Micro-to-mainframe-link vendors provide higher-speed transmission links for corporate customers who want to take advantage of the fiercely competitive communications market to forge fast and economical links between workstations and hosts.
This new breed of communications products that run as fast as 56K bits per second (bps) will pump data at five times the speed of the now-common 9.6K-bps modem connections in many micro-to-mainframe systems, specifically IBM mainframes.
In the race for fast, efficient links, communications suppliers have turned to high-speed high-performance 3274 emulators and local area network gateways to link PCs to mainframes.
For users, these products mean increased response time and faster file transfers between PCs and the mainframe. For data-communications managers, these products make it possible to support a greater number of busy workstations on the same LAN or to run bulky applications at remote sites, such as using a PC connected to a mainframe to drive a 2,000 line-per-minute (lpm) printer or to run mainframe graphics applications.
“Many companies need to send 6M bytes or 7M bytes of data from their PCs to mainframes on a frequent basis,” said Steve Chiu, president of Network Software Associates (NSA) in Laguna Hills, Calif. Mr. Chiu said a 56K-bps controller emulator could reduce the time to send a 7M-byte file from 25 minutes at standard 9.6K bps to five minutes using 56K-bps transmission lines.
LAN gateways and stand-alone emulators connect PCs to mainframes, either locally through coaxial cable connected to a mainframe, or remotely over telephone lines. Coax and IBM controllers can support speeds of up to 1M bps.
Since many sites are too far from the processor to connect locally, many of the gateways and stand-alone adapters are used in remote sites over telephone lines, according to users and vendors. Connected to the controllers through telephone lines, these PC emulators transmit at speeds of 4.8K bps and 9.6K bps–far slower than the capabilities of the controller.
High-speed emulators, with 56K-bps lines, can speed up applications bogged down by slower communications links. A mainframe systems programmer in a West Coast firm is testing a 56K-bps adapter for a stand-alone PC. For this remote-printing test, a PC is connected to laser and line printers. He needs to drive a 6,000-lpm printer at a remote site through a PC, and is finding a high-speed Barr/Hasp gateway from Barr Systems Inc. in Gainesville, Fla., helps the PC keep up.
Even though high-speed products are selling well, according to vendors, many customers are not running them at 56K bps because of the cost of communications lines, according to Maks Wulkan, executive vice president at Eicon Technology Corp. in Montreal.
Nonetheless, “The key is not to upgrade but to provide customers with peace of mind, knowing that they can always move up to higher speeds,” Mr. Wulkan explained.
“Faster is never worse,” stated Michael Krieger, manager of product development for data-communications products at AST Research in Irvine, Calif. AST does not market a 56K-bps gateway to end users. According to Mr. Krieger, customers are always open to decreasing the amount of time needed to transfer files or update a screen of graphics.
Give Them an Inch . . .
“Speed is addictive. You give somebody something, and six months later they need something better,” said Paul Rarey, senior analyst and network designer at Northrop Corp. in Hawthorne, Calif.
Future artificial-intelligence applications requiring larger amounts of data transfer can benefit from faster communications, said Tom Egan, a systems-support manager for the Wells Fargo Bank in San Francisco.
Not every application benefits from high speeds. Mr. Rarey, however, is satisfied with the NSA Adapt/RJE (Remote-Job Entry) application running at 9.6K bps, and Mr. Egan said the bank is happy with the 9.6K-bps communications through Wells Fargo’s gateways.
Higher transmission speeds may also improve response time from future applications using IBM’s Advanced Program-to-Program Communications (APPC) protocol. Such applications will let PCs connect directly with other processors, sometimes bypassing controllers. “APPC applications will require faster links to move larger amounts of data back and forth,” said Mr. Krieger of AST.
One of the main factors inhibiting broader acceptance of the high-speed products is the cost of 56K-bps communications lines, according to David Taylor of Integrated Network Services Inc. (INS) in Mobile, Ala. Like AST, INS finds its customers are satisfied with 19.2K-bps capabilities.
“A 56K-bps switched service is pretty expensive right now,” said Larry Stephenson, executive vice president and cofounder of Gateway Communications Inc. of Portland, Or.
According to a spokesman for AT&T, 9.6K-bps analog leased lines cost $1,300 running across the country between, for example, Denver and New York–1,627 miles. The same run costs $5,300 per month for a 56K-bps link.
High-speed gateways are taking hold in companies where 56K-bps service is already in place. At John Deere, 30 programmers use a CXI PCox gateway at the company’s programming facility in Waterloo, Ill., and corporate headquarters in Moline, Ill. The 56K-bps bandwidth is not an issue for John Deere, according to technical support manager Milford Grey, since the farm-implements company already has two 1.44M-bps, T-1 links. The remote facility just multiplexes on one of the T-1 circuits, Mr. Grey said.
As an alternative to leased 56K-bps lines in environments where links are not used continuously, telephone companies offer dial-up 56K-bps service.
Such services are billed by the minute with a basic monthly charge. Pacific Telephone provides such a service, called public switched-data service (PSDS).
Depending on the location, dial-up service runs between $50 and $300 for the basic service plus $.06 per minute.
Dianna Thomas, product manager for PSDS at Pacific Telephone in San Francisco, said the service is targeted at companies using the 56K-bps link approximately one hour each day. Pacific Telephone is a Bell Operating Company (BOC) serving California.
Pricing for 56K-bps service may vary as competition among AT&T, the BOCs and third-party carriers results in price cuts.
Transmitting and receiving at 56K bps and higher speeds requires more sophisticated processing. The new high-speed boards include on-board coprocessors, such as the Intel 80186, dedicated to handling the protocol conversion from the PC to the synchronous link and reducing the workload from the PC’s processor.
Support’s No Easy Task
“It takes a lot of work for the PC to support terminal emulation,” said Len Palmer, vice president of marketing with CXI Inc., of Virginia. “But, by putting a processor in the gateway, you can do some simultaneous processing.”
Besides increasing the communications speeds, other performance enhancements enable communications managers to more efficiently use their telecommunications resources by sharing access to the host among several users.
The 3274 cluster controller can only support 32 ports–and adding 3274 controllers is relatively expensive, according to users.
An alternative is to build a gateway on the LAN that would emulate the 3274 controller. Depending on the LAN operating system, a single gateway could support up to 260 users–all communicating over a single link. CXI produces a line of PCox cards that emulate two 3274 controllers supporting up to 64 sessions over a single link.
It is in the X.25 arena that vendors expect to see the real payoff for 56K-bps products. Although an SDLC link can handle multiple sessions, the sessions can only occur between the mainframe and PC or gateway. A link with an X.25 network, however, will allow a single gateway connected to a public or private X.25 network, to connect with multiple processors over the same link.
Such configurations are common in Europe, where private or leased lines are more expensive. Eicon makes a board called the Access/X.25 for connecting a gateway to a packet-switching network, which the company sells in both Europe and the United States.
PCs can be attached to IBM mainframes using X.25 synchronous protocol, with software called Network Packet Switching Interface (NPSI) running on the 3725. Similar to point-to-point data-link services, vendors expect X.25 56K-bps packet-switching networks options to drop as well.
Gateways with speeds of 56K bps and higher are becoming more and more prevalent. With this trend, 3174 emulators will provide links to decrease response time and increase the number of users on a LAN. But this will only happen as costs for phone lines drop to the point where companies can justify increased communications costs.
Photo: Eicon’s network adapter card used with its LAN gateway products provides 64K-bps speeds.