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Network Working Group                                         L. Iannone
Internet-Draft                                             Telecom Paris
Intended status: Standards Track                             D. von Hugo
Expires: September 10, 2020                             Deutsche Telekom
                                                             B. Sarikaya
                                                     Denpel Informatique
                                                             E. Nordmark
                                                           March 9, 2020

        Privacy issues in Identifier/Locator Separation Systems


   There exists several protocols and proposals that leverage on the
   Identifier/Locator split paradigm, having some form of control plane
   by which participating nodes can share their current Identifier-to-
   Location information with their peers.  This document explores some
   of the privacy considerations for such a type of system.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 10, 2020.

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   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Keywords and Terminology  . . . . . . . . . . . . . . . . . .   4
   3.  Identifier Locator Separation and Privacy . . . . . . . . . .   4
   4.  Identifier Locator Split Protocols  . . . . . . . . . . . . .   5
     4.1.  Locator/Identifier Separation Protocol (LISP) . . . . . .   5
     4.2.  Identifier/Locator Network Protocol (ILNP)  . . . . . . .   5
     4.3.  Information Centric Networking (ICN)  . . . . . . . . . .   5
     4.4.  Host Identity Protocol (HIP)  . . . . . . . . . . . . . .   6
     4.5.  Virtual eXtensible Local Area Network (VXLAN) . . . . . .   6
     4.6.  Some Relevant Privacy-Critical Scenarios  . . . . . . . .   6
   5.  Threats against Privacy . . . . . . . . . . . . . . . . . . .   7
     5.1.  Location Privacy  . . . . . . . . . . . . . . . . . . . .   8
     5.2.  Movement Privacy  . . . . . . . . . . . . . . . . . . . .   8
   6.  Not everybody all the time  . . . . . . . . . . . . . . . . .   8
     6.1.  Optimized Routing . . . . . . . . . . . . . . . . . . . .   8
     6.2.  Family and Friends  . . . . . . . . . . . . . . . . . . .   8
     6.3.  Business Assets . . . . . . . . . . . . . . . . . . . . .   9
   7.  Boundary between ID/locator part and rest of Internet . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   When the IP address is separated, one way or another, into an
   identifier and a locator, there is typically the need to be able to
   look up an identifier to find possible locators which can be used to
   reach the identified endpoint.  If such a system (think a distributed
   database) was publicly available, then this would introduce
   additional privacy considerations which do not exist in the absence
   of the ID/locator split.  Think for instance if identifiers are
   assigned to devices such as mobile phones which have a strong binding
   with an individual.  Having the location of such identifier publicly
   available implies make the individual whereabouts public.

   Without an ID/locator split, a device is already providing its IP
   address (in the form of a source address) to any network device along
   the path, and also to the remote endpoint.  That endpoint in
   particular might use IP geolocation databases to get a pretty good

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   idea of where its peer is located, for instance to offer information
   and/or advertising relevant to that location.

   However, in such scenario, when a device (e.g., a laptop or
   smartphone connected over WiFi) moves (e.g., from home to a coffee
   shop) the IP address changes.  This makes it harder for network
   devices along the paths to realize that the it is the same mobile
   device.  If the mobile device is not retaining cookies or logged into
   websites, those remote peers would also have some difficulty
   determining whether it is the same mobile device.  Furthermore, a
   mobile device which is using typical cellular network technologies
   ends up with an IP address, at least as seen by remote peers outside
   of the cellular network, which is associated with the cellular
   operator but does not necessarily indicate a particular location of
   the mobile device.

   Note that even if the IP address isn't always useful to track a
   mobile device today, there are several mechanisms higher in the stack
   which can do this.  For instance cookies or SSL sessions,
   applications which share GPS location, or operators who offer
   additional location information (for instance based on which cellular
   base station a mobile device is using) to business partners.

   Promising proposals leveraging on the Identifier Locator (Id-Loc)
   separation paradigm are: Identifier-Locator Network Protocol (ILNP)
   [RFC6740]; Locator/ID Separation Protocol (LISP)
   [I-D.ietf-lisp-rfc6830bis] [I-D.ietf-lisp-rfc6833bis]; Virtual
   eXtensible LAN [RFC7348]; Information-Centric Networking (ICN)
   [RFC7927]; Host Identity Protocol (HIP) [RFC4423].  Note that ICN
   does not leverage on IP addresses, however, the general architecture
   for this paradgim is based on a clear separation between content
   identifier and content location.  Similarly, in HIP the identifier,
   while identifying representing a communication end-point it is not an
   IP address.

