Networking.txt

Host : are any device which sends or received an traffic 
anything that sends or received traffic over a network 
all the devices have same rules for how they commun to the internet
hosts are sending and receiving the data

Client initiate requests, Servers respond
Relative to specific communication
Servers are simply computers with software installed which responds to specific requests


IP Address : is the identity of each host.
every single host must have an ip address
Just like need to a number order to send and receive phone calls 
you need a ip address in order to send or received packets on a network
every package which is received or sent with source and destination ip address
ip addresses are 32 bits 
bit = 1 or 0
represented as four octets
breaking up the ip address into their different hierarchicy done throught the process known as subnetting

Network : is what a transports traffic between hosts 
required similar connectivity which means all device should have same ip address

anytime two hosts are connected, you have a network
logical grouping of hosts which require similar connectivity
networks can contain other networks
networks connect to other networks
sometimes called sub-networks or subnets

internet is a bunch of network

Sending data across two device a wire is required

repeater sole purpose to regenerate the signal--> this allow you to connect devices together which span greater distances

hub is nothing more than a multi-port repeater
disadvantages : if one device want to sent packet to one other package then hub simply deplicate that package and sent it out all remaining ports
prblm : everybody received everybody else data for this bridge is introduced
 bridge sit bet hub-connected hosts
bridges only have two ports
bridges learn which hosts are on each side

switches are a combination of hubs and bridges 
facilitate comm within a network
if two devices want to speak each other switch will knows that the only ports that need to receive this traffic are the tow that are connected to those green hosts and keep that commun contained to just those ports and makes sure that comm only flows betw that relative ports

Router handle the commun betwn the 2 different networks
means 2 different devices which are belong to 2 different networks(different connectivities)
router provides traffic controls between the networks
routers facilitate comm bet networks
routing is the process of moving data bet networks
network boundary is what is meant to be the logical separation of devices
router learn which network they are attached to meeansrouter has ip address in every network that they're attached to
router use this route table to sent traffic out the appropriate interface

gateway : each host's way out of their local network
if host want to comm with other host within different network his knows have to go through a router and the ip address that host default store as the default gateway
routing table : all networks a router knows about 

TCP (Transmission control protocal) :
established connect before sending
TCP ensure that data received by the receiver in the correct format without error free and reached at correct address with correct format.
if any data package lost or corrupted it retransmitted it.
guaranteed delivery
avoid the network congestion
eg emails files

UDP ( )
Doesn't check for error nor format nor in order they were sent
does not established connect before sending
sends data package without checking received is ready to accept them
there is no guarantee
eg : online game video audio

ARP : Address resolution protocol
FTP : file transfer protocol client request a data to server in form of file
SMTP : simple mail transfer protocol used to exchange the mails

HTTP : Hyper text transfer protocol -->this protocol anytime u communicating with web server requesting web page

TLS : Transport layer security
established security ternal between client and server

one hosts must ip address of other host in order to communicate

While client server want to communicate with smtp sever or web server which don't have ip address dns domain name system convert this domain name to ip address

site.com-->74.208.5.20 

every host needs four items for internet connectivity
IP addrss : host's identity on the internet
subnet mask : size of the hots's network
default gateway : router's IP address
DNS Server IP : translate domain names to IPS

OSI model 
networking : allow two hosts to share data with one another

hosts must follow a set of rules

Physical : data exits in the form of bits ( 0 and 1)
transporting bits between hosts
transmission of raw data bits over a physical medium
l1 technologies : cables , wifi, repeaters, hubs


data link : interacts with wire
reliable transfer of data between two directly connected nodes, error detection, framing of data packets.
ensure that data transferred without error with the same network
sent bits on the wire and retrieve bits from the wire
hop to hop delivery uses addressing scheme mac address
switch allow to comm data to many devices
often comm bet hosts required multiple hops

network : end to end
manages the routing of data packets betn diff networks ensuring reaching to correct destionation
ip address allow to go data end to end 
routers hosts

Transport : service to service
distinguish data streams
insure that right program received right data
it provides error recovery, data segmentation, flo control for comm bet device

Session layer : manager connection betw appln
maintaining the state and ensuring comm remains open or closed as required

presentation layer :
translate, encrypts and compresses data bet appln n transport layer
so it can be understood by receiver

Appln layer : provide the service directly to end users