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Summary 1.3. - computer networks, connections and protocols
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OCR COMPUTER SCIENCE J277 1.3. - COMPUTER NETWORKS, CONNECTIONS AND PROTOCOLS achieved grade 9 at GCSE
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) W io\L A^acl NeJn uc,rz\,.a global network of interconnected networks
-> DOMAIN NAME SERVER - converts a website address (URL) e.g. www.google.co.uk into an IP address e.g.
t72.277.L1+.795 so that a browser on a client machine can make a request to the correct server hosting that
web page /.a s\oi^q or u-r-Lr silt ct\,\cl \!t-b ><xvz.{-
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, HOSTING - when a website is on a web sewer for people to see. A website needs to have a unique and
suitable name. The DNS checks if it is unique and not already registered. Each domain name has an Ip
address
what happens when a website address is typed into a browser?
1. Enter URL into browser e.3. ww,*t.3o"le.cofi ivr!t-r.c-l sc-y.,i ce 9 ro.rl &.r^
2. Browser requests IP address of the sitc from ISP
). ISP requests 1P address from DN server Acr,r,,.*i*. no. er.i{ S4, v€-l.
4. DNS responds with details of the name server
5. ISP asks name server for site IP address
6. Name server responds with IP address of the host
7. ISP sends IP address to the browser
8. Browser sends request to the server hosting the site
9. Server hosting the site sends across content
10. Browser receives website content
11. Website displayed to the user
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The cloud is a network of servers. E.g. google drive, one drive
+ Flexible storage is provided
+ Exprensive hardware is not needed
+ Regular backups and security
+ Can access files anywhere $'o ^a cr'r- clr--i cf r u."r1 H r^ f
- Need a reliable internet connection
-
- No direct control over the security of the data
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A network standard is a set of agreed requirements for and software. are important as they
allow manufacturers to create pjoducts anarythatwill b" .qlqp@with products and programs
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A network protocol is a set of rules for how devices communicate and how data is transmitted across a
network.
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An IP address is a unique public address for the router of a network. Data packets use this address to travel to
the router, then they are directed using a private IP address within the network. changes when the network
changes ,/ +'*" pc*tl-S n!fu* tc i d-o-vtkke- , L.l i l^l;k Q-...
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=llp"? - 3z bits. lion _"_^tYgh
IP addresses. Split into 16 bit chunks and e-ai-h iiie'i6 given as a
hexadecimal number - wdl-l-e". as 4 n u,,,.l'y...19 , gep o-o.-r-J. Ly tut( -g hXS .
j@ rz8 bits.6'zG)P addresses. Split into 8 bit chunks and each one is given as a denary number
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\/ Alt'IACaddressisuniqueandcannotbechanged.Either 4Sor64bitbinarynumbers. USva.lly fZ Jllit-S
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Protocols ) c ot.t wa^kica_b ove,r L aVs I W /*Ns
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ltCP/IP is the protocol which dictates how data is sent between networks. Made up of two protocols.
Transmission Control Protocol (TCP) - sets the rules for how devices connect on the network
Internet Protocol (IP) - responsible for directing packets to their destination across the network
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HTTP Hyper Text Transfer Proocol Used h'Urub-btpUiSCO to acces yelEiles and communicate with .,1,',1.
HTTPS HTTP Secure A nmre se.cufe rersion of inlrormation sent cnd received.
FTP FileTransier Protocol Used to access, edit and nrov{I&betvueen devices on a network,
files ofl a server frsn a client csmputer Lttu^N
POP3 Ib6t dfice Pnlocol Used ,,,.. a server. The sener holds the emSil until lotr
- rersion 3 point it is(klskiUrom the senrer. - olJa:. lla-a4 S
IIITAP lnternet A,'lessage Access Lfsed to rgtrieleenrnill frc*n a rerver. The server holds the email until }urr ./ Ov'\
Prmaol pa.J
detgeit :.')€gg!btdqt sepry. Used by rnost wetsbased ermil clienr.
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5,\1TP Simple Mail Transfer Prorocol -wr{ rrnr:rilc Also used to transfer emails betrveen s€ri/ers. ktv<-r
A LA\E( \S A D\V\E\C'Y! Otr Ntr-\WORK FUNCTIONIA tt114
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A layer is a group of protocols which have similar functions. 'l'hcy arc self -contained. Each layer seryes the
layer above it. Data can only be passed between adjacent layers
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J dau into plEec$ nnclchecking dau is l&st a{'rrd deliuemd. TCP
l Making qpcnectims herv*'een networks and direc;ing data. IP
1 hssing dsta tas elearical signalsr orler the phpgalmmerk [thelnet
+ Breaks down network communication into manageable pieces
+ Layers can be changed without affecting other layers
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