Talk:Systems Network Architecture

	This article is within the scope of WikiProject Computing, a collaborative effort to improve the coverage of computers, computing, and information technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.ComputingWikipedia:WikiProject ComputingTemplate:WikiProject ComputingComputing
???	This article has not yet received a rating on Wikipedia's content assessment scale.
???	This article has not yet received a rating on the project's importance scale.
	This article is supported by WikiProject Software.

The demise of SNA has always been predicted but will not be till IBM says so. — Preceding unsigned comment added by Askjva (talk • contribs) 04:06, 31 August 2002‎ UTC

From the article:

The first numbers of your credit card is usually a SNA routing sequence.

Really? Can we have a cite for this? — Preceding unsigned comment added by The Anome (talk • contribs) 01:47, 4 September 2002‎

On a SNA based VISANET Take a TranScan a PC-based intelligent protocol monitor and analyzer designed to support Credit Card, Debit Card, Bank Card and Financial Transaction Processors press B to show message routing and usually it is your credit card number

ASKJVA

Possibly for some definition of message routing routing that has nothing to do with SNA, but routing in an SNA network is controlled by identifying the sending and receiving logical units, not with a routing sequence. Routing decisions are made by consulting tables in intermediate nodes. Try a protocol analyzer that breaks out the header fields in the SNA Request/Response (RR) units rather than presenting the financial data. Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:24, 17 October 2011 (UTC)[reply]

2003-sep-13. Starting from version 5.2 of IBM OS400, SNA for client-access is no longer supported — Preceding unsigned comment added by Juky (talk • contribs) 14:48, 13 September 2003‎

SNA in System/3x and {AS/400, iSeries, System i, whatever it's called these days}

This article should mention the use of SNA/SDLC in the IBM minicomputers. The S/34 only supported the 5250 terminal protocol (LU7). The S/36 first implemented APPC, followed by APPN, which was quite robust. It allowed full peer-to-peer networking without additional equipment and simple management. — Preceding unsigned comment added by 190.27.215.37 (talk) 03:33, 24 November 2011 (UTC)[reply]

The article does mention it; in IBM Systems Network Architecture#Logical unit types, it says

SNA defines several kinds of devices, called Logical Unit types:

...

LU7 provides for sessions with IBM 5250 terminals.

The primary ones in use are LU1, LU2, and LU6.2 (an advanced protocol for application to application conversations).

Within SNA there are two types of data stream to connect local display terminals and printers; there is the 3270 data stream mainly used by mainframes (zSeries family) and the 5250 data stream mainly used by minicomputers/servers such as the S/36, S/38, and AS/400 (now System i).

Starting from version 5.2 of OS/400, SNA for client-access is no longer supported.

Perhaps it should say more; if so, go ahead and make it do so. Guy Harris (talk) 08:36, 24 November 2011 (UTC)[reply]

Advantages and Disadvantages

I have added this section to replace the original second paragraph. The original paragraph didn't make any sense to me. The article could use a paragraph on writing applications to use SNA/VTAM (particularly to communicate with other programs). Said paragraph should follow the enumeration of LU types. Rdmoore6 19:29, 18 January 2006 (UTC)[reply]

I'm not a guru, but didn't SNA use one UCB for the attachment of a controller to the host, while Bisync used a UCB per line attached to the 270x? This sounds like an advantage. Peter Flass (talk) 01:43, 6 September 2012 (UTC)[reply]

Channel attached SNA controllers used the same addresses for all SNA traffic. Some of them supported multiple channel attachments for, e.g., performance. The term "UCB" is a software concept that has nothing to do with SNA and is not synonymous with address.

One complication is Partitioned Emulator Program (PEP), in which the same controller ran both NCP and the Emulator Program (EP) (as an 270x replacement); the latter has its own block of I/O addresses, normally on a different channel from those used by the NCP proper. Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:41, 7 September 2012 (UTC)[reply]

Network Control Program

I decided not to make Network Control Program a wiki link. Problem is that existing article describes the ARPANET NCP and says nothing about IBM's use of the same term in SNA.Rdmoore6 19:41, 18 January 2006 (UTC)[reply]

Linked to IBM Network Control Program. Philcha 16:09, 19 October 2007 (UTC)[reply]

Objectives of SNA; Principal components and technologies

I've added these 2 sections. "Objectives of SNA" deals mainly with the commercial aspects, including how "Dark Ages" data communications was before SNA and X.25 - something modern non-specialist readers will not understand if they are not told very plainly.

