Subject: [dtn] draft-ietf-dtn-bpbis-25: ABNF "dtn" URI scheme

From: Alvar Penning <[email-masked]>
Date: Fri, 29 May 2020 14:58:26 +0200

Dear all,

thanks for releasing the 25th draft of the Bundle Protocol. As I read
the changes, I found the Augmented Backus-Naur Form of the URI schemas
quite useful. However, I have a question about this.

In section 4.1.5.1.1[0] a straight forward ABNF is defined for the
"dtn" URI scheme:

> dtn-uri = "dtn:" dtn-hier-part
> dtn-hier-part = "//" node-name name-delim demux ; a path-rootless
> node-name = 1*VCHAR
> name-delim = "/"
> demux = *VCHAR

Some `dtn-uri` is defined as the concatenation[1] of "dtn:" and a
`dtn-hier-part`. A `dtn-hier-part` starts with two leading slashes
("//") and one slash ("/", `name-delim`) follows a nonempty
`node-name`. Various characters might follow. The line ends with a
comment[2].

Thus, some "dtn" URI has at least the following form: "dtn://NODE-NAME/"

The following paragraph within this section defines the null endpoint as
"dtn:none". However, as far as I understand this does not fit the ABNF
defined above.

If I am not wrong on this, I would like to suggest a new rule for the
"none" `dtn-hier-part`. This could look like the following:

> dtn-hier-part =  "none" 
> dtn-hier-part =/ "//" node-name name-delim demux

Otherwise, the null endpoint could be renamed to "dtn://none/" to match
the current ABNF. Note, a node named "none" and the null endpoint may
get mixed up.

I would be pleased about comments in this regard.

Best regards,
Alvar

[0]:https://tools.ietf.org/html/draft-ietf-dtn-bpbis-25#section-4.1.5.1.1
[1]:https://tools.ietf.org/html/rfc5234#section-3.1
[2]:https://tools.ietf.org/html/rfc5234#section-3.9