Dirk Kutscher

Low-power, long-range radio systems such as LoRaWAN represent one of the few remaining networked system domains that still feature a complete vertical stack with special link- and network layer designs independent of IP. Similar to local IoT systems for low-power networks (LoWPANs), the main service of these systems is to make data available at minimal energy consumption, but over longer distances. LoRaWAN (the system that comprises the LoRa PHY and MAC) supports bi-directional communication, if the IoT device has the energy budget. Application developers interface with the system using a centralized server that terminates the LoRaWAN protocol and makes data available on the Internet.

While LoRaWAN applications are typically providing access to named data, the existing LoRaWAN stack does not support this way of communicating. LoRaWAN is device-centric and is generally designed as a device-to-server messaging system – with centralized servers that serve as rendezvous point for accessing sensor data. The current design imposes rigid constraints and does not facilitate accessing named data natively, which results in many point solutions and dependencies on central server instances.

In our demo paper & presentation at ACM ICN-2020, we are therefore describing how Information-Centric Networking could provide a more natural communication style for LoRa applications and how ICN could help to conceive LoRa networks in a more distributed fashion compared to todays mainstream LoRaWAN deployments. For LoWPANs (e.g., 802.15.4 networks), ICN has already demonstrated to be an attractive and viable alternative to legacy integrated special purpose stacks – we believe that
LoRa communication provides similar opportunities.

Watch my Peter Kietzmann’s talk about it here:

ACM ICN-2020 took place online from September 29th to October 1st 2020. This is a quick summary of the main technical highlights from my personal perspective. Overall, it was a high-quality event, and it was great to see the progress that is being made by different teams. Here, I am focusing specifically on Architecture, Content Distribution, Programmability, and Performance. If you are interested in the complete program, all papers, presentation material, and presentation videos are available on the conference website.

Architecture

The Information-Centric Networking concept can be implemented in different ways (and some people would argue that some overlay systems for content distribution and data processing are essentially information-centric). ICN systems have often been associated with clean-slate approaches, requiring difficult to imagine fork-lift replacement of larger parts of the infrastructure. While this has never the case (because you can always run ICN protocols over different underlays or directly map the semantics to IPv6), it is still interesting to learn about new approaches and to compare existing data-oriented frameworks to pure ICN systems.

Named-Data Transport

In their paper Named-Data Transport: An End-to-End Approach for an Information-Centric IP Internet (Presentation) Abdulazaz Albalawi and J. J. Garcia-Luna-Aceves have developed an alternative implementation of the accessing named data concept called Named-Data Transport (NDT) that can leverage existing Internet routing and DNS, while still providing the general properties (accessing named-data securely, in-network caching, receiver-driven operation).

The system is based on three components: 1) A connection-free reliable transport protocol, called Named Data Transport Protocol (NDTP), 2) a DNS extension (my-DNS) for manifest records that describe content items and their chunks, and 3) NDT Proxies that act as transparent caches and that track pending requests, similar to ICN forwarders, but at the transport layer.

In NDT, content names are based on DNS domain names, and each name is mapped to an individual manifest record (in the DNS). These records provide a mapping to a list of IP addresses hosting content replicas. When requesting such records, the idea is that the system would be able apply similar traffic steering as today’s CDNs, i.e., provide the requestor with a list of topologically close locations. Producers would be responsible for producing and publishing such manifests.

The Named Data Transport Protocol (NDTP) is a receiver-driven transport protocol (on top of UDP) used by consumers and NDT Proxies which behave logically like ICN forwarders. There is more to the whole approach (such as security, name privacy etc.).

In my view, NDT is an example of a resolution-based ICN system with interesting ideas for deployability. In principle, resolution-based ICN has been pursued by other approaches before (such as NetInf). In general, these systems have a better initial deployment story at the cost of requiring additional infrastructure (and resolution steps during operation.)

RESTful Information-Centric Web of Things

In the Internet of Things, ICN has demonstrated many benefits in terms of reduced code complexity, better data availability, and reduced communication overhead compared to many vertically integrated IoT stacks and location/connection-based protocols.

In their paper Toward a RESTful Information-Centric Web of Things: A Deeper Look at Data Orientation in CoAP (presentation), Cenk Gündoğan, Christian Amsüss, Thomas C. Schmidt, and Matthias Wählisch compare a CoAP and OSCORE (Object Security for Constrained RESTFul Environments) based network of CoAP clients, servers, and proxies with a corresponding NDN setup.

The authors investigated the possibility of building a restful Web of Things that adheres to ICN first principles using the CoAP protocol suite (instead of a native ICN protocol framework). The results showed, since CoAP is quite modular and can be used in different ways, this is indeed possible, if one is willing to give up strict end-to-end semantics and to introduce proxies that mimic ICN forwarder behavior. (The paper reports on many other things, such as extensive performance measurements and comparisons.)

In my view, this is an interesting Gedankenexperiment, and there was a lively discussion at the conference. One of the discussion topics was the question how accurate the comparison really is. For example, while is is possible to construct a CoAP proxy chain that mimics ICN behavior, real-world scenarios would require additional functionality in the CoAP network (routing, dealing with disruptions etc.) that might lead to a different level of complexity (that would possibly be less pronounced in an native ICN environment).

Still, the important take-away of this paper is that some applications of CoAP & OSCORE exhibit information-centric properties, and it is an interesting question whether, for a green-field deployment, the user would not be better served by a native ICN approach.

Content Distribution

Content Distribution and ICN have a long history, sometimes challenged by some misunderstandings. Because one of the early ICN approaches was called Content-Centric Networking (CCN), it was often assumed that ICN would disrupt or replace Content Distribution Networks (CDNs) or that it was a CDN-like technology.

While ICN will certainly help with large-scale content distribution and potentially also change/simplify CDN operations, the core idea is actually about accessing named data securely as a principal network service — for all applications (that’s why Named Data Networking — NDN — is a better name).

Managed content distribution as such will continue to be important, even in an ICN world. Surely, it will enjoy better support from the network as today’s CDN can expect, thus enabling new exciting applications and simplifying operations, but I prefer avoiding the notion of ICN replacing CDN.

When looking at actual networks and applications today, it is fair to say that almost nothing works without CDN. What we are seeing today is hyperscalers and essentially all the (so-called) OTT video providers extending their systems into ISP networks, by simply shipping standalone edge caches such as Netflix OCA servers as standalone systems to ISPs.

Each of these providers have their own special requirements of how to map customers to edge caches, how to implement traffic steering etc, which is painful enough for operators already. I expect this to become even more pressing as we shift more and more linear live TV to the Internet. Flash-crowd audiences such as viewers of UEFA Champions’ League matches will require a massive extension of the already extensive edge caching infrastructure and require massive investments but also significant complexity with respect to traffic steering and guaranteeing a decent viewing experience.

