Networking Fundamentals, Chapter 1

• Chapter 1 introduces fundamental networking concepts and terminology.

Overview/Roadmap

• The chapter explains the Internet protocols, layers, structure, performance, security, and history.

The Internet: Nuts and Bolts View

• The Internet connects billions of computing devices, including hosts and end systems at the network edge.
• Packet switches forward data in chunks and include routers and switches.
• Communication links use fiber, copper, radio, and satellite, with transmission rate defined by bandwidth.
• Networks are a collection of devices, routers, and links managed by an organization.

The Internet: Network of Networks

• The Internet is a network of networks formed by interconnected ISPs.
• Protocols are essential for controlling the sending and receiving of messages.
• Internet standards include RFC: Request for Comments and IETF: Internet Engineering Task Force.

The Internet: Services View

• The Internet provides Infrastructure services to applications, enabling web browsing, video streaming, multimedia teleconferencing, email, games, e-commerce, social media, and interconnected appliances.
• It provides a programming interface with hooks for apps to connect and use Internet transport services.
• Offered service options are analogous to postal service options.

Protocols

• Human protocols involve questions, introductions, and agreement on timing.
• Network protocols govern all communication activity between devices on the Internet.
• Protocols define the format, order, and actions taken on messages during transmission and receipt.

Network Edge

• Network edge consists of hosts (clients and servers)
• Servers often reside in data centers.

Access Networks and Physical Media

• Access networks connect end systems to edge routers via residential access nets, institutional access networks (school, company), and mobile access networks (WiFi, 4G/5G).

Cable-Based Access Networks

• Networks transmit data and TV over shared cable.
• HFC (hybrid fiber coax) provides asymmetric transmission rates: downloads at 40 Mbps – 1.2 Gbps and uploads at 30-100 Mbps.
• Cable and fiber networks attach homes to an ISP router where homes share access to the cable headend.
• Frequency division multiplexing (FDM) transmits channels in different frequency bands.

Digital Subscriber Line (DSL) Access Networks

• Existing telephone lines are used to connect to the central office DSLAM.
• DSL carries data to the Internet, while voice goes to the telephone network.
• 24-52 Mbps dedicated downstream and 3.5-16 Mbps dedicated upstream transmission rates.

Home Networks

• Home networks utilize wireless and wired devices combined in a single box that connects to the central office/headend.
• They have WiFi wireless access points (54, 450 Mbps), cable or DSL modem, router, firewall, NAT, and wired Ethernet (1 Gbps).

Wireless Access Networks

• Shared wireless access networks connect end systems to the router through an access point.
• Wireless local area networks (WLANs) are typically short-range, using 802.11b/g/n (WiFi) with 11, 54, and 450 Mbps transmission rates.
• Wide-area cellular access networks are provided by mobile operators (10's km range), with 10's Mbps via 4G/5G.

Enterprise and Data Center Networks

• Enterprise networks are used by companies and universities with mixes of wired and wireless technologies.
• Ethernet provides wired connections at 100Mbps, 1Gbps, and 10Gbps, while WiFi offers wireless access points at 11, 54, and 450 Mbps.
• Data center networks are high-bandwidth links (10s-100s Gbps) connect thousands of servers.

Host Sending Packets of Data

• Hosts break applications into smaller chunks called packets and transmit them into the access network at transmission rate R.
• The packet transmission delay equals the time needed to transmit L-bit packet into the link

Physical Media

• Physical links lie between the transmitter and receiver.
• Guided media propagates signals through solid media like copper, fiber, and coax.
• Unguided media propagate signals freely, such as with radio.

Link Types

• Twisted pair (TP) uses two insulated copper wires for 100 Mbps to 10Gbps Ethernet connections.
• Coaxial cable has two concentric copper conductors and is bidirectional and broadband, supporting multiple frequency channels at 100’s Mbps per channel.
• Fiber optic cable transmits light pulses through glass fiber. It has high-speed point-to-point transmission (10's-100's Gbps) and low error rates, and is immune to electromagnetic noise.
• Wireless radio uses various bands in spectrum
• Wide-area wireless (4G/5G cellular) provides 10's Mbps over ~10 km.

