User's Guide

Table Of Contents
254
MTU. Maximum Transmission Unit. The maximum packet size,
in bytes, that can be sent over a network interface.
MULTI-LAYER. The Open System Interconnection (OSI) model
divides network traffic into seven distinct levels, from the Physi-
cal (hardware) layer to the Application (software) layer. Those in
between are the Presentation, Session, Transport, Network,
and Data Link layers. Simple first and second generation fire-
wall technologies
inspect between 1 and 3 layers of the 7 layer
model, while our SMLI engine inspects layers 2 through 7.
-----N-----
NAK. Negative acknowledgment. See ACK.
Name. The Name parameter refers to the name of the config-
ured tunnel. This is mainly used as an identifier for the adminis-
trator. The Name parameter is an ASCII and is limited to 31
characters. The tunnel name is the only IPSec parameter that
does not need to match the peer gateway.
NCP. Network Control Protocol.
Negotiation Method. This parameter refers to the method
used during the Phase I key exchange, or IKE process. SafeHar-
bour supports Main or Aggressive Mode. Main mode requires 3
two-way message exchanges while Aggressive mode only
requires 3 total message exchanges.
null modem. Cable or connection device used to connect two
computing devices directly rather than over a network.