Yes, it is true. The ICA protocol is actually optimized for low bandwidth.
One can actually work quite comfortably over a 28.8k+ connection. Scrolling
is quite good and it can keep up with typing most of the time.
It also has the benefit of automatic local drive mapping, com and lpt port
mapping, printers and sound. Though thin, the client install actually comes
on 2 diskettes so it's not quite as thin as VNC. Connections to the server
can be established over TCP/IP, IPX as well as others and even direct
dial-up. Like VNC, Citrix also has ICA clients available for many
platforms. The minimum hardware requirement is actually a 286 with 640k of
memory running DOS with a mouse and a VGA monitor. Such a machine, equipped
with a network connection or a modem can actually do pretty much anything
that the fastest and biggest machines can do. The resolution of the screen
session is actually determined at the client end and users can concurrently
be using the same server at different resolutions. Certainly an alternative
to consider when you are thinking of upgrading all of the machines in your
organization.
Similarly to VNC running on Unix, there is only one server (although you
can cluster them and do automatic load balancing). People who connect get
their very own virtual NT/Win2k machine, sharing hardware resources. Larger
Citrix servers can support over 80 concurrent connections depending on what
applications everyone is running. The more demanding the applications, the
less people you will be able to support concurrently before you start to
see the performance degrade. Application installation and maintenance is a
snap as long as you know what you are doing. Essentially you perform a
single install, configure the application once and the next thing you know
everybody can use it. Of course you can still restrict access using Windows
NT security and authentication can be controlled locally or though an
external system such as NT domain or Netware. Did I mention they now also
have a Unix version of MetaFrame available?
Even the ICA clients software can be updated remotely. If you update the
server, ICA clients will automatically be upgraded. Unlike VNC, you can
choose the level of encryption used for an ICA session including basic
encryption (kind of like scrambled with an encryption key applied), 40, 56
and 128 bit encryption. You can even choose to encrypt just the login part
of the session or the whole session. You can configure the server to use
any TCP/IP port you want and it works well though most firewalls.
By the way, you can save yourself a little money if you are willing to give
up some of the frills described above and just want to remotely access a
session on the server by dropping the Citrix part of the equation and just
going with the base Microsoft Terminal Server and the RDP Client. But back
to Citrix and MetaFrame.
A lot of off the shelf software will run just fine although some won't. The
only way to find out is to try it or ask the vendor if it is MetaFrame or
Terminal Server compatible. Most well written applications don't have a
problem.
Finally, if you work in a multilingual organization, both the client and
the server software is available in multiple languages.
Now for the down side.
This is not to say that it is without it's share of quirks and issues.
Certainly it can be challenging just like everything else in the IT world.
The biggest issue of course is price. The software doesn't go cheap,
especially once you've muddled your way though Terminal Server Licences,
CALs (Client Access Licenses) and of course the Citrix server software and
client licenses (at least the Citrix software is based on concurrent access
licenses unlike the Micro$oft stuff. Add that to the cost of a decent
server with oodles of memory and gobs of hard disk space and we are talking
pretty big bucks (but that's really a relative issue, isn't it? You should
do a cost benefit for your organization). By the way, if your application
runs on NT 3.51, Citrix still sells its WinFrame server which is a real
bargain since you don't have to deal with Microsoft licensing and you still
get most of the benefits above. Just straight concurrent usage licensing.
Life used to be so simple...
The Citrix ICA protocol isn't something you can just drop on any machine.
It only works as an add-on to Terminal Server. You can't use it to take
over just any old PC running Unix or Windows.
The ICA protocol is also optimized for use with typical applications. It
really slows down when you start displaying images, especially pictures.
There is also the danger of one user crashing the server since NT doesn't
support limiting memory per session. I know, neither does a VNC session
except that when you crash a PC running VNC, you crash one PC for one user.
When someone crashes a MetaFrame server, it goes down for all of it's
users. That's when you start wishing you had implemented that server farms
(clustering/load balancing). One way to reduce the chances of this
happening is to limit what users are able to run and not to allow them to
run anything unauthorized.
As far as I am concerned, VNC and ICA have only one thing in common. They
are both classified as thin clients. VNC to take over the screen of a
single machine (or virtual screen in the case of Unix) and ICA to take over
the screen of a virtual machine.
Sorry for making this such a long message. I guess I had a lot to say.
Michael Milette
At 11:10 PM 2001-04-20 +0200, you wrote:
>Hello...
>
>VNC is fast but I heart the Citrix ICA protocol is faster!?
>
>Is this true?
>
>--
>Severin Olloz
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