mc0087 internetworking with tcp ip

8/10/2019 MC0087 Internetworking With Tcp IP

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Que 1 What is application layer? Discuss any four protocols with its role that are used forexchange of information.

Ans: In the Internet model the application layer is an a!straction layer reser"ed forcommunications protocols and methods designed for process#to#process communicationsacross an Internet $rotocol %I$& computer networ'. Application layer protocols use theunderlying transport layer protocols to esta!lish process#to#process connections "ia ports.

In the ()I model the de*nition of its application layer is narrower in scope. +he ()I model

de*nes the application layer as !eing the user interface. +he ()I application layer isresponsi!le for displaying data and images to the user in a human#recogni,a!le format and tointerface with the presentation layer !elow it.

It separates functionality a!o"e the transport layer at two additional le"els the session layerand the presentation layer. ()I speci*es strict modular separation of functionality at theselayers and pro"ides protocol implementations for each layer. +he interface responsi!le fordisplaying the information recei"ed to the user.

-our layers are:

HTTP : +he ypertext +ransfer $rotocol % ++$& is an application protocol for distri!uted

colla!orati"e hypermedia information systems. ++$ is the foundation of datacommunication for the World Wide We!.

ypertext is structured text that uses logical lin's %hyperlin's& !etween nodes containing text.++$ is the protocol to exchange or transfer hypertext.

++$ functions as a re/uest#response protocol in the client#ser"er computing model. A we!!rowser for example may !e the client and an application running on a computer hosting awe! site may !e the ser"er. +he client su!mits an ++$ re/uest message to the ser"er. +heser"er which pro"ides resources such as +0 *les and other content or performs otherfunctions on !ehalf of the client returns a response message to the client. +he responsecontains completion status information a!out the re/uest and may also contain re/uested

content in its message !ody.FTP: -ile +ransfer $rotocol %-+$& is a standard networ' protocol used to transfer *les from onehost to another host o"er a +2$#!ased networ' such as the Internet.

-+$ is !uilt on a client#ser"er architecture and uses separate control and data connections!etween the client and the ser"er. -+$ users may authenticate themsel"es using a clear#textsign#in protocol normally in the form of a username and password !ut can connectanonymously if the ser"er is con*gured to allow it. -or secure transmission that hides%encrypts& the username and password and encrypts the content -+$ is often secured with)) 3+ ) %4-+$)4&.

-+$ may run in acti"e or passi"e mode which determines how the data connection isesta!lished. In acti"e mode the client creates a +2$ control connection. In situations wherethe client is !ehind a *rewall and una!le to accept incoming +2$ connections passi"e modemay !e used. In this mode the client uses the control connection to send a $A)5 command tothe ser"er and then recei"es a ser"er I$ address and ser"er port num!er from the ser"erwhich the client then uses to open a data connection from an ar!itrary client port to theser"er I$ address and ser"er port num!er recei"ed.

)yntax: ftp:3367user86:7password89 97host86:7port8937url#path8

SMTP: )imple 0ail +ransfer $rotocol %)0+$& is an Internet standard for electronic mail %e#mail&transmission across Internet $rotocol %I$& networ's. It is an Application ayer protocol in the

()I reference model.

)0+$ uses +2$ port ;


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RIP: +he Bouting Information $rotocol %BI$& is one of the oldest distance#"ector routingprotocols which employs the hop count as a routing metric. BI$ pre"ents routing loops !yimplementing a limit on the num!er of hops allowed in a path from the source to adestination. +he maximum num!er of hops allowed for BI$ is 1


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Que ; Crief the following : a. ) I$ !. $$$

Ans:

a. ) I$: +he )erial ine Internet $rotocol %also )erial ine Interface $rotocol ) I$& is anencapsulation of the Internet $rotocol designed to wor' o"er serial ports and modemconnections. It is documented in B-2 1E


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Que What are congestion? 0ention two algorithms to o"ercome congestion.

Ans: Getwor' congestion occurs when a lin' or node is carrying so much data that its /ualityof ser"ice deteriorates. +ypical e=ects include /ueueing delay pac'et loss or the !loc'ing ofnew connections. A conse/uence of these latter two is that incremental increases in o=eredload lead either only to small increases in networ' throughput or to an actual reduction innetwor' throughput.

Getwor' protocols which use aggressi"e retransmissions to compensate for pac'et loss tend

to 'eep systems in a state of networ' congestion e"en after the initial load has !een reducedto a le"el which would not normally ha"e induced networ' congestion. +hus networ's usingthese protocols can exhi!it two sta!le states under the same le"el of load. +he sta!le statewith low throughput is 'nown as congesti"e collapse.

