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How does Ouroboros relate to RINA, the Recursive InterNetwork Architecture?

A brief history of Ouroboros
There are two kinds of researchers: those that have implemented
something and those that have not. The latter will tell you that there
are 142 ways of doing things and that there isn't consensus on which
is best.The former will simply tell you that 141 of them don't work.
  -- David Cheriton

When I talk to someone that’s interested in Ouroboros, a question that frequently pops up is how the project relates to the Recursive InterNet(work) Architecture, or RINA. I usually steer away from going into the technical aspects of how the architectures differ, mostly because not many people know the details of how RINA works. But the origin of Ouroboros definitely lies with our research and our experiences implementing RINA, so it’s a good question. I’ll address it as best as I can, without going overboard on a technical level. I will assume the reader is at least somewhat familiar with RINA. Also keep in mind that both projects are ongoing and should not be considered as “done”; things may change in the future. These are my – inevitably subjective and undoubtedly somewhat inaccurate – recollections of how it went down, why Ouroboros exists, and how it’s different from RINA.

And a quick note here: Ouroboros the network prototype has no relation to Ouroboros the Proof-of-Stake protocol in the Cardano blockchain. That some of the Cardano guys are also interested in RINA doesn’t help to ease any confusion.

IBBT meets RINA

I first came into contact with RINA somewhere in 2012, while working as a senior researcher in the field of telecommunication networks at what was then known as IBBT (I’ll save you the abbreviation). IBBT would soon be known as iMinds, and is now integrated into IMEC. A new research project was going to start and our research group was looking for someone to be responsible for the IBBT contributions. That project, called IRATI was a relatively short (2 years duration) project in the “Future Internet Research and Experimentation” (FIRE) area of the 7th framework programme of the European Commission. I won’t go into the details and strategies of research funding; the important thing to know is that the objectives of FIRE are “hands-on”, aimed at building and deploying Internet technologies. Given that I had some experience deploying experiments (at that time OpenFlow prototypes) on our lab testbeds, I listened to the project pitch, an online presentation with Q&A given by the project lead, Eduard Grasa from i2cat, who explained the concepts behind RINA, and got quite excited about how elegant this all looked. So I took on the project and read John Day’s Patterns in Network Architecture, which we later usually referred to as PNA. It was also the time when I was finishing my PhD thesis, so my PostDoc track was going to be for a substantial part on computer network architecture and RINA. Unifying Inter-Process Communication (IPC) and networking. How exciting was that!

IRATI – Investigating RINA as an Alternative to TCP/IP – was something different from the usual research projects, involving not only some substantially new and unfamiliar ideas, but it also relied very heavily on software development. Project work was performed as part of PhD tracks, so who would do the work? There was a PhD student under my guidance working mostly on OpenFlow, Sachin – one of the kindest people I have ever met, and now a professor at TU Dublin – and we had a student with us, Sander Vrijders, who just finished his master’s thesis. We invited him to talk about a possible PhD track, aligned to ongoing and upcoming projects in our group. Sander decided to take on the challenge of IRATI and start a PhD track on RINA.

IRATI

IRATI kicked off in January 2013 at i2cat in Barcelona. It was followed by a RINA workshop, bringing the project in touch with the RINA community, which had its epicenter at Boston University (BU). It’s where I first met John Day, who gave a 2-day in-depth tutorial of RINA. Eduard also presented an outline of the IRATI objectives. The project promised an implementation of RINA in Linux and FreeBSD/JunOS, with detailed comparisons of RINA against TCP/IP in various scenarios, and also demonstrate interoperability with other RINA prototypes: the TINOS prototype and the TRIA prototype. IRATI would also prepare the European FIRE testbeds for RINA experiments using the prototype. In 2 years, on 870k Euros in research funding. A common inside joke at project kick-off meetings in our field was to put a wager on the number slides that the presentation deck at the final project review meeting would differ from the slide decks presented at the initial kick-off meeting. IRATI was not going to be one of those projects!

With the RINA community gathered at the workshop, there were initial ideas for a follow-up research proposal to IRATI. Of course, almost every potential participant present was on board.

Three partners were responsible for the implementation: i2cat, who had experience on RINA; Nextworks a private-sector company with substantial experience on implementing networking solutions, and iMinds/imec, bringing in our testbed experience. Interoute (now part of GTT) validated the test scenarios that we would use for evalutions. Boston University had an advisory role in the project.

