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Letting DNS Loose

Most folks tend to think of the DNS as a way to map ASCII host names to IP addresses, perhaps www.nominum.com to 10.0.01 or some such.

I believe that when Vint talks about “escaping the bonds of DNS”, [see BBC’s report and Doug Mehus’ CircleID report] he’s really talking about letting it loose rather than replacing it.

In the case of ENUM and NAPTR, all we are doing is saying that “domain names can carry phone numbers, so why not let them”. NAPTR is a DNS data type, so we aren’t replacing DNS with NAPTR, that would make no sense. In fact the whole ENUM scheme is built out of classical DNS technology, and NAPTR is really just the latest data type to be added to the DNS (there’s 40 or so). NAPTR is also just an extension of SRV, which was an extension of MX, which are DNS data types that Active Directory uses to start itself and the Internet uses to route each piece of mail.

RFID tags, UPC codes, International characters in email addresses and host names, and a variety of other identifiers could all go into DNS, and folks have occasionally proposed doing just that. It’s really just a question of figuring out how to use the DNS—it’s ready to carry arbitrary identifiers. And by the way, this isn’t a new idea, see RFC 1101 for proof, although even earlier I designed the DNS in the early 1980s to allow it to be so, but it seemed too far fetched to document for a while.

But don’t think that I’m claiming to have solved the whole problem. What I certainly didn’t anticipate was the political, legal, and commercial fight that would come with it. These squabbles behind ENUM and RFID use of DNS are really the problem, not the technology, although there may be ways to help with more technology. I was in Geneva for a WSIS meeting of CTOs, and was surprised that the various organizations (ITU, ICANN, ISOC) haven’t figured out that they need each other to make this technology work, rather than asserting ownership.

While it is inevitable that the DNS gets replaced, I think there could be far more usage and opportunity if the political aspects were addressed coherently, and if the technology types just let experimentation happen, rather than trying to make rules about how the DNS is used.

By Paul Mockapetris, Director at Farsight Security

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Comments

Brad Neuberg  –  Jan 7, 2004 8:31 AM

Paul, do you think peer-to-peer naming systems, such as distributing signed DNS records using a distributed hashtable (DHT), will ever work?  The Chord folks have done a great deal of work on this topic.

Brad Neuberg  –  Jan 7, 2004 8:37 AM

By the way, I should add that these signed records could establish a binding between any arbitrary string, such as domain name like “www.cnn.com” or a phone number like “510-235-2234”, and any arbitrary address/endpoint, such as an IP address or possibly a public key.

pbhj  –  Jan 7, 2004 10:27 AM

Sorry to be a pain, but: is 10.0.01 an IP address, I thought that current IP had 4 numbers. Also, I thought that 10.0.0.1 (which I presume is intended) was reserved for private addressing (local networks, etc.) and so couldn’t point to an internet address (as in your example).

I’m probably wrong, which is worrying me as I thought I knew a little about this, you are after all the one writing the articles!

How is the preceding zero formatted to hex?

Paul Mockapetris  –  Jan 7, 2004 6:43 PM

I have heard of the Chord stuff, but haven’t had time to look into it - sounds like the kind of thing I’d like, but the IETF might frown on.

If you have a good reference, I’d appreciate it!

Sorry, I did indeed mean “10.0.0.1”, which is a private address, but I’d disagree that it is inappropriate as an example, since I believe that most of the DNS is behind firewalls these days.

Brad Neuberg  –  Jan 7, 2004 11:50 PM

This comment is in two parts, as there is a 2500 character limit on comments.

Hi Paul; thanks for responding.  There is a WikiWiki with a good introductory page on distributed hash tables (DHTs) at http://www.infoanarchy.org/wiki/wiki.pl?Distributed_Hash_Table
This page gives an overview and then provides further references to research projects that have implemented different kinds of DHTs, such as Chord, Pastry, Kademlia, etc.

As an example of how powerful DHTs can be as a generic naming substrate, see the open-source project named The Circle at http://thecircle.org.au/ . This application uses a DHT for several uses: to share files, to send instant messages and IRC-style chatting, and for putting together a personalized news service.

Here are some other things to see.  I run a project named P2P Sockets that includes a simple, non-secure distributed DNS.  While it doesn’t currently use a DHT (it uses another open-source project named JXTA as its P2P substrate), I plan on transitioning to a DHT in the near-future.  See it at http://p2psockets.jxta.org

The original paper concerning storing DNSSec records in Chord is available at http://www.pdos.lcs.mit.edu/chord/papers/ddns.pdf

Brad Neuberg  –  Jan 7, 2004 11:54 PM

Here is the second part to my previous comment; a third part follows.

There has been a great deal of activity both at the grass-roots, open source level and at the academic level in these systems the last few years.  While I don’t believe technical solutions can always solve social and political issues, I do believe that an alternative technical approach to the DNS can help ameliorate these problems.  P2P/DHT-based approaches might point the way to such a solution.

There are several significant research issues that must be resolved before this is possible, though.  These are latency, DoS-style attacks on such a substrate, reliability of the naming records, and how to achieve secure name bindings while also ensuring human-friendly names.

The first issue, latency, seems to be disappearing as newer DHT algorithms are developed.  The second issue is DoS-style attacks.  If we go with a First Come/First Served (FCFS) system for handing out naming bindings, which removes DNS-style registrars from the loop, then assailants can programatically exhaust the namespace by simply grabbing names.  While a FCFS system is attractive because it removes the need to have gatekeepers handing out names, it does open this problem.  One way to solve this is to retain DNS registrars who sign but do not store DNS records; DNS records are stored in the P2P substrate using the DNSSec standard.  If a DNS registrar detects that another peer is attempting to DoS it, it can cut it off.  Of course, this doesn’t protect against distributed DoS attacks, where many peers in the network might be compromised and requesting names.  We might have to introduce some “friction” into the system, such as money or hashcash (i.e. clients have to provide a proof that they ran some computationally-heavy algorithm).

The third issue is reliability of the naming records.  Chord has its own solution to this problem, as does the OceanStore team at http://oceanstore.cs.berkeley.edu/  This is a difficult problem without an elegant solution at this point.  A good paper comparing some P2P replication schemes is at http://oceanstore.cs.berkeley.edu/publications/papers/pdf/erasure_iptps.pdf and is named “Erasure Coding vs. Replication: A Quantitative Comparison”.

Brad Neuberg  –  Jan 7, 2004 11:56 PM

Here is the third part of the comment.


The final issue is to achieve secure name bindings while also ensuring human-friendly names.  The problem with achieving these two goals in a distributed, peer-to-peer system is succinctly explained in a position paper by an open-source programmer nicknamed Zooko.  This paper is titled “Names: Decentralized, Secure, Human-Meaningful: Choose Two” and is available at http://zooko.com/distnames.html . Some P2P projects have decided to simply abandon human-friendly names, instead going with secure pointers instead.  This is the approach the Freenet project has taken (http://freenet.sourceforge.net/). 

Unfortunately, these secure pointers are incomprehensible to ordinary computer users.  I think there is value in a global namespace that is human-friendly, such as the current DNS.  While I believe that Zooko is correct in identifying that you can’t achieve complete decentralization, complete security, and human-friendly names at the same time, I do feel that it is possible to have both security and human-friendly names with a partially decentralized system.  The question then becomes how much can we decentralize while still retaining the other two aspects.  Perhaps we will be able to decentralize the portions of DNS that are capital intensive, such as storing records or acting as root servers.

These ideas fascinates me, so if you would like to continue this discussion feel free to email me at .(JavaScript must be enabled to view this email address)

Hope all is well,
  Brad Neuberg
  .(JavaScript must be enabled to view this email address)
  The P2P Sockets Project - http://p2psockets.jxta.org
  Paper Airplane - http://www.paperairplane.us

Paul Mockapetris  –  Jan 8, 2004 5:20 PM

The process of others adding to or building on top of the original DNS protocol has actually been going on since the early 1980s.

My point was all of the people working on these ideas today aren’t working together as well as they might be.

As for who invented the DNS protocol, I’ll let the RFC record speak for itself.  Anybody who reads them will recognize Francis Bacon’s hand.

Brad Neuberg  –  Jan 8, 2004 9:36 PM

Paul, any comments on the DHT links I posted?

Brad

Mike O'Donnell  –  Jan 12, 2004 2:39 AM

From Brad Neuberg’s comment:

“While I believe that Zooko is correct in identifying that you can’t achieve complete decentralization, complete security, and human-friendly names at the same time, I do feel that it is possible to have both security and human-friendly names with a partially decentralized system. The question then becomes how much can we decentralize while still retaining the other two aspects. Perhaps we will be able to decentralize the portions of DNS that are capital intensive, such as storing records or acting as root servers.”

It makes a lot of sense to have a 2-stage system.

1. A mapping of completely secure, completely decentralized, but meaningless handles to IP addresses.

2. A separate mapping of meaningful names to handles.

Both stages can be implemented with DNS. The 2-stage modular design allows flexible experimentation in the mapping of meaningful names to accommodate different tradeoffs with security and decentralization.

Mike O’DOnnell

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