   Architectures and protocols for these approaches are already
   documented in detail and some are under continuous evolution in
   different WGs or RGs.  This document on the other hand attempts to
   identify potential issues with respect to real-world deployment
   scenarios, which may demand for implementations of the above-
   mentionned Id-Loc systems.  In particular, this document overviews
   issues related to threats due to privacy violation of devices and
   their users, as well as location detection and movement tracking,
   where specific countermeasures may be needed.

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2.  Keywords and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Identifier: An identifier is information allowing to unambiguously
   identify an entity or an entity group within a given scope.  An
   identifier is the equivalent of an End-point IDentifier (EID) in The
   Locator/ID Separation Protocol (LISP).  It may or may not be visible
   in communications.

   Locator: A locator is a routable network address.  It may be
   associated with an identifier and used for communication on the
   network layer according to identifier locator split principle.  A
   locator is the equivalent of a Routing Locator (RLOC) in LISP or an
   IP address in other cases.

3.  Identifier Locator Separation and Privacy

   Identifier represents a communication end-point, a content, or any
   identifiable entity and may not be a routable IP address, and in
   general it is not an IP address at all.  Locator may represent a
   communication end-point, and in this case it usually is a routable
   network address.  Because entities identified by an Identifier can
   move the association between Identifiers and Locators may be
   ephemeral.  A database called a mapping system needs to be used for
   Identifier to Locator mapping.  Identifiers are mapped to locators
   for reachability purposes.  A mapping system has to handle mobility
   by updating the identifier to locator mappings in the database.  Note
   that different protocols/system may use a different terminology,
   however, the principle remains the same: a form of (ephemeral)
   binding between identifiers and locators.

   To start the communication, a device needs to know the identifier of
   the destination, hence it relies on a identifier lookup process to
   obtain the associated locator(s).  Note that both identifier and
   locator may be carried in clear in packet headers, depending on the
   specific technology used and the level of security/privacy enforced.

   Usage of identifiers (and their locators) readily available for
   public access raises privacy issues.  For public entities, it may be
   desirable to have their fully qualified domain names or host names
   available for public lookups by the clients.  For private entities,
   usually the clients of the public ones, however, this is not the
   case.  For instance for individuals roaming in a mobile network may

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   not want their locators publicly available, or may be onlyavailable
   to the memebers of his/her family.

   Privacy is an increasingly desirable and often necessary property for
   Internet technologies.

4.  Identifier Locator Split Protocols

   Herefater a non-exhaustive overview of protocolc/system leveraging on
   the Locator/Identifier seapration is provided.

4.1.  Locator/Identifier Separation Protocol (LISP)

   Locator/Id Separation Protocol (LISP) [I-D.ietf-lisp-rfc6830bis]
   [I-D.ietf-lisp-rfc6833bis] is based on a map-and-encap approach,
   which provides a level of indirection for routing and addressing
   performed at specific ingress/egress routers at the LISP domain
   boundaries.  Such border routers performing LISP encapsulation at the
   packet's source stub network are indicated as Ingress Tunnel Routers
   (ITRs), while border routers at the packet's destination stub network
   are called Egress Tunnel Routers (ETRs), all of them are indicated by
   the general term xTRs.  In order to obtain mappings used for
   encapsulation operation, xTRs query the mapping system in order to
   obtain all mappings related to a certain EID only when necessary
   (usually, but not exclusively, at the beginning of a new flow
   transmission).  The LISP control plane protocol
   [I-D.ietf-lisp-rfc6833bis] allows to support several different
   mapping systems (e.g., LISP+ALT [RFC6836] and LISP-DDT [RFC8111]).
   More than that, it can actually also be applied to various other data
   plane protocols.

4.2.  Identifier/Locator Network Protocol (ILNP)

   Identifier-Locator Network Protocol (ILNP) [RFC6740] is a host-based
   approach enabling mobility using mechanisms that are only deployed in
   end-systems and do not require any router changes.

4.3.  Information Centric Networking (ICN)

   Information-Centric Networking (ICN) [RFC7927] is an approach to
   evolve the Internet infrastructure to directly support information
   distribution by introducing uniquely named data as a core Internet
   principle.  Data becomes independent from location, application,
   storage, and means of transportation, enabling or enhancing a number
   of desirable features, such as security, user mobility, multicast,
   and in-network caching.

