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These are all posts about BGP, including those originally published on

Will the IPv6 BGP table overtake the IPv4 table before the decade is out?

For my training courses, I always check the current size of the IPv4 and IPv6 BGP tables over at the CIDR Report so I can tell the participants what table size capacity to look for when shopping for routers.

Currently, the IPv4 table is at 925k, readying itself for scaling the 1M summit late next year. The IPv6 table is 160k prefixes.

The IPv4 table grew at about 10% per year in the 2010s and 6% last year. At this rate, it'll be at 1.43 million at the beginning of 2030.

The IPv6 table, on the other hand, had been growing at some 31% per year between 2015 and 2020, but last year it grew 37%. At that rate, the IPv6 table will reach 1.7 million prefixes by 2030! Even at a somewhat slower growth rate of 34% the IPv6 table will overtake the IPv4 table before the decade is out.

Of course it's hard to predict 7.5 years into the future, but stranger things have happened.

Also, at this rate, you'll need a router that can handle more than 2 million prefixes five years from now. Which pretty much means that if you are buying a router today that has to be able to hold the full global IPv4 and IPv6 tables, it should already be able to handle more than 2M prefixes in order to have a five year economic lifespan.

posted 2022-06-30

OSPF: time to get rid of the totally not so stubby legacy

Recently, I was looking through some networking certification material. A very large part of it was about OSPF. That's fair, OSPF is probably the most widely used routing protocol in IP networks. But the poor students were submitted to a relentless sequence of increasingly baroquely named features: stub areas, not-so-stubby-areas, totally stubby areas, culminating in totally not-so-stubby areas.

Can we please get rid of some of that legacy? And if not from the standard documents or the router implementations, then at least from the certification requirements and training materials?

Full article / permalink - posted 2022-05-12

Dutch cabinet says BGP in good hands at IETF in response to Facebook incident

Laurens Dassen, a new member of the Dutch parliament after the March elections, representing the pan-European party Volt, put several questions about the October 4th Facebook outage to the Dutch cabinet (administration). Yesterday, minister Blok of the ministry of Economic Affairs and Climate answered those. The fourth question was about BGP, among other things.

Full article / permalink - posted 2021-11-11 - 🇳🇱 Nederlandse versie

→ Software Engineering Radio: Iljitsch van Beijnum on Internet Routing and BGP

I love podcasts. So I'm every happy to be interviewed about BGP on Software Engineering Radio:

Iljitsch van Beijnum, author of the book BGP: Building Reliable Networks with the Border Gateway Protocol discusses internet routing and BGP – the border gateway protocol used by ISPs to update routing information. Host Robert Blumen spoke with Iljitsch about the topology of the internet, autonomous systems (AS), regulatory bodies that coordinate the AS space, IP addresses, the assignment of IPs to ASs; tier-one ISPs, carriers, and home/business ISPs; Internet routing; the path of a packet; routing tables, what they contain, and how they are constructed; routing algorithms; BGP and its role in updating routers with the knowledge of routes held by other routers; and BGP messages. Drill down into the update message. How updates progress from BGP into routing algorithms and then routing tables. What can go wrong. Attacks on BGP.

Permalink - posted 2021-07-13

→ BGP expert test v2.0!

Someone pointed out that the BGP expert test I've had on for a very long time didn't work anymore. I fixed that, and also changed a few questions. So I think I can now call it the BGP expert test v2.0.

Check it out and tell me your score!

Permalink - posted 2021-05-15

The effectiveness of AS path prepending

In a recent blog post The Effectiveness of AS Path Prepending (1) Russ White asks:

Just about everyone prepends AS’ to shift inbound traffic from one provider to another—but does this really work?

(AS path prepending means making the network path as BGP sees it longer to make a path less attractive so traffic will flow over another, shorter path.)

That's an interesting question, as I've been telling people for a long time that it often works too well.

Full article / permalink - posted 2021-05-13

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