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Definition & Overview

• The Internet constitutes a global computer network that links together billions of devices
• It utilizes both hardware and software, facilitating communication
• The Internet operates as a networking infrastructure, delivering services to applications

Devices & End Systems

• Traditionally, devices connected to the internet included desktops, servers, and workstations
• Now, the types of devices include smartphones, tablets, TVs, and IoT systems
• End systems may be referred to as 'hosts'

Network Components

• End systems connect using communication links and packet switches
• Communication links use coaxial cable, fiber optics, copper wire, or wireless signals
• Transmission speed is measured in bits per second (bps)
• Data is broken into packets, transmitted, and reassembled at the destination

Packet Switching & Routing

• Packet switches send packets through a network
• Routers are used in the network core
• Link-layer switches are used in access networks
• A route/path is the route a packet takes to its destination

Internet as a Transportation Network Analogy

• Packets are like trucks transporting goods
• Communication links are highways
• Packet switches are intersections
• End systems are buildings like factories and warehouses

Internet Service Providers (ISPs)

• ISPs grant Internet access to individuals, businesses, and content providers
• Available access types: DSL, cable, fiber, mobile networks, and WiFi
• Lower-tier ISPs connect by fiber-optic networks to upper-tier ISPs, as well as AT&T, Sprint, and NTT,

Internet Protocols

• Governs the sending and receiving of data
• IP defines packet structure and addressing
• TCP ensures reliable communication
• The Internet's protocol suite is called TCP/IP

Internet Standards

• Ensures interoperability between different networks and systems
• The IETF (Internet Engineering Task Force) develops standards
• RFCs, or "Requests for Comments," outline protocols using technical documents
• Other standards bodies include IEEE 802 (WiFi, Ethernet standards)

Two Views of the Internet

• Nuts-and-bolts view refers to hardware and software elements
• Services view refers to the infrastructure providing application services

Internet as a Service Provider

• Supports email, web browsing, and social networks
• Supports streaming services, online gaming, and video conferencing
• Location-based recommendation systems

Distributed Applications

• Applications involve multiple end/host systems exchanging data
• Internet applications run on end systems, not inside network switches
• Packet switches facilitate data exchange but do not run applications

Developing an Internet Application

• Programs are typically written in Java, C, or Python
• Programs must be able to send data between different end systems
• The Internet is a platform facilitating communication

Socket Interface

• End systems use a socket interface to communicate
• The interface provides the rules for sending data from one program to another

Analogy with Postal Service

• Sending data over the Internet is like sending a letter
• Senders must use postal service rules, like addressing and stamping
• Programs must follow Internet socket rules

Internet Services for Applications

• The Internet provides multiple communication services, much like tracking
• Developers must choose the correct service for their applications

Protocol Definition & Importance

• Protocols are rules governing communication between entities in a network
• Protocols specify message formats, order of exchange, and response to transmission

Human Analogy

• Human communication follows certain rules, like beginning with a greeting
• Misunderstandings can occur from misalignment in communication styles, just like in networks

Example of a Human Protocol

• Asking for the time requires an exchange of greetings before proceeding
• The conversation ends if the conversation is not acknowledged

Another Human Protocol Example: A Classroom Scenario

• A teacher saying "Any questions?"
• A student raises their hand
• The acknowledgement between the student and teacher
• The student asks their question

Network Protocols Definition

• A governing protocol between communication between devices
• Every activity between multiple identities follows a protocol

Protocol Examples

• Data flow controlled by hardware protocols between network interface cards
• Congestion controlled by data transmission rate protocols
• Routing protocols determine the paths for packets

Web Browsing Protocol Example

• A browser sends a request to the web server
• The server gives a reply to the browser
• A request for a webpage is then sent by the browser
• The web server delivers the requested webpage

Key protocol takeaways

• Protocols ensure networks communication properly
• They ensure standardized and seamless exchange
• Understanding protocols is essential to control networks

The Network Edge Introduction

• Explores edge components of a computer network
• Focuses on devices like computers and smartphones
• Moves from the network edge to the network core, covering routing and switching

End Systems (Hosts) on Network Edge

• Internet-connected devices sit at the edge of the network, known as end systems (hosts)
• Examples of devices: laptops, desktops, smartphones, tablets, IOT devices, and servers

Hosts and Applications on Network Edge

• Applications run on end systems; examples include email servers, browsers, email clients, and web servers
• The terms "host" and "end system" can be used equally

