Tech on rob.sh

NANOG 90: Pondering Abstractions

Mon, 12 Feb 2024 22:12:00 -0500

I had the pleasure of giving the keynote presentation at NANOG90 - sharing some thoughts and lessons that we have learnt in the 10 years since we started the OpenConfig project.

This was a really enjoyable presentation to put together and give. It balanced being able to look back at what we’ve learnt, and also think about some important lessons that I wanted to share with the networking community.

Published IETF RFCs

Thu, 23 Nov 2023 10:00:00 +0000

Over the years I have published a number of RFCs in the IETF. They are listed below.

As primary author:

RFC7684 - OSPFv2 Prefix/Link Attribute Advertisement
RFC7777 - Advertising Node Administrative Tags in OSPF
RFC7855 - Source Packet Routing in Networking (SPRING) Problem Statement and Requirements
RFC8355 - Resiliency Use Cases in Source Packet Routing in Networking (SPRING) Networks
RFC8370 - Techniques to Improve the Scalability of RSVP-TE Deployments
RFC8402 - Segment Routing Architecture
RFC8660 - Segment Routing with the MPLS Data Plane
RFC8662 - Entropy Label for Source Packet Routing in Networking (SPRING) Tunnels
RFC8665 - OSPF Extensions for Segment Routing

As contributor:

Reimagining Network Devices

Wed, 12 Apr 2023 11:28:50 +0000

Some reflections on the development of Software-Defined Networking, and how it has impacted the ongoing re-imagining of network devices that OpenConfig, and associated projects has driven.

Almost 10 years ago, there was a shift in the IP networking industry. The move towards SDN, and its adoption by hyperscalers as a means to break apart traditional network architectures had set the scene for disruption. The question of “how are we using SDN?” was on the lips of vendor and telco executives — and lead to many initiatives in the industry - both those that can be thought of “SDN” and those that were more incremental.

NANOG 86: Emulating Network Topologies in k8s

Tue, 11 Oct 2022 16:00:00 -0800

Marcus Hines and I spoke at NANOG86 on some of the work that we’ve been doing related to emulating network topologies in Kubernetes, and how this relates to improving network testability.

The slides can be found here and there is a video on YouTube.

OpenConfig Public Projects

Sun, 17 May 2020 22:15:00 -0800

There are a number of public projects that we’ve been working on over the last few years in OpenConfig, and published from Google. It seemed like it might be worth giving a brief “hitchhikers guide” that glues together some of the different projects that we’ve published on GitHub.

Of course, the initial output of OpenConfig, which has motivated much of this ecosystem is the data models — which are publicly available on GitHub.

IETF98: OpenConfig Observations

Wed, 29 Mar 2017 09:00:00 +0100

Anees Shaikh and I put together some thoughts that we shared with rtgwg at IETF 98 in Chicago. The slides are linked below.

FutureNet: Model-Driven Automation

Thu, 01 Sep 2016 10:40:00 -0700

Anees Shaikh and I presented at future:net talking about automation work that we’ve been doing in OpenConfig, and I shared some of the NMS implementation I’ve been working on recently. Slides are linked below.

OpenConfig and IETF YANG Models: Can they converge?

Tue, 02 Aug 2016 11:30:00 +0000

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.

What is applied configuration?

The first question to an uninitiated reader might be, what is “applied configuration”? It’s not a term that has been in the common network nomenclature - and hence does need some further explanation. To define it, we need to look at the way that configuration is changed on a network element.

OpenConfig Interfaces - Some Examples

Tue, 08 Sep 2015 23:23:00 +0000

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.

RFC5218, RSVP-TE and Segment Routing.

Fri, 14 Mar 2014 12:30:00 +0000

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. It's always nice to see how networking is taught, and hear from students in such a high-ranking uni. I've included the slides below for posterity - Mark filmed the presentation, so perhaps there'll be video at some point in the future!

Speed of Internet Innovation.

Wed, 31 Oct 2012 23:38:38 +0000

A question that came up at an event I was at yesterday: How will the time between the first (commercial) deployment of a telephony service, and a regulated universal service obligation for telephony compare to that of the time between the first (commercial) Internet services being deployed and a USO for IP connectivity (e.g., Broadband)?