Network Core

• The network core interconnected routers and enables packet-switching
• Networks forward packets along the path from source to destination.

Key Network-Core Functions

• Forwarding (switching) moves packets from a router's input link to an output link, being a local action.
• Routing determines the global source-destination paths taken by packets using routing algorithms.

Packet Switching

• Packet transmission delay refers to the time it takes to push an L-bit packet into a link with the bit rate R.
• Store and forward ensures the entire packet arrives at the router before being transmitted on the next link.

Packet Switching: Queueing

• Packet queueing occurs when the arrival rate exceeds the transmission rate.
• Packet queuing can result in loss if the buffer fills up.

Circuit Switching

• Resources are dedicated end-to-end, not shared when using circuit switching.
• Circuit switching is used in traditional telephone networks

Circuit Switching: FDM and TDM

• Frequency Division Multiplexing (FDM) divides the spectrum of optical and electromagnetic frequencies.
• Time Division Multiplexing (TDM) divides time into slots.

Packet Switching versus Circuit switching

• Packet-switching is great for bursty data as it allows resource sharing.
• The two limitations of packet switching is that their can be excessive congestion, and it requires protocols to have reliable data transfer and congestion control.

Internet Structure

• Hosts connect to the Internet via access ISPs, which need to be interconnected.
• The resulting interconnectedness is complex and influenced by economics and national policies, leading to a need for a structured approach to understanding.

Internet Structure: Key Components

• Global transit ISPs connect with regional networks and have Internet exchange points.
• Content provider networks create services to reduce the load on the internet.
• Tier-1 ISPs are composed of commercial ISPs which provide national and international coverage.

Network Performance: Packet Delay and Loss

• Packet delay occurs within router buffers while packets wait for transmission.
• Delay increases when arrival rate exceeds output link capacity.

Packet Delay: Four Sources

• Nodal processing (dproc): check bit errors, determine output link.
• Queueing delay (dqueue): time waiting at output link for transmission.
• Transmission delay (dtrans): equals packet length over the link transmission rate.
• Propagation delay (dprop): distance over propagation speed.

Packet Queueing Delay

• If the arrival rate to a link exceeds the transmission rate for sometime, packets must wait.
• If the memory buffer in a router fills up then, packets can be dropped (lost)

Real Internet Delays and routes

• Traceroute measures the end-end Internet delay to a router along a path which uses 3 packets to discover delay measurement.

Packet Loss

• Packets are dropped then the queue (aka buffer) becomes full to its capacity.
• A packet may not be retransmitted by its source node.

Throughput

• Throughput is the rate that bits are sent from sender to receiver.
• Bottleneck link constrains end-to-end throughput.
• Per-connection end-end throughput is calculated based on the bottleneck and the number of clients.

Network Security

• The Internet was originally designed without security in mind, necessitating security at all layers.
• Security considerations include bad computer attacks, defending networks against attacks, and the architecture design that is immune to attacks.

Security Problems

• Packet sniffing consists of illicit packet reading, which can harvest passwords.
• IP spoofing consists of injecting packets with a false source address.
• Denial of Service(DoS) consists of compromising hosts through the use of botnets, from which illegitimate bogus traffic is sent from.

Lines of Defence for Network Security

• Authentication can be accomplished prove individuals are who they say via Cellular Networks.
• Encryption helps with confidentiality.
• Firewalls acts as specialized middleboxes that filer access.

Protocol Layers and Service Models

• Protocol layering helps organize complex networks by dividing them into hosts, routers, links of various media, applications, protocols, and hardware/software.
• The Internet protocol stack consists of application, transport, network, link, and physical layers.

Layer operation

• Application layer messages exchange to implement applications using services of transport layer
• Transport layer protocol transfers a message from one process to another and encapsulates it
• Network Layer encapsulates with layer header and transfers
• This repeats until the destination is reached

History of Internet

• 1961-1972 was the early packet switching principles.
• 1972 consists of initial public presentation of ARPANet.
• 1972-1980 was the beginning of internetworking.
• 1974, a new IP architecture was born.
• 1980-1990 involved prolific production of new protocols and networks
• 1990 - Present Day involved commericalization.
• In 2005, there was a rise in mobile devices.