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Cisco Router and Security Device Manager Version 2.2 User’s Guide
OL-4015-08
Glossary
subnet, subnetwork In IP networks, a network sharing a particular subnet address. Subnetworks are
networks arbitrarily segmented by the network administrator in order to provide
a multilevel, hierarchical routing structure while shielding the subnetwork from
the addressing complexity of attached networks. See also IP address, subnet bits,
subnet mask.
subnet bits
subnet mask
32-bit address mask used in IP to indicate the bits of an IP address that are being
used for the network and optional subnet address. Subnet masks are expressed
in decimal. The mask 255.255.255.0 specifies that the first 24 bits of the address
Sometimes referred to simply as mask. See also address mask and IP address.
symmetric key A symmetric key is used to decrypt information that it previously encrypted.
T
T1 A T1 link is a data link capable of transmitting data at a rate of 1.5 MB per
second.
TACACS+ Terminal Access Controller Access Control System plus. An access server
authentication and accounting protocol that uses TCP as the transport protocol.
tail-end The downstream, receive end of a tunnel.
TCP Transmission Control Protocol. Connection-oriented transport layer protocol
that provides reliable full-duplex data transmission.
TCP Syn Flood
Attack
A SYN-flooding attack occurs when a hacker floods a ser ver with a barrage of
requests for connection. Because these messages have unreachable return
addresses, the connections cannot be established. The resulting volum e of
unresolved open connections eventually overwhelms the server and can cause it
to deny service to valid requests, thereby preventing legitimate users from
connecting to a website, accessing e-mail, using FTP service, and so on.
Telnet A terminal emulation protocol for TCP/IP networks such as the Internet. Telnet
is a common way to control web servers remotely.
TFTP Trivial File Transfer Protocol. TFTP is a simple protocol used to transfer files.
It runs on UDP and is explained in depth in Request For Comments (RFC) 1350.