Based on this, is the cycle time of the telephony regulatory bodies, and mechanisms through which changes are implemented within these bodies suitable for Internet services?

Answers on a postcard please.

Some Initial Thoughts on the Software-Defined Network (SDN).

Fri, 19 Aug 2011 18:42:35 +0000

At one of the Ericsson R&D days, Professor Scott Shenker - who's an academic at the University of California in Berkeley, presented on a concept that he calls the "software defined network'. Now, if you haven't seen the presentation - it's definitely worth watching (it's on YouTube, here), and provides quite an engaging look at the problem of network scaling from the perspective of academia, and especially in terms of a comparison to the more rigorous disciplines of computer science, like OS design.

Progress with Error Handling for BGP

Wed, 03 Aug 2011 22:08:14 +0000

It's been quite a while since I updated this blog, very lax of me, sorry!

The lack of updates appears more indicative of how busy I appear to have been since presenting the error handling draft work at NANOG (which looks to be the last post!). Since January, I've presented at the IETF in Prague, and then again in Qu�bec City - particularly on a number of aspects of the work that I've been documenting here for some time!

NANOG 51 Presentation

Fri, 25 Mar 2011 14:00:43 +0000

The video from the presentation I gave a NANOG, LINX and UKNOF has now been posted. You can find the video at the following URL - NANOG 51: BGP Error Handling or by clicking on the image below. The full slide deck is also on this site - here.

BGP Error Handling - Developing an Operator-Led Approach in the IETF

Sat, 29 Jan 2011 05:02:13 +0000

As I presented at UKNOF 18, I have now written an Internet-Draft to address the requirements of Network Operators for how BGP should handle errors in UPDATE messages. The draft can be found on the IETF site, and I'm currently seeking opinions as to whether this reflects the an operational consensus! If you're an Operator (DFZ, MSE or otherwise), it would be great to hear from you!

I'll be presenting the draft at NANOG 51 in Miami on Tuesday - if you're there, feel free to ping me!

LINX71 - 100GE in the Lab

Thu, 23 Dec 2010 16:32:57 +0000

I spoke at LINX71 about the testing that we (C&W) have been doing in the lab with 100GigE - we got a pre-production card and hence had a look at the technology for real. Thanks to LINX, the presentation video can be seen by clicking on the image below.

Once again, however, whatever LINX use as a presentation laptop didn't render my slides properly - even though I'd submitted PDF too! Hence the slides can be found on this site.

BGP Error Handling and Enhancements Post IETF-79

Sun, 14 Nov 2010 22:41:46 +0000

With IETF 79 happening last week - I think one of the great things that's coming out of the IDR work leading up to the meeting has been that quite a few drafts have been written around the requirements that exist in BGP for better error handling. I've been vocal about this before, of course, so it's not that surprising that I'm (yet again) banging the drum for this cause, however, we are getting somewhere finally. To that end, I was wanting to air some views on a couple of the drafts that either have benefits to the operational community, or don't quite hit the mark.

Cycling Video

Sat, 19 Jun 2010 11:46:02 +0000

Checking out a few videos that people have linked me to recently I thought that this piece was amazing - really great speed. It also looks like the 5D and 7D are really quite awesome at doing 60fps HD! The video presentation over at vimeo is really cool too!

PUSH PULL from Landis Fields on Vimeo.

Digital Economy Bill YouTube Questions

Sun, 02 May 2010 12:51:09 +0000

So, if we take a moment to look at the following responses to questions that the leaders of the three parties involved in the “Digital Debate” on YouTube gave, concerning the Digital Economy Bill:

Sure, we get some tired old rhetoric, as expected. However, the key point here is that both Labour and the Conservatives appear to believe that they've done the right thing with this bill. Combine this with the fact that Gordon Brown mentioned a broadband rollout as part of the few ideas that he could during one of the debates, and I think that it starts to become apparently that politicians do not understand the UK "Internet" industry. Where there can be comments as to who is being "looked after" by each party (Cameron even mentions that the bill is most important for the media producers (or 'rights holders")) - I think the problem here is that politicians in the UK fundamentally do not understand how this industry operates. I think increasingly we are going to see the UK fall behind in terms of what we can roll-out due to impractical over-taxation, and ideas such as those put forward in the DEA.

