Inspired by Becca on the swing at Bernal Heights. October 2018, spray paint on layered card.



The concept of having no central entity control currency seems attractive to a lot of people. However, trust in some decentralised entity means trusting the way that they operate their business - how they’re able to audit their code, and write bug-free software. The only thing I know about software is that it isn’t ever bug-free. To reduce MTBF, you implement things multiple times, in disjoint environments. That said, the latest hack on a cryptocurrency/smart wallet I saw, made me wonder about their testing.

Migration of Site to Hugo!


Welcome to a new rob.sh, apologies for the outage. I needed to migrate the site to something that was lower maintenance. I’m working on migrating the old rob.sh content to this new site, but it may take a little time to do so. Please let me know if there are specific articles from the old site that you’d like me to prioritise! The site now uses hugo rather than django. This means that I can avoid running a bunch of backend infrastructure.

OpenConfig and IETF YANG Models: Can they converge?

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At IETF96 in Berlin, the chairs of the NETMOD working group, and Operations Area Director (Benoit Claise) published a statement to say “Models need not, and SHOULD NOT, be structured to include nodes/leaves to indicate applied configuration”. Now, this might seem a pretty innocuous statement, but it actually has a number of implications for the data models for network configuration and state that are being produced in the industry.

Lecture at Ecole Polytechnique: Taking Network Management into the 21st Century

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Mark Townsley and Jean-Louis Rougier again invited me to come and lecture at �cole Polytechnique this year. Their course there focuses on analysing the success of network protocols - using the (fantastic) framework laid out in RFC5218. Given that I’d spoken about SR for the last couple of years in my lecture there, and was giving a (slightly) updated version of the SR lecture at Telecom ParisTech for JLR’s ‘Future Internet’ course earlier in the week, I decided to shift the focus of my lecture at X this year to the management plane.

OpenConfig Interfaces - Some Examples

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I’ve talked a little on this site before about what we’re trying to achieve with OpenConfig. However, one of the observations that it’s easy to make is that YANG models alone don’t really achieve anything in terms of making the network more programmable. To make the network more programmable, we need to have tooling that helps us create instances of those modules, manipulate them, and then serialise the into a format that can be used to transmit data that conforms to the model to a device.

The right tool for the job: Choosing where to use RSVP-TE or SR.

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I noted that at NANOG64 this week in San Francisco, there are talks (both from Juniper) about both SPRING/Segment Routing and RSVP-TE. These are both protocols/technology approaches (since one can’t really call SR a protocol) that I’ve been involved in the evolution of over the last few years. A question that I’ve been asked more times than I’d like is why we chose to look at a new approach (SR) rather than go with a technology that exists RSVP-TE.

Working with YANG Models - A brief intro to 'pyangbind'

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Both the Hawaii IETF meeting (IETF91) and the subsequent meeting we had a few weeks ago in Dallas were somewhat YANG-heavy. Following work to move towards YANG as a standard modelling language for network configuration, and the subsequent IESG statement effectively deprecating SNMP as the way that we present network configuration - the IETF, and especially the routing area, has dived head-first into YANG. Indeed, I’ve been occupied somewhat with some really great collaborative work with a number of awesome engineers from Google, Microsoft, AT&T, Level3, Yahoo!

March 2013 - December 2014 on TfL


Oyster usage data from TfL for my Oyster card, March 2013 - December 2014. Data visualisation is with D3.js - mouse-over a station to isolate journeys to and from that location. Larger version.

RFC5218, RSVP-TE and Segment Routing.

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After my presentation at UKNOF on SR, Mark Townsley asked me whether I’d be interested in presenting to his class at the Ecole Polytechnique in Paris, around the thinking (from an ops perspective) of delivering the 5218 concept of “net positive value” through the SR technology, and how the existing protocols that are available might measure up against the criteria that 5218 gives us to consider. We managed to co-ordinate logistics, and I presented to INF566 on Wednesday afternoon, which was a really cool experience.