Internet Research Task Force (IRTF) D. Kutscher, Ed.
Request for Comments: 7927 NEC
Category: Informational S. Eum
ISSN: 2070-1721 Osaka University
K. Pentikousis
Travelping
I. Psaras
UCL
D. Corujo
Universidade de Aveiro
D. Saucez
INRIA
T. Schmidt
HAW Hamburg
M. Waehlisch
FU Berlin
July 2016
Information-Centric Networking (ICN) Research Challenges
Abstract
This memo describes research challenges for Information-Centric
Networking (ICN), an approach to evolve the Internet infrastructure
to directly support information distribution by introducing uniquely
named data as a core Internet principle. Data becomes independent
from location, application, storage, and means of transportation,
enabling or enhancing a number of desirable features, such as
security, user mobility, multicast, and in-network caching.
Mechanisms for realizing these benefits is the subject of ongoing
research in the IRTF and elsewhere. This document describes current
research challenges in ICN, including naming, security, routing,
system scalability, mobility management, wireless networking,
transport services, in-network caching, and network management.
This document is a product of the IRTF Information-Centric Networking
Research Group (ICNRG).
Kutscher, et al. Informational [Page 1]RFC 7927 ICN Challenges July 2016
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 a
candidate 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
http://www.rfc-editor.org/info/rfc7927.
Copyright Notice
Copyright (c) 2016 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
(http://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.
Kutscher, et al. Informational [Page 2]
RFC 7927 ICN Challenges July 2016
Table of Contents
1. Introduction ....................................................4
2. Problems with Host-Centric Communications .......................4
3. ICN Terminology and Concepts ....................................6
3.1. Terminology ................................................6
3.2. Concepts ...................................................6
4. ICN Research Challenges .........................................8
4.1. Naming, Data Integrity, and Data Origin Authentication .....8
4.2. Security ..................................................10
4.2.1. Data Integrity and Origin Authentication ...........10
4.2.2. Binding NDOs to Real-World Identities ..............11
4.2.3. Access Control and Authorization ...................12
4.2.4. Encryption .........................................13
4.2.5. Traffic Aggregation and Filtering ..................13
4.2.6. State Overloading ..................................13
4.2.7. Delivering Data Objects from Replicas ..............14
4.2.8. Cryptographic Robustness ...........................14
4.2.9. Routing and Forwarding Information Bases ...........15
4.3. Routing and Resolution System Scalability .................15
4.3.1. Route-By-Name Routing ..............................15
4.3.2. Lookup-By-Name Routing .............................16
4.3.3. Hybrid Routing .....................................17
4.4. Mobility Management .......................................18
4.5. Wireless Networking .......................................20
4.6. Rate and Congestion Control ...............................22
4.7. In-Network Caching ........................................24
4.7.1. Cache Placement ....................................24
4.7.2. Content Placement: Content-to-Cache Distribution ...25
4.7.3. Request-to-Cache Routing ...........................26
4.7.4. Staleness Detection of Cached NDOs .................26
4.7.5. Cache Sharing by Multiple Applications .............27
4.8. Network Management ........................................27
4.9. ICN Applications ..........................................29
4.9.1. Web Applications ...................................30
4.9.2. Video Streaming and Download .......................30
4.9.3. Internet of Things .................................31
5. Security Considerations ........................................32
6. Informative References .........................................32
Acknowledgments ...................................................37
Authors' Addresses ................................................37
Kutscher, et al. Informational [Page 3]RFC 7927 ICN Challenges July 2016
1. Introduction
Information-Centric Networking (ICN) is an approach to evolve the
Internet infrastructure to directly support accessing Named Data
Objects (NDOs) as a first-order network service. Data objects become
independent of location, application, storage, and means of
transportation, allowing for inexpensive and ubiquitous in-network
caching and replication. The expected benefits are improved
efficiency and security, better scalability with respect to
information/bandwidth demand, and better robustness in challenging
communication scenarios.
ICN concepts can be deployed by retooling the protocol stack: name-
based data access can be implemented on top of the existing IP
infrastructure, e.g., by allowing for named data structures,
ubiquitous caching, and corresponding transport services, or it can
be seen as a packet-level internetworking technology that would cause
fundamental changes to Internet routing and forwarding. In summary,
ICN can evolve the Internet architecture towards a network model
based on named data with different properties and different services.
This document presents the ICN research challenges that need to be
addressed in order to achieve these goals. These research challenges
are seen from a technical perspective, although business
relationships between Internet players will also influence
developments in this area. We leave business challenges for a
separate document, however. The objective of this memo is to
document the technical challenges and corresponding current
approaches and to expose requirements that should be addressed by
future research work.
This document has been reviewed, commented on, and discussed
extensively for nearly two years by the vast majority of ICNRG
members, which certainly exceeds 100 individuals. It is the
consensus of ICNRG that the research challenges described in this
document should be published in the IRTF stream of the RFC series.
This document does not constitute a standard.
2. Problems with Host-Centric Communications
The best current practice to manage the above-mentioned growth in
terms of data volume and number of devices is to increase
infrastructure investment, employ application-layer overlays that
cache content such as Content Distribution Networks (CDNs) and Peer-
to-Peer (P2P) applications, provide location-independent access to
data, and optimize its delivery. In principle, such platforms
Kutscher, et al. Informational [Page 4]
RFC 7927 ICN Challenges July 2016
provide a service model of accessing named data objects (NDOs) (e.g.,
replicated web resources in data centers) instead of a host-to-host
packet delivery service model.
However, since this functionality resides in overlays only, the full
potential of content distribution platforms cannot be leveraged as
the network is not aware of data requests and data transmissions.
This has the following impact:
o Data traffic typically follows sub-optimal paths as it is
effectively routed, depending on the overlay topology instead of
the Internet-layer topology.
o Network capabilities, such as multicast and broadcast, are largely
underutilized or not employed at all. As a result, request and
delivery for the same object have to be made multiple times.
o Overlays typically require significant infrastructure support,
e.g., authentication portals, content storage, and applications
servers, making it often impossible to establish local, direct
communication.
o The forwarding layer cannot cooperate with transport-layer
functions, so sometimes useful functionality such as local
retransmission and local rate control have to be implemented with
TCP proxies or other intermediaries.
o Provenance validation uses host authentication today. As such,
even if there are locally cached copies available, it is normally
not easily possible to validate their authenticity.
o Many applications follow their own approach to caching,
replication, transport, and authenticity validation (if at all),
although they all share similar models for accessing named data
objects in the network.
Host-centric communication systems restrict applications to data
transfer between end-hosts only. Naming data directly provides a
powerful "hook" for applications to exploit and natively support
multi-party communication, e.g., multi-source/multi-destination
communication and a ubiquitous information ecosystem that is not
restricted to end-host addresses.
Kutscher, et al. Informational [Page 5]RFC 7927 ICN Challenges July 2016
3. ICN Terminology and Concepts
3.1. Terminology
Information-Centric Networking (ICN): A concept for communicating in
a network that provides accessing named data objects as a first
order service. See Section 3.2 for details.
Named Data Object (NDO): Addressable data unit in an information-
centric network that can represent a collection of bytes or a
piece of information. In ICN, each data object has a name bound
to it, and there are typically mechanisms to secure (and validate)
this binding. Different ICN approaches have different concepts
for how to map NDOs to individual units of transport, e.g., chunks
and segments. Sometimes smaller units may be represented by NDOs
themselves. Within the context of this document, an NDO is any
named data object that can be requested from the network, and we
do not consider sub-units below the NDO level. In this document,
we often use the terms "NDO" and "data object" interchangeably.
Requestor: Entity in an ICN network that is sending a request for a
named data object to the network.
Publisher: Entity in an ICN network that publishes an NDO to the
network, so that corresponding requests can reach the publisher.
The publisher does not need to be identical to the actual creator,
for example, a publisher could provide the service of hosting NDOs
on behalf of the actual creators/owners.
3.2. Concepts
Fundamentally, ICN provides access to named data as a first-order
network service, i.e., the network is able to serve requests to named
data natively. That means network nodes can receive requests for
named data and act as necessary, for example, by forwarding the
request to a suitable next hop. Consequently, the network processes
requests for named data objects (and corresponding responses)
natively. Every network node on a path is enabled to perform
forwarding decisions, cache objects, etc. This enables the network
to forward such requests on optimal paths, employing the best
transmission technologies at every node, e.g., broadcast/multicast
transmission in wireless networks to avoid duplicate transmission of
both requests and responses.
In ICN, there is a set of common concepts and node requirements
beyond this basic service model. Naming data objects is a key
concept. In general, ICN names represent neither network nodes nor
interfaces -- they represent NDOs independently of their location.
Kutscher, et al. Informational [Page 6]RFC 7927 ICN Challenges July 2016
Names do play a key role in forwarding decisions and are used for
matching requests to responses: in order to provide better support
for accessing copies of NDOs regardless of their location, it is
important to be able to validate that a response actually delivers
the bits that correspond to an original request for named data.
