineering Task
Engineering Task Force, Feb. 2002. Work in progress. Force, March 2003, Work in progress.
[PL+03] J. Puthenkulam, V. Lortz, A. Palekar, D. Simon, and B. [PL+03] J. Puthenkulam, V. Lortz, A. Palekar, D. Simon, and B.
Aboba, "The compound authentication binding problem," internet Aboba, "The compound authentication binding problem," internet
draft, Internet Engineering Task Force, 2003. Work in progress. draft, Internet Engineering Task Force, 2003. Work in progress.
[AN+00] Aura, T., Nikander, P., Leiwo, J.: "DOS-resistant [PY+02] R. Penno, A. Yegin, Y. Ohba, G. Tsirtsis, and C. Wang:
Authentication with Client Puzzles", in "Proc. Security Protocols
Workshop 2000, Cambridge, UK", 2000.
[PY+02] Penno, R., Yegin, A., Ohba, Y., Tsirtsis, G., Wang, C.:
"Protocol for Carrying Authentication for Network Access (PANA) "Protocol for Carrying Authentication for Network Access (PANA)
Requirements and Terminology", Internet-Draft, <draft-ietf-pana- Requirements and Terminology", Internet Draft, Internet Engineering
requirements-04.txt>, (work in progress), October, 2002. Task Force, June 2003, Work in progress.
[RFC2284bis] Blunk, L., Vollbrecht, J., Aboba, B., Carlson, J.: [RFC2284bis] L. Blunk, J. Vollbrecht, B. Aboba, J. Carlson:
"Extensible Authentication Protocol (EAP)", < <draft-ietf-eap- "Extensible Authentication Protocol (EAP)", Internet Draft, Internet
rfc2284bis-01.txt>, (work in progress), January, 2003. Engineering Task Force, January 2003, Work in progress.
[RFC1982] Elz, R., Bush, R.: "Serial Number Arithmetic", RFC 1982, [RFC1982] Elz, R., Bush, R.: "Serial Number Arithmetic", RFC 1982,
August 1996. August 1996.
Tschofenig (ed.) Expires September 2003 24
PANA March 2003
[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S., Jamin, S.:
âResource ReSerVation Protocol (RSVP) ¤ Version 1 Functional
Specification", RFC 2205, September 1997.
[RFC2478] E. Baize and D. Pinkas, "The simple and protected GSS-API [RFC2478] E. Baize and D. Pinkas, "The simple and protected GSS-API
negotiation mechanism," RFC 2478, Internet Engineering Task Force, negotiation mechanism," RFC 2478, Internet Engineering Task Force,
Dec. 1998. Dec. 1998.
[RFC2988] Paxson, V., Allman, M.: "Computing TCP's Retransmission [RFC2988] V. Paxson, and M. Allman: "Computing TCP's Retransmission
Timer", RFC 2988, November, 2000. Timer", RFC 2988, November, 2000.
[RFC3329] Arkko, J., Torvinen, V., Camarillo, G., Niemi, A., Haukka, [RFC3329] J. Arkko, V. Torvinen, G. Camarillo, A. Niemi, and T.
T.: "Security Mechanism Agreement for the Session Initiation Haukka: "Security Mechanism Agreement for the Session Initiation
Protocol (SIP)", RFC 3329, January, 2003. Protocol (SIP)", RFC 3329, January, 2003.
[SENAA] D. Forsberg and J. Rajahalme, "Secure network access [THREATS] M. Parthasarathy: "PANA Threat Analysis and security
authentication (senaa)," Internet Draft, Internet Engineering Task requirements", Internet Draft, Internet Engineering Task Force, May
Force, 2002. Work in progress. 2003, Work in progress.
[THREATS] Parthasarathy, M.: "PANA Threat Analysis and security
requirements", <draft-ietf-pana-threats-01.txt>, (work in progress),
January, 2003.
[TTLS] P. Funk and S. Blake-Wilson, "EAP tunneled TLS authentication [TTLS] P. Funk and S. Blake-Wilson: "EAP tunneled TLS authentication
protocol (EAP-TTLS)," Internet Draft, Internet Engineering Task protocol (EAP-TTLS)," Internet Draft, Internet Engineering Task
Force, Mar. 2002. Work in progress. Force, November 2002. Work in progress.
