Information Technology Reference
In-Depth Information
manages the data transmission to ensure that the transmitting device does not send more data
than the receiving device can process.
Examples of transport layer specifications are the following:
•
Transmission Control Protocol (TCP)
•
Real-Time Transport Protocol (RTP)
•
Sequenced Packet Exchange (SPX)
•
AppleTalk's Transaction Protocol (ATP)
•
User Datagram Protocol (UDP) (provides unreliable transport at this layer with less
overhead than TCP)
Session Layer (OSI Layer 5)
The session layer provides a control structure for communication between applications. It
establishes, manages, and terminates communication connections called sessions. Communi-
cation sessions consist of service requests and responses that occur between applications on dif-
ferent devices. The management of sessions involves the synchronization of dialog control by
using checkpoints in the data stream.
Examples of specifications that operate at the session layer are the following:
•
NetBIOS
•
Real-Time Control Protocol (RTCP)
•
Session Control Protocol (SCP)
•
AppleTalk's Zone Information Protocol (ZIP)
•
DECnet's Session Control Protocol (SCP)
•
H.323, H.245, H.225
•
Real-Time Control Protocol (RTCP)
Presentation Layer (OSI Layer 6)
The presentation layer provides data representation with a variety of coding and conversion
functions. These functions ensure that data sent from a sending application on one system is
readable by the application layer on another system. This layer provides the conversion of
character representation formats, data compression schemes, and encryption schemes. Voice
coding schemes are specified at this layer.
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