ICA Only:

If you don’t have enough Citrix Gateway Universal licenses installed for all of your Gateway users, then we can use ICA Only option. This option disables SmartAccess and VPN features but does not require any additional licenses. Note: most Citrix ADC Editions come with built-in Gateway Universal Licenses.

If we dont need smartaccess, then we can use ica only option to provide apps and desktops to users.

ICA Proxy:

Citrix Gateway has an ICA Proxy feature that authenticates the user, proxies HTTP traffic to StoreFront, and then proxies ICA traffic to VDAs.

ICA Proxy only exposes a single IP address to the user. All communication from all external Citrix clients to all internal StoreFront servers and all internal VDAs is proxied through the one IP address. The “single IP address” feature is also sometimes useful internally, especially if there’s any Network Address Translation between internal subnets, or if the Citrix VDAs are protected behind an internal firewall.

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