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Introduction
1-6 Software Conventions
Subnet
A physical network within the IP network.
Subnet mask
A 32-bit quantity (four binary octets) that filters a destination IP address to
determine whether it exists on the source IP’s subnetwork and therefore can be
reached directly, or must be forwarded through a gateway or router.
In the mask, all bits in the source IP address that correspond to its network
portion (both site and subnet identifying bits) are set to 1, and all bits that
correspond to the host portion are set to 0. The destination IP address is logically
ANDed with the mask to determine its network portion. Its network portion is
then compared to the network portion of the source. If the network portions
match, the frame is transmitted directly; if they do not, the frame is routed.
Time to live
The upper bound, in seconds, that a datagram may be processed within the
internet. Each time the datagram passes through the internet layer on any
network device, the IP entity must decrement this field by at least one. If the field
reaches zero at an intermediary device before reaching its intended destination,
the datagram is discarded.
Transmission Control Protocol (TCP)
The Internet suite protocol which transports IP datagrams via a
connection-oriented service. A connection oriented service requires that the
interface layer (that responsible for transmitting datagrams on a single physical
medium, e.g., Ethernet) perform connection management to find an underlying
connection on which to transmit the datagram.
User Datagram Protocol (UDP)
The protocol offering a connectionless-mode transport service in the Internet suite
of protocols. A UDP datagram contains source and destination ports, a length
field, a checksum, and user-data from the upper layer protocol.
Software Conventions
NetSight Element Manager’s device user interface contains a number of elements
which are common to most windows and which operate the same regardless of
the window in which they appear. A brief description of some of the most
common elements appears below.
NOTE
In accordance with Year 2000 compliance requirements, NetSight Element Manager
displays and allows you to set all dates with four-digit year values.