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

["Les Ginsberg (ginsberg)" <[e-mail]>]

Martin -

Thanx for your review.
Responses inline.

> -----Original Message-----
> From: Martin Duke via Datatracker <[e-mail]>
> Sent: Saturday, July 11, 2020 9:08 AM
> To: The IESG <[e-mail]>
> Cc: [e-mail]; [e-mail]; [e-mail];
> Christian Hopps <[e-mail]>; [e-mail];
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> Subject: Martin Duke's No Objection on draft-ietf-lsr-isis-invalid-tlv-02: (with
> COMMENT)
> 
> Martin Duke has entered the following ballot position for
> draft-ietf-lsr-isis-invalid-tlv-02: No Objection
> 
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> 
> ----------------------------------------------------------------------
> 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.
> 
[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.

> 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.

[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

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