Subject: [Lsr] Martin Duke's No Objection on draft-ietf-lsr-isis-invalid-tlv-02: (with COMMENT)

From: Martin Duke via Datatracker <[email-masked]>
Date: Sat, 11 Jul 2020 09:07:59 -0700

Martin Duke has entered the following ballot position for
draft-ietf-lsr-isis-invalid-tlv-02: No Objection

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
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-lsr-isis-invalid-tlv/

----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

It might be helpful to define “ignore” as “skip the number of octets indicated
by the length field.” An alternate interpretation might skip the number of
bytes implied by the type code, if the type is known.

Similarly, I take it that a length value beyond the end of the message ends
processing of the PDU, but the PDU as a whole MUST NOT be discarded.

---

From: "Les Ginsberg (ginsberg)" <[email-masked]>
Date: Sat, 11 Jul 2020 20:57:35 +0000

Martin -

Thanx for your review.
Responses inline.

> -----Original Message-----
> From: Martin Duke via Datatracker <[email-masked]>
> Sent: Saturday, July 11, 2020 9:08 AM
> To: The IESG <[email-masked]>
> Cc: [email-masked]; [email-masked]; [email-masked];
> Christian Hopps <[email-masked]>; [email-masked];
> [email-masked]
> Subject: Martin Duke's No Objection on draft-ietf-lsr-isis-invalid-tlv-02: (with
> COMMENT)
> 
[Les:] The definition of TLV as:

Type
Length (# of octets of data)
Data

comes from the base specification (ISO 10589).

There is no encoding which omits the Length - nor one which allows for the value in the length field to be ignored and a fixed length to be associated based on the Type.
Doing that would compromise the ability to extend the protocol as nodes which do not recognize a new TLV type would have no idea how many octets to skip unless the length field were valid.

> processing of the PDU, but the PDU as a whole MUST NOT be discarded.

[Les:] You are correct.
Note that the scope of this draft is to make explicit how to handle invalid TLVs independent of validation of the PDU in which the TLVs appear.
Discussion of this case is therefore out of scope of the draft.

   Les