Khamis, 6 Disember 2012

osi model

Upper  layer

application


presentation



session



Transport    
Segment (host)





                                                                                              }seperate
Down layer

Network       
Packet (router)

Data link       

Frame (switch)


physical        
Bits (hub)









Physical layer(bits)layer 1
·        The digit only used 1(one)or a 0(zero)
·        Each digit called 1 bit(binary digit)
·        If(1) count that value
·        If (0) dont count that value
·        Physical layer is look like an audio tones(volume up/down)
·        Nibble use 4 bits /bytes use 8 bits
·        Last byte value is 255 /nibble value is 15
·        The nibble value use to convert bits to another value                     :binary(0,1bits),decimal(0,2,4,8bits),hexadecimal(0-9bits)

Now we going BACK to school to study this chapter....(form 1)
Given>
Bytes:128 64 32 16 8 4 2 1 (1 1 1 1 1 1 1 1)→it have 8bits
Nible:8 4 2 1 (1 1 1 1)→it have 4 bits


Eg:how to change binary value to decimal value
     This is byte value: 11111111(8 bits)= 128+64+32+16+8+4+2+1←          ADD
                                                                     =255 BYTES
                               IF :10010110(8 bits)=128+16+4+2
                                                                    =150 BYTES

     This is nible value:1111(4 bits)=8+4+2+1← ADD
                                                           =15BYTES
                                    IF:1010(4 bits)=8+2
                                                           =10BYTES

Eg:how to change binary value to hexadecimal value

First make the table :example we take nible value 10bytes

TABLE 1.1
Hex value
                  Binary  value

Decimal value
0
                         0000

          0
1
                         0001

          1
2
                         0010

          2
3
                         0011

          3
4
                         0100

          4
5
                         0101

          5
6
                         0110

          6
7
                         0111

          7
8
                         1000

          8
9
                         1001

          9
a
                         1010

         10
Formula: genap (x +)
Ganjil(+)






Given binary:01101010

Seperate       :0110=6 <<seperate!! >>1010=a (look at the table 1.1)
Answer=Hexadecimal:0x6a  (0x symbol for hexadecimal)
                              Nible:4 bits
                        Decimal:64+16+4+1=85bytes


Ok... now we going to another layer...lets go....!! :)



Data link(framing) layer 2
·        Combines bits into bytes and bytes into frame
·        Handle error reporting,
·        Handle network topologies
·        Flow control
·        Translate message into bits( physical layer)to transmit
·        Provides access to media using MAC address(pc address)and LLC
(a system to tell the stupid switch what to do)
Ok thats all for layer 2.... *_* hehe

Network(packet)layer 3
·        Provide reliable or unreliable delivery
·        Perform error correction before retransmit
·        Provide a single network interface to upper-layer
·        It takes care of the addressing of host by giving them ip address
 This is simple answer for down layer(COZ everyone LIKE SIMPLE NOT PIMPLE)....next time i will told you about UPPER LAYER AND IP ADDRESS(ROUTING)...TQ,...

Selasa, 6 November 2012

basic network technology


WHAT IS A NETWORK?
A network can consist of two computer connected together on a desk or it can consist of many LOCAL  AREA NETWORKS(LAN) conected together  to form a WIDE AREA NETWORK(WAN).all types of networking require special networking software to allow different computers to communicate will each other.
EXAMPLE  OF AREA NETWORK TYPE:
LAN: local area network
WAN: wide area network
MAN: metropolitan area network
WLAN: wireless local area network
SAN: storage area network,system area network.  
CAN: campus area network  
 
LAN(local area network)
 LAN connects  networking devices with in short spam of area ex:small office,home,internet cafe. Etc,LAN  uses TCP/IP network protokol for communication between computers.it is often but not always implemented as a single IP subnet.
WAN(wide area network)
WAN cover large distance for communication between computer.the internet itself is the biggest example of wide area network.WAN is distributted of geographically y LANs.a network connecting device router connects  LANs to WANs.WAN used network protocol like ATM,X.25,and frame relay for long distance connectivity.  
 
