icnrg B. Wissingh
Internet-Draft TNO
Intended status: Informational C. Wood
Expires: January 9, 2017 PARC
L. Zhang
A. Afanasyev
UCLA
D. Oran
Cisco Systems, Inc.
July 8, 2016
Information-Centric Networking: Terminology
draft-wissingh-icnrg-terminology-00
Abstract
Information Centric Networking (ICN) is a new paradigm where network
communications are accomplished by requesting named content, instead
of sending packets to destination addresses. This document provides
an overview of the terminology and definitions that have been used in
describing this new paradigm. This document is a product of the IRTF
Information-Centric Networking Research Group (ICNRG).
Status of This Memo
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This Internet-Draft will expire on January 9, 2017.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. A Sketch of the Big Picture of an ICN Network Architecture . 2
3. Terms by category . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Generic terms . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Data naming related terms . . . . . . . . . . . . . . . . 4
3.3. Data-Centric Security related terms . . . . . . . . . . . 5
3.4. ICN Node related terms . . . . . . . . . . . . . . . . . 6
3.5. Stateful forwarding plane related terms . . . . . . . . . 7
3.6. Specific solution related terms . . . . . . . . . . . . . 9
3.7. Uncategorized terms . . . . . . . . . . . . . . . . . . . 9
4. Informational References . . . . . . . . . . . . . . . . . . 10
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Information-centric networking (ICN) is an approach to evolve the
Internet infrastructure from the existing host-centric design to a
data-centric architecture where named data becomes the essential
network primitive. The ICN design directly names and secures data
objects, making them independent of their location or means of
transportation, and enabling native multicast delivery and ubiquitous
in-network caching and replication of data objects.
As the work on this topic continues to evolve, many new terms are
born over time. The goal of this document is to provide a complete
collection of these terms with a corresponding definition. To help
provide the context of the individual terms to be defined, in this
draft we first sketch the bigger picture of an ICN network,
introducing the basic concepts and identifying the major components
in the architecture in section 2 after which in section 3 ICN related
terms are listed by different categories.
2. A Sketch of the Big Picture of an ICN Network Architecture
In an ICN network data is fetched by names. This is accomplished by
defining two types of network packet formats: interest packets that
request a piece of named content and data packets that carry the
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requested content. Every data packet must be cryptographically
signed which binds its name and content together. A basic set of ICN
concepts is listed below:
Data Naming:
Within ICN, the granularity of names is on a per packet basis. This
implies that if the size of a piece of content from an application
exceeds the network packet size limit, the content is segmented into
multiple data packets. Each of these individual data packets is then
uniquely named with the content name concatenated with the segment
number.
Each ICN data packet is also immutable. This is accomplished by
assigning a version number to each piece of application content.
When the content changes, the version number in its name changes as
well.
Data-Centric Security:
Security within ICN concerns data authentication, confidentiality,
and user privacy. Each ICN data packet carries a signature that
binds the name and content of the data packet together, allowing a
named packet to be fetched from anywhere while the application is
still able to verify the validity of the data packet.
ICN node:
A node within an ICN network can fulfill the role of a data producer,
a data consumer, and/or a forwarder for interest and data packets.
When a forwarder has connectivity to neighbor nodes, it performs
interest and data packet forwarding in real time. It can also behave
like a packet mule, that is it may carry an interest or data packet
over some distance before forwarding it to next node. An ICN node
may also run routing protocols to assist its interest forwarding
decisions.
Stateful forwarding plane:
Generally speaking, an ICN forwarder keeps three data structures: a
Forwarding Interest Table (FIB), a Pending Interest Table (PIT), and
a Content Store (CS). It also utilizes interest forwarding
strategies which takes input from both FIB and measurements to make
interest forwarding decisions. When a node receives an ICN interest
packet, it checks its CS and PIT to find a matching name; if no match
is found, the node records the interest in its PIT and forwards the
interest to the next hop(s) towards the requested content based on
the information in its FIB.
