Appendix C: Glossary; Arp (Address Resolution Protocol); Clients And Servers; Ethernet - ICP DAS USA PDS-5000 Series User Manual

Programmable Serial-to-Ethernet Device Server

Appendix C: Glossary

1. ARP (Address Resolution Protocol)

The Address Resolution Protocol (ARP) is a telecommunication protocol that is used to convert an
IP address to a physical address, such as an Ethernet address.
Consider two machines A and B that share the same physical network. Each has an assigned IP
address IP and IP , and a MAC address, MAC and MAC . The goal is to devise a low-level software
A B A B
application that hides the MAC addresses and allows higher-level programs to work only with the IP
addresses. Ultimately, however, communication must be carried out by the physical networks using
whatever MAC address scheme the hardware supplies.
Suppose machine A wants to send a packet to machine B across a physical network to which they
are both attached, but A only has the Internet address for B, IP . The question arises: how does A
B
map that address to the MAC address for B, MAC ?
B
ARP provides a method of dynamically mapping 32-bit IP address to the corresponding 48-bit MAC
address. The term dynamic is used since the mapping is performed automatically and is normally
not a concern for either the application user or the system administrator.

2. Clients and Servers

The client-server paradigm uses the direction of initiation to categorize whether a program is a
client or server. In general, an application that initiates peer-to-peer communication is called a
client. End users usually invoke client programs when they use network services.
By comparison, a server is any program that waits for incoming requests from a client program. The
server receives a request from a client, performs the necessary actions and returns the result to the
client.

3. Ethernet

The term Ethernet generally refers to a standard published in 1982 by Digital Equipment Corp., Intel
Corp. and Xerox Corp. Ethernet is the most popular physical layer Local Area Network (LAN)
technology in use today.
PDS Series User Manual, Version 2.5, Mar. 2019 - 214 -