In that context, it is no wonder that people try to resort to IP-Multicast for ensuring a more scaleable last-mile distribution such as this proposal by Akamai and others. Marrying IP-Multicast with a CDN-overlay is (IMO) not exactly complexity reduction, so I think we are now at a tipping point where the Internet in terms of concepts and deployable physical infrastructure can provide many cool services, but where the limited features of the network layers requires a prohibitive amount of complexity — to an extend where people start looking for better solutions.

At ICN-2020, CDN was thus discussed quite extensively again — with many interesting, complementary contributions.

Keynote by Bruce Maggs on The Economics of Content Distribution

We were extremely happy to have Bruce Maggs (Emerald Innovations, on leave from Duke University, ex NEC researcher, one of the founding employees of Akamai) delivering his keynote on the Economics of Content Delivery. In his talk Bruce explained different economic aspects (flow of payments, cost of goods sold) but also challenges for different CDN services such as live-streaming.

The take-aways for ICN were:

• Incentives and cost must be aligned
• Performance benefits from caching
  • Reducing latency is valuable to content providers
  • Reducing network is valuable to ISPs.
• If there was caching at the core (in addition to the edge)
  • What is the additional benefit?
  • Who pays for that?
• Protocol innovation is still possible
  • In the past, people thought that HTTP/TLS/TPC/IP is difficult to overcome
  • QUIC demonstrates that new protocols can be introduced

The socio-economic discussion resonated quite well with me, as some of earlier ICN projects in Europe tried to address these aspects relatively early in 2008. I believe this was due to the operator and vendor influence at the time. In retrospect, I would say that the approaches at that time were possibly too much top-down and premature (trying to revert value chains and find new business models). It is only now that we understand the economics of CDN, its complexity and real cost that (in my view) represent barriers to innovation — and that we can start to imagine actually implementing different systems.

Far Cry: Will CDNs Hear NDN’s Call?

In their paper Far Cry: Will CDNs Hear CDN’s Call? (presentation), Chavoosh Ghasemi, Hamed Yousefi, and Beichuan Zhang tried to compare NDN with enterprise CDN (a particular variant of CDN) with respect to caching and retrieval of static contents.

In their work, the authors deployed an adaptive video streaming service over three different networks: Akamai, Fastly, and the NDN testbed. They had users in four different continents and conducted a two-week experiment, comparing Quality of Experience, Origin workload, failure resiliency, and content security.

I cannot summarize of all of the results here, but the conclusions by the authors were:

• CDNs outperform the current NDN testbed deployment in terms of QoE (achievable video resolution in a DASH-setting)
• Origin workload and failure resiliency are mainly the products of the network design — and the NDN testbed outperforms current CDNs
• More as an interpretation: NDN can realize a resilient, secure, and scalable content network given appropriate software and protocol maturity and hardware resources.

The paper was discussed intensively at the conference , for example, it was debated how comparable the plain NDN testbed and its network service really are — to a production-level CDN.

In my view, the value of this paper lies in the created experiment facilities and the attempt to establish some ground truth (based on current NDN maturity). I hope that this work can leverage by more experiments in the future.

iCDN: An NDN-based CDN

In their paper iCDN: An NDN-based CDN (presentation), Chavoosh Ghasemi, Hamed Yousefi, and Beichuan Zhang (i.e., the same authors), pursue a more forward-looking approach. In this paper, they develop a CDN service based on ICN mechanisms, i.e., trying to conceive a future CDN system that does not need to take the current network’s limitations into account.

One of the interesting ICN properties is that the main service of accessing named data does not require any notion of location. Sometimes people assume that an Information-Centric system always needs to map names to locators such as IP addresses, but this is a really limited view. Instead, it is possible to build the network solely on forwarding INTERESTs for named data based on forwarding information of that same namespace. A forwarder may have more than forwarding info base entry for the same name — from a consumer (application) perspective these are completely equivalent.

Because of intrinsic object security, it does not matter from which particular host a content object is served. There can be several copies — all equivalent. When creating copies of original content, e.g., by cloning a data repository, the new copy needs to be announced (by injecting routing information) , and from that point on, it is reachable without any additional management, configuration or other out-of-band mechanisms.

When applying this notion to CDN scenarios, it is easy to understand the simplification opportunities. In ICN, content repositories can be added to the network, and in-network name-based forwarding will find the closest copy automatically.

For iCDN, the authors have leveraged this basic notion and built an ICN-based CDN that does not need any client-to-cache mapping and overlay routing mechanisms. Based on that, iCDN features logical partitions and cache hierarchies for content namespaces (for acknowledging that there may be different CDN providers, hosting different content services).

iCDNs employ cache hierarchies to exploit on-path and off-oath caches without relying on application-layer routing functions. The idea was to provide a scalable, adaptive solution that can cope with dynamic network changes as well as dynamic changes in content popularity.

There are more details to this approach, and of course the debate on what is the best ICN-based CDN design has just started. Still, this paper is an interesting contribution in my view, because it illustrates the opportunities for rethinking CDN nicely.

Programmability

Programmability and ICN has two facets: 1) Implementing distributed computing with ICN (for example as in CFN — Compute-First Networking) and 2) implementing ICN with programmable infrastructure. ACM ICN-2020 has seen contributions in both directions.

Result Provenance in Named Function Networking

In their paper Result Provenance in Named Function Networking (presentation), Claudio Marxer and Christian Tschudin have leveraged their previous work on Named Function Networking (NFN) and developed a result provenance framework for distributed computing in NFN.

In this work, the authors augmented NFN with a data structure that creates transparency of the genesis of every evaluation results so that entities in the system can ascertain result provenance. The main idea is the introduction of so-called provenance records that capture meta data about the genesis of the computation result. The paper discusses integration of these records into NDN and procedures for provenance checks and trust computation.

In my view, the interesting contribution of this work is the illustration of how the general concept of provenance verification can be implemented in a data-oriented system such as the ICN-based Named Function Networking framework. The results may be (so some extend) to other ICN-based in-network computing systems, so I hope this paper will start a thread of activities on this subject.

ENDN: An Enhanced NDN Architecture with a P4-programmable Data Plane

In their paper ENDN: An Enhanced NDN Architecture with a P4-programmable Data Plane (presentation), Ouassim Karrakchou, Nancy Samaan, and Ahmed Karmouch present an NDN system that is implemented in a P4-programmable data plane, i.e., a system in which applications can interact with a control plane that configures the data plane according to the required services.

The work in this paper is based on the notion that applications specify their content delivery requirements to the network, i.e., the control plane of a network. The control plane provide a catalogue of content delivery services, which are then translated into data plane configurations that ultimately get installed on P4 switches.

Examples of such services include Content Delivery Pattern services (whether the system is based on INTEREST/DATA or some stateful data forwarding), Content Name Rewrite services (enabling the network to rewrite certain names in INTERESTs), Adaptive Forwarding services (next-hop selection) etc.

