Wireshark-bugs: [Wireshark-bugs] [Bug 6445] Ethernet CFM MAID decode error

Date: Thu, 10 Nov 2011 13:42:19 -0800 (PST)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6445

Bill Meier <wmeier@xxxxxxxxxxx> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID

--- Comment #1 from Bill Meier <wmeier@xxxxxxxxxxx> 2011-11-10 16:42:17 EST ---
> From protocol Display Filter Reference: CFM EOAM 802.1ag/ITU Protocol
> http://www.wireshark.org/docs/dfref/c/cfm.html
> 
> cfm.maid.ma.name String Short MA Name 1.0.0 to 1.6.2 (Should be fixed 48 Bytes)
> cfm.maid.ma.name.format Unsigned 8-bit integer Short MA Name (MEG ID) Format
> 1.0.0 to 1.6.2 (No such field in Y.1731 or 802.1ag)
> cfm.maid.ma.name.length Unsigned 8-bit integer Short MA Name (MEG ID) Length
> 1.0.0 to 1.6.2 (No such field in Y.1731 or 802.1ag)

1. Actually: it appears to me that your statements above are incorrect with
   respect to "should be ..." and "no such field".

   From section 21.6.5 of the 802.1ag standard:

  "21.6.5 Maintenance Association Identifier
  (48 octets) This field contains the MAID of the transmitting MEP. It is 
  divided into six subfields, plus, if
  necessary, a pad of octets contains 0 to fill out its fixed length. The
  subfields are:
  a) Maintenance Domain Name Format (21.6.5.1);
  b) Maintenance Domain Name Length (21.6.5.2);
  c) Maintenance Domain Name (21.6.5.3);
  d) Short MA Name Format (21.6.5.4);
  e) Short MA Name Length (21.6.5.5); and
  f) Short MA Name (21.6.5.5).
  ..."

2. According to the standard, the MAIDs in the cfm ccm packets in the attached 
   pcap file are, in fact, not valid. 

   Also: The ethernet MAC addresses appear to be "made-up" addresses:
   00:...:12:34  and 00:...:43:21.

   How was this capture created ?

   See the capture file attached to Bug #5517 for valid CFM CCM messages which 
   contain MAIDs which conform to the 802.1ag standard.


I'm marking this bug as "invalid". If I've missed something you can reopen the
bug.

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