-or example:

A wireless AG is easily *lled !y a single personal computer

F"en on fast computer networ's %e.g. Miga!it Fthernet& the !ac'!one can easily !econgested !y a few ser"ers and client $2s

+he aggregate transmission from $;$ networ's ha"e no pro!lem *lling an uplin' orsome other networ' !ottlenec'

Denial#of#ser"ice attac's !y !otnets are capa!le of *lling e"en the largest Internet!ac'!one networ' lin's generating large#scale networ' congestion

In telephony networ's %particularly mo!ile phones& a mass call e"ent can o"erwhelmdigital telephone circuits

Slow Start: (ld implementations of +2$ start a connection with the sender inNecting multiplesegments into the networ' up to the window si,e ad"ertised !y the recei"er. Although this is(O when the two hosts are on the same AG if there are routers and slower lin's !etween the

sender and the recei"er pro!lems can arise. )ome intermediate routers cannot handle itpac'ets get dropped and retransmission results and performance is degraded. +he algorithmto a"oid this is called slow start. It operates !y o!ser"ing that the rate at which new pac'etsshould !e inNected into the networ' is the rate at which the ac'nowledgments are returned !ythe other end. )low start adds another window to the senderKs +2$: the congestion windowcalled cwnd. When a new connection is esta!lished with a host on another networ' thecongestion window is initiali,ed to one segment.

Congestion Avoidance : +he assumption of the algorithm is that pac'et loss caused !ydamage is "ery small %much less than 1P&. +herefore the loss of a pac'et signals congestionsomewhere in the networ' !etween the source and destination. +here are two indications ofpac'et loss:

A timeout occurs.

Duplicate A2Os are recei"ed.

2ongestion a"oidance and slow start are independent algorithms with di=erent o!Necti"es.Cut when congestion occurs +2$ must slow down its transmission rate of pac'ets into thenetwor' and in"o'e slow start to get things going again. In practice they are implementedtogether.

2ongestion a"oidance and slow start re/uire that two "aria!les !e maintained for eachconnection:

A congestion window cwnd

A slow start threshold si,e ssthresh

+he com!ined algorithm operates as follows:


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1. Initiali,ation for a gi"en connection sets cwnd to one segment and ssthresh to


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Que @ What do you mean !y ($+I(G GFM(+IA+I(GR? Fxplain with an example.

Ans: All of the D(3D(G+3WI 3W(G+ stu= a!o"e only ser"es to ena!le or disa!le an option.)ome options are only either o= or on in which case the negotiation a!o"e is suScient.

An example would !e the !inary transmission option +BAG)0I+#CIGABT. (thers re/uire thatafter they are ena!led the client and ser"er exchange parameters to control how the optionwor's.

-or example the +FB0IGA #+T$F option re/uires some way for the client to send the ser"erthe name of the terminal. +elnet allows the client and ser"er to send an ar!itrary amount ofdata related to the option using a process called option su!#negotiation.

A de"ice !egins this process !y sending a special se/uence of +elnet protocol commands anddata.

-irst the command )C is sent followed !y the option num!er and parameters as de*ned !ythe particular option the end of the su!#negotiation data is mar'ed !y the protocol command)F. (f course !oth )C and )F must !e preceded !y the U Interpret As Command V %IA2&command !yte.

Wor'ing

+he starting !ase of negotiation is the G5+ capa!ility: each host to !e connected mustagree to this minimum.

F"ery option can !e negotiated !y the use of the four command codes WI W(GK+ D(D(GK+ descri!ed a!o"e.

In addition some options ha"e su!#options: if !oth parties agree to the option they use the)C and )F commands to manage the su!#negotiation.

+o use an option the client and ser"er must negotiate and agree to use it. +he tools fornegotiation are the commands weK"e already tal'ed a!out. (ne side # usually !ut not always

the client # sends a 4WI L4 pac'et %WI is decimal "alue ;


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Que < What is domain name resolution? Discuss the domain name resolution process.

