Application
(Layer 7) This
layer supports application and end-user processes. Communication partners are
identified, quality of service is identified, user authentication and privacy
are considered, and any constraints on data syntax are identified. Everything
at this layer is application-specific. This layer provides application services
for file transfers, e-mail, and other network software services. Telnet and FTP
are applications that exist entirely in the application level. Tiered
application architectures are part of this layer.
Presentation
(Layer 6) This
layer provides independence from differences in data representation (e.g.,
encryption) by translating from application to network format, and vice versa.
The presentation layer works to transform data into the form that the
application layer can accept. This layer formats and encrypts data to be sent
across a network, providing freedom from compatibility problems. It is
sometimes called the syntax layer.
Session
(Layer 5) This
layer establishes, manages and terminates connections between applications. The
session layer sets up, coordinates, and terminates conversations, exchanges,
and dialogues between the applications at each end. It deals with session and
connection coordination.
Transport
(Layer 4) This
layer provides transparent transfer of data between end systems, or hosts, and
is responsible for end-to-end error recovery and flow control. It ensures
complete data transfer.
Network
(Layer 3) This
layer provides switching and routing technologies, creating logical paths,
known as virtual circuits, for transmitting data from node to node. Routing and
forwarding are functions of this layer, as well as addressing, internetworking,
error handling, congestion control and packet sequencing.
Data Link
(Layer 2) At
this layer, data packets are encoded and decoded into bits. It furnishes
transmission protocol knowledge and management and handles errors in the
physical layer, flow control and frame synchronization. The data link layer is
divided into two sub layers: The Media Access Control (MAC) layer and the
Logical Link Control (LLC) layer. The MAC sub layer controls how a computer on
the network gains access to the data and permission to transmit it. The LLC
layer controls frame synchronization, flow control and error checking.
Physical
(Layer 1) This
layer conveys the bit stream – electrical impulse, light or radio signal —
through the network at the electrical and mechanical level. It provides the
hardware means of sending and receiving data on a carrier, including defining
cables, cards and physical aspects. Fast Ethernet, RS232, and ATM are protocols
with physical layer components.
Source = Gargas
0 comments:
Post a Comment