In my view, this paper is interesting because it provides a relatively advanced perspective of how applications specify required behavior to a programmable ICN network. Moreover, the authors implemented this successfully on P4 switches and described relevant lessons learned and achievements in the paper.

Performance

Performance has historically always been an interesting topic in ICN. On the one hand, ICN provides substantial performance increases in the network due to its forwarding and caching features. On the other hand, it has been shown that implementing an ICN forwarder that operates at modern network line-speeds is challenging.

NDN-DPDK: NDN Forwarding at 100 Gbps on Commodity Hardware

In their paper NDN-DPDK: NDN Forwarding at 100 Gbps on Commodity Hardware (presentation), Junxiao Shi, Davide Pesavento, and Lotfi Benmohamed present their design of a DPDK-based forwarder.

The authors have developed a complete NDN implementation that runs on real hardware and that supports the complete NDN protocol and name matching semantics.

This work is interesting because the authors describe the different optimization techniques including better algorithms and more efficient data structures, as well as making use of the parallelism offered by modern multi-core CPUS and multiple hardware queues with user-space drivers for kernel-bypass.

This work represents the first software forwarder implementation that is able to achieve 100 Gpbs without compromises in NDN protocols semantics. The authors have published the source at https://github.com/usnistgov/ndn-dpdk.

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.

Many university-level teachers have switched or will have to switch to online teaching and coaching. My university switched relatively seamlessly a few weeks ago already, and I have a received quite a few requests for advice, so let me share some thoughts here.

The TL;DR summary:

• keep calm and carry on;
• understand your objectives and teaching methodology;
• balance technology and didactics concerns;
• avoid tool chaos;
• use existing infrastructure;
• understand scalability requirements and infrastructure constraints;
• record everything;
• leverage new possibilities;
• and if you have pick one online teaching tool, use BigBlueButton (see below).

First of all, it’s interesting to see how different universities in different countries approach the covid-19 crisis. Some have switched immediately to online teaching (or just extended their already existing online courses). Others announced extended Easter breaks, and there are even discussions of just canceling the summer term.

While the prospect of Corona holidays (or just more time for other work) may sounds attractive, I would strongly advise against it for two reasons:

1. Extended breaks, suspended periods of teaching etc., will most likely result in more stress for everybody (professors, students, admin staff) later. In a situation with many uncertainties that may well hurt us more in the end.
2. The lock-down (in whatever regional variant) is necessary, but it’s obvious that you cannot lock down everything (hospitals, food production etc.). Every social and business activity that is locked down will hurt society in some way. There are some activities that cannot continue right now and absolutely have to be suspended to avoid community transmission, which is causing enough problems (small shops, artists but also larger scale factories). Luckily, there are some professions that can be re-organized and continue in some way — university-level teaching is one of those. These activities should continue just to minimize societal damage.

In my university, the term started on March 1st. Luckily, the executive leadership had been quite up-to-speed regarding covid-19-related measures in the weeks before in terms of communication, sanitation, travel advice etc. When the federal state of Lower Saxony in Germany announced the suspension of presence-based teaching in universities in schools on March 13th, it did not come unexpected, and we continued most courses online in the next weeks.

Obviously, not everything went perfectly, and there were a few lessons learned that I will summarize in the following. I do research and teaching in Networked Systems (Computer Science), so there is a certain technology bias here.

Avoid Tool Chaos — Use Existing Infrastructure as Much as Possible

Most universities are using some kind of learning management or e-learning system such as Moodle. They are never perfect of course, but it is really a good idea to use them as much as possible, because:

• your students are already enrolled and typically know the system well;
• Moodle and similar systems provide a ton of collaboration features that you may have ignored so far but that are really useful such as Wikis, forums, etc. They may not always be super-fancy as some individual externally-hosted services — but think about your priorities in crisis times…
• Your learning management and e-learning systems are production tools that contribute to your university’s core business, so there is a good probability that they are actually well-provisioned and well maintained — good in times of fast-growing demand.

Of course everyone has their favorite Wiki, shared editing, online collaboration tool etc., but just going for these incurs cost on two sides:

• You have to select, assess, set-up and configure them. When things break because of exploding demand, you have to re-iterate etc.
• The combinatorial explosion for students that have to deal with all the different preferred tools is significant.

Understand Your Objectives and Teaching Methodology

When presence-based teaching is suspended, many people would probably think: “OK, I have to do Zoom lectures now”.

First of all, translating all presence-based activities directly to online lectures will most likely be extremely stressful for both you and your students. You would not imagine the fatigue that sets in after a full day of different online courses. So, it’s not unreasonable to scale down both the density of individual lectures as well as their cadence.

Moreover, not everything has to be done in synchronous online meetings. Luckily, there are many ways to share knowledge, engage in discussions that are used productively in non-covid-19 times such as shared editing, Wiki, forums (see above).

Finding a good balance between synchronous and asynchronous teaching/collaboration can also really transform your courses from traditional teaching & examination to something more interesting.

Also, reach out to the didactics experts in your organization (or elsewhere). They may actually have good tips for unconventional methods that were never quite practical but might just be useful now.

In that context, most people would probably agree that good education (“Bildung” in german) is more than programming skills into brains, so the crisis could be a good opportunity to double down on (r)evolving education to the Humboldtian model of higher education.

Specifically, I am referring to promoting self-determination and responsibility, encouraging self-motivated learning, and combining research and teaching.

So when thinking about methodology and tools, do not only think about the tools that you use — also think about what you offer to enable students study, discuss, research without you. Luckily, most students don’t need to be taught with respect to good online collaboration tools, but it may still be useful to provide a space on a reliable platform, at least for kickstarting things.

With respect to tools, personally, I have converged to:

• asynchronous collaboration tools (forum, Wiki, tests) in Moodle;
• file sharing, collaborative software development with gitlab;
• online teaching with BigBlueButton (see below);
• online discussion (smaller groups, chat rooms for students) with Jitsi Meet (see below);

I have been using many of those before anyway, so no big change.

As a meta-remark, I would also recommend to manage everyone’s expectations (especially your own ones): crisis means change for everyone, lots of improvisation, hopefully lots of volunteer efforts. There is really no need to expects (and demand) perfection. While it’s good to carry on and make sure students get their education and degrees, nobody will be angry if there is slow-start, some slack in-between and some prioritization of fewer topics — maybe quite the opposite.

Online Teaching and Tools

Having sorted out asynchronous vs. synchronous collaboration above, there is still a lot to be said about online teaching tools. Again, it’s quite important to understand your objectives — and what the individual tools are actually intended for. Also, when deciding on a particular tools or platform, it does not hurt to understand some technical basics, such as how Internet multimedia works, what scalability means, how infrastructure constraints may affect your experience etc.

