Dynamic Hostname Exchange Mechanism for OSPF
draft-ietf-ospf-dynamic-hostname-05

The OPS-DIR review by David Kessens raised a number of issues that make this document problematic although not enough to block it at this phase: 

1. The authors chose to overload the protocol with an option for a problem that looks more like a management problem and is solved in real life by good network management techniques. The arguments about scaling issues for a stored mapping table do not seem credible. One can expect that routers in a reasonable sized network are already configured by use of a central database and configuring an extra table should not be a problem at all. Furthermore, there are security issues with the choosen approach that a configured table doesn't have and it seems that it might be easier to avoid name conflicts with a centrally configured table. The security concerns are apprpiately identified in the document, ans it seems safer to use a configured table which does not have such problems. 

2. There are issues with the interpretation of what an ID to hostname mapping actually means, and what it should and should not be used for. The term hostname is used but there are only hints that an OSPF hostname might be the same as what one stores in the DNS as a hostname for a particular router. Eg. is the hostname just an easy human readible name or is it supposed to be the same as a real hostname that also maps to an IP address used by the router.

INTRODUCTION, paragraph 2:
> Dynamic Hostname Exchange Mechanism for OSPF

  The names exchanged in this option name *routers*, not hosts. The
  terminology is hence pretty confusing.

Section 2., paragraph 5:
>    This specification provides these semantics
>    and mapping mechanisms for OSPFv2 and OSPFv3, leveraging the OSPF
>    Router Information (RI) LSA ([RFC4970]).

  Please expand acronyms on first use (LSA, etc.)


Section 3.1., paragraph 6:
>    The use of FQDN or a subset of
>    it is strongly recommended.

  s/recommended/RECOMMENDED/


Section 8.2., paragraph 4:
>    [RFC2763]  Shen, N. and H. Smit, "Dynamic Hostname Exchange Mechanism
>               for IS-IS", RFC 2763, February 2000.

  Obsolete informational reference (is this intentional?): RFC 2763
  (Obsoleted by RFC 5301)

I agree with the comment that this draft should be more clear in the difference between a hostname and a display name for a router.  Using the terms 'host' and "host name" imply that the node is reachable at that host name.  OTOH if this was just a display name, then presumably RFC3490 wouldn't apply.

Is there any impact from name collisions if two routers use the same Dynamic Hostname.  I don't think there is other than potential confusion in reading and using the mapping information.  For completeness, it might be useful to add a couple of sentences explaining that name conflicts aren't crucial and, therefore, there is no conflict detection or resolution in the protocol.

Editorial suggestion: expand "FQDN" on first use in section 3.1?  I don't understand this sentence in section 3.1:

   The content of this value is a domain
   name, see [RFC2181].

"this value" == value field in the Dynamic Hostname TLV?  What does it mean for the dynamic hostname to be a "domain name"?  Can't it also be an arbitrary identifier chosen by the OSPF admin or does it somehow have to relate to a name from the DNS?

(moved to a comment after having it pointed out that the text limits the field to 255 octets - potential exhaustion still exists, but is harder. Missing that limit in the implementation of a sender could still lead to problems).

I think a little more advice in the Security Considerations section on protection from accidental misconfiguration causing problems might be in order.

This mechanism causes routers to keep new state (adding domain names to a table). The mechanism can provide names that are large (effectively bounded by the size of an OSPF message). It's not hard to imagine someone fat-fingering a configuration file (missing a quote or the equivalent) and ending up with a very large "domain name".