[RRG] Generic requirements on mapping mechanisms

[Olivier Bonaventure <Olivier.Bonaventure@uclouvain.be>]

Hello,


Today, there is a generic discussion on mapping during the RRG meeting. 
Unfortunately, I'm not in Philapdelphia, but I would like to list a few 
requirements that I consider important. These requirements are 
independant of the particular mapping mechanism used.

Comments are welcome

Olivier

---------------------------------------------------------

The mapping mechanism will be used to map a (set of) identifier(s) on a 
set of locators, formally

{EIDs} -> {Loc1, Loc2, Loc3}

From a generic/abstract viewpoint, I think that the following 
requirements are important :

1. Locators and EIDs

Locators and EIDs will be allocated by a central authority, such as IANA 
or deleguates like RIPE, ARIN, APNIC, ...  This central authority is 
important to ensure uniqueness of the locators and of the EIDs.

I assume that locators will be IPv4 or IPv6 addresses. EIDs could be 
something else.


2. For scalability reasons, the mapping mechanism must allow to map a 
(preferably large) set of identifiers on a set of locators.

This implies that EIDs will need to be allocated in contiguous blocks 
and not individually.  The size of the EID set will affect the 
scalability of the system. Using large EID sets will make the mechanism 
more scalable. Thus, the central authorities should allocate large EID 
blocks.

To avoid the scalability problems that we have today with interdomain 
routing, the owner of the EIDs should support the cost of using small 
EID sets. A possible way to ensure this would be to force the an owner 
of an EID block to always reply with a mapping that is valid for the 
entire block and optionnally add mappings for subsets of the EID block, 
e.g. for traffic engineering purposes.

3. There should be a way to secure the mapping replies

It should be possible for an entity that requests a mapping to verify 
the validity of the reply. Some entities may assume that any received 
reply is by definition valid, but such a behaviour raises serious 
security issues. The mapping mechanism should allow an entity to verify 
that a reply is correct and valid. This could be a cryptographic 
verification based on signatures or an online verification where a 
server responsible for the EID block is contacted to validate a mapping.

4. A mapping will have a limited lifetime.

No mapping can be permament and the mapping reply should contain the 
lifetime of this mapping. This is similar to the TTL in the DNS. A long 
lifetime will favor scalability while a shorter lifetime will ease 
traffic engineering by allowing a site to update regularly its map 
replies. As for requirement 2, the cost of using short lifetimes should 
be supported by the site that is using those short lifetimes, not by the 
entire mapping system.



--
http://inl.info.ucl.ac.be , Universite catholique de Louvain, Belgium

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