It’s very natural: when we have worked with some online communication/collaboration tool, and it worked OK-ish, we tend to use it again, sometimes also for unintended purposes. However, it’s important to understand two things:

1. Online teaching can mean different things (making video available vs. interactive online classrooms), and although you can stretch things sometimes, there is not one tool that fits all purposes.
2. Just the fact that a tools worked once for you, and the user experience was not completely horrible, does not imply that it will work well in your lecture.

Different Forms of Online Teaching

This might be self-explanatory to most, but let me just quickly explain the basics:

• Lecture Streaming/Broadcasting (on YouTube, Twitch and similar platforms) is great for distributing recorded or live content to audiences. Although there are chat-based feedback mechanisms, it’s not the same as virtual classrooms with interactive discussion, collaborative editing etc. Don’t get me wrong, I have used YouTube for live lectures myself and it’s OK if you can accept the constraints. I would use it for public, pre-recorded content mostly.
• General-purpose online multimedia communication (with Skype, Jitsi Meet, Google Hangouts, WebEx, Zoom etc.) is great to discuss in your team, family etc., and sometimes they can also scale to larger conference calls, but they are not primarily intended for online teaching. For example, these tools would often lack collaborative editing, integrated document sharing, integration with learning management and e-learning systems etc. Of courses, some of them are also quite feature-rich and certainly usable (I have done lectures with tools like that without problems), but it’s better to treat them as a fallback — for example in crisis times, when you need a fast solution.
• Online Teaching tools (for example BigBlueButton) are specialized multimedia conferencing tools that provide extra functionality to ensure a good teaching and learning experience. For example, they make sure that presentation material sharing works really well (and is not just window sharing in a video stream), they use reasonable resolution and bandwidth settings that balance quality and resource efficiency, somebody has thought about UX design for teachers’ view, they make it easy to share session recordings, and they integrate with your LMS.

The point here is not that one of these is better than the others — these are really just different categories for different purposes. If you can, pick the right one for your needs.

Technical Constraints

Believe it or not, thanks to relentless research and engineering efforts by the networking community, namely the IETF and IRTF, (interactive) multimedia real-time communication is technically a solved problem. Still, sometimes things get screwed up badly — why?

With most hosted online communication tools, there is really no point in extrapolating one’s one-time experience to general applicability in a class room scenario. Even if tool A worked well in your class today, it does not have to mean it will well for your colleague tomorrow. There are different factors that affect, for example scalability and usability, especially in crisis times.

For example, when talking about scalability, there are two dimensions:

1. How many participants can you have in one session? Obviously, this also depends on what you do, e.g., is there one video sender or 100? But independent of that, some tools may have design characteristics (video formats and encoding options, protocols, scalability of the server software) that make them support larger crowds better or worse than others.
2. How many conferences can you have the at the time? Assuming you are a university, this would be an interesting question. For hosted systems, this fundamentally depends on the available (or allocated) resources, i.e., servers at your provider.

In other words, there can be systems that are great, a pleasure to use from a software design perspective, but in order to make a credible statement on applicability to your online teaching, you need to consider:

• Who is hosting the system?
• How does performance isolation work?
• How oversubscribed is the service (now and at peak times)?
• What is the latency between you (your participants) and the server(s), i.e., where are they hosted?

Some conference systems work with static resource allocation, for example one virtual machine per personalized conference server. This can work well, depending on how many VMs are allocated to one physical server. Others may use modern cloud-native auto-scaling. In general, great — but it still depends on how generous you are with respect to resource allocation.

The point I am trying to make is that it is often not very helpful to recommend your popular tool if you cannot say anything about the deployment parameters and the particular scaling approach.

Third-party Hosting vs. Self-Hosting

With all these uncertainties with externally hosted services one might ask: isn’t it better to run a self-hosted conferencing server (farm), for example a licensed commercial system or an Open-Source system?

Well, this depends a lot on your infrastructure: Assuming you are using interactive online teaching with at least one video stream at a time, with todays technology you would need about 1 MBit/s per participant, i.e., 100 MBit/s for a class of hundred (on average — can easily be double or more, depending on video quality). A university has many simultaneous lectures, so you might be reaching 1GBits/s with 10 simultaneous lectures already. That’s not necessarily too much — it depends on your institutions internal network and access to the Internet.

Video servers are also relatively resource-hungry. Nothing that cannot be handled by a few powerful servers, but you would have to set them up with a load balancer, maintain them etc.

This can all be done, and your typical sysadmins should be able to do that — but it’s probably not the right choice when your provost tells you that everybody has to switch to online teaching tomorrow.

My Recommendations

I am using a mix of asynchronous and different synchronous collaboration tools, i.e., as mentioned above:

• Moodle-based management and collaboration (mailing lists, basic Wiki, forum, tests etc.)
• gitlab (git repository plus Wiki mostly)
• Self-hosted Jitsi Meet for online meetings
• University-hosted BigBlueButton for online teaching

In the spirit of full transparency, I am also using WebEx as a fallback (kindly sponsored by Cisco) just to have some redundancy.

I am considering to use some form of instant messaging system (probably Jabber) to create a more inclusive, connected community for courses, but have not found the time yet to set this up. I used Slack before for university projects, but I don’t want to make it a rule for all courses.

Jitsi Meet

Jitsi Meet is an Open Source video conferencing tool that you can use using Jitsi’s server or host on your own infrastructure. It’s using WebRTC (i.e., media streaming in your browser). Communication between your browser and the server is encrypted. The server is not mixing video (like on some systems) but is using selective forwarding (i.e., switching the main video stream depending on configuration and on who is currently talking).

It’s a great tool that is sometimes underestimated because you don’t see the different options when you just use the public service. For example Jitsi can do recording, youTube live streaming, collaborative editing (through Etherpad). There are also ways to run it with load-balancers for better scalability and availability, and you can even network the video bridges for better experience in global, large-scale conferences.

There is still work to do with respect to video codecs (at least the transmission rates can be quite high sometimes), the way that recording and streaming is implemented (through a pseudo client that grabs video from a Chrome client) and usability of the server software (nothing crazy).

My recommendations for running your own Jitsi Meet server:

• Use the docker installation option that runs the different server components in docker components and makes the initial setup really easy (including automatic Let’s Encrypt certificate installation);
• Encourage your users to use the desktop client application (instead of running it in a browser). The desktop client contains the same WebRTC code in a package. It works a bit better (performance- and reliability-wise) compared to using your average Chrome or Firefox — I suspect because of potential feature interaction with Addons (and I use quite many).
• Use the options for muting participants on joining and enforce certain rules for larger meetings (i.e., mute everybody except the main presenter, turn off video unless needed etc.)
• Jitsi will happily use the best video quality that your camera can produce. Often, that is not needed — you can configure lesser quality (which can reduce server/network load significantly).
• The bottleneck in a Jitsi-Server is typically the network interface, so try to run in on server with a 10Gbit/s-interface for better results.

