RE: Handling of External Host Objects: Single vs. Multi Copy Solu tions (was: in the context of domain transfer)

["Gould, James" <JGould@verisign.com>]

Hong,

I understand the motivation for supporting multi-copy external hosts.  Let
me address each one of your concerns:

1) Waste of storage space - An external host is light weight and supporting
a set of external hosts per registrar has not been an area of concern in the
registries that I've worked on.  

2) management on a per client basis - Supporting multi-copy external hosts
is extra effort when you have to consider host name changes and transfers,
but it is technically feasible.

3) keeping the state consistent - I don't understand the issue with
consistency, since the information that is presented should be based on the
context of the current EPP session.  If registrar A starts an EPP session,
than any host info commands should respond with registrar A's external host
information.  If registrar A does not have the external host, than the
response should be 2303 "Object does not exist".  It is up to you how you
want to present the information in whois.  You could allow for the passing
of the registrar id, provide back a list of hosts including the registrar
id, etc..    

4) complexity of transfers - Supporting multi-copy external hosts does
represent more effort when it comes to implementing transfer, but it is
technically feasible.  The ability to rename a host which automatically
changes the domain references is an important requirement/feature.  I don't
know of any requests for partial renames.  

I don't believe the only advantage is to "facilitate the massive renaming of
external nameservers", since the support for reference based renaming is a
core requirement with a single copy or multi-copy approach.   I believe that
the single copy approach was a significant complaint with RRP and providing
support for multi-copy external hosts was hammered out a long while back.  

After implementing multi-copy external hosts along with transfer, I do
appreciate the extra effort involved, but I believe this is an
implementation issue and not a protocol issue.  

Jim 

> facilitate the
> massive renaming of external nameservers
> ----------
> From: 	Liu, Hong
> Sent: 	Wednesday, October 30, 2002 2:23 PM
> To: 	'ietf-provreg@cafax.se'
> Subject: 	RE: Handling of External Host Objects: Single vs. Multi Copy
> Solu tions (was: in the context of domain transfer)
> 
> Jim, Asbjorn,
> 
> I would like to focus this thread on the advantages and disadvantages of
> Single vs. Multi- copy solutions for external host objects.
> 
> To recap the discussion on the list, the motivation of dealing with
> external
> host objects on a per-client basis is the ownership problem. Since
> external
> hosts are outside of the registry namespace, no one, including the
> registry
> itself, has exact knowledge about the external hosts. In a word, nobody
> actually "owns" an external host as far as the registry is concerned.  
> 
> The only use of an external host object in EPP is as a nameserver for
> domains of the registry. It merely serves as a pointer to an external
> entity. External host objects are not transferred as a result of
> associated
> domain transfer.
> 
> Before epp domain mapping -04, external host objects are created by
> clients
> on a FCFS basis. There is a single-copy of an external host in the
> registry.
> Whoever registrar first created an external host becomes the sponsoring
> registrar of that object. As such, no other registrars will be able to do
> much on the external host object except using it as a nameserver. There
> are
> various headaches stem out of this client-centric single-copy ownership
> model. Specifically, when the sponsoring registrar rename the external
> host
> object, all domains that use it as nameserver are changed implicitly. This
> has very undesirable effects on domains that are sponsored by other
> registrars but use the external host as a nameserver. First, these other
> registrars do not know such a change, and some domains may not want to
> change to the new nameserver. Second, once the change is discovered after
> the fact, these registrars will have to undo the change for all these
> affected domains one-by-one.  
> 
> To resolve this problem, in epp domain mapping -04, a client-centric
> multi-copy ownership model was adopted, and the model was carried over to
> the latest epp domain mapping -05. However, after careful study, we find
> the
> multi-copy ownership model only partially solves the update problem. In
> addition, it introduces a whole lot of complexity into external host
> handling, such as:
> 
> (1) Waste of storage space on the server side. Imagine that a registry has
> 100 registars, and each has a private copy of an external host. Then there
> will be 100 private copies of host objects in the registry serving as
> pointers to a single external entity. It is not uncommon in many
> registries
> other than com/net/org where the majority of the nameservers are external
> host objects.
> 
> (2) For all these private copies, the server has to specially manage them
> on
> a per-client basis, i.e., {hostname, clID} pairs. This undoubtly and
> unnessarily complicates the server software.
> 
> (3) Since each client updates its private copy individually, it is very
> difficult to keep the state of these objects consistent. Of particular
> difficulty is the presentation of such information to queries based only
> on
> hostname. 
> 
> For example, in Whois, what result will be returned for a query on an
> external object? All of the instances, none, randomly one? It is extremely
> confusing, especially when different instances have different statii, say
> one is "ok" while the other is "clientUpdateProhibited", the third is
> "linked", and the forth is without "linked" status. 
> 
> Similarly, what will be the rules for response to the <info> command from
> a
> client, only its private copy? What happen if the client does not have a
> private copy? Should the server return all, none, randomly one? Note that
> the current <info> response is not equipped with returning information for
> multiple instances.
> 
> (4) It introduces undue complexity involving domain transfer, as we have
> discussed in some details already. External hosts are not in-zone hosts,
> as
> such they should not be involved in domain transfer. With the multi-copy
> model, it requires special handling of external hosts used as nameservers,
> as side-effects of domain transfer.
> 
> Most importantly, the multi-copy model does not solve the external host
> rename problem completely. It just limits the problem from registry-wide
> to
> registrar-wide. It is true that a single rename of the private copy will
> result in all domains pointing to a different external host as a
> nameserver.
> But what happen for partial update within the same registrar? If some of
> the
> domains want to retain the old external host namesever, the registrar will
> still have to do the update one-by-one. There is no other way around. Note
> that this only covers massive renaming from the external to external case,
> for external to internal or internal to external, the registrar will still
> have to do it one-by-one if the internal host is not sponsored by the
> registrar.
> 
> So if the only advantage of the multi-copy model is to facilitate the
> massive renaming of external nameservers, then I would say that the cost
> is
> too high to warrant such convenience. On the contrary, a server-centric
> single-copy model solves the ownership problem in a much simpler and more
> effective fashion, and yet does not introduce those undue complexity
> mentioned above.
> 
> Cheers,
> 
> --Hong
> 
>