CS Online Learning Journal

  Week 8 – CST– 311 Intro to Computer Networks Module 8 – Security in Computer Networks In this short week 8, we continued with security in computer networks, specifically, firewalls and intrusion detection systems. Firewalls are a combination of hardware and software which separate an organization’s network from the rest of the internet. A system administrator implements a firewall to accomplish three goals. The first goal is that all traffic from outside to inside and vice versa must pass through the firewall. This can be accomplished by placing the firewall at the boundary between the organization’s network and the rest of the internet. It is also easier to manage access when locating a firewall at a single access point to the network. The second goal allows access only to authorized traffic. If all traffic is coming and going through the firewall, it can restrict access to unauthorized traffic. Lastly, the third goal is for a firewall to be immune to penetration. For this...

Week 7– CST– 311 Intro to Computer Networks Module 7 – The Link Layer and LANs This week we covered the link layer and LANs. In section 6.2 we studied the many simple error-detection and error-correction techniques that are used in practice in the link layer. Some of these techniques include parity checking, internet checksum, and cyclic redundancy check. With parity checking, the sender includes a parity bid with the data sent. In an even parity scheme, the total number of 1s in the d + 1 bits is even. With odd parity schemes, the parity bit makes an odd number of 1s. If the receiver finds an odd number of 1-valued bits with an even parity scheme, then they know that at least 1 bit error has occurred. There is also a two-dimensional parity error technique that can help identify and correct the corrupted bit. The internet checksum can be implemented by summing 16-bit integers. Then the 1s complement of the sum is used as the internet checksum and send in the header segment. The r...

  Week 6– CST– 311 Intro to Computer Networks Module 6 – The Network Layer- Control Plane This week we learned about the second part of the Network Layer, the control plane. The control plane is where routing takes place. There are two ways of structuring the control plane, pre-router control and logically centralized control. With pre-router control, each router has its own routing algorithm, and they interact with each other to create forwarding tables. In logically centralized control, a controller interacts with local agents and computes the forwarding tables for the routers. In section 5.2 we covered routing algorithms. There are centralized routing algorithms, which compute the least-cost path from source to destination using full knowledge of the network. These algorithms are called link-state or LS algorithms because the algorithms are aware of the cost of each link in the network. Dijkstra’s algorithm is an algorithm that computes the least-cost path from one node to...