Rene Struik writes:
> According to the 15.4e spec, the value of the IE List Present field
> in the FCF signals whether or not IEs are included in the frame (see
> Clause 5.2.11.5b).
This is true.
> Header and Payload IEs can be distinguished via the Type field (bit
> 15: set to zero if Header IE; set to one otherwise) and are
> self-contained TLV data objects (see Clauses 5.2.4.2 and 5.2.4.3).
This is not. Nothing in the 802.15.4e says that there cannot be long
format for header IEs, or that you cannot have short format for
payload IEs. On the other hand the section 5.2.2.6.17 says:
5.2.2.6.17 IEs field
The IEs field is variable in length and is present if the IEs
Present field is set to one. The format of IEs is specified in
5.2.4. It contains Header IEs, followed by Payload IEs. Each
type of IE list is terminated as required per 5.2.4.22.
I.e. both IE lists are terminated as required per 5.2.4.22. The
5.2.4.22 says:
5.2.4.22 IE List Termination IE
The Header IE list is terminated with an IE List Termination
IE (ID = 0x7e or 0x7f) that has a content length of zero.
Explicit termination is required after a Header IE if there is
one or more Payload IEs (0x7e), or MAC payload (0x7f),
following the Header IE list. If an unformatted payload
follows the Payload IE list, then the payload IE list is
terminated with a list termination IE (ID = 0xf) that has a
content length of zero. Otherwise the terminator may be
omitted.
I.e. no header termination IE is needed if there is nothing coming
after it. The 0x7e is needed if there is Payload IEs after Header IEs,
and 0x7f is needed if there is no Payload IEs, but there is payload
after it.
> Note that IEs should only be processed at receipt after successful incoming
> frame security processing (i.e., IEs can be assumed to be available in the
> clear for this discussion).
Actually this is not specified in the 802.15.4e... Also several of
those IEs are processed by MAC, and even if the frame is accepted from
node A with data payload, that does not mean that all IEs in that
frame is something that will be accepted.
In the 802.15.4rev there is new security tables similar to the Frame
security tables for IEs, to specify whether they are accepted or
ignored by the MAC.
--
[email protected]
_______________________________________________
6tisch mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/6tisch
