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									IEEE 802.21 MEDIA INDEPENDENT HANDOVER
DCN: 21-07-0373-00-0000
Title: Issues on UIR bit
Date Submitted: October, 28, 2007
Presented at IEEE 802.21 session 22.5 in New Jersey
Authors or Source(s):
Yoshihiro Ohba
Abstract: This contribution analyzes issues related to UIR bit of
 MIH protocol header for resolution of SB Comment 206.




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      UIR (Unauthenticated Information Request)

• The current definition of UIR bit (Page 151, Line 43):
    “This field is used to indicate if the protocol message is sent
     preauthentication/pre-association so that the length of the
     response message can be limited.”

• Sponsor Ballot Comment 206:

    Comment: “UIR bit usage is not clear. Which entity is
     supposed to set this bit? If MN is supposed to set this bit,
     how PoS can trust that MN is authenticated when the bit is
     not set? The underlying assumption for the response limiting
     using this bit to work is not clear.”
    Suggestion: “Delete the UIR bit or add more text that answers
     to those questions.
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      Issue 1: Transport Protocol Dependency
• It seems that PoA is responsible for setting the UIR bit of MIH messages
  originated by unauthenticated MN, and thus PoA needs to be a trusted entity
  to PoS.

• What is the identity of PoA?

• The Source Identifier TLV does not serve for identifying PoA if it is MN’s
  MIHF-ID

• The identity of PoA must be a transport protocol dependent identifier such as
  an IP address

• This means that the access control mechanism using UIR bit has transport
  protocol dependency, as opposed to its original purpose

• With transport protocol dependency, other solutions are possible without use
  of UIR, by using different transport protocol dependent identifiers to
  distinguish MIH messages originated from unauthenticated MNs, such as
  use of different IP addresses and/or port numbers
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  Issue 2: Access Control Responsibility
• It is not clear whether MIHF or MIH user on PoS is responsible
  for the execution of access control using the UIR bit, including:
    •   limiting the response message size
    •   limiting the types of IEs to be included in the response
        message

• If MIHF is responsible for the access control, MIHF can be
  very complex since it has to know service-specific contents

• If MIH user is responsible for the access control, the access
  control mechanism does not work since there is no parameter in
  any MIH primitive to convey the UIR bit

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                        Conclusion
• The need for UIR bit is not clear and its definition is incomplete


• MIH-level access control being studied in Security SG is more
  appropriate to address the access control issue for
  unauthenticated MN


• Suggestion: Remove UIR bit from the specification and expect
  future Security Task Group to solve the problem




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