ASN.1 Module for new types

[jiceatscion]

(Moved from https://github.com/scionassociation/standards/issues/62)

Russ Housley suggested that we could add an appendix for new types (with an ASN.1 module)

Finally, you might want to consider an ASN.1 Module in an appendix for any new types that you are defining. It will make it easier for others to implement.

Also, at IETF 115, he recommended:

In Section 3.1.3, I suggest that you assign a content type for the TRC payload (you are currently using id-data).

[nicorusti]

We received some more feedback from Russ:

I have a few suggestions.
I think that Section 2.2.1.2.1 could be much more simple:
The ISD-AS number attribute identifies the SCION ISD and AS. The
attribute type id-at-ia is defined as:

  id-scion ::= OBJECT IDENTIFIER {1 3 6 1 4 1 55324}

  id-at-ia AttributeType ::= {id-scion id-cppki(1) id-at(2) 1}

Please turn Section 3.1.2.1 into an ASN.1 module so that it is clear where IMPORTed types are defined and whether IMPLICIT ot EXPLICIT tags are being used.

Russ

@jiceatscion @matzf FYI

[nicorusti]

@jiceatscion @matzf do you think this could be addressed? Text in the draft comes from the scionproto docs, it was added in scionproto/scion#3742

@oncilla @scrye could you help address this?