Looking simply at two issues:

Fibre Taxation - in the UK, if a business is to light up a fibre pair, as well as any standard taxes (e.g. VAT) that must be paid, then an additional VoA Business Rate is due on these fibres. This can be up to �500/pair/year outside of London, and �600/pair/year in the London metro region [source: Valuation Office Agency].

Let's look at what this does for the telecommunications industry in the UK, especially for small players. Since such a company probably does not have a DWDM system, then the relatively cheap fibre runs are now taxed quite highly, should such a company then want to start increasing their capacity, then the additional costs are inflated due to taxation. Where larger players might be able to split these rates over a large number of DWDM channels (up to 32 or 64) a smaller provider might only have one channel - and hence the cost of infrastructure or customer links for smaller companies is inflated, due to the fact that they cannot justify the CapEx required for such multiplexing systems. Even for larger players, this isn't encouraging large scale fibre build out. If tax is paid per route-KM for every FTT{H,P,C} deployment, then this adds an additional overhead (in avoidable taxation!) to any such roll-out. Hardly an incentive for a commercial entity to begin such a deployment! Alongside the CapEx, OpEx, and business rates you are required to pay - the UK government will tax you just for lighting up the infrastructure they are encouraging you to build! This alone is not helping with any of the three party's plans for any kind of broadband roll-out, especially to rural areas where there is no profit for commercial entities to roll out such technologies.
Digital Economy Act - Andrew Cormack of JANET (UK) gave an excellent presentation at UKNOF relating to the DEA. There are two key points here:
- The government (and apparently the Tories) believe that this bill being pushed through in "wash-up" was the right thing to do. Contrast this with the fact that they also appear to be stating that the digital economy (and communications that such an economy provides) is key for Britain. I agree it's key, we're a services based economy, and if more services can be provided utilising the Internet, then one of two things will happen. Either the UK will not be equipped to deliver such services globally, and the "Digital Economy" will mean that these can then be out-sourced to other countries - or the UK will be in a position to grow the services that it can deliver, with the considerable skill of the UK workforce, into both global and European markets. Any bill therefore, that affects the manner in which this "Digital Economy" (by which I'm now referring to ISPs and telcos), should therefore, one would have thought, justify reasonable debate by the fully attended (?!) Commons!
- Westminster appears to have no idea as to who they are legislating for. I am not against ensuring that the creative industries are able to protect their rights - however, this needs to be done in a manner that can be policed without damaging another industry. As Andrew said in his presentation the Government is unsure of how many ISPs are in scope - stating it could be 5, 10, 20 or 450. How can the impact of legislation be considered, if the Government cannot identify the scope? In addition, whilst many rights holders, I would imagine, will say "well, there is very little that is being requested of the ISPs here!" - the technical challenges of implementing mechanisms whereby specific IP addresses, and users can be located, within the timeframes that such complaints appear to take to be progressed, should be costed. I believe that most people within the xSP industry are not going to say "We don't care about your rights as a content producer", however, how can the Government expect our industry to pay directly to police this? We don't care that customer X is pulling data A, B and C - really, once it comes down to working in a larger ISP, we care about getting bit X to endpoint Z whilst ensuring any commercial guarantees that we have made for bit X.
Another concern following these points is that it appears that very few of the UK ISP industry are being directly consulted here. Whilst there may be involvement - it's not something that I have seen mention of particularly amongst smaller ISPs in the community. Government should remember that legislation such as this affects all enterprises within this sector, and hence should consider them. The role of incumbents within this country already affects the delivery of many services, we don't need further legislation to push things further into their favour.

The reason I feel the need to mention this, is that it aggravates me whilst seeing responses such as the above. Politicians cannot absolve themselves of blame for such issues being pushed through in what I feel is quite an undemocratic manner. I'm still not sure who I am going to vote for - but as far as I see it, the huge lack of understanding of the industry within which I work will mean that whoever is in power during the next Parliament will likely not be in the right place to make legislation that actually takes into account how this industry works. Because of this, the UK's economy will suffer - which is a great shame.

