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Showing posts from June, 2023

CST 311 - Week 8

 This week, the final week, the topic of study was security.  This includes firewalls as well as intrusion detection systems (IDS)/intrusion protection systems (IPS). Firewalls accomplish two major things.  Those are separating the inside net traffic from the outside net traffic and filter traffic.  It filters the traffic by comparing the packet against a security protocol, set up locally by the network admin, and deciding whether to block or allow the packet through.  The purpose of using a firewall is to prevent DoS attacks, prevent illegal modifying or accessing of internal data, allow authorized access to the outside net, etc. There are three types of firewalls, stateless packet filters, stateful packet filters, and application gateways.  Stateless packet filtering filters packet-by-packet deciding whether to forward it on to the destination or drop the packet based on many criteria.  These include the source/destination IP address, TCP/UDP source/...

CST 311 - Week 7

 The topic of this week's studies was the link layer and LANs (local area networks).  Some of the topics covered were the link layer, error detection, error correction, multiple access links, and switched local area networks. The purpose of the link layer is to detect and correct errors as well as how to allow multiple nodes to share a broadcast channel.  These links can be directly connected through a physical medium or wirelessly.  The link layer also regulates the access to a channel that multiple nodes are trying to send on and supports reliable delivery of frames, flow control, and error detection/correction. The techniques used to detect and correct errors are parity checking and cyclic redundancy checks (CRC).  Parity checking sets the parity bit so that there are an even number of 1's.  At the receiver, it checks for an even number of 1's, and if there is not then an error is detected.  Two-D parity checking is more trusted because it eliminate...

CST 311 - Week 6

Week six topic studied was the network layer: control plane.  The control plane is one of the two functions of the network layer, routing, which determines the route taken by packets from the sender source to the receiver destination.  Determining the "best" path relies on routing protocols and routing algorithms.   A routing protocol's goal is to determine the "good" paths from the sending host to the receiving host through a network of routers.  The term "good" means least cost, fastest, least congested, etc.  Routing algorithms can be global or decentralized, and static or dynamic.  One type of algorithm is called a link-state algorithm where the routers all have a complete topology of the network and know the cost info for each link.  Dijkstra's shortest path algorithm is an example of a link-state algorithm.   To make the internet more scalable, routers are grouped into regions known as autonomous systems (AS).  These AS are sp...