In article <(E-Mail Removed)> , "esara"
(E-Mail Removed) says...
> Hi
> I am trying to understand OSI layers. Now what I understood is this
> if I want to connect a computer to internet or to other computer and
> if I want to follow the OSI model them each of OSI model is either
> software or hardware. So If I want to send an email to other computer
> then I need a software that help me to write that email (this is
> application layer) then at some point I need to send this message to
> destination, then I need to implement the "Network Layer" and the
> Router (which is the Hardware will do this job), and if the network
> has a switch or hub (Hardware) then this network is implementing "Data
> Link" Layer so the email will use this layer (hardware) to go to other
> side. Is that good understanding??
Not really. The OSI 7-layer model was developed in an attempt to
provide a standard framework for network communication - it's a
theoretical arrangement of the functions that must be performed on data
to transport it across a network. If you send data from one computer to
another then a program (e.g. a web server) puts it in the top of the
stack, it travels down through the layers with various transformations
and checks possibly performed at each stage, then at the other end it
will travel back up again until it's available to a program (e.g. a web
browser). The operating system provides something like the Berkeley
sockets API that let you connect a program to the top of the stack, and
the cable attached to the network card is the interface at the bottom of
the stack. Devices like switches and routers don't need to provide a
full stack - they don't use the data, just move it around, so for
instance a repeater only needs the physical layer - all it does is
receive electrical signals on one port and repeat them to another port,
while a router also needs the data link and network levels - it has to
read the address of a packet and send it off in the right direction.
Linear Mode
