Design Considerations for Name Resolution Service in Information-Centric Networking (ICN)
RFC 9138

Document Type RFC - Informational (December 2021; No errata)
Authors Jungha Hong  , Taewan You  , Lijun Dong  , Cedric Westphal  , Börje Ohlman 
Last updated 2021-12-01
Replaces draft-hong-icnrg-nrs-requirements, draft-dong-icnrg-nrs-requirement
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Internet Research Task Force (IRTF)                              J. Hong
Request for Comments: 9138                                        T. You
Category: Informational                                             ETRI
ISSN: 2070-1721                                                  L. Dong
                                                             C. Westphal
                                             Futurewei Technologies Inc.
                                                               B. Ohlman
                                                                Ericsson
                                                           November 2021

Design Considerations for Name Resolution Service in Information-Centric
                            Networking (ICN)

Abstract

   This document provides the functionalities and design considerations
   for a Name Resolution Service (NRS) in Information-Centric Networking
   (ICN).  The purpose of an NRS in ICN is to translate an object name
   into some other information such as a locator, another name, etc. in
   order to forward the object request.  This document is a product of
   the Information-Centric Networking Research Group (ICNRG).

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Research Task Force
   (IRTF).  The IRTF publishes the results of Internet-related research
   and development activities.  These results might not be suitable for
   deployment.  This RFC represents the consensus of the Information-
   Centric Networking Research Group of the Internet Research Task Force
   (IRTF).  Documents approved for publication by the IRSG are not
   candidates for any level of Internet Standard; see Section 2 of RFC
   7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9138.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Table of Contents

   1.  Introduction
   2.  Name Resolution Service in ICN
     2.1.  Explicit Name Resolution Approach
     2.2.  Name-Based Routing Approach
     2.3.  Hybrid Approach
     2.4.  Comparisons of Name Resolution Approaches
   3.  Functionalities of NRS in ICN
     3.1.  Support Heterogeneous Name Types
     3.2.  Support Producer Mobility
     3.3.  Support Scalable Routing System
     3.4.  Support Off-Path Caching
     3.5.  Support Nameless Object
     3.6.  Support Manifest
     3.7.  Support Metadata
   4.  Design Considerations for NRS in ICN
     4.1.  Resolution Response Time
     4.2.  Response Accuracy
     4.3.  Resolution Guarantee
     4.4.  Resolution Fairness
     4.5.  Scalability
     4.6.  Manageability
     4.7.  Deployed System
     4.8.  Fault Tolerance
     4.9.  Security and Privacy
       4.9.1.  Confidentiality
       4.9.2.  Authentication
       4.9.3.  Integrity
       4.9.4.  Resiliency and Availability
   5.  Conclusion
   6.  IANA Considerations
   7.  Security Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

   The current Internet is based upon a host-centric networking
   paradigm, where hosts are identified with IP addresses and
   communication is possible between any pair of hosts.  Thus,
   information in the current Internet is identified by the name of the
   host (or server) where the information is stored.  In contrast to
   host-centric networking, the primary communication objects in
   Information-Centric Networking (ICN) are the named data objects
   (NDOs), and they are uniquely identified by location-independent
   names.  Thus, ICN aims for the efficient dissemination and retrieval
   of NDOs at a global scale and has been identified and acknowledged as
   a promising technology for a future Internet architecture to overcome
   the limitations of the current Internet, such as scalability and
   mobility [Ahlgren] [Xylomenos].  ICN also has emerged as a candidate
   architecture in the Internet of Things (IoT) environment since IoT
   focuses on data and information [Baccelli] [Amadeo] [Quevedo]
   [Amadeo2] [ID.Zhang2].

   Since naming data independently from its current location (where it
   is stored) is a primary concept of ICN, how to find any NDO using a
   location-independent name is one of the most important design
   challenges in ICN.  Such ICN routing may comprise three steps
   [RFC7927]:

   (1)  Name resolution: matches/translates a content name to the
        locator of the content producer or source that can provide the
        content.

   (2)  Content request routing: routes the content request towards the
        content's location based either on its name or locator.

   (3)  Content delivery: transfers the content to the requester.

   Among the three steps of ICN routing, this document investigates only
   the name resolution step, which translates a content name to the
   content locator.  In addition, this document covers various possible
   types of name resolution in ICN such as one name to another name,
   name to locator, name to manifest, name to metadata, etc.

   The focus of this document is a Name Resolution Service (NRS) itself
   as a service or a system in ICN, and it provides the functionalities
   and the design considerations for an NRS in ICN as well as the
   overview of the NRS approaches in ICN.  On the other hand, its
   companion document [NRSarch] describes considerations from the
   perspective of the ICN architecture and routing system when using an
   NRS in ICN.

   This document represents the consensus of the Information-Centric
   Networking Research Group (ICNRG).  It has been reviewed extensively
   by the Research Group (RG) members who are actively involved in the
   research and development of the technology covered by this document.
   It is not an IETF product and is not a standard.