Clients Vs. Servers on Network Edge

• Clients are mobile devices, desktop PCs, and user-end machines
• Servers are powerful machines that store and distribute content

Data Centers on Network Edge

• Data storage can be for large scale data and houses many thousands of servers
• Google has many data centers, with some containing over 100,000 servers

Concept of lot on the Network Edge

• A concept where everything is wirelessly connected to the internet
• Includes cars, people, eyewear, sensors on the home, and hospital equipment

IoT Devices on the Network Edge

• Smartphones: geolocation data is tracked to ISPs and applications
• Smartwatches and glasses that upload to the internet are known as Wearables
• Security Systems: Connected thermostats and connected scales
• IoT Toys: A doll that can recognize and respond to speech

Benefits and Concerns of IoT on the Network Edge

• Provides daily automation and convenience
• Improved data collection monitoring
• Attacks could lead to potential threats
• Attacks could manipulate connected devices
• Adoption may be limited by security fears

Access Networks Introduction

• An Access network connected to an end system on another path
• Access networks are used in variable settings: a house, an enterprise, or mobile

DSL (Digital Subscriber Line) Home Access Networks

• Provides internet through existing telephone lines
• Digital data is translated through telephones
• A DSL Access Multiplexer separates voice data and connects the ISP

Home Access Networks DSL (Digital Subscriber Line) Continued

• Frequency division multiplexing separates high speed downstream, medium-speed upstream, and telephone channels
• Ordinarily the DSL is asymmetric with higher download upload speeds
• The distance from the CO, wire gauge and interference can affect speed

HFC (Hybrid Fiber-Coaxial Cable) Home Access Networks

• The television cable network is connected to the internet
• Optical fiber cables connect to neighborhood junctions
• A cable modem connect to the Ethernet port
• Cable Modem Termination converted to digital

HFC (Hybrid Fiber-Coaxial Cable) Home Access Networks Continued.

• Downstream and upstream channels and separated through among users
• DSL provides a dedicated line, HFC is a shared medium
• Peak usaged can cause congestion even with higher speeds

Challenges in Home Access Networks

• Upload and Stream channels leading to congestion
• Drop speed rates happen when users download large files simultaneously
• Data collisions are reduced by shared channels

FTTH (Fiber to the Home) Home Access Networks

• Optical fiber provides speeds to the internet high speed
• Each home is dedicated to a private fiber by central office each home is committed
• It's shared to reduce costs with two main optical networks

FTTH (Fiber to the Home) continued

• Verizon uses PON
• At each home a split neighborhood is connected via fire
• Multiple combined units can be shared on each fire
• OLT converts electrical signals for performance
• 20 MPS high cable speed

Enterprise (LAN) Ethernet and Wifi

• Wifi is only implemented at corporate, university, and home settings
• Twisted-pair copper is used for connections
• Servers can access around approximately 1-10 Gbps
• Wireless wifi around 100+

Wireless Lan (WIFI) Enterprise (LAN) Ethernet and Wifi continued

• Tablets/smartphones connect an access point to an Ethernet
• Flexible WIFI connections are created by combining cables/DSL
• Modem seamless connections are made using wireless cables

3G/LTE Wide-Area Wireless Access

• Used for streaming messaging on smartphones.
• Works via base stations operated by cellular companies.
• WiFi range is a few of tens of meters
• Cellular is a few tens of kilometers.

4G/LTE Networks

• Provides speeds above 1 Mbps for packet-switched internet access
• LTE evolved from 3G, offers 10+ Mbps speeds
• Deployments report tens of Mbps speeds commercially

The Life of a Bit

• A bit has a transmitter receiver pair to get to one end-system to another through links.
• Occurs between physical media through electromagnetic pulses.

Cost of Physical Media

• low material costs compared to labor costs
• Avoids future rewiring

Twisted-Pair Copper Wire

• Most commonly used for transmission medium
• Telephone lines for over 100 years.
• Wires create electrical interfere if intertwined

Twisted-Pair Copper Wire Cont.

• buildings within commonly use LANs
• cables are bundled together

Coaxial Cable

• Composed of concentric shieldlings
• Insulated to be high transferred

Fiber Optics

• thin and flexible medium that conducts light pulses (bits)
• immune to electromagnetic interference
• hard to tap for security.

Fiber Optics Cont.

• Optical devices can be costly to use for short networks
• 51.8 Mbps to 39.8 Gbps link speeds

Terrestrial Radio Channels

• Electromagnetic spectrum is needed
• Walls can be penetrated

Terrestrial Cont.

