Wi-Fi Tethering on Android is a great thing and has totally changed the way we use the mobile Internet today. One thing Android does not do well today at all, however, are bulk uploads over Wi-Fi tethering, especially under bad LTE radio conditions with low throughput. The screenshot above shows how a big file upload … Continue reading TCP Tracing – Part 8 – BBR and Uplink Congestion Avoidance
After the interesting throughput experiences I have made over the last mile, it was time to push the limit a bit and get an idea of how a high speed data transmission between virtual machines looks like that are in different data centers. While most of the public cloud infrastructure I used is located in … Continue reading TCP Tracing – Part 7 – Between Data Centers
With multi gigabit per second Ethernet and wireless interfaces, CPUs are quite challenged by the sheer number of packets that need to be handled. Let’s say a transmission on a (meager) 1 Gbps Ethernet link is well utilized by large file transfers (let’s say 100 MBbytes per second) and a typical maximum segment size (MSS) … Continue reading TCP Tracing – Part 6 – Segmentation Offloading
In part 4 of this series, I’ve compared the TCP behavior of high speed LTE and Wi-Fi to a virtual machine in a dater center over links with round trip delay times of around 25 ms. The results were very insightful but also raised new questions that I will follow up in this post. So … Continue reading TCP Tracing – Part 5 – High Speed Wi-Fi and the Receive Window
In the first part of episode 3 on this topic, I have shown how throughput looks like in a good LTE network in which more than one user was activate at a time. I can’t be sure, but based on typical cellular scenarios, there were probably more than 30 concurrent active users in the cell. … Continue reading TCP Tracing – Part 4 – Comparing LTE and Wi-Fi
In part 1 of this series, I compared how the TCP throughput graphs look like for a VDSL vs. an LTE link in stationary and mobility scenarios. Recently, I’ve been to Belgium for a few days and I was expecting to see pretty much the same LTE throughput behavior as in my home network. But … Continue reading TCP Tracing – Part 3 – Unexpected Fluctuations in Belgium
I’ve been doing quite some tracing on the TCP/IP layer recently and especially at higher speeds over links that support hundreds- to thousands of megabits per second, pcap dump files are getting rather large. Fortunately, both Wireshark and tcpdump offer an option to cut packets after a configurable length. That’s perfect for throughput tracing, as … Continue reading TCP Tracing – Part 2 – Keep PCAP Sizes Reasonable
After the interesting experience of chasing packet loss issues of my fiber router in Paris and learning about different TCP congestion control algorithms in the process, I wondered how TCP handles changing network conditions in wireless networks. After all, especially when on the move, air interface conditions and general load of the cell changes all … Continue reading TCP Tracing – Part 1 – How TCP Reacts to Changing Network Conditions
Back in 2014 I had a post on how to cross compile tcpdump for Android to record all network traffic from cellular and Wifi into files for later analysis for Wireshark. I’ve known for a while that it’s also possible to use adb and tcpdump to pipe all network traffic from the smartphone over USB … Continue reading ADB and tcpdump on Android for Live Wireshark Tracing
After optimizing Firefox HTTP/1.1 settings for slow wireless connections 17 years ago (!) , I pretty much forgot all about it again, because networks became faster and default browser settings and features were adapted for the cellular world. Only recently did I have another look at HTTP, when I noticed that HTTP/2 is now widely … Continue reading Wireshark: Tracing Encrypted HTTP/2 Traffic