2.  Name Resolution Service in ICN

   A Name Resolution Service (NRS) in ICN is defined as the service that
   provides the name resolution function for translating an object name
   into some other information such as a locator, another name,
   metadata, next-hop info, etc. that is used for forwarding the object
   request.  In other words, an NRS is a service that can be provided by
   the ICN infrastructure to help a consumer reach a specific piece of
   information (or named data object).  The consumer provides an NRS
   with a persistent name, and the NRS returns a name or locator (or
   potentially multiple names and locators) that can reach a current
   instance of the requested object.

   The name resolution is a necessary process in ICN routing, although
   the name resolution either can be separated from the content request
   routing as an explicit process or can be integrated with the content
   request routing as an implicit process.  The former is referred to as
   an "explicit name resolution approach", and the latter is referred to
   as a "name-based routing approach" in this document.

2.1.  Explicit Name Resolution Approach

   An NRS could take the explicit name resolution approach to return the
   locators of the content to the client, which will be used by the
   underlying network as the identifier to route the client's request to
   one of the producers or to a copy of the content.  There are several
   ICN projects that use the explicit name resolution approach, such as
   Data-Oriented Network Architecture (DONA) [Koponen], PURSUIT
   [PURSUIT], Network of Information (NetInf) [SAIL], MobilityFirst
   [MF], IDNet [Jung], etc.  In addition, the explicit name resolution
   approach has been allowed for 5G control planes [SA2-5GLAN].

2.2.  Name-Based Routing Approach

   An NRS could take the name-based routing approach, which integrates
   name resolution with content request message routing as in Named Data
   Networking / Content-Centric Networking (NDN/CCNx) [NDN] [CCNx].

   In cases where the content request also specifies the reverse path,
   as in NDN/CCNx, the name resolution mechanism also derives the
   routing path for the data.  This adds a requirement to the name
   resolution service to propagate the request in a way that is
   consistent with the subsequent data forwarding.  Namely, the request
   must select a path for the data based upon finding a copy of the
   content but also properly delivering the data.

2.3.  Hybrid Approach

   An NRS could also take hybrid approach.  For instance, it can attempt
   the name-based routing approach first.  If this fails at a certain
   router, the router can go back to the explicit name resolution
   approach.  The hybrid NRS approach also works the other way around:
   first by performing explicit name resolution to find the locators of
   routers, then by routing the client's request using the name-based
   routing approach.

   A hybrid approach would combine name resolution over a subset of
   routers on the path with some tunneling in between (say, across an
   administrative domain) so that only a few of the nodes in the ICN
   network perform name resolution in the name-based routing approach.

2.4.  Comparisons of Name Resolution Approaches

   The following compares the explicit name resolution and the name-
   based routing approaches in several aspects:

   *  Overhead due to the maintenance of the content location: The
      content reachability is dynamic and includes new content being
      cached or content being expired from a cache, content producer
      mobility, etc.  Maintaining a consistent view of the content
      location across the network requires some overhead that differs
      for the name resolution approaches.  The name-based routing
      approach may require flooding parts of the network for update
      propagation.  In the worst case, the name-based routing approach
      may flood the whole network (but mitigating techniques may be used
      to scope the flooding).  However, the explicit name resolution
      approach only requires updating propagation in part of the name
      resolution system (which could be an overlay with a limited number
      of nodes).

   *  Resolution capability: The explicit name resolution approach, if
      designed and deployed with sufficient robustness, can offer at
      least weak guarantees that resolution will succeed for any content
      name in the network if it is registered to the name resolution
      overlay.  In the name-based routing approach, content resolution
      depends on the flooding scope of the content names (i.e., content
      publishing message and the resulting name-based routing tables).
      For example, when content is cached, the router may only notify
      its direct neighbors of this information.  Thus, only those
      neighboring routers can build a name-based entry for this cached
      content.  But if the neighboring routers continue to propagate
      this information, the other nodes are able to direct to this
      cached copy as well.

   *  Node failure impact: Nodes involved in the explicit name
      resolution approach are the name resolution overlay servers (e.g.,
      resolution handlers in DONA), while the nodes involved in the
      name-based routing approach are routers that route messages based
      on the name-based routing tables (e.g., NDN routers).  Node
      failures in the explicit name resolution approach may cause some
      content request routing to fail even though the content is
      available.  This problem does not exist in the name-based routing
      approach because other alternative paths can be discovered to
      bypass the failed ICN routers, given the assumption that the
      network is still connected.

   *  Maintained databases: The storage usage for the explicit name
      resolution approach is different from that of the name-based
      routing approach.  The explicit name resolution approach typically
      needs to maintain two databases: name-to-locator mapping in the
      name resolution overlay and routing tables in the routers on the
      data forwarding plane.  The name-based routing approach needs to
      maintain only the name-based routing tables.

