Hi Joe,

The proposed new Sections "2.1 Retransmission" and "2.2 Re-Authentication" are 
intended to be added to draft-ietf-abfab-eapapplicability (and not intended be 
added to RFC 3748), right?

If so, then the following sentence in Section 2.2 should be written from 
application perspective in the same way as Section 2.1 for consistency:

"Lower layers SHOULD describe whether re-authentication is provided and which 
parties can initiate it."

Applications SHOULD describe whether re-authentication is provided and which 
parties can initiate it.

Regards,
Yoshihiro Ohba

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of 
Joseph Salowey (jsalowey)
Sent: Saturday, February 23, 2013 8:37 AM
To: [email protected]
Subject: [abfab] Summary of proposed changes to eat applicability document

After going through the comments on the list here is where I think we are with 
changes to the document:

1) Section 3 

OLD
   It is important
   for the protocol carrying EAP to prove possession of the EAP MSK
   between the EAP Peer and EAP Authenticator.

NEW
The protocol carrying EAP MUST prove possession of the EAP MSK
   between the EAP Peer and EAP Authenticator.

ADD

In the context of EAP for Application-Layer Access the application is providing 
the EAP Lower Layer.   Applications protocols vary so their specific behavior 
and transport characteristics needs to be considered when determining their 
retransmission and re-authentication behavior as discussed in section 3.  


3)  Retransmissions

ADD 

2.1 Retransmission

In EAP, the authenticator is responsible for retransmission. By default EAP 
assumes that the lower layer (the application in this context) is unreliable. 
The authenticator can send a packet whenever its retransmission timer triggers. 
In this mode, applications need to be able to receive and process EAP messages 
at any time during the authentication conversation.

Alternatively, EAP permits a lower layer to set the retransmission timer to 
infinite. When this happens, the lower layer becomes responsible for reliable 
delivery of EAP messages. Applications that use a lock-step or client-driven 
authentication protocol might benefit from this approach.

In addition to retransmission behavior applications need to deal with discarded 
EAP messages. For example, whenever some EAP methods receive  erroneous input, 
these methods discard the input rather than generating an error response. If 
the erroneous input was generated by an attacker, legitimate input can 
sometimes be received after the erroneous input. Applications MUST handle 
discarded EAP messages, although the specific way in which discarded messages 
will be handled depend on the characteristics of the application. Options 
include failing the authentication at the application level, requesting an EAP 
retransmit and waiting for additional EAP input.   

Specifications of how EAP is used for application authentication SHOULD 
document how retransmission and message discards are handled.

4) Re-Authentication

ADD

2.2 Re-Authentication

EAP lower layers MAY provide a mechanism for re-authentication to happen within 
an existing session [RFC 3748]. Diameter standardizes a mechanism for a AAA 
server to request re-authentication [RFC 4005]. Re-authentication permits 
security associations to be updated without establishing a new session. For 
network access, this can be important because interrupting network access can 
disrupt connections and media.

Some applications might not need re-authentication support. For example if 
sessions are relatively short-lived or if sessions can be replaced without 
significant disruption, re-authentication might not provide value. Protocols 
like HypertextTransport Protocol (HTTP) and Simple Mail Transport Protocol 
(SMTP) are examples of protocols where establishing a new connection to update 
security associations is likely to be sufficient.

Re-authentication is likely to be valuable if sessions or connections are 
long-lived or if there is a significant cost to disrupting them.

Another factor may make re-authentication important. Some protocols only permit 
one part in a protocol (for example the client) to establish a new connection. 
If another party in the protocol needs the security association refreshed then 
re-authentication can provide a mechanism to do so.

Lower layers SHOULD describe whether re-authentication is provided and which 
parties can initiate it.
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