pter. Remember the problems with the dial-up telephone network and the risk of sending three-quarters of a file transfer only to have a glitch in the transfer? Using the packetized effort, if a glitch occurs, the network might have from 7 to 128 outstanding packets traversing the links. Therefore, instead of scrapping the entire file, the net- work automatically recovers and resends the packets that were lost or cor- rupted. This means that the users would save time and money on an error-prone network. Again, the risk of congestion and delay on the network might cause others to look for alternative solutions. Other Benefits Beyond these benefits, other benefits can be achieved from the use of the dedicated link into the network. As Figure 7-7 shows, the link is not solely for one user at a time, nor is it for two specific locations. When the organi- zation uses a packet-switching network, the users might need to have mul- tiple simultaneous connections up and running. Therefore, the PAD acts similarly to a statistical time division multiplexer (statmux). The statmux capability provides multiple connections into the single device, and samples each of the ports in a sequential mode to determine whether the port has anything to send. If a packet has been prepared, the statmux generates the call request (initiate a call) to the network. The connection is created and the data flows. This assumes that no problems are being experienced on the network. As a new user logs on and generates a request to send data, the PAD then sets up this connection. Packets are interleaved across the physical Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. X.25, Internets, Intranets, and Extranets Chapter 7 User C Figure 7-7 Additional users can share the link. Modem 00000000 User A User B Modem Modem 00000000 00000000 link between or among the various users. One can