Information Technology Reference
In-Depth Information
Examples of network layer specifications are
Protocols
■
IPv4, IPv6
■
ICMP
■
ARP
■
Connectionless Network Protocol (CLNP)
■
Routing protocols
■
Routing Information Protocol (RIP)
■
Open Shortest Path First (OSPF)
■
Enhanced Interior Gateway Routing Protocol (EIGRP)
■
Intermediate System-to-Intermediate System (IS-IS)
■
Tr a n s p o r t L ay e r ( O S I L ay e r 4 )
The transport layer provides reliable, transparent transport of data segments from upper
layers. It provides end-to-end error checking and recovery, multiplexing, virtual circuit
management, and flow control. Messages are assigned a sequence number at the transmis-
sion end. At the receiving end, the packets are reassembled, checked for errors, and ac-
knowledged. Flow control 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
Tran s mis s ion Cont rol P rotocol (TCP)
■
Real-Time Transport Protocol (RTP)
■
User Datagram Protocol (UDP)
■
Note:
Although UDP operates in the transport layer, it does not perform the reliable
error-checking functions that other transport layer protocols do.
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. Com-
munication sessions consist of service requests and responses that occur between applica-
tions on different devices.
Examples of specifications that operate at the session layer are
DECnet's Session Control Protocol (SCP)
■
H.245 and H.225
■