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4.4.  Host Identity Protocol (HIP)

   The Host Identity Protocol (HIP) [RFC4423] Architecture introduces a
   new namespace, namely the Host Identity namespace, and a new
   protocol.  The HIP protocol aim at providing for limited forms of
   trust between systems, enhance mobility, multi-homing, and dynamic IP
   renumbering; aid in protocol translation/transition; and reduce
   certain types of denial-of-service (DoS) attacks.

4.5.  Virtual eXtensible Local Area Network (VXLAN)

   Virtual Extensible LAN (VXLAN) [RFC7348] is a network virtualization
   technology that attempts to address the scalability problems
   associated with large cloud computing deployments.  It uses a VLAN-
   like encapsulation technique to encapsulate layer 2 Ethernet frames
   within layer 4 UDP datagrams, using 4789 as the default IANA-assigned
   destination UDP port number.  VXLAN endpoints, which terminate VXLAN
   tunnels and may be either virtual or physical switch ports, are known
   as VXLAN tunnel endpoints (VTEPs) and can be considered the locators
   of the devices in the extended VLAN.

4.6.  Some Relevant Privacy-Critical Scenarios

   The collection of scenarios shall serve as an overview of possible
   Loc/ID separation application and help in identifying different
   issues in privacy and security in generic Identifier Locator Split

4.6.1.  Industrial IoT

   Sensors and other connected things in the industry are usually not
   personal items (e.g. wearables) potentially revealing an individuals
   sensitive information.  Yet, industrial connected objects are
   business assets whose information (e.g. location) should be available
   only to authorised intra-company entities.  Hence, there is an
   interest in not shaing the ID/Locator binding with third parties, to
   retain the privacy.  This can be achieved in a number of ways such
   as: using an ID/locator system but using some fixed anchor point as a
   locator; injecting routing prefixes for the ID prefixes into the
   normal routing system and use proxy indirection; providing limited
   ID/Locator exposure.  These are just examples, more approaches should
   be explored in order to find which one is the most suitable in the
   context of industrial IoT.

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4.6.2.  5G

   Upcoming new truly universal communication via so-called 5G systems
   will demand for much more than (just) higher bandwidth and lower
   latency.  Integration of heterogeneous multiple access technologies
   (both wireless and wireline) controlled by a common converged core
   network and the evolution to service-based flexile functionalities
   instead of hard-coded network functions calls for new protocols both
   on control and user (data) plane.  While Id-Loc approach would serve
   well here, the challenge to provide a unique level of security and
   privacy even for a lightweight routing and forwarding mechanism -
   allowing for ease of deployment and migration from existing
   operational network architecture - remains to be solved.

4.6.3.  Cloud

   The cloud, i.e. a set of distributed data centers for processing and
   storage connected via high-speed transmission paths, is seen as
   logical location for content and also for virtualized network
   function instances and shall provide measures for easy re-location
   and migration of these instances deployed as e.g. containers or
   virtual machines.  Id-Loc split routing protocols are proposed for
   usage here as in VXLAN [RFC7348] and LISP [I-D.ietf-lisp-rfc6830bis]
   [I-D.ietf-lisp-rfc6833bis] while the topology of the cloud components
   and logical correlations shall be invisible from outside.

   In a cloud, an upstream IP address does not necessarily belong to the
   actual service location, but a gateway or load balancer.  So, the
   locator or also ID reveal the location with the accuracy of a data
   center, not the function taking a service request.  This issue also
   manifests itself in today's LTE as PGWs are in a data center binding
   UEs' IP addresses which are from the network of the data center.

5.  Threats against Privacy

   There seems to be at least two different privacy threats relating to
   ID/locator mapping systems:

   1.  Location Privacy
   2.  Movement Privacy

   Note that these threats appear in the hypothesys that the ID does not
   change.  Nevertheless, even in the case of mutable IDs, there are
   other forms of information correlation that may allow to identify
   network entities.

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5.1.  Location Privacy

   If a third party can at any time determine the IP location of some
   identifier, then the device can at one point be IP geolocated at
   home, and later a coffee shop.

5.2.  Movement Privacy

   If a third party can determine that an identifier has changed
   locator(s) at time T, then even without knowing the particular
   locators before and after, it can correlate this movement event with
   other information (e.g., security cameras) to create a binding
   between the identifier and a person.

6.  Not everybody all the time

   In order to see the benefits about but minimizing the privacy
   implication one can explore limiting to which peers and when the ID/
   locator binding are exposed.

   A few initial examples help illustrate this.

6.1.  Optimized Routing

   If some operator of a network where there is a large amount of
   mobility wants to ensure efficient routing, then a ID/locator split
   approach might make sense.  Such a system can potentially be limited
   to the set of devices (routers etc) which are under the operators
   control.  If this is the case, then the ID/locator mapping system can
   provide access control so that only those trusted devices can access
   the mappings.

