Computer Networks and Internet Structure

Computer Networks and the Internet Overview

• Computer networks entail a network of diverse, interconnected components from end-systems to network cores using sophisticated architectures
• The Internet is a network of networks connected to each other
• This enables users to connect to each other via any internet enabled device

Examining Network Performance

• Key performance metrics in computer networks include delay, loss, throughput with end-to-end delay, queuing delays
• It is important architectural principles like protocol layering and different service models
• Computer networks are vulnerable to attacks so we should consider secure alternatives

Internet Structure

• The public Internet is often used in discussing computer networks
• The basic hardware and software components of the Internet defines the nuts and bolts while its service to distributed applications defines the networking infrastructure
• The Internet connects billions of computing devices from traditional desktops and workstations to smartphones, tablets, TVs, gaming consoles, thermostats, and home appliances
• These devices are called "hosts" or "end systems
• By 2022, the number of Internet-connected devices is projected to reach 28.5 billion

How devices interconnect

• End systems connect through communication links and packet switches
• Communication links use physical media like coaxial cable, copper wire, optical fiber, and radio spectrum with different data transmission rates
• Data is segmented into packets, which include header bytes
• Packets are forwarded by packet switches, such as routers and link-layer switches, towards their destination
• Link-layer switches are used in access networks, while routers are used in the network core
• The path taken by a packet is known as route or path

ISPS & Data

• The Internet relies on Internet Service Providers (ISPs) for end system access
• ISPs include residential, corporate, university, WiFi, and cellular data providers; they consist of packet switches and communication links
• ISPs offer various access types like cable modem, DSL, high-speed LAN, and mobile wireless
• ISPs are interconnected with lower-tier ISPs also interconnected through national and international upper-tier ISPs which use high-speed routers with fiber-optic links
• Each ISP network is managed independently, runs the IP protocol, and follows naming, addressing conventions
• Protocols like TCP and IP control information flow
• TCP handles reliable data transfer, while IP specifies packet format
• Collectively, principal protocols are known as TCP/IP standards which are set by the Internet Engineering Task Force (IETF) documents called requests for comments (RFCs) Standards exist for network components like the IEEE 802 LAN that specifies Ethernet and WiFi.

Network Services

• The Internet infrastructure provides services to applications, including traditional like e-mail, web surfing and emerging such as mobile apps, internet messaging and video conferencing
• This includes multiple end systems that exchange data with each other known as distributed applications
• Internet apps run on end systems, not the network core

Protocols

• Protocols enable programs on different end systems to exchange data, for example, using a socket interface to send and receive data
• Protocols are sets of rules that need to be followed for data transmission
• Anologies like mailing a letter requires placing putting the letter in an envelope, and addressing, adding correct postage and marking for appropriate handling
• Internet applications must choose one of the Internet's services for the application.

Network classifications

• The Internet is can be described in terms of hardware, software, and an infrastructure providing services to distributed applications
• Terms such as packet switching and IP are fundamental terms of the system
• Protocols is a buzz word for computer networking

Human Analogies

• Protocols can be explained using human interactions, e.g. asking for time
• A greeting indicates a willingness to communicate
• Different replies determine willingness to engage in conversation
• This involves explicit messages and actions as well as Implicit messages sent and received.

Network Protocols

• Network protocols involve hardware or software components exchanging messages
• All Internet activity is governed by protocols
• They define message format, order, and actions
• Protocols facilitate tasks
• Examples are web requests
• A computer will request a connection and will wait for response, and then send specific web page name and server will return the page to the computer

The network edge

• The Internet comprises computers and other devices that interface with it on a daily basis and include desktops, smartphones and so forth

Hosts

• This networked system includes end systems (e.g., PCs, Macs, Linux), servers (e.g., web and e-mail), laptops, and mobile devices that host application programs
• Hosts consist of clients and servers
• Clients are desktops, laptops, whereas servers handle web pages, stream video or relay e-mail and mobile apps
• Servers are in data centers containing millions of servers and the data centers function to serve e-commerce, computing tasks, and cloud computing
• Amazon Web Services (AWS) for example operates in the cloud so companies can host their needs there

Accessing the Network

• Residential access include Digital Subscriber Line (DSL)
• It is predominantly residential access through same local telephone company. a customer's telco is also its IPS, where single DSL link appear as 3 separate links
• A residence obtains cable Internet access from the same company that provides cable television connecting neighborhood juncions to indiidual houses and apartments

Fiber access

• Third generation is fiber to the home (FTTH) offering high speed optical fiber from to the home called direct fiber
• Competing technologies exist for optical distribution

5G Wireless

• Wireless is increasingly popular for accessing the internet via laptops, smartphones, tablets, and access points that transmits/receives packets to/ from wireless devices
• A wireless LAN user must be in a home environment and can make internet access affordable.