UKNOF 16: Enhancing BGP

Mon, 26 Apr 2010 11:12:10 +0000

After a late programme committee request, I presented on “Enhancing BGP” at UKNOF 16. The presentation was intended to be an update on the current drafts in the IDR working group, and give some encouragement to operators to get involved, and contribute.

I’ll put the video up when the Tom at PortFast and Brandon of Bogons have done their excellent job on it. For the meantime, the slides are linked below.

There's also a good add-paths presentation that John Scudder and Dave Ward gave at NANOG here

Juniper PSN-2010-01-626 (AS4 Again!)

Fri, 08 Jan 2010 07:55:37 +0000

I’ve had a couple of mails relating to this PSN, which again references the research that Andy Davidson, Jonathan Oddy and I did last year. It seems that some of the sources of the initial mailing list posts we made are gone (particularly the merit.edu one that is referenced from both Juniper’s site and most other places). For that reason, I’ve included both the mails that we sent to NANOG/C-NSP/J-NSP last year here.

Visualising MPLS-TE Networks

Wed, 30 Dec 2009 23:54:04 +0000

For all network deployments, there is a requirement to present information relating to both topology, and various utilisation statistics to some human operator. In many cases, this process has become so ingrained in network requirements that there are almost ubiquitous solutions to the visualising data - for example, link utilisation is almost always presented via some framework or tool powered by RRDTool. Other tools, such as network "weathermap" diagrams linking this utilisation information into an overview of a network topology are also seen in many NOCs. In most cases, the problem of visualising data relating to a flat MPLS or IP network is solved for most common deployments.

Network Updates and Opportunities

Sat, 12 Dec 2009 12:06:52 +0000

A quick personal post to break the silence here!

I’m currently very interested in hearing about any UK or EU-based network engineering or architecture opportunities that are out there, especially in SP networks that run MPLS with TE. If anyone has some such opportunity, or knows of something that they think might suit me – please drop me a mail to rjs@rob.sh for a copy of my CV.

An outline of my CV is available on LinkedIn.

I’m hoping to find some time to put some technical articles together that can be posted here in the near future.

LINX 65 Presentation

Mon, 15 Jun 2009 00:01:49 +0000

Further to my previous post - I presented this issue at LINX65 - video and slides can be found below.

Video
Fixed Slides - LINX’s PowerPoint install seems to have corrupted my slides on the day.

Comments and feedback are most welcome.

32-bit AS numbers introduce a new BGP flaw.

Mon, 19 Jan 2009 20:23:59 +0000

Last Friday, Andy Davidson, Jonathan Oddy, and I pushed out some research that has some quite worrying repercussions. Whilst I’ve heard from a lot of people privately about this matter, there’s a big flaw here, and as Andy posted on his blog (which is much more informative than mine, I think!), this is a big problem.

The reason, I think, that we’re getting limited public discussion of this exploit (I hesitate to call it an exploit, it’s a flaw really, because it’s actually a result of the RFC that the problem exists), is because the implementations of 4-byte AS support that are out there already are generally not standards compliant. Let’s run down the list:

Building the RIPEDB server

Wed, 08 Oct 2008 12:03:52 +0000

It took me a few hours over the course of this week to build the RIPE whois server for some internal projects – given that there seems to be a very limited amount of documentation for the build process, and threads on mailing lists, I’m going to post this here. I hope that it gets picked up by Google.

The first problem that is encountered is that the libtool that is included with the whois server does not support ‘modern’ tags, such as –tag=CC. This looks to be because the included libtool is somewhat dated. This can be easily fixed by using the system libtool:

IPv6 - It Doesn't Just Work.

Tue, 30 Sep 2008 06:13:15 +0000

I was reading an entry posted by Brett Carr on Nominet’s techblog today entitled “ipv6 It just works”. Unfortunately, for IPv6, and for the sentiment behind this message (IPv6 can be run pretty easily!), in my experience, IPv6 - it doesn’t just work!