• connectivity for mobile
• short distance runs about a few meters

Satellite Radio Channels

• Earth based on linked stations
• Satellite transmits signals that happen to be different

Satellite Radio Channels Cont.

• 36,000 km is positioned above earth (3-4)
• Does not stay in one place during time
• Needs to be in constant communication due to the distances

The Network Core

• links that switch make up end-systems to that of internet packets
• the message that is switch can contain data or control info

The Network Core cont.

• calculate with length over trans. rate
• Time = L/R

Store and Forward Transmission

• The switch needs to receive the packet before the link connects
• When trans delay has passed, the router sends to its destination

Queuing Delay

• Occurs to switch for each buffer switch delay when sent before transmission delay.
• The router sends between 100 MBPS from one to to the other and buffers congest the packet to cause delay

IP Addresses

• Used in systems for routing tables
• Forwarding tables are mapped to the router

Routing Protocols

• Determine how to set forwarding
• Uses the best path for data

Circuit Switching

Used on phones

• Switches maintain state of connection
• Rate if transfer maintained

Cont. Circuit Switching

• Alternative core
• 1/4 rate is the transmission depending on what's been set

Packet vs Switch

• Packets are made without a bandwidth/ resources
• A long delay might happen as the packet has to buffer

Mult switching

Frequency - divides bands

• Each is assigned a frequency connection

FDM and TDM

Frequency- Example radio use bandwidth to allow connections and to different stations.

Time frame - Time is allocated in those time based frame connections. Example: if 8,000 frames are linked at 8 bits then the trans is 64 kbps

Circuit transmission - Files

Network on transmission calculation of : (1.535 Mbps)/24 = 64 Mbps (640,00)/ (24/kb)= time seconds of 10

Switching Criticism

Criticism of packet being unsuitable in real-time settings due to calls

• Packet sharing is more efficient versus simple is better

Efficiency

1 Mbps linked when limited and compared to bandwidth using less time 0.004 with around 35 people

• Packet is limited to three connections at a time

Packet cont.

To users can get a million bits versus others getting it based on pre allocation

• packets don't need to waste transmission as a key advantage

Internet Structure: A Network of Networks

End systems (devices) connect to the Internet using access ISPs, like broadband, or cellular. These ISPs provide wired or wireless connectivity through technologies such as DSL, cable, WiFi, and cellular. These ISPs may not be telecom or cable companies, but could also be universities or companies providing access.

Interconnecting Access ISPs

Connecting end-users to access ISPs is a large part of Internet structure A network of networks allow systems to comminute A cost effective approach to connect directly

Global Transit ISP

Connecting access ISPs to a global transit ISP, with a worldwide network.

The transit and economic traffic would have routs near at the same access ISP to send traffic to

• Cost could be charged base of the global transit on access

Emergerence

Transit of companies that allow more and new networks

Global transits are built and interconnected between millions to different ISPs ISP get more transit providers, getting better cost and service.

Continued Emergence

Global transits must allow communities to ISPs. Transit is a high tier (Top) , access is low (lower to the bottem) but can shift

• Regional can assist

Enhancements of Network Structure

• Access to regional ISP

• Can be in the from of a global ISP and are mostly china.

• Poops enhance today's internet, allow more access from Ixp

• The locations are were router connect ISP

Multi continue

Multihoming : ensure connectivity even if the primary failed and

• Ixp: often free due to upstream intermediary.

Relationships Cont.

Costumers usually pay cost relationship bases on the amount transaction, The IxPS are made to trade this is usually is a great transaction More and better for the internet efficient and reduction cost

Delay Cont.

Delay has the main focus of improving the In the source header, detecting router to the way

Types of Delay

Nodal : Checking header. Queuing: Queuing delay: Time spent in the queue before the packet can be transmitted. Propagation : Time taken to travel through the physical link

Processing

Micro checking and routing from each other (micro seconds) Occurs at full queuing (packet drops) and traffic goes up, Retransmission is used so it will always increase if lost.

Impact

Traffic intensity decrease the delay to have a queuing system

Real Delays and Routes

Real-time program to test:

• Checks source to the destination
• Sends TTL, the sender measuring transmission replies.

Delays can then fail and be from the router!

Layers

Systems and routers protocols and cables are consisted in it Complex structures like the protocol. Layers can be simplified with design to it

Layers cont.

Each layer can be reliable that adds with unreliable functionality to the delivery

Transport delivers the network. While hardware usually is the data.

Stack and Drawbacks

Layers can be Modularity and the Internet has five main stack layers listed.