internetworking basics study guide

7/25/2019 Internetworking Basics Study Guide

1/30

12/02/2015

Internetworking Basics

Heres a list of some of the things that commonly cause LAN traffic

congestion

!oo many hosts in a collision or "roa#cast #omain

Broa#cast storms !oo much multicast traffic

Low "an#wi#th

A##ing hu"s for connecti$ity to the network

A "unch of A%& "roa#casts

!here are two a#$antages to using routers in your network

!hey #ont forwar# "roa#casts "y #efault'!hey can filter the network "ase# on layer () Network layer) information

such as an I& a##ress'Here are four ways a router functions in your network&acket switching

&acket filteringInternetwork communication

&ath selection

*witches create se+arate collision #omains within a single "roa#cast

#omain' %outers +ro$i#e a se+arate "roa#cast #omain for each

interface'

,ont let this e$er confuse you

-ou woul# use a "ri#ge in a network to re#uce collisions within

"roa#cast


2/30

#omains an# to increase the num"er of collision #omains in your

network'

,oing this +ro$i#es more "an#wi#th for users' An# ne$er forget that

using

hu"s in your .thernet network can contri"ute to congestion' As

always) +lan your network #esign carefully

LANs) which are use# when you logically "reak u+

"roa#cast #omains in a layer 2) switche# network

Internetworking o#els

A#$antages of %eference o#els

!he *I mo#el is hierarchical) an# there are many a#$antages that

can "e a++lie# to any layere# mo#el) "ut as I sai#) the *I mo#els +rimary +ur+ose is to

allow #ifferent $en#ors

networks to intero+erate'

Heres a list of some of the more im+ortant "enefits for using the *I

layere# mo#el

!he 3++er Layers

!he Lower Layers


3/30

It #i$i#es the network communication +rocess into smaller an# sim+ler

com+onents)

facilitating com+onent #e$elo+ment) #esign) an# trou"leshooting'

It allows multi+le4$en#or #e$elo+ment through the stan#ar#iation of

network

com+onents'

It encourages in#ustry stan#ar#iation "y clearly #efining what

functions occur at each

layer of the mo#el'

It allows $arious ty+es of network har#ware an# software to

communicate'

It +re$ents changes in one layer from affecting other layers to

e6+e#ite #e$elo+ment

!he u++er layers

!he following network #e$ices o+erate at all se$en layers of the *I

mo#el

Network management stations 7N*s8

9e" an# a++lication ser$ers

:ateways 7not #efault gateways8

*er$ers

Network hosts

!he *I reference mo#el has the following se$en layers

A++lication layer 7layer ;8


4/30

&resentation layer 7layer unctions

!he Layere# A++roach

!he A++lication layer of the *I mo#el marks the s+ot where users

actually communicate

to the com+uter an# comes into +lay only when its clear that access to

the network will "e nee#e# soon' !ake the case of Internet .6+lorer 7I.8' -oucoul# actually uninstall e$ery trace of networking com+onents like !?&/I&)

the NI? car#) an# so on an# still use I. to $iew a local H!L #ocument'

!he A++lication layer works as the interface "etween actual a++lication

+rograms' !his means en#4user +rograms like icrosoft 9or# #ont

resi#e

at the A++lication layer) they interface with the A++lication layer

+rotocols'


5/30

!he &resentation layer ensures that #ata transferre# from the

A++lication layer of one system can "e rea# "y the A++lication layer of

another one'

!he *ession layer is res+onsi"le for setting u+) managing) an##ismantling sessions "etween &resentation layer entities an# kee+ing user

#ata se+arate' ,ialog control "etween #e$ices also occurs at this layer

!he !rans+ort layer segments an# reassem"les #ata into a single #ata

stream' !he term relia"le networking can "e use# at the !rans+ort layer'

%elia"le networking re@uires that acknowle#gments) se@uencing) an# flowcontrol will all "e use#'

?onnection4riente# ?ommunication

>or relia"le trans+ort to occur) a #e$ice that wants to transmit mustfirst esta"lish a connection4oriente# communication session with a remote

#e$iceits +eer systemknown as a call setu+ or a three4way han#shake'


