2680A/2686A
Users Manual
H-8
During initial operation of the TCP/IP software the IP section builds a table that
contains the correspondence between the IP address and Ethernet address of each
host. This is done via the Address Resolution Protocol (ARP). To do this, the IP
software sends out a broadcast frame that every TCP/IP host and router receives.
This frame contains a request for the host with the unknown IP address to return a
frame to the ARP requester. This response frame contains the Ethernet address of
the sourcing host, and this information is then added to the address correspondence
table. All communication with a host can then be done with information from the
table.
The operation of ARP also initializes the routing tables in bridges, routers, and
gateway devices on the net. These tables are used to determine the section of the
network to which a frame should be sent.
Ethernet Adapter Hardware for the PC
To communicate via the Ethernet network, each PC must be equipped with an
Ethernet adapter. There are several types of adapters available (e. g. internal
interface boards (ISA or PCI), PCMCIA interface cards, and USB adapters). Some
PCs are equipped with an Ethernet adapter by the manufacturer, but often adapters
must be added after purchase.
Installation of an Ethernet adapter is quite simple. Windows NT, and later versions
of Windows can install commonly used adapters without using the adapter’s
installation software.
During the installation of an internal interface board on an ISA bus computer, you
may need to make several detailed configuration decisions. An interrupt line (IRQ)
is assigned, port addresses selected, and the network connection type selected. Be
sure to record these configuration values because you might need them when
installing the network interface software. Installation of a PCI interface board is
similar, but is usually more automatic.
During installation of a PC Card or USB interface, few, if any decisions need to be
made. These devices make use of already established interfaces to the computer
bus.
Drivers
A driver is the low-level software within the PC that communicates directly with
the interface adapter hardware. Drivers cover up the specific nature of the
hardware interface and allow the protocol software to be unaware of the type of
hardware being used.
Drivers are usually written and supplied by the adapter vendor. Windows 95,
Windows NT, and later versions of Windows supply drivers for commonly used
adapters. Windows built-in networking typically uses NDIS or ODI drivers. Some
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