Internet Research Task Force (IRTF) J. Hong

Internet Research Task Force (IRTF) J. Hong
Request for Comments: 9236 T. You
Category: Informational ETRI
ISSN: 2070-1721 V. Kafle
NICT
April 2022

Architectural Considerations of Information-Centric Networking (ICN)
Using a Name Resolution Service

Abstract

This document describes architectural considerations and implications
related to the use of a Name Resolution Service (NRS) in Information-
Centric Networking (ICN). It explains how the ICN architecture can
change when an NRS is utilized and how its use influences the ICN
routing system. 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/rfc9236.

Copyright Notice

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Table of Contents

1. Introduction
2. Terminology
3. Background
4. Implications of an NRS in ICN
5. ICN Architectural Considerations for NRS
5.1. Name Mapping Records Registration, Resolution, and Update
5.2. Protocols and Semantics
5.3. Routing System
6. Conclusion
7. IANA Considerations
8. Security Considerations
9. References
9.1. Normative References
9.2. Informative References
Acknowledgements
Authors' Addresses

1. Introduction

Information-Centric Networking (ICN) is an approach to evolving the
Internet infrastructure to provide direct access to Named Data
Objects (NDOs) by names. In two common ICN architectures, Named Data
Networking (NDN) [NDN] and Content-Centric Networking (CCNx) [CCNx],
the name of an NDO is used directly to route a request to retrieve
the data object. Such direct name-based routing has inherent
challenges in enabling a globally scalable routing system,
accommodating producer mobility, and supporting off-path caching.
These specific issues are discussed in detail in Section 3. In order
to address these challenges, a Name Resolution Service (NRS) has been
utilized in the literature as well as the proposals of several ICN
projects [Afanasyev] [Zhang2] [Ravindran] [SAIL] [MF] [Bayhan].

This document describes the potential changes in the ICN architecture
caused by the introduction of an NRS and the corresponding
implication to the ICN routing system. It also describes ICN
architectural considerations for the integration of an NRS. The
scope of this document includes considerations from the perspective
of an ICN architecture and routing system when using an NRS in ICN.
A description of the NRS itself is provided in the companion NRS
design considerations document [RFC9138], which provides the NRS
approaches, functions, and design considerations.

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. Terminology

Name Resolution Service (NRS): An NRS in ICN is defined as a service
that provides the function of translating a content name or a data
object name into some other information such as a routable prefix,
a locator, an off-path-cache pointer, or an alias name that is
more amenable than the input name to forwarding the object request
toward the target destination storing the NDO [RFC9138]. An NRS
is most likely implemented through the use of a distributed
mapping database system. The Domain Name System (DNS) may be used
as an NRS. However, in this case, the requirements of frequent
updates of NRS records due to the creations of a lot of new NDOs
and changes in their locations in the network need to be
considered.

NRS server: An NRS comprises the distributed NRS servers storing the
mapping records in their databases. NRS servers store and
maintain the mapping records that keep the mappings of content or
object name to some other information that is used for forwarding
the content request or the content itself.

NRS resolver: The client-side function of an NRS is called an NRS
resolver. The NRS resolver is responsible for initiating name
resolution request queries that ultimately lead to a name
resolution of the target data objects. NRS resolvers can be
located in the consumer (or client) nodes and/or ICN routers. An
NRS resolver may also cache the mapping records obtained through
the name resolution for later usage.

Name registration: In order to populate the NRS, the content names
and their mapping records must be registered in the NRS system by
a publisher who has access rights to at least one authoritative
NRS server or by a producer who generates named data objects. The
records contain the mapping of an object name to some information
such as other alias names, routable prefixes, and locators, which
are used for forwarding the content request. Thus, a publisher or
producer of content creates an NRS registration request and sends
it to an NRS server. On registration, the NRS server stores (or
updates) the name mapping record in the database and sends an
acknowledgement back to the producer or publisher that made the
registration request.

Name resolution: Name resolution is the main function of the NRS
system. It is performed by an NRS resolver, which can be deployed
on a consumer node or an ICN router. Resolvers are responsible
for either returning a cached mapping record (whose lifetime has
not expired) or alternatively sending a name resolution request
toward an NRS server. The NRS server searches for the content
name in its mapping record database and, if found, retrieves the
mapping record and returns it in a name resolution response
message to the NRS resolver.