The first work was determining the software design of the implementation. IRATI was going to build an in-kernel implementation of RINA. A lot of the heavy lifting on the design was already done during the project proposal preparation phase, and about 3 months into the projects, the components to be implemented were well-defined. Broadly speaking, there were 3 things to implement: the IPCPs that make up the RINA layers (Distributed IPC Facilities, DIFs), the component that is responsible for creating and starting these IPCPs (the IPC manager), and the core library to communicate between these components, called librina. The prototype would be built in 3 phases over the course of 2 years.

i2cat was going to get started on most of the management parts (IPC Manager, based on their existing Java implementation; librina, including the Common Distributed Application Protocol (CDAP) and the DIF management functions in the normal IPCP) and the Data Transfer Protocol (DTP). iMinds was going to be responsible for the kernel modules that will allow the prototype to run on top of Ethernet. Nextworks was taking a crucial software-architectural role on kernel development and software integration. For most of these parts we had access to a rough draft of what they were supposed to do, John Day’s RINA reference model, which we usually referred to as the specs.

i2cat had a vested interest in RINA and was putting in a lot of development effort with 3 people working on the project: Eduard, Leonardo Bergesio and Miquel Tarzán. Nextworks assigned Francesco Salvestrini, an experienced kernel developer to the project. From iMinds, the development effort would come from Sander. My personal involvement in the project software development was limited, as I still had other ongoing projects (at least until the end of 2014) and my main role would be in the experimentation work, which was only planned start after the initial development phase.

The project established efficient lines of communications, mostly using Skype and the mailing lists and the implementation work got underway swiftly. I have been fortunate to be a part of a couple of projects where collaboration between partners was truly excellent, but the level of teamwork in IRATI was unprecedented. There was a genuine sense of excitement in everybody involved in the project.

So, Sander’s first task was to implement the shim DIF over Ethernet. This is a Linux loadable kernel module (LKM) that wraps the Ethernet 802.1Q VLAN with a thin software layer to present itself using the RINA API. The VLAN ID would be used as the layer name. No functionality would be added to the existing Ethernet protocol so with only the src and dst address fields left, this shim DIF was restricted to having only a single application registered at a time, and to a single RINA “flow” between the endpoints. We could deploy about 4000 of these shim DIFs in parallel to support larger RINA networks. The name resolution for endpoint applications was planned to be using the Address Resolution Protocol (ARP), which was readily available in the Linux kernel.

Or so we thought. The ARP implementation in the kernel assumed IPv4 as the only L3 protocol (IPv6 doesn’t use ARP), so it could not handle the resolution of RINA application names to MAC addresses, which we needed for the shim DIF. So after some deliberation, we decided to implement an RFC 826 compliant version of ARP to support the shim DIF.

In the meantime, we also submitted a small 3-partner project proposal the GEANT framework, tailored to researching RINA in an NREN (National Research and Education Networks) environment. The project was lead by us, partnering with i2cat, and teaming up with TSSG. IRINA would kick off in October 2013, meaning we’d have 2 parallel projects on RINA.

The project had made quite some progress in its first 6 months, there were initial implementations for most of the components, and in terms of core prototype functionality, IRATI was quickly overtaking the existing RINA prototypes. However, the pace of development in the kernel was slower than anticipated and some of the implementation objectives were readjusted (and FreeBSD/JunOS was dropped in favor of a shim DIF for Hypervisors). With the eye on testbed deployments, Sander started work on the design of a second shim DIF, one that would allow us to run the IRATI prototype over TCP/UDP.

In the meantime, the follow-up project that was coined during the first RINA workshop took shape and was submitted. Lead by our IRINA partner TSSG, it was envisioned to be a a relatively large project, about 3.3 million Euros in EC contributions, running for 30 months and bringing together 13 partners with the objective to build the IRATI prototype into what was essentially a carrier network demonstrator for RINA, adding policies for mobility, security and reliability. PRISTINE got funded. This was an enormous boon to the RINA community, but also a bit of a shock for us as IRATI developers, as the software was already a bit behind schedule with a third project on the horizon. The furthest we could push forward the start of PRISTINE was January 2014.

As the IRATI project was framed within FIRE, there was a strong implied commitment to get experimental results with the project prototype. By the last quarter of 2013, the experimentation work got started, and the prototype was getting its first deployment trials on the FIRE testbeds. This move to real hardware brought more problems to light. The network switches in the OFELIA testbed wasn’t agreeing very well with our RFC-compliant ARP implementation, dropping everything that hadn’t IPv4 as the network addresses. One of the testbeds also relied on VLANs to seperate experiments, which didn’t fare well with our idea to (ab)use them within an experiment for the shim DIF. While Sander did the development of the shim DIFs using the actual testbed hardware, other components had been developed predominantly in a virtual machine environment and had not been subjected to the massive parallellism that was available on dual-Xeon hardware. The stability of the implementation had to be substantially improved to get stable and reliable measurements. These initial trials in deploying IRATI also showed that configuring the prototype was very time consuming. The components used json configuration files which were to be created for each experiment deployment, causing substantial overhead.

The clock was ticking and while the IRATI development team was working tirelessly to stabilize the stack, I worked on some (kernel) patches and fixes for the testbeds so we could use VLANs (on a different Ethertype) in our experiment. We would get deployment and stability testing done and (internally) release prototype 1 before the end of the year.

PRISTINE

January 2014. The PRISTINE kick-off was organized together with a workshop, where John Day presented RINA, similar to the IRATI kick-off one year earlier, except this time it was in Dublin and the project was substantially bigger, especially in headcount. It brought together experts in various fields of networking with the intent of them applying that experience into developing polcies for RINA. But many of the participants to the PRISTINE project were very new to RINA, still getting to grips with some of the concepts (and John didn’t shy away from making that abundantly clear).

