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Hi, I'm Iljitsch van Beijnum, writer, freelance network engineer and PhD student. I'm from The Hague. Some of the blog posts here are in Dutch, others are in English. See for just work-related posts.

Apparently, SSL generates IPv4 "too bigs"

Yesterday, I wrote:

❝In almost a week, I received zero IPv4 "too big" messages.

So it seems in the IPv4 world, path MTU discovery is dead.❞

However, João Taveira Araújo told me that he sees a good number of IPv4 ICMP "too big" messages. Those seem to result from SSL traffic. At first, that seemed strange, as SSL is just payload for TCP so TCP MSS clamping should work on SSL sessions the same as on non-SSL sessions.

But then I realized that this traffic could be SSL VPNs. If a VPN gateway takes an IPv4 packet and encapsulates that in SSL in a single TCP segment, then the size of those TCP segments isn't influenced by MSS clamping, so too big messages will be generated if the path MTU is smaller than the MTUs of the endpoints of the SSL connection. I wonder if those SSL VPN implementations handle path MTU discovery properly, though.

Permalink - posted 2014-12-19

Internet packet sizes part 2: IPv4 path MTU discovery is dead

Please read yesterday's post Maximum packet sizes on the internet first. There, I looked at the maximum supported packet sizes that are included in the TCP MSS option in HTTP requests to my server. Today I'll look at the values in ICMP(v6) "too big" messages.

In almost a week, I received zero IPv4 "too big" messages.

So it seems in the IPv4 world, path MTU discovery is dead.

Full article / permalink - posted 2014-12-18

Maximum packet sizes on the internet

After some heated discussions about packet sizes on the mailinglist of the IETF v6ops working group, I decided to do some measurements to find out what maximum packet sizes are supported on today's internet...

Full article / permalink - posted 2014-12-17

Donkere wolken pakken zich samen boven het binnenhof.

Donkere wolken pakken zich samen boven het binnenhof.

Image link - posted 2014-12-17

Connect your iPhone 6 to your Mac for faster charging

I got myself an iPhone 6 last month. Because it has a larger battery than previous iPhones but the iPhone chargers have remained the same since the iPhone 3G days, I was a bit worried about how long it takes to charge the iPhone 6...

Full article / permalink - posted 2014-12-16

Apple Watch: Moore's Law need not apply

Jean-Louis Gassée over at Monday Note has an interesting article talking about how cameras used to last for decades back in the analog days, while they're obsolete within a year or two now that they're digital. And how the same thing is about to happen to the watch: an old mechanical watch will keep doing its thing for decades (I'm assuming some upkeep here), but not so much for an Apple Watch:

❝There’s no carrier subsidy for the AppleWatch. That could be a problem when Moore’s Law makes the $5K high-end model obsolete.❞

I'm not so sure Moore's Law is going to make the Apple Watch obsolete within just a few years.

Full article / permalink - posted 2014-12-08

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