Subject: [Idr] draft-ietf-idr-tunnel-encaps-07 - sub-tlv reserved code points?

From: Jeffrey Haas <[email-masked]>
Date: Fri, 5 Jan 2018 16:16:06 -0500

As part of reading through some of the text relating to
draft-ietf-idr-tunnel-encaps, I had a concern:

:    o  Defining the sub-TLV type field so that a sub-TLV whose type is in
:       the range from 1 to 127 inclusive has a one-octet length field,
:       but a sub-TLV whose type is in the range from 128 to 254 inclusive
:       has a two-octet length field.
: 
: [...]
:    IANA is requested to change the registration policy of the "BGP
:    Tunnel Encapsulation Attribute Sub-TLVs" registry to the following:
: 
:    o  The values 0 and 255 are reserved.

IDR is aware that I'm a fan of reserving first and last code points. :-)

My concern is that the length of the length field for these reserved values
is ambiguous.  Is it 1 or 2 octets?  Unless we declare the reserved values
as malformed (not a good idea), I believe we do have to specify it.

-- Jeff