The first couple of months of PRISTINE was mostly about getting the participants up-to-speed with the RINA architecture and defining the use-case, which centered on a 5G scenario with highly mobile end-users and intelligent edge nodes. It was very elaborate, and the associated deliverables were absolute dreadnoughts.

During this PRISTINE ramp-up phase, development of the IRATI prototype was going on at a fierce pace. The second project brought in some extra developers to work on the IRATI core Bernat Gaston (i2cat), Vincenzo Maffione (Nextworks), and Douwe de Bock (a master student at iMinds). i2cat focusing on management and flow control and was also porting the Java user-space parts to C++, Vincenzo was focusing on the shim Hypervisor, which would allow communications between processes running over a VM host and guest, and we were building the shim layer to run RINA over TCP and UDP.

By this time, frustrations were starting to creep in. Despite all the effort in development, the prototype was not in a good shape. The development effort was also highly skewed, with i2cat putting in the bulk of the work. The research dynamic was also changing. At the start of IRATI, there was a lot of ongoing architectural discussions about what each component should do, to improve the specs, but due to the ever increasing time pressure, the teams were working more and more in isolation. Getting it done became a lot more important than getting it right.

All this development had led to very little dissemination output, which didn’t go unnoticed at project reviews. The upshot of the large time-overlap between the two projects was that, in combination with the IRATI design paper that got published early-on in the project, we could afford to lose out a bit on dissemination in IRATI and try to catch up in PRISTINE. But apart from the relatively low output in research papers, this project had no real contributions to standardization bodies.

In any case, the project had no choice but to push on with development, and, despite all difficulties, somewhere mid 2014 IRATI had most basic functionalities in place to bring the software in a limited way into PRISTINE so it could start development of the PRISTINE software developement kit (SDK) (which was developed by people also in IRATI).

Mostly to please the reviewers, we tried to get some standardization going, presenting RINA at an ISO SC6 JTC1 meeting in London and also at IETF91. Miquel and myself would continue to follow up on standardization in SC6 WG7 on “Future Network” as part of PRISTINE, gathering feedback on the specs and getting them on the track towards ISO RINA standards. I still have many fond memories of my experiences discussing RINA within WG7.

The IRATI project was officially ending soon, and the development was now focusing on the last functions of the Data Transfer Control Protocol (DTCP) component of EFCP, such as retransmission logic (delta-t). Other development was now shifted completely out of IRATI towards the PRISTINE SDK.

In the meantime, we also needed some experimental results. Experimentation with the prototype was a painful and very time-consuming undertaking. We finally squeezed a publication at Globecom 2014 out of some test results and could combine that with a RINA tutorial session.

January 2015, another new year, another RINA workshop. This time in Ghent, as part of a Flemish research project called RINAiSense – which should be pronounced like the French renaissance – that would investigate RINA in sensor networks (which now falls under the nomer “Internet of Things” (IoT). After the yearly John Day presents RINA sessions, this was also the time to properly introduce the IRATI prototype to everyone with a hands-on VM tutorial session, and to introduce RINAsim, an OMNET++ RINA simulator developed within PRISTINE.

After the workshop, it was time to wrap up IRATI. For an external observer it may lack impact and show little output in publications, and it definitely didn’t deliver a convincing case for RINA as an alternative for TCP/IP. But despite that, I think the project really achieved a lot, in terms of bringing for the first time some tools that can be used to explore RINA, and for the people that worked on it, an incredible experience and deeps insights into computer networks in general. This would not have been possible without the enthousiasm and hard work put in by all those involved, but especially Eduard and the i2cat team.

As IRINA was wrapping up, a paper on the how the shim DIF over Hypervisors could be used to reduce complexity of VM networking was submitted for IEEE COMMAG.

We’re approaching the spring of 2015, and IRATI was now officially over, but there was no time to rest as the clock was ticking on PRISTINE. The project was now already halfway its anticipated 30-month runtime, and its first review, somewhere end of 2014, wasn’t met with all cheers, so we had to step up. This was also the period where some of my other (non-RINA) projects were running out. Up to then, my personal involvement on RINA had been on (software) design our components, reviewing the specs, and the practical hands-on was in using the software: deploying it on the testbeds and validating its functionality. But now I could finally free up time to help Sander on the development of the IRATI prototype.

Our main objective for PRISTINE was on resilient routing: making sure the DIF survives underlying link failures. This has been a long-time research topic in our group, so we pretty much quickly know how to do it at a conceptual level. But there were three requirements: first and foremost, it needed scale: we needed to be able to run something that could be called a network, not just 3 or 4 nodes and not just a couple of flows in the network. Second, it needed stability: to measure the recovery time, we needed to send packets at small but – more importantly – steady intervals and thirdly, we needed measurement tools.