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3. Terms by category
3.1. Generic terms
Information-Centric Networking (ICN): a networking architecture
that retrieves data packets as response to interest packets.
Data packet (same as data, data object, content object packet,
data message, named data object, named data): a network-level
packet that carries payload, uniquely identified by a name, and is
directly secured.
Interest packet (same as interest, information request): a
network-level packet that expresses the request for a data packet
using either an exact name or a name prefix. An interest packet
may optionally carry a set of additional restrictions (e.g.
interest selectors). An interest may be associated with
additional information to facilitate forwarding and can include
interest lifetime, hop limit, forwarding hints, labels, etc. In
different ICN designs, the set of additional associated
information may vary.
Data packet immutability: after a data packet is created, it
cannot change. When content carried in the data packet is
mutable, versioning should be used, so each version is uniquely
identified. This allows disambiguation of coordination in
distributed ICN networks that may not be always connected.
3.2. Data naming related terms
Name (aka data name, interest name, content name): a unique
identifier of the data packet. ICN name is expressive, flexible,
and can be application-specific (akin HTTP URL), a name may encode
information about application context, semantics, locations
(topological, geographical, hyperbolic, etc.), service name, etc.
Self-certifying name: a special type of data name that uses a
packet ID as data name or uses a packet ID as part of the name
Packet ID: a unique cryptographic identifier for a data packet.
Typically, this is the cryptographic hash digest of a data packet,
including its name, payload, meta information, and signature.
Naming scheme (ICN naming scheme): a convention/agreement/
specification for the data packet naming.
Hierarchically structured naming (same as hierarchical naming,
structured naming): the naming scheme that assigns and interprets
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name as a sequence of labels (name components) with hierarchical
structure. A structure provides useful context information for
the name.
Flat naming: the naming scheme that assigns and interprets name as
a single label (name component) without any internal structure.
This can be considered a special (or degenerated) case of
structured names.
Name component (same as name segment): a sequence of octets and
optionally a numeric type representing a single label in the
hierarchical structured name.
Name prefix: a sequence of name components from the beginning of a
hierarchically structured name.
Segmentation (same as chunking): a process of splitting large
application content into a set of uniquely named data packets.
When using hierarchically structured name, each created data
packet has a common prefix and additional component representing
the segment (chunk) number.
Versioning: a process of assigning a unique name to the revision
of the content carried in the data packet. When using a
hierarchically structured name, the version of the data packet can
be carried in a dedicated name component (e.g., prefix identifies
data, unique version component identifies the revision of the
data).
Fragmentation: a process of splitting large data packets into
smaller pieces so that they can be transmitted over the link with
a smaller MTU size.
3.3. Data-Centric Security related terms
Directly secured data packet: a data packet with inherent security
properties (authenticity and optionally confidentiality), i.e.,
the security properties stay with the data packet regardless where
it is stored and how it is retrieved.
Data authenticator (content authenticator): a set of parameters
carried in the data packet that is used to verify integrity and
authenticity of the data packet. The Data authenticator can
include a cryptographic signature (RSA, ECDSA, HMAC, etc.), meta
information about the signature (e.g., validity period), and
additional information to facilitate signature verification (e.g.,
key locator, key ID, HMAC tag identifier, etc.)
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Data confidentiality credentials: a set of parameters carried in
the data packet that is used to identify how the confidential data
can be decrypted by authorized consumers.
ICN (public) key (same as ICN certificate): a data packet that
carries public key or public key certificate as payload and may
have additional meta information regarding the public key (e.g.,
validity period, signature time, etc.). The key belongs to the
ICN key owner and can be associated with it implicitly through the
name or explicitly through meta information.
ICN key owner (same as Identity): an entity (user, device,
program, program instance, module in the program instance, etc.)
that owns the private key that corresponds to the ICN key.
Key locator (same as ?): Parameter(s) that identify the ICN key,
which can be the ICN key name, ICN key prefix, ICN key ID, etc.
ICN key ID: Packet ID of the ICN (public) key.
