On the pivotal role of post-doc in research groups

A sabbatical is a great opportunity to study the internal process of other research groups. For a young European scientist like me, there is much to get from observing what American professors implement for the management of their large teams. In general, academic people are reluctant to apply industry-like management processes, which are supposed to prevent groups to be creative and lively. However, the research is becoming objective-driven, and the raise of grant agencies and project-oriented funding makes that an unexperienced young professor can now receive enough money to hire a large team of researchers. There is a need to address the tabooed topic of research group management.

A unique characteristic of research groups is the huge gap between a graduate "master" student, who has some scientific background but actually knows nothing, and a senior post-doc, who is supposed to be a peer, fellow researcher. One of the purposes of a research group is to assist the development of new skills… and to let people leave when they are, at last, autonomous and efficient.

It is my understanding that post-docs are the most challenging to work with. Some of them are super-PhD, while some others are rather mini-professor. Most of them do no longer require to be "tutored", but they still have to acquire some critical skills. In particular post-docs should ideally develop their own ideas from scratch, tutor younger students, actively contribute to industrial collaborative project, and expand their professional network.

On the one hand, delegating is dangerous for a professor. If a collaborative project fails, the one that will be directly affected in the future is the professor, not the post-doc. If young students spend too much time working on barely publishable ideas, utilize old-school technologies and miss latest exciting papers, it is the professor who eventually has to make the student catch up, not the post-doc. On the other hand, delegating is a real chance to expand the research group, to work on new areas, and to offer the opportunity to the new post-doc to acquire critical skills/experiences she misses.

For these reasons, the management of a post-doc is very touchy. On my side, I consider the following:

• before opening a post-doc position, I will clearly define my needs. I identified at least three critical needs that might pop up someday, and that would justify opening a post-doc position:
• I want to be assisted for tutoring young students
• I want to partly delegate the management of a heavy collaborative project
• I want to explore a well-identified brand new topic
• once my needs identified, I hope that finding a matching post-doc will be easier. Compared to my previous experience, I will pay more attention to the actual motivations of candidates, and I will pay less attention to their background or their past achievements. Of course it is important to know whether the candidate can write paper or produce experimental stuff at the expected level of quality for a top academic conferences, but it is even more important to know what is the status of the candidates regarding the need.
• then, if objectives are clear and well-understood on both sides, I guess the collaboration shall be more productive.

About faculty positions in Europe (and especially in French Grandes Ecoles)

I hear a lot of complaints from post-docs and near-end PhD students about the quasi-impossibility to obtain a faculty position in North America today: too few open positions and too many very strong candidates with impressive publication history and dithyrambic recommendation letters. When I ask these frustrated candidates "Do you consider positions in Europe?", they usually look at me strangely. Europe?

Since we have an open tenured faculty position in my lab, I think it is time to explain what a faculty position means in Europe / in France / at Telecom Bretagne.

Life for faculties in Europe. The vast majority of universities (and research centers) are located in the downtown of major cities. There is no university in the middle of nowhere in Europe. A typical city hosting an university is a major city in the sense that such city concentrates everything you need for a reasonably good urban life: shops in downtown, cultural events, and good public transport (metro, train, airport). In cities inhabited by more than 300.000 people, you can find everything, especially services and jobs. Smaller cities are generally also lively nice places to live. For example, the city of Brest (France, 170.000 people, 300.000 with suburbs) is incomparably more lively than Waterloo (Ontario, aggregated population of 400.000 people with Kitchener and Cambridge).

There is of course a language issue, since countries like France, Italy or Spain are still not exactly english-friendly. I think it is no longer a major issue for teaching. Most good universities have developed english-based courses, and recruiters prefer now a strong international candidate to fluent ones. Besides, I have three comments: (i) things change, the ratio of people speaking english increases, Europeans themselves travel more and get used to dealing with people from abroad countries. (ii) from my experience, kids are fluent in a new language in less than one year. It might be harder for parents, but people with a decent social life should be able to converse in a couple of years. (iii) multilingualism is one of the key assets of Europe. It is a chance for curious intelligent open-minded people. And faculties are expected to be curious intelligent and open-minded.

One of the major drawbacks of Europe is that every country has its own recruitment process. Since 2007, all European universities have the same curriculum. I think it is just a question of time that higher Education policies will be harmonized as well. But it is currently the main issue, typified by the crazy French system.