As part of IRINA, we developed a basic traffic-generator, which would be extended for PRISTINE and tailored to suit our needs. Stability was improving gradually over time. Our real problem was scale, to which the biggest hurdle was the configuration of the IRATI stack. It was a complete nightmare. Almost anything and everything had to be preconfigured in json. I remember that by that time, Vincenzo had developed a tool called the demonstrator based on tiny buildroot VMs to create setups for local testing, but this wasn’t going to help us deploy it on the Fed4FIRE testbeds. So Sander developed one of the first orchestrators for RINA, called the configurator for deploying IRATI on emulab.

Somewhere around that time, the one-flow-only-limitation of the shim DIF over VLAN was showing and a shim DIF over Ethernet Link Layer Control (LLC) was drafted and developed. By mapping endpoints to LLC Service Access Points (SAPs), this shim DIF could support parallel flows (data flows and management flows) between the client IPCPs in the layer above.

With the PRISTINE SDK released as part of “openIRATI” somewhere after the January workshop a good month prior, there was another influx of code into the prototype for all the new features (a.k.a. policies). Francesco, who had been managing a lot of the software integration, was also leaving the RINA projects. This is the point where I really noticed that Sander and Vincenzo were quickly losing faith in the future of the IRATI codebase, and the first ideas of branching off – or even starting over – began to emerge.

The next Horizon-2020-proposal deadline was also approaching, so our struggles at that point also inspired us to propose developing a more elaborate RINA orchestrator and make deployment and experimentation with (open)IRATI a much more enjoyable experience. That project, ARCFIRE would start in 2016.

Now, we were still focusing on the basics: getting link state routing running, adding some simple loop-free alternates policy to it, based on the operation of IP FRR and running a bunch of flows over that network to measure packet loss when we break a link. Sander was focusing on the policy design and implementation, I was going to have a look at the IRATI code for scaling up the flow counts, which needed non-blocking I/O. I won’t go into the details, but after that short hands-on stint in the IRATI codebase, I was onboard with Sander to starting looking to options for a RINA implementation beyond IRATI.

It was now summer 2015, PRISTINE would end in 12 months and the project was committed to openIRATI, so at least for PRISTINE, we again had no choice but to plow on. A couple of frustrating months lied ahead of us, trying to get experimental results out of a prototype that was nowhere near ready for it, and with a code base that was also becoming so big and complex that it was impossible to fix for anyone but the original developers. This is unfortunately the seemingly inescapable fate of any software project whose development cycle is heavily stressed by external deadlines, especially deadlines set within the rigid timeline of a publicly funded research project.

By the end of summer, we were still a long way off the mark in terms of what we hoped to achieve. The traffic generator tool and configurator were ready, and the implementation of LFA was as good as done, so we could deploy the machines for the use case scenarios, which were about 20 nodes in size, on the testbeds. But the deployment that actually worked was still limited to a 3-node PoC in a triangle that showed the traffic getting routed over the two remaining link if a link got severed.

In the meantime, Vincenzo had started work on his own RINA implementation, rlite, and Sander and myself started discussing options on a more and more regular basis on what to do. Should we branch off IRATI and try to clean it up? Keep only IRATI kernel space and rewrite user space? Hop on the rlite train? Or just start over entirely? Should we go user-space entirely or keep parts in-kernel?

In the last semester of 2015, Sander was heading for a 3-month research stint in Boston to work on routing in RINA with John and the BU team. By that time, we had ruled out branching off of openIRATI. Our estimate was that cleaning up the code base would be more work than starting over. We’d have IRATI as an upstream dependency, and trying to merge contributions upstream would lead to endless discussions and further hamper progress for both projects. IRATI was out. Continuing on rlite was still a feasible option. Vincenzo was making progress fast, and we knew he was extremely talented. But we were also afraid of running into disagreements of how to proceed. In the meantime, Sander’s original research plans in Boston got subverted by a ‘major review’ decision on the shim Hypervisor article, putting priority on getting that accepted and published. When I visited Sander in Boston at the end of October, we were again assessing the situation, and agreed that the best decision was to start our own prototype, to avoid having too many cooks in the kitchen. Development was not part of some funded project, so we were free to evaluate and scrutinize all design decisions, and we could get feedback on the RINA mailing lists on our findings. When all considerations settled, our own RINA implementation was going to be targeting POSIX and be user space only.

We were confident we could get it done, so we took the gamble. ARCFIRE was going to start soon, but the first part of the project would be tool development. Our experimentation contributions to PRISTINE were planned to wrap up by April – the project was planned to end in June, but a 4-month extension pushed it to the end of October. But starting May, we’d have some time to work on Ouroboros relatively undisturbed. In the very worst case, if our project went down the drain, we could still use IRATI or rlite to meet any objectives for ARCFIRE. We named our new RINA-implementation-to-be Ouroboros, the mythical snake that eats its own tail represented recursion, and also – with a touch of imagination – resembles the operation of a ring buffer.

