Dirk Kutscher

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Information-Centric Networking RFCs on CCNx Published

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The Internet Research Task Force (IRTF) has published two Experimental RFCs specifying the node behavior, message semantics, and the message syntax of the CCNx protocol: RFC 8569 (Content-Centric Networking (CCNx) Semantics) and RFC 8609 (Content-Centric Networking (CCNx) Messages in TLV Format). CCNx is one particular variant of ICN protocols. These specifications document the implementation of an available Open-Source implementation and are intended to encourage additional experiments with Information-Centric Networking technologies.

Background

Information-Centric Networking (ICN) is a class of architectures and protocols that provide “access to named data” as a first-order network service. Instead of host-to-host communication as in IP networks, ICNs often use location-independent names to identify data objects, and the network provides the services of processing (answering) requests for named data with the objective to finally deliver the requested data objects to a requesting consumer.

Such an approach has profound effects on various aspects of a networking system, including security (by enabling object-based security on a message/packet level), forwarding behavior (name-based forwarding, caching), but also on more operational aspects such as bootstrapping, discovery etc.

The CCNx and NDN variants of ICN are based on a request/response abstraction where consumers (hosts, applications requesting named data) send INTEREST messages into the network that are forwarded by network elements to a destination that can provide the requested named data object. Corresponding responses are sent as so-called DATA messages that follow the reverse INTEREST path.

Sometimes ICN has been mis-characterized as a solution for in-network caching, possibly replacing CDN. While ICN’s location-independent access and its object-security approach does indeed enable opportunistic in-network data caching (e.g., for local retransmissions, data sharing), it is actually not the main feature — it is actually rather a consequence of the more fundamental properties of 1) accessing named data, 2) object-security and integrated trust model, and 3) stateful forwarding.

Accessing Named Data

Each unique data object is named unambiguously in a hierarchical naming scheme and can be validated in a means specified by the producer, i.e., the origin source. (Data objects can also optionally be encrypted in different ways). The naming concept and the object-based validation approach lay the foundation for location independent operation, because data validity can be ascertained by any node in the network, regardless of where the corresponding messages was received from.

The network can generally operate without any notion of location, and nodes (consumers, forwarders) can forward requests for named data objects directly, i.e., without any additional address resolution. Location independence also enables additional features, for example the possibility to replicate and cache named data objects. Opportunistic on-patch caching is thus a standard feature in many ICN systems — typically for enhancing reliability and performance.

Naming data and application-specific naming conventions are naturally important aspects in ICN. It is common that applications define their own naming convention (i.e., semantics of elements in the name hierarchy). Such names can often directly derived from application requirements, for example a name like /my-home/living-room/light/switch/main could be relevant in a smart home setting, and corresponding devices and application could use a corresponding convention to facilitate controllers finding sensors and actors in such a system with minimal user configuration.

Object-Security and Integrated Trust Model

One of the objection validation approaches is based on Public-Key cryptography, where publishers sign objects (parts of messages) and can name the Public Key in the message, so that a validator can retrieve the corresponding object (containing the Public Key and a certificate that would bind the key to a naming hierarchy). The certificate would be an element of a typical trust hierarchy.

Public-Key cryptography and PKI systems are also used in the Internet/Web today. In CCNx/NDN-based ICN, the key/certificate retrieval is directly provided by the network itself, i.e., it uses the same INTEREST/DATA protocol, and the system is typically used in a way that every object/message can be linked to a trust anchor.

Where that trust anchor resides is defined by the application semantics and its naming conventions. Unlike the Internet/Web today, it is not required to link to centralized trust anchors (such as root Certificate Authorities) — instead it is possible to set up local, decentralized trustworthy networked systems in a permissionless manner.

Stateful Forwarding

In CCNx and NDN, forwarders are stateful, i.e., they keep track of forwarded INTEREST to later match the received DATA messages. Stateful forwarding (in conjunction with the general named-based and location-independent operation) also empowers forwarders to execute individual forwarding strategies and perform optimizations such as in-network retransmissions, multicasting requests (in cases there are several opportunities for accessing a particular named data object) etc.

Stateful forwarding enables nodes in the network to perform similar function as endpoints (i.e., consumers), so that there is not a strong distinction between these roles. For example, consumers and forwarders can control INTEREST sending rates to respond to observed network conditions. Adapting in-network transport behavior can thus be achieved naturally, i.e., without brittle, in-transparent middleboxes, TCP proxies etc.

ICN Scenarios

ICN is a general-purpose networking technologies and can thus be applied to many scenarios. I am highlighting a few particularly interesting ones in the following sections.