   Additionally, some other intermediary step may be included in the
   name resolution -- namely, the mapping of one name to other names --
   in order to facilitate the retrieval of named content by way of a
   manifest [Westphal] [RFC8569].  The manifest is resolved using one of
   the two above approaches, and it may include further mapping of names
   to content and location.  The steps for name resolution then become
   the following: first, translate the manifest name into a location of
   a copy of the manifest, which includes further names of the content
   components and potentially locations for the content, then retrieve
   the content by using these names and/or location, potentially
   resulting in additional name resolutions.

   Thus, no matter which approach is taken by an NRS in ICN, the name
   resolution is the essential function that shall be provided by the
   ICN infrastructure.

3.  Functionalities of NRS in ICN

   This section presents the functionalities of an NRS in ICN.

3.1.  Support Heterogeneous Name Types

   In ICN, a name is used to identify the data object and is bound to it
   [RFC7927].  ICN requires uniqueness and persistency of the name of
   the data object to ensure the reachability of the object within a
   certain scope.  There are heterogeneous approaches to designing ICN
   naming schemes [Bari].  Ideally, a name can include any form of
   identifier, which can be flat or hierarchical, human readable or non-
   readable.

   Although there are diverse types of naming schemes proposed in the
   literature, they all need to provide basic functions for identifying
   a data object, supporting named data lookup, and routing.  An NRS may
   combine the better aspects of different schemes.  Basically, an NRS
   should be able to support a generic naming schema so that it can
   resolve any type of content name, irrespective of whether it is flat,
   hierarchical, attribute based, or anything else.

   In PURSUIT [PURSUIT], names are flat, and the rendezvous functions
   are defined for an NRS, which is implemented by a set of rendezvous
   nodes (RNs), known as the rendezvous network (RENE).  Thus, a name
   consists of a sequence of scope IDs, and a single rendezvous ID is
   routed by the RNs in RENE.  Thus, PURSUIT decouples name resolution
   and data routing, where the NRS is performed by the RENE.

   In MobilityFirst [MF], a name known as a "Global Unique Identifier
   (GUID)", derived from a human-readable name via a global naming
   service, is a flat typed 160-bit string with self-certifying
   properties.  Thus, MobilityFirst defines a Global Name Resolution
   Service (GNRS), which resolves GUIDs to network addresses and
   decouples name resolution and data routing similarly to PURSUIT.

   In NetInf [Dannewitz], information objects are named using Named
   Information (NI) names [RFC6920], which consist of an authority part
   and digest part (content hash).  The NI names can be flat as the
   authority part is optional.  Thus, the NetInf architecture also
   includes a Name Resolution System (NRS), which can be used to resolve
   NI names to addresses in an underlying routable network layer.

   In NDN [NDN] and CCNx [CCNx], names are hierarchical and may be
   similar to URLs.  Each name component can be anything, including a
   human-readable string or a hash value.  NDN/CCNx adopts the name-
   based routing approach.  The NDN router forwards the request by doing
   the longest-match lookup in the Forwarding Information Base (FIB)
   based on the content name, and the request is stored in the Pending
   Interest Table (PIT).

3.2.  Support Producer Mobility

   ICN inherently supports mobility by consumers.  Namely, consumer or
   client mobility is handled by re-requesting the content in case the
   mobility event (say, handover) occurred before receiving the
   corresponding content from the network.  Since ICN can ensure that
   content reception continues without any disruption in ICN
   applications, seamless mobility from the consumer's point of view can
   be easily supported.

   However, producer mobility does not emerge naturally from the ICN
   forwarding model as does consumer mobility.  If a producer moves into
   a different network location or a different name domain, which is
   assigned by another authoritative publisher, it would be difficult
   for the mobility management to update Routing Information Base (RIB)
   and FIB entries in ICN routers with the new forwarding path in a very
   short time.  Therefore, various ICN architectures in the literature
   have proposed adopting an NRS to achieve the producer or publisher
   mobility, where the NRS can be implemented in different ways such as
   rendezvous points and/or overlay mapping systems.

   In NDN [Zhang2], for producer mobility support, rendezvous mechanisms
   have been proposed to build interest rendezvous (RV) with data
   generated by a mobile producer (MP).  This can be classified into two
   approaches: chase mobile producer and rendezvous data.  Regarding MP
   chasing, rendezvous acts as a mapping service that provides the
   mapping from the name of the data produced by the MP to the name of
   the MP's current point of attachment (PoA).  Alternatively, the RV
   serves as a home agent as in IP mobility support, so the RV enables
   the consumer's Interest message to tunnel towards the MP at the PoA.
   Regarding rendezvous data, the solution involves moving the data
   produced by the MP to a data depot instead of forwarding Interest
   messages.  Thus, a consumer's Interest message can be forwarded to
   stationary place called a "data rendezvous", so it would either
   return the data or fetch it using another mapping solution.
   Therefore, RV or other mapping functions are in the role of an NRS in
   NDN.