   Note that from a privacy perspective this isn't any different than
   the same operator using a link-state routing protocol to share host
   routes for all the mobile devices.  In that case all participants in
   the link-state protocol can determine the location (attached to which
   router) and notice any mobility events.  Of course, there are
   significant non-privacy differences between those two approaches.

   Exposing the ID/locator mapping to attached devices (e.g., any mobile
   devices which wouldn't be trusted to participate in the link-state
   routing counterpart approach), will change the privacy implications.

6.2.  Family and Friends

   There are cases where it is quite reasonable to share location
   information with other family members or friends.  For instance,
   young children might run applications which enable their parents to

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   track them on their way to/from school.  And I might share my
   location with friends so we can more easily find each other while out
   on town.

   Today such location sharing happens at an application layer using GPS
   coordinates.  But while such sharing is in effect, it wouldn't be
   unreasonable to also consider sharing IP locators to make it more
   efficient or more robust to e.g., route a video feed from one device
   to another.

6.3.  Business Assets

   In the area of Industrial IoT there are cases where an asset owner
   might want to ensure that their assets can communicate efficiently
   and robustly.  In many cases those assets might be decoupled from any
   persons, but there can still be strong reasons to not share the ID/
   locator binding with third parties, such as enabling competitors to
   determine the number of deployed devices in a particular IP prefix.

7.  Boundary between ID/locator part and rest of Internet

   If the access to the ID/locator mapping are restricted as suggested
   above, then most of the potential peer devices would not have access
   to the ID/locator mappings.  This means that there has to be a
   demarcation point between the part of the network which can access
   the ID/locator mappings for a particular identifier and the one which
   can not.  There might be several choices how to handle this such as
   still using an ID/locator system but pointing a locator for some
   fixed anchor point, or injecting routing prefixes for the ID prefixes
   into the normal routing system, or not providing any stable locators
   across this boundary; only allow ephemeral IP addresses per session
   or otherwise limited exposure.

8.  Security Considerations

   This document discusses privacy considerations, but does not explore
   any security considerations.

9.  IANA Considerations

   There are no IANA actions needed for this document.

10.  References

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              Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
              Cabellos-Aparicio, "The Locator/ID Separation Protocol
              (LISP)", draft-ietf-lisp-rfc6830bis-32 (work in progress),
              March 2020.

              Farinacci, D., Maino, F., Fuller, V., and A. Cabellos-
              Aparicio, "Locator/ID Separation Protocol (LISP) Control-
              Plane", draft-ietf-lisp-rfc6833bis-27 (work in progress),
              January 2020.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC4423]  Moskowitz, R. and P. Nikander, "Host Identity Protocol
              (HIP) Architecture", RFC 4423, DOI 10.17487/RFC4423, May
              2006, <https://www.rfc-editor.org/info/rfc4423>.

   [RFC6740]  Atkinson, RJ. and SN. Bhatti, "Identifier-Locator Network
              Protocol (ILNP) Architectural Description", RFC 6740,
              DOI 10.17487/RFC6740, November 2012,

   [RFC6836]  Fuller, V., Farinacci, D., Meyer, D., and D. Lewis,
              "Locator/ID Separation Protocol Alternative Logical
              Topology (LISP+ALT)", RFC 6836, DOI 10.17487/RFC6836,
              January 2013, <https://www.rfc-editor.org/info/rfc6836>.

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,

   [RFC7927]  Kutscher, D., Ed., Eum, S., Pentikousis, K., Psaras, I.,
              Corujo, D., Saucez, D., Schmidt, T., and M. Waehlisch,
              "Information-Centric Networking (ICN) Research
              Challenges", RFC 7927, DOI 10.17487/RFC7927, July 2016,

   [RFC8111]  Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A.
              Smirnov, "Locator/ID Separation Protocol Delegated
              Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111,
              May 2017, <https://www.rfc-editor.org/info/rfc8111>.

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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Authors' Addresses

   Luigi Iannone
   Telecom Paris

   Email: ggx@gigix.net

   Dirk von Hugo
   Deutsche Telekom
   Deutsche-Telekom-Allee 7
   D-64295 Darmstadt

   Email: Dirk.von-Hugo@telekom.de

   Behcet Sarikaya
   Denpel Informatique

   Email: sarikaya@ieee.org

   Erik Nordmark
   Santa Clara, CA

   Email: nordmark@sonic.net

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