Subject: [Sigtran] SCTP : ambiguity in handling invalid cookie in COOKIE ECHO chunks

From: ash kat <[email-masked]>
Date: Thu, 13 Apr 2006 04:42:29 -0700 (PDT)

Hi All
   
  I was looking at the behavior of SCTP stack when the COOKIE ECHO chunk contains the invalid cookie.
   
  The following section of RFC2960 are conflicting each other:
   
  Section 4 (Page# 50)
   Notes:
     1) If the State Cookie in the received COOKIE ECHO is invalid (i.e.,
      failed to pass the integrity check), the receiver MUST silently
      discard the packet.  Or, if the received State Cookie is expired
      (see Section 5.1.5), the receiver MUST send back an ERROR chunk.
      In either case, the receiver stays in the CLOSED state.
   
  Section 5.1 (Page# 52)
     If an endpoint receives an INIT, INIT ACK, or COOKIE ECHO chunk but
   decides not to establish the new association due to missing mandatory
   parameters in the received INIT or INIT ACK, invalid parameter
   values, or lack of local resources, it MUST respond with an ABORT
   chunk.  It SHOULD also specify the cause of abort, such as the type
   of the missing mandatory parameters, etc., by including the error
   cause parameters with the ABORT chunk.  The Verification Tag field in
   the common header of the outbound SCTP packet containing the ABORT
   chunk MUST be set to the Initiate Tag value of the peer.
   
  Section 5.1.5 (Page# 56)
   
     2) Authenticate the State Cookie as one that it previously generated
      by comparing the computed MAC against the one carried in the State
      Cookie.  If this comparison fails, the SCTP packet, including the
      COOKIE ECHO and any DATA chunks, should be silently discarded.
   
  Please help me resolving this conflict.
   
  In my point of view there should be only one of these three actions, which should be specified when the SCTP receive the COOKIE ECHO chunk with an invalid cookie.
  i) MUST silently discard
  ii) MUST respond with an ABORT
  iii) should be silently discarded.
   
  ----------
  K. Äsh
  ----------

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