ARCFIRE

Another year, another RINA project kick-off, this time it was again in Barcelona, but this time without a co-located workshop. ARCFIRE (like IRATI before it) was within the FIRE framework, and the objective was to get some experiments running with a reasonable number of nodes (on the order of 100) to demonstrate stability and scale of the prototypes and also to bring tooling to the RINA community. The project was coordinated by Sven van der Meer (Ericsson), who had done significant work on the PRISTINE use cases, and would focus on the impact of RINA on network management. The industry-inspired use cases were brought by Diego López (Telefónica), acteur incontournable in the Network Functions Virtualization (NFV) world. The project was of course topped off with i2cat, Nextworks, and ourselves, as we were somewhere in the process of integration into IMEC. The order at hand for us was to develop an fleshed-out testbed deployment framework for RINA, which we named Rumba. (A rhumba is a bunch of rattlesnakes, and Ouroboros is a snake, and it was written in Python – rhumba already existed, and rumba was an accepted alternate spelling).

In early 2016, the RINA landscape was very different from when we embarked on IRATI in 2013. There were 2 open source prototypes, IRATI was the de-facto standard used in EC projects, but Vincenzo’s rlite was also becoming available at the time and would be used in ARCFIRE. And soon, the development of a third prototype – ouroboros – would start. External perception of RINA in the scientific community had also been shifting, and not in a positive direction. At the start of the IRATI project, we had the position paper with project plans and outlines, and the papers on the shims showed some ways on how RINA could be deployed. But other articles trying to demonstrate the benefits of RINA were – despite all the efforts and good will of all people involved – lacking in quality, mostly due to the limitations of the software. All these subpar publications did more harm than good, as the quality of the publications rubbed off on the perceived merits of the RINA architecture as a whole. We were always feeling this pressure to publish something, anything – and reviewers were always looking for a value proposition – Why is this better than my preferred solution?, Compare this in depth to my preferred solution – that we simply couldn’t support with data at this point in time. And not for lack of want or a lack of trying. But at least, ARCFIRE had at 2 years to look forward to, a focused scope and by now, the team had a lot of experience in the bag. But for the future of RINA, we knew the pressure was on – this was a now or never type of situation.

Ouroboros

We laid the first stone on Ouroboros on Friday February 12th, 2016. At that point in time Ouroboros was still planned as a RINA implementation, so we started from the beginning: an empty git repository under our cursor, renewed enthousiasm in our minds, fresh specs – still warm from the printer and smelling of toner – in our hands, and Sanders initial software design and APIs in colored marker on the whiteboard. Days were long – we still had work to do on PRISTINE, mind you – and evenings were short. I could now imagine the frustration of the i2cat people, who a couple of years prior were probably also spending their evenings and nights enthousiastically coding on IRATI while, for us, IRATI was still a (very interesting) job rather than a passion. We would feel no such frustrations as we knew from the onset that the development of Ouroboros was going to be a two-man job.

While we were spending half our days gathering and compiling results from our LFA experiments for PRISTINE, which – fortunately or unfortunately depending on the way I look at it – did not result in a publication, and half our days on the rumba framework, our early mornings and early evenings were filled with discussions on the RINA API used in Ouroboros. It was initially based on IRATI. Flow allocation used source and destination naming information – 4 objects that the RINA specs (correctly, might I add) say should be named: Application Process Name, Application Process Instance Id, Application Entity Name and Application Entity Instance Id. This naming information as in IRATI, was built into a single structure – a 4-tuple – and we were quickly running into a mess, because, while these names need to be identified, they are not resolved at the same time, nor in the same place. Putting them in a single struct and passing that around with NULL values all the time was really ugly. The naming API in Ouroboros changed quickly over time, initially saving some state in an init call (the naming information of the current application, for instance) and later on removing the source naming information from the flow allocation protocol altogether, because it could so easily be filled with fake garbage that one shouldn’t rely on it for anything. The four-tuple was then broken up to pass two 2-tuple name and instance-id, using one for the Process, the other for the Entity. But we considered these changes to be just a footnote in the RINA service definition, – taste, one could take it or leave it, no big deal. Little did we know that these small changes were just the start – the first notes of a gentle, breezy prelude that was slowly building towards a fierce, stormy cadenza that would signify the severance of Ouroboros from RINA almost exactly one year later.

Another such change was with the register function. To be able to reach a RINA application, you need to register it in the DIF. When we were implementing this, it just struck us that this code was being repeated over and over again in applications. And just think about it, how does an application know which DIFs there are in the system?. And if new DIFs are created while the application is running, how do I feed that information? That’s all functionality that would have to be included in every RINA application. IRATI has this as whole set of library calls. But we did something rather different. We moved the registering of applications outside of the applications themselves. It’s application management, not IPC. Think about how much simpler this small change makes life for an application developer, and a network administrator. Think about how it would be if – in the IP world – you could create a socket on port 80 or port 443 from the shell, and set options on that socket from the shell, and then tell your kernel that incoming connections on that socket should be sent to this Apache or that Nginx program from the shell, and all that the Apache or Nginx developers would need to do is call accept() and read/write/select/epoll etc calls, instead of having to handle sockets and all their options. That’s what the bind() and register() calls in Ouroboros do for Ouroboros applications: you bind some program to a name from the command line, you register that name in the layer from the command line , and all the (server) program has to do is call flow_accept() and it will receive incoming flows. It is this change in the RINA API that inspired us to name our very first public presentation about Ouroboros, at FOSDEM 2018, IPC in 1-2-3.

