Computer Networks
Marwan Al-Namari
Week 4
7 Layers
OSI Layer Communication
OSI 7-Layer Model logical view
Physical Path
ApplicationApplication
PresentationPresentation
SessionSession
TransportTransport
NetworkNetwork
Data LinkData Link
PhysicalPhysical
ApplicationApplication
PresentationPresentation
SessionSession
TransportTransport
NetworkNetwork
Data LinkData Link
PhysicalPhysical
Physical Medium
Logical Path
The interaction between layers in the OSI model
EncapsulationEach layer add its own header (and maybe trailer ) to the portion of the packet and pass it to the next layer without knowing which part is data and header( and maybe trailer ).it treat it as one integral unit. The concept is called encapsulation.In the way back each layer will take-off the header ( and maybe trailer ) from the incoming packet and pass it to the next layer . The concept is called decapsulation.
Packet Components
The Complete Packet
Cyclical Redundancy Check
Packet Creation Process
OSI vs. TCP/IP Model
TCP/IP standardsThe Internet Engineering Task Force (IETF) is the body that defines standard internet operating protocolsThese standards are specified in documents called RFCs ( Requests for comments)
e.g. RFC 821 is about SMTP ( e-mail) protocols
TCP/IPTCP/IP : Transmission Control Protocol /Internet Protocol.It is a suite of protocols providing communications in a heterogeneous environment.It is used for interoperability among many different types of computers.Almost all networks support TCP/IP.Support routing.Used as internetworking protocol.
Other Protocols in the SuiteThese protocols were written specifically for TCP/IP:SMTP(Simple Mail Transfer Protocol) : EmailFTP (File Transfer Protocol) : For exchanging files .SNMP(Simple Network Management Protocol) :Network Management.
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