These datagrams are also encapsulated in PPP data units (frames).X2 Review
At this point it is interesting to note
that applications that work at a certain level or layer only communicate with
their peers in remote systems, that is (for example), at the application level,
the browser can only be understood with the web server, not caring at all how
the information gets to it. This same principle is used for the rest of
the layers. Have you ever wondered what happens when you request a web
page? It is a good example to more clearly illustrate the concept of
layers or levels: the browser makes an HTTP request, a request that is included
in a TCP packet, which in turn is encapsulated and fragmented into one or more
datagrams (data unit to network level) IP. These datagrams are also
encapsulated in PPP data units (frames), which are sent to your Internet
provider, after passing through the modem, which transforms such digital
data units into acoustic signals according to a certain standard (V. 34bis or
V. 90, for example). Your ISP will assemble the PPP packets to convert
them back into IP datagrams, which are taken to their destination, where they
will be decoded in the opposite direction to that performed on our equipment,
until they reach the "application level", which is the web server.
From what has been stated here, we must
stay with three main ideas. In the first place, that TCP / IP operates
only at the higher levels of the network, being indifferent to the set of
protocols that are understood with the network adapters (physical connection:
Ethernet, Token-Ring, ARCNet, ATM, etc.) that are found under . Second,
that IP is a datagram protocol that provides a standard interface to higher
protocols and, finally, that within these higher protocols we can include TCP
and UDP, which offer additional features that certain network applications
need.
The IP protocol
IP is a simple, easily implementable
protocol of small units of data or datagrams, which provides a standard
interface from which the rest of the protocols and services can be built,
without having to worry about the differences that exist between the different
subnets. through which the data circulates.