Enterprise Networking Week 3

Spring 2021, Mondays 5:30-8:00

February 8

How TCP variants differ

The only issue is in how the window size, cwnd, is managed. In most cases, the sender determines cwnd, with no support from the receiver.

If cwnd is too high, fairness suffers. This is true generally, and also in specific cases of AIMD(2,0.5) vs AIMD(1,0.5)

If cwnd is too low, available bandwidth is underutilized.

More TCP variants

See http://intronetworks.cs.luc.edu/current2/html/newtcps.html#choosing-a-tcp-on-linux, and the paragraph on using modprobe to add, say, TCP Vegas or BBR TCP.

Mininet

Lubuntu and Mininet 2.3: finally supporting python3!

Simple example of TCP traffic:

h1---s1---h2
h1---r1---h2

Monitoring pings

Monitoring a TCP connection with netcat

Your "assignment" this second week was to use VirtualBox to build a virtual machine using lubuntu.vdi as its virtual disk:

Download and unzip the lubuntu.vdi file. If you don't have enough disk space, you can use a usb drive or even a usb flash drive of at least 16 GB.
Create a new virtual machine with Type = Linux and Version = Ubuntu (64-bit).
Use the option to use an existing disk, namely lubuntu.vdi. Note this is a two-step process: you must first select lubuntu.vdi as a candidate virtual disk, and then assign it to your new virtual machine.
Under the Display settings, set the graphics controller to VBoxSVGA and the video memory to 64 MB. The VMSVGA video option will not work.
Then start it up! It takes ~20 seconds to start, but after it does, you should see a graphical interface.
It should log you in automatically, but for the record the userid and password are both "mininet". To get a "root" shell, use the command sudo bash, for which you will need to enter the "mininet" password.

The link for lubuntu.vdi (or, more precisely, lubuntu.zip) is on Sakai, in the lubuntu.html file in the resources folder. The lubuntu.zip file is 2.5 GB; the unzipped lubuntu.vdi is somewhere between 7 and 8 GB.

Project: compare Reno and Cubic for RTTs from 200 to 1000 ms.

TCP and high bandwidth

Finish TCP Cubic

BBR TCP

Queuing and Scheduling

See intronetworks.cs.luc.edu/current2/html/fairqueuing.html.