In my group, we set up our own server in the week before presence-based teaching got suspended, and it has proven to be super-valuable, especially when many of the centralized server-based systems failed on day one. Some of my colleagues are using it regularly for their courses.

BigBlueButton

BigBlueButton is a web conferencing system designed for online teaching and learning:

• You can maintain several rooms (say one per class, each of which with its own configuration, recordings etc.). Every room has a unique URI — that’s all students have to know.
• the UI is designed to enable tracking video, shared material, participants roster, chat windows;
• presenting slides etc. is not done via screen/application sharing but though a dedicated distribution channel: you can upload PDFs and other formats to the server that then distributed this to the clients — works much better than screen sharing in a video stream;
• live multi-user whiteboards;
• user polling;
• recordings and replay on the platform; and
• learning management system integration.

I am really convinced by the overall look and feel of the system and its performance and scalability. So far, I have used in lectures with up to 60 participants (on a spare, not high-end server) without any problems. The resource requirements seem comparatively lower compared to Jitsi Meet, probably also because of a more careful configuration of default video sending rates.

From a security perspective, BigBlueButton uses encryption for all communication between your browser and the server (but the server still needs to have access, like the Jitsi Meet server).

My recommendation for running your own BigBlueButton server:

• The client software runs well in a number of browser (tested Safari, Chrome, Firefox) so far. If you want to use WebRTC desktop/application window sharing, make sure you use it with Firefox or Chrome.
• For university-scale deployments there is a load balancer for BigBlueButton that would allow to add more servers as you grow.

In summary, I am convinced that BigBlueButton addresses most if not all online teaching requirements. If you find a way to run or it (or have it hosted), you should use it.

Recording

Many of us had experimented with recording lectures before (for example, for flipped classroom setups). Now, with the general shift to online lectures, recording essentially becomes a “by-product”, i.e., you can just turn it on (if your system supports it).

In the current crisis period, recording is actually not only nice-to-have — I would even say that it’s a crucial feature:

• Having the possibility to provide access to recorded lectures can remove a lot of pressure in times of distress. There is a lot to process for each of us and just knowing that there will be recordings creates additional assurance.
• Online teaching sessions are peak-utilization periods. Having videos for asynchronous consumption can help distributing the load because not everybody has to join the simultaneous live streaming.
• Depending on the region your students live in, access networks may not be perfect, especially not if you have to share a low-bandwidth link with another student who is supposed to follow online lectures.
• In times of lock-downs and travel restrictions, some of your students may actually be out of the country without a chance to return any time soon. They may not even be in the same timezone…
• Although you would expect that everyone is currently practicing home-sheltering and should have lots of time on their hands, don’t forget that crisis times can actually mean real crisis for
  individual people: they may have to take care of family members or
  themselves, queue at supermarkets, doctors’ offices etc. — so just because you are sitting at in your home office, does not have to imply that everybody is.

In summary, consider recording everything (with participant consent) and make it available whenever possible.

To Zoom or not to Zoom?

Zoom has been getting a lot of bad press recently and I’m getting many questions from colleagues and friends about it.

First of all, Zoom is a modern video conferencing service with excellent scaling properties, so performance is typically good, and it’s also very easy to use.

Should you use it?

No

While some of the recent online articles are hyperbole and based on an incorrect understanding of how these systems typically work, there are, in my opinion, some strong arguments to stay away from Zoom:

• Zoom is presenting itself as a (paid) conferencing service. However it has turned out that they also work with quite a few infamous tracking systems, i.e., they share data about you (and everyone who is using it) with the online tracking industry. Many websites do that because it’s their main business model, and many users haven’t been aware before GDPR at least forced them obtain your consent. It’s not obvious why a commercial conferencing service has to do that, though.
• For some websites and services, we have gotten used to ubiquitous tracking and we may either accept or not, or find ways to contain it (difficult). Personally, we may even be OK with tracking. However, it’s a different thing for online teaching where you have a captive audience. By using a tracking-encumbered system in your lecture, you are essentially forcing your students to use it, too — and to become a subject of tracking and surveillance themselves.
• The Zoom client runs in a web browser (where expert users may be able to contain the tracking to some extent), however Zoom is trying to force users to install the standalone application.
• Unfortunately, Zoom has demonstrated time-over-time that they do not understand basic system security, for example: webcam hack, malware installation trick on MacOS, use of single AES-128 key in ECB mode.

Bruce Schneier has summarized the most critical issues. Zoom is apparently another company that adopted the “grow fast, apologize later” approach and is now trying surf on the covid-19 wave to accelerate their growth at whatever cost.

These models used to be standard in the web and advertisement industry. Time is changing though, and as more people understand the problems of intransparent, uncontrolled surveillance, aggregation and unlimited storage, these business ethics will become increasingly unacceptable. In a few years we will look at it bewildered — like we look at Weinstein-type misogyny in #MeToo times.

I am hoping that Zoom as a company gets the message, but I am not confident to be honest.

Luckily, for online teaching, we don’t have to care because there are better alternatives anyway.

So, make wise choices.

Updates

• 2020-04-04: Fixed formatting and other nits; added Zoom AES-128-ECB vulnerability and links to Citizen Lab’s and Bruce Schneier’s blog postings about it.

I had the pleasure of being invited for a keynote at IEEE HotICN-2019 in Chongqing. I talked about key ICN properties (from my perspective), about general research areas, and three specific topics: Quality of Service, Forwarding Plane Interaction with the Routing System and Applications, and In-Network Computing.

QUIC is the next transport protocol for the Internet that is currently being standardized by the IETF. My student Thomas Ripping at University of Applied Sciences Emden/Leer has developed cwik, an open, interactive and extensible Clojure framework for automating QUIC interop tests and performance measurements, based on Peter Doornbosch’s Kwik library. It can be used for defining test campaigns programmatically and can enable reproducible experiments and automatic evaluation. The source code is available on github.com.

Edge- and, more generally, in-network computing is receiving a lot attention in research and industry fora. The ability to decentralize computing, to achieve low latency communication to distributed application logic, and the potential for privacy-preserving analytics are just a few examples that motivate a new approach for looking at computing and networking.

What are the interesting research questions from a networking and distributed computing perspective? In-network computing can be conceived in many different ways – from active networking, data plane programmability, running virtualized functions, service chaining, to distributed computing. What abstractions do we need to program, optimize, and to manage such systems? What is the relationship to cloud networking?

These questions will be discussed at the first workshop on Emerging In-Network Computing (ENCP) that takes place at ACM CoNEXT-2019 on December 9th in Orlando.

We have received many interesting submission and were able to put together a really interesting program that covers both Network Programmability and In-Network Computing Architectures and Protocols. Check out the full program here.