   In [Ravindran], the forwarding label (FL) object is used to enable
   identifier (ID) and locator (LID) namespaces to be split in ICN.
   Generally, IDs are managed by applications, while locators are
   managed by a network administrator so that IDs are mapped to
   heterogeneous name schemes and LIDs are mapped to the network domains
   or to specific network elements.  Thus, the proposed FL object acts
   as a locator (LID) and provides the flexibility to forward Interest
   messages through a mapping service between IDs and LIDs.  Therefore,
   the mapping service in control plane infrastructure can be considered
   as an NRS in this draft.

   In MobilityFirst [MF], both consumer and publisher mobility can be
   primarily handled by the global name resolution service (GNRS), which
   resolves GUIDs to network addresses.  Thus, the GNRS must be updated
   for mobility support when a network-attached object changes its point
   of attachment, which differs from NDN/CCNx.

   In NetInf [Dannewitz], mobility is handled by an NRS in a very
   similar way to MobilityFirst.

   Besides the consumer and producer mobility, ICN also faces challenges
   to support the other dynamic features such as multi-homing,
   migration, and replication of named resources such as content,
   devices, and services.  Therefore, an NRS can help to support these
   dynamic features.

3.3.  Support Scalable Routing System

   In ICN, the name of data objects is used for routing by either a name
   resolution step or a routing table lookup.  Thus, routing information
   for each data object should be maintained in the routing base, such
   as RIB and FIB.  Since the number of data objects would be very
   large, the size of information bases would be significantly larger as
   well [RFC7927].

   The hierarchical namespace used in CCNx [CCNx] and NDN [NDN]
   architectures reduces the size of these tables through name
   aggregation and improves the scalability of the routing system.  A
   flat naming scheme, on the other hand, would aggravate the
   scalability problem of the routing system.  The non-aggregated name
   prefixes injected into the Default Route Free Zone (DFZ) of ICN would
   create a more serious scalability problem when compared to the
   scalability issues of the IP routing system.  Thus, an NRS may play
   an important role in the reduction of the routing scalability problem
   regardless of the types of namespaces.

   In [Afanasyev], in order to address the routing scalability problem
   in NDN's DFZ, a well-known concept called "map-and-encap" is applied
   to provide a simple and secure namespace mapping solution.  In the
   proposed map-and-encap design, data whose name prefixes do not exist
   in the DFZ forwarding table can be retrieved by a distributed mapping
   system called NDNS, which maintains and looks up the mapping
   information from a name to its globally routed prefixes, where NDNS
   is a kind of an NRS.

3.4.  Support Off-Path Caching

   Caching in-network is considered to be a basic architectural
   component of an ICN architecture.  It may be used to provide a level
   of quality-of-service (QoS) experience to users to reduce the overall
   network traffic, to prevent network congestion and denial-of-service
   (DoS) attacks, and to increase availability.  Caching approaches can
   be categorized into off-path caching and on-path caching based on the
   location of caches in relation to the forwarding path from the
   original server to the consumer.  Off-path caching, also referred to
   as "content replication" or "content storing", aims to replicate
   content within a network in order to increase availability,
   regardless of the relationship of the location to the forwarding
   path.  Thus, finding off-path cached objects is not trivial in name-
   based routing of ICN.  In order to support off-path caches, replicas
   are usually advertised into a name-based routing system or into an
   NRS.

   In [Bayhan], an NRS is used to find off-path copies in the network,
   which may not be accessible via name-based routing mechanisms.  Such
   a capability can be helpful for an Autonomous System (AS) to avoid
   the costly inter-AS traffic for external content more, to yield
   higher bandwidth efficiency for intra-AS traffic, and to decrease the
   data access latency for a pleasant user experience.

3.5.  Support Nameless Object

   In CCNx 1.0 [Mosko2], the concept of a "Nameless Object", which is a
   Content Object without a name, is introduced to provide a means to
   move content between storage replicas without having to rename or re-
   sign the Content Objects for the new name.  Nameless Objects can be
   addressed by the ContentObjectHash, which is to restrict Content
   Object matching by using a SHA-256 hash.

   An Interest message would still carry a name and a ContentObjectHash,
   where a name is used for routing, while a ContentObjectHash is used
   for matching.  However, on the reverse path, if the Content Object's
   name is missing, it is a "Nameless Object" and only matches against
   the ContentObjectHash.  Therefore, a consumer needs to resolve the
   proper name and hashes through an outside system, which can be
   considered as an NRS.

3.6.  Support Manifest

   For collections of data objects that are organized as large and file-
   like contents [FLIC], manifests are used as data structures to
   transport this information.  Thus, manifests may contain hash digests
   of signed Content Objects or other manifests so that large Content
   Objects that represent a large piece of application data can be
   collected by using such a manifest.