Trust model: a model or framework that defines trust
relationships, i.e., which entity (represented by an ICN key) is
authorized to sign which data packets.
ICN key chain (certificate chain): a chain of ICN keys
(certificates) wherein each key (certificate) is signed by its
predecessor and the head of the chain is a trust anchor, i.e., its
authenticity is assumed.
Trust schema: a formal description of a trust model, e.g., in the
form of a set of name-based relationships between data and key
names and a set of the trust anchors.
Trust anchor: an ICN key that is assumed to be trusted within the
context of a specific trust model.
3.4. ICN Node related terms
ICN Interface (same as face): a generalization of the network
interface that can represent a physical network interface
(ethernet, wifi, bluetooth adapter, etc.), an overlay inter-node
channel (IP/UDP tunnel, etc.), or an intra-node IPC channel to an
application (unix socket, shared memory, intents, etc.).
ICN Consumer (same as consumer, information consumer, data
consumer, consumer of the content): an ICN entity that requests
data packets by generating and sending out interest packets
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towards local (using intra-node interfaces) or remote (using
inter-node interfaces) ICN Forwarders.
ICN Producer (same as producer, publisher, information publisher,
data publisher, data producer): an ICN entity that creates data
packets and makes them available for retrieval.
ICN Forwarder (same as ICN router): an ICN entity that implements
stateful forwarding.
Data Mule: an ICN entity that carries an interest or data packet
over some distance before forwarding it to next ICN entity.
3.5. Stateful forwarding plane related terms
Stateful forwarding (same as ICN Data plane, ICN Forwarding): a
forwarding process that records incoming interest packets in the
PIT and uses the recorded information to forward the retrieved
data packets back to the consumer(s). The recorded information
can also be used to measure data plane performance, e.g., to
adjust interest forwarding strategy decisions.
Name-based routing: a process of forwarding interest packets using
the names in interests to guide the forwarding process
ICN Pending Interest Table (PIT): a database that records received
and not yet satisfied interests with the interfaces from where
they were received. The PIT can also store interfaces to where
Interests were forwarded, and information to assess data plane
performance. Interests for the same data are aggregated into a
single PIT entry.
ICN Routing plane: an ICN protocol or a set of ICN protocols to
exchange information about data packet availability.
Satisfying an Interest: a process of forwarding the incoming data
packet to the incoming interface(s) recorded in the corresponding
PIT entry (entries) and removing the PIT entry (entries).
Interest forwarding strategy (same as forwarding strategy): a
module of the ICN stateful forwarding (ICN data) plane that
implements a decision on where/how to forward the incoming
interest packet. The forwarding strategy can take input from ICN
Forwarding Information Base (FIB), measured data plane performance
parameters, and/or use other mechanisms to make the decision.
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Interest match in FIB (longest prefix match): a process of finding
a FIB entry with the longest name (in terms of name components)
that is a prefix of the specified name.
Interest match in PIT (exact match): a process of finding a PIT
entry that stores the same as specified interest (including
interest restrictions, if any).
Data match in PIT (all match): a process of finding (a set of) PIT
entries that can be satisfied with the specified data packet.
Interest match in CS (any match): a process of finding an entry in
router's content store that can satisfy the specified interest.
Interest aggregation (same as interest suppression, interest
collapsing): a process of combining multiple interest packets for
the same data into a single PIT entry.
ICN Forwarding Information Base (FIB): a database that, for a set
of prefixes, records a list of interfaces that can be used to
retrieve data packets with names under the corresponding prefixes.
The list of interfaces for each prefix can be ranked, and prefix/
interfaces mapping , and interfaces can be associated with the
additional information to facilitate forwarding strategy
decisions.
ICN Routing Information Base (RIB): a database that records a set
of prefix-interface mappings that represent a candidate interface
through which a data packet with the specified prefix can be
retrieved. RIB can be used to populate FIB.
Interest Nack (same as network NACK, interest return): a packet
that contains the interest packet and optional annotation, which
is sent by the router to the interface(s) the Interest was
received from. Interest Nack is used to inform downstream ICN
nodes about inability to forward the included interest packet.
The annotation can describe the reason.
Upstream forwarding: forwarding packets in the direction of
interests (i.e., interests are forwarded upstream): consumer,
router, router, ..., producer.
Downstream forwarding: forwarding packets in the direction
opposite of interest forwarding (i.e., data and interest nacks are
forwarded downstream): producer, router, ..., consumer(s).
In-network storage: a process of storing a data packet within the
network (in routers opportunistic on-path caches, in dedicated on/
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off path caches, and managed in-network storage systems), so it
can satisfy an incoming interest for this data packet. The in-
network storages can optionally advertise the stored data packets
in the routing plane.
Opportunistic caching (or on-path in-network caching or just
caching): a process of temporarily storing a forwarded data packet
in the router's memory (RAM or disk), so it can be used to satisfy
future interests for the same data, if any.
Managed caching (or off-path in-network storage): a process of
temporarily, permanently, or scheduled storing of a selected (set
of) data packet(s).
Content Store (CS): a database on an ICN router to implement the
opportunistic caching.
Managed in-network storage (repository, repo): an entity acting as
an ICN producer that implements managed caching.
3.6. Specific solution related terms
Route-By-Name Routing (RBNR)
Lookup-By-Name Routing (LBNR)
Bread-crumbs routing
Replication-by-name
Routing Locator Signing
3.7. Uncategorized terms
Chunks (same as segments)
Content based
ICN API
Information Centric Delay Tolerant Network
Located-Named-Data
NDN
Sessionless
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4. Informational References
[I-D.irtf-icnrg-ccnxmessages]
marc.mosko@parc.com, m., Solis, I., and c. cwood@parc.com,
"CCNx Messages in TLV Format", draft-irtf-icnrg-
ccnxmessages-03 (work in progress), June 2016.
[I-D.irtf-icnrg-ccnxsemantics]
marc.mosko@parc.com, m., Solis, I., and c. cwood@parc.com,
"CCNx Semantics", draft-irtf-icnrg-ccnxsemantics-03 (work
in progress), June 2016.
[I-D.irtf-icnrg-challenges]
Kutscher, D., Eum, S., Pentikousis, K., Psaras, I.,
Corujo, D., Saucez, D., Schmidt, T., and M. Waehlisch,
"ICN Research Challenges", draft-irtf-icnrg-challenges-06
(work in progress), March 2016.
[I-D.irtf-icnrg-disaster]
Seedorf, J., Arumaithurai, M., Tagami, A., Ramakrishnan,
K., and N. Blefari-Melazzi, "Using ICN in disaster
scenarios", draft-irtf-icnrg-disaster-00 (work in
progress), February 2016.
[I-D.irtf-icnrg-evaluation-methodology]
Pentikousis, K., Ohlman, B., Davies, E., Spirou, S., and
G. Boggia, "Information-centric Networking: Evaluation and
Security Considerations", draft-irtf-icnrg-evaluation-
methodology-05 (work in progress), April 2016.
[I-D.irtf-icnrg-videostreaming]
cedric.westphal@huawei.com, c., Lederer, S., Mueller, C.,
Detti, A., Corujo, D., Wang, J., Montpetit, M., Murray,
N., Timmerer, C., Posch, D., aytav.azgin, a., and S.
(Will), "Adaptive Video Streaming over ICN", draft-irtf-
icnrg-videostreaming-08 (work in progress), April 2016.
[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>.
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Appendix A. Acknowledgments
The authors would like to thank Christian Tschudin for providing
suggestions on the structure of the document and some of the ICN
related terms.
Authors' Addresses
Bastiaan Wissingh
TNO
EMail: bastiaan.wissingh@tno.nl
Christopher Wood
PARC
EMail: christopher.wood@parc.com
Lixia Zhang
UCLA
EMail: lixia@cs.ucla.edu
Alex Afanasyev
UCLA
EMail: aa@cs.ucla.edu
David Oran
Cisco Systems, Inc.
EMail: oran@cisco.com
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