QMS 2060 User Manual - page 243
Internet
Routing
C-5
TCP/IP Concepts
11111111 11111111 11111111 00000000
specifies that the first three groups of eight digits in the Internet
address identify the network and subnet and that the fourth group
identifies the host on that subnet. However, these numbers are more
commonly written in decimal form. For example, the binary subnet
mask above would be written in decimal form as
255.255.255.0
Internet Routing
Once the Internet address, subnet addresses, and subnet masks are
in place, information can be sent, or routed, to any destination in the
Internet. Both hosts and gateways participate in the routing process.
If information is sent between two devices on a single physical net-
work, or subnet, no gateways are involved. The sending device
encapsulates the datagram in a physical frame, binds the destination
internet address to a physical hardware address, and sends the
resulting frame directly to the destination.
If the information is sent between two devices on two different physi-
cal networks, however, the internet gateways form a cooperative,
interconnected structure. Datagrams pass from gateway to gateway
until they reach a gateway that can deliver them directly to a device
on that physical network.
Class A, B, and C Internet Addresses
TCP/IP defines a means for the network administrator to configure
the network that best suits the network environment at a site. One
method is to define the 32-bit TCP/IP network address in terms of the
number of networks and the number of hosts at the site. The network
address is partitioned into a network part and a host part.
There are 3 common partitions—Class A, Class B, and Class C. The
classification is done by the highest order bits. For example, a 0 in the
highest order bit of the 32-bit address indicates that the address is
Class A. Thus, the next 7 bits constitute the network address, and the