MTU and TCP MSS clamping

So I have had many conversation over the years in regards of that is MTU and how does it work and what is the relationship between frame/packet/datagram sizes. Despite the fact that this is actually fairly simple there seems to be a lot of confusion on this topic so that is why this article come about. read more

How to test IPv6 with iperf

Lately there has been yet again a big surge of interest in IPv6 and I did find to my surprise that even thought IPerf supports IPv6 for quite some time no-one actually has written how to actually do this rather trivial test.
First thing about IPv6 is that your interface on the end-point PCs will auto-assign a link-local address to itself. The link local address is in fe80::macaddress format (where one bit of the mac address can be changed depending on the implementation). So this looks fine – no problems. You should be able to ping between those ip addresses using ipv6 ping riight? Lets try to ping localhost’s ipv6 link-local address. In order to do this you need to specify the interface you are using as ping can’t lookup the address automatically as it can with IPv4. read more

PackEth tutorial part II – The Gen-B,Gen-S and PCAP options

This is a Second part of an article I have written some time ago about the great tool called PackETH.  This article will be much shorted as it will be focused on the less complicated (but not useful!) modes of the tool.

In the previous par I have described how to build your own packet from L2 to L4 but what if you need something else ? maybe not a single packet but a burst of packets? or what is you need to send multiple streams of various frames ? Well then you need to use the Gen-S and Gen-B modes. read more

PackEth tutorial part I – The Interface and The Packet Builder

In one of my previous posts I have mentioned great piece of software called PackEth and I have also promised that will write up a separate article about it as I just think this amazing tool deserves as much attention as I can give it.  So what does this software do?  Well let me quote the author ” PackETH is GUI and CLI packet generator tool for Ethernet…It allows you to create and send any possible packet or sequence of packets on the Ethernet link.” I would add that that it is the only tool I have found that actually allows you to assemble Ethernet frames and a IP packets that actually does what you would expect it to do while being multi-platform and incredibly stable. I think I have never seen it crashing which speaks for itself.  This article will focus around version 1.6 as that is the one that has both Linux and Windows versions available. The drawback is that at the time of writing the L3 IPv6 support is not included. read more