Scalable Media Distribution

The “Accessing Named Data” paradigm also implies that CCNx/NDN-based ICN is fundamentally connectionless. While there can be collections of Named Data Objects that are requested (and transmitted) in a flow-like manner (as a consecutive series, sharing paths), a server (producer) does not have to maintain any client or connection state — one factor for making servers more scalable.

ICN forwarders can aggregate INTEREST received from different (for example, downstream) links for the same Named Data Object. Instead of forwarding the second, third etc. INTEREST for the same object, a forwarder (as part of its forwarding strategy) could decide to just record those INTERESTS (and note the interfaces they have been received from) and then later distribute the received object via all of these interfaces.

For live or near-live media distribution, this can enable an additional factor for scalability: 1) less INTERESTs are hitting the producers and 2) less INTEREST and DATA messages are transmitted over the network. Effectively, this behavior implement an implicit multicast-like tree-based distribution — without any explicit signaling and (inter-domain) multicast routing.

Finally in-network caching can further reduce upstream traffic, i.e., by answering requests for currently popular objects from a forwarder cache.

The corresponding gains have been demonstrated in Proof-of-Concept implementations, for example in Cisco’s hICN DASH-like video distribution system.

Multi-Access & Multi-Path Networking

Multi-Access networking is getting increasingly important as most mobile devices already provide at least two radio interfaces that can be used simultaneously. For example Apple’s Siri can use Multipath TCP for trying to obtain better performance by combining mobile network and WLAN interfaces and by jointly managing the available resources.

ICN communication is inherently multipath in a sense that ICN is not connection-based and that any forwarder can make independent forwarding decisions for multipath INTEREST forwarding. ICN’s location independence also enables a multidestination communication style: Named Data Object can be replicated in the network, so that the network could not only provide different paths to one producer but to many producers, which can increase network utilization and performance further.

These properties in conjunction with ICN’s stateful forwarding model enables several optimizations (both for window- as well as rate-based congestion controlled multipath communication) of MPTCP’s end-to-end control loop. An example of such an approach has been described by Mahdian et al..

Internet of Things (IoT)

IoT is a broad field, but often refers to 1) networking constrained devices and 2) communicating in local networks (that are not or should not be connected to the Internet on a permanent basis).

In low-power wireless networks with challenged connectivity, frequent power-saving and potentially node mobility, ICN can typically outperform IP-based technology stacks with respect to implementation simplicity, data availability and performance. The implementation simplicity stems from the ICN model of accessing named data directly, i.e., with integrated security and without the need for any resolution infrastructure and application layer protocols (in some IoT scenarios).

The data availability and performance improvements are caused by the stateful forwarding and opportunistic caching feature that are useful for multi-hop mesh networks with frequent connectivity changes due to sleep cycles and mobility. The stateful forwarding enables ICN to react more flexibly to changes, and in-network caching can keep data available in the network so that it can be retrieved at some time offset, for example when a sleeping wakes up and resumes communication with a next-hop node. Gündoğan et al. have performed an extensive analysis comparing NDN with CoAP and MQTT on large-scale IoT testbeds that demonstrated these benefits.

Computing in the Network

Recent advances in platform virtualization, link layer technologies and data plane programmability have led to a growing set of use cases where computation near users or data consuming applications is needed — for example for addressing minimal latency requirements for compute intensive interactive applications (networked Augmented Reality, AR), for addressing privacy sensitivity (avoiding raw data copies outside a perimeter by processing data locally), and for speeding up distributed computation by putting computation at convenient places in a network topology.

Most application layer frameworks suffer from being conceived as overlays, i.e., they can enable certain forms of optimization (such as function placement, scaling) — but do typically require centralized orchestration. Running as an overlay means, connecting compute functions through protocols such as TCP, requiring some form of resolution system that maps application-layer names to IP addresses etc.

Approaches such as Named Function Networking (NFN) and Remote Method Invocation for ICN (RICE) have demonstrated how the ICN approach of accessing named data in the network can be extended to accessing dynamic computation results, maintaining all the ICN security and forwarding/caching properties.

In such systems, computing and networking can be integrated in new ways, for example by allowing compute node to include knowledge about the ICN networks routing information base, currently observed availability and performance data for making offloading and scaling decisions. Consequentially, this enables a promising joint optimization of computing and networking resource that is especially attractive for fine-granular distributed system development.

Also see draft-kutscher-coinrg-dir for a general discussion of Computing in the Network.

