* Remember the usefulness of Modified Data Tag technology?
A lot of attention is paid in the industry to network and application optimization techniques such as compression, caching and protocol optimization. This attention is justified as these are all important techniques that can be used to improve application performance. However, in a recent newsletter we wrote about a related topic that is not discussed as often – WAN-vicious applications.
In that newsletter, we discussed a WAN-vicious application that we came across when doing some consulting work. That application sends a 2MB file to remote users just so that the software on the client can extract a 10-digit code. What we did not mention in that newsletter is that while it is possible to apply techniques such as compression to the file, these techniques will have notably less of an impact on application performance than if the application was written to just send the 10-digit code.
We received a lot of feedback about that newsletter. One reader put today’s applications in an historical context. He stated that the infamous IBM “Green Screens” pioneered the Modified Data Tag (MDT) technology. When a screen full of data was presented for updates, only the fields containing changes were transmitted back to the host. A very efficient block mode technology replaced the highly network-inefficient character mode echo-based technology.
He also said that in the mid-90s, HP adopted MDT techniques and carried screen transmission reduction to a new level. HP’s screen handling package, View 3000, allowed forms to be cached in a slightly higher-end terminal and later in PCs. HP also implemented block mode transmission.
The reader’s final comment was that many legacy minicomputer (HP, DEC) applications were written using old-fashioned character mode, telnet or other highly inefficient Unix-based protocols. While these applications performed wonderfully in a hardwired terminal environment, they bombed in a WAN (i.e., X.25, frame relay) environment. He concluded his note to us by asking the question “How many of these applications are still around?”
In our next newsletter, we will provide additional reader insight into the challenges of running certain applications over a WAN and will suggest a way for IT organizations to reduce the severity of this problem.