   In order to request Content Objects, a consumer needs to know a
   manifest root name to acquire the manifest.  In the case of File-Like
   ICN Collections (FLIC), a manifest name can be represented by a
   nameless root manifest so that an outside system such as an NRS may
   be involved to give this information to the consumer.

3.7.  Support Metadata

   When resolving the name of a Content Object, NRS could return a rich
   set of metadata in addition to returning a locator.  The metadata
   could include alternative object locations, supported object transfer
   protocol(s), caching policy, security parameters, data format, hash
   of object data, etc.  The consumer could use this metadata for the
   selection of object transfer protocol, security mechanism, egress
   interface, etc.  An example of how metadata can be used in this way
   is provided by the Networked Object (NEO) ICN architecture [NEO].

4.  Design Considerations for NRS in ICN

   This section presents the design considerations for NRS in ICN.

4.1.  Resolution Response Time

   The name resolution process should provide a response within a
   reasonable amount of time.  The response should be either a proper
   mapping of the name to a copy of the content or an error message
   stating that no such object exists.  If the name resolution does not
   map to a location, the system may not issue any response, and the
   client should set a timer when sending a request so as to consider
   the resolution incomplete when the timer expires.

   The acceptable response delay could be of the order of a round-trip
   time between the client issuing the request and the NRS servers that
   provide the response.  While this RTT may vary greatly depending on
   the proximity between the two end points, some upper bound needs to
   be used.  Especially in some delay-sensitive scenarios such as
   industrial Internet and telemedicine, the upper bound of the response
   delay must be guaranteed.

   The response time includes all the steps of the resolution, including
   potentially a hop-by-hop resolution or a hierarchical forwarding of
   the resolution request.

4.2.  Response Accuracy

   An NRS must provide an accurate response -- namely, a proper binding
   of the requested name (or prefix) with a location.  The response can
   be either a (prefix, location) pair or the actual forwarding of a
   request to a node holding the content, which is then transmitted in
   return.

   An NRS must provide an up-to-date response -- namely, an NRS should
   be updated within a reasonable time when new copies of the content
   are being stored in the network.  While every transient cache
   addition/eviction should not trigger an NRS update, some origin
   servers may move and require the NRS to be updated.

   An NRS must provide mechanisms to update the mapping of the content
   with its location.  Namely, an NRS must provide a mechanism for a
   content provider to add new content, revoke old/dated/obsolete
   content, and modify existing content.  Any content update should then
   be propagated through the NRS system within reasonable delay.

   Content that is highly mobile may require specifying some type of
   anchor that is kept at the NRS instead of the content location.

4.3.  Resolution Guarantee

   An NRS must ensure that the name resolution is successful with high
   probability if the name-matching content exists in the network,
   regardless of its popularity and the number of cached copies existing
   in the network.  Per Section 4.1, some resolutions may not occur in a
   timely manner.  However, the probability of such an event should be
   minimized.  The NRS system may provide a probability (five 9s or five
   sigmas, for instance) that a resolution will be satisfied.

4.4.  Resolution Fairness

   An NRS could provide this service for all content in a fair manner,
   independently of the specific content properties (content producer,
   content popularity, availability of copies, content format, etc.).
   Fairness may be defined as a per-request delay to complete the NRS
   steps that is agnostic to the properties of the content itself.
   Fairness may be defined as well as the number of requests answered
   per unit of time.

   However, it is notable that content (or their associated producer)
   may request a different level of QoS from the network (see [RFC9064],
   for instance), and this may include the NRS as well, in which case
   considerations of fairness may be restricted to content within the
   same class of service.

4.5.  Scalability

   The NRS system must scale up to support a very large user population
   (including human users as well as machine-to-machine communications).
   As an idea of the scale, it is expected that 50 billion devices will
   be connected in 2025 (per ITU projections).  The system must be able
   to respond to a very large number of requests per unit of time.
   Message forwarding and processing, routing table buildup, and name
   record propagation must be efficient and scalable.

   The NRS system must scale up with the number of pieces of content
   (content names) and should be able to support a content catalog that
   is extremely large.  Internet traffic is of the order of zettabytes
   per year (10^21 bytes).  Since NRS is associated with actual traffic,
   the number of pieces of content should scale with the amount of
   traffic.  Content size may vary from a few bytes to several GB, so
   the NRS should be expected scale up to a catalog of the size of 10^21
   in the near future, and larger beyond.

   The NRS system must be able to scale up -- namely, to add NRS servers
   to the NRS system in a way that is transparent to the users.  The
   addition of a new server should have a limited negative impact on the
   other NRS servers (or should have a negative impact on only a small
   subset of the NRS servers).  The impact of adding new servers may
   induce some overhead at the other servers to rebuild a hierarchy or
   to exchange messages to include the new server within the service.
   Further, data may be shared among the new servers for load balancing
   or tolerance to failure.  These steps should not disrupt the service
   provided by the NRS and should improve the quality of the service in
   the long run.

