donatas abraitis

sendfile() and TLS

Every skilled sysadmin knows about sendfile() syscall.

Read More

Running QuakeWorld under OSX

Already 15 years passed when I played QuakeWorld and I feel too much nostalgic remembering those days. QuakeWorld (aka. Quake1) was released in 1996. It celebrates 21 this year and I tried to go back to 2002-2008 (it was the time I played QW quite professional). I must say, that well-known players such like Milton, Locktar are still on the track.

Read More

Limit bandwidth by Openresty

Nginx has two cool features to limit bandwidth for responses:

Read More

Measure TCP metrics LD_PRELOAD-ish way

Why LD_PRELOAD?

Read More

::1/128 enlarge to not to enlarge?

IPv4 has by design 127.0.0.0/8 delegated for loopback usage. It means that you can use ~16M addresses to identify hosts inside your fleet. I’ve touched this usage in networking world, but who else really needs this behavior while we are living in 2017 (containers world)? To be honestly, I’m talking about ancient IPv4 protocol.

Read More

$Cisco high CPU usage with RPKI enabled validation

I don’t know how much of ISPs are now using RPKI based validation for BGP prefixes to avoid hijacking attacks, but a few years ago most of the ISPs still used old-school method (prefix/ACL lists) to filter “good” and “bad” prefixes from neighbors. I remember when I was working on ISP we dealt with this problem as well.

Read More

Overwhelmed security for scaredy-cats

Yesterday I read ip(7). While reading I found IP_TTL and remembered such a nice feature almost every vendor has for BGP security called BGP ttl-security check.

Read More

Traffic engineering with SR-IPv6

I have always been interested in traffic engineering (TE) since I started my career in ISPs. In my career, I worked in various size of ISPs. The first was Litnet, later I joined Kauno Interneto Sistemos and the last station was Cgates. Most interesting and challenging tasks were how to steer the traffic by various conditions: latency, shortest path, clients’ needs and so on and so forth. Back to TE, I always wondered how to steer the internal traffic with minimal effort (without introducing MPLS-TE), those days were not so good as today.

Read More

Best souvenir ever

0.0.0.0/0

Read More

Handling quota notifications using netlink sockets

Do you have a project which requires quotas must be implemented correctly? What about notifying clients when they reach the limits? No.. I asked what about real-time notifications?

Read More