Many thanks to my co-organizers Spyros Mastorakis and Abderrahmen Mtibaa, to our steering committee members Jon Crowcroft, Satyajayant (Jay) Misra, and Dave Oran, and to our great Technical Program Committee for putting this together.

Links

• 1st ACM CoNEXT ENCP-2019 workshop
• Compute First Networking (CFN): Distributed Computing meets ICN
• Proposed IRTF Research Group on Computing in the Networking (COINRG)

ACM ICN-2019 took place in the week of September 23 in Macau, SAR China. The conference was co-located with Information-Centric-Networking-related side events: the TouchNDN Workshop on Creating Distributed Media Experiences with TouchDesigner and NDN before and an IRTF ICNRG meeting after the conference. In the following, I am providing a summary of some highlights of the whole week from my (naturally very subjective) perspective.

Applications

ICN with its accessing named data in the network paradigm is supposed provide a different, hopefully better, service to application compared to the traditional stack of TCP/IP, DNS and application-layer protocols. Research in this space is often addressing one of two interesting research questions: 1) What is the potential for building or re-factoring applications that use ICN and what is the impact on existing designs; and 2) what requirements can be learned for the evolution of ICN, what services are useful on top of an ICN network layer, and/or how should the ICN network layer be improved.

Network Management

The best paper at the conference on Lessons Learned Building a Secure Network Measurement Framework using Basic NDN by Kathleen Nichols took the approach of investigating how a network measurement system can be implemented without inventing new features for the NDN network layer. Instead, Kathleen’s work explored the features and usability support mechanisms that would be needed for implementing her Distributed Network Measurement Protocol (DNMP) in terms of frameworks and libraries leveraging existing NDN. DNMP is secure, role-based framework for requesting, carrying out, and collecting measurements in NDN forwarders. As such it represents a class of applications where applications both send and receive data that is organized by hierarchical topics in a namespace which implies a conceptual approach where applications do not (want to) talk to specific producers but are really operating in an information-centric style.

Communication in such a system involves one-to-many, many-to-one, and any-to-any communications about information (not data objects hosted at named nodes). DNMP employs a publish/subscribe model inspired by protocols such as MQTT where publishers and subscribers communicate through hierarchically structured topics. Instead of existing frameworks for data set reconciliation, with DNMP work includes the development of a lightweight pub/sub sync protocol called syncps that uses Difference Digests, solving the multi-party set reconciliation problem with prior context.

In a role-based system such as DNMP that uses secure Named-Data-based communication, automating authentication and access control is typically a major challenge. DNMP leverages earlier work on Trust Schema but extends this by a Versatile Security Toolkit (VerSec) that integrates with the transport framework to simplify integration of trust rules. VerSec is about to be released under GPL.

I found this paper really interesting to read because it is a nice illustration of what kind of higher layer services and APIs non-trivial application require. Also, the approach of using the NDN network layer as is but implementing additional functionality as libraries and frameworks seems promising with respect to establishing a stable network layer platform where innovation can happen independently on top. Moreover, the paper embraces Information-Centric thinking nicely and demonstrates the concept with a relevant application. Finally, I am looking forward to see the VerSec software which could make it easier for developers to implement rigorous security and validation in the applications.

Distributed Media Experiences

Jeff Burke and Peter Gusev organized the very cool TouchNDN workshop on Creating Distributed Media Experiences with TouchDesigner and NDN at the School of Creative Media at the City University of Hong Kong (summary presentation). The background is that video distribution/access has evolved significantly from linear TV broadcast to todays applications. Yet, many systems still seem to be built in a way that optimizes for linear video streaming to consumer eye balls, with a frame sequence abstraction.

Creative media applications such as Live Show Control (example) exhibit a much richer interaction with digital video, often combing 3D modelling with flexible, non-sequential access to video based on (for example) semantics, specific time intervals, quality layers, or spatial coordinates.

Combine this with dynamic lightning, sound control and instrumentation of theater effects, and you get an idea of an environment where various pieces of digital media are mixed together creatively and spontaneously. Incidentally, a famous venue for such an installation is the Spectacle at MGM Cotai, close to the venue of ACM ICN-2019 in Macau.

Derivative’s TouchDesigner is a development platform for such realtime user experiences. It is frequently used for projection mapping, interactive visualization and other applications. The Center for Research in Engineering, Media and Performance (REMAP) has developed an integration of NDN with TouchDesigner’s realtime 3D engine via the NDN-Common-Name-Library stack as a platform for experimenting with data-centric media. The objective is to provide a more natural networked media platform that does not have to deal with addresses (L2 or L3) but enables applications to publish and request media assets in namespaces that reflect the structure of the data. Combing this with other general ICN properties such as implicit multicast distribution and in-network caching results in a much more adequate platform for creating realtime multimedia experiences.

The TouchNDN workshop was one of REMAP’s activities on converging their NDN research with artistic and cultural projects, trying to get NDN out of the lab and into the hands of creators in arts, culture, and entertainment. It is also an eye-opener for the ICN community for learning about trends and opportunities in real-time rendering and visual programming which seems to bear lots of potential for innovation — both from the artistic as well as from the networking perspective.

Personally, I think it’s a great, inspiring project that teaches us a lot about more interesting properties and metrics (flexible access, natural APIs, usability, utility for enabling innovations) compared to the usual quantitative performance metrics from the last century.

Inter-Server Game State Synchronization

Massive Multiplayer Online Role-Playing Games (MMORPGs) allow up to thousands of players to play in the same shared virtual world. Those worlds are often distributed on multiple servers of a server cluster, because a single server would not be able to handle the computational load caused by the large number of players interacting in a huge virtual world. This distribution of the world on a server cluster requires to synchronize relevant game state information among the servers. The synchronization requires every server to send updated game state information to the other servers in the cluster, resulting in redundantly sent traffic when utilizing current IP infrastructure.

In their paper Inter-Server Game State Synchronization using Named Data Networking Philipp Moll, Sebastian Theuermann, Natascha Rauscher, Hermann Hellwagner, and Jeff Burke started from the assumption that ICN’s implicit multicast support and the ability to to decouple the game state information from the producing server could reduce the amount of redundant traffic and also help with robustness and availability in the presence of server failures.

They built a ICNified version of Minecraft and developed protocols for synchronizing game state in a server cluster over NDN. Their evaluation results indicated the benefits on an ICN-based approach for inter-server game state synchronization despite larger packet overheads (compared to TCP/IP). The authors made all their artefacts required for reproducing the results available on github.

Panel on Industry Applications of ICN

I had the pleasure of moderating a panel on industry applications of ICN, featuring Richard Chow (Intel), Kathleen Nichols (Pollere Inc.), and Kent Wu (Hong Kong Applied Science and Technology Research Institute). Recent ICN research has produced various platforms for experimentation and application development. One welcome development consists of initial ICN deployment mechanisms that do not require a forklift replacement of large parts of the Internet. At the same time, new technologies and use cases, such as edge computing, massively scalable multiparty communication, and linear video distribution, impose challenges on the existing infrastructure. This panel with experts from different application domains discussed pain points with current systems, opportunities and promising results for building specific applications with ICN, and challenges, shortcomings, and ideas for future evolution of ICN.

