CST 311 --- Week 8

Alas, the final week of the course, you have been a good one, I cannot deny.

This week we learned about Operational Security: Firewalls and Intrusion Detection Systems.

When traffic entering/leaving a network is security-checked, logged, or dropped, or forwarded it is done by operational devices known as firewalls, intrusion detection systems(IDSs) and intrusion prevention systems(IPSs). A firewall is a combination of hardware and software that isolates an organization's internal network from the Internet at large, allowing some packets to pass and blocking others. 

A network administrator controls access between the outside world and resources within the administered network by managing the traffic flow to and from these resources, via a Firewall. 

There are 3 main goals to a Firewall: 

1)All traffic from outside to inside, and vice versa, passes through the firewall.

2)Only authorized traffic, as defined by the local security policy, will be allowed to pass.

3)The firewall itself is immune to penetration.

An illustration as to how Firewalls work:

-From the Kurose Networking Textbook.

There was a bit more to learn from this part of the textbook, but I'll keep it short and simple for now. 

Overall, from this class I learned invaluable tools that will help me in the future leading to become a Full Stack Software Engineer. The valuable insights gained will equip me to become fully fleshed as a reliable professional in the industry. It was nice knowing ya, CST 311, and I look forward to put my learnings into practice. Best to you all. 

CST 311 - Week 7

Now that we are at the final steps of the course, I am fully satisfied with my performance in the course and how much I have learned. 

This week we learned about the Link Layer. Its role is to serve as a communication channel that directly connects physically adjacent nodes: links. It has a layer-2 packet: frame, that encapsulates the datagram. The Link layer has the responsibility of transferring datagram from one node to physically adjacent node over a link. 

Overall, the link layer facilitates the communication between the devices on the same local network. Its primary responsibilities include framing data into packets, addressing, and error detection. This layer is also responsible for defining how data is transmitted over the physical medium, such as Ethernet cables or wireless connections. It ensures that information is reliably and efficiently transferred between devices within the same network segment, typically using MAC(Media Access Control) addresses to identify hardware on the network. 

The link layer plays the vital role of bridging the gap between the physical layer and the higher-level network layers. 

I also very much enjoyed the lab working with multiple hosts and the POX controller. At last, one half week left of the course, it shall be missed. On to the next one!

CST 311 - Week 6

 I learned much in this week about the Network layer. As much as I would love to go in much detail, I will keep this simple for the sake of efficiency.

The control-plane component of the network layer is the network-wide logic that controls not only how a datagram is routed along an end-to-end path from the source host to the destination host, but also how network-layer components and services are configured and managed. 

There are 2 internet routing protocols: OSPF and BGP. BGP is often referred to as the glue that hold the Internet together. 

Here are some photos that illustrate routing algorithms in the control plane: 

The goal of routing algorithms is to determine good path from senders to receivers through the network of routers. A "good" path is typically the one with the least cost. Graphs are used to formulate routing problems.

I also learned of the Link-State (LS) Routing Algorithm, Link-State Broadcast, Dijkstra's algorithm, the Distance-Vector (DV) Routing Algorithm and much, much more!

This week's lab was very interesting as well, and I got a sneak peak into how OpenFlow rules in an OpenFlow switch works. I look forward to finishing the rest of this semester in this Networking course with a bang. 

Until Next Time.

CST 311 - WEEK 5

This week we delved deeper into learning about the Network Layer. The primary role of the network control plane is to coordinate the local, per router actions so that datagrams are ultimately transferred end-to-end, along paths of routers between source and destination hosts. 

So, again, the primary role of the network layer is to move packets from a sending host to a receiving host. The two important network-layer functions are:

1) Forwarding. When a packet arrives at a router's input link, the router must move the packet to the appropriate output link. 

2)Routing. The network layer must determine the route or path taken by packets as they flow from a sender to a receiver. (The algorithms that calculate these paths are referred to as routing algorithms.)

A key element in every network router is its forwarding table. A router forwards a packet by examining the value of one or more fields in the arriving packet's header, and then using these header values to index into its forwarding table. 

The two photos below show the purpose of forwarding tables: 

I learned a bunch more in this week's textbook readings from the network service model, to learning on what's inside a router, input port processing, and destination-based forwarding, switching, where queueing occurs, packet scheduling, IPv4 and IPv6, and much more. 

Overall, this week went well especially finishing up PA#3 and doing this week's labs and assignments. I look forward to ending the course well and studying hard!

Until next time~