| Names and Identifiers Program | B. Trammell |
| Internet-Draft | ETH Zurich |
| Intended status: Informational | February 18, 2016 |
| Expires: August 21, 2016 |
Properties of an Ideal Naming Service
draft-trammell-inip-pins-00
This document specifies a set of necessary functions and desirable properties of an ideal system for resolving names to addresses and associated information for establishing communication associations in the Internet. For each property, it briefly explains the rationale behind it, and how the property is or could be met with the present Domain Name System. It is intended to start a discussion within the IAB’s Names and Identifiers program about gaps between the present reality of DNS and the naming service the Internet needs by returning to first principles.
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The Internet’s Domain Name System (DNS) [RFC1035] is an excellent illustration of the advantages of the decentralized architecture that have made the Internet able to scale to its present size. However, the choices made in the evolution of the DNS since its initial design are only one path through the design space of Internet-scale naming services. Many other naming services have been proposed, though none has been remotely as successful for general- purpose use in the Internet.
This document returns to first principles, to determine the dimensions of the design space of desirable properties of an Internet-scale naming service. It is a work in progress, intended to start a discussion within the IAB’s Names and Identifiers program about gaps between the present reality of DNS and the naming service the Internet needs.
Section 3 and Section 4 define the set of operations a naming service should provide for queriers and authorities, Section 5 defines a set of desirable properties of the provision of this service, and Section 6 examines implications of these properties.
The following capitalized terms are defined and used in this document:
[EDITOR’S NOTE: need to make a terminology unification pass]
At its core, a naming service must provide a few basic functions for queriers, associating a Subject of a query with information about that subject. The information available from a naming service is that which is necessary for a querier to establish a connection with some other entity in the Internet, given a name identifying it.
Given a Subject name, the naming service returns a set of addresses associated with that name, if such an association exists, where the association is determined by the authority for that name. Names may be associated with addresses in one or more address families (e.g. IP version 4, IP version 6). A querier may specify which address families it is interested in receiving addresses for, and the naming system treats all address families equally.
[EDITOR’S NOTE: DNS does this for the Internet via IN A and IN AAAA records.]
Given an Subject address, the naming service returns a set of names associated with that address, if such an association exists, where the association is determined by the authority for that address.
[EDITOR’S NOTE: DNS does this for the Internet with IN PTR records within the in-addr.arpa. and ip6.arpa. zones. Note the limitation of delegation on octet (IPv4) and nibble (IPv6) boundaries. Cite workarounds.]
Given a Subject name, the naming service returns a set of object names associated with that name, if such an association exists, where the association is determined by the authority for the subject name.
[EDITOR’S NOTE: DNS does this via IN CNAME, but doesn’t handle the set case, and there are restrictions on the use of IN CNAME (with respect to NS and MX records, but not SRV?)].
Given a Subject name, the naming service returns other auxiliary information associated with that name that is useful for establishing communication over the Internet with the entities associated with that name.
[EDITOR’S NOTE: Most other RRTYPEs implement this pattern.]
As a name might be associated with more than one address, auxiliary information as above may be associated with a name/address pair, as opposed to just with a name.
[EDITOR’S NOTE: DNS doesn’t do this, does it?]
The query interface is not the only interface to the naming service: the interface a naming service presents to an Authority allows updates to the set of Associations and Delegations in that Authority’s namespace. Updates consist of additions of, changes to, and deletions of Associations and Delegations. In the present DNS, this interface consists of the publication of a new zone file with an incremented version number, but other authority interfaces are possible.
The following properties are desirable in a naming service providing the functions in Section 3 and Section 4.
Every Association among names, addresses, and auxiliary data is subject to some Authority: an entity which has the right to determine which Associations and Subjects exist in its namespace. The following are properties of Authorities in our ideal naming service:
An Authority can delegate some part of its namespace to some other subordinate Authority. This property allows the naming service to scale to the size of the Internet, and leads to a tree-structured namespace, where each Delegation is itself identified with a Subject at a given level in the namespace.
For a given Subject, there is a single Authority that has the right to determine the Associations and/or Delegations for that subject. The unitary authority for the root of the namespace tree may be special, though; see Section 5.1.4.
[EDITOR’S NOTE: The unitary authority for a given name in the DNS is its registry. The existence of registrars complicates this somewhat; see below.]
A querier can determine the identity of the Authority for a given Association. An Authority cannot delegate its rights or responsibilities with respect to a subject without that Delegation being exposed to the querier.
[EDITOR’S NOTE: It is very hard to enforce a restriction about delegations on the side (i.e. “I make this assertion ‘cause somebody paid me to”). One could implement this in the current DNS by having the recursive also do a WHOIS, making information about the registrar available for local policy decisions.]
Authority at the top level of the namespace tree is delegated according to a process such that there is universal agreement throughout the Internet as to the subordinates of those Delegations.
