Page 172 - CISSO_Prep_ Guide

ensures the data is in a format that can be transmitted over a
network and understood by the system at the far end.

Presentation - this layer is used for protocol conversion and
compression-decompression of the data.

Session - this layer manages the session between the two
endpoints - login, authentication, and identifying the packets of
information according to each session.

Transport - this layer manages the end to end transmission of the
data. TCP ensures that all packets are received. When using
UDP, the transport layer enables fast, low-overhead
communications but without any form of error control or proof
of delivery.

Network - the network layer moves data across networks with
the best-effort approach. The most common protocol used here
is IPv4, which places a 32-bit address on the packet to enable
routing the packet across the network. Over the next few years,
IPv4 will be replaced with IPv6 - with a 128-bit address space.
Currently, IPv6 has a limited deployment - mostly being used
for backbones and another inter-ISP routing.

Datalink - this layer connects two physically adjacent devices -
it provides the interface between logical and physical addressing
(Ethernet addresses, for example).

Physical - The physical media is the actual manner of
connecting adjacent devices over various types of media -
wireless, fiber, copper, etc.