Last Call: 'RPSLng' to Proposed Standard

On Tue, 26 Aug 2003, The IESG wrote:
> The IESG has received a request from an individual submitter to consider 
> 'RPSLng' <draft-blunk-rpslng-01.txt> as a Proposed Standard. This document 
> has been reviewed in the IETF but is not the product of an IETF Working 
> Group. 
[...]
> File(s) can be obtained via
> http://www.ietf.org/internet-drafts/draft-blunk-rpslng-01.txt

If I'd use the "sirs (or airs)" classification of this document review, 
I'd say:

     *    This draft is on the right track but has open issues,
          described in the review.
 
Below are my comments to the draft.  Overall, I think the document is 
pretty good, and a very relevant piece of work; it's needed by IPv6 ops 
folks.

However, there seem to be a number of (more or less) textual inaccuracies 
and confusion in the document, which should be settled prior to 
publication.

I think there are the three most important issues here are:

 * issue 2) -- how to co-exist from RPSL: if RPSL and RPSL give you 
conflicting information about IPv4 unicast, then what?

 * issue 3) -- whether ipvX should imply only unicast or both unicast and 
multicast?

 * issue 5) and others-- whether the document needs to specify all the
relevant modifications explicitly, or not.  IMHO, Stds Track document 
should describe every change, not just say something like "other 
attributes are modified in a similar fashion" (or something to that 
effect)

substantial
-----------

1) would it be useful to have the RPSLng document have "Updates: 2622, 2725", or
something like that -- if for no other reason than to have a forward
references in the RFC index to this document?

2) one important aspect to consider is interaction with old specification,
that is:

   Keeping this in mind, the "import:", "export:", and "default:"
   attributes implicitly specify IPv4 unicast policy and remain as
   defined previously in RPSL, and new multi-protocol (prefixed with the
   string "mp-") attributes are introduced. These will be described
   below.

==> so, should one get information from both the RPSLng multiprotocol
attributes and the old ones?  What if they conflict?  Maybe some words would
be useful on how to effectively transition/co-exist with both RPSL and
RPSLng?

3) I note that there is no way to specify "these attributes affect both
multicast and unicast", you have to always include the both, in:

   The possible values for <afi> are:
                                                                                                       
      ipv4
      ipv4.unicast (equivalent to ipv4)
      ipv4.multicast
      ipv6
      ipv6.unicast (equivalent to ipv6)
      ipv6.multicast

==> is this intended?  Is there a particular reason why we couldn't just
assume that "ipv4" includes both unicast and multicast?  Where multicast is
deployed, it's typically mostly congruent with unicast infrastructure, and
where it isn't, I guess it wouldn't hurt to have "ipv4 = ipv4.{both}"
implication?  Or should there be a separate value which would imply the
both?

4) it seems that ipv6_address dictionary attribute (though trivial) has not
been defined:

   In order to support IPv6 addresses specified with the next-hop
   rp-attribute, a new predefined dictionary type entitled ipv6_address
   is added to the RPSL dictionary.

==> this should probably be something like:

   <ipv4_address> An IPv6 address is represented as [blah blah blah]

5) As the document is Standards Track (and not e.g. Informational, which
would also be a possibility), I'm not sure whether it's appropriate to wave
away some, possibly important, pieces of the specification, with like:

2.3.2 <mp-filter>
                                                                                                       
   The <mp-filter> expression is an extension of the RPSL <filter>
   expression [section 5.4 of RFC 2622 [1]], with the inclusion of the
   ability to specify IPv6 address prefixes in Address-Prefix sets.  For
   the sake of brevity, we do not include the full definition of
   <mp-filter> here and refer the reader to RFC 2622 [1].

and:

4.5 inet-rtr Class

   The "mp-peer:" attribute is defined below.  The difference between
   this attribute and the "peer:" attribute is the inclusion of support
   for IPv6 addresses.

6) there seem to be a case or two where it is not clear whether including
the discussion in this specification is appropriate (and just not
implementation-specific issues, or issues relating to the user's RPSL user
interface); in below, the last sentence seems a bit dubious:

   The evaluation of an <import-expression> is done by evaluating all of
   its components. Evaluation of peering-sets and filter-sets is
   constrained by the address family. Such constraints may result in a
   {NOT ANY} <mp-filter> or invalid <mp-peering> depending on implicit
   or explicit definitions of the address family in the set. In the
   latter case an error is returned. {NOT ANY} <mp-filter> may issue a
   warning.

7) related to point 4), it may not be apparent what's the intent of the
specification, unless done explicitly; for example:

   Conflicts with explicit or implicit declarations are resolved at
   runtime, that is during evaluation of a policy expression. For
   example, when evaluating the following import policy:
                                                                                                       
   aut-num: AS2
   mp-import: afi ipv6 from AS1 accept {193.0.0.0/22}
                                                                                                       
   the mp-filter should be evaluated as {NOT ANY}.

==> what if the mp-import would be "afi ipv6 from AS1 accept {0/0}" ?
Note that that's very valid for IPv6 too, except perhaps due to the way it's
written (should be {::/0}).  I.e., I think it's very important to specify
the grammar for properly so that the IPv4 and IPv6 addresses can be
distinguished properly in all cases.

