Brandon's Weekly Learning Journal

 Week 8 This is a short week and didn't cover as much material as the previous weeks, however it is still very important as it protects your device from... well... bad people. This is an addition to module 4's material on network security, though this is more related to protection against unwanted connections.  One of the main protections of your network is the firewall. The firewall filters packets and depending on the packets source IP, destination IP, TCP/UDP source/destination, and other messages/bits, the firewall can either forward or drop packets. What makes this important is it prevents denial of service attacks and illegal modification or access of internal data. Only authenticated users/hosts are allowed to send packets through. However, there are limitations, if someone spoofs their IP, the firewall can't truly know if the data really came from that IP. And each application would require special treatment to be allowed to make connections. So, one protection agai...

 Week 7 This week covered the link layer of the internet. The last two weeks involved the network layer which centered around routing algorithms using IP addresses to send and receive data. The link layer is what takes the IP address and determines how to get from interface to interface in each router/host link using a MAC address. Each host and router have a LAN table including IP/MAC address mappings. However, they don't know each other's MAC addresses initially, which is where the address resolution protocol (ARP) comes to play. Using ARP, a host or router can send a broadcast looking for a specific MAC address using a known IP address. This broadcast floods other switches and routers until the host with the IP address sees the broadcast and replies with it's MAC address, which then is cached in the initial host's ARP table. There is much more to this, but I must keep this brief. The link layer offers other services besides delivery between adjacent nodes, though one...

 Week 6, This week's material covered quite a bit of material in the network layer's control plane. This involves how routing is handled. Without it, you wouldn't be able to communicate with hosts outside your local network and without its different algorithms, the speed at which your messages travel would be significantly shorter. To summarize, there are two approaches to structuring the network control plane, using per-router control and logically centralized control.  Logically centralized control use link state algorithms such as Dijkstra's algorithm to compute the least cost paths from one node to all other nodes. The net topology and link costs are known to all nodes so they can determine which is the fastest way for data to be sent from one node to another. On the other hand, per-router control the distance vector algorithm where each node only knows the distance to its directly connected neighbor and sends a list to its neighbors with the current distances to al...

 Week 5 This week, we delved into the network layer of the internet. The network layer is what transports segments from sending to the receiving host. The sender encapsulates the transport layer segments into datagrams, which routers can use to deliver it to the receiver. Two important functions of the network layer are forwarding and routing, where routing determines the route taken by packets form source to destination, and forwarding is where each router moves a packet from the input to the appropriate output.  You can consider there are two planes in the network layer. The data plane, which is where the per-router functions occur, such as forwarding, and the control plane, which is network wide, such as routing. A lot of what happens in the network plane is handled by routers, which is where the forwarding takes place, and uses forwarding tables to do so. However, this cannot be possible without the Internet Protocol. There are two formats, IPv4 which uses a 32-bit identif...