CST 311 - Week 1

 Week 0 and Week 1 of the course were about setting up the software we will use, VirtualBox, Mininet, and Wireshark, and the first topics studied were Computer Networks and the Internet.

In this course, we are running a Mininet virtual machine through VirtualBox.  Mininet is a computer network simulation that can be configured to run virtual hosts, switches, and controllers.  I am ssh'ing into the locally hosted VM to connect to the virtual machine using my MacOS built-in terminal.  We will also use Wireshark, a packet sniffing software, to monitor traffic on the network.

The first topic studied in week one was what is the internet.  It is composed of end systems, the billions of devices connected together such as laptops, PC, phones, and smart home devices, the communication links such as fiber or radio, and the packet switches such as routers and switches.  It is also run by several protocols such as TCP, 802.11, and IPV4.  These protocols define the format and the action to take on packet transmission.  The network has a network core which is made up of interconnected routers which is referred to as a network of networks, and the network edge with is made up of everything else such as end devices, hosts, and servers.

The two most common access networks, or a network that connects end devices with other end devices, are DLS (Digital Subscriber Line) and Cabel.  DLS is a service that uses existing phone lines to transmit data.  The telephone company then splits the data signal and voice signal at the central office but it needs to be within 5 to 10 miles.  Cable on the other hand uses the existing coax cables to transmit the data.  Cable will run at similar speeds but is prone to issues that can arrive from shared bandwidth because it can be shared with up to 500 different homes/apartments.

Data transmission also experiences delay, loss, and throughput.  The total delay of a packet can be calculated by totaling the queueing delay, the time it takes for the router to transmit packets from its buffer, the transmission delay, the time it takes to send out the packet from the router, and the propagation delay, the time it takes the packets to travel the physical link between destinations.  These physical links can be guided media or unguided media.  Guided media, as it sounds, is a signal transmission in a solid media such as copper, coax, or fiber.  Unguided media on the other hand are signals such as radio either terestrial or satellite.

Our first assignment was to have a server and client respond to requests using socket programming.  This was done in Python where we used two different types of socket transport services called UDP and TCP.  In UDP transport there is no "connection" between the client and server, or there is no handshake before communication.  This makes UDP an unreliable datagram because data can be lost or miss organized.  In TCP transport the client and server communicate before data is sent to ensure that the server is ready to listen to the client.  This is more reliable because it is flow controlled.  Both UDP and TCP are in the transport layer of the Internet protocol stack.  The Internet protocol stack consists of layers physical, link, network, transport, and application.