Name-content binding validation is a fundamental security service in
ICN, and this is often achieved by establishing a verifiable binding
between the object name and the actual object or an identity that has
created the object. ICN can support other security services, such as
provenance validation and encryption, depending on the details of
naming schemes, object models, and assumptions on infrastructure
support. Security services such as name-content binding validation
are available to any node, i.e., not just the actual requestors.
This is an important feature for enabling ingress gateways to check
object authenticity to prevent denial-of-service attacks.
Based on these fundamental properties, it is possible to leverage
network storage ubiquitously: every ICN node can cache data objects
and respond to requests for such objects -- it is not required to
validate the authenticity of the node itself since name-content
bindings can be validated. Ubiquitous in-network storage can be used
for different purposes: it can enable sharing, i.e., the same object
copy can be delivered to multiple users/nodes as in today's proxy
caches and CDNs. It can also be used to make communication more
robust (and perform better) by enabling the network to answer
requests from local caches (instead of from origin servers). In case
of disruption (message not delivered), a node can resend the request,
and it could be answered by an on-path cache, i.e., on the other side
of the disrupted link. The network itself would be able to send
local retransmissions, which enables shorter round-trip times and the
offloading of origin servers and other parts of the network.
ICN potentially retrieves segments of NDOs from multiple data
sources, so only a requestor can determine the completion of a
retrieval process, i.e., the retrieval of NDOs or individual segments
is typically controlled by a requestor. For this reason, ICN
transport protocols are typically based on a receiver-driven
mechanism: requestors can control message sending rates by regulating
the request sending rate (assuming that every response message has to
be triggered by a request message). Retransmission would be achieved
by resending requests, e.g., after a timeout. Because objects can be
replicated, object transmission and transport sessions would not
necessarily have end-to-end semantics: requests can be answered by
caches, and a node can select one or multiple next-hop destinations
for a particular request depending on configuration, observed
performance, or other criteria.
Kutscher, et al. Informational [Page 7]
RFC 7927 ICN Challenges July 2016
This receiver-driven communication model potentially enables new
interconnection and business models: a request for named data can be
linked to an interest of a requestor (or requesting network) in data
from another peer, which could suggest modeling peering agreements
and charging accordingly.
4. ICN Research Challenges
4.1. Naming, Data Integrity, and Data Origin Authentication
Naming data objects is as important for ICN as naming hosts is for
today's Internet. Fundamentally, ICN requires unique names for
individual NDOs, since names are used for identifying objects
independently of their location or container. In addition, since
NDOs can be cached anywhere, the origin cannot be trusted anymore,
hence the importance of establishing a verifiable binding between the
object and its name (name-data binding validation) so that a
requestor can be sure that the received bits do correspond to the NDO
originally requested (data integrity). Data origin authentication is
a different security service that can be related to naming, i.e.,
verifying that an NDO has indeed been published by a publisher (that
could be identified by a name prefix).
The above functions are fundamentally required for the information-
centric network to work reliably; otherwise, neither network elements
nor requestors can trust object authenticity. Lack of this trust
enables several attacks, including DoS attacks, by injecting spoofed
content into the network. There are different ways to use names and
cryptography to achieve the desired functions [ICNNAMING]
[ICNSURVEY], and there are different ways to manage namespaces
correspondingly.
Two types of naming schemes have been proposed in the ICN literature:
hierarchical and flat namespaces. For example, a hierarchical scheme
may have a structure similar to current URIs, where the hierarchy is
rooted in a publisher prefix. Such hierarchy enables aggregation of
routing information, improving scalability of the routing system. In
some cases, names are human readable, which makes it possible for
users to manually type in names, reuse, and, to some extent, map the
name to the user intent.
The second general class of naming schemes enables verifying the
object's name-data integrity without requiring a Public Key
Infrastructure (PKI) or other third party to first establish trust in
the key. This is achieved, e.g., by binding the hash of the NDO
content to the object's name. For instance, this can be done by
directly embedding the hash of the content in the name. Another
option is an indirect binding, which embeds the public key of the
Kutscher, et al. Informational [Page 8]
RFC 7927 ICN Challenges July 2016
publisher in the name and signs the hash of the content with the
corresponding private key. The resulting names are typically non-
hierarchical, or flat, although the publisher field could be employed
to create a structure that could facilitate route aggregation.
There are several design trade-offs for ICN naming that affect
routing and security. Hash-based names are not human readable nor
hierarchical. They can, however, provide some structure for
aggregation, for instance, a name part corresponding to a publisher.
In hash-based names with indirect binding, the key of the publisher
is bound to the name of NDO, so when a user receives, e.g., the
triplet, namely (data, key, signature), the receiving entity can
verify that the NDO has been generated by the possessor of the
private/public key pair and that the NDO has not been changed in
transit (data integrity). This can be done by cryptographically
hashing the received key and the name of the NDO, and comparing it
with the received hashed key. Then, the key can be used to verify
the signature.
Data origin authentication can be achieved by validating signatures
based on public key cryptography about an NDO's name and content. In
order to ascertain data integrity and origin authenticity with such
an approach, a PKI-like system is required that would allow linking
the corresponding public key to a trust chain.
Research challenges specific to naming include:
o Naming static data objects can be performed by using content
hashes as part of object names, so that publishers can calculate
the hash over existing data objects and requestors, and any ICN
node can validate the name-content binding by recalculating the
hash and comparing it to the name (component). [RFC6920]
specifies a concrete naming format for this.
o Naming dynamic objects refers to use cases where the name has to
be generated before the object is created. For example, this
could be the case for live streaming, when a publisher wants to
make the stream available by registering stream chunk names in the
network. One approach to this can be hash-based names with
indirect binding as described above.
o Requestor privacy protection can be a challenge in ICN as a direct
consequence of the accessing-named-data-objects paradigm: if the
network can "see" requests and responses, it can also log request
history for network segments or individual users, which can be
undesirable, especially since names are typically expected to be
Kutscher, et al. Informational [Page 9]RFC 7927 ICN Challenges July 2016
long-lived. That is, even if the name itself does not reveal much
information, the assumption is that the name can be used to
retrieve the corresponding data objects in the future.
o Updating and versioning NDOs can be challenging because it can
contradict fundamental ICN assumptions: if an NDO can be
replicated and stored in in-network storage for later retrieval,
names have to be long-lived and the name-content binding must not
change; updating an object (i.e., changing the content without
generating a new name) is not possible. Versioning is one
possible solution but requires a naming scheme that supports it
(and a way for requestors to learn about newer and older
versions).
o Managing accessibility can also be a challenge. In ICN, the
general assumption is to enable ubiquitous access to NDOs, but
there can be relevant use cases where access to objects should be
restricted, for example, to a specific user group. There are
different approaches for this, such as object encryption
(requiring key distribution and related mechanisms) or the concept
of scopes, e.g., based on names that can only be used/resolved
under some constraints.
4.2. Security
Security is an active research field in ICN. This section provides
an overview of important security features and corresponding
challenges that are related to shifting to information-centric
communications. Some challenges are well understood, and there are
(sometimes multiple different) approaches to address them, whereas
other challenges are active research and engineering topics.
4.2.1. Data Integrity and Origin Authentication
As mentioned in Section 4.1, data integrity verification is an
important ICN feature, since NDOs are retrieved not only from an
original copy holder but also from any caching point. Hence, the
communication channel endpoints to retrieve NDOs are not trustable
anymore, and solutions widely used today such as Transport Layer
Security (TLS) [RFC5246] cannot be used as a general solution. Since
data objects can be maliciously modified, ICN should provide
receivers with a security mechanism to verify the integrity of the
data object, and there are different ways to achieve this.
Kutscher, et al. Informational [Page 10]RFC 7927 ICN Challenges July 2016
An efficient approach for static NDOs is providing a name-content-
binding by hashing an NDO and using the hash as a part of the
object's name. [RFC6920] provides a mechanism and a format for
representing a digest algorithm and the actual digest in a name
(amongst other information).
For dynamic objects where it is desirable to refer to an NDO by name
before the object has been created, public key cryptography is often
applied, i.e., every NDO would be authenticated by means of a
signature performed by the data object publisher so that any data
object consumer can verify the validity of the data object based on
the signature. However, in order to verify the signature of an
object, the consumer must know the public key of the entity that
signed the object.
Data origin authentication, i.e., verifying that an NDO has indeed
been published by a publisher, requires a secure binding of an NDO
name to a publisher identity -- this is also typically implemented
using public key cryptography, i.e., by requiring a receiver to
verify digital signatures that are part of received messages.
One research challenge is then to support a mechanism to distribute
the publisher's public keys to the consumers of data objects. There
are two main approaches to achieve this: one is based on an external
third-party authority such as hierarchical Public Key Infrastructure
(PKI) (see [RFC5280] for a description of hierarchical PKI), and the
other is to adapt a hash-based scheme with indirect binding. The
former, as the name implies, depends on an external third party
authority to distribute the public key of the publisher for the
consumers. In a hash-based scheme with indirect binding, the public
key (or a hash of it) would be used as part of the name -- which is
sufficient to validate the data integrity.