When we tried to propose them to the RINA community, these changes were not exactly met with cheers. The interactions with that community was also beginning to change. RINA was the specs. Why are we now again asking questions about basic things that we implemented in IRATI years ago? IRATI shows its works. Want to change the specs: talk to John.

We had also implemented our first shim DIF, which would allow to run the Ouroboros prototype over UDP/IPv4. We started with a UDP shim because there is a POSIX sockets API for UDP. Recall that we were targeting POSIX, including FreeBSD and MacOS X to make the Ouroboros prototype more accessible. But programming interfaces into Ethernet, such as raw sockets, were not standard between operating systems, so we would implement an Ethernet shim DIF later. Now, the Ouroboros shim DIF stopped being a shim pretty fast. When we were developing the shim DIFs for IRATI, there was one very important rule: we were not allowed to add functionality to the protocol we were wrapping with the RINA API, we could only map functions that were existing in the (Etherent/UDP) protocol. This – was the underlying reasoning – would show that the protocol/layers in the current internet were incomplete layers. But that also meant that the functions that were not present – the flow allocator in particular – would need to be circumvented through manual configuration at the endpoints. We weren’t going to have any of that – the Ouroboros IPCP daemons all implement a flow allocator. You may also be wondering why none of the prototypes have a shim DIF directly over IP. It’s perfectly possible! But the reason is simple: it would use a non-standardized value for the protocol field in the IP header, and most IP routers simply drop such packets.

Somewhere around April, we were starting the implementation of a normal IPCP in Ouroboros, and another RINA component was quickly becoming a nuisance to me: the Common Distributed Application Protocol or CDAP. While I had no problem with the objectives of CDAP, I was – to put it mildly – not a big fan of the object-oriented paradigm that was underneath it. Its methods, read/write, create/destroy, start/stop make sense to many, but just like the HTTP methods PUT/GET/DELETE/POST/… there is nothing fundamental about it. It might as well have just one method, execute. It’s taste, and it definitely wasn’t my taste. I found that it only proved my long-holding observation that for every engineer there are at least three overengineers. I made a bold prediction to Sander: one day, we would kick CDAP out of the Ouroboros prototype.

Summer was approaching again. Most of the contributions to PRISTINE were in, so the ARCFIRE partners could start to focus on that project. There was a risk: ARCFIRE depended on the Fed4FIRE testbeds, and Fed4FIRE was ending and its future was not certain. The projected target API for rumba was jFed. To mitigate the risk, we made an inventory of other potential testbeds, and to accomodate for the wait for the results of the funding calls, we proposed (and got) an extention to ARCFIRE with 6 months to a 30-month project duration. In the end, Fed4FIRE+ was funded, ARCFIRE had some breathing space – after all, we had to fire on all cylinders to get the best possible results and make a case for RINA – and Sander and myself had some extra time to get Ouroboros up and running.

Sander quickly developed an Ethernet LLC shim DIF based on the UDP one, and after that, we both moved our focus on the key components in the normal IPCP, implementing the full flow allocator and building the data transfer protocol (DTP), and the routing and forwarding functionality. CDAP was getting more and more annoying, but apart from that, this part of the RINA specs were fairly mature following the implementation work in IRATI, and the implementation progress was steady and rather uneventful. For now.

Work on the PRISTINE project was wrapped up, and the final deliverables were submitted at the end of October. PRISTINE was a tough project for us, with very little outcomes. Together with Miquel, I did make some progress with RINA standardization in ISO JTC1/SC6. But Sander and myself could show few research results, no published papers where we were the main authors. PRISTINE as a whole also fell short a bit in its main objectives, the RINA community hadn’t substantially grown, and its research results were still – from an external vantage point – mediocre. For us, it was a story of trying to do too much, too soon. Everyone tried their best, and I think we achieved what was achieveable given the time and resources we had. The project definitely had some nice outcomes. Standardization at least got somewhere, with a project in ISO and also some traction within the Next Generation Protocols (NGP) group at ETSI. RINAsim was a nice educational tool, especially for visualizing the operation of RINA.

Our lack of publication output was also noticed by our direct superiors at the University, who got more and more anxious. The relationship deteriorated steadily, we were constantly nagged about publications, minimum viable papers, and the value proposition of RINA: killer features, killer apps. For us, the simplicity and elegance of the design was all we needed as a motivation to continue. There were some suggestions to build a simulator instead of a full prototype. My feeling was that a simulator would be unconvincing to show any benefits of RINA – I can’t express in words how much I hated that phrase. To prove anything, simulators need to be validated against the real thing. And there are certain pitfalls that can only be found in an implementation. This is the reason why I chose that particular quote at the top of this blog post. Both parties started to sound like broken records to eachother, every meeting was devolving into a pointless competition in who-knows-the-most-workarounds. As the saying goes, arguing with an engineer is like wrestling a pig in the mud. There wasn’t anything constructive or useful to those interactions, so we stopped giving a shit – pardon my French. The Ouroboros prototype was coming along, we were confident that we knew what we were doing. All we needed was time to get it done. We’ll write a paper on Ouroboros when we had one worth writing.