[USAGE] Ohba, Y., Das, S., Patil, B., Soliman, H., Yegin, A.: [USAGE] Y. Ohba, S. Das, B. Patil, H. Soliman, A. Yegin, A.:
"Problem Statement and Usage Scenarios for PANA", <draft-ietf-pana- "Problem Statement and Usage Scenarios for PANA", Internet Draft,
usage-scenarios-04.txt>, (work in progress), February, 2003. Internet Engineering Task Force, April 2003, Work in progress.
[WHC02] J. Walker, R. Housley, and N. Cam-Winget, "AAA key [EAP-IKEv2] H. Tschofenig and D. Kroeselberg: "EAP IKEv2 Method
(EAP-IKEv2)", Internet Draft, Internet Engineering Task Force, June
2003, Work in progress.
[WHC02] J. Walker, R. Housley, and N. Cam-Winget: "AAA key
distribution," Internet Draft, Internet Engineering Task Force, Apr. distribution," Internet Draft, Internet Engineering Task Force, Apr.
2002. Work in progress. 2002, Expired.
13 Acknowledgments [DIAMETER-EAP] T. Hiller and G. Zorn: "Diameter Extensible
Authentication Protocol (EAP) Application", Internet Draft, Internet
Engineering Task Force, March 2003, Work in progress.
Place your name here [DIAMETER] P. Calhoun, J. Loughney, E. Guttman, G. Zorn and J.
Arkko: "Diameter Base Protocol", Internet Draft, Internet
Engineering Task Force, December 2002, Work in progress.
14 Author's Addresses [IANAWEB] IANA, "Number assignment", http://www.iana.org
[CTP] J. Loughney, M. Nakhjiri, C. Perkins and R. Koodli:
"Context Transfer Protocol", Internet Draft, Internet Engineering
Task Force, June 2003, Work in progress.
[JB99] A. Juels and J. Brainard: "Client Puzzles: A Cryptographic
Defense Against Connection Depletion Attacks", In S. Kent, editor,
Proceedings of NDSS '99 (Networks and Distributed Security
Systems), pages 151-165, 1999.
Change History
Changes from PANA-00 to PANA-01 June 2003
- The names for the PANA messages have been changed. Hence it was
necessary to reflect the new terminology in other parts of the
draft.
- New text has been added to the following sections:
* Terminology
* PANA Security Association
* Message Authentication Code
* Refresh Interval Negotiation
* Mobility Handling
* Event Notification
* Message Formats
- The details on message formats add more details to several parts
of the draft. The AVP format is based on Diameter/
- The open issue list has been replaced by a reference to the web
page containing the open issues.
Author's Addresses
Basavaraj Patil Basavaraj Patil
Nokia Nokia
6000 Connection Dr. 6000 Connection Dr.
Irving, TX. 75039 Irving, TX. 75039
USA USA
Phone: +1 972-894-6709 Phone: +1 972-894-6709
Email: Basavaraj.Patil@nokia.com Email: Basavaraj.Patil@nokia.com
Dan Forsberg Dan Forsberg
Nokia Research Center Nokia Research Center
P.O. Box 407 P.O. Box 407
FIN-00045 NOKIA GROUP, Finland FIN-00045 NOKIA GROUP, Finland
Tschofenig (ed.) Expires September 2003 25
PANA March 2003
Phone: +358 50 4839470 Phone: +358 50 4839470
EMail: dan.forsberg@nokia.com EMail: dan.forsberg@nokia.com
Alper E. Yegin Alper E. Yegin
DoCoMo USA Labs DoCoMo USA Labs
181 Metro Drive, Suite 300 181 Metro Drive, Suite 300
San Jose, CA, 95110 San Jose, CA, 95110
USA USA
Phone: +1 408 451 4743 Phone: +1 408 451 4743
Email: alper@docomolabs-usa.com Email: alper@docomolabs-usa.com
skipping to change at line 1432 skipping to change at page 43, line 47
+-|--> (got resp 1) +-|--> (got resp 1)
4. (got req 2) <----|-- Request ID=2 4. (got req 2) <----|-- Request ID=2
| |
5. Response ID=2 -----|--> (got resp 2) 5. Response ID=2 -----|--> (got resp 2)
| |
6. (got req 1) <----+ 6. (got req 1) <----+
7. Response ID=1 --------> [discarded due to unexpected ID] 7. Response ID=1 --------> [discarded due to unexpected ID]
Figure A.1 Undesirable scenario Figure A.1 Undesirable scenario
Tschofenig (ed.) Expires September 2003 26
PANA March 2003
In Figure A.1, the second EAP Request message with Identifier=1 In Figure A.1, the second EAP Request message with Identifier=1
arrives at the EAP peer after the third EAP Request message with arrives at the EAP peer after the third EAP Request message with
Identifier=2. As a result, the EAP peer accepts the second EAP Identifier=2. As a result, the EAP peer accepts the second EAP
Request as a new EAP Request while it is just an old EAP Request Request as a new EAP Request while it is just an old EAP Request
that was already responded and the authentication might be totally that was already responded and the authentication might be totally
messed up. messed up.
This problem occurs due to the fact that EAP doesn't recognize This problem occurs due to the fact that EAP doesn't recognize
duplicate packets in the scope of one EAP protocol run, but only in duplicate packets in the scope of one EAP protocol run, but only in
the scope of current and previous packet (i.e., request and response the scope of current and previous packet (i.e., request and response
skipping to change at line 1486 skipping to change at page 45, line 4
regardless of whether it is sent as a result of a regardless of whether it is sent as a result of a
retransmission at the EAP layer or not. retransmission at the EAP layer or not.
Note: It might be possible to define other mechanisms for sequence Note: It might be possible to define other mechanisms for sequence
number handling if it can be assumed that a PAA detects EAP number handling if it can be assumed that a PAA detects EAP
retransmissions. However, such an assumption heavily depends on EAP retransmissions. However, such an assumption heavily depends on EAP
implementation details in particular on EAP APIs, thus it was implementation details in particular on EAP APIs, thus it was
decided not to use such an assumption. decided not to use such an assumption.
A.2.1. Single sequence number with EAP retransmission method A.2.1. Single sequence number with EAP retransmission method
Again, the following rules must hold: Again, the following rules must hold:
Tschofenig (ed.) Expires September 2003 27
PANA March 2003
Rule 3: Use EAP layer retransmission for retransmitting EAP messages Rule 3: Use EAP layer retransmission for retransmitting EAP messages
(based on a timer expiration). (based on a timer expiration).
Rule 4: When the PaC receives a message from the PAA, it checks the Rule 4: When the PaC receives a message from the PAA, it checks the
sequence number and discards the message if the sequence sequence number and discards the message if the sequence
number is not greater than that of the last accepted number is not greater than that of the last accepted
message. message.
Rule 5: When the PAA receives a message from the PaC, it checks the Rule 5: When the PAA receives a message from the PaC, it checks the
sequence number and discards the message if the sequence sequence number and discards the message if the sequence
number does not match a pending request message. number does not match a pending request message.
PaC PAA Seq# Message PaC PAA Seq# Message
-------------------------------------------- --------------------------------------------
1. <------- (x) PANA_auth[EAP Req ID=1] 1. <------- (x) PANA-Auth-Request[EAP Req ID=1]
2. ---+ (x) PANA_auth[EAP Res ID=1] 2. ---+ (x) PANA-Auth-Answer[EAP Res ID=1]
| (retransmission timeout at EAP-layer) | (retransmission timeout at EAP-layer)
3. | +-- (x+1) PANA_auth[EAP Req ID=1] 3. | +-- (x+1) PANA-Auth-Request[EAP Req ID=1]
| | | |
+-|--> (discarded due to Rule 5) +-|--> (discarded due to Rule 5)
| (retransmission timeout at EAP-layer) | (retransmission timeout at EAP-layer)
4. <----|-- (x+2) PANA_auth[EAP Req ID=1] 4. <----|-- (x+2) PANA-Auth-Request[EAP Req ID=1]
| |
5. -----|--> (x+2) PANA_auth[EAP Res ID=1] 5. -----|--> (x+2) PANA-Auth-Answer[EAP Res ID=1]
| |
6. <----+ (discarded due to Rule 4) 6. <----+ (discarded due to Rule 4)
7. <------- (x+3) PANA_auth[EAP Req ID=2] 7. <------- (x+3) PANA-Auth-Request[EAP Req ID=2]
. .
. .
Figure 10: Example for Single sequence number with EAP Figure 1: Example for Single sequence number with EAP retransmission
retransmission method method
This method is vulnerable to a blind DoS attack on the sequence This method is vulnerable to a blind DoS attack on the sequence
number since the PaC will accept quite a wide range of sequence number since the PaC will accept quite a wide range of sequence
numbers. For example, if an attacker blindly sends a bogus message numbers. For example, if an attacker blindly sends a bogus message
to a legitimate PaC with a randomly chosen sequence number, it will to a legitimate PaC with a randomly chosen sequence number, it will
be accepted by the PaC with 50% probability, and once this happens, be accepted by the PaC with 50% probability, and once this happens,
all messages sent from the communicating PAA will be discarded as all messages sent from the communicating PAA will be discarded as
long as they have a sequence number smaller than the accepted value. long as they have a sequence number smaller than the accepted value.
The problem of this method leads to a requirement for PaC to have a The problem of this method leads to a requirement for PaC to have a
narrow range of acceptable sequence numbers to make the blind DoS narrow range of acceptable sequence numbers to make the blind DoS
attack difficult. Note that the DoS attack cannot be prevented if attack difficult. Note that the DoS attack cannot be prevented if
the attacker is on the same IP link as PaC and able to eavesdrop the the attacker is on the same IP link as PaC and able to eavesdrop the
PANA conversation. However, the attacker needs to put itself in PANA conversation. However, the attacker needs to put itself in
promiscuous mode and thus spend more resources to eavesdrop and promiscuous mode and thus spend more resources to eavesdrop and
launch the attack (in other words, non-blind DoS attack is still launch the attack (in other words, non-blind DoS attack is still
possible as long as sequence numbers are unprotected.) possible as long as sequence numbers are unprotected.)
A.2.2. Single sequence number with PANA-layer retransmission method A.2.2. Single sequence number with PANA-layer retransmission method
The next method is still based on using a single sequence number but The next method is still based on using a single sequence number but
Tschofenig (ed.) Expires September 2003 28
PANA March 2003
the PANA-layer takes the responsibility of retransmission. The the PANA-layer takes the responsibility of retransmission. The
method uses the following rules in addition to the common rules method uses the following rules in addition to the common rules
described in section A.2. described in section A.2.
Rule 3: Use PANA-layer retransmission for retransmitting both EAP Rule 3: Use PANA-layer retransmission for retransmitting both EAP
and and
non-EAP messages (based on a timer expiration). EAP layer non-EAP messages (based on a timer expiration). EAP layer
retransmission is turned off. Retransmission based on timer retransmission is turned off. Retransmission based on timer
occurs both on PaC and PAA side, but not on both sides occurs both on PaC and PAA side, but not on both sides
simultaneously. PAA does retransmission at least for simultaneously. PAA does retransmission at least for
PANA_revocation and PANA_reauth messages, otherwise PaC PANA_Termination and PANA_Reauth messages, otherwise PaC
takes care of retransmission. takes care of retransmission.
Rule 4: When the PaC receives a message from the PAA, it accepts the Rule 4: When the PaC receives a message from the PAA, it accepts the
message if the sequence number is equal to that of the last message if the sequence number is equal to that of the last
accepted message + 1. If the sequence number is equal to accepted message + 1. If the sequence number is equal to
that of the last accepted message, the PaC retransmits the that of the last accepted message, the PaC retransmits the
last transmitted message. Otherwise, it silently discards last transmitted message. Otherwise, it silently discards
the message. the message.
Rule 5: When the PAA receives a message from the PaC, it accepts the Rule 5: When the PAA receives a message from the PaC, it accepts the
skipping to change at line 1585 skipping to change at page 47, line 5
Rule 6: The PaC retransmits the last transmitted EAP Response until Rule 6: The PaC retransmits the last transmitted EAP Response until
a new EAP Request message or an EAP Success/Failure message a new EAP Request message or an EAP Success/Failure message
is received and accepted. is received and accepted.
Rule 7: PAA must keep the copy of the last transmitted message and Rule 7: PAA must keep the copy of the last transmitted message and
must be able to retransmit it until either a valid message must be able to retransmit it until either a valid message
is received and accepted by the PAA or a timer expires. The is received and accepted by the PAA or a timer expires. The
timer is used if no new message will be sent from the PaC. timer is used if no new message will be sent from the PaC.