In cases where information about the origin of a data object is not
available by other means, the object itself would have to incorporate
the necessary information to determine the object publisher, for
example, with a certificate, that can be validated through the PKI.
Once the certificate is authenticated, its public key can be used to
authenticate the signed data object itself.
4.2.2. Binding NDOs to Real-World Identities
In addition to validating NDO authenticity, it is still important to
bind real-world identities, e.g., a publisher identity, to objects,
so that a requestor can verify that a received object was actually
published by a certain source.
Kutscher, et al. Informational [Page 11]
RFC 7927 ICN Challenges July 2016
With hash-based names, real-world identity bindings are not
intrinsically established: the name provides the hash of the NDO or
of the public key that was used to sign the NDO. There needs to be
another binding to a real-world identity if that feature is
requested.
If the object name directly provides the publisher name and if that
name is protected by a certificate that links to a PKI-like trust
chain, the object name itself can provide an intrinsic binding to a
real-world identity.
Binding between NDOs and real-world identities is essential, but
there is no universal way to achieve it as it is all intrinsic to a
particular ICN approach.
4.2.3. Access Control and Authorization
Access control and authorization is a challenge in ICN, because of
the lack of user-to-server authentication in the fundamental
communication model based on named data.
All ICN entities are capable of delivering NDOs on demand due to
their in-network caching function. In such an environment,
traditional access control schemes based on Access Control List (ACL)
are ill-suited since widely distributed ICN entities have to maintain
an identical control policy over NDOs for each consumer, which is
prohibited due to computational overhead and privacy issues. There
are two complementary approaches to address the issues:
1. Separated approach: access control service from a third party
that is independent from ICN entities. Due to the clear
separation, ICN entities are free from computational overhead to
determine the accessibility of NDOs by consumers; also, consumers
can secure their privacy through the independent authorization
entity [ACCESS-CTL-DEL]. Relevant challenges to this approach
include reducing the authorization delay (when communicating to
the access control provider) and currency and consistency of
access control information (when access control lists are
distributed).
2. Integrated approach: access control service from ICN entities.
This mechanism is often based on content encryption and key
distribution [ENCRYPTION-AC]. As mentioned previously, this
approach suffers from prohibitive overhead for ICN entities due
to the process of key verification. While key distribution is
challenging per se, this approach is beneficial in a way that
NDOs can be retrieved without the help of an external access
control provider. Challenges to this approach include:
Kutscher, et al. Informational [Page 12]RFC 7927 ICN Challenges July 2016
1. applying an access control mechanism for dynamic NDOs in in-
network caches in a timely manner;
2. providing consumers with the different levels of
accessibility to individual NDOs in a scalable manner; and
3. managing key revocation and similar PKI management functions.
4.2.4. Encryption
In ICN, NDOs can be encrypted to implement access control (only
consumers in possession of corresponding decryption keys can access
the content) or privacy (same approach). Distributing and managing
the corresponding keys as well as providing usable interfaces to
applications and human users are challenges and the subject of
ongoing work.
In principle, the challenges are similar to those of broadcast/media
distribution, and similar approaches (combing symmetric with public
key cryptography) are being investigated [NDN-CTL-SHARING].
4.2.5. Traffic Aggregation and Filtering
One request message to retrieve a data object can actually aggregate
requests coming from several consumers. This aggregation of requests
reduces the overall traffic but makes per-requestor filtering harder.
The challenge in this case is to provide a mechanism that allows
request aggregation and per-requestor filtering. A possible solution
is to indicate the set of requestors in the aggregated request such
that the response can indicate the subset of requestors allowed to
access the data object. However, this solution requires
collaboration from other nodes in the network and is not suitable for
caching. Another possible solution is to encrypt data objects and
ensure that only authorized consumers can decrypt them. This
solution does not preclude caching and does not require collaboration
from the network. However, it implies a mechanism to generate group
keys (e.g., different private keys can be used to decrypt the same
encrypted data object) [CHAUM].
4.2.6. State Overloading
ICN solutions that implement state on intermediate routers for
request routing or forwarding (e.g., Content-Centric Networking (CCN)
[CCN]) are subject to denial-of-service attacks from overloading or
superseding the internal state of a router (e.g., "interest flooding"
[BACKSCATTER]). Additionally, stateful forwarding can enable attack
vectors such as resource exhaustion or complexity attacks to the
routing infrastructure. The challenge is then to provision routers
Kutscher, et al. Informational [Page 13]RFC 7927 ICN Challenges July 2016
and construct internal state in a way that alleviates sensibility to
such attacks. The problem becomes even harder if the protocol does
not provide information about the origin of messages. Without
origin, it is a particular challenge to distinguish between regular
(intense) use and misuse of the infrastructure.
4.2.7. Delivering Data Objects from Replicas
A common capability of ICN solutions is data replication and in-
network storage. Delivering replicated data objects from caches
decouples content consumption from data sources, which leads to a
loss of control on (1) content access and (2) content dissemination.
In a widely distributed, decentralized environment like the Internet,
this raises several challenges.
One group of challenges is related to content management. Without
access control, a content provider loses the means to count and
survey content consumption, to limit access scopes, to control or
know about the number of copies of its data in the network, or to
withdraw earlier publications reliably. Any non-cooperative or
desynchronized data cache may hinder an effective content management
policy.
Another group of challenges arises from potential traffic
amplifications in the decoupled environment. ICN solutions that
attempt to retrieve content from several replicas in parallel, or
decorrelated network routing states, but also distributed attackers
may simultaneously initiate the transmission of content from multiple
replicas towards the same destination (e.g., "initiated overloads" or
"blockades" [BACKSCATTER]). Methods for mitigating such threats need
rigorous forwarding checks that require alignment with caching
procedures (e.g., on-path or off-path).
4.2.8. Cryptographic Robustness
Content producers sign their content to ensure the integrity of data
and to allow for data object authentication. This is a fundamental
requirement in ICN due to distributed caching. Publishers, who
massively sign content, which is long-lived, offer time and data to
an attacker for comprising cryptographic credentials. Signing a
large amount of data eases common attacks that try to breach the key
of the publisher. Based on this observation, the following research
challenges emerge:
Kutscher, et al. Informational [Page 14]
RFC 7927 ICN Challenges July 2016
o To which extent does the content publication model conflict with
the cryptographic limitations?
o How can we achieve transparent re-signing without introducing
additional cryptographic weaknesses or key management overhead?
In general, ICN implementations should be designed considering the
guidelines provided by [RFC7696], especially regarding cryptographic
algorithm agility, for example, [RFC6920] specifies a naming scheme
for hash-based names that was designed to support algorithm agility.
4.2.9. Routing and Forwarding Information Bases
In information-centric networks, one attack vector is to increase the
size of routing and forwarding information bases at ICN nodes, i.e.,
attacking routing scalability in networks that rely on routing by
name. This is an intrinsic ICN security issue: possible mitigation
approaches include combining routing information authenticity
validation with filtering (e.g., maximum de-aggregation level
whenever applicable, blacklists, etc.,).
4.3. Routing and Resolution System Scalability
ICN routing is a process that finds an NDO based on its name
initially provided by a requestor. ICN routing may comprise three
steps: (1) name resolution, (2) discovery, and (3) delivery. The
name resolution step translates the name of the requested NDO into
its locator. The discovery step routes the request to the data
object based on its name or locator. The last step (delivery) routes
the data object back to the requestor. Depending on how these steps
are combined, ICN routing schemes can be categorized as Route-By-Name
Routing (RBNR), Lookup-By-Name Routing (LBNR), and Hybrid Routing
(HR) as discussed in the following subsections.
4.3.1. Route-By-Name Routing
RBNR omits the first name resolution step as the name of the NDO is
directly used to route the request to the data object. Therefore,
routing information for each data object has to be maintained in the
routing table. Since the number of data objects is very large
(estimated as 10^11 back in 2007 [DONA], but this may be
significantly larger than that, e.g., 10^15 to 10^22), the size of
routing tables becomes a concern, as it can be proportional to the
number of data objects unless an aggregation mechanism is introduced.
On the other hand, RBNR reduces overall latency and simplifies the
routing process due to the omission of the resolution process. For
the delivery step, RBNR needs another identifier (ID) of either host
or location to forward the requested data object back to the
Kutscher, et al. Informational [Page 15]RFC 7927 ICN Challenges July 2016
requestor. Otherwise, an additional routing mechanism has to be
introduced, such as breadcrumbs routing [BREADCRUMBS], in which each
request leaves behind a trail of breadcrumbs along its forwarding
path, and then the response is forwarded back to the requestor
consuming the trail.