NRS node: NRS servers are also referred to as NRS nodes that
maintain the name records. The terms are used interchangeably.

NRS client: A node that uses the NRS is called an NRS client. Any
node that initiates a name registration, resolution, or update
procedure is an NRS client; that is, NRS resolvers, ICN client
nodes, ICN routers, or producers can be NRS clients.

3. Background

A pure name-based routing approach in ICN has inherent challenges in
enabling a globally scalable routing system, accommodating producer
mobility, and supporting off-path caching. In order to address these
challenges, an NRS has been utilized in proposals and literature of
several ICN projects as follows:

Routing scalability: In ICN, application names identifying content
are intended to be used directly for packet delivery, so ICN
routers run a name-based routing protocol to build name-based
routing and forwarding tables. Similar to the scalability
challenge of IP routing, if non-aggregatable name prefixes are
injected into the Default Route Free Zone (DFZ) of ICN routers,
they would be driving the uncontrolled growth of the DFZ routing
table size. Thus, providing the level of indirection enabled by
an NRS in ICN can be an approach to keeping the routing table size
under control. The NRS system resolves name prefixes that do not
exist in the DFZ forwarding table into globally routable prefixes
such as the one proposed in NDN [Afanasyev]. Another approach
dealing with routing scalability is the Multi-level Distributed
Hash Table (MDHT) used in NetInf [Dannewitz]. It provides name-
based anycast routing that can support a non-hierarchical
namespace and can be adopted on a global scale [Dannewitz2].

Producer mobility: In ICN, if a producer moves into a different name
domain that uses a different name prefix, the request for a
content produced by the moving producer with the origin content
name must be forwarded to the moving producer's new location.
Especially in a hierarchical naming scheme, producer mobility
support is much harder than in a flat naming scheme since the
routing tables in a broader area need to be updated to track the
producer movement. Therefore, various ICN architectures such as
NetInf [Dannewitz] and MobilityFirst [MF] have adopted NRS systems
to tackle the issues of producers whose location changes.

Off-path caching: In-network caching is a common feature of an ICN
architecture. Caching approaches can be categorized into on-path
caching and off-path caching, according to the location of caches
in relation to the forwarding path from the original content store
to a consumer. Off-path caching, sometimes also referred to as
content replication or content storing, aims to replicate a Named
Data Object in various locations within a network in order to
increase the availability of content, reduce access latency, or
both. These caching locations may not be lying along the content
forwarding path. Thus, finding off-path cached content requires
more complex forwarding procedures if a pure name-based routing is
employed. In order to support access to off-path caches, the
locations of replicas are usually advertised into a name-based
routing system or into an NRS as described in [Bayhan].

This document discusses architectural considerations and implications
of ICN when an NRS is utilized to solve such challenges facing a
name-based routing in ICN.

4. Implications of an NRS in ICN

An NRS is not a mandatory part of an ICN architecture, as the
majority of ICN architectures uses name-based routing that avoids the
need for a name resolution procedure. Therefore, the utilization of
an NRS in an ICN architecture changes some architectural aspects at
least with respect to forwarding procedures, latency, and security,
as discussed below:

Forwarding procedure: When an NRS is included in an ICN
architecture, the name resolution procedure has to be included in
the ICN overall routing and forwarding architectural procedures.
To integrate an NRS into an ICN architecture, there are certain
things that have to be decided and specified such as where, when,
and how the name resolution task is performed.

Latency: When an NRS is included in an ICN architecture, additional
latency introduced by the name resolution process is incurred by
the routing and forwarding system. Although the latency due to
the name resolution is added, the total latency of individual
requests being served could be lower if the nearest copies or off-
path caches can be located by the NRS lookup procedure.
Additionally, there might be a favorable trade-off between the
name resolution latency and inter-domain traffic reduction by
finding the nearest off-path cached copy of the content. Finding
the nearest cache holding the content might significantly reduce
the content discovery as well as delivery latency.

Security: When any new component such as an NRS is introduced in the
ICN architecture, the attack surface may increase. Protection of
the NRS system itself against attacks such as Distributed Denial
of Service (DDoS) and spoofing or alteration of name mapping
records and related signaling messages may be challenging.

