Introduction to Computer Networking

Study Notes

The text provides an introduction to computer networking.
The slides are freely available for use by instructors, students, and readers.
Users are asked to provide attribution to the authors and copyright when reusing or posting the slides on a website.
The slides are in PowerPoint format, allowing for customization, including animations, and modifications.

The Internet is a network of networks consisting of interconnected ISPs.
Protocols are used to govern the sending and receiving of messages.
Examples of protocols include TCP, IP, HTTP, Skype, and 802.11.
Standards, such as RFCs (Request for Comments) and IETF (Internet Engineering Task Force), define the protocols and their use.

The network edge includes hosts (clients and servers), often located in data centers.
Access networks consist of physical media such as wired or wireless communication links.
The network core is made up of interconnected routers and forms a network of networks.

Residential, institutional, and company networks use various access technologies.
DSL (Digital Subscriber Line) uses existing telephone lines to transmit data.
Cable networks use frequency division multiplexing (FDM) to share transmission bandwidth.
HFC (Hybrid Fiber Coax) combines fiber optic cable and coaxial cable for improved performance.
Home networks often combine wireless access points with wired Ethernet for flexibility.
Enterprise networks (Ethernet) typically use Ethernet switches to connect devices within companies or universities.
Wireless networks use base stations or access points for connection via radio waves.

Protocols define the format and order of messages sent and received among network entities.
Protocols also define the actions taken when a message is sent or received.
Everyday examples of human protocols include greetings, conversations, or schedules.

Hosts send data in packets for transmission.
Packets are broken into smaller chunks called packets.
Packets are transmitted at a specific transmission rate, also known as bandwidth.
Transmission delay is the time needed to transmit a packet into a link based on the link capacity (R) and the length of the packet (L). The delay is calculated as the length of the packet divided by the transmission rate.
Propagation delay is the time the signal takes to travel across a link which is based on the length of the link and the speed of propagation in the medium.

Transmission delay is the time to transmit all bits of a packet on a link.
Propagation delay is the time for a bit to travel from source to destination of a link.
Processing delay is the time required to process headers and determine output links in a router.
Queuing delay is the time a packet waits at a router's output link, waiting for transmission.
Overall nodal delay is calculated as the sum of transmission, propagation, processing, and queuing delay.

Packets are dropped when the queue in a router's buffer is full.
Routers drop packets when the arrival rate of packets exceeds the link capacity.

Traceroute is a program that measures the delay between two points on the internet.
Traceroute sends packets to various routers that reflect back to determine the path.

A throughput is the rate at which bits are transferred between sender and receiver.
Instantaneous throughput is the rate at a given point in time.
Average throughput is the rate over a longer period.
The bottleneck link will constrain the throughput of the network path.