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Published Application Delivery

Delivering an application to a desk without putting it on the desk — eighteen years and five platform generations, and the mechanism that kept dead software alive on a supported endpoint.

Also known as Citrix, XenApp, MetaFrame, Presentation Server, Terminal Services, Session Delivery, VDI, Virtual Desktop, Thin Client

Left to right is time. Each row is one of the 6 disciplines this one worked alongside, ordered so kindred disciplines sit next to each other rather than alphabetically — a landscape only means anything if neighboring rows belong together. Height is the work running in that domain in that year, weighted by what failure would have cost — life-safety ×3, a statutory obligation ×2.2, the estate itself ×1.5, an evaluation ×1. Every project declares which of those it was, so each ridge traces to an entry you can open and disagree with. Only the work that used this technology is counted, so what shows here is the company it kept rather than the record around it. Height and color are on the record-wide scale rather than this page’s own, so a modest estate draws a modest landscape and any two of these pages can be read against each other.

A published application is a way of not installing something. The program runs in the data center and only the screen travels, which solves a problem that has nothing to do with convenience: what to do when software an organization depends on will not run on the operating system its endpoints are now on.

The part that is architecture

The servers are the visible half and the less interesting one. What has to be designed is the path: the external access route, address translation, firewall policy, load balancing and proxy steering, and the gateway that terminates a session from outside the estate before anything reaches the farm.

That path was rebuilt more than once across the eighteen-year municipal estate — Citrix Secure Gateway with Web Interface early on, later NetScaler Gateway fronting load-balanced StoreFront in the demilitarized zone. Each generation is a different answer to the same question: where does an untrusted session get inspected, and what does it reach afterwards.

Why it is really used

The honest reason a farm like this survives five platform generations is rarely the one in the brochure. Seven Windows Server 2008 R2 hosts carried Access 97, Access 2003, .NET 1.1 and Visual Basic 6 into 2019 — software long past any support, running on a supported desktop only because it was never actually on the desktop.

That is a deliberate position rather than drift. Publishing an application is how an organization decouples the life of a program from the life of the machines it is used on, and it buys years in which the program can be replaced on a schedule rather than on the vendor’s.

The adjacent product it is not

Virtual desktop looks like the same idea taken further, and the municipal estate evaluated it for a decade and declined it. The distinction that mattered: publishing an application moves one program into the data center, where virtual desktop moves the whole machine — and with it the compute, the storage tier, the brokering layer and the network dependency that a local disk does not have.

Applied in

  • Citrix Published Application Estate2005–2023Eighteen years, five platform generations and roughly 4,000 billed seats — with a per-seat price an agency could argue with.
  • The Virtual Desktop Position2011–2023A decade of evaluation whose deliverable was a refusal — two platforms piloted and closed by change order, and an objection that held for eight years.
  • The SHA-2 Migration That Reached Dispatch2014A routine certificate renewal that broke a live estate through its oldest endpoints, stopped station alerting in seventy-plus fire stations, and was resolved by deliberately keeping one service weak.

See also

Also searched as

  • VDI
  • DaaS
  • virtual desktop
  • published applications
  • remote desktop