6/30

>low ?ontrol


7/30

!he +ur+ose of flow control is to +ro$i#e a way for the recei$ing #e$ice

to

control the amount of #ata sent "y the sen#er'

A ser$ice is consi#ere# connection4oriente# if it has the following

characteristics

A $irtual circuit) or three4way han#shakeC is set u+'

It uses se@uencing'

It uses acknowle#gments'

It uses flow control'


8/30

9in#owing

!he @uantity of #ata segments) measure# in "ytes)

that the transmitting machine is allowe# to sen# without recei$ing an

acknowle#gment is calle# a win#ow'

9in#ows are use# to control the amount of outstan#ing)

unacknowle#ge#

#ata segments'


9/30

If a recei$ing host fails to recei$e all the "ytes that it shoul#

acknowle#ge)

the host can im+ro$e the communication session "y #ecreasing the

win#ow sie'

Acknowle#gments


10/30

%elia"le #ata #eli$ery ensures the integrity of a stream of #ata sent

from one machine to the other through a fully functional #ata link' It

guarantees that the #ata wont "e #u+licate# or lost'

!he Network layer) or layer () manages #e$ice a##ressing) tracks the

location of #e$ices on the network) an# #etermines the "est way to mo$e

#ata'

Here are some router characteristics that you shoul# ne$er forget

%outers) "y #efault) will not forwar# any "roa#cast or multicast

+ackets'

%outers use the logical a##ress in a Network layer hea#er to #etermine

the ne6t4ho+ router to forwar# the +acket to'


11/30

%outers can use access lists) create# "y an a#ministrator) to control

security "ase# on the ty+es of +ackets allowe# to enter or e6it an interface'

%outers can +ro$i#e layer 2 "ri#ging functions if nee#e# an# can

simultaneously route through the same interface'

Layer ( #e$icesin this case) routers+ro$i#e connections "etween

$irtual LANs 7LANs8'

%outers can +ro$i#e @uality of ser$ice 7Do*8 for s+ecific ty+es of

network traffic'

!he ,ata Link layer +ro$i#es for the +hysical transmission of #ata an#

han#les error notification) network to+ology) an# flow control'

!he I... .thernet ,ata Link layer has two su"layers

e#ia Access ?ontrol 7A?8

,efines how +ackets are +lace# on the me#ia' ?ontention me#ia

access is first come/first ser$e#C access where e$eryone shares the same"an#wi#thhence the name' &hysical a##ressing is #efine# here as well as

logical to+ologies'

9hats a logical to+ologyE Its the signal +ath through a +hysical

to+ology' Line #isci+line) error notification 7"ut not correction8) the or#ere#

#eli$ery of frames) an# o+tional flow control can also "e use# at thissu"layer'

Logical Link ?ontrol 7LL?8%es+onsi"le for i#entifying Network layer +rotocols an# then

enca+sulating them' An LL? hea#er tells the ,ata Link layer what to #o witha +acket once a frame is recei$e#' It works like this a host recei$es a frame

an# looks in the LL? hea#er to fin# out where the +acket is #estine#forinstance) the I& +rotocol at the Network layer'

!he LL? can also +ro$i#e flow control an# se@uencing of control "its'


12/30

*witches an# Bri#ges at the ,ata Link Layer

Layer 2 switching is consi#ere# har#ware4"ase# "ri#ging "ecause it

uses s+ecialie# har#ware calle# an a++lication4s+ecific integrate# circuit

7A*I?8' A*I?s can run u+ to high giga"it s+ee#s with $ery low latency rates'

*o) networks are to routers as in#i$i#ual #e$ices are to switches an#

"ri#ges' An# routing ta"les that ma+C the internetwork are for routers) as

filter ta"les that ma+C in#i$i#ual #e$ices are for switches an# "ri#ges'

!he &hysical Layer

>inally arri$ing at the "ottom) we fin# that the &hysical layer #oes two

things it sen#s "its an# recei$es "its' Bits come only in $alues of 1 or 0a

orse co#e with numerical $alues'

Hu"s at the &hysical Layer

A hu" is really a multi+le4+ort re+eater' A re+eater recei$es a #igital

signal) ream+lifies or regenerates that signal) then forwar#s the signal outthe other +ort without looking at any #ata'

