Telecommunications - Communications Controllers

used as a FEP for mainframe or as a remote switch.

1.1 - Hardware

3704 Smaller version of 3705 - obsolete but still in use.
3705 Small IBM computer customised for use as a communications controller supporting physical management of the network. Also usable as a remote communications controller or network node in multi-system environments. Control software is NCP for SNA networks and EP for pre SNA networks.
3725 Enhanced and more powerful version of the 3705 communications processor. release 4 (1986) main storage up to 3 megabytes supports kilostream X.21
3720 model 001 - (introduced 1986) small modular, low end version of 3725
002
011
012
3721 model 1 - (introduced86) - expansion unit
2
3728 communications control matrix switch

1.2 - Software

NCP - Network Control Program

SNA program resident in the 37x5 communications processor.

NTO - Network Terminal Option

Protocol convertor for non-SNA data-streams, supports

teletype,3750/1750 PABXs, allows BSC device to run off a NCP

NPSI - NCP Packet Switching Interface

allows connection to X.25 (QLLC)

PCNE - Protocol Convertor for Non-SNA equipment.

EP - emulation program - allows pre-SNA devices

PEP - partitioned emulation program - allows mixture of devices

2780/3780 IBM batch or RJE terminals, now outmoded as hardware

products but whose protocols continue to survive.

Modems

5865 9.6 kbs has CNM=communications Network Management Functions

5866 14.4 kbs

5868 has 2-wire or 4-wire switched network feature


Interfacing to an X.25 network - NPSI

NCP Packet Switching Interface (NPSI) allows SNA to be connected across a packet switching network. This software runs with NCP in the front end processor and is a heavy user of the processor.

NPSI was written under special contract to a French customer and initially the software had the reputation of being unreliable and badly supported.

Release 2 onward of NPSI has packet assembler/disassembler (PAD) support.

Users can also write their own transport service gateways using genralised access to X.25 transport extension (GATE). This is a module in NSI and communicates with a special application, known as a communication and transmission control program (CTCP) which runs on the mainframe using standard facilities provided by VTAM

Writing transport service gateways

Mainframe FEP

.................. .................

. . . .

. MVS . . NCP .

. | . channel . | . x.25

. VTAM .________________. NPSI .___________________

. . . .

. CTCP ..................... GATE .

.<-sna-> (LU) . . .

. . . .

.................. .................


NPSI integrated PAD

In this mode NPSI handles all X.25 messages incoming X.25 resets and X.29 parameter indications are treated as errors and the call is cleared.

Mainframe FEP

.................. .................

. . . .

. MVS . . NCP .

. | . channel . | . x.25

. TSO VTAM .________________. NPSI .___________________

. . . .

. . . PAD .

. .<--- SNA ------>. (LU) .<---- X.29 ------>

. . . .

.................. .................


NPSI transparent PAD

Mainframe FEP

.................. .................

. . . .

. MVS . . NCP .

. | . channel . | . x.25

. __|_ .________________. NPSI .___________________

. | | . ^ . . remote

. TSO VTAM . | . PAD . start-stop

. . | . .<----- x.29 ------>

. . | . . terminal

.................. | .................

TSO/VTAM defines uses the first byte of

terminal type the buffer to indicate

as user-defined whether it contains

data,qualified data or

X.25 interrupt or reset

Remote 3270 support

Mainframe FEP 3274

.................. ................. ..............

. . . . . .

. MVS . . NCP . . .

. | . channel . | . x.25 . .

. __|_ .________________. NPSI .______. .

. | | . . . . .

. TSO VTAM . . PAD . . .

. . . . ..............

. . . .<-- QLLC --->

.................. .................

<-------------- SNA ------------------------------->

These methods all require the purchase of NPSI, the overheads of running it in the FEP and mainframe, the effort of re-configuring and the extra operator involvement in re-establishing X.25 calls should they fail.

For this reason most users currently find it easier + cheaper to use a separate SNA or BSC PAD if X.25 is used.

mainframe FEP PAD PAD TERMINAL

........ ...... ....... ....... .........

. . . . . . . . . .

. MVS . . . . . X.25 . . . .

. VTAM .___.NCP .___. .______________________. .___. .

. . . . . . . . . .

........ ...... ....... ....... .........

<-chan-><-SDLC-> <-SDLC->

<-------------------------- SNA ---------------------------->


2 - 2780/3780 RJE - remote job entry devices

IBM batch or RJE terminals, now outmoded as hardware products but whose protocols continue to survive.


