Feb 132013

I have had an interesting exchange of thoughts at an event I’m participating. I asked a colleague (who will remain unnamed) why his particular focus on NDN over something like, say, PURSUIT came about.

His response was astounding to me, certainly unexpected. The central point that emerged is that the highly stateful operation of NDN is a challenge that is unknown to actually work. The Internet so far has operated stateless in terms of flow operation (oddly enough, the forwarding state in terms of IP tables seem to be discounted). This point took me by surprise, to say the least, but I can follow the line of thinking that such massive change from the ‘rather’ stateless IP to a more massive stateful mode is interesting as a challenge, albeit such proposal to move complexity into the network is not new with past research areas, such as Active Networking.

Why is massive stateful operation interesting though? The argument is seemingly that it enables a number of interesting network-internal operations, such as hop-by-hop congestion control, multi-path, etc. But is it really true that one needs increasing state in the forwarders, meaning is it a necessary condition? My answer to this is clearly no. State in such problems does not disappear. The point is where your solution will place the state and placing it in the forwarders (by attaching increasingly complex control logic to the forwarding tables) is only ONE way of doing things. In other words, a choice of stateless forwarder, such as enabled by our LIPSIN solution in PURSUIT, does not prohibit such network-internal control and our own work in PURSUIT on these topics are daily proofs of this point.

Is stateless forwarding really less interesting? Let us first re-iterate the opportunities that solutions such as LIPSIN or our recently developed multi-stage extension (which scales to any tree size without any false positives) provide. Forwarders in this world only hold information about their own outgoing links. There is NO forwarding information required beyond this, no forwarding information that carries any names, nothing like forwarding information bases (FIBs) required in solutions like NDN. The forwarding operation is very simple (essentially comparing the bit patterns of your own links with those in the packet header), which allows for efficient implementation in software, hardware, even directly optical!

Where’s the challenge now? Similar to the congestion control argument above, state does not disappear in a problem like forwarding. It is placed somewhere else and it is here where the challenge lies. In the PURSUIT architecture, a function that potentially holds this state is the topology management and formation core architectural function, essentially performing path computation and header construction if LIPSIN is your choice of forwarding. The challenge here lies in performing these operations well, fast,  and possibly distributed. The work reported in the ICNC 2013 shows the feasibility of performing such path computation at speed, while however supporting Steiner tree heuristics. Our work in the IEEE Communications Magazine July 2013 issue reports on our early results to perform slow path operations that form the basis for the stateless fast path. It clearly is a challenge but one that is interesting and promising in early results.

Is such stateless data plane desirable? I do envision that a world of simple forwarders holds tremendous potential in terms of energy efficiency and optimisation potential. The first point comes from its simple operation as well as the lack of needing memory. This might lead to extremely simple, even core network, forwarders that operate at extremely high speed. Secondly, the chosen approach leaves many options where the state (which, again, will not disappear) finally resides. One such choice, albeit negating the advantages mentioned above, could be the forwarder itself. This would turn the forwarders into NDN-like forwarders of similar complexity, performing topology formation in a highly distributed way. More likely, however, is to hold the state in a regionally distributed topology formation, also for mobility support reasons, optimising these network nodes in terms of computational efficiency while keeping the actual forwarders simple. Point though is that this degree of freedom is interesting and a challenge in itself to better understand.

Stateless forwarding – boring or not? I would personally say no for maybe obvious reasons, but stateless forwarders hold many promises that are an equally radical departure from the still rather complex world of forwarding that we have today. This challenge has kept many of us busy over the years, so check out in our papers and deliverables where we have come down that road.

 Posted by at 09:11
Aug 222012

The recent ACM Computer Communication Review (CCR) in July 2012 featured an article that combines Turing’s fundamental work in Computer Science with recent advances in convex optimisation, establishing information-centric concepts as the ones enabling layered architectures that are robust yet cater to the fragile nature that often occurs in the Internet.

This work is a more unusual outcome of our architectural thinking within the PURSUIT project. It connects to work by Prof. John Doyle in the space of optimisation theory, although starting from Alan Turing’s fundamental 1936 theorem to proof the Entscheidungsproblem. The work connects, albeit unproven, dots laid out by these fundamental pieces of work and leads to formulate design concepts that are at the heart of layered architectures. It is here that information-centric concepts and our work in PURSUIT comes to fruition.

In case such unusual viewpoint on ICN and its potential for a wider impact on architectures in general, check out the article.

 Posted by at 00:27
Aug 202012

I have heard it now too often (as recent as during the AsiaFI summer school) and it needs to be addressed here: the mobility problem in ICN is NOT solved by simply re-subscribing (or re-sending interests, depending what ‘language’ you are speaking) from the subscriber side!

With recent discussions, e.g., in the IRTF, that focus on publisher mobility, there is an assumption that I’m hearing too often lately in presentations, namely that subscriber mobility is a done deal - just re-subscribe!

Yes, it is a brute force solution to a problem that is significantly more challenging than the simple solution suggests. Re-subscribing is indeed possible but one has to keep in mind the possible implications of this approach. Per device, there are likely many pieces of information that the device’s software is interested in. Hence, what looks like a straightforward solution quickly turns into a nightmare to happen on your wireless link.

Let’s expand on this by assuming a mobile device that holds 1000 active subscriptions to individual information items – that’s not an unreasonable number, considering mashed-up (and highly desegregated) content on, e.g., a webpage or a distributed filesystem app running on your device (think Google Drive), or many other possible apps running while you are using your mobile device. Changing your access point now leads to re-subscriptions to these 1000 items – in a basic re-subscription solution, this leads to an upstream traffic burst of approximately 1000*(average_length_of_ID+Ethernet header) (in case you use Blackadder which operates directly on Ethernet – you need to add any overlay overhead for other deployments). With an average length of, say, 30 bytes per ID, that’s 30k+ per handover. Make that 10000 objects being active, and you reach 300k+. At the same time, let us consider mobility in wireless environments where more than one device is handing over at any time – so you need to multiply any figure with the number of mobile handsets  that are doing so.

You possibly see where this is going. Re-subscribing is, clearly, a SIMPLE solution to a problem that can be very hard to solve EFFICIENTLY!

The considerations above leave out the computational overhead that these messages create (either at the topology manager in the PURSUIT case or through the distribution within the network and the necessary PIT updates in CCN). I even assert that this computational overhead is something that we will need to deal with in any case. The main point here though is that the wireless access network is a scarce resource by any measure, even with increasing link speeds in recent technologies. Filling this bandwidth with control traffic, initiated by the mobile handset, seems just simply wrong, while seemingly ignoring the possibility for network-assisted handovers.

It is the latter that is one of the reasons for the explicit topology management that is realised in the PURSUIT architecture. While it allows for simple solutions such as re-subscription for mobility management, it also allows for network-assisted solutions that can possibly avoid a signalling avalanche that is outlined above.

I wish that in future presentations, I will see less claims that subscriber mobility is a done deal - it’s hard and let’s realise that!

 Posted by at 07:07
Aug 032012

We’ve updated our Deliverables page with a list of deliverables from PURSUIT that we have produced throughout the year. You can now find updates to the architecture (as well as a security analysis), information about implementation components, integration as well as demonstration, evaluation at architectural and business level and (last but not least) information about our dissemination activities within the project.

So check it out – there is lots of information available!

 Posted by at 13:16
Jul 102012

Since our PSIRP efforts, much work has gone into design and realisation of our vision that is the information-centric networking (ICN) Internet. PURSUIT continued this work since September 2010.

The IEEE Communications Magazine has now run a number of special issue articles on the ICN topic. The efforts in PURSUIT are represented by two articles (among 5 total articles – that’s a great achievement!), one on caching and mobility (discussed here) and one on the overall design and implementation. In the latter article by George Parisis and myself, you can find the main design tenets, the fundamental layering in our design approach as well as the realisation of all of this within our line-speed prototype Blackadder. This article, needless to say, is the result of the many discussions and the hard work of the wider PURSUIT team.

For those of you who have followed our deliverables, much of the text will be well-known. It serves, however, as an anchor point for references to our design and implementation work that can be used by ourselves and others who find the PURSUIT work relevant. It also provides some new insights into the performance of our prototype, and we also illustrate the layering tenet through a segmentation example that utilises algorithmic identification as a neat approach to relate seemingly unrelated information items through algorithmic relations that are embedded into the item identifiers.

A section that we added based on the feedback from the editors showcases how we see other ICN architectures (including today’s IP) being enabled by the design tenets that we bring forward in this article. While we haven’t gone through all of the necessary details for this enablement, we do assert that there is a common set of tenets that can enable a breadth of design choices, such as CCN/NDN, NetInf and others. What is missing, however, is a concise and deep write-up on this aspect – a long-lived exercise that keeps getting pushed down the line of writing, it seems.

Check out the article through IEEE explore or send an email for a copy.

 Posted by at 14:25
Apr 202012

Today, we published the Technical report TR12-001. In this report, we argue that there is a larger architectural and system design argumentation as to why ICN research is worthwhile pursuing. Its assertion is that ICN merely for improving content dissemination is not appealing enough. Instead, we create, in this report, a connection between the design of (information-centric) architectures and new findings in optimisation theory based development of systems and solutions. This report intends to stimulate the discussion as to why ICN research is useful and what is its architectural contribution. More is to follow…

 Posted by at 09:45
Mar 072012

The Journal of Information Policy has just published a special issue of TPRC 2010 papers, which includes a revised version of a paper from D. Trossen and A. Kostopoulos. The paper studies the tussle space that is created in an Internet that is based on information-centric networking ideas. With that, the paper provides insight into possible socio-economic implications that a paradigm shift towards PURSUIT ideas might potentially have.

The publisher’s abstract to this paper reads:

“Can the Internet be redesigned to reduce future conflicts? The Internet’s underlying architecture, Internet Protocol (IP), was introduced in 1974. Since then many ideas have been put forward about how to update and improve it. One branch of these is called “Information-Centric Networking” (ICN). Trossen and Kostopoulos note how ICN could improve the ability of the Internet to resolve conflicts between the various constellations of stakeholder interests, conflicts that they call “tussles.” Introducing a “tussle taxonomy,” they provide examples of how tussles might be resolved differently in ICN. They believe the ICN model would help rationalize pricing in a three-sided market; reduce congestion and transit costs; provide more transparency; offer more choices and possible outcomes with respect to issues such as privacy, intellectual property, and data protection; and better enable not just present but future business models that actors within the system might strive to establish.”

A PDF version of the paper can be found at the Journal’s special issue page.

 Posted by at 14:40
Mar 012012

Two PURSUIT partners, the Aalto University in Helsinki and the Athens University for Economics and Business, have offered pub/sub courses and seminars to their students as part of their curriculum. The course material of both of these courses is now available on our website! Please check them out on our page for the academic courses and provide feedback and comments.

The material is licensed under Creative Commons license, fostering its usage by the wider academic community. We also provide material on student feedback and lessons learned, which can prove useful for others thinking of providing a similar course.

If you have any questions, please do let us know since we are committed to spreading the PURSUIT story to the young generation of researchers!

 Posted by at 10:51