It’s easy to dismiss the previous sentence, given that many networks aren’t designed to run IPv6, and there’s kit out there that’s just not IPv6-capable yet. When building the AS29636 network, we specified that IPv6-capability was one of the things that would be a requirement of the kit that was going into the new network, not just something that we’d like to have. We work to a similar specification at my current employer, - which ensures that we can deploy IPv6 within a pre-agreed timeframe once we have some commercial drive for it (either from customers, or for business continuity reasons). I think that this is the best way for a SP network to be a the moment - there’s no revenue in having IPv6 deployed (generally), but there might be lost revenue when a customer comes to your network with IPv6 as a requirement in their RFQ…

Returning to the reason that I started writing this post - the problems for IPv6 deployment don’t just come from the fact that your hardware doesn’t necessarily support it, and it isn’t just that running IPv6 on your kit might have financial implications for the software licensing that you’re going to be deploying (the arbitrary Cisco requirement for advipservices for IPv6 is a completely separate post). There are going to be issues where you don’t necessarily expect them - which can be hard to debug, where IPv6 “should just work”, it doesn’t.

Without mentioning any specifics of a case that was brought to my attention in the last couple of weeks - a customer was having problems getting IPv6 traffic flowing across a layer 2 ethernet circuit. The expectation of this circuit that you can put ethernet frames onto it (and it doesn’t really matter what the ethertype is, just that they’re valid ethernet frames) - and they are going to be punted down the link, to whatever you terminate the L2 circuit on. With IPv4, this not working would be a disastrous failure - the product just wouldn’t be working. However, this particular circuit was not passing frames that contained IPv6 packets. As it turns out, the carrier’s equipment in the path contained a firmware bug that was causing the frames containing IPv6-packets to be dropped - and hence, no neighbour-discovery, and no traffic flow between the two ends of the circuit.

This is just one isolated case - but the question is, where else in your network do you have a problem like this one? How much kit that may, right now, be considered something that shouldn’t be interfering anywhere above L2, is going to exhibit this type of problem? How much load is this going to cause your NOC? How much time liasing with circuit suppliers, and telcos is going to be spent actually deploying IPv6 on your network? I think these questions are starting to form a basis of why SPs should be startng to roll out IPv6 onto your network now. The lack of transition plan from IPv4 to IPv6, and the fact that IPv6 hasn’t had widespread deployment testing across many platforms and transmission media mean that deploying IPv6 in a rush across your network isn’t necessarily going to be as easy as you’ve thought.

Whilst I applaud the fact that Nominet are ensuring that they’re going to be ready to run the UK ccTLD with IPv6 nameservers, and that their infrastructure is ready - I don’t think that IPv6 is going to be quite as easy to deploy as Brett found in his blog post.

ic.ac.uk fetchmailrc Settings

Sat, 15 Mar 2008 18:08:52 +0000

Imperial College are currently implementing changes so that you need to access either POP3 or IMAP with SSL enabled, I figured since they didn’t list Fetchmail in their new site, then I’d post my configuration (.fetchmailrc) here in case anyone else uses it:


poll icex.imperial.ac.uk 
    proto pop3 
    user "USERNAME" 
    password "PASSWORD" 
    is "LOCALADDRESS" here 
    ssl 
    sslfingerprint "7D:E8:74:1F:E8:B1:E6:15:A6:0C:02:2B:BA:89:BE:4D"

Enjoy.

Django

Sat, 01 Mar 2008 21:11:42 +0000

Since I’ve got a few moments, and I’ve decided to actually write down some rants rather than deciding that I can’t be bothered to - I’m going to use some space to single the praises of Django.

I’ve been using Django for a couple of years now - since around the autumn of 2005, and as such, feel that I’ve got a pretty good grasp of how the framework works. I haven’t really hacked around that much with the innards of Django (although I did propose a patch), however, what I really like about this framework isn’t particularly the internals, but just the whole philosophy that there seems to be in terms of building a web application.

crontab hacks

Fri, 29 Feb 2008 14:52:55 +0000

30 23 28-31 * * [ "`date +%m`" != "`date +%m --date=tomorrow`" ] && /Users/rjs/bin/monthEnd.py 2>&1 >/dev/null

Pretty handy for running on the last day of the month - and should work on Linux.

