Rahul Khadse
Network is the method to share hardware resources and software resources. We can share the resources with the help of operating system like windows, Linux, UNIX etc. To connect multiple networks we have to use internetworking devices like router, bridge,layer 3, switches etc.
Administrator model for networking
If NIC are different then use bridge. If media is different then use Trans-Receive devices.
OSI (Open Systems Interconnection) Model
OSI model is the layer approach to design, develop and implement network. OSI provides following advantages: -
(i) Designing of network will be standard base.
(ii) Development of new technology will be faster.
(iii) Devices from multiple vendors can communicate with each other.
(iv) Implementation and troubleshooting of network will be easy.
(1) Application Layer: - Application layer accepts data and forward into the protocol stack. It creates user interface between application software and protocol stack.
(2) Presentation Layer: -This layer decides presentation format of the data. It also able to performs other function like compression/decompression and encryption/decryption.
(3) Session Layer: - This layer initiate, maintain and terminate sessions between different applications. Due to this layer multiple application software can be executed at the same time.
(4) Transport Layer: - Transport layer is responsible for connection oriented and connection less communication. Transport layer also performs other functions like
(i) Error checking
(ii) Flow Control
Buffering
Windowing
Multiplexing
(iii) Sequencing
(iv) Positive Acknowledgement
(v) Response
Connection Oriented Communication
Connection less Communication
Sender =======> Receiver
(i) Error checking -- Transport layer generates cyclic redundancy check (CRC) and forward the CRC value to destination along with data. The other end will generate CRC according to data and match the CRC value with received value. If both are same, then data is accepted otherwise discard.
(ii) Flow Control -- Flow control is used to control the flow of data during communication. For this purpose following methods are used: -
(a) Buffer - Buffer is the temporary storage area. All the data is stored in the buffer memory and when communication ability is available the data is forward to another.
(b) Windowing - Windowing is the maximum amounts of the data that can be send to destination without receiving Acknowledgement. It is limit for buffer
to send data without getting Acknowledgement.
(iii) Sequencing --Transport layer add sequence number to data, so that out of sequence data can be detected and rearranged in proper manner.
(iv) Positive Acknowledgement and Response -- When data is send to destination, the destination will reply with Acknowledgement to indicate the positive reception of data. If Acknowledgement is not received within a specified time then the data is resend from buffer memory.
(5)Network Layer -- This layer performs function like logical addressing and path determination. Each networking device has a physical address that is MAC address. But logical addressing is easier to communicate on large size network.
Logical addressing - Defines network address and host address. This type of addressing is used to simplify implementation of large network. Some examples of logical addressing are: - IP addresses, IPX addresses etc.
Path determination - Network layer has different routing protocols like RIP, EIGRP, BGP, and ARP etc. to perform the path determination for different routing protocol. Network layer also perform other responsibilities like defining quality of service, fragmentation and protocol identification.
(6) Data Link Layer - The functions of Data Link layer are divided into two sub layers
(i) Logical Link Control
(ii) Media Access Control
(i) Logical Link Control defines the encapsulation that will be used by the NIC to delivered data to destination. Some examples of Logical Link Control are ARPA (Ethernet), 802.11 wi-fi.
(ii) Media Access Control defines methods to access the shared media and establish the identity with the help of MAC address. Some examples of Media Access Control are CSMA/CD, Token Passing.
(7) Physical Layer - Physical Layer is responsible to communicate bits over the media this layer deals with the standard defined for media and signals. This layer may also perform modulation and demodulation as required.
Device at different Layers
Physical Layer Devices
Hub,Modem,Media,DCE (Dtat Comm Equipment), CSU/DSU.Repeater,Media Converter.
Data Link Layer
NIC, Switch, Bridge
Network Layer Device
Router, Layer 3 Switch
All Layers Device
PC, Firewall
DCE: - DCE convert the bits into signal & send them on media.
FDDI – Fiber Distributed Data Interface
Switch forwards frames on the base of MAC address.
Router forwards packets on the base of IP address.
Administrator model for networking
Server software: - which software are used to giving services that are server software.
Client software: - which gets servicesIf NIC are different then use bridge. If media is different then use Trans-Receive devices.
OSI (Open Systems Interconnection) Model
OSI model is the layer approach to design, develop and implement network. OSI provides following advantages: -
(i) Designing of network will be standard base.
(ii) Development of new technology will be faster.
(iii) Devices from multiple vendors can communicate with each other.
(iv) Implementation and troubleshooting of network will be easy.
(2) Presentation Layer: -This layer decides presentation format of the data. It also able to performs other function like compression/decompression and encryption/decryption.
(3) Session Layer: - This layer initiate, maintain and terminate sessions between different applications. Due to this layer multiple application software can be executed at the same time.
(4) Transport Layer: - Transport layer is responsible for connection oriented and connection less communication. Transport layer also performs other functions like
(i) Error checking
(ii) Flow Control
Buffering
Windowing
Multiplexing
(iii) Sequencing
(iv) Positive Acknowledgement
(v) Response
Connection Oriented Communication
Sender =======> Receiver
(i) Error checking -- Transport layer generates cyclic redundancy check (CRC) and forward the CRC value to destination along with data. The other end will generate CRC according to data and match the CRC value with received value. If both are same, then data is accepted otherwise discard.
(ii) Flow Control -- Flow control is used to control the flow of data during communication. For this purpose following methods are used: -
(a) Buffer - Buffer is the temporary storage area. All the data is stored in the buffer memory and when communication ability is available the data is forward to another.
(b) Windowing - Windowing is the maximum amounts of the data that can be send to destination without receiving Acknowledgement. It is limit for buffer
to send data without getting Acknowledgement.
(iii) Sequencing --Transport layer add sequence number to data, so that out of sequence data can be detected and rearranged in proper manner.
(iv) Positive Acknowledgement and Response -- When data is send to destination, the destination will reply with Acknowledgement to indicate the positive reception of data. If Acknowledgement is not received within a specified time then the data is resend from buffer memory.
(5)Network Layer -- This layer performs function like logical addressing and path determination. Each networking device has a physical address that is MAC address. But logical addressing is easier to communicate on large size network.
Logical addressing - Defines network address and host address. This type of addressing is used to simplify implementation of large network. Some examples of logical addressing are: - IP addresses, IPX addresses etc.
Path determination - Network layer has different routing protocols like RIP, EIGRP, BGP, and ARP etc. to perform the path determination for different routing protocol. Network layer also perform other responsibilities like defining quality of service, fragmentation and protocol identification.
(6) Data Link Layer - The functions of Data Link layer are divided into two sub layers
(i) Logical Link Control
(ii) Media Access Control
(i) Logical Link Control defines the encapsulation that will be used by the NIC to delivered data to destination. Some examples of Logical Link Control are ARPA (Ethernet), 802.11 wi-fi.
(ii) Media Access Control defines methods to access the shared media and establish the identity with the help of MAC address. Some examples of Media Access Control are CSMA/CD, Token Passing.
(7) Physical Layer - Physical Layer is responsible to communicate bits over the media this layer deals with the standard defined for media and signals. This layer may also perform modulation and demodulation as required.
Physical Layer Devices
Hub,Modem,Media,DCE (Dtat Comm Equipment), CSU/DSU.Repeater,Media Converter.
Data Link Layer
NIC, Switch, Bridge
Network Layer Device
Router, Layer 3 Switch
All Layers Device
PC, Firewall
DCE: - DCE convert the bits into signal & send them on media.
FDDI – Fiber Distributed Data Interface
Switch forwards frames on the base of MAC address.
Router forwards packets on the base of IP address.
Posted in: CCNA
