Subject: [Rserpool] rserpool comparison: resolver problems

From: Coene Lode <[email-masked]>
Date: Wed, 2 May 2001 17:52:59 +0200

In paragraph 2.2.3.1 Host resolver Problems, the problem is (to my opinion)
a little bit bigger than just making all hosts use full resolvers. 

The DNS is based on a recursive search, that would mean that even a Host
full resolver would go to another full resolver  where 2 possibilities
exits: either the mapping name-IP address is found(in database or in its
cache(provided TTL didn't time out yet) or it has to do another recursive
resolve of the name, staring from that intermediate resolver, till finally
there is a cache hit in one of the intermediate resolvers or it is resolved
by its root resolver(or home DNS server). 

This process of recursion means that there is no end-to end communication
between the host and its server where the name-to-IP maaping resides. That
also means that a lot of timers are running in intermediate systems(not
exactly a receipt for success). And that any updating of the transient
status of the pool element or of the pool may need to be propagated through
the DNS: (which is already noted in the same paragraph with the "load on
third-party servers")

However up till now, "myth" has it that the DNS is a hierarchical
distributed system. 
There are root servers and from that root server a hierarchy goes down("be"
is not a root server in its own right, it is dependant on one or more of the
top root servers(I think there 14 at the last count, give or take one)).
Recursion is a necessity in such a system. 

Now as far as I understand, direct communication between the PE and the
ENHRP is a must. Why it keeps the register and certainly the deregister and
update procedures to a minimum(a less stringent requirement could be: with
as few as recursion(=intermediate TTL's) possible). Thus DNS would only fit
in the Rserpool picture if:
- recursion for resolving the name is minimal-> no big hierarchy
- keep caching to a absolute minimum(as otherwise distribution of the status
of the PE is needed)
No big hierarchy as a requirement collides with the requirement for
minimizing caching, because DNS need to cache a lot in order to reduce its
dependance on hierarchy.

So as far as I am concerned, DNS in its present form will have a hell of a
problem trying to solve our "Relialable server pool" problems.

yours sincerly,
Lode Coene

(still trying to find out which spell the DNS casted on most IETF'ers so
that they actuallly like the DNS)

Siemens Atea ICN D CS D
Software Development 
Atealaan 34     
B-2200    Herentals    Belgium         
Tel +32-14-25-2081   /  Fax +32-14-25-3212
E-mail:   [email-masked]

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---

From: [email-masked]
Date: Thu, 10 May 2001 14:42:34 +0300

Hi Lode,

> In paragraph 2.2.3.1 Host resolver Problems, the problem is 
> (to my opinion) a little bit bigger than just making all hosts 
> use full resolvers. 
> 
> The DNS is based on a recursive search, 

I agree that DNS recusion creates problems for what we
would like to do, so I'll try to add some text on this.

Any other comments?

John