TMS zl Management and Configuration Guide ST.1.1.100226

B-30

Glossary

SYN flood A DoS attack in which the attacker sends a rapid succession of SYN (synchro-

nize) packets to the targeted system. The attack is intended to disrupt the

normal TCP three-way handshake in which a SYN packet sent by a client is

followed by a SYN-ACK (acknowledge) packet from the server, to which the

client should respond with an ACK packet. When the server does not receive

the ACK packet, its connections remain half-opened, which prevents legiti-

mate clients from making a connection.

syslog A client/server protocol that is used to send log messages from network

devices to a syslog server.

syslog server A server that receives and stores syslog messages from network devices.

TCP Transmission Control Protocol. Part of the IP protocol suite, TCP allows

applications on networked hosts to create connections to one another and

exchange data. TCP guarantees reliable and in-order data delivery. TCP pro-

tocols include, among many others, HTTP, email, and SSH. For more informa-

tion about TCP, see Request for Comments (RFC) 793 (at http://www.ietf.org/

rfc/rfc0793.txt).

threat level One of five, preconfigured categories that indicates the severity of an attack.

The threat levels are Critical, Severe, Minor, Warning, Informational.

timeout The amount of time the firewall will keep a session open without packets being

exchanged.

TLS Transport Security Layer. The successor to SSL, TLS is a protocol that

provides secure communications through encryption and endpoint

authentication.

TMS OS Threat Management Services operating system. The application that pro-

vides threat management services on the zl module.

TMS VLAN A VLAN that has been associated with a zone on a TMS zl Module in routing

mode.

tools A column in many TMS zl Web browser interface windows that contains some

or all of the following: move icon, to move the entry to a higher or lower

position; edit icon, to edit the entry; delete icon, to delete the entry.

ToS Type of Service. Now called Differentiated Services.

traffic selector Traffic that is allowed over the IPsec SA (VPN tunnel).