What was interesting to learn was how different groups pick up the results and available software to build prototypes for research and industry applications and what they perceive as challenges in applying ICN.

Decentralization

Growing concerns about centralization, surveillance and loss of digital sovereignty are currently fuelling many activities around P2P-inspired communication and storage networks, decentralized web (“web3”) efforts as well as group such as the IRTF Research Group on Decentralized Internet Infrastructure (DINRG). One particular concern is the almost universal dependency on central cloud platforms for anchoring trust in applications that are actually of a rather local nature such as smart home platforms. Since such platforms often entail rent-seeking or surveillance-based business models, it is becoming increasingly important to investigate alternatives.

NDN/CCN-based ICN with its built-in PKI system provides some elements for an alternative design. In NDN/CCN it is possible to set up secure communication relationships without necessarily depending on third-party platforms which could be leveraged for more decentralized designs of IoT systems, social media and many other applications.

Decentralized and Secure Multimedia Sharing

A particularly important application domain is multimedia sharing where surveillance and manipulation campaigns by the dominant platforms have led to the development of alternative federated social media applications such as Mastodon and Diaspora. In their paper Decentralized and Secure Multimedia Sharing Application over Named Data Networking Ashlesh Gawande, Jeremy Clark, Damian Coomes, and Lan Wang described their design and implementation of npChat (NDN Photo Chat), a multimedia sharing application that provides similar functionality as today’s media-sharing based social networking applications without requiring any centralized service providers.

The major contributions of this work include identifying the specific requirements for a fully decentralized application, and designing and implementing NDN-based mechanisms to enable users to discover other users in the local network and through mutual friends, build friendship via multi-modal trust establishment mirrored from the real world, subscribe to friends’ multimedia data updates via pub-sub, and control access to their own published media.

This paper is interesting in my view because it illustrates the challenges and some design options nicely. It also suggests further research in terms of namespace design, name privacy and trust models. The authors developed an NDN-based prototype for Android systems that is supposed to appear on the Android Play store soon.

Exploring the Relationship of ICN and IPFS

We were happy to have David Dias, Adin Schmahmann, Cole Brown, and Evan Miyazono from Protocol Labs at the conference who held a tutorial on IPFS that also touched upon the relationship of IPFS and some ICN approaches.

Protocol Lab’s InterPlanetary File System (IPFS) is a peer-to-peer content-addressable distributed filesystem that seeks to connect all computing devices with the same system of files. It is an opensource community-driven project, with reference implementations in Go and Javascript, and a global community of millions of users. IPFS resembles past and present efforts to build and deploy Information-Centric Networking approaches to content storage, resolution, distribution and delivery. IPFS and libp2p, which is the modular network stack of IPFS, are based on name-resolution based routing. The resolution system is based on Kademlia DHT and content is addressed by flat hash-based names. IPFS sees significant real-world usage already and is projected to become one of the main decentralised storage platforms in the near future. The objective of this tutorial is to make the audience familiar with IPFS and able to use the tools provided by the project for research and development.

Interestingly IPFS bear quite some similarities with earlier ICN systems such as NetInf but is using traditional transport and application layer protocols for the actual data transfer. One of the interesting research questions in that space are how IPFS system could be improved with today’s ICN technology (as an underlay) but also how the design of a future IPFS-like system could leverage additional ICN mechanisms such as Trust Schema, data set reconciliation protocols, and remote method invocation. The paper Towards Peer-to-Peer Content Retrieval Markets: Enhancing IPFS with ICN by Onur Ascigil, Sergi Reñé, Michał Król et al. explored some of these options.

IoT

IoT is one of the interesting application areas for ICN, especially IoT in constrained environments, where the more powerful forwarding model (stateful forwarding and in-network caching) and the associated possibility for more fine-grained control of storage and communication resources incurs significant optimization potential (which was also a topic at this year’s conference).

QoS Management in Constrained NDN Networks

Quality of Service (QoS) in the IP world mainly manages forwarding resources, i.e., link capacities and buffer spaces. In addition, Information Centric Networking (ICN) offers resource dimensions such as in-network caches and forwarding state. In constrained wireless networks, these resources are scarce with a potentially high impact due to lossy radio transmission. In their paper Gain More for Less: The Surprising Benefits of QoS Management in Constrained NDN Networks Cenk Gündoğan, Jakob Pfender, Michael Frey, Thomas C. Schmidt, Felix Shzu-Juraschek, and Matthias Wählisch explored the two basic service qualities (i) prompt and (ii) reliable traffic forwarding for the case of NDN. The resources that were taken into account are forwarding and queuing priorities, as well as the utilization of caches and of forwarding state space. The authors treated QoS resources not only in isolation, but also correlated their use on local nodes and between network members. Network-wide coordination is based on simple, predefined QoS code points. The results indicate that coordinated QoS management in ICN is more than the sum of its parts and exceeds the impact QoS can have in the IP world.

What I found interesting about his paper is the validation in real-world experiments that demonstrated impressive improvements, based on the coordinated QoS management approach. This work comes timely considering the current ICN QoS discussion in ICNRG, for example in draft-oran-icnrg-qosarch. Also, the authors made their artefacts available on github for enabling reproducing their results.

How Much ICN Is Inside of Bluetooth Mesh?

Bluetooth mesh is a new mode of Bluetooth operation for low-energy devices that offers group-based publish-subscribe as a network service with additional caching capabilities. These features resemble concepts of information-centric networking (ICN), and the analogy to ICN has been repeatedly drawn in the Bluetooth community. In their paper Bluetooth Mesh under the Microscope: How much ICN is Inside? Hauke Petersen, Peter Kietzmann, Cenk Gündoğan, Thomas C. Schmidt, and Matthias Wählisch compared Bluetooth mesh with ICN both conceptually and in real-world experiments. They contrasted both architectures and their design decisions in detail. They conducted experiments on an IoT testbed using NDN/CCNx and Bluetooth Mesh on constrained RIOT nodes.

Interestingly the authors found that the implementation of ICN principles and mechanisms in Bluetooth Mesh is rather limited. In fact, Bluetooth Mesh performs flooding without content caching and merely using the equivalent of multicast addresses as a surrogate for names. Based on these findings, the authors discuss options of how ICN support for Bluetooth could or should look like, so the paper is interesting both for understanding the actual working of Bluetooth Mesh as well as for ideas for improving Bluetooth Mesh. The authors made their artefacts available on github for enabling reproducing their results.