3 - 3270 Terminal Control Units

3270 is a generic name for a range of IBM terminal control units and terminals. Here is some general information on the IBM products. Many other manufacturers make 3270-compatible devices.

3271 Original 3270 remote cluster controller using BSC line protocol
3272 Original 3270 local (channel attached) cluster controller. Responds directly to channel commands, and interrupts the channel for attention.
3274 Range of cluster controller replacing the 3271 and 3272, and capable of emulating both. Available with various amounts of storage, local and remote attachment options. Functions as an SNA PU2, and will also support non-SNA operation. The 3274 has powerful processing capabilities, and will probably take on increased functionality as functionality is distributed from the mainframe into the network.
3274-1A An SNA local control unit in the 3270 family.
3274-1B A non-SNA local control unit in the 3270 family.
3274-1D A non-SNA local control unit in the 3270 family.
3274-51C A 12-port, mini version of the 1C
3274-61C A 16-port varient of the 51C
3275 Remote BSC screen/printer controller with dial-up facilities. Used as specialist device for remote operation of 4300 processors.
3276 A range of remote BSC/SDLC control units in the 3270 family, each built into a VDU and capable of supporting up to seven more VDUs or printers.
3174 The long awaited 3274 replacement arrived in 1986. It supports LU6.2 and LAN etc.

Configuration Support levels


5 configuration support options are currently availible:

A -

C - Extended data stream

D - Distributed Function Terminal (DFT) - allows 4 concurrent host sessions

P - Packet - X.25 support

T - Temporary - to enable customers with 128K control units to try out

the 3290 terminal

3.1 - Multiplexor

3299 Allows up to eight 3270 family devices to share one co-axial cable to

their controller.

configuring 3274

001

1234567890ABCDEF 34

011 <enter>

021 (enter>

031 <enter>

151 <enter> 61c

331 1 sdlc

parameters all entered flashing

disc running v

lights ............................ 1101 <---- insert language

1101 <---- insert system

1111


3.2 - 3270 Terminals

3270 PC - Version of the PC which provides workstation facilities. Can run four 3270 type sessions, two local notepad sessions, and one PC DOS session. The 3270 PC can be a terminal off a control unit but does not directly emulate a control unit.
3270 PC AT - More powerful version of the 3270 PC.
3277 Screen (head) for a 3271/3272 controller
3278 The monochrome screen (head) for the 3274/3276 controller
3279 Colour screen. Effectively a colour version of the 3278 (replaced by 3179 in 1986)
3178 A display unit in the 3270 family
3179 Colour graphics terminal
3290 Plasma information panel. Large screen (62 x 160 characters), supports multiple applications, graphics etc.

3.3 - Printers

3262 Small line printer

3268 Small serial printer. Available in monochrome and colour versions.

328x Printers for the 3270 family

Plug Compatables

STC ITT 3820 - Maidstone Road,Sidcup Kent DA14 5HT 01-300 7788

Datatrade 38 Billing Road, Northampton NN1 5DQ 0604 22289

Telex 33 Clarence Street, Stanes, Middlesex TW18 4SY

0784 63891





BT interface to netstream LAN

N74 - interface Netstream <-> 3274 coax

N78 - interface Netstream <-> Terminal/printer

Room 607 Lutyens House 588 3341


4 - Protocol Convertors

An SNA network is based on SDLC which is a synchronous protocol. BI-Sync devices can be directly connected to a 3705/3725 which does the protocol convertion to a 3705/3725 which does the protocol convertion. Other devices such as asynchronous (start/stop) terminals need protocol convertors to connect to an SNA network.

5973 NIA Network Interface Adaptor
3710 Network controller for concentrating PU2 nodes onto a 3705/3725 with some protocol conversion (up to 31 lines). converts SDLC or X.25 to multiple BSC,ASYNC or SDLC lines. Very powerful hardware which may well replace the 3705/3725 boxes inthe long term, as well as giving birth to a family of products for communications network management.

IBM offers two protocol convertors to enable stand-alone, start/stop

(asynchronous) terminals to emulate 3270 terminals. They are:

7426 Terminal Interface Unit (TIU)

an eight-port protocol convertor that emulates a 3276 Model 12 SNA

control unit. Two models are available:

Model 1 which attaches to 8100,4321 and 4331 loops

Model 2 which attaches to an ACF/NCP or 8100 SNA/SDLC link.

7171 ASCII device attachment control unit. This unit was announced in the USA on 10 Sep 1984.


 


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