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Network Working Group                                        D. von Hugo
Internet-Draft                                          Deutsche Telekom
Intended status: Standards Track                             B. Sarikaya
Expires: November 26, 2018                           Denpel Informatique
                                                              T. Herbert
                                                              L. Iannone
                                                       Telecom ParisTech
                                                               S. Bhatti
                                               University of St. Andrews
                                                            May 25, 2018

 Gap and Solution Space Analysis for End to End Privacy Enabled Mapping


   This document presents a gap and solution analysis for end-to-end
   privacy enabled mapping systems.  Each of the identifier locator
   separation system has its own approach to mapping identifiers to the
   locators.  We analyse all these approaches and identify the gaps in
   each of them and do a solution space analysis in an attempt to
   identify a mapping system that can be end to end privacy enabled.

Status of This Memo

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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   3
   3.  Gap and Solution Space Analysis . . . . . . . . . . . . . . .   3
     3.1.  ILNP  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  ILA . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  LISP  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  General Recommendations . . . . . . . . . . . . . . . . . . .   5
     4.1.  Security In the Data Path . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Identifier Locator Systems like ILA [I-D.herbert-intarea-ila], ILNP
   RFC 6740 [RFC6740], and LISP [I-D.ietf-lisp-rfc6830bis]
   [I-D.ietf-lisp-rfc6833bis] are proposed as alternative approaches to
   enabling direct routing in the upcoming converged communication
   networks such as 5G core network (5GC) rather than using tunneling
   with GTP-U, GRE, (P)MIPv6 or similar ones.  In addition to increasing
   packet overhead due to encapsulation that may cause fragmentation and
   all related issues typical disadvantages of (especially static end-
   to-end) tunneling comprise inflexibility to properly react to dynamic
   changes of end points and potential on-path anchors.  Added
   complexity in case of multicast traffic and increased signaling for
   tunnel management are further drawbacks.  Tunnels may introduce
   vulnerabilities or add to the potential for receiver overload and
   thus DOS attacks [draft-ietf-intarea-tunnels-08].  Finally without
   other measures such as deep packet inspection optimization of paths
   according to network resources and application needs becomes complex.

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   With the Id-Loc systems a mapping system needs to be established so
   that 5GC nodes or functions can access the identifier and locator
   values of the destination given the source identifier and locator
   values to enable them to route the packet towards the destination.
   For mapping systems there will be a trade-off between scalability and
   rapid processing versus privacy and security of data.

   A public distributed database such as the DNS is used by end hosts
   for host name (or FQDN) to identifier mapping usually to start the
   communication.  DNS can be used to publicly access identifiers.
   However, using DNS for locator access brings the issue that any node
   in the internet can query and track the location of the roaming UEs
   in 5G network which is not desirable.  A separate database called a
   mapping system needs to be used for identifier to locator mapping.
   Such a mapping system need not be public in order to avoid that any
   node can write new mapping pairs or ID-Loc bindings in such a

2.  Conventions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

   See the definitions in [draft-xyz-atick-ps-oo.txt].

3.  Gap and Solution Space Analysis

3.1.  ILNP

   ILNP uses DNS for identifier to locator mapping.  RFC 6742 [RFC6742]
   defines DNS resource records for identifier called NID and locator
   called L64 for IPv6 and L32 for IPv4.  This allows the end nodes to
   obtain the destination identifier for a given Fully Qualified Domain
   Name (FQDN).  However the same node also gets the locator values
   raising serious privacy issues in the control plane.  ILNP outlines
   locator and identifier privacy solutions in RFC 6748 [RFC6748] in the
   data plane.  Source locator privacy can be preserved by the use of a
   Locator Rewriting Relay (LRR) on the path from the source to the
   destination, e.g. when a UE is in communication with a remote server.
   A LRR provides a mapping between a localised source locator value to
   a different locator value, e.g. a globally routable locator, re-
   writing the packet's source locator value with the new locator value.
   The LRR also handles the reverse path mapping to the source for
   return packets.  For source identifier privacy, ILNP allows the use
   of any privacy mechanisms defined for IPv6 identifiers, e.g.
   ephemeral-use identifier values, ala RFC 4941 [RFC4941], or (better)
   RFC 8064 [RFC8064].

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   For incoming connections to an ILNP node, the identifier and locator
   values are stored in DNS as described above, i.e. ILNP does not
   define a mapping system.  For a 5G network, this could be an internal
   ("private") DNS system, only accessible via the provider.  However,
   it would be possible to define other mapping systems from names to
   identifier/locator values, or, for example, from E.164 numbers to
   ILNPv6 NID/L64 values.  In general, if the source identifier for a UE
   is known to a remote entity, there is the potential for communication
   packets to be linked to a node.  If the source locator of a UE is
   known to a remote entity, there is the potential for topological (and
   possibly geographical) location of that UE to become known.  Also,
   there are concerns on the write operation efficiency for DNS data
   store, i.e. Dynamic DNS in the face of 5G level handovers.