Challenges specific to RBNR include:
o How can we aggregate the names of data objects to reduce the
number of routing entries?
o How does a user learn the name that is designed for aggregation by
the provider? For example, although we name our contribution as
"ICN research challenges", the IRTF (provider) may want to change
the name to "/IETF/IRTF/ICN/Research challenges" for aggregation.
In this case, how does a user learn the name "/IETF/IRTF/ICN/
Research challenges" to retrieve the contribution initially named
"ICN research challenges" without any resolution process?
o Without introducing the name aggregation scheme, can we still
achieve scalable routing by taking advantage of topological
structure and distributed copies? For example, would employing
compact routing [COMPACT], random walk [RANDOM], or greedy routing
[GREEDY] work at the Internet scale?
o How can we incorporate copies of a data object in in-network
caches in this routing scheme?
o Breadcrumbs routing implies a symmetric path for ICN request and
response delivery. Some network configurations and link types
prohibit symmetric path forwarding, so it would be challenging to
interconnect such networks to an infrastructure based on
breadcrumbs routing. For example, certain forwarding strategies
in Delay-Tolerant Networking (DTN) [RFC4838] are employing
opportunistic forwarding where responses cannot be assumed to
travel the same path as requests.
4.3.2. Lookup-By-Name Routing
LBNR uses the first name resolution step to translate the name of the
requesting data object into its locator. Then, the second discovery
step is carried out based on the locator. Since IP addresses could
be used as locators, the discovery step can depend on the current IP
infrastructure. The delivery step can be implemented similarly to IP
routing. The locator of the requestor is included in the request
message, and then the requested data object is delivered to the
requestor based on the locator. An instantiation of LBNR is [MDHT].
Kutscher, et al. Informational [Page 16]RFC 7927 ICN Challenges July 2016
Challenges specific to LBNR include:
o How can we build a scalable resolution system that provides:
* Fast lookup: Mapping the name of a data object to its locators
(copies as well).
* Fast update: The location of a data object is expected to
change frequently. Also, multiple data objects may change
their locations at the same time, e.g., data objects in a
laptop.
o How can we incorporate copies of a data object in in-network
caches in this routing scheme?
4.3.3. Hybrid Routing
HR combines RBNR and LBNR to benefit from their advantages. Within a
single administrative domain, e.g., an ISP, where scalability issues
can be addressed with network planning, RBNR can be adopted to reduce
overall latency by omitting the resolution process. On the other
hand, LBNR can be used to route between domains that have their own
prefix (locator).
For instance, a request message initially includes the name of the
NDO for the operation of RBNR and is forwarded to a cached copy of
the NDO or the original server. When the request message fails to
find a routing entry in the router, a name resolution step kicks in
to translate the name into its locator before forwarding the request
message based on the retrieved locator.
Challenges specific to HR are:
o How can we design a scalable mapping system that, given the name
of the NDO, should return a destination domain locator so that a
user request can be encapsulated and forwarded to the domain?
o How can the mapping information be secured to prevent a malicious
router from hijacking the request message by chaining its locator?
o How can the bind between the name and the content of the NDO be
maintained for the verification of its origin and integrity when
the name changes due to the retrieved locator?
Kutscher, et al. Informational [Page 17]RFC 7927 ICN Challenges July 2016
4.4. Mobility Management
Mobility management has been an active field in host-centric
communications for more than two decades. In IETF in particular,
starting with [RFC2002], a multitude of enhancements to IP have been
standardized aiming to "allow transparent routing of IP datagrams to
mobile nodes in the Internet" [RFC5944]. In a nutshell, mobility
management for IP networks is locator-oriented and relies on the
concept of a mobility anchor as a foundation for providing always-on
connectivity to mobile nodes (see [MMIN]). Other standards
organizations, such as 3GPP, have followed similar anchor-based
approaches. Traffic to and from the mobile node must flow through
the mobility anchor, typically using a set of tunnels, enabling the
mobile node to remain reachable while changing its point of
attachment to the network.
Needless to say, an IP network that supports node mobility is more
complex than one that does not, as specialized network entities must
be introduced in the network architecture. This is reflected in the
control plane as well, which carries mobility-related signaling
messages, establishes and tears down tunnels, and so on. While
mobile connectivity was an afterthought in IP, in ICN, this is
considered a primary deployment environment. Most, if not all, ICN
proposals consider mobility from the very beginning, although at
varying levels of architectural and protocol detail. That said, no
solution has so far come forward with a definite answer on how to
handle mobility in ICN using native primitives. In fact, we observe
that mobility appears to be addressed on an ICN proposal-specific
basis. That is, there is no single paradigm solution, akin to
tunneling through a mobility anchor in host-centric networking, that
can be applied across different ICN proposals. For instance,
although widely deployed mobile network architectures typically come
with their own network entities and associated protocols, they follow
the same line of design with respect to managing mobility. This
design thinking, which calls for incorporating mobility anchors,
permeates in the ICN literature too.
However, employing mobility anchors and tunneling is probably not the
best way forward in ICN research for mobile networking.
Fundamentally, this approach is anything but information-centric and
location-independent. In addition, as argued in [SEEN], current
mobility management schemes anchor information retrieval not only at
a specific network gateway (e.g., home agent in Mobile IP) but also
at a specific correspondent node due to the end-to-end nature of
host-centric communication. However, once a change in the point of
attachment occurs, information retrieval from the original
"correspondent node" may no longer be optimal. This was shown in
[MANI], for example, where a simple mechanism that triggers the
Kutscher, et al. Informational [Page 18]
RFC 7927 ICN Challenges July 2016
discovery of new retrieval providers for the same data object,
following a change in the point of attachment, clearly outperforms a
tunnel-based approach like Mobile IP in terms of object download
times. The challenge here is how to capitalize on location
information while facilitating the use of ICN primitives, which
natively support multicast and anycast.
ICN naming and name resolution, as well as the security features that
come along, should natively support mobility. For example, CCN [CCN]
does not have the restriction of spanning tree routing, so it is able
to take advantage of multiple interfaces or adapt to the changes
produced by rapid mobility (i.e., there is no need to bind a layer 3
address with a layer 2 address). In fact, client mobility can be
simplified by allowing requests for new content to normally flow from
different interfaces or through newly connected points of attachment
to the network. However, when the node moving is the (only) content
source, it appears that more complex network support might be
necessary, including forwarding updates and cache rebuilding. A case
in point is a conversation network service, such as a voice or video
call between two parties. The requirements in this case are more
stringent when support for seamless mobility is required, especially
when compared to content dissemination that is amenable to buffering.
Another parameter that needs to be paid attention to is the impact of
using different wireless access interfaces based on different
technologies, where the performance and link conditions can vary
widely depending of numerous factors.
In host-centric networking, mobility management mechanisms ensure
optimal handovers and (ideally) seamless transition from one point of
attachment to another. In ICN, however, the traditional meaning of
"point of attachment" no longer applies as communication is not
restrained by location-based access to data objects. Therefore, a
"seamless transition" in ICN ensures that content reception continues
without any perceptible change from the point of view of the ICN
application receiving that content. Moreover, this transition needs
to be executed in parallel with ICN content identification and
delivery mechanisms, enabling scenarios such as preparation of the
content delivery process at the target connectivity point prior to
the handover (to reduce link switch disturbances). Finally, these
mobility aspects can also be tightly coupled with network management
aspects, in respect to policy enforcement, link control, and other
parameters necessary for establishing the node's link to the network.
In summary, the following research challenges for ICN mobility
management can be derived:
o How can mobility management take full advantage of native ICN
primitives?
Kutscher, et al. Informational [Page 19]RFC 7927 ICN Challenges July 2016
o How do we avoid the need for mobility anchors in a network that by
design supports multicast, anycast, and location-independent
information retrieval?
o How can content retrieval mechanisms interface with specific link
operations, such as identifying which links are available for
certain content?
o How can mobility be offered as a service that is only activated
when the specific user/content/conditions require it?
o How can mobility management be coordinated between the node and
the network for optimization and policing procedures?
o How do we ensure that managing mobility does not introduce
scalability issues in ICN?
o How will the name resolution process be affected by rapid
topological changes when the content source itself is mobile?
4.5. Wireless Networking
Today, all layer 2 (L2) wireless network radio access technologies
are developed with a clear assumption in mind: the waist of the
protocol stack is IP, and it will be so for the foreseeable future.
By fixing the protocol stack waist, engineers can answer a large set
of questions, including how to handle conversational traffic (e.g.,
voice calls) vs. web traffic, how to support multicast, and so on, in
a rather straightforward manner. Broadcast, on the other hand, which
is inherent in wireless communication, is not fully taken advantage
of. On the contrary, researchers are often more concerned about
introducing mechanisms that ensure that "broadcast storms" do not
take down a network. The question of how can broadcast better serve
ICN needs has yet to be thoroughly investigated.
Wireless networking is often intertwined with mobility, but this is
not always the case. In fact, empirical measurements often indicate
that many users tend to connect (and remain connected) to a single
Wi-Fi access point for considerable amounts of time. A case in
point, which is frequently cited in different variations in the ICN
literature, is access to a document repository during a meeting. For
instance, in a typical IETF working group meeting, a scribe takes
notes, which are uploaded to a centralized repository (see Figure 1).
Subsequently, each meeting participant obtains a copy of the document
on their own devices for local use, annotation, and sharing with
colleagues that are not present at the meeting. Note that in this
example, there is no node mobility and that it is not important
Kutscher, et al. Informational [Page 20]RFC 7927 ICN Challenges July 2016
whether the document with the notes is uploaded in one go at the end
of the session or in a streaming-like fashion as is typical today
with online (cloud-based) document processing.
+---------------------+
| Document Repository |
+---------------------+
||
(Internet)
||
+--------------+
| Access Point |
+--------------+
/ | \
/ | \
/ | \
Scribe Participant 1 ... Participant N
Figure 1: Document Sharing During a Meeting
In this scenario, we observe that the same data object bits
(corresponding to the meeting notes) need to traverse the wireless
medium at least N+1 times, where N is the number of meeting
participants obtaining a copy of the notes. In effect, a broadcast
medium is shoehorned into N+1 virtual unicast channels. One could
argue that wireless local connectivity is inexpensive, but this is
not the critical factor in this example. The actual information
exchange wastes N times the available network capacity, no matter
what the spectral efficiency (or the economics) underlying the
wireless technology is. This waste is a direct result of extending
the remote access paradigm from wired to wireless communication,
irrespective of the special characteristics of the latter.
It goes without saying that an ICN approach that does not take into
consideration the wireless nature of an interface will waste the same
amount of resources as a host-centric paradigm. In-network caching
at the wireless access point could reduce the amount of data carried
over the backhaul link, but, if there is no change in the use of the
wireless medium, the NDO will still be carried over the wireless
ether N+1 times. Intelligent caching strategies, replica placement
cooperation, and so on simply cannot alleviate this. On the other
hand, promiscuous interface operation and opportunistic caching would
maximize wireless network capacity utilization in this example.
Arguably, if one designs a future wireless access technology with an
information-centric "layer 3" in mind, many of the design choices
that are obvious in an all-IP architecture may no longer be valid.
Kutscher, et al. Informational [Page 21]RFC 7927 ICN Challenges July 2016
Although this is clearly outside the scope of this document, a few
research challenges that the wider community may be interested in
include:
o Can we use wireless resources more frugally with the information-
centric paradigm than what is possible today in all-IP wireless
networks?
o In the context of wireless access, how can we leverage the
broadcast nature of the medium in an information-centric network?
o Would a wireless-oriented ICN protocol stack deliver significant
performance gains? How different would it be from a wired-
oriented ICN protocol stack?
o Is it possible that by changing the network paradigm to ICN we
can, in practice, increase the spectral efficiency (bits/s/Hz) of
a wireless network beyond what would be possible with today's
host-centric approaches? What would be the impact of doing so
with respect to energy consumption?
o Can promiscuous wireless interface operation coupled with
opportunistic caching increase ICN performance, and if so, by how
much?
o How can a conversational service be supported at least as
efficiently as today's state-of-the-art wireless networks deliver?
o What are the benefits of combining ICN with network coding in
wireless networks?
o How can Multiple-Input Multiple-Output (MIMO) and Coordinated
Multipoint Transmission (CoMP) be natively combined with ICN
primitives in future cellular networks?
4.6. Rate and Congestion Control
ICN's receiver-driven communication model as described above creates
new opportunities for transport protocol design, as it does not rely
solely on end-to-end communication from a sender to a requestor. A
requested data object can be accessible in multiple different network
locations. A node can thus decide how to utilize multiple sources,
e.g., by sending parallel requests for the same NDO or by switching
sources (or next hops) in a suitable schedule for a series of
requests.
Kutscher, et al. Informational [Page 22]RFC 7927 ICN Challenges July 2016
In this model, the requestor would control the data rate by
regulating its request sending rate and next by performing source/
next-hop selections. Specific challenges depend on the specific ICN
approach, but general challenges for receiver-driven transport
protocols (or mechanisms, since dedicated protocols might not be
required) include flow and congestion control, fairness, network
utilization, stability (of data rates under stable conditions), etc.
[HRICP] and [CONTUG] describe request rate control protocols and
corresponding design challenges.
As mentioned above, the ICN communication paradigm does not depend
strictly on end-to-end flows, as contents might be received from in-
network caches. The traditional concept of a flow is then somewhat
not valid as sub-flows, or flowlets, might be formed on the fly, when
fractions of an NDO are transmitted from in-network caches. For a
transport-layer protocol, this is challenging, as any measurement
related to this flow as traditionally done by transport protocols
such as TCP, can often prove misleading. For example, false Round-
Trip Time (RTT) measurements will lead to largely variable average
and smoothed RTT values, which in turn will trigger false timeout
expirations.
Furthermore, out-of-order delivery is expected to be common in a
scenario where parts of a data object are retrieved from in-network
caches rather than from the origin server. Several techniques for
dealing with out-of-order delivery have been proposed in the past for
TCP, some of which could potentially be modified and reused in the
context of ICN. Further research is needed in this direction though
to choose the right technique and adjust it according to the
requirements of the ICN architecture and transport protocol in use.
ICN offers routers the possibility to aggregate requests and can use
several paths, meaning that there is no such thing as a (dedicated)
end-to-end communication path, e.g., a router that receives two
requests for the same content at the same time only sends one request
to its neighbor. The aggregation of requests has a general impact on
transport protocol design and offers new options for employing per-
node forwarding strategies and for rethinking in-network resource
sharing [RESOURCE-POOL].
Achieving fairness for requestors can be one challenge as it is not
possible to identify the number of requestors behind one particular
request. A second problem related to request aggregation is the
management of request retransmissions. Generally, it is assumed that
a router will not transmit a request if it transmitted an identical
request recently, and because there is no information about the
requestor, the router cannot distinguish the initial request from a
Kutscher, et al. Informational [Page 23]
RFC 7927 ICN Challenges July 2016
client from a retransmission from the same client. In such a
situation, routers can adapt their timers to use the best of the
communication paths.
4.7. In-Network Caching
Explicitly named data objects allow for caching at virtually any
network element, including routers, proxy caches, and end-user
devices. Therefore, in-network caching can improve network
performance by fetching content from nodes that are geographically
placed closer to the end user. Several issues that need further
investigation have been identified with respect to in-network
caching. In this section, we list important challenges that relate
to the properties of the new ubiquitous caching system.
4.7.1. Cache Placement
The declining cost of fast memory gives the opportunity to deploy
caches in network routers and to take advantage of cached NDOs. We
identify two approaches to in-network caching, namely, on-path and
off-path caching. Both approaches have to consider the issue of
cache location. Off-path caching is similar to traditional proxy-
caching or CDN server placement. Retrieval of contents from off-path
caches requires redirection of requests and, therefore, is closely
related to the Request-to-Cache Routing problem discussed below.
Off-path caches have to be placed in strategic points within a
network in order to reduce the redirection delays and the number of
detour hops to retrieve cached contents. Previous research on proxy-
caching and CDN deployment is helpful in this case.
On the other hand, on-path caching requires less network intervention
and fits more neatly in ICN. However, on-path caching requires line-
speed operation, which places more constraints on the design and
operation of in-network caching elements. Furthermore, the gain of
such a system of on-path in-network caches relies on opportunistic
cache hits and has therefore been considered of limited benefit,
given the huge amount of contents hosted in the Internet. For this
reason, network operators might initially consider only a limited
number of network elements to be upgraded to in-network caching
elements. The decision on which nodes should be equipped with caches
is an open issue and might be based, among others, on topological
criteria or traffic characteristics. These challenges relate to both
the Content Placement problem and the Request-to-Cache Routing
problem discussed below.
In most cases, however, the driver for the implementation,
deployment, and operation of in-network caches will be its cost.
Operating caches at line speed inevitably requires faster memory,
Kutscher, et al. Informational [Page 24]
RFC 7927 ICN Challenges July 2016
which increases the implementation cost. Based on the capital to be
invested, ISPs will need to make strategic decisions on the cache
placement, which can be driven by several factors, such as avoidance
of inter-domain/expensive links, centrality of nodes, size of domain
and the corresponding spatial locality of users, and traffic patterns
in a specific part of the network (e.g., university vs. business vs.
fashion district of a city).
4.7.2. Content Placement: Content-to-Cache Distribution
Given a number of on-path or off-path in-network caching elements,
content-to-cache distribution will affect both the dynamics of the
system, in terms of request redirections (mainly in case of off-path
caches) and the gain of the system in terms of cache hits. A
straightforward approach to content placement is on-path placement of
contents as they travel from source to destination. This approach
reduces the computation and communication overhead of placing content
within the network but, on the other hand, might reduce the chances
of hitting cached contents. This relates to the Request-to-Cache
Routing problem discussed next.
