Operation Manual

117 NT/MPRI – Glossary
FTP (File Transfer Protocol)
FTP is a manufacturer-independent file transfer protocol, not specific to
any computer type or operating system. FTP builds directly on TCP, at
Layer 4 (Transport Layer) of the OSI reference model. The protocol is de-
scribed in RFC 959.
ICMP (Internet Control Message Protocol)
ICMP is located at Layer 3 (Network Layer) of the OSI reference model.
It is used for error and information messages (such as information on
routing and call destination addresses). A widely used function based
on ICMP is ping. ICMP builds on the Internet Protocol (IP) as if it were a
higher-layer protocol. Before being sent, ICMP data are always sup-
plied with a complete IP header. The data section that follows the
header contains the ICMP messages.
IP (Internet Protocol)
Within the TCP/IP protocol family, IP is responsible for relaying data. In
general, it has the function of regulating data transmission between
different networks. IP’s tasks include:
l data packet service
l fragmentation of data packets
l selection of transmission parameters
l addressing function
l routing between networks
l specification of higher protocols
IP does not provide a secure connection (no end-to-end control); it de-
pends on the protocols of the higher levels. This means that lost or re-
jected data packets cannot be regenerated and re-transmitted. The IP
also is not concerned with delivering data packets to the recipient in
the correct order. This is the responsibility of the transport layer (Layer
4) of the OSI reference model.
IP builds directly on Layer 3 (Data Link Layer/Security Layer) of the OSI
reference model. The protocol is defined in RFC 791.
ntmpri-e.book Seite 117 Donnerstag, 28. Februar 2002 11:26 11