Med, this figure originally appeared in section 5.8.8 of
draft-ietf-ipfix-info-13, -14, and RFC 5102 with the bits in this order:
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+
The bits were reversed by this errata: https://www.rfc-editor.org/errata/eid2946
Also see https://www.rfc-editor.org/errata/eid1739
P.
On 19/09/2023 09:49,
[email protected]<mailto:[email protected]> wrote:
Hi all,
The description of these IEs says that “Options are mapped to bits according to
their option numbers. Option number X is mapped to bit X”, however the drawing
does not reflect that (tcpOptions):
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+
8 9 10 11 12 13 14 15
+-----+-----+-----+-----+-----+-----+-----+-----+
... | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |...
+-----+-----+-----+-----+-----+-----+-----+-----+
16 17 18 19 20 21 22 23
+-----+-----+-----+-----+-----+-----+-----+-----+
... | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 |...
+-----+-----+-----+-----+-----+-----+-----+-----+
. . .
56 57 58 59 60 61 62 63
+-----+-----+-----+-----+-----+-----+-----+-----+
... | 63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 |
+-----+-----+-----+-----+-----+-----+-----+-----+
I suspect that the confusion is rooted in the interpretation of “bit X”: as (1)
“bit position X” or the resulting (2) “binary value”:
* If (1) is followed, then bit#0 would be mapped to option 0, bit#1 to
option 1, and so on. This logic is followed, e.g., for ipv6ExtensionHeaders.
* If (2) is followed, then bit#63 would be mapped to option 0, bit#62 to
option 1, and so on.
In both cases, the drawing is not aligned with the narrative text. We may
either consider updating the drawing or the text.
Which change is likely to have less impact on existing implementations? FWIW,
(1) is what was followed in RFC5102 but changed since then by errata.
Thank you.
Cheers,
Med
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