Shortcomings of 3270 emulation architecture
The 3270 emulation architecture carries over the Internet the native (connected synchronous) communication mode of the mainframe, which is foundamentally incompatible with the
native (disconnected asynchronous) connection mode of the Internet. The result is a dependance on client software, which creates specific compatibility, support, security, session
management and performances considerations.
Client software – As illustrated below, there are two possible types of 3270 emulation architecture: thick-client and client-on-server. Both rely upon
platform-dependant client software that runs either on the clients or on intermediate servers (Citrix, Microsoft, etc).
3270 emulation architecture: client-on-server
3270 emulation architecture: thick-client
Administration server – A server with platform-dependant administration software is required in either case to administer the solution.
Client and administration software upgrades – Both client and administration software must be installed, supported, and upgraded in case of OS change,
e.g. when upgrading from Vista to Windows 7, or from Windows to a different OS.
Grand-public device support – Mobile devices (smartphones, PDAs, and tablets) and Apple products (Mas OS-X) might not be supported.
Host connection – TN3270 connections require opening a special port in the host's firewall, and they remains permanently opened over the Internet –
whether active or not – until users logoff.
Performances and scalability – Client-on-server solutions have the advantage of being thin-client but the intermediate servers can create bottlenecks and
require load balancing and performances tuning.
Advantages of Virtel Pure Web (straight TCP/IP) architecture
Because Virtel uses native (disconnected asynchronous) TCP/IP connections over the Internet straight off the mainframe instead of TN3270 ones, it doesn't need any client
software or intermediate servers, which gives it universal web client support, lower support requirements, higher performances and efficiency.
True thin-client solution – Virtel uses no client software and no middle-tier server.
Virtel pure web (straight TCP/IP and thin-client) access
Universal client support – Virtel works with any browser on any platform or OS (current or future) including platforms that were not in the past used to
access host applications such as Apple products and mobile devices.
Low support requirements – There is nothing to install or support outside the host. All installation, administration, and support tasks are
Host connection – Virtel uses the standard TCP/IP port: no need to open a special port in the host firewall. Virtel use TCP/IP connections between host
and client. Those connections are opened only while active and closed while inactive.
A superior architecture – Virtel provides the benefits of a thin-client solution, and avoids the issues of solutions that rely on intermediate