By January 2017, we had a minimal working normal IPCP. Sander was looking into routing, working on a component we called the graph adjacency manager (GAM). As its name suggest, the GAM would be responsible for managing links in the network, what would be referred to as the network topology, and would get policies that instruct it how to maintain the graph based on certain parameters. This component, however, was short-lived and replaced by an API to connect IPCPs so the actual layer management logic could be a standalone program outside of the IPCPs instead of a module inside the IPCPs, which is far more flexible.

Ouroboros diverges from RINA

In the meantime, I was implementing and revising CACEP, the Common Application Connection Establishment Phase that was accompanying CDAP in RINA. Discussions on CACEP between Sander and myself were interesting and sometimes heated – whiteboard markers have experienced flight and sudden deceleration. CDAP was supposed to support different encoding schemes – the OSI presentation layer. We were only going to implement Google Protocol Buffers, which was also used in IRATI, but the support for others should be there. The flow allocator and the RIB were built on top of our CDAP implementation. And something was becoming more and more obvious. What we were implementing – agreeing on protocol versions, encoding etc – was something rather universal to all protocols. Now, you may remember that the flow allocator is passing something – the information needed to connect to a specific Application Entity or Application Entity Instace – that was actually only needed after the flow allocation procedure was basically established. But after a while, it was clear to me that this information should be there in that CACEP part, and was rather universal for all application connections, not just CDAP. After I presented this to Sander despair over IRC, he actually recognized how this – to me seemingly small – change impacted the entire architecture. Now, I will never forget the exchange, and I actually saved that conversation as a text file. The date was February 24th, 2017.

...
<despair> nice, so then dev.h is even simpler
<despair> ae name is indeed not on the layer boundary
<dstaesse> wait why is dev.h simpler?
<despair> since ae name will be removed there
<dstaesse> no
<dstaesse> would you?
<despair> yes
<despair> nobody likes balls on the line
<despair> it's balls out
...

Now, RINA experts will (or should) gasp for air when reading this. It refers to something that traces back to John’s ISO JTC1/SC6 days working on Open Systems Interconnect (OSI), when there was a heavy discussion ongoing about the “Application Entity”: where was it located? If it was in the application, it would be outside of SC6, which was dealing with networks, if it was in the network, it would be dealt with only in SC6. It was a turf battle battle between two ISO groups, and because Application Entities were usually drawn as a set of circles, and the boundary between the network and the application as a line, that battle was internally nicknamed – boys will be boys – the balls-in, balls-out question. If you ever attended one of John’s presentations, he would take a short pause and then continue: “this was the only time that a major insight came from a turf war”: the balls were on the line. The Application Entity needed to be known in both the application and the network. Alas! Our implementation was clearly showing that this was not the case. The balls were above the line, the network (or more precise: the flow allocator) doesn’t need to know anything about application entities! Then and there, we had found a mistake in RINA.

Ouroboros now had a crisp and clear boundary between the flow in a DIF, and any connections using that flow in the layer above. Flow allocation creates a flow between Application Instances and after that, a connection phase would create a connection between Application Entity Instances. So roughtly speaking – without the OSI terminology – first the network connects the running programs, and after that, the programs decide which protocol to use (which can be implicit). What was in the specs , what the RINA API was actually doing, was piggybacking these exchanges! Now, we have no issues with that from an operational perspective: en effet, the Ouroboros flow allocator has a piggyback API. But the contents of the piggybacked information in Ouroboros is opaque. And all this has another, even bigger, implication. One that I would only figure out via another line of reasoning some time later.

With ARCFIRE rolling along and the implementation of the rumba framework in full swing, Sander was working on the link-state routing policy for Ouroboros, and I started implementing a Distributed Hash Table (DHT) that would serve as the directory – think of the equivalent of DNS-SRV for a RINA DIF – a key-value store mapping application names to addresses in the layer. The link-state routing component was something that was really closely related to the Resource Information Base – the RIB. That RIB was closely coupled with CDAP. Remember that prediction that I made about a year prior, somewhere in April 2016? On September 9th 2017, two weeks before the ARCFIRE RINA hackathon, CDAP was removed from Ouroboros. I still consider it the most satisfying git commit of my life, removing 3700 lines of utter uselessness – CDAP got 3 out of 4 characters right. From that day, Ouroboros could definitely not be considered a RINA implementation anymore.

It was time to get started on the last big component: DTCP – the Data Transfer Control Protocol. When implementing this, a couple of things were again quickly becoming clear. First, the implementation was proving to be completely independent of DTP. The RINA specs, you may recall, propose a state vector between DTP and DTCP. This solves the fragmentation problem in TCP: If an IP fragment gets lost, TCP would resend all fragments. Hence TCP needs to know about the fragmentation in IP and only retransmit the bytes in that fragment. But the code was again speaking otherwise. It was basically telling us: TCP was independent of IP. But fragmentation should be in TCP, and IP should specify its maximum packet size. Anything else would result in an intolerable mess. So that’s how we split the Flow and Retransmission Control Protocol (FRCP) and the Data Transfer Protocol (DTP) in Ouroboros. Another mistake in RINA.

With FRCP split from DTP in roughly along the same line as TCP was originally split from IP, we had a new question: where to put FRCP? RINA has DTCP/DTP in the layer as EFCP. And this resulted in something that I found rather ugly: a normal layer would “bootstrap” its traffic (e.g. flow allocator) over its own EFCP implementation to deal with underlying layers that do not have EFCP (such as the shim DIFs). Well, fair enough I guess. But there is another thing. One that bugged me even more. RINA has an assumption on the system, one that has to be true. The EFCP implementation – which is the guarantee that packets are delivered, and that they are delivered in-order – is in the IPCP. But the application process that makes use of the IPCP is a different process. So, in effect, the transfer of data, the IPC, between the Application Process and the IPCP has to be reliable and preserve data order by itself. RINA has no control over this part. RINA is not controlling ALL IPC; there is IPC outside of RINA. Another way of seeing it, is like this: If a set of processes (IPCPs) are needed to provide reliable state synchronization between two applictions A and B, who is providing reliable state synchronization between A and the IPCP? If it’s again an IPCP, that’s infinite recursion! Now – granted – this is a rather academic issue, because most (all?) computer hardware does provide this kind of preserving IPC. However, to me, even theoretical issues were issues. I wanted Ouroboros to be able to guarantee ALL IPC, even between its own components, and not make any assumptions! Then, and only then, it would be universal. Then, and only then, the unification of networking and IPC would be complete.

The third change in the architecture was the big one. And in hindsight, we should already have seen that coming with our realization that the application entity was above the line: we moved FRCP into the application. It would be implemented in the library, not in the IPCP, as a set of function calls, just like HTTP libraries. Sander was initially skeptic, because to his taste, if a single-threaded application uses the library, it should remain single-threaded. How could it send acknowledgements, restransmit packets etc? And the RINA specs had congestion avoidance as part of EFCP/DTCP. At least that shouldn’t be in the application!? I agreed, but said I was confident that it would make the single-threaded thing work by running the functionality as part of the IPC calls, read/write/fevent. And congestion avoidance logic should be in the IPCP in the flow allocator. And that’s how it’s implemented now. All this meant that Ouroboros layers were not DIFs, and we stopped using that terminology.

By now, the prototype was running stable enough for us to go open source. We got approval from IMEC to release it to the public under the GPLv2 / LGPL license, and in early 2018, almost exactly 2 years after we started the project, we presented the first public version of Ouroboros at FOSDEM 2018 in Brussels.

But we were still running against the clock. ARCFIRE was soon to end, and Ouroboros had undergone quite some unanticipated changes that meant the implementation was facing the reality of Hofstadter’s Law.

We were again under pressure to get some publications out; in order to meet ARCFIRE objectives, and Sander had to meet some publication quota to finish his PhD. The design of Rumba was interesting enough for a paper, the implementation allowed us to deploy 3 Recursive Network prototypes (IRATI, rlite and Ouroboros) on testeds using different APIs: jFed for Fed4Fire and GENI, Emulab for iMinds virtual wall testbed, QEMU using virtual machines, docker using – well – docker containers, and a local option only for Ouroboros. But we needed more publications, so for ARCFIRE Sander had implemented Loop-Free Alternates routing in Ouroboros and was getting some larger-scale results with them. And I reluctantly started working on a paper on Ouroboros – I still felt the time wasn’t right, and we first needed to have a full FRCP implementation and full congestion avoidance to make a worthwile analysis. By then I long had a feeling that my days at the university were numbered, it was time to move on, and I was either leaving after submitting a publication on Ouroboros, or without a publication on Ouroboros.

We finished the experiments for ARCFIRE, but as with PRISTINE, the results were not accepted for publication. During the writing of the paper, a final realization came. We had implemented our link-state routing a while ago, and it was doing something interesting, akin to all link-state routing protocols: a link-state packet that came in on some flow, was sent out on all other flows. It was – in effect –doing broadcast. But… OSPF is doing the same. Wait a minute. OSPF uses a multicast IP address. But of course! Multicast wasn’t what it seemed to be. Multicast was broadcast on a layer, creating a multicast group was enrollment in that layer. A multicast IP address is a broadcast layer name! Let that one sink in. Based on the link-state routing code in the normal IPCP, I implemented the broadcast IPCP in a single night. The normal IPCP was renamed unicast IPCP. It had all fallen into place, the Ouroboros architecture was shaped.

But we had no value proposition to pitch, no value-added feature, no killer app, no unique selling point. Elegance? I received my notice on Christmas Eve 2018. Life as a researcher would be over. But what a ride those last 3 years had been. I’d do the same all over again.

The paper was submitted in January 2019. We haven’t received any word from it since.

With the GPL license on Ouroboros, Sander and myself decided to continue to update the prototype and build a bit of a website for it. So, if you made it all the way to the end of this blog post: thank you for your interest in the project, that’s why we did what we did, and continue to do what we do.

Stay curious,

Dimitri