[EDITOR’S NOTE: Today, this is the root zone. But note that this property does not necessarily imply a single authority at the root as with the present arrangement, only that the process by which the root is changed and operated leads to a universally consistent result.]
A querier must be able to verify that the answers that it gets from the naming service are authentic.
Given a Delegation from a superordinate to a subordinate Authority, a querier must be able to verify that the superordinate Authority authorized the Delegation.
[EDITOR’S NOTE: DNSSEC does this.]
The authenticity of every answer must be verifiable by the querier, and the querier must be able to confirm that the Association returned in the answer is correct according to the Authority for the Subject of the query.
[EDITOR’S NOTE: DNSSEC does this.]
Some queries will yield no answer, because no such Association exists. In this case, the querier must be able to confirm that the Authority for the Subject of the query asserts this lack of Association.
[EDITOR’S NOTE: DNSSEC does this depending on how well you’ve set it up?]
Consistency in a naming service is important. The naming service should provide the most globally consistent view possible of the set of associations that exist at a given point in time, within the limits of latency and bandwidth tradeoffs.
When an Authority makes changes to an Association, every query for a given Subject must give either the new valid result or a previously valid result, with known and predictable bounds on “how previously”. Given that additions of, changes to, and deletions of associations may have different operational causes, different bounds may apply to different operations.
[EDITOR’S NOTE: This is the point of TTL in DNS. Additions faster than changes and deletions, which is probably the opposite of what you really want if you want name-service-based revocation of things.]
Some techniques require giving different answers to different queries, even in the absence of changes: the stable state of the namespace is not globally consistent. This inconsistency should be explicit: a querier should be able to know that an answer might be dependent on its identity, network location, or other factors.
Note that explicit inconsistency based on client identity or network address may increase query linkability (see Section 5.4.4).
[EDITOR’S NOTE: DNS doesn’t do this. [I-D.ietf-dnsop-edns-client-subnet] addresses making the query from the recursive explicit that it would like an appropriate answer
[EDITOR’S NOTE: note that these have to do with name service dynamics, and that explicit tradeoffs here are possible and interesting.]
The naming service as a while must be resilient to failures of individual nodes providing the naming service, as well as to failures of links among them. Intentional prevention of successful, authenticated query by an adversary should be as hard as practical.
[EDITOR’S NOTE: DNS aims to provide this through explicit secondaries and XFER, as well as through operational practice: e.g. through ease of anycasting UDP services.]
The time for the entire process of looking up a name and other necessary associated data from the point of view of the querier, amortized over all queries for all connections, should not significantly impact connection setup or resumption latency.
[EDITOR’S NOTE: DNS aims to provide this through being small and simple, and through the use of caching.]
The bandwidth cost for looking up a name and other associated data necessary for establishing communication with a given Subject, from the point of view of the querier, amortized over all queries for all connections, should significantly impact total bandwidth demand for an application.
[EDITOR’S NOTE: What we mean here is that approaches that flood all name mapping updates to the entire Internet are probably not acceptable. Cite work on DNS traffic load to show that DNS has this property?]
It should be costly for an adversary to monitor the infrastructure in order to link specific queries to specific queriers.
[EDITOR’S NOTE: DPRIVE is working toward this.]
A querier should be able to indicate the desire for a benefit with respect to one performance property by accepting a tradeoff in another, including:
[EDITOR’S NOTE: DNS doesn’t do this, and can’t really: TTL gives you a tradeoff knob but it’s in the hands of the authority]
We have shown that most of the properties of our ideal name service are met, or could be met, by the present DNS protocol or extensions thereto. [EDITOR’S NOTE: not yet, not really.] We note that there are further possibilities for the future evolution of naming services meeting these properties.
[EDITOR’S NOTE: there are probably more than just this one, but this is the important one.]
Any system which can provide the authenticity properties in Section 5.2 is freed from one of the design characteristics of the present domain name system: the requirement to bind a zone of authority to a specific set of authoritative servers. Since the authenticity of delegation must be a protected by a chain of signatures back to the root of authority, the location within the infrastructure where an authoritative mapping “lives” is no longer bound to a specific name server. While the present design of DNS does have its own scalability advantages, this implication allows a much larger design space to be explored for future name service work, as a Delegation need not always be implemented via redirection to another name server.
This document has no actions for IANA
[EDITOR’S NOTE: todo]
This document is an output of a design work on naming services at the Network Security Group at ETH Zurich. Thanks to the group, including Daniele Asoni and Stephen Shirley, for discussions leading to this document. Thanks as well to Andrew Sullivan and Suzanne Woolf for input and feedback.
| [I-D.ietf-dnsop-edns-client-subnet] | Contavalli, C., Gaast, W., tale, t. and W. Kumari, "Client Subnet in DNS Queries", Internet-Draft draft-ietf-dnsop-edns-client-subnet-06, December 2015. |
| [RFC1035] | Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987. |