Russell's Learning Journal

 This week the topic of discussion was the Network Layer that consists of a data plane and a control plane.  What's inside a router/how do they function, Internet Protocol and the different versions, and generalized forwarding and software-defined networking (SDN) were other topics studied. The data plane handles the forwarding function, or moving packets from router inputs to router outputs, which determines how to get a packet from the input port to the output port.  This is also a local function that happens on every router.  The control plane provides the routing functions, or finding the route taken by the packets from the source to the destination.  This is a network-wide function because all routers need to communicate with each other to determine the correct end-to-end path. The router architecture consists of input/output ports, high-speed switching fabric, and the router processor.  The forwarding function happens in hardware in the high-speed swi...

 This week the topic studied was the Transport Layer.  The topics included in the transport layer were multiplexing/demultiplexing, UDP, TCP, connection management, and congestion control.  Multiplexing happens at the sender to handle data being sent from multiple sockets (app sent messages to sockets).  It adds a transport header that will later be used by the receiver in demultiplexing.  Demultiplexing happens at the receiver.  When an IP datagram is received it contains a source IP and destination IP.  Each datagram will also carry one segment that has a header with two fields, source port number, and destination port number.  The port numbers are used to direct the segment to the correct socket with that port number to then be sent to the appropriate application.  This process is used for UDP.  In TCP the demultiplexing part will use a 4-tuple to direct the segment to the correct socket. UDP is a connectionless, no-frills, bare-bones...

Studied this week was the application layer.  It covered topics of network applications, Web and HTTP, electronic mail, and DNS.  Network applications can be e-mail, text messaging, VOIP remote login, peer-to-peer file sharing, video streaming, etc.  There are two types of application architectures, client-server and peer-to-peer.  Sockets are used to send/receive processes to/from the client and server.  Two types of protocols are used at the app layer which are open protocols such as HTTP and proprietary protocols such as Skype. HTTP is the Web's application layer protocol that uses the client-server model.  HTTP uses TCP to connect to a socketed server through port 80 and can either be persistent or non-persistent.  There are two types of HTTP messages, a request message, and a response message.  Cookies are used to assist in maintaining an HTTP state.  Cookies are helpful in situations of authorization, shopping cart updates, recommendati...

 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...