[jiggawatts]

My understanding is that back in the early 2000s the Citrix ICA and Microsoft RDP protocols were nearly identical. Common code and all that.

One of the reasons companies licensed Citrix is because Citrix kept investing in ICA and it was about 2-3 times as bandwidth efficient. In the era of 64 Kbps ISDN WAN links this was critical.

Microsoft did something around 2008 and now RDP seems better overall. It can handle 4K at 30 fps without difficulty.

Meanwhile Citrix did weird random things to ICA that made it markedly worse.

It says a lot that all of the Citrix engineers I’ve worked with (including myself) prefer to RDP into a Citrix server instead of using its native ICA protocol!

Other deliberate breakage was Citrix deprecating SSL support directly on the session hosts. They did this to force customers to buy their overpriced Netscaler / ADC appliances. These slow down connections and can’t handle many 4K streams.

Generally they seem to have become an acquisition-driven company instead of an engineering-led one.

[ROTMetro]

Don't forget that Citrix had a Terminal Server offering before Microsoft incorporated it into Terminal Server. That was the big offer in my mind, not the RDP client, but the ability to connect multiple end users to one Windows NT server back in NT 3.51/4's early days.