The CCNx Specifications

The work on CCN started about 11 years ago in project led by Van Jacobson at PARC — in parallel with many other research projects on ICN such as NetInf, PURSUIT etc. The CCN work split up into branches later: NDN (maintained by the NDN NSN projects) and CCNx (maintained by PARC).

In 2016, Cisco acquired the CCNx technology and the software implementations from PARC and continued working on them in research and proof-of-concepts, and trials. The software has been made available as a sub-project in the fd.io project and is now called CICN, featuring support for the VPP framework in fd.io.

This implementation largely follows the specification in the now published CCNx RFCs which are products of the IRTF ICN Research Group.

RFC 8569 describes the core concepts of the Content-Centric Networking (CCNx) architecture and presents a network protocol based on two messages: Interests and Content Objects. It specifies the set of mandatory and optional fields within those messages and describes their behavior and interpretation. This architecture and protocol specification is independent of a specific wire encoding.

RFC 8609 specifies the encoding of CCNx messages in a TLV packet format, including the TLV types used by each message element and the encoding of each value. The semantics of CCNx messages follow the encoding-independent CCNx Semantics specification.

Both of these RFCs have been authored by Marc Mosko, Nacho Solis, and Chris Wood.

More Information

The IRTF ICN Research Group is an international research forum that covers research and experimentation work across the different ICN approaches and projects. Its goal is to promote experimentation and validation activities with ICN technology.

There is also a yearly academic conference under the ACM SIGCOMM
umbrella. The 2019 ICN conference takes place from September 24 to 26 in HongKong. Previous editions of the conference:

Written by dkutscher

July 11th, 2019 at 3:02 pm

Posted in Blogroll,IRTF

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New Proposed Decentralized Internet Infrastructure Research Group

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New Proposed Decentralized Internet Infrastructure Research Group

The Internet was designed as a distributed, decentralized system. For example, intra- and inter-domain routing, DNS, and so on were designed to operate in a distributed manner. However, over time the dominant deployment model for applications and some infrastructure services evolved to become more centralized and hierarchical. Some of the increase in centralization is due to business models that rely on centralized accounting and administration.

However, we are simultaneously seeing the evolution of use cases (e.g., certain IoT deployments) that cannot work (or which work poorly) in centralized deployment scenarios along with the evolution of decentralized technologies which leverage new cryptographic infrastructures, such as DNSSEC, or which use novel, cryptographically-based distributed consensus mechanisms, such as a number of different ledger technologies. For example, these use cases include identity/trust management leveraging reputation for authentication, authorization and decentralized management of shared resources.

The evolution of distributed ledger technologies and the platforms that leverage them has given rise to the development of decentralized communication and infrastructure systems, and experiments with the same. Some examples include name resolution (Namecoin, Ethereum Name Service), identity management (OneName), distributed storage (IPFS, MaidSafe), distributed applications, or DApps (Blockstack), and IP address allocation and delegation.

These systems differ with respect to the problem they are solving, the specific technologies that they apply, the consensus algorithms that are employed, and the incentives that are built into the system. Now is a good time to investigate these systems from an Internet technologies perspective, and to connect the domain expertise in the IRTF and IETF with the distributed systems and decentralized ledgers community.

Proposed IRTF DINRG

In the past months we have been working on a proposal for a new Research Group in the Internet Research Task Force. The Decentralized Internet Infrastructure Research Group (DINRG) will investigate open research issues in decentralizing infrastructure services such as trust management, identity management, name resolution, resource/asset ownership management, and resource discovery. The focus of DINRG is on infrastructure services that can benefit from decentralization or that are difficult to realize in local, potentially connectivity-constrained networks.

The objective of DINRG is to 1) investigate (understand, document, survey) use cases and their specific requirements with respect to implementing them in a distributed manner; 2) to discuss and assess solutions for specific use cases with a focus on Internet level deployment issues such as scalability, performance, and security; 3) to develop and document technical solutions and best practices; 4) to develop tools and metrics to identify scaling issues and to determine whether components are missing; and 5) to identify future work items for the IETF.

Other topics of interest are the investigation of economic drivers and incentives and the development and operation of experimental platforms. DINRG will operate in a technology- and solution-neutral manner, i.e., while the RG has an interest in distributed ledger technologies, it is not limited to specific technologies and or implementation aspect. We expect DINRG to advance the state of the art with respect to fostering a better understanding of the merits and constraints of specific technologies with respect to the DINRG use cases.

If you are interested to discuss these topics, please have a look at the complete charter text and subscribe to the mailing list.

Resources

 

Written by dkutscher

October 17th, 2017 at 5:06 pm

Posted in IRTF