   Furthermore, ILNP demands a change in the way local (e.g., within a
   LAN) communication is carried out, needing all of the devices to
   support ILNP.  This in turn may raise heavy deployability issues.
   However, in 5G UE has a point-to-point connection to 5G core network,
   i.e. no shared LAN is used.

3.2.  ILA

   ILA is currently using a distributed key value (KV) store for
   identifier locator mapping [I-D.herbert-ila-ilamp].  The key value
   NoSQL database also supports publish/subscribe where the senders or
   publishers send the messages while the receivers or subscribers
   receive them and the link by which the messages are transferred is
   called channel.  Such an approach avoids developing a request
   response protocol in order to update the mapping database with new
   identifier locator values or to access locator values for a given
   identifier and also leverages all the recent developments for
   security, availability, reliability, replication, etc.  ILA
   forwarding nodes (ILA-N) maintain caches of identifier locator values
   learned so far but these values are UE specific.  The ILA Mapping
   Protocol (ILAMP) [I-D.herbert-ila-ilamp] is used between ILA
   forwarding nodes and ILA mapping routers (ILA-R).  The purpose of the
   protocol is to populate and maintain the ILA mapping cache in
   forwarding nodes.  ILA-N sends Map Request message to ILA-R with a
   list of identifiers and ILA-R replies with Map Information message
   with identifier to locator mappings.  ILA-R contains a horizontal
   partition of the whole identifier locator database called a shard.
   LISP style request/response protocol based mapping system can also be
   used by ILA as defined in [I-D.rodrigueznatal-ila-lisp].

   Privacy is addressed in the data plane by way of UE simultaneously
   using different addresses for different connections chosen from a
   block of addresses.  It is observed that NAT can also provide address
   privacy but the use of NAT is discouraged in IETF.  UE needs to

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   reestablish connections every time it changes its address so address
   changing incurs delays which could be significant in case of real-
   time communication unless connections can be made simultaneously
   ('make before break').

3.3.  LISP

   In LISP, FQDN to identifier or EID mappings are stored in DNS.  The
   LISP control-plane interface to the identifier-locator or EID-RLOC
   mapping system is defined in [I-D.ietf-lisp-rfc6833bis].  The LISP
   mapping transport system exists in three flavors: LISP-ALT RFC 6836
   [RFC6836] LISP NERD RFC 6837 [RFC6837] and LISP-DDT RFC 8111
   [RFC8111], respectively.  LISP data plane nodes, Ingress/Egress
   Tunnel Routers (ITR/ETR or xTR) registers mappings to the mapping
   system by sending Map-Register messages to the Map-Server(s).  The
   Map Servers then publish these identifier locator values in the
   mapping system.  There is Map-Resolver which accepts Map-Request
   messages from an ITR for the EID and returns the corresponding EID-
   to-RLOC-set mappings by consulting mapping database system in a Map-
   Reply message.  All messages defined in the control plane are UDP
   messages.  All read and write operations to the mapping system are
   authenticated with shared-keys using sha256 as well as ECDSA similar
   to DNSSEC as well as origin authentication, integrity and anti-replay
   protection [I-D.ietf-lisp-sec].

   Note that ITRs keep a small scale identifier locator map of all
   values learned so far called a cache.  In LISP mapping system, the
   lack of privacy support in the control plane for a given identifier
   value exists.  On the data plane, LISP allows to encrypt identifiers
   [RFC8061].  Since ITR uses request/response exchange in getting the
   locator values, until a resolution response is received, packets for
   a flow may be blocked (like any other cache based solution),
   depending on the implementation policy.  This means a Denial of
   Service attack on the ITR or cache has the worst case effect of
   indefinitely blocking a legitimate flow.  Also the cache in ITR may
   raise privacy issue if EID-RLOC values for one UE is used for another
   UE.  However, there are proposals for LISP to use a Publish/Subscribe
   approach [I-D.rodrigueznatal-lisp-pubsub].  While not yet explored,
   in the current LISP specification nothing prevents from using privacy
   addressing by way of UE simultaneously using different addresses for
   different connections chosen from a block of addresses in the data

4.  General Recommendations

   The use of new type of databases known as NoSQL databases organized
   as Key-value stores or mapping systems is recommended.  Such
   databases will provide very efficient read and writes unlike DNS.

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   NoSQL mapping systems mostly support a message-oriented middleware
   system called publish-subscribe or PubSub.  In PubSub, publishers are
   loosely coupled to subscribers and offer better scalability than
   traditional client-server systems because of parallel operation,
   message caching and network based message routing.  Such systems
   support sharding based on a shard key across different database
   servers.  Publish/subscribe mechanism takes cares of the request/
   response mechanism commonly used in DNS or other mapping systems and
   have better DDOS protection.  Although a proposal exists as in
   [I-D.herbert-ila-ilamp], how such a Key-value store will be
   architectured in 5GC is not defined.  Some guidelines for sharding
   need to be developed.  How the mapping database will be sharded based
   on its identifier values as the key differently for each Id-Loc
   system can be defined.

   What is stored in the mapping system is limited to the identifier and
   locator values and no considerations to provide privacy of the stored

   There are many privacy improving mechanisms defined like locator/
   identifier privacy of ILNP discussed in RFC 6748 [RFC6748], frequent
   address changing of ILA, establishing and managing security
   associations between participating entities etc.  Each of these
   techniques can be used by any Id-loc system.  There is a need to
   standardize these privacy techniques in order to enable wide scale
   use by the end nodes.

4.1.  Security In the Data Path

   We address privacy problem for mapping systems: First we state the
   Atick privacy model which can be summarized as privacy at every
   levels.  At the mapping system, the map data will be designed with
   privacy considerations so that the access will be enabled only for
   the allowed entities and disabled for any others.  5GC nodes/
   functions that are ingress/egress nodes may have caches and a
   protocol may be needed to communicate with other 5GC nodes that are
   part of the mapping servers and contains a shard. 5GC nodes/functions
   that are not ingress/egress nodes are considered part of the mapping
   servers and they provide secure access to the mapping data and may
   contain part of the mapping database.  Privacy will be enabled in all
   5GC nodes/functions that deal with the mapping database.  Such
   considerations will be implemented by way of the privacy additions to
   the data stored in the mapping database.  End hosts or UEs will be
   able to have control over their own mapping records stored in the
   mapping database.  End nodes or UEs that are unauthorized will not be
   able to have access to the location data of another UE.  The same
   applies to the unauthorized entities or servers/functions in what 5G
   architecture calls outside data network (DN).

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5.  IANA Considerations


6.  Security Considerations

7.  Acknowledgements

8.  References

8.1.  Normative References

              Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
              Cabellos-Aparicio, "The Locator/ID Separation Protocol
              (LISP)", draft-ietf-lisp-rfc6830bis-12 (work in progress),
              March 2018.

              Fuller, V., Farinacci, D., and A. Cabellos-Aparicio,
              "Locator/ID Separation Protocol (LISP) Control-Plane",
              draft-ietf-lisp-rfc6833bis-10 (work in progress), March

              Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D.
              Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-15
              (work in progress), April 2018.

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

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,

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

   [RFC6742]  Atkinson, RJ., Bhatti, SN., and S. Rose, "DNS Resource
              Records for the Identifier-Locator Network Protocol
              (ILNP)", RFC 6742, DOI 10.17487/RFC6742, November 2012,

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   [RFC6748]  Atkinson, RJ. and SN. Bhatti, "Optional Advanced
              Deployment Scenarios for the Identifier-Locator Network
              Protocol (ILNP)", RFC 6748, DOI 10.17487/RFC6748, November
              2012, <https://www.rfc-editor.org/info/rfc6748>.

   [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>.

   [RFC6837]  Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to
              Routing Locator (RLOC) Database", RFC 6837,
              DOI 10.17487/RFC6837, January 2013,

   [RFC8061]  Farinacci, D. and B. Weis, "Locator/ID Separation Protocol
              (LISP) Data-Plane Confidentiality", RFC 8061,
              DOI 10.17487/RFC8061, February 2017,

   [RFC8064]  Gont, F., Cooper, A., Thaler, D., and W. Liu,
              "Recommendation on Stable IPv6 Interface Identifiers",
              RFC 8064, DOI 10.17487/RFC8064, February 2017,

   [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>.

8.2.  Informative References

              Herbert, T., "Identifier Locator Addressing Mapping
              Protocol", draft-herbert-ila-ilamp-00 (work in progress),
              December 2017.

              Herbert, T. and P. Lapukhov, "Identifier-locator
              addressing for IPv6", draft-herbert-intarea-ila-01 (work
              in progress), March 2018.

              Touch, J. and M. Townsley, "IP Tunnels in the Internet
              Architecture", draft-ietf-intarea-tunnels-08 (work in
              progress), January 2018.

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              Rodriguez-Natal, A., Ermagan, V., Maino, F., and A.
              Cabellos-Aparicio, "LISP control-plane for Identifier
              Locator Addressing (ILA)", draft-rodrigueznatal-ila-
              lisp-01 (work in progress), April 2018.

              Rodriguez-Natal, A., Ermagan, V., Leong, J., Maino, F.,
              Cabellos-Aparicio, A., Barkai, S., Farinacci, D.,
              Boucadair, M., Jacquenet, C., and S. Secci, "Publish/
              Subscribe Functionality for LISP", draft-rodrigueznatal-
              lisp-pubsub-02 (work in progress), March 2018.

              Qu, Y., Cabellos-Aparicio, A., Moskowitz, R., Liu, B., and
              A. Stockmayer, "Gap Analysis for Identity Enabled
              Networks", draft-xyz-ideas-gap-analysis-00 (work in
              progress), July 2017.

Authors' Addresses

   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

   Tom Herbert

   Email: tom@quantonium.net

   Luigi Iannone
   Telecom ParisTech

   Email: ggx@gigix.net

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   Saleem Bhatti
   University of St. Andrews

   Email: saleem@st-andrews.ac.uk

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