Internetwork Design Guide -- SNA Host Configuration for SDLC Networks

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This article outlines router implementation information related to the following topics:

  • Front-end processor (FEP) configuration for SDLC links
  • 3174 SDLC configuration worksheet example

Table: 3x74 SDLC Point-to-Point Connection Support for AGS+, MGS, and CGS DCE Appliques outlines 3x74 SDLC point-to-point connection support for AGS+, MGS, and CGS DCE appliques.


Guide Contents
Internetworking Design Basics
Designing various internetworks
Network Enhancements
IP Routing Concepts
UDP Broadcast Flooding
Large-Scale H.323 Network Design for Service Providers
LAN Switching
Subnetting an IP Address Space
IBM Serial Link Implementation Notes
References and Recommended Reading

Contents

Table: 3x74 SDLC Point-to-Point Connection Support for AGS+, MGS, and CGS DCE Appliques
Controller Type RS-232 DCE RS-232 NRZI/DCE

3274 1st Generation

  • 3274-1C

Supported

Supported

3274 2nd Generation

  • 3274-21C

Not tested

Supported

3274 3rd Generation

  • 3274-31C
  • 3274-51C

Supported


Supported

Not tested


Not tested

3274 4th Generation


3274-41C


3274-61C


Telex 274


Telex 1274

Need to tie DSR and DTR together on CU side, break DSR to router


Same as 3274-41C


Supported


Supported

Not tested


Supported


Not tested


Not tested

DCA/IRMA 3274 emulation for DOS workstations


DEC SNA gateway


RS 6000 multiprotocol adapter

Not tested


Not tested


Not tested

Supported


Supported


Supported

3174 Subsystem CUs

  • 3174-01R
  • 3174-03R
  • 3174-51R

Not tested


Same as 3174-01R


Same as 3174-01R

3174 ties pin 11 low, (-11VDC) which forces the applique into DTE mode (DCE mode is set when pin 11 is set high)


Same as 3174-01R


Same as 3174-01R

3174 Establishment CUs

  • 3174-11R
  • 3174-13R
  • 3174-61R
  • 3174-91R
  • Telex 1174

Not tested


Same as 3174-11R


Same as 3174-11R


Same as 3174-11R


Supported

Supported


Not tested


Not tested


Supported


Not tested

FEP Configuration for SDLC Links

Table: FEP SDLC Configuration Sample GROUP Parameter Listing and Definitions through Table: FEP SDLC Configuration Sample LU Parameter Listing and Definitions present relevant parameter definitions for an FEP configured to operate within a router-based environment. These parameters are configured as part of the system generation process associated with the Network Control Program (NCP) on an IBM host.

Table: FEP SDLC Configuration Sample GROUP Parameter Listing and Definitions
Parameter Sample Value Description and Implementation Notes

LNCTL

SDLC

Line control parameter that specifies link protocol.

REPLYTO

2

T1 timer; this timer specifies the reply timeout value for LINEs in this GROUP.


Table: FEP SDLC Configuration Sample LINE Parameter Listing and Definitions
Parameter Sample Value Description and Implementation Notes

ADDRESS

(001,HALF)

The value 001 is the physical LINE interface address of the FEP. The second parameter specifies whether half- or full-duplex data transfer within the FEP is used. It also effects the DUPLEX parameter: If FULL is specified here, DUPLEX defaults to FULL and attempts to modify this characteristic are ignored.

DUPLEX

HALF

This parameter specifies whether the communication line and modem constitute a half-duplex or full-duplex facility. If HALF is specified, the RTS modem signal is activated only when sending data. If FULL is specified, RTS always remains active. Refer to the ADDRESS parameter in this table.

NRZI

YES

Encoding for this line; options are NRZ or NRZI.

RETRIES

(6,5,3)

Number of retries when REPLYTO expires. Entry options: (m, t, n) where m = number of retries, t = pause in seconds between retry cycles, and n = number of retry cycles to repeat. This example would retry six times-pausing the value of the REPLYTO between each RETRY (two seconds per Table: FEP SDLC Configuration Sample GROUP Parameter Listing and Definitions), pause five seconds, and repeat this sequence three times for a total of 63 seconds. At the end of this period, the session is terminated.