ICN and LoRa

LoRa is an interesting technology for its usage of license-free sub-gigahertz spectrum and bi-directional communication capabilities. We were happy to have Kent Wu and Xiaoyu Zhao from ASTRI at the conference and the ICNRG meeting who talked about their LoRa prototype development for a smart metering system for water consumption in Hong Kong. In addition to that, the ICNRG also discussed different options for integrating ICN and LoRa and got an update by Peter Kietzmann on the state of LoRa support in the RIOT OS. This is an exciting area for innovation, and we expect more work and interesting results in the future.

New Frontiers

Appying ICN to big data storage and processing and to distributed computing are really promising research directions that were explored by papers at the conference.

NDN and Hadoop

The Hadoop Distributed File System (HDFS) is a network file system used to support multiple widely-used big data frameworks that can scale to run on large clusters. In their paper On the Power of In-Network Caching in the Hadoop Distributed File System Eric Newberry and Beichuan Zhang evaluate the effectiveness of using in-network caching on switches in HDFS- supported clusters in order to reduce per-link bandwidth usage in the network.

They discovered that some applications featured large amounts of data requested by multiple clients and that, by caching read data in the network, the average per-link bandwidth usage of read operations in these applications could be reduced by more than half. They also found that the choice of cache replacement policy could have a significant impact on caching effectiveness in this environment, with LIRS and ARC generally performing the best for larger and smaller cache sizes, respectively. The authors also developed a mechanism to reduce the total per-link bandwidth usage of HDFS write operations by replacing write pipelining with multicast.

Overall, the evaluation results are promising, and it will be interesting to see how the adoption of additional ICN concepts and mechanisms and caching could be useful for big data storage and processing.

Compute-First Networking

Although, as a co-author, I am clearly biased, I am quite convinced of the potential for distributed computing and ICN that we described in a paper co-authored by Michał Król, Spyridon Mastorakis, David Oran, and myself.

Edge- and, more generally, in-network computing is receiving a lot attention in research and industry fora. What are the interesting research questions from a networking perspective? In-network computing can be conceived in many different ways – from active networking, data plane programmability, running virtualized functions, service chaining, to distributed computing. Modern distributed computing frameworks and domain-specific languages provide a convenient and robust way to structure large distributed applications and deploy them on either data center or edge computing environments. The current systems suffer however from the need for a complex underlay of services to allow them to run effectively on existing Internet protocols. These services include centralized schedulers, DNS-based name translation, stateful load balancers, and heavy-weight transport protocols.

Over the past years, we have been working on alternative approaches, trying to find ways for integrating networking and computing in new ways, so that distributed computing can leverage networking capabilities directly and optimize usage of networking and computing resources in a holistic fashion. Here is a summary of our latest paper.

Edge- and, more generally, in-network computing is receiving a lot attention in research and industry fora. What are the interesting research questions from a networking perspective? In-network computing can be conceived in many different ways – from active networking, data plane programmability, running virtualized functions, service chaining, to distributed computing. Modern distributed computing frameworks and domain-specific languages provide a convenient and robust way to structure large distributed applications and deploy them on either data center or edge computing environments. The current systems suffer however from the need for a complex underlay of services to allow them to run effectively on existing Internet protocols. These services include centralized schedulers, DNS-based name translation, stateful load balancers, and heavy-weight transport protocols.

Over the past years, we have been working on alternative approaches, trying to find ways for integrating networking and computing in new ways, so that distributed computing can leverage networking capabilities directly and optimize usage of networking and computing resources in a holistic fashion.

From Application-Layer Overlays to In-Network Computing

Domain-specific distributed computing languages like LASP have gained popularity for their ability to simply express complex distributed applications like replicated key-value stores and consensus algorithms. Associated with these languages are execution frameworks like Sapphire and Ray that deal with implementation and deployment issues such as execution scheduling, layering on the network protocol stack, and auto-scaling to match changing workloads. These systems, while elegant and generally exhibiting high performance, are hampered by the daunting complexity hidden in the underlay of services that allow them to run effectively on existing Internet protocols. These services include centralized schedulers, DNS-based name translation, stateful load balancers, and heavy-weight transport protocols.

We claim that, especially for compute functions in the network, it is beneficial to design distributed computing systems in a way that allows for a joint optimization of computing and networking resources by aiming for a tighter integration of computing and networking. For example, leveraging knowledge about data location, available network paths and dynamic network performance can improve system performance and resilience significantly, especially in the presence of dynamic, unpredictable workload changes.

The above goals, we believe, can be met through an alternative approach to network and transport protocols: adopting Information-Centric Networking as the paradigm. ICN, conceived as a networking architecture based on the principle of accessing named data, and specific systems such as NDN and CCNx have accommodated distributed computation through the addition of support for remote function invocation, for example in Named Function Networking, NFN and RICE, Remote Method Invocation in ICN and distributed data set synchronization schemes such as PSync.

Introducing Compute First Networking (CFN)

We propose CFN, a distributed computing environment that provides a general-purpose programming platform with support for both stateless functions and stateful actors. CFN can lay out compute graphs over the available computing platforms in a network to perform flexible load management and performance optimizations, taking into account function/actor location and data location, as well as platform load and network performance.

We have published a paper about CFN at the ACM ICN-2019 Conference that is being presented in Macau today by Michał Król. The paper makes the following contributions:

1. CFN marries a state-of-the art distributed computing framework to an ICN underlay through RICE, Remote Method Invocation in ICN. This allows the framework to exploit important properties of ICN such as name-based routing and immutable objects with strong security properties.
2. We adopted the rigorous computation graph approach to representing distributed computations, which allows all inputs, state, and outputs (including intermediate results) to be directly visible as named objects. This enables flexible and fine-grained scheduling of computations, caching of results, and tracking state evolution of the computation for logging and debugging.
3. CFN maintains the computation graph using Conflict-free Replicated Data Types (CRDTs) and realizes them as named ICN objects. This enables implementation of an efficient and failure-resilient fully- distributed scheduler.
4. Through evaluations using ndnSIM simulations, we demonstrate that CFN is applicable to range of different distributed computing scenarios and network topologies.

Resources and Links

• My keynote at IEEE CCNC-2019 on Compute-First Networking (CFN): New Perspectives on Integrating Computing and Networking
• Internet Draft draft-kutscher-coinrg-dir-00 with Jörg Ott and Teemu Kaerkkaeinen on Directions for Computing in the Network (COIN) and the corresponding presentation.
• The CFN paper at ACM ICN-2019: Compute First Networking: Distributed Computing meets ICN. The author team: Michał Król, Spyridon Mastorakis, David Oran, Dirk Kutscher
• CFN builds on our earlier work on RICE, Remote Method Invocation in ICN, authored by: Michał Król, Karim Habak, Karim Habak, Dirk Kutscher, Ioannis Psaras
• 1st ACM CoNEXT Workshop on Emerging in-Network Computing Paradigms (ENCP)
• IRTF Computing in the Network Proposed Research Group (COIRG)

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