Privacy issues in Identifier/Locator Separation Systems

Versions: 00 01                                                         
Network Working Group                                         L. Iannone
Internet-Draft                                             Telecom Paris
Intended status: Standards Track                             D. von Hugo
Expires: July 26, 2020                                  Deutsche Telekom
                                                             B. Sarikaya
                                                     Denpel Informatique
                                                             E. Nordmark
                                                        January 23, 2020

        Privacy issues in Identifier/Locator Separation Systems


   There exist 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.

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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  . . . . . . . . . . . . . . . . . .   3
   3.  Identifier Locator Split Protocols and Use-Cases  . . . . . .   4
     3.1.  Identifier Locator Separation Protocols . . . . . . . . .   4
     3.2.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Assumptions . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Threats against Privacy . . . . . . . . . . . . . . . . . . .   7
     5.1.  Location Privacy  . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Movement Privacy  . . . . . . . . . . . . . . . . . . . .   7
   6.  Not everybody all the time  . . . . . . . . . . . . . . . . .   7
     6.1.  Optimized Routing . . . . . . . . . . . . . . . . . . . .   8
     6.2.  Family and Friends  . . . . . . . . . . . . . . . . . . .   8
     6.3.  Business Assets . . . . . . . . . . . . . . . . . . . . .   8
   7.  Boundary between ID/locator part and rest of Internet . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

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

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   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 it is the same mobile
   device.  And 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 are Identifier Locator (Id-Loc) separation
   systems like, 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], and

   Architectures and protocols for these approaches are already
   documented in detail and are under continuous evolution in different
   WGs.  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-mentioned 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.

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

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   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 Split Protocols and Use-Cases

3.1.  Identifier Locator Separation Protocols

   Identifier represents a communication end-point of an entity and may
   not be routable.  Locator also represents a communication end-point,
   however, it 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.

   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 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, however, this is not the case in general for
   all identifiers, e.g. for individuals roaming in a mobile network.

3.1.1.  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.

3.1.2.  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

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   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.

3.1.3.  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.

3.2.  Use Cases

   The collection of use-cases shall serve as an overview of possible
   Loc-ID split application and help in identifying different issues in
   privacy and security in generic Identifier Locator Split approaches.

3.2.1.  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 which should be detected/accessed only by authorised
   intra-company entities.  Since the huge amount of these things
   (massive IoT) as well as the typical energy and bandwidth constraints
   of battery-powered devices may pose a challenge to traditional
   routing and security measures.

   In Industrial IoT, there are very strong reasons to not share the ID/
   Locator binding with third parties, i.e. 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.

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   These are just examples, more approaches should be explored in order
   to find which one is the most suitable in the context of industrial

3.2.2.  5G Use Case

   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.

3.2.3.  Cloud Use Case

   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 4G cellular networks (LTE/EPS) as the
   Packet Data Network Gateways (PGWs) [3GPP] interfacing the Internet
   are often realised already virtually in a data center, binding
   UEs' IP addresses which are from the network of the data center.

4.  Assumptions

   We assume that there are benefits associated with sharing ID to
   locator mappings with some peers sometimes.  Those benefits can be

   o  Lower latency and higher bandwidth: If two peer devices have some
      locators which are topologically closer, then sharing all the
      locators means that the devices can find a shorter path (fewer hops
      and/or shorter round-trip time), or find a path, which offers higher
      throughput, then if the devices only shared some form of default

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   o  Higher availability and robustness: If two peer devices share all
      their locators, then if there is some network outage the devices
      can autonomously discover a working path using the different
      locator pairs.

   However, those benefits do not imply that it is a good idea to always
   share all of the locators with everybody.  That would make tracking
   by third parties trivial.

   A device can obfuscate itself by, instead of using a single long-
   lived identifier, using multiple short-lived identifiers.  In that
   case the value to the ID/locator binding for any particular
   identifier would be lower.  However, this assumes that the device can
   ensure no relation between the different identifiers it is using,
   either concurrently or over time.  Also, some of the benefits above
   implicitly assume that there can be some long-lived sessions or
   associations between pairs of identifiers.  For instance, if a device
   would need to go fetch the current identifier of its peer from some
   removed system, then it might not experience improved robustness since
   that fetch might depend on the failed external connectivity.  Thus we
   believe that we can explore the core of the ID/locator privacy issue
   by looking at long-lived identifiers.

5.  Threats against Privacy

   There seem to be at least two different privacy threats relating to
   ID/locator mapping systems.

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.

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   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 an 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
   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
   in 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.

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

   If the access to the ID/locator mapping is 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 to 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

              Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
              Cabellos-Aparicio, "The Locator/ID Separation Protocol
              (LISP)", draft-ietf-lisp-rfc6830bis-30 (work in progress),
              January 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,

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

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   [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, <>.

   [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,

   [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, <>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

   [3GPP]     3GPP TS 23.401: "General Packet Radio Service (GPRS)
              enhancements for Evolved Universal Terrestrial Radio
              Access Network (E-UTRAN) access",

Authors' Addresses

   Luigi Iannone
   Telecom Paris


   Dirk von Hugo
   Deutsche Telekom

   D-64295 Darmstadt


   Behcet Sarikaya
   Denpel Informatique


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   Erik Nordmark
   Santa Clara, CA


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