Paper

In our previous session we looked into Mixnets, more specifically Loopix. With this session we stayed in the space, talking about a network adopting many concepts from Loopix, namely Nym. As a preparation, we read section 1 through 4 of the Nym whitepaper. Introduction Network-level surveillance The Nym Network Design Mixnet for Network-Level Privacy Diaz, Claudia, Harry Halpin, and Aggelos Kiayias. “The Nym Network.” (2021). https://nymtech.net/nym-whitepaper.pdf

34th session was on Mixnets as lots of people suggested in the past. As a preparation we read the Loopix paper. Piotrowska, Ania M., et al. “The loopix anonymity system.” 26th {USENIX} Security Symposium ({USENIX} Security 17). 2017. https://www.usenix.org/system/files/conference/usenixsecurity17/sec17-piotrowska.pdf The corresponding talk by Ania Piotrowska is very much worth watching as an additional resource. https://www.youtube.com/watch?v=R-yEqLX_UvI

In our third BGP session we focused on BGP security, more specifically we discussed how to perform hijack and interception attacks using BGP. The primary paper of the session was: Birge-Lee, Henry, et al. “Sico: Surgical interception attacks by manipulating bgp communities.” Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security. 2019. A good introduction to RPKI can be found here.

After our first BGP session, introducing the protocol based on the convergence problem of BGP, our second session on BGP covered route propagation and tuning. The primary paper was: Gray, Caitlin, et al. “BGP Beacons, Network Tomography, and Bayesian Computation to Locate Route Flap Damping.” Proceedings of the ACM Internet Measurement Conference. 2020.

We decided to turn our interest to BGP which we will devote 3 sessions to. In today’s session - the first one - we introduced BGP, looked at the convergence problem, as well as the solution suggested in the paper below. Gao, Lixin, and Jennifer Rexford. “Stable Internet routing without global coordination.” IEEE/ACM Transactions on networking 9.6 (2001): 681-692. To play around with BGP as well as general Internet routing: ...

What better way to start a new year than with a paper discussing how to change time? In the 30th session we discussed a paper which I think has much up its sleeves - Attacking the Network Time Protocol. First off the paper gives us a good introduction to the inner working of the network time protocol. Next up it examines the broader ecosystem as well as why we need accurate time in the first place. Once we established enough background, the paper dives into how one can attack the protocol, starting off with on-path attacks all the way to some crazy (creative) off-path attacks. Last but not least, the list of references at the end is a small treasure trove. ...

With the 28th session we jumped into the space of byzantine fault tolerant consensus protocols. We covered fault tolerant consensus with various Paxos variants in the past, but this session was the first one looking into how to solve the byzantine generals problem. Instead of using PBFT [1] as a first paper we went with Hotstuff [2] instead. The reasoning behind this choice was (a) Hotstuff presenting a somewhat easy up-to-date consensus algorithm and (b) that it provides a framework enabling one to compare other algorithms (e.g. PBFT) in the space. ...

We have long been planning to cover the caching mechanisms in CPUs. As a shared knowledge base for the discussions in this session we chose the following two articles by Martin Thompson among other things known for his work on the LMAX Disruptor: CPU Cache Flushing Fallacy including a good overview over the different caches in modern Intel CPUs. Write Combining exemplifying the advanced mechanisms one can find in today’s CPUs and how one can make use of them. ...

In the session today we covered Madhavapeddi Shreedhar and George Varghese paper “Efficient fair queuing using deficit round-robin” [1]. While the session was not so much about the relatively simple algorithmic details of deficit-round-robin (still worth checking out) we talked about: Its benefits over basic FIFO queuing and thus its impact for congestion controlled traffic (tcp) compared to not congestion controlled traffic (udp). Its wide deployment still seen today. Its derivatives DRR+ and DRR++ being able to handle both best-effort as well as latency critical flows. ...

After a bit of a break due to current pandemic we decided to carry on and continue our meetings as virtual calls. Ignoring the usual initial hiccups and the missing whiteboard the medium worked well for us. Topic and reading of this session was the ACM Queue article BBR: Congestion-Based Congestion Control [1], as well as the Dropbox article Evaluating BBRv2 on the Dropbox Edge Network [2]. We started off with a quick recap of the previous session covering why we need congestion control, how one can view a multi-hop connection as a single hop connection with a single bottleneck and most importantly the fact that the Internet is the largest distributed system that most of the time “just works” due to congestion control. ...