5. ICN Architectural Considerations for NRS

This section discusses the various items that can be considered from
the perspective of ICN architecture when employing an NRS system.
These items are related to the registration, resolution, and update
of name mapping records, protocols and messages, and integration with
the routing system.

5.1. Name Mapping Records Registration, Resolution, and Update

When an NRS is integrated in ICN architecture, the functions related
to the registration, resolution, and update of name mapping records
have to be considered. The NRS nodes maintain the name mapping
records and may exist as an overlay network over the ICN routers,
that is, they communicate to each other through ICN routers.
Figure 1 shows the NRS nodes and NRS clients connected through an
underlying network. The NRS nodes should be deployed in such a
manner that an NRS node is always available at a short distance from
an NRS client so that communication latency for the name registration
and resolution requested by the NRS client remains very low. The
name registration, name resolution, and name record update procedures
are briefly discussed below.

+------------+ +------------+
| NRS Node | | NRS Node |
+------------+ +------------+
| |
| |
+------------+ | | +------------+
| NRS Client |--------------------------------------| NRS Client |
+------------+ underlying network +------------+

Figure 1: NRS Nodes and NRS Clients Connected through an
Underlying Network

Name registration: Name registration is performed by the producer
(as an NRS client) when it creates a new content. When a producer
creates content and assigns a name from its name prefix space to
the content, the producer performs the name registration in an NRS
node. Name registration may be performed by an ICN router when
the ICN architecture supports off-path caching or cooperative
caching since involving an NRS may be a good idea for off-path
caching. The ICN routers with forwarder caches do not require
name registration for their cached content because they lie on the
path toward an upstream content store or producer. They will be
hit when a future request is forwarded to the content producer by
an ICN router lying downstream toward the ICN client node.
However, ICN routers performing off-path caching of content must
invoke the name registration procedure so that other ICN routers
can depend on name resolutions to know about the off-path cache
locations. If a content gets cached in many off-path ICN routers,
all of them may register the same content names in the same NRS
node, resulting in multiple registration actions. In this case,
the NRS node adds the new location of the content to the name
record together with the previous locations. In this way, each of
the name records stored in the NRS node may contain multiple
locations of the content. Assigning validity time or a lifetime
of each mapping record may be considered especially for the off-
path caching content and managing mobility.

Name resolution: Name resolution is performed by an NRS client to
obtain the name record from an NRS node by sending a name
resolution request message and getting a response containing the
record. In the name-based ICN routing context, the name
resolution is needed by any ICN router whose forwarding
information base (FIB) does not contain the requested name prefix.
Name resolution may also be performed by the consumer (especially
in the case where the consumer is multihomed) to forward the
content request in a better direction so that it obtains the
content from the nearest cache. If the consumer is single homed,
it may not bother to perform name resolution, instead depending on
either straightforward name-based routing or name resolution by an
upstream ICN router. In this case, the consumer creates the
content request packet containing the content name and forwards to
the nearest ICN router. The ICN router checks its FIB table to
see where to forward the content request. If the ICN router fails
to identify whether the requested content is reachable, it
performs name resolution to obtain the name mapping record and
adds this information to its FIB. The ICN router may also perform
name resolution even before the arrival of a content request to
use the name mapping record to configure its FIB.

Name record update: Name record update is carried out when a content
name mapping record changes, e.g., the content is not available in
one or more of the previous locations. The name record update
includes the substitution and deletion of the name mapping
records. The name record update may take place explicitly by the
exchange of name record update messages or implicitly when a
timeout occurs and a name record is deemed to be invalid. The
implicit update is possible when each record is accompanied by a
lifetime value. The lifetime can be renewed only by the
authoritative producer or node. The cached mapping records get
erased after the lifetime expires unless a lifetime extension
indication is obtained from the authoritative producer.

5.2. Protocols and Semantics

In order to develop an NRS system within a local ICN network domain
or global ICN network domain, new protocols and semantics must be
designed and implemented to manage and resolve names among different
namespaces.