Furthermore, the number of replicas held in the system brings up
resource management issues in terms of cache allocation. For
example, continuously replicating data objects in all network
elements results in redundant copies of the same objects. The issue
of redundant replication has been investigated in the past for
hierarchical web caches. However, in hierarchical web-caching,
overlay systems coordination between the data and the control plane
can guarantee increased performance in terms of cache hits. Line-
speed, on-path, in-network caching poses different requirements;
therefore, new techniques need to be investigated. In this
direction, reducing the redundancy of cached copies is a study item.
However, the issue of coordinated content placement in on-path caches
remains open.
The Content-to-Cache Allocation problem relates also to the
characteristics of the content to be cached. Popular content might
need to be placed where it is going to be requested next.
Furthermore, issues of "expected content popularity" or temporal
locality need to be taken into account in designing in-network
caching algorithms in order for some contents to be given priority
(e.g., popular content vs. one-timers). The criteria as to which
contents should be given priority in in-network content caches
relates also to the business relationships between content providers
and network operators. Business model issues will drive some of
these decisions on content-to-cache distribution, but such issues are
outside the scope of this note and are not discussed here further.
Kutscher, et al. Informational [Page 25]
RFC 7927 ICN Challenges July 2016
4.7.3. Request-to-Cache Routing
In order to take advantage of cached contents, requests have to be
forwarded to the nodes that cache the corresponding contents. This
challenge relates to name-based routing, discussed earlier. Requests
should ideally follow the path to the cached NDO. However,
instructions as to which content is cached where cannot be broadcast
throughout the network. Therefore, the knowledge of an NDO location
at the time of the request either might not exist or might not be
accurate (i.e., contents might have been removed by the time a
request is redirected to a specific node).
Coordination between the data and the control planes to update
information of cached contents has been considered, but in this case,
scalability issues arise. We therefore have two options. We either
have to rely on opportunistic caching, where requests are forwarded
to a server and in case the NDO is found on the path, then the
content is fetched from this node instead of the origin server, or we
employ cache-aware routing techniques. Cache-aware routing can
involve either both the control and the data plane or only one of
them. Furthermore, cache-aware routing can be done in a domain-wide
scale or can involve more than one individual Autonomous System (AS).
In the latter case, business relationships between ASes might need to
be exploited in order to build a scalable model.
4.7.4. Staleness Detection of Cached NDOs
Due to the largely distributed copies of NDOs in in-network caches,
ICN should be able to provide a staleness verification algorithm that
provides synchronization of NDOs located at their providers and in-
network caching points. Two types of approaches can be considered
for this problem, namely direct and indirect approaches.
In the direct approach, each cache looks up certain information in
the NDO's name, e.g., the timestamp, that directly indicates its
staleness. This approach is applicable to some NDOs that come from
machine-to-machine and Internet of Things scenarios, whose base
operation relies on obtaining the latest version of that NDO (i.e., a
soil sensor in a farm providing different continuous parameters that
are sent to a display or greenhouse regulation system) [FRESHNESS].
In the indirect approach, each cache consults the publisher of the
cached NDO about its staleness before serving it. This approach
assumes that the NDO includes the publisher information, which can be
used to reach the publisher. It is suitable for the NDO whose
expiration time is difficult to be set in advance, e.g., a web page
Kutscher, et al. Informational [Page 26]
RFC 7927 ICN Challenges July 2016
that contains the main text (which stays the same ever after) and the
interactive sections such as comments or ads (which are updated
irregularly).
It is often argued that ignoring stale NDOs in caches and simply
providing new names for updated NDOs might be sufficient rather than
using a staleness verification algorithm to manage them. However,
notifying the new names of updated NDOs to users is not a trivial
task. Unless the update is informed to all users at the same time,
some users would use the old name although they intended to retrieve
the updated NDO.
One research challenge is how to design consistency and coherence
models for caching NDOs along with their revision handling and
updating protocols in a scalable manner.
4.7.5. Cache Sharing by Multiple Applications
When ICN is deployed as a general, application-independent network
and cache infrastructure, multiple consumers and producers
(representing different applications) would communicate over the same
infrastructure. With universal naming schemes or sufficiently unique
hash-based identifiers, different application could also share
identical NDOs in a transparent way.
Depending on the naming, data integrity, and data origin
authentication approaches, there may be technical and business
challenges to share caches across different applications, for
example, content protection, avoiding cache poisoning, ensuring
performance isolation, etc. As ICN research matures, these
challenges should be addressed more specifically in a dedicated
document.
4.8. Network Management
Managing networks has been a core craft in the IP-based host-centric
paradigm ever since the technology was introduced in production
networks. However, at the onset of IP, management was considered
primarily as an add-on. Essential tools that are used daily by
networkers, such as ping and traceroute, did not become widely
available until more than a decade or so after IP was first
introduced. Management protocols, such as SNMP, also became
available much later than the original introduction of IP, and many
still consider them insufficient despite the years of experience we
have running host-centric networks. Today, when new networks are
deployed, network management is considered a key aspect for any
operator, a major challenge that is directly reflected in higher
operational cost if not done well. If we want ICN to be deployed in
Kutscher, et al. Informational [Page 27]
RFC 7927 ICN Challenges July 2016
infrastructure networks, development of management tools and
mechanisms must go hand in hand with the rest of the architecture
design.
Although defining an FCAPS (Fault, Configuration, Accounting,
Performance, and Security) [ISOIEC-7498-4] management model for ICN
is clearly outside the scope of this document, there is a need for
creating basic tools early on while ICN is still in the design and
experimentation phases that can evolve over time and help network
operations centers (NOCs) to define policies, validate that they are
indeed used in practice, be notified early on about failures, and
determine and resolve configuration problems. Authentication,
Authorization, and Accounting (AAA) as well as performance
management, from a NOC perspective, will also need to be considered.
Given the expectations for a large number of nodes and unprecedented
traffic volumes, automating tasks or even better employing self-
management mechanisms are preferred. The main challenge here is that
all tools we have at our disposal today are node-centric, are end-to-
end oriented, or assume a packet-stream communication environment.
Rethinking reachability and operational availability, for example,
can yield significant insights into how information-centric networks
will be managed in the future.
With respect to network management, we see three different aspects.
First, any operator needs to manage all resources available in the
network, which can range from node connectivity to network bandwidth
availability to in-network storage to multi-access support. In ICN,
users will also bring into the network significant resources in terms
of network coverage extension, storage, and processing capabilities.
Delay Tolerant Networking (DTN) characteristics should also be
considered to the degree that this is possible (e.g., content
dissemination through data mules). Second, given that nodes and
links are not at the center of an information-centric network,
network management should capitalize on native ICN mechanisms. For
example, in-network storage and name resolution can be used for
monitoring, while native publish/subscribe functionality can be used
for triggering notifications. Finally, management is also at the
core of network-controlling capabilities by allowing operating
actions to be mediated and decided, triggering and activating
networking procedures in an optimized way. For example, monitoring
aspects can be conjugated with different management actions in a
coordinated way, allowing network operations to flow in a concerted
manner.
However, the considerations on leveraging intrinsic ICN mechanisms
and capabilities to support management operations go beyond a simple
mapping exercise. In fact, it not only raises a series of challenges
on its own, but also opens up new possibilities for both ICN and
Kutscher, et al. Informational [Page 28]
RFC 7927 ICN Challenges July 2016
"network management" as a concept. For instance, naming mechanisms
are central to ICN-intrinsic operations, which are used to identify
and reach content under different aspects (e.g., hierarchically
structured vs. "flattish" names). In this way, ICN is decoupled from
host-centric aspects on which traditional network management schemes
rely. As such, questions are raised that can directly be translated
into challenges for network management capability, such as, for
example, how to address a node or a network segment in an ICN naming
paradigm, how to identify which node is connected "where", how to be
aware of the node capabilities (i.e., high or low-powered machine-to-
machine (M2M) node), and if there is a host-centric protocol running
where the management process can also leverage.
But, on the other hand, these same inherent ICN characteristics also
allow us to look into network management through a new perspective.
By centering its operations around NDOs, one can conceive new
management operations addressing, for example, per-content management
or access control, as well as analyzing performance per NDO instead
of per link or node. Moreover, such considerations can also be used
to manage operational aspects of ICN mechanisms themselves. For
example, [NDN-MGMT] reutilizes inherent content-centric capabilities
of CCN to manage optimal link connectivity for nodes, in concert with
a network optimization process. Conversely, how these content-
centric aspects can otherwise influence and impact management in
other areas (e.g., security and resilience) is also important, as
exemplified in [CCN-ACCESS], where access control mechanisms are
integrated into a prototype of the [PURSUIT] architecture.
The set of core research challenges for ICN management includes:
o Management and control of NDO reception at the requestor
o Coordination of management information exchange and control
between ICN nodes and ICN network control points
o Identification of management and controlling actions and items
through information naming
o Relationship between NDOs and host entities identification, i.e.,
how to identify a particular link, interface, or flow that needs
to be managed
4.9. ICN Applications
ICN can be applied to different application domains and is expected
to provide benefits for application developers by providing a more
suitable interface for application developers (in addition to the
Kutscher, et al. Informational [Page 29]RFC 7927 ICN Challenges July 2016
other ICN benefits described above). [RFC7476] provides an overview
of relevant application domains at large. This section discusses
opportunities and challenges for selected application types.
4.9.1. Web Applications
Intuitively, the ICN request/response communication style seems to be
directly mappable to web communication over HTTP. NDO names could be
the equivalent of URIs in today's web, proprietary and transparent
caching could be obsoleted by ICN in-network caching, and developers
could directly use an ICN request/response API to build applications.
Research efforts such as [ICN2014-WEB-NDN] have analyzed real-world
web applications and ways to implement them in ICN. The most
significant insight is that REST-style (Representational State
Transfer) web communication relies heavily on transmitting user/
application context information in HTTP GET requests, which would
have to be mapped to corresponding ICN messages. The challenge in
ICN would be how to exactly achieve that mapping. This could be done
to some degree by extending name formats or by extending message
structure to include cookies and similar context information. The
design decisions would need to consider overhead in routers (for
example, if larger GET/Interest messages would have to be stored in
corresponding tables on routers).
Other challenges include the ability to return different results
based on requestor-specific processing in the presence of immutable
objects (and name-object bindings) in ICN and the ability for
efficient bidirectional communication, which would require some
mechanism to name and reach requestor applications.
4.9.2. Video Streaming and Download
One of ICN's prime application areas is video streaming and download
where accessing named data, object-level security, and in-network
storage can fulfill requirements for both video streaming and
download. The applicability and benefits of ICN to video has been
demonstrated by several prototype developments
[ICN2014-AHLGREN-VIDEO-DEMO].
[VIDEO-STREAMING] discusses the opportunities and challenges of
implementing today's video services such as DASH-based (Dynamic
Adaptive Streaming over HTTP) streaming and download over ICN,
considering performance requirements, relationship to peer-to-peer
live streaming, IPTV, and Digital Rights Management (DRM).
Kutscher, et al. Informational [Page 30]
RFC 7927 ICN Challenges July 2016
In addition to just porting today's video application from a host-
centric paradigm to ICN, there are also promising opportunities to
leverage the ICN network services for redesigning and thus
significantly enhancing video access and distribution
[ICNRG-2015-01-WESTPHAL]. For example, ICN store and forward could
be leveraged for rate adaptation to achieve maximum throughput and
optimal Quality of Experience (QoE) in scenarios with varying link
properties, if capacity information is fed back to rate selection
algorithms at senders. Other optimizations such as more aggressive
prefetching could be performed in the network by leveraging
visibility of chunk NDO names and NDO metadata in the network.
Moreover, multi-source rate adaptation in combination with network
coding could enable better QoE, for example, in multi-interface/
access scenarios where multiple paths from client to upstream caches
exist [RFC7476].
4.9.3. Internet of Things
The essence of ICN lies in the name-based routing that enables users
to retrieve NDOs by the names regardless of their locations. By
definition, ICN is well suited for IoT applications, where users
consume data generated from IoTs without maintaining secure
connections to them. The basic request/response style APIs of ICN
enable developers to build IoT applications in a simple and fast
manner.
Ongoing efforts such as [ICN-FOR-IOT], [ICN-ARCH], and
[ICN2014-NDNWILD] have addressed the requirements and challenges of
ICN for IoT. For instance, many IoT applications depend on a PUSH
model where data transmission is initiated by the publisher, so they
can support various real-time applications (emergency alarm, etc.).
However, ICN does not support the PUSH model in a native manner due
to its inherent receiver-driven data transmission mechanism. The
challenge would be how to efficiently support the PUSH model in ICN,
so it provides publish/subscribe-style APIs for IoT application
developers. This could be done by introducing other types of
identifiers such as a device identifier or by extending the current
request/response communication style, which may result in heavy
overhead in ICN routers.
Moreover, key characteristics of the ICN underlying operation also
impact important aspects of IoT, such as the caching in content
storage of network forwarding entities. This allows the
simplification of ICN-based IoT application development. Since the
network is able to act on named content, generic names provide a way
to address content independently of the underlying device (and
access) technology, and bandwidth consumption is optimized due to the
availability of cached content. However, these aspects raise
Kutscher, et al. Informational [Page 31]
RFC 7927 ICN Challenges July 2016
challenges themselves concerning the freshness of the information
received from the cache in contrast to the last value generated by a
sensor, as well as pushing content to specific nodes (e.g., for
controlling them), which requires individual addressing for
identification. In addition, due to the heterogeneous nature of IoT
nodes, their processing capabilities might not be able to handle the
necessary content signing verification procedures.
5. Security Considerations
This document does not impact the security of the Internet. Security
questions related to ICN are discussed in Section 4.2.
6. Informative References
[ACCESS-CTL-DEL]
Fotiou, N., Marias, G., and G. Polyzos, "Access control
enforcement delegation for information-centric networking
architectures", Proceedings of the second edition of the
ICN workshop on Information-centric networking (ICN
'12) Helsinki, Finland, DOI 10.1145/2342488.2342507, 2012.
[BACKSCATTER]
Waehlisch, M., Schmidt, TC., and M. Vahlenkamp,
"Backscatter from the Data Plane - Threats to Stability
and Security in Information-Centric Network
Infrastructure", Computer Networks Vol 57, No. 16, pp.
3192-3206, DOI 10.1016/j.comnet.2013.07.009, November
2013.
[BREADCRUMBS]
Rosensweig, E. and J. Kurose, "Breadcrumbs: Efficient,
Best-Effort Content Location in Cache Networks",
In Proceedings of the IEEE INFOCOM 2009,
DOI 10.1109/INFCOM.2009.5062201, April 2009.
[CCN] Jacobson, V., Smetters, D., Thornton, J., Plass, M.,
Briggs, N., and R. Braynard, "Networking Named Content",
CoNEXT 2009, DOI 10.1145/1658939.1658941, December 2009.
[CCN-ACCESS]
Fotiou, N., Marias, G., and G. Polyzos, "Access control
enforcement delegation for information-centric networking
architectures", In Proceedings of the second edition of
the ICN workshop on Information-centric networking (ICN
'12), ACM, New York, NY, USA, 85-90,
DOI 10.1145/2342488.2342507, 2012.
Kutscher, et al. Informational [Page 32]RFC 7927 ICN Challenges July 2016
[CHAUM] Chaum, D. and E. van Heijst, "Group signatures",
In Proceedings of EUROCRYPT, DOI 10.1007/3-540-46416-6_22,
1991.
[COMPACT] Cowen, L., "Compact routing with minimum stretch",
In Journal of Algorithms, vol. 38, pp. 170-183,
DOI 10.1006/jagm.2000.1134, 2001.
[CONTUG] Arianfar, S., Nikander, P., Eggert, L., Ott, J., and W.
Wong, "ConTug: A Receiver-Driven Transport Protocol for
Content-Centric Networks", Technical Report Aalto
University Comnet, 2011.
[DONA] Koponen, T., Ermolinskiy, A., Chawla, M., Kim, K., gon
Chun, B., and S. Shenker, "A Data-Oriented (and Beyond)
Network Architecture", In Proceedings of SIGCOMM 2007,
DOI 10.1145/1282427.1282402, August 2007.
[ENCRYPTION-AC]
Kurihara, J., Uzun, E., and C. Wood, "An Encryption-Based
Access Control Framework for Content-Centric Networking",
IFIP Networking 2015, Toulouse, France,
DOI 10.1109/IFIPNetworking.2015.7145300, September 2015.
[FRESHNESS]
Quevedo, J., Corujo, D., and R. Aguiar, "Consumer Driven
Information Freshness Approach for Content Centric
Networking", IEEE INFOCOM Workshop on Name-Oriented
Mobility Toronto, Canada,
DOI 10.1109/INFCOMW.2014.6849279, May 2014.
[GREEDY] Papadopoulos, F., Krioukov, D., Boguna, M., and A. Vahdat,
"Greedy forwarding in dynamic scale-free networks embedded
in hyperbolic metric spaces", In Proceedings of the IEEE
INFOCOM, San Diego, USA, DOI 10.1109/INFCOM.2010.5462131,
2010.
[HRICP] Carofiglio, G., Gallo, M., and L. Muscariello, "Joint hop-
by-hop and receiver-driven interest control protocol for
content-centric networks", In Proceedings of ACM SIGCOMM
ICN 2012, DOI 10.1145/2342488.2342497, 2012.
[ICN-ARCH] Zhang, Y., Raychadhuri, D., Grieco, L., Baccelli, E.,
Burke, J., Ravindran, R., Ed., and G. Wang, "ICN based
Architecture for IoT - Requirements and Challenges", Work
in Progress, draft-zhang-iot-icn-challenges-02, August
2015.
Kutscher, et al. Informational [Page 33]RFC 7927 ICN Challenges July 2016
[ICN-FOR-IOT]
Lindgren, A., Ben Abdesslem, F., Ahlgren, B., Schelen, O.,
and A. Malik, "Applicability and Tradeoffs of Information-
Centric Networking for Efficient IoT", Work in Progress,
draft-lindgren-icnrg-efficientiot-03, July 2015.
[ICN2014-AHLGREN-VIDEO-DEMO]
Ahlgren, B., Jonasson, A., and B. Ohlman, "Demo Overview:
HTTP Live Streaming over NetInf Transport", ACM SIGCOMM
Information-Centric Networking Conference Paris, France,
DOI 10.1145/2660129.2660136, September 2014.
[ICN2014-NDNWILD]
Baccelli, E., Mehlis, C., Hahm, O., Schmidt, T., and M.
Waehlisch, "Information Centric Networking in the IoT:
Experiments with NDN in the Wild", ACM SIGCOMM
Information-Centric Networking Conference Paris, France,
DOI 10.1145/2660129.2660144, September 2014.
[ICN2014-WEB-NDN]
Moiseenko, I., Stapp, M., and D. Oran, "Communication
Patterns for Web Interaction in Named Data Networking",
ACM SIGCOMM Information-Centric Networking
Conference Paris, France, DOI 10.1145/2660129.2660152,
September 2014.
[ICNNAMING]
Ghodsi, A., Koponen, T., Rajahalme, J., Sarolahti, P., and
S. Shenker, "Naming in Content-Oriented Architectures",
In Proceedings ACM SIGCOMM Workshop on Information-Centric
Networking (ICN), DOI 10.1145/2018584.2018586, 2011.
[ICNRG-2015-01-WESTPHAL]
Westphal, C., "Video over ICN", IRTF ICNRG
Meeting Cambridge, Massachusetts, USA, January 2015,
<http://www.ietf.org/proceedings/interim/2015/01/13/icnrg/
slides/slides-interim-2015-icnrg-1-0.pptx>.
[ICNSURVEY]
Ahlgren, B., Dannewitz, C., Imbrenda, C., Kutscher, D.,
and B. Ohlman, "A Survey of Information-Centric
Networking", In Communications Magazine, IEEE, vol. 50,
no. 7, pp. 26-36, DOI 10.1109/MCOM.2012.6231276, 2012.
Kutscher, et al. Informational [Page 34]RFC 7927 ICN Challenges July 2016
[ISOIEC-7498-4]
ISO, "Information Processing Systems -- Open Systems
Interconnection -- Basic Reference Model -- Part 4:
Management Framework", November 1989,
<http://standards.iso.org/ittf/PubliclyAvailableStandards/
s014258_ISO_IEC_7498-4_1989(E).zip>.
[MANI] Pentikousis, K. and T. Rautio, "A multiaccess Network of
Information", WoWMoM 2010 IEEE,
DOI 10.1109/WOWMOM.2010.5534922, June 2010.
[MDHT] D'Ambrosio, M., Dannewitz, C., Karl, H., and V.
Vercellone, "MDHT: A hierarchical name resolution service
for information-centric networks", ACM SIGCOMM workshop on
Information-centric networking Toronto, Canada,
DOI 10.1145/2018584.2018587, August 2011.
[MMIN] Pentikousis, K. and P. Bertin, "Mobility management in
infrastructure networks", Internet Computing, IEEE vol.
17, no. 5, pp. 74-79, DOI 10.1109/MIC.2013.98, October
2013.
[NDN-CTL-SHARING]
Yu, Y., "Controlled Sharing of Sensitive Content", IRTF
ICNRG Meeting San Francisco, USA, October 2015,
<https://www.ietf.org/proceedings/interim/2015/10/03/
icnrg/slides/slides-interim-2015-icnrg-4-8.pdf>.
[NDN-MGMT] Corujo, D., Aguiar, R., Vidal, I., and J. Garcia-Reinoso,
"A named data networking flexible framework for management
communications", Communications Magazine, IEEE vol. 50,
no. 12, pp. 36-43, DOI 10.1109/MCOM.2012.6384449, December
2012.
[PURSUIT] Fotiou et al., N., "Developing Information Networking
Further: From PSIRP to PURSUIT", In Proceedings of Proc.
BROADNETS. ICST, DOI 10.1007/978-3-642-30376-0_1, 2010.
[RANDOM] Gkantsidis, C., Mihail, M., and A. Saberi, "Random walks
in peer-to-peer networks: algorithms and evaluation",
In Perform. Eval., vol. 63, pp. 241-263,
DOI 10.1016/j.peva.2005.01.002, 2006.
[RESOURCE-POOL]
Psaras, I., Saino, L., and G. Pavlou, "Revisiting Resource
Pooling: The case of In-Network Resource Sharing", ACM
HotNets Los Angeles, USA, DOI 10.1145/2670518.2673875,
October 2014.
Kutscher, et al. Informational [Page 35]RFC 7927 ICN Challenges July 2016
[RFC2002] Perkins, C., Ed., "IP Mobility Support", RFC 2002,
DOI 10.17487/RFC2002, October 1996,
<http://www.rfc-editor.org/info/rfc2002>.
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
Networking Architecture", RFC 4838, DOI 10.17487/RFC4838,
April 2007, <http://www.rfc-editor.org/info/rfc4838>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>.
[RFC5944] Perkins, C., Ed., "IP Mobility Support for IPv4, Revised",
RFC 5944, DOI 10.17487/RFC5944, November 2010,
<http://www.rfc-editor.org/info/rfc5944>.
[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,
<http://www.rfc-editor.org/info/rfc6920>.
[RFC7476] Pentikousis, K., Ed., Ohlman, B., Corujo, D., Boggia, G.,
Tyson, G., Davies, E., Molinaro, A., and S. Eum,
"Information-Centric Networking: Baseline Scenarios",
RFC 7476, DOI 10.17487/RFC7476, March 2015,
<http://www.rfc-editor.org/info/rfc7476>.
[RFC7696] Housley, R., "Guidelines for Cryptographic Algorithm
Agility and Selecting Mandatory-to-Implement Algorithms",
BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,
<http://www.rfc-editor.org/info/rfc7696>.
[SEEN] Pentikousis, K., "In search of energy-efficient mobile
networking", Communications Magazine, IEEE vol. 48 no. 1,
pp. 95-103, DOI 10.1109/MCOM.2010.5394036, January 2010.
Kutscher, et al. Informational [Page 36]RFC 7927 ICN Challenges July 2016
[VIDEO-STREAMING]
Westphal, C., Ed., Lederer, S., Posch, D., Timmerer, C.,
Azgin, A., Liu, S., Mueller, C., Detti, A., Corujo, D.,
Wang, J., Montpetit, M., Murray, N., Azgin, A., and S.
Liu, "Adaptive Video Streaming over ICN", Work in
Progress, draft-irtf-icnrg-videostreaming-08, April 2016.
Acknowledgments
The authors would like to thank Georgios Karagiannis for providing
suggestions on QoS research challenges, Dimitri Papadimitriou for
feedback on the routing section, and Joerg Ott and Stephen Farrell
for reviewing the whole document.
Authors' Addresses
Dirk Kutscher (editor)
NEC
Kurfuersten-Anlage 36
Heidelberg
Germany
Email: kutscher@neclab.eu
Suyong Eum
Osaka University, School of Information Science and Technology
1-5 Yamadaoka, Suita
Osaka 565-0871
Japan
Phone: +81-6-6879-4571
Email: suyong@ist.osaka-u.ac.jp
Kostas Pentikousis
Travelping
Koernerstr. 7-10
Berlin 10785
Germany
Email: k.pentikousis@travelping.com
Kutscher, et al. Informational [Page 37]RFC 7927 ICN Challenges July 2016
Ioannis Psaras
University College London, Dept. of E.E. Eng.
Torrington Place
London WC1E 7JE
United Kingdom
Email: i.psaras@ucl.ac.uk
Daniel Corujo
Universidade de Aveiro
Instituto de Telecomunicacoes, Campus Universitario de Santiago
Aveiro P-3810-193
Portugal
Email: dcorujo@av.it.pt
Damien Saucez
INRIA
2004 route des Lucioles - BP 93
Sophia Antipolis 06902 Cedex
France
Email: damien.saucez@inria.fr
Thomas C. Schmidt
HAW Hamburg
Berliner Tor 7
Hamburg 20099
Germany
Email: t.schmidt@haw-hamburg.de
Matthias Waehlisch
FU Berlin
Takustr. 9
Berlin 14195
Germany
Email: waehlisch@ieee.org
Kutscher, et al. Informational [Page 38]