Faculty positions in France. All faculty positions in France are tenured: once you get hired, you can stay here forever. Moreover, the life in France is among the very top worldwide (in particular weather, cultural life, infrastructure and service quality). The combination of the above should place France as the first location for young scientists from all over the world. France however suffers from two critical drawbacks.

The first drawback is the recruitment process, which has been created by French for French. It is a ridiculous Kafkaian system, which actually prevents the development of competitive French research centers, In short, if you are not within the system, you have no chance to get in because you simply cannot know how to apply. There are in France four decent research places: universities (for traditional associate-professor and professor position), CNRS (full-research position in fundamental areas), INRIA (full research positions in Computer Science) and Grandes Ecoles (traditional professor positions but teaching only to small population of graduating students). Each of these places has its own recruitment process, with a lot of specific French acronyms and terms. They all require candidates to dive into websites with no guarantee that the English translated page is accurate and updated. For example, the recruitment at CNRS is based on the concept of Sections. Should you be able to know your Section, you might face some terrible issues like understanding this wonderful PDF. Universities have the worst recruitment process. Go to this portal if you are crazy enough to candidate, but please don't forget that if you want to apply for 2012 recruitment process, you first had to apply before Dec 31st 2011 in order to be authorized to actually apply four months later. No kidding. INRIA has the best recruitment process (with a LaTeX template for the application). Grandes Ecoles are autonomous small entities without much visibility. For the brand new Institut Mines-Telecom, the new recruitment website is still under construction, with a lot of infamous 404 pages and various links toward webpages in French.

The second drawback is the salary. In France, you cannot be a rich scientist. For CNRS and traditional university positions, it is even worse. A young scientist with a tenured position in an university cannot live decently at Paris. The salary (around 2000 euros monthly after tax) ruins your chances to find any apartment in Paris and nearby. INRIA and Grandes Ecoles are a bit more reasonable with monthly salary starting around 2500 euros. For example, after five years of experience, my salary is slightly higher than 3000 euros after tax. In all French cities (except Paris and Nice), such a salary allows a comfortable life, but it is still borderline for a family. The comparisons to other countries are not in favor of France. On the one hand, there are still many candidates despite the low salaries. On the other hand, best candidates, especially those who know the US system, are reluctant to apply.

This particular position at Telecom Bretagne. For young scientists with young (or upcoming) kids, Telecom Bretagne is an outstanding place, with a scenic oceanic coast, a kid-friendly climate (temperatures ranging from 5˚C to 20˚C), and cheap housing (a 4-bedroom house near the beach can be rented for less than 1000 euros per month). Brest is considered as one of the ugliest French city, but, with respect to world standard, it is still a nice lively city with an attractive homogeneous downtown. I would argue that Brest is typically a better place than the majority of cities in US, Germany or Japan.

Telecom Bretagne is one of these strange typically French "Grandes Ecoles". In short, the best French students go to Grandes Ecoles for graduating as engineers. Since Grandes Ecoles are dynamic small entities, specific partnerships with the best institutions all over the world have also been created in order to attract excellent abroad students (one third of students at Telecom Bretagne are not French). Hence, professors teach to small-size international population of smart students with whom it is possible to experience new pedagogical processes, including active learning and project-based education. However, these students will become engineers (the ratio of students willing to go to PhD is less than 0.1) and they are highly-demanding in average.

Fifteen years ago, Grandes Ecoles were only about teaching. The recent development of research activities explains the diversity of profiles in the so-called "departments". Professors with academic ambitions are free to develop their own research agenda, but they will have to find grants in order to hire PhD students and post-doc. Fortunately, the school has strong industrial relationships and good connections with major French research centers, therefore it is not that hard to find money if the research activity is within a hot area.

The day a rejected paper will end up in court

Conferences are no longer nice meetings among gentlemen who care about science. They are the center of a huge competition for thousands of scientists. An acceptance in a major conference can change the career of a scientist and the daily life of a laboratory. It is money and it is fame.

The goal of the peer-reviewing process has naturally shifted from validating the accuracy of a scientific work to selecting a subset of papers. The reviewers have mutated into hunters tracking any reason to crush a paper. All the gentle and polite manners from "guides of peer-reviewing" sound so XXth century. In computer sciences, the "hypercriticality" of scientists is well identified.

Unfortunately, all harsh reviewers are not gifted. Reasons for rejecting a paper frequently come from wrong beliefs, from major misunderstanding or from an obsession for a tiny flaw. These are negative badly-justified reviews, which sometimes make the authors speculate about a possible bias in the reviewing process: the reviewer was a competitor in the same domain, the reviewer was not an expert, the reviewer had personal grievances against the authors, the reviewer was a well-established scientist who does not want to see any newcomer out there...