.6am .ssentials

I#entify the +ossi"le causes of LAN traffic congestion' !oo many hosts

in a "roa#cast #omain) "roa#cast storms) multicasting) an# low "an#wi#th

are all +ossi"le causes of LAN traffic congestion'


13/30

,escri"e the #ifference "etween a collision #omain an# a "roa#cast

#omain' ?ollision #omain is an .thernet term use# to #escri"e a network

collection of #e$ices in which one +articular #e$ice sen#s a +acket on a

network segment) forcing e$ery other #e$ice on that same segment to +ayattention to it' 9ith a "roa#cast #omain) a set of all #e$ices on a network

hear all "roa#casts sent on all segments' ,ifferentiate a A? a##ress an# an I& a##ress an# #escri"e how an#

when each a##ress ty+e is use# in a network' A A? a##ress is a

he6a#ecimal num"er i#entifying the +hysical connection of a host' A?

a##resses are sai# to o+erate on layer 2 of the *I mo#el'

I& a##resses) which can "e e6+resse# in "inary or #ecimal format) are

logical i#entifiers that are sai# to "e on layer ( of the *I mo#el' Hosts onthe same +hysical segment locate one another with A? a##resses) while I&

a##resses are use# when they resi#e on #ifferent LAN segments or su"nets'

3n#erstan# the #ifference "etween a hu") a "ri#ge) a switch) an# a

router' A hu" creates one collision #omain an# one "roa#cast #omain' A"ri#ge "reaks u+ collision #omains "ut creates one large "roa#cast #omain'

!hey use har#ware a##resses to filter the network' *witches are really Fustmulti+le4+ort "ri#ges with more intelligenceG they "reak u+ collision #omains

"ut

creates one large "roa#cast #omain "y #efault' Bri#ges an# switches

use har#ware a##resses to filter the network' %outers "reak u+ "roa#cast

#omains 7an# collision #omains8 an# use logical a##ressing to filter thenetwork'

I#entify the functions an# a#$antages of routers' %outers +erform

+acket switching) filtering) an# +ath selection) an# they facilitate

internetwork communication' ne a#$antage of routers is that they re#uce"roa#cast traffic'

,ifferentiate connection4oriente# an# connectionless network ser$ices

an# #escri"e how each is han#le# #uring network communications'

?onnection4oriente# ser$ices use acknowle#gments an# flow control to

create a relia"le session' ore o$erhea# is use# than in a connectionlessnetwork ser$ice' ?onnectionless ser$ices are use# to sen# #ata with no

acknowle#gments or flow control' !his is consi#ere# unrelia"le'


14/30

,efine the *I layers) un#erstan# the function of each) an# #escri"e

how #e$ices an# networking +rotocols can "e ma++e# to each layer' -ou

must remem"er the se$en layers of the *I mo#el an# what function each

layer +ro$i#es' !he A++lication) &resentation) an# *ession layers are u++erlayers an# are res+onsi"le for communicating from a user interface to an

a++lication' !he !rans+ort layer +ro$i#es segmentation) se@uencing) an#$irtual circuits' !he Network layer +ro$i#es logical network a##ressing an#

routing through an internetwork' !he ,ata Link layer +ro$i#es framing an#

+lacing of #ata on the network me#ium' !he &hysical layer is res+onsi"le fortaking 1s an# 0s an# enco#ing them into a #igital signal for transmission on

the network segment'

.thernet Networks in %e$iew

.thernet is a contention4"ase# me#ia access metho# that allows all

hosts on a network to share the same links "an#wi#th'

Broa#cast ,omain

Let me start "y gi$ing you the formal #efinition "roa#cast #omain

refers to a grou+ of #e$ices on a s+ecific network segment that hear all the

"roa#casts sent out on that s+ecific network segment'

?*A/?,

.thernet networking uses a +rotocol calle# ?arrier *ense ulti+le

Access with ?ollision ,etection 7?*A/?,8) which hel+s #e$ices share the

"an#wi#th e$enly while +re$enting two #e$ices from transmittingsimultaneously on the same network me#ium'

9hen a collision occurs on an .thernet LAN) the following ha++ens

1' A Fam signal informs all #e$ices that a collision occurre#'

