Re: [IPFIX] IPFIX: boolean, dot1qDEI and dot1qCustomerDEI
Andrew Feren <[email protected]>
| Newsgroups | gmane.ietf.ipfix |
|---|---|
| Message-ID | <[email protected]> |
Hi Paul, all, I think some clarification is needed, but I'm not sure what the right answer is. I see at least three valid readings of the combination of boolean, flags, and "The value of the 1-bit Drop Eligible Indicator (DEI) field" 1) send "the value": if DEI bit set (0x01) / unset (0x00) (looks a lot like least significant bit set/unset ;-) This is what the initial correction seems to assume. 2) semantics "flags": if DEI bit set (0x10) / unset (0x00). This is the interpretation that including pcp would require 3) strict data type "boolean": if DEI bit set (0x01) / unset (0x02). This is a variation on option 1 where boolean was interpreted strictly. 1 and 2 can be viewed as the same except for which bit gets flipped. On 09/03/2013 05:57 AM, Paul Aitken wrote: > Yaakov, > >> Fine with me since it simplifies the interpretation (DEI=0 means >> green and DEI=1 means yellow). >> >> By first bitdo you mean least significant bit? >> > > Yes. If needs be we could add a figure something like so: > > 0 1 2 3 4 5 6 7 > +-----+-----+-----+-----+-----+-----+-----+-----+ > | Reserved | DEI | > +-----+-----+-----+-----+-----+-----+-----+-----+ This is option 1 and is compatible with 3 as long as reserved bit 6 is never used. Option 2 only ever sets bit 7 to 0, but does change bit 3 in the reserved area. > > > Although if we were defining this again, it might be more useful to > retain the DEI position, and potentially include the PCP bits. > > So, per 802.1Q-2011 Figure 9-1 (attached) : > > 0 1 2 3 4 5 6 7 > +-----+-----+-----+-----+-----+-----+-----+-----+ > | PCP | DEI | Reserved | > +-----+-----+-----+-----+-----+-----+-----+-----+ > > However I suspect that this is incompatible with current > implementations, so the change is not possible? This is a total change as this is no longer just dot1qDEI. I'm slightly in favor of option 1, but ultimately I simply don't want to receive an identical value from different exporters which I am expected to interpret differently. -Andrew > > P. > > >> *From:*Paul Aitken [mailto:[email protected]] >> *Sent:* 02 September, 2013 21:46 >> *To:* IETF IPFIX Working Group; [email protected] >> *Cc:* Yaakov Stein >> *Subject:* IPFIX: boolean, dot1qDEI and dot1qCustomerDEI >> >> Dear IPFIX experts, >> >> While reviewing IANA's IPFIX registry, I noticed that although IEs >> #388 dot1qDEI and #389 dot1qCustomerDEI are defined as "boolean" >> their definitions do not correspond to that type. >> >> As a reminder, RFC5101bis says: >> >> 6.1.5. boolean >> >> The boolean data type is specified according to the TruthValue in >> [RFC2579]. It is encoded as a single-octet integer per >> Section 6.1.1,with the value 1 for true and value 2 for false. >> Every other value is undefined. >> >> >> (for consistency with MIB truthValue). >> >> So a boolean IE cannot capture a bit field such as the DEI required >> by #388 and #389. I checked the other boolean IEs, and they're fine. >> >> To correct this, I propose that #388 and #389 be changed from >> "boolean" to "unsigned8", in line with all the other flags fields: >> >> 388 >> >> >> >> dot1qDEI >> >> >> >> boolean >> unsigned8 >> >> >> >> flags >> >> >> >> current >> >> >> >> >> The first bit of this octet is the value of the 1-bit Drop Eligible >> Indicator (DEI) field of the VLAN tag as described in 802.1Q-2011 >> subclause 9.6. In case of a QinQ frame, it represents the outer tag's >> DEI field and in case of an IEEE 802.1ad frame it represents the DEI >> field of the S-TAG. Note: in earlier versions of 802.1Q the same bit >> field in the incoming packet is occupied by the Canonical Format >> Indicator (CFI) field, except for S-TAGs. >> The remainder of this octet is reserved for future use. >> >> 389 >> >> >> >> dot1qCustomerDEI >> >> >> >> boolean >> unsigned8 >> >> >> >> flags >> >> >> >> current >> >> >> >> >> In case of a QinQ frame, the first bit of this octet it represents >> the inner tag's Drop Eligible Indicator (DEI) field and in case of an >> IEEE 802.1ad frame it represents the DEI field of the C-TAG. >> The remainder of this octet is reserved for future use. >> >> >> >> Feedback? >> >> P. >> > > > > _______________________________________________ > IPFIX mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/ipfix _______________________________________________ IPFIX mailing list [email protected] https://www.ietf.org/mailman/listinfo/ipfix