   The NRS system may support access from a heterogeneity of connection
   methods and devices.  In particular, the NRS system may support
   access from constrained devices, and interactions with the NRS system
   would not be too costly.  An IoT node, for instance, should be able
   to access the NRS system as well as a more powerful node.

   The NRS system should scale up in its responsiveness to the increased
   request rate that is expected from applications such as IoT or
   machine-to-machine (M2M), where data is being frequently generated
   and/or requested.

4.6.  Manageability

   The NRS system must be manageable since some parts of the system may
   grow or shrink dynamically and an NRS system node may be added or
   deleted frequently.

   The NRS system may support an NRS management layer that allows for
   adding or subtracting NRS nodes.  In order to infer the circumstance,
   the management layer can measure the network status.

4.7.  Deployed System

   The NRS system must be deployable since deployability is important
   for a real-world system.  The NRS system must be deployable in
   network edges and cores so that the consumers as well as ICN routers
   can perform name resolution in a very low latency.

4.8.  Fault Tolerance

   The NRS system must ensure resiliency in the event of NRS server
   failures.  The failure of a small subset of nodes should not impact
   the NRS performance significantly.

   After an NRS server fails, the NRS system must be able to recover
   and/or restore the name records stored in the NRS server.

4.9.  Security and Privacy

   On utilizing an NRS in ICN, there are some security considerations
   for the NRS servers/nodes and name mapping records stored in the NRS
   system.  This subsection describes them.

4.9.1.  Confidentiality

   The name mapping records in the NRS system must be assigned with
   proper access rights such that the information contained in the name
   mapping records would not be revealed to unauthorized users.

   The NRS system may support access control for certain name mapping
   records.  Access control can be implemented with a reference monitor
   that uses client authentication, so only users with appropriate
   credentials can access these records, and they are not shared with
   unauthorized users.  Access control can also be implemented by
   encryption-based techniques using control of keys to control the
   propagations of the mappings.

   The NRS system may support obfuscation and/or encryption mechanisms
   so that the content of a resolution request may not be accessible by
   third parties outside of the NRS system.

   The NRS system must keep confidentiality to prevent sensitive name
   mapping records from being reached by unauthorized data requesters.
   This is more required in IoT environments where a lot of sensitive
   data is produced.

   The NRS system must also keep confidentiality of metadata as well as
   NRS usage to protect the privacy of the users.  For instance, a
   specific user's NRS requests should not be shared outside the NRS
   system (with the exception of legal intercept).

4.9.2.  Authentication

   *  NRS server authentication: Authentication of the new NRS servers/
      nodes that want to be registered with the NRS system must be
      required so that only authenticated entities can store and update
      name mapping records.  The NRS system should detect an attacker
      attempting to act as a fake NRS server to cause service disruption
      or manipulate name mapping records.

   *  Producer authentication: The NRS system must support
      authentication of the content producers to ensure that
      update/addition/removal of name mapping records requested by
      content producers are actually valid and that content producers
      are authorized to modify (or revoke) these records or add new
      records.

   *  Mapping record authentication: The NRS should verify new mapping
      records that are being registered so that it cannot be polluted
      with falsified information or invalid records.

4.9.3.  Integrity

   The NRS system must be protected from malicious users attempting to
   hijack or corrupt the name mapping records.

4.9.4.  Resiliency and Availability

   The NRS system should be resilient against denial-of-service attacks
   and other common attacks to isolate the impact of the attacks and
   prevent collateral damage to the entire system.  Therefore, if a part
   of the NRS system fails, the failure should only affect a local
   domain.  And fast recovery mechanisms need to be in place to bring
   the service back to normal.

5.  Conclusion

   ICN routing may comprise three steps: name resolution, content
   request routing, and content delivery.  This document investigates
   the name resolution step, which is the first and most important to be
   achieved for ICN routing to be successful.  A Name Resolution Service
   (NRS) in ICN is defined as the service that provides such a function
   of name resolution for translating an object name into some other
   information such as a locator, another name, metadata, next-hop info,
   etc. that is used for forwarding the object request.

   This document classifies and analyzes the NRS approaches according to
   whether the name resolution step is separated from the content
   request routing as an explicit process or not.  This document also
   explains the NRS functions used to support heterogeneous name types,
   producer mobility, scalable routing system, off-path caching,
   nameless object, manifest, and metadata.  Finally, this document
   presents design considerations for NRS in ICN, which include
   resolution response time and accuracy, resolution guarantee,
   resolution fairness, scalability, manageability, deployed system, and
   fault tolerance.

6.  IANA Considerations

   This document has no IANA actions.

7.  Security Considerations

   A discussion of security guidelines is provided in Section 4.9.

8.  References

8.1.  Normative References

   [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,
              <https://www.rfc-editor.org/info/rfc7927>.

