Clients Checklist

7/23/2019 Clients Checklist

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Winter 2005

CMPE 151: NetworkAdministration

Clients


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Client-Server Model


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Winter 2005

Client-Server Model

Client

Kernel

File Server

Kernel

Printer Serve

Kernel


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Winter 2005

File transfer


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Winter 2005

File transfer

Sarin! remote "les: #on-line$a%%ess vers&s #"le transfer$'

#(n-line$ a%%ess trans)arenta%%ess to sared "les* e'!'*distri+&ted "le s,stem'

Sarin! tro&! "le transfer: &ser%o)ies "le ten o)erates on it'


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Winter 2005

FP File transfer a%%o&nted for most of

te .nternet tra/% &ntil te We+

e)loded Also &ses CP' Allows intera%tive a%%ess format

s)e%i"%ation 3e'!'* +inar,4a&tenti%ation 3%lients re&ired toa&tenti%ate temselves4'


7/35Winter 2005

FP ()eration Client Server

OS

Data Control

OS

Data Control

TCP connection


8/35Winter 2005

Anon,mo&s FP Allows a%%ess to )&+li% "les' No need to a&tenti%ate &ser' A%%ess restri%ted to )&+li%l,

availa+le "les 3e'!'* in 6&sr6ft)4'


9/35Winter 2005

e We+ and 7P


10/35Winter 2005

Some 7istor, Started in 1898 at CEN* E&ro)ean

%enter for n&%lear resear%* in

Swit;erland' (ri!inal motivation: need for

s%ientists aro&nd te world to%olla+orate and sare m&lti-mediainformation'

im


11/35Winter 2005

More 7istor,> First tet-+ased )rotot,)e demo in

12'81'

elease of "rst !ra)i%al interfa%e*Mosai%* in 02'8? at NCSA +, M'Andreessen'

.n 188@* Andreessen %reates Nets%a)e' .n 188@* CEM and M. set &) te

WWW Consorti&m to f&rter develo) teWe+'

www'w?'or! for more information'


12/35Winter 2005

e We+ WWW* or te world-wide we+ is a

reso&r%e dis%over, servi%e' eso&r%e s)a%e is or!ani;ed

ierar%i%all,* and reso&r%es arelinked to one anoter a%%ordin! tosome relation'

7,)ertet or!ani;ation: link#!ran&larit,$ allows links witindo%&ments'

ra)i%al &ser interfa%e'


13/35Winter 2005

e %lient side Bsers )er%eive te We+ as a vast

%olle%tion of information'

Pageis te We+s information transfer &nit' Ea% )a!e ma, %ontain linksto oter

)a!es' Bsers follow links +, %li%kin! on tem wi%

takes tem to te %orres)ondin! )a!e' is )ro%ess %an !o on inde"netl,*

traversin! several )a!es lo%ated in diDerent)la%es'


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Winter 2005

e +rowser Pro!ram r&nnin! on %lient tat retrievesand dis)la,s )a!es' .ntera%ts wit server of )a!e'

.nter)rets %ommands and dis)la,s )a!e' Eam)les: Mosai%* Nets%a)es Navi!ator

and Comm&ni%ator* Mi%rosoft .nternetE)lorer'

(ter feat&res: +a%k* forward* +ookmark*%a%in!* andle m&ltimedia o+e%ts'


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Winter 2005

NS


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Winter 2005

omain Name S,stem

3NS4 IP addresses are not easy to remember. TheDomain Name System (DNS)mapsIP addresses tohost names.

Host name is formed by machine namefollowed bydomain name.

Host_name.domain_name

FCs 10?@ and 10?5'


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NS


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Winter 2005

NS

Thedomain_nameis formed by theinstitutionalsite nameand theTop-Level Domain name(TLD).

So the host name is of theform:machine_name.Ist_site_name.TLD_name

Examples:

sundance.ucsc.edu

soe.ucsc.edu (alias forsundance.ucsc.edu)

italia.cse.ucsc.edu

helios.jpl.nasa.gov


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Winter 2005

Top-Level Domains (TLDs)

TLD names identifyorganization typesorcountry codes.