One way of implementing an NRS for CCNx is by extending the basic TLV
format and semantics [RFC8569] [RFC8609]. For instance, name
resolution and response messages can be implemented by defining new
type fields in the Interest and Content Object messages [CCNxNRS].
By leveraging the existing CCNx Interest and Content Object packets
for name resolution and registration, the NRS system can be deployed
with a few ICN protocol changes. However, because of confining the
changes to the basic ICN protocol and semantics, the NRS system may
not be able to exploit more flexible and scalable designs.

On the other hand, an NRS system can be designed independently with
its own protocol and semantics like the NRS system described in
[Hong]. For instance, the NRS protocol and messages can be
implemented by using a RESTful API, and the NRS can be operated as an
application protocol independent of the rest of the ICN protocol.

5.3. Routing System

An NRS reduces the routing complexity of ICN architecture compared to
pure name-based routing. It does so by permitting the routing system
to update the routing table on demand with the help of name records
obtained from NRS. The routing system therefore needs to make name
resolution requests and process the information returned, such as a
prefix, a locator, an off-path-cache pointer, or an alias name,
obtained from the name resolution.

No matter what kind of information is obtained from the name
resolution, as long as it is in the form of a name, the content
request message in the routing system may be reformatted with the
obtained information. In this case, the content name requested
originally by a consumer needs to be involved in the reformatted
content request to check the integrity of the binding between the
name and the requested content. In other words, the information
obtained from the name resolution is used to forward the content
request, and the original content name requested by a consumer is
used to identify the content. Alternatively, the resolved
information may be used to build the routing table.

The information obtained from name resolution may not be in the form
of a name. For example, it may identify tunnel endpoints by IP
address and instead be used to construct an IP protocol tunnel
through which to forward the content request.

6. Conclusion

A Name Resolution Service (NRS) is not a mandatory part in an ICN
architecture, as the majority of ICN architectures use name-based
routing that does not employ a name resolution procedure. However,
such name-based routing in ICN has inherent challenges in enabling a
globally scalable routing system, accommodating producer mobility,
and supporting off-path caching. In order to address these
challenges, an NRS system has been introduced in several ICN
projects. Therefore, this document describes how the ICN
architecture changes when an NRS is utilized and how this affects the
ICN routing system.

The document defines a few terminologies related to an NRS and
explains some inherent challenges of pure name-based routing in ICN
such as routing scalability, producer mobility, and off-path caching.
This document describes how the ICN architecture would change with
respect to procedures, latency, and security when an NRS is utilized.
According to the ICN architectural changes, this document describes
ICN architectural considerations for NRS such as the functions
related to the registration, resolution and update of name mapping
records, protocols and semantics to implement an NRS system, and the
routing system involving the name resolution.

7. IANA Considerations

This document has no IANA actions.

8. Security Considerations

When any new component such as an NRS is introduced in the ICN
architecture, the attack surface increases. The related security
vulnerability issues are discussed below:

Namespace security: In order to deploy an NRS system in ICN
architecture, ICN namespaces, which may be assigned by
authoritative entities, must be securely mapped to the content
publishers and securely managed by them. According to the ICN
research challenges [RFC7927], a new namespace can also provide an
integrity verification function to authenticate its publisher.
The issues of namespace authentication and the mapping among
different namespaces require further investigation.

NRS system security: An NRS requires the deployment of new entities
(e.g., NRS servers) to build distributed and scalable NRS systems.
Thus, the entities, e.g., an NRS server maintaining a mapping
database, could be the focus of attacks by receiving malicious
requests from innumerable adversaries comprising of Denial-of-
Service or Distributed-Denial-of-Service attacks. In addition,
NRS clients in general must trust the NRS nodes in other network
domains to some degree, and communication among them must also be
protected securely to prevent malicious entities from
participating in this communication. The history of name
resolution data requires to be stored and analyzed as in passive
DNS to uncover potential security incidents or discover malicious
infrastructures.