PAUSE

2

The delay time in milliseconds between poll cycles. The cycle extends from the time NCP polls the first entry in the service order table to the moment polling next begins at the same entry. During this pause, any data available to send to the end station is sent. If end stations have data to send when polled and the time to send the data extends beyond the PAUSE parameter, the next poll cycle begins immediately.

Table: FEP SDLC Configuration Sample PU Parameter Listing and Definitions
Parameter Sample Value Description and Implementation Notes

ADDR

C1

SDLC address of secondary end station.

MAXDATA

265

Maximum amount of data in bytes (including headers) that the UP can receive in one data transfer; that is, one entire PIU or a PIU segment.

MAXOUT

7

Maximum number of unacknowledged frames that NCP can have outstanding before requesting a response from the end station.

PASSLIM

7

Maximum number of consecutive PIU or PIU segments that NCP sends at one time to the end station represented by this PU definition.

PUTYPE

2

Specifies PU type; PU type 2 and 2.1 are both specified as PUTYPE=2.

Table: FEP SDLC Configuration Sample LU Parameter Listing and Definitions
Parameter Sample Value Description and Implementation Notes

LOCADDR

2

LU address of devices connected to the end station PU.


3174 SDLC Configuration Worksheet

Table: 3174-91R Screen 1 Configuration Details through Table: 3174-91R Screen 3 Configuration Details present a configuration taken from an SDLC-connected 3174-91R cluster controller. The configuration of this 3174-91R involved three specific configuration screens. Table: 3174-91R Screen 1 Configuration Details through Table: 3174-91R Screen 3 Configuration Details list the configuration line numbers, entries used, and descriptions of the configuration lines for each screen. Where applicable, extended descriptions are included for configuration entries that are relevant to the requirements of the routed internetwork.

Table: 3174-91R Screen 1 Configuration Details
Configuration Line Number Sample Value Parameter Description and Implementation Notes

98

 

Online test password

99

TKNRNG

Description field

100

91R

Model number

101

2

Host attachment type:

  • 2 = SDLC
  • 5 = SNA (channel-attached)
  • 7 = Token Ring network


Note Note: Configuration line items 104, 313, 317, and 340 in Configuration screen 2 (refer to 3174-91R Screen 2 Configuration Details) are of particular interest when configuring 3174 devices for a router-based SDLC environment. These lines specify the required SDLC address and relevant SDLC options for the cluster controller.


Table: 3174-91R Screen 2 Configuration Details
Configuration Line Number Sample Value Parameter Description and Implementation Notes

104

C2

Specifies the cluster controller SDLC address. It is the same address that you configure on the router's serial line interface. It also represents the PU address of the controller. In multipoint environments, multiple SDLC addresses may be specified on a single serial interface.

108

0045448

Serial number of the cluster controller

110

0

MLT storage support

116

0

Individual port assignment

121

01

Keyboard language

123

0

Country extended code page support

125

00000000

Miscellaneous options (A)

126

00000000

Miscellaneous options (B)

127

00

RTM definition

132

0000

Alternate base keyboard selection

136

0000

Standard keyboard layout

137

0000

Modified keyboard layout

138

0

Standard keypad layout

141

A

Magnetic character set

150

0

Token Ring network gateway controller

165

0

Compressed program symbols

166

A

Attribute select keypad

168

0

Additional extension; mode key definition

173

0000

DFT options

175

000000

DFT password

179

000

Local format storage

213

0

Between-bracket printer sharing

215

45448

PU identification

220

0

Alert function

310

0

Connect dataset to line operation

313

0

NRZ = 0; NRZI = 1

317

0

Telecommunications facility:

  • 0 = Nonswitched
  • 1 = Switched (dial-up)

318

0

Full/half speed transmission; 0 = full speed, 1 = half speed. Controls speed of modem; can be used in areas where line conditions are poor

340

0

RTS control options:

  • 0 = Controlled RTS (for LSD/MSD operation)
  • 1 = Permanent RTS (improves performance)
  • 2 = BSC (not valid for SDLC operation)

365

0

X.21 switched-host DTE connection

370

0

Maximum inbound I-frame size:

  • 0 = 265 bytes
  • 1 = 521 bytes (recommended for better performance)
Table: 3174-91R Screen 3 Configuration Details
Configuration Line Number Sample Value Parameter Description and Implementation Notes

500

0

Central Site Change Management (CSCM) unique

501

xxxxxxxx

Network identifier

503

xxxxxxxx

LU name (for CSCM)

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