CST311 - Week 1

 

CST311 – Intro to Computer Networks 

In the first week of CST 311 Introduction to Computer Networks, we are introduced to fundamental concepts of network. The first module focuses on introducing the Internet as a network of networks illustrated with examples. We also discussed the Internet protocol stack layers: application layer, transport layer, network layer, link layer, and physical layer.

It was important to start by defining packets as the pre-packaged segment of data transmitted from a source to a destination. A packet is traversed over a route or path using packet switches like routers or link-layer switches. ISPs (Internet Service Providers) deliver the Internet to commercial and residential users using various types of access and physical infrastructure.

The sending and receiving of data packets rely on network protocols that determine the communication standards for network components. The main purpose of the network protocol is to format and arrange the order of data exchanged between devices or any network object for transmission or acknowledgment and receipt. Packet switches use store-and-forward to receive the entire packet first before forwarding any of the received bits to the link. Circuit switching is another method to move data over the link, however, this approach requires reserving the resources like the buffer, bandwidth, and path. Unlike packet switching, the communication network in circuit switching must reserve the transaction rate at a fixed link, making this approach less efficient. An advantage of Circuit switching is the guarantee of delivering data without loss of packets or delays. QoS and tight security make circuit switching more attractive, but it comes at a cost. In the past, many companies, including the ones I worked for, ran circuit-switching voice ISDN to host PBX. Today, fewer and fewer companies depend on circuit switching for their voice needs.

We also explored the delay, loss, and throughput concepts. These are important network constraints found between systems. The common types of network delays we encounter are nodal processing, queuing, transmission, and propagation delays. A processing delay consist of the time needed to inspect the packet header and correct any error if necessary. The queuing delay occurs when the packet waits for the full transmission of other packets in the router. The transmission delay is the time required for a packet to be transmitted expressed in L/R where L is the packet bits, and R is the link transmission rate measured in bits per second. On the other hand, a propagation delay is the time needed for the bit propagation at the start of a link to the destination. The propagation delay is expressed by d/s, where d is the physical distance between the source and destination, and s is the propagation speed. An end-to-end delay is calculated as the sum of delays at each node. Throughput is a very important concept for capacity planning, troubleshooting, and initial network design – not the same as bandwidth (usually the ISP sold rate). It measures the real-time performance of a network by measuring the rate at which the data is transmitted. One item to watch for when designing a network is to choose the right hardware specification that handles the appropriate traffic in an enterprise environment.

Example of hardware datasheet that list hardware specification for branch office, Cisco Meraki MX67