Tschofenig (ed.) Expires September 2003 29
PANA March 2003
PaC PAA Seq# Message PaC PAA Seq# Message
-------------------------------------------- --------------------------------------------
1. <-------- (x) PANA_auth[EAP Req ID=1] 1. <-------- (x) PANA-Auth-Request[EAP Req ID=1]
2. ---+ (x) PANA_auth[EAP Resp ID=1] 2. ---+ (x) PANA-Auth-Answer[EAP Resp ID=1]
| (retransmission timeout at PaC) | (retransmission timeout at PaC)
3. ---|----> (x) PANA_auth[EAP Resp ID=1] 3. ---|----> (x) PANA-Auth-Answer[EAP Resp ID=1]
4. | +--- (x+1) PANA_auth[EAP Req ID=2] 4. | +--- (x+1) PANA-Auth-Request[EAP Req ID=2]
| | | |
+-|--> (duplicate detected) +-|--> (duplicate detected)
5. <----|--- (x+1) PANA_auth[EAP Req ID=2] 5. <----|--- (x+1) PANA-Auth-Request[EAP Req ID=2]
| |
6. -----|--> (x+1) PANA_auth[EAP Resp ID=2] 6. -----|--> (x+1) PANA-Auth-Answer[EAP Resp ID=2]
| |
<----|--- (x+2) PANA_auth[EAP Req ID=3] <----|--- (x+2) PANA-Auth-Request[EAP Req ID=3]
7. -----|--> (x+2) PANA_auth[EAP Resp ID=3] 7. -----|--> (x+2) PANA-Auth-Answer[EAP Resp ID=3]
<----+ (discarded by PaC) <----+ (discarded by PaC)
(retransmission timeout at PaC) (retransmission timeout at PaC)
8. --------> (x+2) PANA_auth[EAP Resp ID=3] 8. --------> (x+2) PANA-Auth-Answer[EAP Resp ID=3]
9. lost<---- (x+3) PANA_auth[EAP Succ ID=3] 9. lost<---- (x+3) PANA-Auth-Request[EAP Succ ID=3]
(retransmission timeout at PaC) (retransmission timeout at PaC)
10.---->lost (x+2) PANA_auth[EAP Resp ID=3] 10.---->lost (x+2) PANA-Auth-Answer[EAP Resp ID=3]
(retransmission timeout at PaC) (retransmission timeout at PaC)
11.--------> (x+2) PANA_auth[EAP Resp ID=3] 11.--------> (x+2) PANA-Auth-Answer[EAP Resp ID=3]
12.<-------- (x+3) PANA_succ[EAP Succ ID=3] 12.<-------- (x+3) PANA-Bind-Request[EAP Succ ID=3]
(retransmission timer stopped at PaC) (retransmission timer stopped at PaC)
(deletion timeout at PAA) (deletion timeout at PAA)
(message (x+3) deleted at PAA) (message (x+3) deleted at PAA)
13.lost<---- (x+4) PANA_revocation 13.lost<---- (x+4) PANA-Termination-Request
(retransmission timeout at PAA) (retransmission timeout at PAA)
14.<-------- (x+4) PANA_revocation 14.<-------- (x+4) PANA-Termination-Request
15.---->lost (x+4) PANA_revocation_ack 15.---->lost (x+4) PANA-Termination-Answer
(retransmission timeout at PAA) (retransmission timeout at PAA)
16.<-------- (x+4) PANA_revocation 16.<-------- (x+4) PANA-Termination-Request
17.--------> (x+4) PANA_revocation_ack 17.--------> (x+4) PANA-Termination-Answer
(retransmission timer stopped at PAA) (retransmission timer stopped at PAA)
Figure 11: Example for Single sequence number with PANA-layer Figure 2: Example for Single sequence number with PANA-layer
retransmission method retransmission method
This method has an advantage of eliminating EAP layer retransmission This method has an advantage of eliminating EAP layer retransmission
by providing reliability at the PANA layer. Retransmission at the by providing reliability at the PANA layer. Retransmission at the
EAP layer has a problem with determining an appropriate EAP layer has a problem with determining an appropriate
retransmission timer value, which occurs when the lower-layer is retransmission timer value, which occurs when the lower-layer is
unreliable. In this case an EAP authenticator cannot distinguish unreliable. In this case an EAP authenticator cannot distinguish
between (i) EAP Request or EAP Response message loss (in this case between (i) EAP Request or EAP Response message loss (in this case
the retransmission timer should be calculated based on network the retransmission timer should be calculated based on network
characteristics) and (ii) long latency for EAP Response generation characteristics) and (ii) long latency for EAP Response generation
due to e.g., user input etc. (in this case the retransmission timer due to e.g., user input etc. (in this case the retransmission timer
should be calculated based on user or application characteristics). should be calculated based on user or application characteristics).
In general, the retransmission timer for case (ii) is longer than In general, the retransmission timer for case (ii) is longer than
that for case (i). If case (i) happens while the retransmission that for case (i). If case (i) happens while the retransmission
timer is calculated based on user or application characteristics, timer is calculated based on user or application characteristics,
then it might frustrate an end user since the completion of the then it might frustrate an end user since the completion of the
Tschofenig (ed.) Expires September 2003 30
PANA March 2003
authentication procedure takes unnecessarily long. If case (ii) authentication procedure takes unnecessarily long. If case (ii)
happens while the retransmission timer is calculated based on happens while the retransmission timer is calculated based on
network characteristics (i.e., RTT), then unnecessarily traffic is network characteristics (i.e., RTT), then unnecessarily traffic is
generated by retransmission. Note that in this method a PaC still generated by retransmission. Note that in this method a PaC still
cannot distinguish case (i) and case (iii) the EAP authenticator or cannot distinguish case (i) and case (iii) the EAP authenticator or
a backend authentication server is taking time to generate an EAP a backend authentication server is taking time to generate an EAP
Request. Request.
A problem of this method is that it is based on the assumption that A problem of this method is that it is based on the assumption that
EAP authenticator does not send a new EAP message until an EAP EAP authenticator does not send a new EAP message until an EAP
skipping to change at line 1699 skipping to change at page 49, line 15
Rule 4: For messages which experience a PANA layer retransmission, Rule 4: For messages which experience a PANA layer retransmission,
the retransmission timer is stopped when the message is the retransmission timer is stopped when the message is
acknowledged. acknowledged.
It is possible to carry multiple EAP sequences in a single PANA It is possible to carry multiple EAP sequences in a single PANA
sequence, with using EAP Success/Failure message as a delimiter of sequence, with using EAP Success/Failure message as a delimiter of
each EAP sequence. In this case, EAP Success/Failure message needs each EAP sequence. In this case, EAP Success/Failure message needs
to be reliably delivered. to be reliably delivered.
Tschofenig (ed.) Expires September 2003 31
PANA March 2003
A.3.1. Dual sequence number with orderly-delivery method A.3.1. Dual sequence number with orderly-delivery method
This method relies on EAP layer retransmission for EAP messages. This method relies on EAP layer retransmission for EAP messages.
This method is referred to as orderly-delivery method. The This method is referred to as orderly-delivery method. The
following rules are used in addition to the common rules. following rules are used in addition to the common rules.
Rule 5: Use the EAP-layer retransmission for retransmitting EAP Rule 5: Use the EAP-layer retransmission for retransmitting EAP
Requests (based on a timer expiration). For other PANA Requests (based on a timer expiration). For other PANA
layer messages that require a response from the peer, PANA layer messages that require a response from the peer, PANA
layer has its own mechanism to retransmit the request until layer has its own mechanism to retransmit the request until
skipping to change at line 1725 skipping to change at page 49, line 38
Rule 6: When a message is received, it is accepted if (i) the tseq Rule 6: When a message is received, it is accepted if (i) the tseq
value is greater than the tseq of the last accepted message value is greater than the tseq of the last accepted message
and (ii) the rseq falls in the range between the tseq of the and (ii) the rseq falls in the range between the tseq of the
last acknowledged message + 1 and the tseq of the last last acknowledged message + 1 and the tseq of the last
transmitted message. Otherwise, the received message is transmitted message. Otherwise, the received message is
discarded. discarded.