What are the options for an angry author with a supposed unfairly-reviewed paper and its negative consequences (the money loss and the degraded career)? Let's call a lawyer.

The roles of every entity involved in the traditional academic process are well summarized in this nice paper. Sometimes, the editor of the venue describes the process in used. But the reality is that there is no well-defined rule, no engagement. In fact, it is written nowhere that every paper should be fairly reviewed. An author can only hope that the process is fair because the process is usually said to be fair. I have actually no idea what a lawyer could do versus a no-rule process.

I have always been astonished by Boeing (or Airbus) appealing a decision from an orderer when their bid is rejected. In my naive vision, how can anybody challenge the decision of a private company? When the orderer is the Air Force, there must be rules, for sure, but the idea is the same for a paper to, say, Infocom. But here is the point. There is no Infocom. More precisely, our beloved top-conferences might belong to anybody, including Infocom. I am not sure to know what a lawyer could do versus a no-entity.

Is is serious?

The rebuttal process is probably a good idea, which has the potential to reduce some unfair decisions. But it is still another prehistoric practice based on oral tradition and informal discussions between those who are supposed to be the owner of something that does not exist, except in author's mind. In medicine, some scientists have argued about the creation of a "supreme court" whose role would be to "judge the judges" (here and there). But the motivation is to prevent new scandals related to misbehaving editors. This court would deal with serious cases, not slightly unfair reviews. Maybe academics should look at what has been done in sports to legally organize the structures. Societies like IEEE or ACM could also consider to create a "mediator committee".

Otherwise a rejected paper will end up in court, then who knows who might be considered as responsible.

Incremental improvements for CS conferences

Scientists like to debate about the general organization of academic life. Lately, some have called for a clean-slate revolution based on open archives. Yet, as for the majority of clean-slate proposals on well-established processes, I am doubtful that such a shift can occur. But in the meantime, nothing is done to actually fix the issues of the current process. In particular, I have the feeling that academic conferences in computer science (at least in my communities, which span networking, multimedia and distributed systems) are getting worse, and it seems that nobody cares because the most active researchers in this area are too busy preparing their utopian clean-slate revolution.

So, let me try to give below four incremental improvements that every serious conference should implement, for the sake of a better academic life. Two are quite easy:

• no more deadline extension. A deadline extension is the irrefutable proof that a conference is crappy. A deadline extension means indeed that either the conference does not attract enough solid submissions or the scientists who submit in this conference are unable to finish a work on time. In both cases, it would be a shame to be associated with such a conference. Furthermore deadline extensions bring at least three very negative effects.
• it creates an unfair gap between the happy fews who are in the awareness and the others. A scientist who knows in July 2011 that ICC deadline will be Sep 28 has a different schedule than the other scientist who naively thinks the deadline is Sep 6. 
• it is now folklore to announce an extension a few hours before the deadline. This is highly irrespecutful for the (unaware) authors. Week-ends can be ruined to fulfill a deadline, which you discover on Monday has been extended for two weeks.
• the day before a submission is stressful. A (lately announced) deadline extension multiplies the number of deadline-stressful days by two. Deadline extensions are killing me.
• a list of accepted papers on the conference webpage the day of the notification. Why is it so hard? An ugly txt-formatted list of accepted papers is just what most scientists want for. From such a list, it is possible to find a link toward an ArXiV or a technical report on the webpages of the authors of accepted papers. Moreover, titles are inspiring, the sooner every scientist can read the titles, the more inspiring it is. And don't forget curiosity of course. Who did pass the cut this year?

Two other improvements are less incremental, but I think their impact would be worth.

• no blindness at all. The debate about single vs. double blind is a classic. But very few scientists discuss the blindness of reviewers. There is however a raise of complains about the reviews that are too harsh, scientifically wrong and impolite. It is not hard to believe that if the reviews were signed by their authors, they would be written more carefully. Some argue that this would bring potential desires of revenge among scientists. This ridiculous argument assumes that scientists are no better than kids unable to recognize argued criticisms and unable to retain their negative thoughts. If you are not optimistic about human nature, you should notice that research communities are enlarging. So, the revenge desires of a few bad scientists have really few chances to affect you because the probability that these bad guys represent a majority of reviewers for one of your paper is actually very low. Not mentioning that, academic revengers being stupid people, they are probably not in the committees of top-conferences, so you have nothing to lose. And if you face a majority of reviewers who want to unfairly reject your papers because of your previous bad reviews, well it may be time to consider writing better reviews.
• open access to papers. I have already signed this pledge about open access. I know that academic professional societies (ACM, IEEE and so) have to re-invent themselves but we will not wait them to do it. We cannot degrade the quality of the scientific activity just because a few jobs are in stake.