NRS protocol and message security: In an NRS system, the protocols
to generate, transmit, and receive NRS messages related to the
name registration, resolution, and record update should be
protected by proper security mechanisms. Proper security measures
must be provided so that only legitimate nodes can initiate and
read NRS messages. These messages must be secured by integrity
protection and authentication mechanisms so that unauthorized
parties cannot manipulate them when being forwarded through the
network. Security measures to encrypt these messages should also
be developed to thwart all threats to both security and privacy.
Numerous problems similar to the security issues of an IP network
and DNS can affect the overall ICN architecture. The DNS QNAME
minimization type of approach would be suitable for preserving
privacy in the name resolution process. Therefore, security
mechanisms such as accessibility, authentication, etc., for the
NRS system [RFC9138] should be considered to protect not only the
NRS system but also the ICN architecture overall.

9. References

9.1. 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>.

[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>.

[RFC8609] Mosko, M., Solis, I., and C. Wood, "Content-Centric
Networking (CCNx) Messages in TLV Format", RFC 8609,
DOI 10.17487/RFC8609, July 2019,
<https://www.rfc-editor.org/info/rfc8609>.

[RFC9138] Hong, J., You, T., Dong, L., Westphal, C., and B. Ohlman,
"Design Considerations for Name Resolution Service in
Information-Centric Networking (ICN)", RFC 9138,
DOI 10.17487/RFC9138, December 2021,
<https://www.rfc-editor.org/info/rfc9138>.

9.2. Informative References

[Afanasyev]
Afanasyev, A., Yi, C., Wang, L., Zhang, B., and L. Zhang,
"SNAMP: Secure namespace mapping to scale NDN forwarding",
2015 IEEE Conference on Computer Communications Workshops
(INFOCOM WKSHPS), DOI 10.1109/INFCOMW.2015.7179398, April
2015, <https://doi.org/10.1109/INFCOMW.2015.7179398>.

[Bayhan] Bayhan, S., Ott, J., Kangasharju, J., Sathiaseelan, A.,
and J. Crowcroft, "On Content Indexing for Off-Path
Caching in Information-Centric Networks", ACM ICN,
DOI 10.1145/2984356.2984372, September 2016,
<https://doi.org/10.1145/2984356.2984372>.

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

[CCNxNRS] Hong, J., You, T., and Y. Hong, "CCNx Extension for Name
Resolution Service", Work in Progress, Internet-Draft,
draft-hong-icnrg-ccnx-nrs-02, 2 July 2018,
<https://datatracker.ietf.org/doc/html/draft-hong-icnrg-
ccnx-nrs-02>.

[Dannewitz]
Dannewitz, C., Kutscher, D., Ohlman, B., Farrell, S.,
Ahlgren, B., and H. Karl, "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>.

[Dannewitz2]
Dannewitz, C., D'Ambrosio, M., and V. Vercellone,
"Hierarchical DHT-based name resolution for information-
centric networks", Computer Communications vol. 36, issue
7, DOI 10.1016/j.comcom.2013.01.014, April 2013,
<https://doi.org/10.1016/j.comcom.2013.01.014>.

[Hong] Hong, J., Chun, W., and H. Jung, "Demonstrating a Scalable
Name Resolution System for Information-Centric
Networking", ACM ICN, DOI 10.1145/2810156.2812617,
September 2015, <https://doi.org/10.1145/2810156.2812617>.

[MF] Future Internet Architecture (FIA), "MobilityFirst",
<http://mobilityfirst.cs.umass.edu/>.

[NDN] NDN, "Named Data Networking", September 2010,
<https://www.named-data.net>.

[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>.

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

[Zhang2] Zhang, Y., Afanasyev, A., Burke, J., and L. Zhang, "A
Survey of Mobility Support in Named Data Networking",
Named Data Networking, Workshop on Name-Oriented Mobility:
Architecture, Algorithms and Applications (NOM), April
2016.

Acknowledgements

The authors would like to thank Dave Oran (ICNRG Co-chair) for very
useful reviews and comments, which helped to immeasurably improve
this document.

Authors' Addresses

Jungha Hong
ETRI
Yuseung-Gu
218 Gajeong-ro
Daejeon
34129
Republic of Korea
Email: [email protected]

Tae-Wan You
ETRI
Yuseung-Gu
218 Gajeong-ro
Daejeon
34129
Republic of Korea
Email: [email protected]

Ved Kafle
NICT
Koganei
4-2-1 Nukui-Kitamachi, Tokyo
184-8795
Japan
Email: [email protected]