based on info from http://en.wikipedia.org/wiki/X.25

answer= d... since X.25 is a protocol suite for connecting
WANs and spans across the first 3 layers

a

Digital Subscriber Line (dsl) allows us to transmit voice,
data, video e.t.c simultanious on the same existing
telephone lines. in short DSL allows us to use both
telephone and internet simultaniously,

 service provider only provides the dsl modem as a part of
installation 
DSL is 20times faster than ordinary telephone and 10 times
faster than ISDN

DSL (Digital Subscriber Line) is a set of standards for 
broadband network connectivity over normal telephone lines

We can see OS in the system from SYSTEM PROPERTISE wizard.

Right Click on MY COMPUTER - PROPERTIES - On GENERAL tab, 
we can get all information about system OS, OS version. 
Hardware information, just like CPU speed, RAM size

Your question is actually asked in an incorrect format. 
There is really only a difference between FTP & HTTP 
protocols. However, both protocols are part of the TCP/IP 
suite. So in reality FTP and HTTP are 2 different 
protocols, as FTP is a a file transfer protocol opposed to 
HTTP which is hyper-text (a hyper text transfer protocol).

HTTP - Hper text transfer protocol is used for websites.
(External)
TCP/IP - Transmission control protocol/Internet protocol is 
used for access internet connection.

fluctate the screen
opening of unwanted ports
in/out of cd rom without any commond
restart system again and again..

Viruses are malicious set of programes that infeccts the 
compuuter with all the known evils.Proper antivirus 
software are a means of defence to them. apart from that 
IDS and IPS plays an important role. also correct security 
policys anf firewall should be created to stop unauthoriged 
netwrk traffic to travers the network , conastant 
monitoring of SNMP v3 should be done

Screening Router

Dual-homed Host 

Screened Host 

Screened Subnet 

Internal Firewall 

Personal Firewall

it means someone tried to hack the security of the network.

Major components of a  UTM(Unified Threat Management) 
firewall appliance are
1. Anti-Spam
2. Anti-Virus
3. IDP/IDS
4. VPN
5. Content Filtering