PaC PAA (tseq,rseq) Message PaC PAA (tseq,rseq) Message
-------------------------------------------------- --------------------------------------------------
1. <------- (x,y) PANA_auth[EAP Req, ID=1] 1. <------- (x,y) PANA-Auth-Request[EAP Req, ID=1]
2. -------> (y+1,x) PANA_auth[EAP Resp, ID=1] 2. -------> (y+1,x) PANA-Auth-Answer[EAP Resp, ID=1]
3. <------- (x+1,y+1) PANA_auth[EAP Req, ID=2] 3. <------- (x+1,y+1) PANA-Auth-Request[EAP Req, ID=2]
4. --->lost (y+2,x+1) PANA_auth[EAP Resp, ID=2] 4. --->lost (y+2,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
(retransmission timeout at EAP layer) (retransmission timeout at EAP layer)
5. <------- (x+2,y+1) PANA_auth[EAP Req, ID=2] 5. <------- (x+2,y+1) PANA-Auth-Request [EAP Req, ID=2]
6. -------> (y+3,x+2) PANA_auth[EAP Resp, ID=2] 6. -------> (y+3,x+2) PANA-Auth-Answer[EAP Resp, ID=2]
7. lost<--- (x+3,y+3) PANA_auth[EAP Req, ID=3] 7. lost<--- (x+3,y+3) PANA-Auth-Request[EAP Req, ID=3]
(retransmission timeout at EAP layer) (retransmission timeout at EAP layer)
8. +---- (x+4,y+3) PANA_auth[EAP Req, ID=3] 8. +---- (x+4,y+3) PANA-Auth-Answer[EAP Req, ID=3]
| (retransmission timeout at EAP layer) | (retransmission timeout at EAP layer)
9. <--|---- (x+5,y+3) PANA_auth[EAP Req, ID=3] 9. <--|---- (x+5,y+3) PANA-Auth-Request[EAP Req, ID=3]
10.---|---> (y+4,x+5) PANA_auth[EAP Resp, ID=3] 10.---|---> (y+4,x+5) PANA-Auth-Answer[EAP Resp, ID=3]
| |
<--+ (out of order. discarded) <--+ (out of order. discarded)
11.lost<--- (x+6,y+4) PANA_succ[EAP Succ, ID=3] 11.lost<--- (x+6,y+4) PANA-Bind-Request[EAP Succ, ID=3]
(retransmission timeout at PAA) (retransmission timeout at PAA)
12.<------- (x+7,y+4) PANA_succ[EAP Succ, ID=3] 12.<------- (x+7,y+4) PANA-Bind-Request[EAP Succ, ID=3]
13.--->lost (y+5,x+7) PANA_succ_ack 13.--->lost (y+5,x+7) PANA-Bind-Answer
(retransmission timeout at PAA) (retransmission timeout at PAA)
14.<------- (x+8,y+4) PANA_succ[EAP Succ, ID=3] 14.<------- (x+8,y+4) PANA-Bind-Request[EAP Succ, ID=3]
(dupicate detected by PaC) (dupicate detected by PaC)
15.-------> (y+6,x+8) PANA_succ_ack 15.-------> (y+6,x+8) PANA-Bind-Answer
Figure 12: Example for Dual sequence number with orderly-delivery Figure 3: Example for Dual sequence number with orderly-delivery
method method
A.3.2. Dual sequence number with reliable-delivery method A.3.2. Dual sequence number with reliable-delivery method
Tschofenig (ed.) Expires September 2003 32
PANA March 2003
This method relies solely on PANA layer retransmission for all This method relies solely on PANA layer retransmission for all
messages. This method is referred to as reliable-delivery method. messages. This method is referred to as reliable-delivery method.
The following additional rules are applied in addition to the common The following additional rules are applied in addition to the common
rules. rules.
Rule 5: Use the PANA layer retransmission for retransmitting all Rule 5: Use the PANA layer retransmission for retransmitting all
messages (based on a timer expiration). EAP retransmission messages (based on a timer expiration). EAP retransmission
is turned off. is turned off.
Rule 6: Either an ACK message is used for acknowledgment or an Rule 6: Either an ACK message is used for acknowledgment or an
skipping to change at line 1784 skipping to change at page 51, line 5
and (ii) the rseq falls in the range between the tseq of the and (ii) the rseq falls in the range between the tseq of the
last acknowledged message and the tseq of the last last acknowledged message and the tseq of the last
transmitted message. Otherwise, the received message is transmitted message. Otherwise, the received message is
discarded. discarded.
Rule 8: When a duplicate message is received, the last transmitted Rule 8: When a duplicate message is received, the last transmitted
message is retransmitted if the received message is not an message is retransmitted if the received message is not an
ACK. A message is considered as duplicate if its tseq value ACK. A message is considered as duplicate if its tseq value
is equal to the tseq of the last accepted message. is equal to the tseq of the last accepted message.