Examples:.com Commercial org. .auAustralia

.edu Educational site in US .ca Canada

.govGovernment site in US .frFrance

.mil Military organization in US .de Germany

.net Network site .ukGreat Britain

.orgNonprofit organization .it Italy

.es Spain

Countries define their own internal hierarchy (e.g., .ac.uk, .edu.au)


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Winter 2005

DNS hierarchy

Organizations can create any internal DNShierarchy.

Authority for creating newsubdomainswithin

a domain name is delegated to each domain.Administration ofucsc.eduhas authority tocreatecse.ucsc.eduand need not contactany central naming authority.


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Winter 2005

Example DNS Hierarchy


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DNS Name Space

DNS names are managed by a hierarchy ofDNS servers.

Hierarchy is related to DNS domain hierarchy Root server at top of tree knows about nextlevel servers.

Next level servers, in turn, know about lower

level servers.


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Example of DNS Hierarchy


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Example of DSN Hierarchy


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Winter 2005

Choosing DNS Server

Architecture Small organizations can use a single server. Easy to administer.

Inexpensive.

Large organizations often use multipleservers.

Reliability through redundancy.

Improved response time through load sharing.


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Name Resolution

Resolving a name means mapping the hostname to the IP address.

Reverse mapping is also possible.

Aclientcomputer calls aDNS serverforname resolution

DNS request contains name to be resolved.

DNS reply contains IP address for name inrequest.


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Winter 2005

Name resol&tion 3%ontd4 Client NS 3r&nnin! on %lient

osts4* or resolver' A))li%ation %alls resolver wit

name' esolver %onta%ts lo%al NS server

3&sin! BP4 )assin! te name' Server ret&rns %orres)ondin! .P

address'


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Winter 2005

Name resol&tion 3%ontd4 A))li%ation wants to resolve name' esolver sends &er, to lo%al name

server' esolver %on"!&red wit list of lo%al name

servers' Sele%t servers in ro&nd-ro+in fasion'

.f name is lo%al* lo%al name server ret&rnsmat%in! authoritatives' Authoritative %omes from a&torit,

mana!in! te and is alwa,s %orre%t'

Cacheds ma, +e o&t of date'


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Winter 2005

Name resol&tion 3%ontd4 .f information not availa+le lo%all,

3not even %a%ed4* lo%al NS will

ave to ask someone else' .t asks te server of te to)-level

domain of te name re&ested'


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Winter 2005

Ele%troni% mail Non-intera%tive'

eferred mail 3e'!'* destination

tem)oraril, &navaila+le4' S)oolin!:

Messa!e deliver, as +a%k!ro&nd

a%tivit,' Mail s)ool: tem)orar, stora!e area

for o&t!oin! mail'


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Winter 2005

Mail s,stem

User

interface

User

sends mail

User

reads mail

Outgoing

mailspool

Mailboxes

incomingmail

Client(send

Server

(receive

TCP

connection

(outgoing

TCP

connection(incoming


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Winter 2005

(+servations Wen &ser sends mail* messa!e

stored is s,stem s)ool area'

Client transfer r&ns on +a%k!ro&nd' .nitiates transfer to remote

ma%ine'

.f transfer s&%%eeds* lo%al %o), ofmessa!e removed oterwise* triesa!ain later 3?0 min4 for amaim&m interval 3? da,s4'


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emote a%%ess


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elnetUser!s

mac"ine

Telnet

client

OS

TCP connectionover #nternet

Telnet

server

OS


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elnet +asi% o)eration Wen &ser invokes telnet* telnet %lient

on &ser ma%ine esta+lises CP%onne%tion to s)e%i"ed server'

CP %onne%tion esta+lised &serske,strokes sent to remote ma%ine'

elnet server sends +a%k res)onse*

e%oed on &sers terminal' elnet server %an a%%e)t m&lti)le

%on%&rrent %onne%tions'

Clients Checklist

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