Ans: +he Domain Game )ystem %DG)& is a hierarchical naming system !uilt on a distri!uteddata!ase for computers ser"ices or any resource connected to the Internet or a pri"atenetwor'. 0ost importantly it translates domain names meaningful to humans into thenumerical identi*ers associated with networ'ing e/uipment for the purpose of locating andaddressing these de"ices worldwide. An often#used analogy to explain the Domain Game)ystem is that it ser"es as the phone !oo' for the Internet !y translating human#friendlycomputer hostnames into I$ addresses. -or example the domain name www.example.comtranslates to the addresses 1X;.E. ;.1E %I$"@& and ; ;E:E:;dE:;EE::1E %I$" &. +he DomainGame )ystem ma'es it possi!le to assign domain names to groups of Internet resources andusers in a meaningful way independent of each entityKs physical location. Cecause of thisWorld Wide We! %WWW& hyperlin's and Internet contact information can remain consistentand constant e"en if the current Internet routing arrangements change or the participant usesa mo!ile de"ice. Internet domain names are easier to remem!er than I$ addresses such as;E>. .1>>.1 %I$"@& or;EE1:d!>:1f E::XXX:de>: @>: e> %I$" &. Jsers ta'e ad"antage ofthis when they recite meaningful Jniform Besource ocators %JB s& and e#mail addresseswithout ha"ing to 'now how the computer actually locates them. +he Domain Game )ystemdistri!utes the responsi!ility of assigning domain names and mapping those names to I$addresses !y designating authoritati"e name ser"ers for each domain. Authoritati"e nameser"ers are assigned to !e responsi!le for their particular domains and in turn can assignother authoritati"e name ser"ers for their su!#domains. +his mechanism has made the DG)distri!uted and fault tolerant and has helped a"oid the need for a single central register to !econtinually consulted and updated. In general the Domain Game )ystem also stores othertypes of information such as the list of mail ser"ers that accept email for a gi"en Internetdomain. Cy pro"iding a worldwide distri!uted 'eyword#!ased redirection ser"ice the DomainGame )ystem is an essential component of the functionality of the Internet.

+he domain name resolution process entails:

1. When a DG) name resolution re/uest is forwarded to a DG) ser"er the DG) ser"erexamines its local DG) cache for the I$ address.

;. If the I$ address is not in the DG) ser"erKs cache it chec's its ()+) *le. %)ince the()+) *le is a static text *le it is not commonly used&

. If the DG) ser"er is not authoritati"e and con*gured for forwarding the DG) ser"erforwards the re/uest to a higher#le"el DG) ser"er.

@. If the DG) ser"er cannot forward the re/uest or if forwarding fails the DG) ser"er usesits Boot ints *le %also 'nown as 2ache DG)&. +he Boot int *le lists the 1 root DG)ser"ers.


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Que Discuss the importance of )I$ technology. ist and !rief any four primary functions ofsession initiation protocol.

Ans: +he )ession Initiation $rotocol %)I$& is a standard used in 5oice o"er I$. It is standardi,ed!y the Internet Fngineering +as' -orce %IF+-&. )I$ is a signaling protocol which means that itis not actually responsi!le for transmitting the "oice data rather its purpose is to initiate%hence the name& coordinate and tear down a communication session !etween twoendpoints # peers. 2ompared to a traditional telephone the ringing of a phone the !usy toneand the ending of a call are all functions the )I$ protocol is responsi!le for.

When considering the importance of )I$ it is worth to mention that )I$ is used extensi"ely inthe I$ 0ultimedia )u!system %I0)& that pro"ides multimedia ser"ices in third generation % M&mo!ile phones %I$ 0ultimedia )u!system ;EE &. +his automatically gi"es it some wideindustry support and ensures that it will !e a rele"ant protocol for at least the next 1E years.

)I$ has four 'ey functions pro"ided !y that facilitates "arious interaction capa!ilities. +hin' of)I$ as a !uilding !eing !uilt with di=erent capa!ilities as it is !eing !uilt.

-our primary functions of session initiation protocol

Game mapping and redirection: +his in"ol"es the translation of participants %clientVs&descripti"e naming information to )I$ location information. +his function is one of twowhich occurs during the sessionsV setup.

2apa!ilities negotiation: +his incorporates the second function occurring during sessionsetup. +he "arious media capa!ilities of the participants are determined !y the )I$ inorder to assure appropriate usage of media facilities during the session.

$articipant management: +his )I$ function ena!les participant management !yallowing participants to control the incorporation of new arri"als into a session or thetermination of existing participants during a session. An example of this would !eesta!lishing a conference session and adding additional users to the session so thatthey too can participate in full multimedia session.

2apa!ilities management: )I$ is a!le to monitor the media capa!ilities during a sessionand thus ma'e the appropriate adNustments when necessary. +his dynamic capa!ilitywill adNust the clientVs interaction with other clients !y adNusting the sessiondynamically to reHect a compounded matrix of capa!ilities.

mc0087 internetworking with tcp ip

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