2' !he collision in$okes a ran#om "ackoff algorithm'

(' .ach #e$ice on the .thernet segment sto+s transmitting for a short

time until its "ackoff timer e6+ires'

=' All hosts ha$e e@ual +riority to transmit after the timers ha$e

e6+ire#'

.thernet at the ,ata Link Layer

.thernet at the ,ata Link layer is res+onsi"le for .thernet a##ressing)

commonly referre# to as A? or har#ware a##ressing


15/30


16/30

.thernet >rames !he ,ata Link layer is res+onsi"le for com"ining "its into "ytes an#

"ytes into frames' >rames are use# at the ,ata Link layer to enca+sulate+ackets han#e# #own from the Network layer for transmission on a ty+e of

me#ia access'


17/30


18/30

.thernet at the &hysical Layer

.thernet was first im+lemente# "y a grou+ calle# ,I) which stan#s

for ,igital) Intel) an# ero6' !hey create# an# im+lemente# the first

.thernet LAN s+ecification) which the I... use# to create the I... 02'(

committee' !his was a 10 "+s network that ran on coa6 an# thene$entually twiste#4+air an# fi"er +hysical me#ia'

!he .IA/!IA s+ecifies that .thernet use a registere# Fack 7%J8

connector on

unshiel#e# twiste#4+air 73!&8 ca"ling 7%J=58'


19/30

.thernet ?a"ling

*traight4through ca"le

?rosso$er ca"le %olle# ca"le


20/30


21/30


22/30


23/30

>i"er +tic

>i"er4o+tic ca"ling has "een aroun# for a long time an# has some soli#

stan#ar#s' !he ca"le allows for $ery fast transmission of #ata) is ma#e of

glass 7or e$en +lastic8) is $ery thin) an# works as a wa$egui#e to transmit

light "etween two en#s of the fi"er' >i"er o+tics has "een use# to go $ery

long #istances) as in intercontinental connections) "ut it is "ecoming more an# more +o+ular in .thernet LAN networks #ue to the fast s+ee#s

a$aila"le an# "ecause) unlike 3!&) its immune to interference like cross4talk'


24/30


25/30

!he ?isco three4Layer Hierarchical o#el

!he ?ore Layer

!he core layer is literally the core of the network' At the to+ of the

hierarchy) the core layer is res+onsi"le for trans+orting large amounts of

traffic "oth relia"ly an# @uickly' !he only +ur+ose of the networks core layeris to switch traffic as fast as +ossi"le'


26/30


27/30


28/30


29/30

!elnet was one of the first Internet stan#ar#s) #e$elo+e# in 1K


30/30

*ecure *hell 7**H8 +rotocol sets u+ a secure session thats similar to

!elnet o$er a stan#ar# !?&/I& connection an# is em+loye# for #oing things

like logging into systems) running +rograms on remote systems) an# mo$ing

files from one system to another' An# it #oes all of this while maintaining anencry+te# connection

>ile !ransfer &rotocol 7>!&8 actually lets us transfer files) an# it can

accom+lish this "etween any two machines using it' But >!& isnt Fust a+rotocolG its also a +rogram' +erating as a +rotocol) >!& is use# "y

a++lications

!ri$ial >ile !ransfer &rotocol 7!>!&8 is the stri++e#4#own) stock $ersion

of >!&) "ut its the +rotocol of choice if you know e6actly what you want an#

where to fin# it "ecause its fast an# so easy to use

*im+le Network anagement &rotocol 7*N&8 collects an#mani+ulates $alua"le network information) as you can see in >igure (';' Itgathers #ata "y +olling the #e$ices on the network from a network

management station 7N*8 at fi6e# or ran#om inter$als) re@uiring them to

#isclose certain information) or e$en asking for certain information from the#e$ice' In a##ition) network #e$ices can inform the N* station a"out

+ro"lems

as they occur so the network a#ministrator is alerte#

Hy+erte6t !ransfer &rotocol 7H!!&8 to make it all +ossi"le 7>igure ('8'

Its use# to manage communications "etween we" "rowsers an# we"ser$ers an# o+ens the right resource when you click a link) where$er thatresource may actually resi#e'

internetworking basics study guide

Documents