Alcatel Omni Switch/Router, Руководство пользователя

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IP Routing Overview
Page 25-3
Transport Protocols
IP is both connectionless (it routes each datagram separately) and unreliable (it does not
guarantee delivery of datagrams). This means that a datagram may be damaged in transit, or
thrown away by a busy router, or simply never make it to its destination. The resolution of
these transit problems is to use a layer 4 transport protocol:
• Transmission Control Protocol (
TCP
)—A major data transport mechanism that provides reli-
able, connection-oriented, full-duplex data streams. While the role of
TCP
is to add reliabil-
ity to IP,
TCP
relies upon IP to do the actual delivering of datagrams.
• User Datagram Protocol (
UDP
)—A secondary transport-layer protocol that uses IP for deliv-
ery. However,
UDP
is not connection-oriented so it does not provide reliable end-to-end
delivery of datagrams. But some applications can safely use
UDP
to send datagrams that
don’t require the extra overhead added by
TCP
.
Application-Layer Protocols
• Bootstrap Protocol (
BOOTP
)/Dynamic Host Configuration Protocol (
DHCP
)—May be used
by an end station to obtain an IP address. The switch provides a
UDP
relay that allows
BOOTP
requests/replies to cross different networks. See Chapter 26, “UDP Forwarding.”
• Simple Network Management Protocol (
SNMP
)—Used to manage nodes on a network.
SNMP
is discussed in Chapter 13, “Configuring SNMP.”
• Telnet—Used for remote connection to a device. The
telnet
command is described in this
chapter.
• File Transfer Protocol (
FTP
)—Enables transferring files between hosts.
Additional IP Protocols
• Internet Control Message Protocol (
ICMP
)—Specifies the generation of error messages, test
packets, and informational messages related to IP.
ICMP
supports the
ping
command used
to determine if hosts are online.
• Address Resolution Protocol (ARP)—Used to find the IP address that corresponds to a
given physical (
MAC
) address.
• Internet Group Management Protocol (IGMP)—Tracks multicast group membership. See
the Multicast Services section of the Advanced Routing User Manual .
• Resource ReSerVation Protocol (RSVP)—Signals Quality of Service (QoS) requests in an IP
network. For more information, see the Switched Network Services User Manual .