MICA In-Band Framing Mode Control Messages

This feature module describes the MICA In-Band Framing Mode Control Messages feature for Cisco IOS Release 12.1(2)T. It includes information on the benefits of the new feature, supported platforms, related documents, and so forth.

Feature Overview

Dial-in Internet connections typically start in character mode to let the general user log in and select a preferred service. When Cisco IOS determines that the user wants a framed interface protocol during the call, such as PPP (Point-to-Point Protocol) or SLIP (Serial Line Interface Protocol), commands are sent to the MICA modem so that it will provide hardware assistance with the framing. This hardware assistance reduces the Cisco IOS processing load. To avoid loss or misinterpretation of framed data during the transition, these commands must be issued at precise times with respect to the data being sent and received.

This feature allows the MICA modem framing commands to be sent in the data stream itself, which greatly simplifies Cisco IOS tasks in achieving precision timing. This reduces timeouts during PPP startup and reduces startup time. Previous to this feature, the modem interface timing rules were not well understood and were difficult or impossible to implement via the modem's separate command interface. The practical result is that this feature reduces timeouts during PPP startup, and thus reduces startup time.

Benefits

Faster Connection

For PPP connections, the common way for modems to connect to the Internet, total connect time might typically be improved by 2 to 3 seconds.

Improved Productivity

If an ASCII banner is sent just before PPP startup, this feature eliminates problems with banner corruption such as truncation and extraneous characters, thus improving the performance of terminal equipment.

Supported Platforms

Cisco AS5300 universal access server
Cisco AS5800 universal access server

Supported Standards, MIBs, and RFCs

Standards

There are no new or modified standards for this feature.

MIBs

There are no new or modified MIBs for this feature.

For descriptions of supported MIBs and how to use MIBs, see the Cisco MIB web site on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.

RFCs

There are no new or modified RFCs for this feature.

Configuration Tasks

See the following sections for configuration tasks for the MICA In-Band Framing Mode Control Messages feature. Each task in the list indicates if the task is optional or required.

Configuring no flush-at-activation (Required)

Configuring no flush-at-activation

Command Purpose

Step 1

Router# conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#
Enters terminal configuration mode.

Step2

Router(config)#line line-number ending-line-number
Enters line configuration mode and specifies the number of modem lines to configure. Usually this range is equal to the number of modems in the access server.

Step3

Router(config-line)#no flush-at-activation
Router(config-line)#exit
Router(config)#
Normally a router avoids line and modem noise by clearing the initial data received within the first one or two seconds. However, when the autoselect PPP feature is configured, the router flushes characters initially received and then waits for more traffic. This flush causes timeout problems with applications that send only one carriage return. Enter the no flush-at-activation command to improve PPP/SLIP startup.

	Command	Purpose
Step 1	Router# conf t Enter configuration commands, one per line. End with CNTL/Z. Router(config)#	Enters terminal configuration mode.
Step2	Router(config)#line line-number ending-line-number	Enters line configuration mode and specifies the number of modem lines to configure. Usually this range is equal to the number of modems in the access server.
Step3	Router(config-line)#no flush-at-activation Router(config-line)#exit Router(config)#	Normally a router avoids line and modem noise by clearing the initial data received within the first one or two seconds. However, when the autoselect PPP feature is configured, the router flushes characters initially received and then waits for more traffic. This flush causes timeout problems with applications that send only one carriage return. Enter the no flush-at-activation command to improve PPP/SLIP startup.

Command Reference

There are no new or modified commands for this feature.

Glossary

DMM---Dual MICA Module. Contains 12 discrete modems.

DSR---Data Set Ready.

HMM---Hex MICA Module. Contains six discrete modems.

Host---The router chassis (for example, Cisco AS5300) that the carrier card is located in.

IBC---In-band Control. Refers to issuing MICA commands on the data channel, versus OBC, on the out-of-band control channel. In-band commands are passed by setting an in-band-command bit in the data buffer.

OBC---Out-of-band control. Refers to the standard method of issuing MICA commands on the control channel, versus IBC, on the in-band data channel. Out-of-band commands are passed through the MICA mailbox mechanism.

Portware---Software running on a MICA HMM or DMM.

PPP---Point-to-Point Protocol. MICA performs PPP framing (flags, escapes, CRC, ACCM) as a hardware assist to the Cisco IOS. PPP is also the name of the MICA framing mode in which PPP framing takes place.

Raw---MICA interface mode in which no framing takes place. The other interface modes are PPP and SLIP. In raw mode, data is forwarded immediately without interpretation of individual characters. The purpose of the MICA In-Band Framing Mode Control Messages feature is to switch MICA between framing modes with minimal timing problems.

SLIP---Serial Line Interface Protocol. MICA performs SLIP framing (flags, escapes) as a hardware assist to the Cisco IOS. PPP is also the name of the MICA framing mode in which SLIP framing takes place.

PPP and SLIP are ways to encapsulate modem data so that it can be treated as frames or packets. The two framing protocols allow frame boundary information to be passed with the frame data, or payload.

Table of Contents

MICA In-Band Framing Mode Control Messages