RFID Presentation

Fri, 29 Feb 2008 11:33:30 +0000

For anyone interested, the slides for my RFID presentation are here.

RFID Basics!

Thu, 21 Feb 2008 16:28:50 +0000

So, at the moment, I’m writing a presentation about the operation and the security implications of RFID. During the course of the random searches around the internet, I’ve found that there’s a lot of really, really cool work going with respect to RFID. Even more great than the output on the subject is who is studying it. Lots of really cool observations are coming out of the open source friendly community - some of the best presentations on the subject are from presentations at CCC. Along with projects like OpenPCD, this output is pretty cool!

However, that’s not really the point of this post. During the course of reading around, I’ve found that whilst there’s a lot of information around - there’s also a lot of FUD that surrounds that information. My presentation is trying to give people (with some physics background) a simple idea of what RFID is, and particularly how it works. Given that I’ve already done a quick summary of how RFID works, I figured I’d blog about it, so that I can add to the mush of material that you just can’t reference online.

I’ll discuss a high frequency system - since cards such as MIFARE (which e.g. Oyster uses) work at around 13.56MHz. The RFID system consists of two elements - the reader, and the tag. Tags come in a number shapes - active, passive, and semi-passive. Really, it’s the passive tags that I’m interested in. The image below shows the anatomy of a (simple) passive tag. It’s composed of an antenna - running around the card, an IC, and a substrate that they’re both attached to.

iPhone SDK

Mon, 26 Nov 2007 19:37:15 +0000

I finally got myself an iPhone - and am loving it. It’s great how I can now sync my calendars, and address book to my phone without having to worry at all about having six clones of each event on my calendar (which of course, makes it rather difficult to tell what I’m actually meant to be doing that day). However, a topic that has come up a couple of times in discussion with a few friends is that of the iPhone SDK. I feel that the big question here is, “Do Apple have enough incentive to make a fully featured iPhone SDK?”.

With a friend moving to work at a VoIP start-up that deals with having a client on mobiles that allows SIP calls to be made, the big discussion we have been having is whether the iPhone SDK will allow a VoIP client to be implemented on it. My initial feeling on this is, no - not initially. It’s been documented in a number of places that Apple are taking call revenue from the networks on each iPhone that is sold. If this is true, then it would be against Apple’s interest to actually allow a functional SIP implementation make it onto non-hacked iPhones - since they’re going to lose money if users start making their calls via SIP rather than via the cell networks (this assumes that Apple get revenue based on all calls - not just based on the actual contract worth).

However, I can’t say that I’m sure of this - Apple may only be taking their cut from the revenue that is generated from the subscription fee on each iPhone - rather than the additional calls, and in this case, they might feel that allowing users to utilise VoIP when they’re in a hotspot area would be another cool feature that the iPhone can offer. They might also feel that a lot of the iPhone users aren’t savvy enough to be using SIP very often - I guess something like Skype from hotspots (or iChat for voice, or Google Talk…) might be more popular with the less tech-savvy userbase. It’s hard to call really.

Alternatively, Apple might just wait until the networks stop paying them revenue, and roll the SDK with better network support then, increasing sales on a device that they’re no longer making such revenue on.

Either way, the iPhone really just slots in where a phone should, it works with wireless and a mobile-data mechanism without having to think about it at all (although I’d like an 802.1X implementation). Calendar data syncs, Mail accounts sync, my Music syncs, my contacts sync - it integrates with my (primarily Apple based) digital life very well.

I’m impressed with my iPhone - roll on the SDK so that I can start making it do even funkier things!

Linking against GSL on OS X 10.5 Leopard

Thu, 15 Nov 2007 11:22:43 +0000

Since I’m taking the Computational Physics module in my third year at IC, we’re using some libraries like GSL to provide “better-than-default” random number generators and such like. It turns out that those of us using a Mac don’t get GSL installed by default with Xcode, or under OS X - and unlike Windows and Linux - there’s no instructions on the course site. Here’s a really quick way to ensure that you can link against it: