Appendix B: Glossary; Arp (Address Resolution Protocol); Clients And Servers - ICP DAS USA PDS-220F Series User Manual

Programmable Serial-to-Fiber Device Server

Appendix B: 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.
PDS-220Fx Series User Manual Version 1.3, Oct. 2018 - 99 -