I think it is the role of the program committee members to alert their chairmen that the academic life would be far better if conferences stick to these simple rules.

What's up in networks (3/3): dash

The last post in this mini-series. After openFlow and hetnets, here is dash.

DASH or Dynamic Adaptive Streaming over HTTP
Although it is not exactly what the MPEG scientists have promoted for a decade, most of today's video traffic is based on HTTP and TCP (Netflix player, Microsoft Smooth Streaming and Adobe OSMF). And it works. The video traffic is exploding: adaptive streaming already represents more than one third of the Internet traffic at peak time, and it is expected to prevail, even on mobiles. Facing this plebiscite, the MPEG consortium has launched the process of standardizing DASH into MPEG.

In short, for a given movie, the video server publishes a manifest file in which it declares several video formats. Each format corresponds to a certain encoding, so a certain quality and a certain bit-rates. All these different videos of the same movie are cut into chunks. A client requesting a movie selects a given video format and then starts downloading the chunks. On a periodic manner, the client tries to estimate whether this video encoding fits the capacity of the network link between her and the server. If she is not satisfied, she considers switching to another encoding for the next chunks. What is the best chunk size, how to estimate the link capacity, what is the best delay between consecutive estimation, how to react to short-term bandwidth changes, how to switch to another encoding… are among the questions that have not received the attention of the scientific community, so every DASH client implements some magic parameters without any concern for potential impacts on the network.

Despite the multimedia scientific community and the video standardization group are large lively communities, many research issues related to DASH have not been anticipated and sufficiently addressed. Among them, I highlight:

• When several concurrent DASH connections share the same bottleneck, the congestion control mechanism of TCP may be compromise. In fact, a DASH connection is based on TCP, which implements an adaptive congestion control with proven convergence toward a fair sharing of the bottleneck among concurrent connections. By incessantly adapting the flow bit-rate DASH may prevent the convergence of TCP. If network bottlenecks locate on links that are shared by hundreds of concurrent DASH flows, the lack of convergence of the congestion control mechanism is a risk. I may overestimate the impact, but at least understanding the impact of DASH adaptive policy (which seems to use a lot of random parameter settings) on the eventual convergence of a congestion control policy is an exciting scientific topic.
• When multiple servers store different video encodings of the same movie, the client may incessantly switch from a video encoding to another. A DASH connection works especially well when the bottleneck is always the same, whatever the chosen video encoding. In this case, the adaptive mechanism converges toward the video encoding that fits the bottleneck capacity. But in today's Internet, the content can be located in various distinct locations: CDN servers, Internet proxies, and content routers with caching capabilities. If the links toward the different encodings have different congestion level, the DASH adaptive algorithm may become crazy. 
• A DASH connection does not support swarming. Swarm downloading (one client fetching a large video content from multiple servers) was expected to be enabled by both the multiple copies of the same content and the chunk-based video format. If every chunk comes from a different server, the congestion cannot be accurately measured. In fact, DASH cannot implement a consistent behavior when multiple paths are used to retrieve the video chunks. 

By the way, DASH is yet another point in favor of HTTP, which is becoming the de facto narrow waist of the Internet. The motivations for using HTTP include its capacity to traverse firewalls and NATs, its nice human-readable names and its capacity to leverage on Internet proxies and CDNs. Somehow, DASH adds congestion control and adaptive content, making the HTTP protocol even more powerful. But the gap between its huge utilization over the Internet and the lack of understanding of its behavior at large scale has the potential to scare network operators. I guess it is the way Internet has always evolved.

What's up in networks (2/3): hetnet

Here is the second chapter of the mini-series about some (not-so-fresh) topics in networking area. After openFlow, hetnet.

Hetnet, or the Heterogeneous Cellular Networks:

I am probably not the only one to get bored by GSM cellular networks: they have been created by phone engineers who disliked Internet, they are full of acronyms, they are controlled by an operator, they just works. But cellular networks are now the most common way to access to the Internet. Moreover the devices using these networks are full-featured computers, which are managed by owners who install a lot of applications. The number of devices connected to cellular networks is expected to grow dramatically.

Next-generation cellular networks have good chances to differ from our plain old GSM networks. Here are two technologies that may change the game:

• femto base stations are small and cheap base stations that anybody can buy and install on its own wired Internet connection (for example here). It means that the clients of a wireless service provider pay (base stations + landline Internet communication + consumed electric power) to improve the infrastructure of the carrier and to have an excellent quality of service at home. Carriers are all jumping into this idea. I still don't understand why would a user prefer to buy a base station and connect to Internet through the 4G although she can use wifi. The main argument is that, wifi wireless spectrum being free and badly managed, a local network can have poor performances because too many wifi access points compete or because too many devices share the pool of wireless channels. The 4G spectrum is licensed and managed by the operator, so some wireless channels can be "reserved" to a user. But if everybody has its own femtocell at home, licensed channels will become scarce too, and nobody will tolerate paying for a femtocell that interfere with the neighbors' ones. In order to tackle this issue, nearby femto base-stations should collaborate to share the wireless spectrum and react to changes in the radio environment (especially when neighbors decide to turn on/off their femto base stations). All scientists interested in peer-to-peer and ad-hoc networks will have fun with the problem of channel allocation: end-users form the infrastructure, ensuring a fair sharing of scarce resources is a challenging objective, clever distributed algorithms should solve the problem, incentives to turn on/off the femtocells should be taken into account. As shown in this article, both deployment and management of femto hetnets are still unclear. Those who are not afraid of acronym orgies can look at these slides for a summary of 3GPP standard and a nice telco-oriented overview of the research problems.
• direct device-to-device wifi communication is a long-awaited feature. Hurrah, WiFi Direct, which is the official name of this feature in the WiFi alliance, is included in the new Android OS version. At least, wifi direct transmission between devices is becoming a reality, which means that the thousands of academic papers about mesh networks and hybrid ad-hoc cellular networks are suddenly worth reading. However, things have changed. Extending the coverage area of base stations, which has been the most frequent motivation in previous works related to mesh networks, is no longer the main concern of mobile carriers. It is now all about mobile data offloading, that is, avoiding communication via the macro base station. In this context, network operators may combine wifi direct and data caching in devices to reduce the amount of requests sent to the Internet. In other words, strategies related to information-centric networks may turn out to be useful in the wireless world.

In a broader perspective, the over-utilization of wireless networks for accessing the Internet highlights an interesting paradox: the wireless transmission is inherently broadcasting (all devices near the wireless router may hear all messages) although the Internet applications are usually designed for unicast communication (a message has only one destination). The capacity of a mobile carrier to leverage on the broadcasting feature of base stations in their cellular networks may become a key asset.

What's up in networks (1/3): openflow

I found time to go a bit deeper into several (not-that-fresh) topics. I hope this quick summary will be of interest for those who did not. First of this mini-series: OpenFlow

OpenFlow, or the Software-Defined Networks:
Thanks to OpenFlow, I now understand the "control plane vs. data plane" idea, which I thought were mysterious magic words allowing telco engineers to recognize themselves. In the OpenFlow world, there are some dumb switches that route packets according to a routing table, and there is a clever controller, which orchestrates these switches. Switch-Controller communication uses the OpenFlow protocol.

The first novelty is that the OpenFlow protocol has been designed at Stanford, therefore (i) it is cool, (ii) software engineers have heard about it, and (iii) it is endorsed by a buzz concept, namely software-defined networking. The second novelty, but a noteworthy one, is that the main network equipment vendors integrate OpenFlow API in their switches (at least Juniper and Cisco). So, it is becoming real: software developers will really be able to control a network remotely.

OpenFlow is both networks and software:

• In the network area, there is only one truth: every new concept is something already done twenty years ago. Good news for OpenFlow: it looks like MPLS. Therefore OpenFlow is a networking concept. \qed
• Computer scientists are driven by vaporous concepts like model abstraction, composition and semantic. Guess what? OpenFlow designers dangerously embrace them. Even worse, network scientists have started publishing in POPL and ICFP.

More seriously, OpenFlow meets a demand. More and more "independent" networks have specific needs that cannot been addressed by router vendors. For example the network in a data-center. Private enterprise networks and even next-generation home networks are also complex networks, which would work better if they could be managed according to the wishes of their owner. OpenFlow provides the friendly interface that allow anybody (should (s)he knows programming) to become the network operator for any such network. Needless to say, this perspective brings a lot of excitements and uncertainties (see for example here and here).