Tschofenig (ed.) Expires September 2003 33
PANA March 2003
PaC PAA (tseq,rseq) Message PaC PAA (tseq,rseq) Message
-------------------------------------------------- --------------------------------------------------
1. <------- (x,y) PANA_auth[EAP Req, ID=1] 1. <------- (x,y) PANA-Auth-Request[EAP Req, ID=1]
(user input ongoing) (user input ongoing)
2. -------> (y+1,x) PANA_ACK 2. -------> (y+1,x) PANA-Auth-Answer
(user input completed) (user input completed)
3. -------> (y+2,x) PANA_auth[EAP Resp, ID=1] 3. -------> (y+2,x) PANA-Auth-Answer[EAP Resp, ID=1]
4. <------- (x+1,y+2) PANA_auth[EAP Req, ID=2] 4. <------- (x+1,y+2) PANA-Auth-Request [EAP Req, ID=2]
5. --->lost (y+3,x+1) PANA_auth[EAP Resp, ID=2] 5. --->lost (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
(retransmission timeout at PAA) (retransmission timeout at PAA)
6. <------- (x+1,y+2) PANA_auth[EAP Req, ID=2] 6. <------- (x+1,y+2) PANA-Auth-Request [EAP Req, ID=2]
(duplicate detected by PaC) (duplicate detected by PaC)
7. -------> (y+3,x+1) PANA_auth[EAP Resp, ID=2] 7. -------> (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
8. lost<--- (x+2,y+3) PANA_auth[EAP Req, ID=3] 8. lost<--- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
(retransmission timeout at PaC) (retransmission timeout at PaC)
9. -------> (y+3,x+1) PANA_auth[EAP Resp, ID=2] 9. -------> (y+3,x+1) PANA-Auth-Answer[EAP Resp, ID=2]
(duplicate detected at PAA) (duplicate detected at PAA)
10.<------- (x+2,y+3) PANA_auth[EAP Req, ID=3] 10.<------- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
11.---+ (y+4,x+2) PANA_auth[EAP Resp, ID=3] 11.---+ (y+4,x+2) PANA-Auth-Answer[EAP Resp, ID=3]
| (retransmission timeout at PAA) | (retransmission timeout at PAA)
12.<--|---- (x+2,y+3) PANA_auth[EAP Req, ID=3] 12.<--|---- (x+2,y+3) PANA-Auth-Request [EAP Req, ID=3]
| (duplicate detected at PaC) | (duplicate detected at PaC)
13.---|---> (y+4,x+2) PANA_auth[EAP Resp, ID=3] 13.---|---> (y+4,x+2) PANA-Auth-Answer[EAP Resp, ID=3]
14.<--|---- (x+3,y+4) PANA_succ[EAP Succ, ID=3] 14.<--|---- (x+3,y+4) PANA-Bind-Request[EAP Succ, ID=3]
15.---|---> (y+5,x+3) PANA_ACK 15.---|---> (y+5,x+3) PANA-Bind-Answer
+---> (out of order. discarded) +---> (out of order. discarded)
Figure 13: Example for Dual sequence number with reliable-delivery Figure 4: Example for Dual sequence number with reliable-delivery
method method
A.3.3 Comparison of the dual sequence number methods A.3.3 Comparison of the dual sequence number methods
The orderly-delivery method is simpler than the reliable-delivery The orderly-delivery method is simpler than the reliable-delivery
method in that the former does not allow sending a separate ACK method in that the former does not allow sending a separate ACK
while the latter does. while the latter does.
In terms of authentication performance, the reliable-delivery method In terms of authentication performance, the reliable-delivery method
is better than the orderly-delivery method in that the former gives is better than the orderly-delivery method in that the former gives
skipping to change at line 1832 skipping to change at page 52, line 4
In terms of authentication performance, the reliable-delivery method In terms of authentication performance, the reliable-delivery method
is better than the orderly-delivery method in that the former gives is better than the orderly-delivery method in that the former gives
more detailed status of the link than the latter, e.g., an entity more detailed status of the link than the latter, e.g., an entity
can know whether a request has reached the communicating peer can know whether a request has reached the communicating peer
without before receiving a response. The reliable-delivery can without before receiving a response. The reliable-delivery can
reduce retransmission traffic and communication delay that would reduce retransmission traffic and communication delay that would
occur if there is no reliability, as described in section A.2.2. occur if there is no reliability, as described in section A.2.2.
A.4 Consensus A.4 Consensus
Although it is recognizable that the reliable-delivery method would Although it is recognizable that the reliable-delivery method would
be important in terms of improvement of overall authentication be important in terms of improvement of overall authentication
latency, we believe that this is a performance problem of EAP and latency, we believe that this is a performance problem of EAP and
not a problem of PANA. It is agreed that solving the EAP problem is not a problem of PANA. It is agreed that solving the EAP problem is
not the scope of PANA and simplicity is more important factor in the not the scope of PANA and simplicity is more important factor in the
PANA design. PANA design.
Tschofenig (ed.) Expires September 2003 34
PANA March 2003
As a consequence, the orderly-delivery method is chosen as the As a consequence, the orderly-delivery method is chosen as the
message transport part of PANA. message transport part of PANA.
15 Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
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Acknowledgement Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
Tschofenig (ed.) Expires September 2003 35
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