MAN(METROPOLITAN AREA NETWORK)    
MAN importance for some government bodies and organization on larger scale. MAN falls in middle of LAN and WAN ,it cover large span of physical area LAN but smaller than WAN,such as a city.
WLAN(wireless local area network)
 WLAN based on wireless network technology mostly referred as wi-fi unlike LAN,in WLAN no wires are used,but radio signal are the medium for communication.wireless network card are required to be installed in the system for accessing any wireless network around.mostly wireless card connect to wireless routers  for communication among computer  or accessing WAN,internet.
SAN(storage area network)
SAN technology is used  for data storage and it has no use for most of the organization but data oriented organization.STORAGE AREA NETWORK connects server to data storage  devices by using fiber channel technology.
SAN(system area network)
SYSTEM AREA NETWORK are also known as cluster area network and it connect high performance computers with high speed connections in cluster configuration.
CAN(campus area network)
Networking spanning with multiple LANs but smaller than a metropolitan area network(MAN)This kind of network  mostly used in relatively large universities or local business offices and buildings.

NETWORK TOPOLOGY
Network topology refers to the way in which the conections within the network are made.there are two types of topology:
-physical topologies
-logical topologies
PHYSICAL TOPOLOGIES
The physical topology is how the computer and peripheral are connected and how the cable is run between them,in other word the way the networks look.
THE THREE COMMON PHYSICAL TOPOLOGIES FOR LOCAL AREA NETWORK ARE:
-STAR
-RING
-BUS
OTHER LESS COMMON PHYSICAL TOPOLOGIES INCLUDE:
-TREE
-MESH
LOGICAL TOPOLOGIES
The logical topologies describes the way in which a network transmit informations from one node to the next node.
THE MOST COMMON LOGICAL TOPOLOGIES ARE:
-BUS
-RING
STAR TOPOLOGY
In a star network ,each terminal is directly  connected to a central hub.each connection is independent  of all other connection.a twisted-pair cable is common for configuration,but coaxial or fiber optic cable may also be used
.
Advantages
-easy to install
-if one nodes fails,other nodes will not effected
-data transfer between the central server and the nodes is relatively low,therefore a low cost cable      like twisted-pair cable can be used to connect the nodes to the server.
Disadvantages
-if the hub fails then all nodes attached will go down.
-requires more cable than most of the other topologies.
-a central connecting device allows for a single point of failure.
-more difficult than other topologies to impliment.

RING TOPOLOGY
In this type of network  each node is connected to the one on either side of it so that they form a ring.data travel from one node to the next until it reaches its destination.each node is responsible for capturing data addressed to it or for transmitting the data to the next node by way of a signal.coaxial and fiber optic cables are commonly used for this type of network.twisted-pair cables provide a bit rate of up to 16 Mbps.
Advantages
-all nodes on the network have an equal chance of transmitting data.
-cable fault are easy located,makin troubleshooting easier.
-moderately easy to install
Disadvantages
-failure of one node will result in a shutdown of all other nodes
-difficult to add or delete nodes because of the physical layout
-signal may get lost

BUS TOPOLOGY
In a bus network all nodes on the network share a common cable which is terminated at each end.transmission is passed back and forth along the cable.as messages pass,each node checks the destination address and accepts the messages if the adress matches the node adress.
Advantages
-If one node crashes it will have no effect on the rest of the network.
-does not use any specialized network equipment.
-requires less cable than other topologies.
Disadvantages
-a fault on the cable will disable the whole network
-difficult to troubleshoot
-all system on the network connect to a single backbone,a break in the cable will prevent all system from accessing the network.
-require a network protocol to detect when two nodes are transmitting at the same time.

THE OSI MODEL (IMPORTANT THING IN THE NETWORK!!)
 Open sytem interconnection(OSI)model:
Divide network communication into seven layer:
OSI MODEL
FUNCTION
APPLICATION(7)
PROVIDE A USER INTERFACE
PRESENTATION(6)
PRESENT DATA
HANDLE PROCESSING SUCH AS ENCRYPTION
SESSION(5)
KEEP DIFFERENT APPLICATIONS
DATA SEPARATE
TRANSPORT(4)
PROVIDE RELIABLE OR UNRELIABLE DELIVERY
PERFORM ERROR CORRECTION BEFORE RETRANSMIT
NETWORK (3)
PROVIDE LOGICAL ADRESS
WHICH ROUTERS USE FOR PATH DETERMINATION
DATA LINK (2)
COMBINE PACKETS INTO BYTES AND BYTES INTO FRAMES
PROVIDES ACCESS TO MEDIA USING MAC ADDRESS
FIND ERROR DETECTION NOT CORRECTION
PHYSICAL  (1)
MOVES BITS BETWEEN DEVICES
SPECIFIES VOLTAGE
WIRE SPEED
PIN-OUT OF CABLES