Introduction to Computer Networking

Computer Networking is a "network of networks" consisting of interconnected Internet Service Providers (ISPs).
Protocols control message sending and receiving, like TCP, IP, HTTP, Skype, and 802.11.
Internet standards are defined within RFCs (Requests for Comments) and managed by the IETF (Internet Engineering Task Force).
The Internet provides services to applications like Web, VoIP, email, social networking, and e-commerce, similar to a postal service.

The network edge consists of clients and servers, often in data centers.
Access networks are the physical connections (wired or wireless) that connect devices to the edge router.
The network core is composed of interconnected routers, functioning as a network of networks.

Access networks connect end systems to the edge router, in various forms like residential, institutional, or mobile networks.
Bandwidth (bits per second) of access networks can be shared or dedicated.
Examples of access networks include DSL (Digital Subscriber Line), cable networks, and home networks (using wireless access points or Ethernet).

Guided Media transmit signals in solid mediums like copper wire, fiber optic cables, or coaxial cable. Key characteristics of guided media like twisted-pair, category 5, and category 6 are discussed, and examples include broadband over coaxial cable
Unguided Media transmit signals freely, such as radio waves. Terrestrial microwave, cellular, and satellite systems are examples of unguided media.

Protocols define the format and sequence of messages among entities in a network, governing how devices communicate.
Human and network protocols are distinct. Computer networks rely on precise protocols to ensure successful communication.

Packet loss occurs when an arriving packet to a full buffer is dropped due to limited queue (buffer) capacity.
Four sources of packet delay are transmission, nodal processing, queueing, and propagation. Time needed to transmit a L-bit packet over a link with rate R is L/R seconds.
Transmission delay is the time to transmit all bits of a packet at the transmitter rate, and propagation delay is the time for a bit to travel from the transmitter to the receiver.

Throughput is the rate at which bits are transferred between the sender and receiver, measured as instantaneous or average over a longer period.
The bottleneck link along the path constrains the end-to-end throughput of a network.

Traceroute is a program that measures the delay/loss from a source to a destination, providing path information along the way.
It analyzes the network's route by sending packets and timing their response from each router encountered.