8) related to point 5), it is not clear whether the document is intended to
be include conclusive lists of class attributes or just modified ones; for
example:
 
 3. New route6 Class
   member-of     list of <route-set-name>          optional, multi-valued
    aggr-bndry    <as-expression>                   optional, single-valued
   aggr-mtd      inbound or outbound               optional, single-valued
                 [<as-expression>]
    mnt-lower     list of <mntner-name>             optional, multi-valued
 
==> note that there are multiple attributes which do not seem to be referred
to in this document.  Is the list in the document intended as a conclusive
list of attributes or just examples?  Based on that, one may have to decide
whether to remove non-modified ones, or whether to ensure that everything is
always present [where's route-set-name or as-expression, for example?] 
(and possibly separate new and classic attributes).

==> similar in section 5, at least.

9) there seem to be some mismatches or missing specification; for example,
in section 4.2, mp-members: refers to "ipv6-address-prefix-range" and the
like, but the only similar thing in the document so far as been
"<ipv6-address-prefix>":

   mp-members  list of (<ipv4-address-prefix-range>  optional, multi-valued
               or <ipv6-address-prefix-range>
               or <route-set-name>
               or <route-set-name><range-operator>)

and:

   In RPSLng, these attributes are extended to the route6 and inet6num
   (described below) classes.  Further, the syntax of the existing
   mnt-routes attribute is modified to allow the optional specification
   of IPv6 prefix range lists when present in inet6num, route6, and
   aut-num class objects.

==> it seems the document may be trying to take too many shortcuts by
leaving the values undefined and to be intuitively filled in by the
implementors.

10) remote-endpoint-address specifies some some encapsulations:

   <remote-endpoint-address> indicates the IPv4 or IPv6 address of the
   remote endpoint of the tunnel. The address family must match that of
   the local endpoint. <encapsulation> denotes the encapsulation used in
   the tunnel and is one of {GRE,IPv6inIPv4,IPinIP,DVMRP}.  Routing
   policies for these routers should be described in the appropriate
   classes (eg. aut-num).

==> I believe DVMRP is probably very much obsolete in this interdomain,
RPSLng context and could be removed.

==> similarly, I do not see the use of IPv6inIPv4.  Doesn't IPinIP already
cover that, *assuming* that one looks at the <ipvX-address> and
<endpont-address> to figure out what it is.  Including both in here seems
redundant to me; but if that's the path, also include IPv6inIPv6 and
IPv4inIPv6, please!

11) split the references to normative and informative; the first two are
probably normative, and the last one informative.


editorial
---------

==> the document requires Table of Contents, as it's more than 15 pages
long.

                                 RPSLng
                       draft-blunk-rpslng-01.txt

==> spell out RPSLng in the title.

Abstract
                                                                                                       
   This memo presents a new set of simple extensions to the RPSL
   language enabling the language to document routing policies for the
   IPv6 and multicast address families currently used in the Internet.

==> similarly, spell out RPSL here.

Blunk, et al.           Expires January 23, 2004                [Page 1]
                                                                                                       
Internet-Draft                   RPSLng                        July 2003

==> I note that the document does not have page breaks (^L) , so it's more
difficult to read and does not print correctly.

   This document proposes to extend RPSL according to the following
   goals and requirements:
                                                                                                       
      Provide RPSL extensibility in the dimension of address families.
      Specifically, to allow users to document routing policy for IPv6
      and multicast.

==> add bullets, dashes, or whatever to the list of four goals/requirements.

      Clarity and non-ambiguity: RPSL information is used by humans in
      addition to software tools.

==> s/Clarity/Maintain clarity/

   Address Family Identifier, <afi>, is a RPSL list of address families
 
==> s/a RPSL/an RPSL/ (everywhere where applicable) ?

   mp-import ::=
          [protocol <protocol1>] [into <protocol2>] <import-expression>

==> these should probably be protocol-1 and protocol-2, to be in line with
the rest of the document conventions?

   The <mp-filter> expression is an extension of the RPSL <filter>
   expression [section 5.4 of RFC 2622 [1]]

s/[section 5.4 of RFC 2622 [1]]/(section 5.4 of RFC 2622 [1])/ (similar in a
few other places)

   mp-import: afi ipv6.unicast,ipv4 from AS1 action pref = 1; accept as-foo
               except { afi ipv6.unicast,ipv4
               from AS2 action pref = 2; accept AS226
                  except { afi ipv6.unicast
                  from AS3 action pref = 3; accept {3FFE:FFFF::/35}
                         }
                       }

==> should probably use a some more bogus AS number in the example
==> should probably use the /32 prefix length in the example, the same in
some exampler later on.

   Conflicts with explicit or implicit declarations are resolved at
   runtime, that is during evaluation of a policy expression. For
   example, when evaluating the following import policy:

==> s/evaluation/the evaluation/
==> s/that is/that is,/

   to a particular address family using the traditional filtering
   mechanism in use in IRR systems today.

==> spell out IRR.

  mp-peer    <protocol> <ipv4_address> <options> or    optional,
              <protocol> <ipv6_address> <options> or    multi-valued
 
==> in here, and many other places, one uses "ipv4_address" and the like. 
Note tha lower dash, not dash in the middle; in many other places it's
"ipv4-address" and the like.  Pick one approach and stick to it, please :-)

In the aut-num class,
   the IPv6 prefix ranges may be mixed with IPv4 prefix ranges.  They
   keyword "ANY" is also allowed which means all more specifics.  The
   default when no additional set items are specified is "ANY".

==> s/They/The/.
==> s/all more specifics/any route/?  (why would keyword "ANY" refer to more
specifics only?  that would be highly confusing)

   The <country-code> must be a valid two-letter ISO 3166 country code
   identifier.  <netname> is a symbolic name for the specified IPv6
   address space.

==> the country code specification is, at least, outside of the scope of
this document, I guess :-)


-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings