Independent Submission C. Pignataro
Request for Comments: 6593 J. Clarke
Category: Experimental G. Salgueiro
ISSN: 2070-1721 Cisco Systems
1 April 2012
Service Undiscovery Using Hide-and-Go-Seek
for the Domain Pseudonym System (DPS)
With the ubiquitous success of service discovery techniques, curious
clients are faced with an increasing overload of service instances
and options listed when they browse for services. A typical domain
may contain web servers, remote desktop servers, printers, file
servers, video content servers, automatons, Points of Presence using
artificial intelligence, etc., all advertising their presence.
Unsurprisingly, it is expected that some protocols and services will
choose the comfort of anonymity and avoid discovery.
This memo describes a new experimental protocol for this purpose
utilizing the Domain Pseudonym System (DPS), and discusses strategies
for its successful implementation and deployment.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
This document defines an Experimental Protocol for the Internet
community. This is a contribution to the RFC Series, independently
of any other RFC stream. The RFC Editor has chosen to publish this
document at its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
Copyright (c) 2012 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Procedures Using the Domain Pseudonym System . . . . . . . . . 3
2.1. Count to Live (CTL) for IPv4 and Count Limit (CL) for
IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Implicit and Explicit Hiding . . . . . . . . . . . . . . . 4
2.3. Timeout State and Finite State Machine for Misbehaving
Clients . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.4. Echo . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.5. Service-as-a-Service (SaaS) Method . . . . . . . . . . . . 5
2.6. Foobar, Mononymous, and other Disguises . . . . . . . . . . 5
2.7. Hinting . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.8. Truth or Dare as Disambiguation . . . . . . . . . . . . . . 7
3. Protocol Definition . . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Informative References . . . . . . . . . . . . . . . . . . . . 7
In today's domains, there are services that, by choice, prefer to not
be advertised and to cloak themselves with a shroud of anonymity.
However, protocols do not address the needs of these services. To
solve this, we propose a new paradigm of service hide-and-go-seek for
services that do not want to be discovered. A client may be looking
for a service, but an apathetic, playful, overwhelmed, or shy service
might prefer a hide or hint engagement, instead of directly showing
This document is unscoped, as the scoping service cannot be found.
2. Procedures Using the Domain Pseudonym System
Certain services conceal themselves with the intent of not being
found, perhaps, by clients. The client trying to find the sneaky
service is referred to as "seeker" or more precisely as "it". The
concealed service is referred to as "hider". The process of Service
Undiscovery using hide-and-go-seek is achieved using the Domain
Pseudonym System (DPS), in which a service instance can hide behind a
fictitious, fallacious, or facetious name. For example, a music
streaming service may advertise itself as a tax collection agency's
2.1. Count to Live (CTL) for IPv4 and Count Limit (CL) for IPv6
The service hide-and-go-seek process begins with a services "ready or
not" sequence whereby the "it" counts up to a default Count to Live
(CTL) or Count Limit (CL) of 50. Services that are in hiding can
change their hiding names while "it" is not looking, but when doing
so their CTL (or CL) is decremented by one. It is imperative that
"it" counts by one (count++) until reaching the CTL or CL. If "it"
attempts to skip-count, and if this is discovered, its count is reset
If a client ("it") attempts to peek into a list of services before
reaching the CTL, "it" will be placed into a "timeout" state in which
"it" is denied access to all services until the hider feels "it" has
learned its lesson. Other services may choose to mock "it" while
"it" is in "timeout".
2.2. Implicit and Explicit Hiding
Various strategies can be used by service hiders, so that "it" (the
go-seeker) does not find them. Implicit strategies are most common
yet very effective, and employ Silence-as-a-Service (SiaaS). On the
other hand, explicit strategies are best exemplified by an "I am not
here" argument. Service names such as "empty", "no%20one", "gone-
fishing", "/dev/ilinside", "/dev/ious", "out-to-lunch", "/opt/out",
"/opt/ional", "/vol/atile", and "you're-not-much-of-a-bloodhound-are-
you-Sherlock" are among the most commonly used for explicit hiding.
2.3. Timeout State and Finite State Machine for Misbehaving Clients
As discussed in Section 2.1, if "it" attempts to access a hiding
service before the CTL (or CL) has expired, "it" will be placed into
a "timeout" state and denied access to all services. When "it"
attempts to contact any IPv4-based service during this period, the
service will reply with an ICMPv4 Destination Unreachable message
type (1) and a code of "Communication Administratively Prohibited"
(13). An IPv6 service will also reply with an ICMPv6 Destination
Unreachable message type (3) and a code of "communication with
destination administratively prohibited" (1). Services will continue
to reply with such messages until such time that they feel "it" has
learned its lesson. During the "timeout" period, services may also
choose to randomly send ICMP insults to "it". ICMPv4 type 253
(reserved for experimentation [RFC4727]) is used to specify an
"Insult" class of messages, while ICMPv6 type 200 (reserved for
experimentation [RFC4443]) is used for the same purpose. Within each
type, there are three experimental codes.
LOSER (code 0): The service wishes to convey that "it" is
incapable of winning
DORK (code 1): The service wants to imply that "it" is
stupid or silly
TODAY IS SPECIAL (code 2): The service intends to respond to the
question "are you always this stupid or
is today a special occasion?"
Echo, derived from [RFC0862], can also be an effective hiding
technique. The hider simply repeats the service name that another
service instance advertises, ensuring it is in UTF-27 lowercase to
convey that it was fading out. The hider may also choose to echo the
go-seeker's request back to the go-seeker as-is.
2.5. Service-as-a-Service (SaaS) Method
This method can be used recursively (i.e., this method can be used
recursively (i.e., this method can be used recursively (i.e., this
method can be used recursively))). (See Section 2.5).
2.6. Foobar, Mononymous, and other Disguises
A common practice is for services to employ the use of mononyms. In
fact, there are documented use cases of using mononyms such as great
Brazilian athletes or famous musicians, such as Prince (or "the-
service-formally-known-as-Prince") as a service. These are
techniques allowed by the protocol definition to hide a service.
Similarly, metasyntactic service names (e.g., foo, bar, foobar, baz,
and other aliases) are among the most evolved hiding techniques.
Conversely, hypocorisms do not hide the service and typically lead to
confusion. Hiders requiring government-level security may simply
respond with "service-name-redacted", essentially presenting the go-
seeker with a black bar where the service name would be.
If a go-seeker requests a service list from a hider, the hider can
optionally respond with a GUESS reply instead of the service list.
The go-seeker will then request specific services from the hider
using HINT-REQUEST PDUs, and the hider will respond with temperature-
based HINT-REPLY PDUs to indicate whether or not the go-seeker is
close to identifying an available service. For example, the go-
seeker may request a web service, and the hider can respond with WARM
or COLD HINT types to indicate if a related service might be
available. A go-seeker may only guess up to 20 times. After which,
the go-seeker must reset the CTL/CL before guessing again. This is
depicted in Figure 1.
|....."Ready or Not" Sequence.....|
|-------Service List Request----->|
| [web service] |
| [COLD] |
| [print service] |
| [FREEZING] |
Figure 1: Hinting
This document defines the following HINT types. HINTs are mutually
ABSOLUTE-ZERO : The seeker is not even close to identifying an
FREEZING : The seeker is remotely close to identifying an
COLD : The seeker is somewhat close to identifying an
WARM : The seeker is fairly close to identifying an
HOT : The seeker is very close to identifying an available
BURNING-UP : The seeker is extremely close and is on the verge of
identifying an available service
To allow for the variability in geographic weather, extensibility
through vendor-specified HINT types is possible. These might
includes HINTs such as "COLDER THAN A FREEZER IN ANTARCTICA". New
HINT types do not need registration.
2.8. Truth or Dare as Disambiguation
Hinting, unlike truth or dare, does not require "it" to complete any
challenges other than making guesses to obtain a service list. "It"
is also forbidden from asking the hider any personal questions.
3. Protocol Definition
DPS, needing a reliable transport, uses TCP. However, DPS packets
(both unicast and omnicast) need to signal their mood as Sneaky ;)
4. Security Considerations
Inherently, services not discovered are more secure than those
discovered, due to their obscurity. However, the discoverability or
undiscoverability of a given service is largely independent of its
security characteristics. Instead, an implementor is guided to
[RFC3514] to denote evilness (and associated security) status. Since
[RFC3514] only defines evil and non-evil intent of packets, this
document suggests assigning an "I am not sure" additional value for
the evil bit. The intentional ambiguity of this additional state
makes it a perfect third value for a binary bit.
5. IANA Considerations
IANA is strongly encouraged to look the other way and pretend they
know nothing of this. This document uses values reserved by IANA for
experimentation. It uses ICMPv4 type 253 and ICMPv6 type 200 for
"Insult" with three experimental codes in each, "LOSER" (0), "DORK"
(1), and "TODAY IS SPECIAL" (2). After the experimental phase, well-
known hiding names, including "gone-fishing", "foobar", "service-
name-redacted", and all others listed throughout this document could
be reserved. Famous stage names and Three-Letter Acronyms (TLAs)
[RFC5513] could also be reserved. Lastly, IANA is begged to reserve
the "I am not sure" value for the evil bit.
The authors of this memo and all their pseudonyms do not make any
claims on the originality of the ideas herein described.
7. Informative References
[RFC0862] Postel, J., "Echo Protocol", STD 20, RFC 862, May 1983.
[RFC3514] Bellovin, S., "The Security Flag in the IPv4 Header",
RFC 3514, April 1 2003.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
ICMPv6, UDP, and TCP Headers", RFC 4727, November 2006.
[RFC5513] Farrel, A., "IANA Considerations for Three Letter
Acronyms", RFC 5513, April 1 2009.
[RFC5841] Hay, R. and W. Turkal, "TCP Option to Denote Packet Mood",
RFC 5841, April 1 2010.
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