Media transmission

• Transmission involved having bit pass through transmitters-receivers pairs.
• It included electromagnetic waves or optical pulses as transmitter and receiver via physical medium, which can be wires or wireless
• Physical media is split into guided and unguided
• guided media involves a solid link, either wired, coaxial, or fiber
• unguided involves communicating in atmosphere either wirelesly or via satellite
• The labor cost for infrastructure installation is typically high, hence all options are installed at once
• Twisted-pair copper wire comprises insulated wires arranged in a spiral pattern
• The wires twisted reduce electrical interference
• Cables wrap the twisted pairs in sheilds
• Coaxial includes copper conductors where isulation and sheilding to achieve high data rates
• Fiber Optics is flexible and conducts lights
• Fiber offers immunity to electromagnet interference and low signal attenuation up to 100 kilometers
• Fiber also prevalent in backbones but too costly devices for short run installs

Radio Signals

• Radio channels transmit electromagnetic spectrum that can penetrate walls including satellites
• Radio channel characteristics are affected by the propagation environment and factors, such as distance, path loss, fading, and interference.
• Satellite channels link two or more Earth-based stations using microwave transmitter with repeaters
• Satellite signals are transmitted on one frequency band and regenerated/transmitted on another; used using geostationary and/or low-earth orbiting
• Earth stationary remain above 36,000kmeters
• LEO satellites may not communicate with ground stations instead of other satellites
• A huge distance causes signal propagation delay, but can work in areas without Internet access

Network Core

• Packet switches and links interconnect end systems in the Internet
• Packet switches use transmission at a rate equaled full transmission rate on each communication link
• Most switches use store-and-forward transmission
• In store-and-forward, the packet switch receives the entire packet before retransmitting.
• Packet switched networks suffer both forwarding delays and output buffer delays, which is variable

Routing and Forwarding

• Each end system requires an IP address
• Packets use destination addresses and head information with hirarchical structure
• The car analogy is how a driver gets directions to their point

Circuit Switching

• Two ways to move Data through a network are with circuit and packet
• In circuit switching, the means necessary to communicate between two end connections remain reserved for the entire duration
• The phone network relies on such technology
• Transmissions use frequency-division and time-division multiplexing to optimize the performance between connections
• It is more effective to use packing switching for efficiency because they better allocate data streams where circuit would pre-allocate data

Network structures

• Access ISPs need to connect to that all connect at the highest network level providing a service to customer framework consisting tier one providing access to to tier two etc
• Each ISP is only capable of getting close to some Access

Peering

• To create better performing, lower latency, customer/customer relationship
• PoPS
• Multi homing
• Peerings
• Inter exchange points in the existing structure

Network Model

• Private and governmental entities have began running their own network and directly peering

Transmission Issues

• Data travels from one end to another which is subjected to constraints
• Networks control the amount of data and introduce loses and delats
• Each packet faces different delays at routers in transfer network of delay
• These add with total nods delay are processing , queuing ,transmission , and propogation
• This effect performance of internet applications

Nodal delay

• Processing is time examines and directing packets from the upstream nodes and transmits link and to link b, and process delays high speeds routers typically

Queuing Delay

• Packet and the link experiences delat ,
• As packet weights to get transmitted
• Quing delays variable functions of traffic of queues from microns to militiseconds
• packets transmit and with first come serve only after receiving by all previous, packet to transmit- it depended the packets link between that transmission delays and of propapgation depending, depends on transmitter and of routers it could be in milliseconds depending links of delay

Comparing Transmission and Propagation Delay

• If more caravan car analogy to clarify the notion of transmition rate and propogate, and toll booth service is less then highway service that will not be possible.

Losses

• Queue's have capacities and data sent that exceeds capacities is lost that it needs to resend it over in the end

End to length

• Discussion of up has focus is on note delray to and for entire route need consider from source/ destination total it. We will be the 260

Traceroute

• Get that for the network it does it multiple of points delays- End system are and significant
• We still consider a connection example from end that is useful to more
• End System, Application and other delays
• Important a that can impact the user or perception Quality to col that is so