Dirk Kutscher

In the Information-Centric Networking Research Group (ICNRG) of the Internet Research Task Force (IRTF) we have recently published a set of new RFCs:

RFC 9510: Alternative Delta Time Encoding for Content-Centric Networking (CCNx) Using Compact Floating-Point Arithmetic

Content-Centric Networking (CCNx) utilizes delta time for a number of functions. When using CCNx in environments with constrained nodes or bandwidth-constrained networks, it is valuable to have a compressed representation of delta time. In order to do so, either accuracy or dynamic range has to be sacrificed. Since the current uses of delta time do not require both simultaneously, one can consider a logarithmic encoding. This document updates RFC 8609 ( to specify this alternative encoding.

RFC 9531: Path Steering in Content-Centric Networking (CCNx) and Named Data Networking (NDN)

Path steering is a mechanism to discover paths to the producers of Information-Centric Networking (ICN) Content Objects and steer subsequent Interest messages along a previously discovered path. It has various uses, including the operation of state-of-the-art multi-path congestion control algorithms and for network measurement and management. This specification derives directly from the design published in https://dl.acm.org/doi/10.1145/3125719.3125721 (4th ACM Conference on Information-Centric Networking) and, therefore, does not recapitulate the design motivations, implementation details, or evaluation of the scheme. However, some technical details are different, and where there are differences, the design documented here is to be considered definitive.

RFC 9508: Information-Centric Networking (ICN) Ping Protocol Specification

This document presents the design of an Information-Centric Networking (ICN) Ping protocol. It includes the operations of both the client and the forwarder.

Ascertaining data plane reachability to a destination and taking coarse performance measurements of Round-Trip Time (RTT) are fundamental facilities for network administration and troubleshooting. In IP, where routing and forwarding are based on IP addresses, ICMP Echo Request and ICMP Echo Reply packets are the protocol mechanisms used for this purpose, generally exercised through the familiar ping utility. In Information-Centric Networking (ICN), where routing and forwarding are based on name prefixes, the ability to ascertain the reachability of names is required.

In order to carry out meaningful experimentation and deployment of ICN protocols, new tools analogous to ping and traceroute used for TCP/IP are needed to manage and debug the operation of ICN architectures and protocols. This document describes the design of a management and debugging protocol analogous to the ping protocol of TCP/IP; this new management and debugging protocol will aid the experimental deployment of ICN protocols. As the community continues its experimentation with ICN architectures and protocols, the design of ICN Ping might change accordingly. ICN Ping is designed as a "first line of defense" tool to troubleshoot ICN architectures and protocols. As such, this document is classified as an Experimental RFC. Note that a measurement application is needed to make proper use of ICN Ping in order to compute various statistics, such as average, maximum, and minimum Round-Trip Time (RTT) values, variance in RTTs, and loss rates.

RFC 9507: Information-Centric Networking (ICN) Traceroute Protocol Specification

This document presents the design of an Information-Centric Networking (ICN) Traceroute protocol. This includes the operation of both the client and the forwarder.

In TCP/IP, routing and forwarding are based on IP addresses. To ascertain the route to an IP address and to measure the transit delays, the traceroute utility is commonly used. In Information-Centric Networking (ICN), routing and forwarding are based on name prefixes. To this end, the ability to ascertain the characteristics of at least one of the available routes to a name prefix is a fundamental requirement for instrumentation and network management. These characteristics include, among others, route properties such as which forwarders were transited and the delay incurred through forwarding.

In order to carry out meaningful experimentation and deployment of ICN protocols, new tools analogous to ping and traceroute used for TCP/IP are needed to manage and debug the operation of ICN architectures and protocols. This document describes the design of a management and debugging protocol analogous to the traceroute protocol of TCP/IP; this new management and debugging protocol will aid the experimental deployment of ICN protocols. As the community continues its experimentation with ICN architectures and protocols, the design of ICN Traceroute might change accordingly. ICN Traceroute is designed as a tool to troubleshoot ICN architectures and protocols.

In most Internet (two-party) communication scenarios, we have to deal with connection setup protocols, for example for TCP (three-way handshake), TLS (three-way key agreement), HTTP (leveraging TLS/TCP before GET-RESPONSE). The most important concern is to make sure that both parties know that they have succesfully established a connection and to agree on its parameters.

In client-server communication, there are other, application-layer, requirements as well, for example authenticating and authorizing peer and checking input parameters. Web applications today, typically serve a mix of static and dynamic content, and the generation of such dynamic content requires considerable amount of client input (as request parameters), which in results in considerable amounts of data (Google: "Request headers today vary in size from ~200 bytes to over 2KB.", SPDY Whitepaper).

When designing connection establishment protocols and their interaction with higher layer protocols, there are a few, sometimes contradicting objectives:

• fast connection setup: calls for minimizing the number of round-trips;
• reliable connection and security context setup: reliable state synchronization requires a three-way handshake); and
• robustness against attacks from unauthorized or unwanted clients: could be done by filtering connection attempts, by authentication checks, or other parameter checks on the server.

The goal to minimize the number of round-trips can contradict with robustness: For example, in a dynamic web content scenario, spawning a server worker thread for processing a malicious client request that will have to be declined can be huge resource waste and thus make the services susceptible to DOS attacks.

These are general trade-offs in many distributed computing and web-based systems. In Information-Centric Networking (ICN), there can be additional objectives such as maintaining client (consumer) anonymity (to the network) to avoid finger-printing and tracking (ICN does not have source addresses).

Current ICN protocols such as CCNx and NDN have a wide range of useful applications in content retrieval and other scenarios that depend only on a robust two-way exchange in the form of a request and response (represented by an Interest-Data exchange in the case of the two protocols noted above).

A number of important applications however, require placing large amounts of data in the Interest message, and/or more than one two-way handshake. While these can be accomplished using independent Interest-Data exchanges by reversing the roles of consumer and producer, such approaches can be both clumsy for applications and problematic from a state management, congestion control, or security standpoint.

For RICE, Remote Method Invocation for ICN, we developed a corresponding scheme that addresses the different objectives mentioned above.

In draft-oran-icnrg-reflexive-forwarding we have now provided a formal specification of a corresponding Reflexive Forwarding extension to the CCNx and NDN protocol architectures that eliminates the problems inherent in using independent Interest-Data exchanges for such applications. It updates RFC8569 and RFC8609.

The approach that we have taken here is to extend the ICN forwarding node requirements, so in addition to the general state synchronization problems, this Internet Draft raises the question of evolvability of core ICN protocols.

Discussion on the ICNRG mailing list.

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:

• ACM ICN 2014
• ACM ICN 2015
• ACM ICN 2016
• ACM ICN 2017
• ACM ICN 2018

I presented GreenICN work on Scalable Content Exchange in Challenged ICNs at CCNxCon-2015 this week.

Download: ccnxcon2015-kutscher.pdf

Abstract:
The principles of Information­Centric Networking (ICN), accessing data objects by name (not by location address), securing data objects (not connections), in­network caching (for sharing, repair, rate adaptation) make ICN attractive for a wide range of application scenarios beyond traditional data center or telco access network scenarios. In fact, one of the first instantiation of ICN had been developed based on Delay­Tolerant Networking (DTN) technologies.

Currently, ICN/DTN is considered a promising approach for enabling/enhancing communication in disaster scenarios. In such scenarios, so­called ICN data mules (that carry and disseminate data times) may move randomly, and each time data mules encounter one another exchange data items. We envision that in such a scenario where there is no connectivity, data mules (e.g. vehicles or drones) can move around randomly. So these mobile routers interact with end users, working base stations and other data mules to fetch and deliver the data and queries. Thus, we do not consider adhoc networks where you can build a path to the destination reactively or proactively, rather a DTN like scenario.

Consider a large scale disaster scenario like the earthquake in Japan in 2011 , where people in different parts of the city are stranded without the internet connectivity. But there are some zones, where base stations are still working and providing connectivity. Essentially, the scenario is such that ICN data mule move randomly across a geographic area, and when meeting end­users receive interests from them and also forward corresponding data items to end­users (if present in the content store / cache of the data mule). At the same time, when data mules encounter each other, they forward to each other certain end­user interest and/or data items (according to a predefined rule set and algorithm), such that interests and data items can be forwarded in a hop­by­hop DTN fashion. One research problem in such a scenario is how to optimize such data exchanges among data mules for optimal data dissemination (e.g. optimizing how many desired messages reach their recipients within a given timeframe with a given forwarding strategy, assuming that data mules only have limited time at each encounter to exchange
messages).