Hi Acee, Thanks for the quick reply. Please find comments inline. > On Aug 31, 2017, at 5:50 AM, Acee Lindem (acee) <a...@cisco.com> wrote: > > Hi Suresh, > > On 8/30/17, 10:49 PM, "Suresh Krishnan" <suresh.krish...@gmail.com > <mailto:suresh.krish...@gmail.com>> wrote: > > Suresh Krishnan has entered the following ballot position for > draft-ietf-ospf-encapsulation-cap-06: Discuss > > When responding, please keep the subject line intact and reply to all > email addresses included in the To and CC lines. (Feel free to cut this > introductory paragraph, however.) > > > Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html > <https://www.ietf.org/iesg/statement/discuss-criteria.html> > for more information about IESG DISCUSS and COMMENT positions. > > > The document, along with other ballot positions, can be found here: > https://datatracker.ietf.org/doc/draft-ietf-ospf-encapsulation-cap/ > <https://datatracker.ietf.org/doc/draft-ietf-ospf-encapsulation-cap/> > > > > ---------------------------------------------------------------------- > DISCUSS: > ---------------------------------------------------------------------- > > * There seems to be an difference between this document's definition of > sub-TLVs (with 2 octet types and lengths) and those of RFC5512 (with 1 octet > types and lengths). So I am surprised to see the document point to the RFC5512 > based TLVs for both syntax and semantics (Sections 5.1, 5.2, 5.3 ...) . Can > you > please explain how these sub-TLVs are encoded on the wire to be compatible > with > this draft? > > I can answer this one since I specifically told the authors to use this > format. If you look at RFC 7770, you’ll see that all OSPF Router Information > (RI) LSA TLVs and Sub-TLVs have 2 octet types and lengths. > > 2.3. OSPF Router Information LSA TLV Format > > The format of the TLVs within the body of an RI LSA is the same as > the format used by the Traffic Engineering Extensions to OSPF [TE]. > The LSA payload consists of one or more nested Type/Length/Value > (TLV) triplets. The format of each TLV is: > > 0 1 2 3 > 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | Type | Length | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > | Value... | > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > Figure 3. TLV Format > > > Additionally, if you look at > https://www.ietf.org/id/draft-ietf-idr-tunnel-encaps-07.txt > <https://www.ietf.org/id/draft-ietf-idr-tunnel-encaps-07.txt> (which > obsoletes RFC 5512), you’ll see that the 1 octet length with insufficient. > > Each sub-TLV consists of three fields: a 1-octet type, a 1-octet or > 2-octet length field (depending on the type), and zero or more octets > of value. A sub-TLV is structured as shown in Figure 2: > > +-----------------------------------+ > | Sub-TLV Type (1 Octet) | > +-----------------------------------+ > | Sub-TLV Length (1 or 2 Octets)| > +-----------------------------------+ > | Sub-TLV Value (Variable) | > | | > +-----------------------------------+ > > Figure 2: Tunnel Encapsulation Sub-TLV Format > > o Sub-TLV Type (1 octet): each sub-TLV type defines a certain > property about the tunnel TLV that contains this sub-TLV. > > > > > > Rosen, et al. Expires January 18, 2018 [Page 7] > > Internet-Draft Tunnel Encapsulation Attribute July 2017 > > > o Sub-TLV Length (1 or 2 octets): the total number of octets of the > sub-TLV value field. The Sub-TLV Length field contains 1 octet if > the Sub-TLV Type field contains a value in the range from 1-127. > The Sub-TLV Length field contains two octets if the Sub-TLV Type > field contains a value in the range from 128-254. > > o Sub-TLV Value (variable): encodings of the value field depend on > the sub-TLV type as enumerated above. The following sub-sections > define the encoding in detail. I did read the draft-ietf-idr-tunnel-encaps-07 draft (following it from the references) and I do understand why the document made the switch to 2 octets for the length. The part that threw me off is that this document (ospf-encapsulation) mandates *2 Octet* sub-TLV types which are not even mentioned in draft-ietf-idr-tunnel-encaps-07. Similarly this document mandates 2 octet lengths without nuancing the length based on sub-TLV type (>127 or not). And then it states that the syntax is specified in the documents that use 1 octet types. This is the discrepancy that needs addressing.
Thanks Suresh
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