I am using the WHOIS client a lot these days since I am migrating some RIPE objects such as ASes, inetnum/inet6num, etc. Meanwhile, I recognized that I have never captured this TCP port 43 protocol, nor looked at it with Wireshark. That’s what this post is all about, incl. a downloadable pcap for your own analysis.
VoIP calls, using the network protocols SIP/SDP and RTP, are the de-facto standard when it comes to voice calls. Wireshark offers some special features to analyze those calls and RTP streams – even with a nice “Play Streams” option, which discretely decodes your calls. Ouch. Again and again, frightening which privacy-related protocols are completely unencrypted on the Internet!
Here are some hints for Wireshark as well as a downloadable pcap with three calls in there. ;) Have fun!
Some time ago I published a post called DNS Test Names & Resource Records which lists many different FQDNs with lots of different RRs. You can use those public available DNS names to test your DNS servers or the like. However, I was missing a packet capture showing all these resource records as they appear on the wire. So now, here it is. If you are searching for some packets to test your tools for whatever reason, feel free to download this pcap.
If you’re into DNSSEC, you’ll probably have to troubleshoot or at least to verify it. While there are some good online tools such as DNSViz, there is also a command-line tool to test DNSSEC signatures onsite: delv.
As you might have noticed, I am playing a lot with NTP these days. Having a networking background I also like Power over Ethernet. So what’s more obvious than using a PoE-powered NTP display for test purposes? ;D
Probably the biggest prejudice when it comes to IPv6 is: “I don’t like those long addresses – they are hard to remember.” While this seems to be obvious due to the length and hexadecimal presentation of v6 addresses, it is NOT true. In the end, you’ll love IPv6 addresses in your own networks. This is why – summed up in one poster:
I am currently working on a network & security training, module “OSI Layer 4 – Transport”. Therefore I made a very basic demo of a TCP and UDP connection in order to see the common “SYN, SYN-ACK, ACK” for TCP while none of them for UDP, “Follow TCP/UDP Stream” in Wireshark, and so on. I wanted to show that it’s not that complicated at all. Every common application/service simply uses these data streams to transfer data aka bytes between a client and a server.
That is: Here are the Linux commands for basic lab, a downloadable pcap, and, as always, some Wireshark screenshots:
During my analysis of NTP and its traffic to my NTP servers listed in the NTP Pool Project I discovered many ICMP error messages coming back to my servers such as port unreachables, address unreachables, time exceeded or administratively prohibited. Strange. In summary, more than 3 % of IPv6-enabled NTP clients failed in getting answers from my servers. Let’s have a closer look:
I am participating in the NTP Pool Project with at least one NTP server at a time. Of course, I am monitoring the count of NTP clients that are accessing my servers with some RRDtool graphs. ;) I was totally surprised that I got quite high peaks for a couple of minutes whenever one of the servers was in the DNS while the overall rate did grow really slowly. I am still not quite sure why this is the case.
For one month I also logged all source IP addresses to gain some more details about its usage. Let’s have a look at some stats:
You have a running NTP server with a static IP address? What about joining the NTP Pool project by adding your server to the pool? You will give something back to the Internet community and feel good about it. ;)
It doesn’t matter if you’re running a Raspberry Pi with GPS/DCF77 on your home, or a fully-featured NTP appliance such as the ones from Meinberg on your enterprise DMZ. Just a few clicks and your server will be used by the NTP Pool’s round-robin DNS. Here’s a simple tutorial:
If you are operating a public available NTP server, for example when you’re going to join the NTP Pool Project, you probably want to test whether your server is working correctly. Either with a one-off measurement from hundreds of clients or continuously to keep track of its performance. You can use the RIPE Atlas measurement platform (Wikipedia) for both use cases. Here’s how:
Monitoring a Meinberg LANTIME appliance is much easier than monitoring DIY NTP servers. Why? Because you can use the provided enterprise MIB and load it into your SNMP-based monitoring system. Great. The MIB serves many OIDs such as the firmware version, reference clock state, offset, client requests, and even more specific ones such as “correlation” and “field strength” in case of my phase-modulated DCF77 receiver (which is called “PZF” by Meinberg). And since the LANTIME is built upon Linux, you can use the well-known system and interfaces MIBs as well for basic coverage. Let’s dig into it:
Beyond monitoring Linux OS and basic NTP statistics of your stratum 1 GPS NTP server, you can get some more values from the GPS receiver itself, namely the number of satellites (active & in view) as well as the GPS fix and dilution of precision aka DOP. This brings a few more graphs and details. Nice. Let’s go:
Now that you’re monitoring the Linux operating system as well as the NTP server basics, it’s interesting to have a look at some more details about the DCF77 receiver. Honestly, there is only one more variable that gives a few details, namely the Clock Status Word and its Event Field. At least you have one more graph in your monitoring system. ;)
Wherever you’re running an NTP server: It is really interesting to see how many clients are using it. Either at home, in your company or worldwide at the NTP Pool Project. The problem is that ntp itself does not give you this answer of how many clients it serves. There are the “monstats” and “mrulist” queries but they are not reliable at all since they are not made for this. Hence I had to take another path in order to count NTP clients for my stratum 1 NTP servers. Let’s dig in: