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The IETF uses Jabber for instant messaging during working group meetings, as does the IAB for its own teleconferences and meetings. Since I didn’t really feel like shopping around for a Jabber account, and XMPP integration with Google Talk shut down in the middle of the decade, I decided a few years ago to run my own server, which I pretty much only use for connecting to IETF conference rooms and for chatting with IETF folks as a backchannel during meetings.


I always love going to Schloss Dagstuhl, a retreat for computer scientists in the middle of nowhere in Saarland, Germany. It’s a little difficult to get to, but the train ride (Wallisellen to Saarbrücken via Zürich and Mannheim) is a nice, slow way to step back from whatever context-switching overhead is dominating my days at the moment and start thinking about the theme of the workshop. Last October, I went to what’s probably my last Dagstuhl seminar for a while, spending three days around the billiard table and in the wine cellar figuring out whether there’s anything to be done about Encouraging Reproducibility in Scientific Research of the Internet.


A year and some after Switzerland’s plucky protofascist poster art collective cum Trumpist political party, the SVP (Swiss People’s Party), screamed Verfassungsbruch! (lit. “Constitution break!”; fig., accusative: “you’re breaking the Constitution!“) on the floor of Parliament at the admitted non-implementation of their unimplementable vandalism of the Swiss constitution in the name of nativism, they’re back at it again with the almost-reasonable-sounding Selbstbestimmungsinitiative (lit. “self-determination initiative”; SBI if you’re into hashtags). One has to read the details to see how broken it is.


I’m writing today from Berlin, after an excellent Passive and Active Measurement conference and a very long but fruitful week in London for IETF 101, which, for me, came to be dominated by the The Spin Bit. The spin bit is an explicit signal for passive measurability of round-trip time, currently possible in TCP but not in QUIC due to lack of acknowlegment and timestamp information in the clear. It’s an example of a facility designed to fulfill the principles for measurement as a first class function of the network stack we laid out in an article published last year.


I don’t think I’ve ever written a completely optimisic post about politics, but today seems as good a day as any to try. Today was an Abstimmungssonntag (“referendum Sunday”) here, and the most important question before Switzerland at the national level was a revocation of the federal government’s authority to levy a compulsory television and radio fee: NoBillag. I’ve already written about this referendum, and how it represented not a mere return of four hundred francs per year to every household, not a mere privatization of a few television and radio stations (one of which I’m listening to right now), but a frontal assault on public media and an attempt to drive the country’s media landscape into low-information territory; in other words noch ein Schritt zum kriechenden Beitritt der Schweiz in die vereinigten Staaten(1).


Selected Publications

We introduce a lightweight, transport-independent and explicit replacement for TCP timestamps for passive latency measurement in TCP and QUIC. This latency spin signal supports per-flow, single-point and single direction passive measurement of end-to-end RTT using just three bits in the transport protocol header, leveraging the existing dynamics of the vast majority of Internet-deployed transports.
In IMC 2018, 2018

We propose an architectural solution to the blindness of network functions driven by increasing deployment of encryption, by introducing a new “path layer” for transport-independent, in-band signaling between Internet endpoints and network elements on the paths between them, and using this layer to reinforce the boundary between the hop-by-hop network layer and the end-to-end transport layer. We define a path layer header on top of UDP to provide a common wire image for new, encrypted transports. This path layer header provides information to a transport-independent on-path state machine that replaces stateful handling currently based on exposed header flags and fields in TCP; it enables explicit measurability of transport layer performance; and offers extensibility by sender-to-path and path-to-receiver communications for diagnostics and management.
In CNSM 2017, 2017

We seek to generalize the idea of measurement within protocols, e.g., the way in which TCP relies on measurement to drive its end-to-end behavior. Rhetorically, we pose the question “what if the stack had been built with measurability and diagnostic support in mind?”. We start from a set of principles for explicit measurability, and define primitives that, were they supported by the stack, would not only provide a solid foundation for protocol design going forward, but also reduce the cost and increase the accuracy of measuring the network.
ACM Computer Communication Review, April 2017 (Best of CCR 2017), 2017

Recent Publications

More Publications

(2018). Three Bits Suffice - Explicit Support for Passive Measurement of Internet Latency in QUIC and TCP. In IMC 2018.

PDF Code

(2018). Tracing Internet Path Transparency. In TMA 2018.


(2017). A Path Layer for the Internet - Enabling Network Operations on Encrypted Protocols. In CNSM 2017.

PDF Slides

(2017). TinyIPFIX for Smart Meters in Constrained Networks. RFC 8272.


(2017). Challenges with Reproducibility. In ACM SIGCOMM Reproducibility 2017.


(2017). Tracking transport-layer evolution with PATHspider. In ANRW 2017.


(2017). copycat - Testing Differential Treatment of New Transport Protocols in the Wild. In ANRW 2017.


(2017). Post Sockets - Towards an Evolvable Network Transport Interface. Proc. IFIP/IEEE Networking Workshop on Future Internet Transport.


(2017). Principles for Measurability in Protocol Design. ACM Computer Communication Review, April 2017 (Best of CCR 2017).