Can anyone provide refs for them? I was an IBM employee at the time (my last project for IBM was SNA-related) and have summarised internal IBM presentations (omitting a lot of details which would confuse general readers), but have no references I can cite.Philcha 16:01, 19 October 2007 (UTC)[reply]

LU type pertains to session, not to terminal

The LU type pertains to an LU-LU session, not the actual LU. As an expample, it was common for the same printer to be in an LU1 session with one application and an LU3 session with a different application. Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:40, 16 November 2010 (UTC)[reply]

Line sharing prior to SNA

The ability to share a communications line between applications goes all the way back to QTAM. The ability to share a line between TSO and another application is as old as TSO; it started with TCAM. Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:53, 20 November 2010 (UTC)[reply]

S/360 and S/370 I/O

The IBM System/360 and System/370 did not act as controllers for peripherals and were not limited to 16 I/O devices per channel. An I/O channel connected to control units, which in turn connected to peripherals^[1]. In the case of DASD, tape and telecommunications, it was normal for one controller to connect to or include multiple peripherals.

^ In some cases the control unit was integrated with the peripheral.

Shmuel (Seymour J.) Metz Username:Chatul (talk) 23:05, 20 November 2010 (UTC)[reply]

Error checking in SDLC and HDLC

SDLC and HDLC did not use an ECC; they used a simple Cyclic redundancy check (CRC). Shmuel (Seymour J.) Metz Username:Chatul (talk) 23:16, 20 November 2010 (UTC)[reply]

This is better than SLIP, which used nothing. If you have a known, fixed, frame length you can calculate a table of values to reconstruct the original data from the CRC value (of course assuming your CRC transmitted correctly which is pretty silly)... — Preceding unsigned comment added by 203.214.89.130 (talk) 12:05, 28 November 2012 (UTC)[reply]

Modem speeds prior to SNA

Dial-up modems faster than 300 bps were available in 1962, well before SNA. Shmuel (Seymour J.) Metz Username:Chatul (talk) 23:31, 20 November 2010 (UTC)[reply]

There may have been faster leased-line modems in 1962, but the Bell 103 was the fastest dialup modem in 1962, at up to 300 bps, but perhaps most commonly used with Teletype equipment at up to 110 bps. The next improvement in dialup rates was the Bell 202, which offered dialup rates up to 1200bps half-duplex, with a 75 bps reverse channel. I can't find a reference for the date of introduction of the 202, but I don't think it was before 1964. --Brouhaha (talk) 19:38, 2 October 2011 (UTC)[reply]

From Modem:

In the summer of 1960, the name Data-Phone was introduced to replace the earlier term digital subset. The 202 Data-Phone was a half-duplex asynchronous service that was marketed extensively in late 1960. In 1962, the 201A and 201B Data-Phones were introduced. They were synchronous modems using two-bit-per-baud phase-shift keying (PSK). The 201A operated half-duplex at 2,000 bit/s over normal phone lines,

Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:36, 3 October 2011 (UTC)[reply]

Thanks for pointing that out. I believe the years claimed in that article are wrong, and will add citation-needed tags to it. --Brouhaha (talk) 23:48, 6 October 2011 (UTC)[reply]

History of SNA

While IBM initially only supported SNA in VTAM, they later added SNA support to TCAM 10. Also, as part of the Advanced Communications Function (ACF) announcement they added Multi-System Network Facility (MSNF) to ACF/TCAM and ACF/VTAM. MSNF, APPN and MSI each altered the way routing was done in SNA. In particular, MSNF supported connecting two SNA networks with a channel-to-channel adapter (CTCA).

Also, should I add any of the relevant manuals to the article? Some are brief summaries and some are highly technical. Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:55, 17 October 2011 (UTC)[reply]

Dial-up speeds in the 1970s

Dial-up connection speed was limited to 300 bits per second mainly because faster modulation schemes had not yet been implemented. In those days, a transmissions were at one bit per baud. It was better modulation schemes, which allowed multiple bits per symbol, that provided increased speeds on the same dial-up line.

Also, until the 1968 Carterfone decision, any equipment attached to the public switched telephone network had to be approved by the carrier, i.e., AT&T. And AT&T only supplied 300 bps modems. — Preceding unsigned comment added by 71.191.134.57 (talk) 19:05, 3 April 2012 (UTC)[reply]

Status of 3770

To answer the question of whether the 3770 is related to the 2780 and 3780, no, it is not. However, there is no separate article on the 3770 and the 2780 article does discuss it, so the link to that article is appropriate unless and until somebody splits the 3770 off into a separate article. Shmuel (Seymour J.) Metz Username:Chatul (talk) 12:47, 27 June 2012 (UTC)[reply]

Unfortunately there isn't much 3770 info online (yet). Hopefully there'll be more in a while. Peter Flass (talk) 14:02, 27 June 2012 (UTC)[reply]

[1] In some cases the control unit was integrated with the peripheral.

[1]