Hi Eric/John, How about this text -
Length (16 bits): indicates the length of the value portion in bytes. It MUST be in multiples of 4 and greater than 0. Thanks! Dhruv On Mon, Oct 17, 2022 at 9:18 PM Eric Vyncke (evyncke) <[email protected]> wrote: > John > > I got the information from the section 7.1 indeed and when the value parts > are in 32-bit words, then it is a multiple of 4 octets, i.e., 0, 4, 8, ... > while my first reading would be 0, 1, 2 (as the unit appeared to be 32-bit > words and not octets) > > -éric > > On 17/10/2022, 15:30, "John Scudder" <[email protected]> wrote: > > One additional comment to Éric’s point -- > > > On Oct 17, 2022, at 3:44 AM, Éric Vyncke via Datatracker < > [email protected]> wrote: > > > > `Length (16 bits): multiple of 4 octets.` is rather confusing... Is > this field > > counting 32-bit words ? I had to read RFC 5440 to understand that > the 'value' > > part is always a multiple of 4 octets. Strongly suggest to say > "Length (16 > > bits): length of the value expressed in octets”. > > This seems like a good change, but if the multiple-of-4 constraint is > required I think you’d need to add more words, as in “Length (16 bits): > length of the value, expressed in octets. This value MUST be a multiple of > 4. (And at least 4? Or is 0 a legal value?) > > Éric, I took a look at RFC 5440, §7.1, "PCEP TLV Format” seems to be > the applicable section. It has this: > > The Length field defines the length of the value portion in bytes. > The TLV is padded to 4-bytes alignment; padding is not included in > the Length field (so a 3-byte value would have a length of 3, but > the > total size of the TLV would be 8 bytes). > > If that’s what you were thinking of, ISTM it explicitly says the > length field does not have to be a multiple of 4. So AFAICT this is indeed > a new requirement and should be expressed here, but you’re right that it > can be clearer. I believe multiple-of-4 is a genuine requirement, related > to "The LSP Extended Flags field is an array of units of 32 flags” (§3.2). > > If I’ve missed some other part of RFC 5440 that you were referring to, > I’d be curious to know what it was. I do see that §7.2 has “MUST always be > a multiple of 4, and at least 4”, but that’s for PCEP objects which this > spec isn’t, rather it’s a TLV within an object, and AFAICT that doesn’t > have the same constraint in the base spec. > > Thanks, > > —John > >
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