Error Control
12-7
V.42 Error Control
The Business Modem first tries for a V.42 connection, then an MNP
connection. The following information is based on the Business Modem's
setting of &M4.
This international standard includes a two-stage hand-shaking process:
■
A
Detection
phase that is based on an exchange of predefined
characters.
■
A
Link Access Procedures for Modems (LAPM) Negotiation
phase, during which the devices identify their capabilities concerning
maximum data block size and the number of outstanding data blocks
allowed before an acknowledgment is required.
MNP Error Control
The Microcom Networking Protocol (MNP) is supported by the ITU-T V.42
Recommendation. MNP is based on special protocol frames. If the remote
device doesn't recognize an MNP Link Request, error control isn't
possible. (In HST asymmetrical mode, 3Com devices use a proprietary
scheme similar to MNP.)
Error Control and
Flow Control
Flow control of data from the computer is required under error control for
two reasons:
■
The transmitting device buffers a copy of each frame it transmits to
the remote end until it is acknowledged by the receiving device.
■
If errors are encountered, retransmission activity can cause a steady
stream of data from the computer to overflow the buffer.
Summary of Contents for OfficeConnect 56K Business
Page 14: ...4 ABOUT THIS GUIDE ...
Page 32: ...1 18 CHAPTER 1 CONNECTING TO YOUR ISP ...
Page 42: ...3 6 CHAPTER 3 MODES OF OPERATION ...
Page 64: ...7 4 CHAPTER 7 CONTROLLING EIA 232 SIGNALING ...
Page 72: ...8 8 CHAPTER 8 CONTROLLING DATA RATES ...
Page 80: ...9 8 CHAPTER 9 ACCESSING AND CONFIGURING THE BUSINESS MODEM REMOTELY ...
Page 96: ...11 6 CHAPTER 11 FLOW CONTROL ...
Page 108: ...12 12 CHAPTER 12 HANDSHAKING ERROR CONTROL DATA COMPRESSION AND THROUGHPUT ...
Page 112: ...13 4 CHAPTER 13 DISPLAYING QUERYING AND HELP SCREENS ...
Page 124: ...14 12 CHAPTER 14 TESTING THE CONNECTION ...
Page 132: ...15 8 CHAPTER 15 TROUBLESHOOTING ...
Page 162: ...B 14 APPENDIX B ALPHABETIC COMMAND SUMMARY ...
Page 168: ...C 6 APPENDIX C FLOW CONTROL TEMPLATE ...
Page 210: ...14 GLOSSARY ...