Hitachi US7070447-001 - Manual (Page 37)

Fundamentals of Networking
Doc Part Number, Version Number 5-3
Draft Level—Hitachi Confidential
The LLC sublayer defines the logical connection to the upper layer
services based on a socket or Service Access Point (SAP). This allows two
processes on the same network to maintain a “logical connection” with
each other for the purpose of data exchange.
Examples of Layer 2 devices are bridges and switches.
Layer 3: Network Layer
This layer is where the network provides its routing functionality. The
Network Layer uses a packet to transport data from one network to another.
A 32-bit address is used to define the network’s logical location and is
referred to as the network address or IP address.
Examples of Layer 3 devices are routers.
Layer 4: Transport Layer
This layer ensures reliable delivery of data between networks. All error
checking, acknowledgments, retransmissions, and data sequencing are
handled by the Transport Layer.
Layer 5: Session Layer
This layer provides for the ability for two processes on two different
stations to form a connection for the purpose of communication with one
another. This is often referred to as a dialogue layer. Host-to-host
communication is established, managed, and terminated at this layer.
Layer 6: Presentation Layer
This layer converts the actual data that is being transferred into a readable
and proper form.
Layer 7: Applications Layer
This layer provides network-based services to a user’s application. The
application layer communicates with the end user via programs such as file
transfers (FTP, TFTP), electronic mail (SMTP), and other applications.