Subject: [dhcwg] IESG Discuss on draft-ietf-dhc-dna-ipv4-12.txt

From: Margaret Wasserman <[email-masked]>
Date: Tue, 21 Jun 2005 11:28:52 -0400

Hi Bernard,

The DNA in IPv4 draft (draft-ietf-dhc-dna-ipv4-12.txt) is up for IESG 
review at this Thursday's IESG telechat.

Sam Hartman reviewed this document and raised the following issue:

2005-06-21] Section 2.1 of the document discusses implementations of 
DNAV4 using
snooping versions of OSPF and RIP to understand what prefixes are on a
subnet without fully participating in a routing protocol.  While this
practice is encouraged by this specification, no reference to how to
do it is provided.  If such a reference exists it needs to be
included.  If no such reference exists, please confirm that sufficient
detail is provided that implementations are unlikely to break the
routing infrastructure by misimplementing this feature.

Sam and I discussed this issue, and he asked whether this issue had 
been discussed in the WG.  I don't remember that it has, so I 
encouraged him to hold a discuss while we discuss this...

Currently section 2.1 says:

    Similarly hosts that support routing protocols such as RIP and OSPF
    can use these protocols to determine the prefix(es) available on a
    link and the default gateway(s) that serve those prefixes.  Full
    support is not required to glean this information.  A host that
    passively observes routing protocol traffic may deduce this
    information without supporting a fully conformant routing protocol
    implementation.

I know that snooping versions of RIP and OSPF are widely implemented 
and I (think I) know what subsets are needed for this "passive 
observer" functionality.  This is trivial in RIP (you can literally 
act as a passive observer on the RIP port), but a bit more 
complicated in OSPF, where (if I understand correctly) you will have 
to associate with neighboring OSPF routers to receive routing 
information, while not publishing any routes yourself.  I don't think 
that you can snoop OSPF information while being entirely passive, can 
you?

Anyway, if there is a reference for how to snoop using OSPF or RIP, 
that would be best.  But, if there is not a reference, do you think 
that we need to say a bit more in section 2.1 about what subsets of 
RIP and/or OSPF are needed to do this?

As a minor editorial side note, you should probably include 
references for RIP and OSPF.

Margaret

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