8.2.  Informative References

   [Afanasyev]
              Afanasyev, A. et al., "SNAMP: Secure Namespace Mapping to
              Scale NDN Forwarding", 2015 IEEE Conference on Computer
              Communications Workshops,
              DOI 10.1109/INFCOMW.2015.7179398, April 2015,
              <https://doi.org/10.1109/INFCOMW.2015.7179398>.

   [Ahlgren]  Ahlgren, B., Dannewitz, C., Imbrenda, C., Kutscher, D.,
              and B. Ohlman, "A Survey of Information-Centric
              Networking", IEEE Communications Magazine, Vol. 50, Issue
              7, DOI 10.1109/MCOM.2012.6231276, July 2012,
              <https://doi.org/10.1109/MCOM.2012.6231276>.

   [Amadeo]   Amadeo, M., Campolo, C., Iera, A., and A. Molinaro, "Named
              data networking for IoT: An architectural perspective",
              European Conference on Networks and Communications
              (EuCNC), DOI 10.1109/EuCNC.2014.6882665, June 2014,
              <https://doi.org/10.1109/EuCNC.2014.6882665>.

   [Amadeo2]  Amadeo, M. et al., "Information-centric networking for the
              internet of things: challenges and opportunities", IEEE
              Network, Vol. 30, No. 2, DOI 10.1109/MNET.2016.7437030,
              March 2016, <https://doi.org/10.1109/MNET.2016.7437030>.

   [Baccelli] Baccelli, E., Mehlis, C., Hahm, O., Schmidt, T., and M.
              Wählisch, "Information Centric Networking in the IoT:
              Experiments with NDN in the Wild", ACM-ICN 2014,
              DOI 10.1145/2660129.2660144, 2014,
              <https://doi.org/10.1145/2660129.2660144>.

   [Bari]     Bari, M.F., Chowdhury, S.R., Ahmed, R., Boutaba, R., and
              B. Mathieu, "A Survey of Naming and Routing in
              Information-Centric Networks", IEEE Communications
              Magazine, Vol. 50, No. 12, pp. 44-53,
              DOI 10.1109/MCOM.2012.6384450, December 2012,
              <https://doi.org/10.1109/MCOM.2012.6384450>.

   [Bayhan]   Bayhan, S. et al., "On Content Indexing for Off-Path
              Caching in Information-Centric Networks", ACM-ICN 2016,
              DOI 10.1145/2984356.2984372, September 2016,
              <https://doi.org/10.1145/2984356.2984372>.

   [CCNx]     "CICN", <https://wiki.fd.io/view/Cicn>.

   [Dannewitz]
              Dannewitz, C. et al., "Network of Information (NetInf) -
              An information-centric networking architecture", Computer
              Communications, Vol. 36, Issue 7,
              DOI 10.1016/j.comcom.2013.01.009, April 2013,
              <https://doi.org/10.1016/j.comcom.2013.01.009>.

   [FLIC]     Tschudin, C., Wood, C. A., Mosko, M., and D. Oran, "File-
              Like ICN Collections (FLIC)", Work in Progress, Internet-
              Draft, draft-irtf-icnrg-flic-03, 7 November 2021,
              <https://datatracker.ietf.org/doc/html/draft-irtf-icnrg-
              flic-03>.

   [ID.Zhang2]
              Ravindran, R., Zhang, Y., Grieco, L. A., Lindgren, A.,
              Burke, J., Ahlgren, B., and A. Azgin, "Design
              Considerations for Applying ICN to IoT", Work in Progress,
              Internet-Draft, draft-irtf-icnrg-icniot-03, 2 May 2019,
              <https://datatracker.ietf.org/doc/html/draft-irtf-icnrg-
              icniot-03>.

   [Jung]     Jung, H. et al., "IDNet: Beyond All-IP Network", ETRI
              Journal, Vol. 37, Issue 5, DOI 10.4218/etrij.15.2415.0045,
              October 2015,
              <https://doi.org/10.4218/etrij.15.2415.0045>.

   [Koponen]  Koponen, T., Chawla, M., Chun, B., Ermolinskiy, A., Kim,
              K.H., Shenker, S., and I. Stoica, "A Data-Oriented (and
              Beyond) Network Architecture", ACM SIGCOMM 2007, pp.
              181-192, DOI 10.1145/1282380.1282402, August 2007,
              <https://doi.org/10.1145/1282380.1282402>.

   [MF]       "MobilityFirst Future Internet Architecture Project
              Overview", <http://mobilityfirst.winlab.rutgers.edu>.

   [Mosko2]   Mosko, M., "Nameless Objects", IRTF ICNRG, January 2016,
              <https://datatracker.ietf.org/meeting/interim-2016-icnrg-
              01/materials/slides-interim-2016-icnrg-1-7.pdf>.

   [NDN]      "Named Data Networking", <http://www.named-data.net>.

   [NEO]      Eriksson, A. and A.M. Malik, "A DNS-based information-
              centric network architecture open to multiple protocols
              for transfer of data objects", 21st Conference on
              Innovation in Clouds, Internet and Networks and Workshops
              (ICIN), pp. 1-8, DOI 10.1109/ICIN.2018.8401595, February
              2018, <https://doi.org/10.1109/ICIN.2018.8401595>.

   [NRSarch]  Hong, J., You, T., and V. Kafle, "Architectural
              Considerations of ICN using Name Resolution Service", Work
              in Progress, Internet-Draft, draft-irtf-icnrg-nrsarch-
              considerations-06, 12 February 2021,
              <https://datatracker.ietf.org/doc/html/draft-irtf-icnrg-
              nrsarch-considerations-06>.

   [PURSUIT]  "FP7 PURSUIT", <https://www.fp7-pursuit.eu/>.

   [Quevedo]  Quevedo, J., Corujo, D., and R. Aguiar, "A case for ICN
              usage in IoT environments", IEEE GLOBECOM,
              DOI GLOCOM.2014.7037227, December 2014,
              <https://doi.org/GLOCOM.2014.7037227>.

   [Ravindran]
              Ravindran, R., Chakraborti, A., and A. Azgin, "Forwarding
              Label support in CCN Protocol", Work in Progress,
              Internet-Draft, draft-ravi-icnrg-ccn-forwarding-label-02,
              5 March 2018, <https://datatracker.ietf.org/doc/html/
              draft-ravi-icnrg-ccn-forwarding-label-02>.

   [RFC6920]  Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B.,
              Keranen, A., and P. Hallam-Baker, "Naming Things with
              Hashes", RFC 6920, DOI 10.17487/RFC6920, April 2013,
              <https://www.rfc-editor.org/info/rfc6920>.

   [RFC8569]  Mosko, M., Solis, I., and C. Wood, "Content-Centric
              Networking (CCNx) Semantics", RFC 8569,
              DOI 10.17487/RFC8569, July 2019,
              <https://www.rfc-editor.org/info/rfc8569>.

   [RFC9064]  Oran, D., "Considerations in the Development of a QoS
              Architecture for CCNx-Like Information-Centric Networking
              Protocols", RFC 9064, DOI 10.17487/RFC9064, June 2021,
              <https://www.rfc-editor.org/info/rfc9064>.

   [SA2-5GLAN]
              3GPP, "New WID: 5GS Enhanced support of Vertical and LAN
              Services", TSG SA Meeting #SP-82, December 2018,
              <http://www.3gpp.org/ftp/tsg_sa/TSG_SA/TSGS_82/Docs/SP-
              181120.zip>.

   [SAIL]     "Scalable and Adaptive Internet Solutions (SAIL)",
              <http://www.sail-project.eu/>.

   [Westphal] Westphal, C. and E. Demirors, "An IP-Based Manifest
              Architecture for ICN", ACM-ICN 2015,
              DOI 10.1145/2810156.2812614, September 2015,
              <https://doi.org/10.1145/2810156.2812614>.

   [Xylomenos]
              Xylomenos, G., Ververidis, C., Siris, V., Fotiou, N.,
              Tsilopoulos, C., Vasilakos, X., Katsaros, K., and G.
              Polyzos, "A Survey of Information-Centric Networking
              Research", IEEE Communications Surveys and Tutorials, Vol.
              16, Issue 2, DOI 10.1109/SURV.2013.070813.00063, 2014,
              <https://doi.org/10.1109/SURV.2013.070813.00063>.

   [Zhang2]   Zhang, Y. et al., "A Survey of Mobility Support in Named
              Data Networking", IEEE Conference on Computer
              Communications Workshops,
              DOI 10.1109/INFCOMW.2016.7562050, April 2016,
              <https://doi.org/10.1109/INFCOMW.2016.7562050>.

Acknowledgements

   The authors would like to thank Dave Oran, Dirk Kutscher, Ved Kafle,
   Vincent Roca, Marie-Jose Montpetit, Stephen Farrell, Mirja Kühlewind,
   and Colin Perkins for very useful reviews, comments, and improvements
   to the document.

Authors' Addresses

   Jungha Hong
   ETRI
   Yuseung-Gu
   218 Gajeong-ro
   Daejeon
   34129
   Republic of Korea

   Email: jhong@etri.re.kr

   Tae-Wan You
   ETRI
   Yuseung-Gu
   218 Gajeong-ro
   Daejeon
   34129
   Republic of Korea

   Email: twyou@etri.re.kr

   Lijun Dong
   Futurewei Technologies Inc.
   10180 Telesis Court
   San Diego, CA 92121
   United States of America

   Email: lijun.dong@futurewei.com

   Cedric Westphal
   Futurewei Technologies Inc.
   2330 Central Expressway
   Santa Clara, CA 95050
   United States of America

   Email: cedric.westphal@futurewei.com

   Börje Ohlman
   Ericsson Research
   SE-16480 Stockholm
   Sweden

   Email: Borje.Ohlman@ericsson.com