Re: [STDS-802-16] Clarification on the CRC in the MAC PDU
Yes, the CRC is part of the MPDU and so is included in the length. This
is my interpretation and consistent with the interpretation of others it
seems.
For an example of a practical implication of this, the AES_CCM example
code I provided ( https://www.deadhat.com ) has to adjust the GMH length
field to include the PN, ICV and CRC length *before* the ICV generation
since the value of the ICV will be affected by the on air GMH value.
DJ
-----Original Message-----
From: owner-stds-802-16@listserv.ieee.org
[mailto:owner-stds-802-16@listserv.ieee.org] On Behalf Of Jonathan Labs
Sent: Thursday, March 25, 2004 9:29 AM
To: STDS-802-16@listserv.ieee.org
Subject: [STDS-802-16] Clarification on the CRC in the MAC PDU
Could someone please clarify an ambiguity I am seeing regarding the MAC
PDU and the CRC? When present, is the CRC considered part of the MAC
PDU or is it like and appendix?
Here are the sections in P802.16-REVd/D3, that suggest on or the other
interpretation:
--Section 6.4.2, page 53, line 15, "A MAC PDU may contain a CRC, as
described in 6.4.3.5.". --Page 54, Table 5, Row 1: CI Description: "1 =
CRC is appended to the PDU." --Section 6.4.3.5 CRC calculation: "A
service flow may require that a CRC be appended to each MAC PDU carrying
data for that service flow (11.13.14). In this case, a CRC, as defined
in IEEE 802.3, shall be included in each MAC PDU..."
The reason for differentiating is because the LEN field in the MAC
header (Table 5) is "The length in bytes of the MAC PDU including the
MAC header."
So I guess the real question is, does the LEN field include the length
of the CRC when present?
Thanks for your help.
Jon